Tag Archives: aerospace/space-flight

No Antenna Could Survive Europa’s Brutal, Radioactive Environment—Until Now

Post Syndicated from Nancer E. Chahat original https://spectrum.ieee.org/aerospace/space-flight/no-antenna-could-survive-europas-brutal-radioactive-environment-until-now

Europa, one of Jupiter’s Galilean moons, has twice as much liquid water as Earth’s oceans, if not more. An ocean estimated to be anywhere from 40 to 100 miles (60 to 150 kilometers) deep spans the entire moon, locked beneath an icy surface over a dozen kilometers thick. The only direct evidence for this ocean is the plumes of water that occasionally erupt through cracks in the ice, jetting as high as 200 km above the surface.

The endless, sunless, roiling ocean of Europa might sound astoundingly bleak. Yet it’s one of the most promising candidates for finding extraterrestrial life. Designing a robotic lander that can survive such harsh conditions will require rethinking all of its systems to some extent, including arguably its most important: communications. After all, even if the rest of the lander works flawlessly, if the radio or antenna breaks, the lander is lost forever.

Ultimately, when NASA’s Jet Propulsion Laboratory (JPL), where I am a senior antenna engineer, began to seriously consider a Europa lander mission, we realized that the antenna was the limiting factor. The antenna needs to maintain a direct-to-Earth link across more than 550 million miles (900 million km) when Earth and Jupiter are at their point of greatest separation. The antenna must be radiation-hardened enough to survive an onslaught of ionizing particles from Jupiter, and it cannot be so heavy or so large that it would imperil the lander during takeoff and landing. One colleague, when we laid out the challenge in front of us, called it impossible. We built such an antenna anyway—and although it was designed for Europa, it is a revolutionary enough design that we’re already successfully implementing it in future missions for other destinations in the solar system.

Currently, the only planned mission to Europa is the Clipper orbiter, a NASA mission that will study the moon’s chemistry and geology and will likely launch in 2024. Clipper will also conduct reconnaissance for a potential later mission to put a lander on Europa. At this time, any such lander is conceptual. NASA has still funded a Europa lander concept, however, because there are crucial new technologies that we need to develop for any successful mission on the icy world. Europa is unlike anywhere else we’ve attempted to land before.

For context, so far the only lander to explore the outer solar system is the European Space Agency’s Huygens lander. It successfully descended to Saturn’s moon Titan in 2005 after being carried by the Cassini orbiter. Much of our frame of reference for designing landers—and their antennas—comes from Mars landers.

Traditionally, landers (and rovers) designed for Mars missions rely on relay orbiters with high data rates to get scientific data back to Earth in a timely manner. These orbiters, such as the Mars Reconnaissance Orbiter and Mars Odyssey, have large, parabolic antennas that use large amounts of power, on the order of 100 megawatts, to communicate with Earth. While the Perseverance and Curiosity rovers also have direct-to-Earth antennas, they are small, use less power (about 25 W), and are not very efficient. These antennas are mostly used for transmitting the rover’s status and other low-data updates. These existing direct-to-Earth antennas simply aren’t up to the task of communicating all the way from Europa.

Additionally, Europa, unlike Mars, has virtually no atmosphere, so landers can’t use parachutes or air resistance to slow down. Instead, the lander will depend entirely on rockets to brake and land safely. This necessity limits how big it can be—too heavy and it will require far too much fuel to both launch and land. A modestly sized 400-kilogram lander, for example, requires a rocket and fuel that combined weigh between 10 to 15 tonnes. The lander then needs to survive six or seven years of deep space travel before finally landing and operating within the intense radiation produced by Jupiter’s powerful magnetic field.

We also can’t assume a Europa lander would have an orbiter overhead to relay signals, because adding an orbiter could very easily make the mission too expensive. Even if Clipper is miraculously still functional by the time a lander arrives, we won’t assume that will be the case, as the lander would arrive well after Clipper’s official end-of-mission date.

I’ve mentioned previously that the antenna will need to transmit signals up to 900 million km. As a general rule, less efficient antennas need a larger surface area to transmit farther. But as the lander won’t have an orbiter overhead with a large relay antenna, and it won’t be big enough itself for a large antenna, it needs a small antenna with a transmission efficiency of 80 percent or higher—much more efficient than most space-bound antennas.

So, to reiterate the challenge: The antenna cannot be large, because then the lander will be too heavy. It cannot be inefficient for the same reason, because requiring more power would necessitate bulky power systems instead. And it needs to survive exposure to a brutal amount of radiation from Jupiter. This last point requires that the antenna must be mostly, if not entirely, made out of metal, because metals are more resistant to ionizing radiation.

The antenna we ultimately developed depends on a key innovation: The antenna is made up of circularly polarized, aluminum-only unit cells—more on this in a moment—that can each send and receive on X-band frequencies (specifically, 7.145 to 7.19 gigahertz for the uplink and 8.4 to 8.45 GHz for the downlink). The entire antenna is an array of these unit cells, 32 on a side or 1,024 in total. The antenna is 32.5 by 32.5 inches (82.5 by 82.5 centimeters), allowing it to fit on top of a modestly sized lander, and it can achieve a downlink rate to Earth of 33 kilobits per second at 80 percent efficiency.

Let’s take a closer look at the unit cells I mentioned, to better understand how this antenna does what it does. Circular polarization is commonly used for space communications. You might be more familiar with linear polarization, which is often used for terrestrial wireless signals; you can imagine such a signal propagating across a distance as a 2D sine wave that’s oriented, say, vertically or horizontally relative to the ground. Circular polarization instead propagates as a 3D helix. This helix pattern makes circular polarization useful for deep space communications because the helix’s larger “cross section” doesn’t require that the transmitter and receiver be as precisely aligned. As you can imagine, a superprecise alignment across almost 750 million km is all but impossible. Circular polarization has the added benefit of being less sensitive to Earth’s weather when it arrives. Rain, for example, causes linearly polarized signals to attenuate more quickly than circularly polarized ones. 

Each unit cell, as mentioned, is entirely made of aluminum. Earlier antenna arrays that similarly use smaller component cells include dielectric materials like ceramic or glass to act as insulators. Unfortunately, dielectric materials are also vulnerable to Jupiter’s ionizing radiation. The radiation builds up a charge on the materials over time, and precisely because they’re insulators there’s nowhere for that charge to go—until it’s ultimately released in a hardware-damaging electrostatic discharge. So we can’t use them.

As mentioned before, metals are more resilient to ionizing radiation. The problem is they’re not insulators, and so an antenna constructed entirely out of metal is ­­still at risk of an electrostatic discharge damaging its components. We worked around this problem by designing each unit cell to be fed at a single point. The “feed” is the connection between an antenna and the radio’s transmitter and receiver. Typically, circularly polarized antennas require two perpendicular feeds to control the signal generation. But with a bit of careful engineering and the use of a type of automated optimization called a genetic algorithm, we developed a precisely shaped single feed that could get the job done. Meanwhile, a comparatively large metal post acts as a ground to protect each feed from electrostatic discharges.

The unit cells are placed in small 16-by-16 subarrays, four subarrays in total. Each of these subarrays is fed with something we call a suspended air stripline, in which the transmission line is suspended between two ground planes, turning the gap in between into a dielectric insulator. We can then safely transmit power through the stripline while still protecting the line from electric discharges that would build up on a dielectric like ceramic or glass. Additionally, suspended air striplines are low loss, which is perfect for the highly efficient antenna design we wanted.

Put together, the new antenna design accomplishes three things: It’s highly efficient, it can handle a large amount of power, and it’s not very sensitive to temperature fluctuations. Removing traditional dielectric materials in favor of air striplines and an aluminum-only design gives us high efficiency. It’s also a phased array, which means it uses a cluster of smaller antennas to create steerable, tightly focused signals. The nature of such an array is that each individual cell needs to handle only a fraction of the total transmission power. So while each individual cell can handle only a minuscule amount of power, each subarray can handle more than 6 kilowatts. That’s still low—much lower than the megawatt-range transmissions from Mars rovers—but it’s enough for the modest downlink rates I mentioned above. And finally, because the antenna is made of metal, it expands and contracts uniformly as the temperature changes. In fact, one of the reasons we picked aluminum is because the metal does not expand or contract much as temperatures change.

When I originally proposed this antenna concept to the Europa lander project, I was met with skepticism. Space exploration is typically a very risk-averse endeavor, for good reason—the missions are expensive, and a single mistake can end one prematurely. For this reason, new technologies may be dismissed in favor of tried-and-true methods. But this situation was different because without a new antenna design, there would never be a Europa mission. The rest of my team and I were given the green light to prove the antenna could work.

Designing, fabricating, and testing the antenna took only 6 months. To put that in context, the typical development cycle for a new space technology is measured in years. The results were outstanding. Our antenna achieved the 80 percent efficiency threshold on both the send and receive frequency bands, despite being smaller and lighter than other antennas. It also doesn’t require a delicate gimbal to point it toward Earth. Instead, the antenna’s subarrays act as a phased array capable of shaping the direction of the signal without reorienting the antenna.

In order to prove how successful our antenna could be, we subjected it to a battery of extreme environmental tests, including a handful of tests specific to Europa’s atypical environment.

One test is what we call thermal cycling. For this test, we place the antenna in a room called a thermal chamber and adjust the temperature over a large range—as low as –170 ℃ and as high as 150 ℃. We put the antenna through multiple temperature cycles, measuring its transmitting capabilities before, during, and after each cycle. The antenna passed this test without any issues.

The antenna also needed to demonstrate, like any piece of hardware that goes into space, resilience against vibrations. Rockets—and everything they’re carrying into space—shake intensely during launch, which means we need to be sure that anything that goes up doesn’t come apart on the trip. For the vibration test, we loaded the entire antenna onto a vibrating table. We used accelerometers at different locations on the antenna to determine if it was holding up or breaking apart under the vibrations. Over the course of the test, we ramped up the vibrations to the point where they approximate a launch.

Thermal cycling and vibration tests are standard tests for the hardware on any spacecraft, but as I mentioned, Europa’s challenging environment required a few additional nonstandard tests. We typically do some tests in anechoic chambers for antennas. You may recognize anechoic chambers as those rooms with wedge-covered surfaces to absorb any signal reflections. An anechoic chamber makes it possible for us to determine the antenna’s signal propagation over extremely long distances by eliminating interference from local reflections. One way to think about it is that the anechoic chamber simulates a wide open space, so we can measure the signal’s propagation and extrapolate how it will look over a longer distance.

What made this particular anechoic chamber test interesting is that it was also conducted at ultralow temperatures. We couldn’t make the entire chamber that cold, so we instead placed the antenna in a sealed foam box. The foam is transparent to the antenna’s radio transmissions, so from the point of view of the actual test, it wasn’t there. But by connecting the foam box to a heat exchange plate filled with liquid nitrogen, we could lower the temperature inside it to –170 ℃. To our delight, we found that the antenna had robust long-range signal propagation even at that frigid temperature.

The last unusual test for this antenna was to bombard it with electrons in order to simulate Jupiter’s intense radiation. We used JPL’s Dynamitron electron accelerator to subject the antenna to the entire ionizing radiation dose the antenna would see during its lifetime in a shortened time frame. In other words, in the span of two days in the accelerator, the antenna was exposed to the same amount of radiation as it would be during the six- or seven-year trip to Europa, plus up to 40 days on the surface. Like the anechoic chamber testing, we also conducted this test at cryogenic temperatures that were as close to those of Europa’s surface conditions as possible.

The reason for the electron bombardment test was our concern that Jupiter’s ionizing radiation would cause a dangerous electrostatic discharge at the antenna’s port, where it connects to the rest of the lander’s communications hardware. Theoretically, the danger of such a discharge grows as the antenna spends more time exposed to ionizing radiation. If a discharge happens, it could damage not just the antenna but also hardware deeper in the communications system and possibly elsewhere in the lander. Thankfully, we didn’t measure any discharges during our test, which confirms that the antenna can survive both the trip to and work on Europa.

We designed and tested this antenna for Europa, but we believe it can be used for missions elsewhere in the solar system. We’re already tweaking the design for the joint JPL/ESA Mars Sample Return mission that—as the name implies—will bring Martian rocks, soil, and atmospheric samples back to Earth. The mission is currently slated to launch in 2026. We see no reason why our antenna design couldn’t be used on every future Mars lander or rover as a more robust alternative—one that could also increase data rates 4 to 16 times those of  current antenna designs. We also could use it on future moon missions to provide high data rates.

Although there isn’t an approved Europa lander mission yet, we at JPL will be ready if and when it happens. Other engineers have pursued different projects that are also necessary for such a mission. For example, some have developed a new, multilegged landing system to touch down safely on uncertain or unstable surfaces. Others have created a “belly pan” that will protect vulnerable hardware from Europa’s cold. Still others have worked on an intelligent landing system, radiation-tolerant batteries, and more. But the antenna remains perhaps the most vital system, because without it there will be no way for the lander to communicate how well any of these other systems are working. Without a working antenna, the lander will never be able to tell us whether we could have living neighbors on Europa.

This article appears in the August 2021 print issue as “An Antenna Made for an Icy, Radioactive Hell.”

About the Author

Nacer E. Chahat is a senior antenna engineer at NASA’s Jet Propulsion Laboratory. In a previous article for IEEE Spectrum, he described the antennas that allowed microsatellites to fly to Mars.

China Tries To Solve Its Rocket Debris Problem

Post Syndicated from Andrew Jones original https://spectrum.ieee.org/tech-talk/aerospace/space-flight/chinas-rocket-debris-problem

On the morning of 17 June, China launched the first astronauts to its Tianhe space station module, with a Long March 2F rocket sending the crewed Shenzhou-12 spacecraft into orbit.

Overlooked from this major success, however, was that downrange from its Gobi Desert launch site, empty rocket stages fell to ground. As getting to orbit is about reaching velocity high enough to overcome gravity (roughly 7.8 kilometers per second), rockets consist of stages, with tanks and engines optimized for flying through atmosphere dumped to reduce mass once empty. A video posted on the Twitter-like Sina Weibo emerged that seems to show one of these as part of the recovery process, with apparent residual, hazardous propellant leaking from the broken boosters. According to the source, road closures and evacuations allowed a safe clean up.

Stunningly, this is not unusual for Chinese space launches. China’s three main spaceports were built during the Cold War when security was paramount, with the U.S. and Soviet Union considering the possibility of preemptive strikes on facilities linked to China’s fledging nuclear weapon capabilities. Only the Wenchang launch center, established in 2016 for new rockets, is on the coast. As China has been aiming to launch as many as 40 or more times annually in the last few years, the issue is growing, with some stages falling on or near inhabited areas, including close to a school.

However where the stages fall and how they are dealt with is not as haphazard as it appears. The areas in which stages and side boosters fall are calculated to avoid major populations, and local warnings and evacuation orders are issued and implemented in advance. The array of amateur footage of falling rocket stages backs up the claim that the events are known and expected. No casualties from these events have so far been reported.

Yet this approach is costly, disruptive and not without continued risks and occasional damage.

To mitigate and eventually solve the problem, the China Aerospace Science and Technology Corp. (CASC), the country’s main space contractor is developing controllable parafoils to constrain the areas in which the stages fall, most recently tested on a Long March 3B launch from Xichang, southwest China, one of China’s workhorse launchers, which most frequently threaten inhabited areas. Grid fins, the kind which help guide Falcon 9 rocket core stages to landing areas, have been tested on smaller Long March 2C and 4B launch vehicles.

The latter step is part of attempts to develop rockets that can launch, land and be reused like the Falcon 9, thus controlling the fall of large first stages.

The Long March 8, which had a debut (expendable) flight in December, is expected to be CASC’s first such launcher. Chinese commercial companies including Landspace, iSpace, Galactic Energy and Deep Blue Aerospace, are also working on reusable rockets. Low altitude hop tests are expected this year. Though, as SpaceX has demonstrated in a self-depreciating compilation, landing rockets vertically is no mean feat.

Additionally, the Long March 7A rocket, which launches from the coast, is expected to eventually replace the aging Long March 3B rocket for launches to geostationary orbit. As a bonus the 7A uses relatively clean kerosene and liquid oxygen propellant instead of the toxic fuel and oxidizer mix used by the 3B. The Long March 2F used for crewed launches could also be replaced by a Long March 7 or a low-Earth orbit version of a new-generation rocket being developed to eventually send Chinese astronauts to the moon.

China has also developed the ability to conduct launches at sea (though the most recent such launch flew directly over Taiwan). Its new Long March 5B, which launches from the coast, also has its own particular issue, namely the first stage actually (and unusually) reaching orbit, and returning to Earth wherever and whenever the atmosphere drags it back down.

Despite these measures, launching over land and population centers is fraught with risk. The debris issues and events above are when things go well; failures could bring yet greater danger. China’s space industry and activities have expanded greatly in recent decades, including lunar and planetary exploration, human spaceflight, remote sensing, spy, weather and other satellites, as well as a new commercial space sector. Some areas of space operations playing catch up.

No Sleep Till Jezero: Touchdown Time for Mars Perseverance Rover?

Post Syndicated from Ned Potter original https://spectrum.ieee.org/automaton/aerospace/space-flight/nasa-perseverance-rover-lands-at-mars-jezero-crater

They used to call it “Seven Minutes of Terror”—a NASA probe would slice into the atmosphere of Mars at more than 20,000 kilometers per hour; slow itself with a heat shield, parachute, and rocket engines; and somehow land intact on the surface, just six or seven minutes later, while its makers waited helplessly on Earth. The computer-animated landing videos NASA produced before previous Mars missions—in 2004, 2008, and 2012—became online sensations. “If any one thing doesn’t work just right,” said NASA engineer Tom Rivellini in the last one, “it’s game over.”

NASA is now trying again, with the Perseverance rover and the tiny Ingenuity drone bolted to its undercarriage. NASA will be live-streaming the landing (across many video and social media platforms as well as in a Spanish language feed and in an immersive, 360-degree view) beginning at 11:15 a.m. PST/2:15 p.m. EST/19:15 UTC on Thursday, 18 February 2021. 

While this year’s animated landing video is as dramatic as ever, the tone has changed. “The models and simulations of landing at Jezero crater have assessed the probability of landing safely to be above 99 percent,” says Swati Mohan, the guidance, navigation and controls operations lead for the mission.

There isn’t a trace of arrogance in her voice as she says this. She’s been working on this mission for five years, has teammates who were around for NASA’s first Mars rover in 1997, and knows what they’re up against. Yes, they say, 99 percent reliability is realistic. 

The biggest advance over past missions is a system called Terrain Relative Navigation—TRN for short. In essence, it gives the spacecraft a way to know precisely where it’s headed, so it can steer clear of hazards on the very jagged landscapes that scientists most want to explore. If all goes as planned, Perseverance will image the Martian surface in rapid sequence as it plows toward its landing site, and compare what it sees to onboard maps of the ground below. The onboard database is primarily based on high-resolution images from NASA’s Mars Reconnaissance Orbiter, which has been mapping the planet from an altitude of 250 kilometers since 2006. Its images have a resolution of 30 cm per pixel. 

“This is kind of along the same lines as what the Apollo astronauts did with people in the loop, back in the day. Those guys looked out the window,” says Allen Chen, the mission’s entry, descent, and landing lead. “For the first time here on Mars, we’re automating that.”

There will still be plenty of anxious controllers at NASA’s Jet Propulsion Laboratory in California. After all, the spacecraft will be on its own, about 209 million kilometers from Earth, far enough away that its radio signals will take more than 11 minutes to reach home. The ship should reach the surface four minutes before engineers even know it has entered the Martian atmosphere. “Landing on Mars is hard enough,” says Thomas Zurbuchen, NASA’s associate administrator for science missions. “It is not guaranteed that we will be successful.” 

But the new navigation technology makes a very risky landing possible. Jezero crater, which was probably once a lake at the end of a river delta, has been on scientists’ shortlist since the 1990s as place to look for signs of past life on Mars. But engineers voted against it until this mission. Previous landers used radar, which Mohan likens to “closing your eyes and holding your hands out in front of you. You can use that to slow down and to stop. But with your eyes closed you can’t really control where you’re coming down.”

Everything happens fast as Perseverance comes in, following a long arcing path. Fewer than 90 seconds before scheduled touchdown, and about 2,100 meters above the Martian surface, the TRN system makes its calculations. Its rapid-fire imaging should by then have told it where it is relative to the ground below, and from that it can project its likely touchdown spot. If the ship is headed for a ridge, a crevice, or a dangerous outcropping of rock, the computer will send commands to eight downward-facing rocket engines to change the descent trajectory. 

In that final minute, as the spacecraft slows from 300 kilometers per hour to zero, the TRN system can shift the touchdown spot by up to 330 meters. The safe targets map in Perseverance’s memory is detailed enough, the team says, that the ship should be able to reach a suitable location for a safe landing. 

“It’s able to thread the needle of all these different hazards to land in the safe spots in between these hazards,” says Mohan, “and by landing amongst the hazards it’s also landing amongst the scientific features of interest.”

NASA’s Mars Perseverance Rover Should Leave Past Space Probes in the Dust

Post Syndicated from Ned Potter original https://spectrum.ieee.org/tech-talk/aerospace/space-flight/nasa-mars-perseverance-rover-should-leave-past-space-probes-in-dust

If you could stand next to NASA’s Perseverance rover on the Martian surface… well, you’d be standing on Mars. Which would be a pretty remarkable thing unto itself. But if you were waiting for the rover to go boldly exploring, your mind might soon wander. You’d be forgiven for thinking this is like watching paint dry. The Curiosity rover, which landed on Mars in 2012 and has the same chassis, often goes just 50 or 60 meters in a day. 

Which is why Rich Rieber and his teammates have been at work for five years, building a new driving system for Perseverance that they hope will set some land-speed records for Mars. 

“The reason we’re so concerned with speed is that if we’re driving, we’re not doing science,” he said. “If you’re on a road trip and you drive to Disneyland, you want to get to Disneyland. It’s not about driving, you want to be there.”

Rieber is the lead mobility systems engineer for the Perseverance mission. He ran the development of the drivetrain, suspension, engineering cameras, machine vision, and path-planning algorithms that should allow the rover to navigate the often-treacherous landscape around Perseverance’s destination, called Jezero crater. With luck, Perseverance will leave past rovers in the dust. 

“Perseverance is going to drive three times faster than any previous Mars rover,” said Matt Wallace, the deputy mission manager at NASA’s Jet Propulsion Lab. “We have added a lot of surface autonomy, a lot of new AI if you will, to this vehicle so that we can complete the mission on the surface.”

The rover, if everything works, will still have a maximum speed of only 4.4 cm per second, which is one-thirtieth as fast as human walking speed. It would travel the length of a football field in 45 minutes. But, says Rieber, “It is head and shoulders the fastest rover on Mars, and that’s not because we are driving the vehicle faster. It’s because we’re spending less time thinking about how.” 

Perseverance bases much of its navigational ability on an onboard map created from images taken by NASA’s Mars Reconnaissance Orbiter–detailed enough that it can show features less than 30 cm across. That helps tell the rover where it is. It then adds stereo imagery from two navigational cameras on its top mast and six hazard-detection cameras on its body. Each camera has a 20-megapixel color sensor. The so-called Navcams have a 90-degree field of view. They can pick out a golf ball-sized object 25 meters away.

These numbers add up: The technology should allow the rover to pick out obstacles as it goes—a ridge, an outcropping of rock, a risky-looking depression—and steer around many of them without help from Earth. Mission managers plan to send the rover its marching orders each morning, Martian time, and then wait for it to report its progress the next time it can communicate with Earth. 

Earlier rovers often had to image where they were and stop for the day to await new instructions from Earth. Curiosity, on days it’s been ordered to drive, only spends 13 percent of its time actually in motion. Perseverance may more than triple that. 

There are, however, still myriad complexities to driving on Mars. For instance, mission engineers can calculate how far Perseverance will go with each revolution of its six wheels. But what if the wheels on one side slip because they were driving through sand? How far behind or off its planned path might it be? The rover’s computers can figure that out, but their processing capacity is limited by the cosmic radiation that bombards spacecraft outside the Earth’s protective magnetosphere. “Our computer is like top of the line circa 1994,” said Rieber, “and that’s because of radiation. The closer [together] you have your transistors, the more susceptible they are.”

Matt Wallace, the deputy project manager, has been on previous missions when—sometimes only in hindsight—engineers realized they had barely escaped disaster. “There’s never a no-risk proposition here when you’re trying to do something new,” he said. 

But the payoff would come if the rover came across chemical signatures of life on Mars from billions of years ago. If Perseverance finds that, it could change our view of life on Earth.

Is there a spot somewhere at Jezero crater that could offer such an incredible scientific breakthrough? The first step is to drive to it.

10 Exciting Engineering Milestones to Look for in 2021

Post Syndicated from Eliza Strickland original https://spectrum.ieee.org/aerospace/space-flight/10-exciting-engineering-milestones-to-look-for-in-2021

graphic link to special report landing page
  • A Shining Light

    Last year, germicidal ultraviolet light found a place in the arsenal of weapons used to fight the coronavirus, with upper-air fixtures placed near hospital-room ceilings and sterilization boxes used to clean personal protective equipment. But a broader rollout was prevented by the dangers posed by UV-C light, which damages the genetic material of viruses and humans alike. Now, the Tokyo-based lighting company Ushio thinks it has the answer: lamps that produce 222-nanometer wavelengths that still kill microbes but don’t penetrate human eyes or skin. Ushio’s Care222 lamp modules went into mass production at the end of 2020, and in 2021 they’ll be integrated into products from other companies—such as Acuity Brands’ lighting fixtures for offices, classrooms, stores, and other occupied spaces.

  • Quantum Networking

    Early this year, photons will speed between Stony Brook University and Brookhaven National Laboratory, both in New York, in an ambitious demonstration of quantum communication. This next-gen communication concept may eventually offer unprecedented security, as a trick of quantum mechanics will make it obvious if anyone has tapped into a transmission. In the demo, “quantum memory buffers” from the startup Qunnect will be placed at each location, and photons within those buffers will be entangled with each other over a snaking 70-kilometer network.

  • Winds of Change

    Developers of offshore wind power quickly find themselves in deep water off the coast of California; one prospective site near Humboldt Bay ranges from 500 to 1,100 meters deep. These conditions call for a new breed of floating wind turbine that’s tethered to the seafloor with strong cables. Now, that technology has been demonstrated in pilot projects off the coasts of Scotland and Portugal, and wind power companies are eager to gain access to three proposed sites off the California coast. They’re expecting the U.S. Bureau of Ocean Energy Management to begin the process of auctioning leases for at least some of those sites in 2021.

  • Driverless Race Cars

    The Indianapolis Motor Speedway, the world’s most famous auto racetrack, will host an unprecedented event in October: the first high-speed race of self-driving race cars. About 30 university teams from around the world have signed up to compete in the Indy Autonomous Challenge, in which souped-up race cars will reach speeds of up to 320 kilometers per hour (200 miles per hour). To win the US $1 million top prize, a team’s autonomous Dallara speedster must be first to complete 20 laps in 25 minutes or less. The deep-learning systems that control the cars will be tested under conditions they’ve never experienced before; both sensors and navigation tools will have to cope with extreme speed, which leaves no margin for error.

  • Robots Below

    The robots participating in DARPA’s Subterranean Challenge have already been tested on three different courses; they’ve had to navigate underground tunnels, urban environments, and cave networks (although the caves portion was switched to an all-virtual course due to the pandemic). Late this year, SubT teams from across the world will put it all together at the final event, which will combine elements of all three subdomains into a single integrated challenge course. The robots will have to demonstrate their versatility and endurance in an obstacle-filled environment where communication with the world above ground is limited. DARPA expects pandemic conditions to improve enough in 2021 to make a physical competition possible.

  • Mars or Bust

    In February, no fewer than three spacecraft are due to rendezvous with the Red Planet. It’s not a coincidence—the orbits of Earth and Mars have brought the planets relatively close together this year, making the journey between them faster and cheaper. China’s Tianwen-1 mission plans to deliver an orbiter and rover to search for water beneath the surface; the United Arab Emirates’ Hope orbiter is intended to study the Martian climate; and a shell-like capsule will deposit NASA’s Perseverance rover, which aims to seek signs of past life, while also testing out a small helicopter drone named Ingenuity. There’s no guarantee that the spacecraft will reach their destinations safely, but millions of earthlings will be rooting for them.

  • Stopping Deepfakes

    By the end of the year, some Android phones may include a new feature that’s intended to strike a blow against the ever-increasing problem of manipulated photos and videos. The anti-deepfake tech comes from a startup called Truepic, which is collaborating with Qualcomm on chips for smartphones that will enable phone cameras to capture “verified” images. The raw pixel data, the time stamp, and location data will all be sent over secure channels to isolated hardware processors, where they’ll be put together with a cryptographic seal. Photos and videos produced this way will carry proof of their authenticity with them. “Fakes are never going to go away,” says Sherif Hanna, Truepic’s vice president of R&D. “Instead of trying to prove what’s fake, we’re trying to protect what’s real.”

  • Faster Data

    In a world reshaped by the COVID-19 pandemic, in which most office work, conferences, and entertainment have gone virtual, cloud data centers are under more stress than ever before. To ensure that people have all the bandwidth they need whenever they need it, service providers are increasingly using networks of smaller data centers within metropolitan areas instead of the traditional massive data center on a single campus. This approach offers higher resilience and availability for end users, but it requires sending torrents of data between facilities. That need will be met in 2021 with new 400ZR fiber optics, which can send 400 gigabits per second over data center interconnects of between 80 and 100 kilometers. Verizon completed a trial run last September, and experts believe we’ll see widespread deployment toward the end of this year.

  • Your Next TV

    While Samsung won’t confirm it, consumer-electronics analysts say the South Korean tech giant will begin mass production of a new type of TV in late 2021. Samsung ended production of liquid crystal display (LCD) TVs in 2020, and has been investing heavily in organic light-emitting diode (OLED) display panels enhanced with quantum dot (QD) technology. OLED TVs include layers of organic compounds that emit light in response to an electric current, and they currently receive top marks for picture quality. In Samsung’s QD-OLED approach, the TV will use OLEDs to create blue light, and a QD layer will convert some of that blue light into the red and green light needed to make images. This hybrid technology is expected to create displays that are brighter, higher contrast, and longer lasting than today’s best models.

  • Brain Scans Everywhere

    Truly high-quality data about brain activity is hard to come by; today, researchers and doctors typically rely either on big and expensive machines like MRI and CT scanners or on invasive implants. In early 2021, the startup Kernel is launching a wearable device called Kernel Flow that could change the game. The affordable low-power device uses a type of near-infrared spectroscopy to measure changes in blood flow within the brain. Within each headset, 52 lasers fire precise pulses, and reflected light is picked up by 312 detectors. Kernel will distribute its first batch of 50 devices to “select partners” in the first quarter of the year, but company founder Bryan Johnson hopes the portable technology will one day be ubiquitous. At a recent event, he described how consumers could eventually use Kernel Flow in their own homes.

SpaceX, Blue Origin, and Dynetics Compete to Build the Next Moon Lander

Post Syndicated from Jeff Foust original https://spectrum.ieee.org/aerospace/space-flight/spacex-blue-origin-and-dynetics-compete-to-build-the-next-moon-lander

graphic link to special report landing page

In March 2019, Vice President Mike Pence instructed NASA to do something rarely seen in space projects: move up a schedule. Speaking at a meeting of the National Space Council, Pence noted that NASA’s plans for returning humans to the moon called for a landing in 2028. “That’s just not good enough. We’re better than that,” he said. Instead, he announced that the new goal was to land humans on the moon by 2024.

That decision wasn’t as radical as it might have seemed. The rocket that is the centerpiece of NASA’s lunar exploration plans, the Space Launch System, has been in development for nearly a decade and is scheduled to make its first flight in late 2021. The Orion, a crewed spacecraft that will be launched on that rocket, is even older, dating back to the previous NASA initiative to send humans to the moon, the Constellation program in the mid-2000s.

What’s missing, though, is the lander that astronauts will use to go from the Orion in lunar orbit down to the surface and back. NASA was just starting to consider new ideas for lunar landers when Pence gave his speech. Indeed, proposals for an initial round of studies were due to NASA just the day before he spoke. Those studies have since progressed, and NASA may settle on a design for its upcoming moon lander as soon as next month.

To meet Pence’s 2024 deadline, it was clear that NASA would have to move faster than normal. That meant moving differently.

The Lunar Module, or LM, used for the Apollo program, was developed through a standard government contract with Grumman Corp. But in the half century since Apollo, not only has the technology of spaceflight changed, but so has the business. Commercial programs to ferry cargo and crew to the space station demonstrated there were opportunities for government to partner with industry, with companies covering some of the development costs in exchange for using the vehicles they designed to serve other customers.

That approach, NASA argued, would allow it to support more companies in the early phases of the program and perhaps through full-scale lander development. “We want to have numerous suppliers that are competing against each other on cost, and on innovation, and on safety,” NASA Administrator Jim Bridenstine told the Senate Commerce Committee in September of 2020.

That was the approach NASA decided to follow to develop what it calls the Human Landing System (HLS), part of its upcoming Artemis program of lunar exploration. NASA would award up to four contracts for less than a year of initial work to refine lander designs. Based on the quality of those lander designs as well as the available funding—including the share of the costs companies offered to pay—NASA would select one or more for continued development.

Proposals for the HLS program were due to NASA in November of 2019. On 30 April 2020, NASA announced the winners of three contracts with a combined US $967 million for those initial studies: Blue Origin, Dynetics, and SpaceX. “Let’s make no mistake about it: We are now on our way,” said Douglas Loverro, then a NASA official, at the briefing announcing the contracts. Loverro, who was the NASA associate administrator responsible for human spaceflight, added, “We’ve got all the pieces we need.” Later this year, NASA will choose which of these three to pursue.

The three landers are as different as the companies NASA selected. Blue Origin, in Kent, Wash., has the significant financial resources of its founder, Amazon.com’s Jeff Bezos, but chose to partner with three other major companies on its lander: Draper, Lockheed Martin, and Northrop Grumman. “What we’re trying to do is take the best of what all the partners bring to build a truly integrated lander vehicle,” says John Couluris, program manager for the HLS at Blue Origin.

Its design is the most similar of the three to the original Apollo LM. Blue Origin is leading the development of the descent stage, which brings the lander down to the surface, using a version of an uncrewed lunar lander called Blue Moon that it had previously been working on. Lockheed Martin is building the ascent stage, which will carry astronauts back into lunar orbit. Its crew cabin is based on the one the company designed for the Orion spacecraft. Northrop Grumman will provide a transfer stage, which will move the combined ascent and descent stages from a high lunar orbit to a low one, from which the descent stage takes over for the landing. Draper Laboratory, in Cambridge, Mass., is providing the avionics for the combined lander.

That modular approach, Couluris argues, has advantages over building a larger integrated lander. “The three elements provide a lot of flexibility in launch-vehicle selection,” he says, allowing NASA to use any number of vehicles to send the modules to the moon. “It also allows three independent efforts to go in parallel as Blue Origin leads the overall integrated effort.”

The early work on the lander has included building full-scale models of the ascent and descent modules and installing them in a training facility at NASA’s Johnson Space Center. This gives engineers and astronauts a hands-on way to see how the modules work together and determine the best places to put major components before the design is fixed.

“Understanding things that affect the primary structure are important. For example, are the windows in the right spot?” says Kirk Shireman, a former NASA space-station program manager who joined Lockheed Martin recently as vice president of lunar campaigns. “They impact big pieces of the structure that are long-lead and need to be finalized so we can begin manufacturing.”

Dynetics, a Huntsville, Ala.–based engineering company, is similarly working on its lander with other firms—more than two dozen. These include Sierra Nevada Corp., which is building the Dream Chaser cargo vehicle for the space station; Thales Alenia Space, which built pressurized module structures for the station and other spacecraft; and launch-vehicle company United Launch Alliance (ULA).

Dynetics took a very different approach with its lander, though, creating a single module ringed by thrusters and propellant tanks. That results in a low-slung design that puts the crew cabin just a couple of meters off the ground, making it easy for astronauts to get from the module to the surface and back.

“We felt like it was important to get the crew module as close to the lunar surface as we could to ease the operations of getting in and out,” says Robert Wright, a program manager for space systems at Dynetics.

To make that approach work—and also be carried into space using available launch vehicles—Dynetics proposes to fuel the lander only after it is orbiting the moon. The lander will be launched with empty propellant tanks on a ULA Vulcan Centaur rocket and placed in lunar orbit. Two more Vulcan Centaur launches will follow, each about two to three weeks apart, carrying the liquid oxygen and methane propellants needed to land on the moon and return to orbit.

Refueling in space using cryogenic propellants requires new technology, but Dynetics believes it can demonstrate it in time to support a 2024 landing. “We worked closely with NASA on our concept of operations, and the Orion plans, to ensure that our operational scenario is viable and feasible,” says Kim Doering, vice president of space systems at Dynetics.

The third contender, SpaceX, is offering a lunar lander based on Starship, the reusable launch vehicle it is developing and testing at a site on the Texas coast near Brownsville. Starship, in many respects, looks oversized for the job, resembling the giant rocket that the graphic-novel hero Tintin used in his fictional journey to the moon. Starship’s crew cabin is so high off the lunar surface that SpaceX plans to use an elevator to transport astronauts down to the surface and back.

“Starship works well for the HLS mission,” says Nick Cummings, director of civil-space advanced development at SpaceX. “We did look at alternative architectures, multi-element architectures, but we came back because Starship provides a lot of capability.” That capability includes the ability to carry what he described as “extraordinarily large cargo” to the surface of the moon, for example large rovers.

The Starship used for lunar missions will be different from those flying to and from Earth. The lunar Starship lacks the flaps and heat shield needed for reentering Earth’s atmosphere. It will have several large Raptor engines, but also a smaller set of thrusters used for landing and taking off on the moon because the Raptors are too powerful.

Starship, like the Dynetics lander, will require in-space refueling. The lunar ­Starship will be launched into Earth orbit, and several Starships will follow with propellant to transfer to it before it heads to the moon.

SpaceX CEO Elon Musk said at a conference in October that he expects to demonstrate Starship-to-Starship refueling in 2022. “As soon as you’ve got orbital refilling, you can send significant payload to the moon,” he said.

All three companies face significant obstacles to overcome in their lander development. The most obvious ones are technical: New rocket engines need to be built and new technologies, like in-space refueling, need to be demonstrated, all on a tight schedule to meet the 2024 deadline.

NASA acknowledged that crunch in a document explaining why it chose those three companies. Blue Origin, for example, has “a very significant amount of development work” that needs to be completed “on what appears to be an aggressive timeline.” Dynetics’s lander requires technologies that “need to be developed at an unprecedented pace.” And SpaceX’s concept “requires numerous, highly complex launch, rendezvous, and fueling operations which all must succeed in quick succession in order to successfully execute on its approach.”

The companies nevertheless remain optimistic about staying on schedule. “It certainly is an aggressive timeline,” acknowledged SpaceX’s Cummings. But, based on the company’s experience with other programs, “we think this is very doable.”

Congress may be harder to convince. Some members remain skeptical that NASA’s approach to returning humans to the moon by 2024, including its use of partnerships with industry, is the right one.

NASA’s Bridenstine, in many public comments, said he appreciates that Congress is willing to provide at least some funding for the lunar lander program. “Accelerating it to 2024 requires a $3.2 billion budget for 2021,” he told senators last September. That funding decision, he added, needs to come by February, when NASA will select the companies that will continue development work for the HLS program. “If we get to February of 2021 without [a $3.2 billion] appropriation, that’s really going to put the brakes on our ability to achieve a moon landing by as early as 2024,” he warned. And the current Senate proposal, now being negotiated with the House, budgets only $1 billion.

In space, as on Earth, the most important fuel is money.

This article appears in the January 2021 print issue as “Three Ways to the Moon.”

Nuclear-Powered Rockets Get a Second Look for Travel to Mars

Post Syndicated from Prachi Patel original https://spectrum.ieee.org/aerospace/space-flight/nuclear-powered-rockets-get-a-second-look-for-travel-to-mars

For all the controversy they stir up on Earth, nuclear reactors can produce the energy and propulsion needed to rapidly take large spacecraft to Mars and, if desired, beyond. The idea of nuclear rocket engines dates back to the 1940s. This time around, though, plans for interplanetary missions propelled by nuclear fission and fusion are being backed by new designs that have a much better chance of getting off the ground.

Crucially, the nuclear engines are meant for interplanetary travel only, not for use in the Earth’s atmosphere. Chemical rockets launch the craft out beyond low Earth orbit. Only then does the nuclear propulsion system kick in.

The challenge has been making these nuclear engines safe and lightweight. New fuels and reactor designs appear up to the task, as NASA is now working with industry partners for possible future nuclear-fueled crewed space missions. “Nuclear propulsion would be advantageous if you want to go to Mars and back in under two years,” says Jeff Sheehy, chief engineer in NASA’s Space Technology Mission Directorate. To enable that mission capability, he says, “a key technology that needs to be advanced is the fuel.”

Specifically, the fuel needs to endure the superhigh temperatures and volatile conditions inside a nuclear thermal engine. Two companies now say their fuels are sufficiently robust for a safe, compact, high-performance reactor. In fact, one of these companies has already delivered a detailed conceptual design to NASA.

Nuclear thermal propulsion uses energy released from nuclear reactions to heat liquid hydrogen to about 2,430 °C—some eight times the temperature of nuclear-power-plant cores. The propellant expands and jets out the nozzles at tremendous speeds. This can produce twice the thrust per mass of propellant as compared to that of chemical rockets, allowing nuclear-powered ships to travel longer and faster. Plus, once at the destination, be it Saturn’s moon Titan or Pluto, the nuclear reactor could switch from propulsion system to power source, enabling the craft to send back high-quality data for years.

Getting enough thrust out of a nuclear rocket used to require weapons-grade, highly enriched uranium. Low-enriched uranium fuels, used in commercial power plants, would be safer to use, but they can become brittle and fall apart under the blistering temperatures and chemical attacks from the extremely reactive hydrogen.

However, Ultra Safe Nuclear Corp. Technologies (USNC-Tech), based in Seattle, uses a uranium fuel enriched to below 20 percent, which is a higher grade than that of power reactors but “can’t be diverted for nefarious purposes, so it greatly reduces proliferation risks,” says director of engineering Michael Eades. The company’s fuel contains microscopic ceramic-coated uranium fuel particles dispersed in a zirconium carbide matrix. The microcapsules keep radioactive fission by-products inside while letting heat escape.

Lynchburg, Va.–based BWX Technologies, is working under a NASA contract to look at designs using a similar ceramic composite fuel—and also examining an alternate fuel form encased in a metallic matrix. “We’ve been working on our reactor design since 2017,” says Joe Miller, general manager for the company’s advanced technologies group.

Both companies’ designs rely on different kinds of moderators. Moderators slow down energetic neutrons produced during fission so they can sustain a chain reaction, instead of striking and damaging the reactor structure. BWX intersperses its fuel blocks between hydride elements, while USNC-Tech’s unique design integrates a beryllium metal moderator into the fuel. “Our fuel stays in one piece, survives the hot hydrogen and radiation conditions, and does not eat all the reactor’s neutrons,” Eades says.

Princeton Plasma Physics Laboratory scientists are using this experimental reactor to heat fusion plasmas up to one million degrees C—on the long journey to developing fusion-powered rockets for interplanetary travel.

There is another route to small, safe nuclear-powered rockets, says ­Samuel Cohen at Princeton Plasma Physics Laboratory: fusion reactors. Mainline fusion uses deuterium and tritium fuels, but Cohen is leading efforts to make a reactor that relies on fusion between deuterium atoms and helium-3 in a high-temperature plasma, which produces very few neutrons. “We don’t like neutrons because they can change structural material like steel to something more like Swiss cheese and can make it radioactive,” he says. The Princeton lab’s concept, called Direct Fusion Drive, also needs much less fuel than conventional fusion, and the device could be one-thousandth as large, Cohen says.

Fusion propulsion could in theory far outperform fission-based propulsion, because fusion reactions release up to four times as much energy, says NASA’s Sheehy. However, the technology isn’t as far along and faces several challenges, including generating and containing the plasma and efficiently converting the energy released into directed jet exhaust. “It could not be ready for Mars missions in the late 2030s,” he says.

USNC-Tech, by contrast, has already made small hardware prototypes based on its new fuel. “We’re on track to meet NASA’s goal to have a half-scale demonstration system ready for launch by 2027,” says Eades. The next step would be to build a full-scale Mars flight system, one that could very well drive a 2035 Mars mission.

This article appears in the January 2021 print issue as “Nuclear-Powered Rockets Get a Second Look.”

Japan Prepares to Welcome Home Asteroid Explorer Hayabusa2

Post Syndicated from John Boyd original https://spectrum.ieee.org/tech-talk/aerospace/space-flight/japan-prepares-to-welcome-home-asteroid-explorer-hayabusa2

Okaerinasai is Japanese for “Welcome back.” It’s a word everyone at the Japan Aerospace Exploration Agency JAXA will be shouting together around 2 am Tokyo time on December 6, when a capsule ejected from the Hayabusa2 space probe is due to land in Woomera, South Australia, after a 5.2 billion kilometer round-trip.

The reentry capsule is expected to contain precious particles scooped from the rock-strewn surface and subsurface of Ryugu, a diamond-shape asteroid less than a kilometer in diameter. This difficult trick was pulled off as Ryugu traveled on its 16-month orbit around the sun between Earth and Mars. What’s more, Hayabusa2 was able to land twice on the spinning asteroid and complete a series of missions. Perhaps the most difficult and spectacular of these was using an impactor to form a crater on the asteroid for gathering particles from below its surface—one of a number of firsts in space exploration Hayabusa2 has achieved.

Providing all goes as planned, the capsule will separate from the spacecraft on December 5, some 220,000 km from Earth. After which Hayabusa2 will enter an escape trajectory to depart Earth and commence on an extension of its mission. So long as the craft is still operational and has 50 percent of its xenon fuel remaining to drive its ion thruster engines, JAXA has set it the goal of visiting and observing an asteroid of a type never explored before. If successful, Hayabusa2 will reach its target in 2031.

In a press briefing a week before the landing, the project’s mission manager Makoto Yoshikawa explained how a JAXA team, working with the Australian Space Agency, will locate and retrieve the capsule. Ground stations and an airplane flying above the clouds will triangulate the capsule fireball’s progress through the Earth’s atmosphere by measuring its light trail. Then, at an altitude of 10 km above the Earth, the capsule will deploy a parachute and land somewhere (depending on weather conditions) within a 100 km2 area of the Woomera desert

Yoshikawa described how JAXA track and trace the capsule. Four marine radar units have been set up around the predicted landing area. Their fan-beam horizontal rotating antenna will track an umbrella made of radar-reflective-cloth attached to the top of the descending parachute. At the same time, a radio beacon in the capsule will begin signaling its location. 

“A helicopter and a team on the ground will track the beacon’s signal that will continue transmitting after landing,” Yoshikawa added. “We’re also bringing drones to help us find it as quickly as possible.”

The capsule will be taken by helicopter to a quick-look facility established in the Woomera Prohibited Area. There, the instrument module and sealed containers holding the Ryugu samples will be removed, including any gas released by the particles, and stored and sealed in special containers and airlifted to Japan. The aim is to complete all this in less than 100 hours after the landing to minimize any risk of contamination.

Once at JAXA, the samples will be removed in a vacuum environment inside a cleanroom. Over the next two years, each particle will be analyzed, described, and curated, with some of the particles being sent to international organizations, including NASA, for further study.

In a separate press briefing in Australia on December 1, Masaki Fujimoto, a Deputy Director at JAXA, explained why the samples taken from Ryugu are so important. Earth, being relatively close to the sun, was created dry without much water present. Something must have brought the H2O here. Ryugu is a primordial asteroid born outside the inner solar system and is the kind of body that could have brought water and organic materials to our planet that enabled the creation of life.

Analysis of the collected samples, says Fujimoto, “could help answer the fundamental question of how our planet became habitable.”  

He said that the asteroid samples gathered will likely amount to around one gram. “One gram may sound small to some of you,” said Fujimoto, “but for us, it is huge and enough to address the science questions we have in mind.”

Update (Dec. 6): JAXA confirmed the reentry capsule entered the Earth’s atmosphere at 2.28 a.m. Japan standard time on December 6. A helicopter searched for and located it in the Woomera desert at 4.47, then flew it to the quick look facility in the Woomera Prohibited Area, arriving just after 8 a.m. The JAXA recovery team is expected to extract any gas from the captured Ryugu samples. On its approach and orbit, beginning on December 5, Hayabusa2 performed several trajectory maneuvers to successfully depart Earth’s orbit and has now set out on its extended mission to observe an asteroid it hopes to visit in 2031.

NASA Study Proposes Airships, Cloud Cities for Venus Exploration

Post Syndicated from Evan Ackerman original https://spectrum.ieee.org/aerospace/space-flight/nasa-study-proposes-airships-cloud-cities-for-venus-exploration

Editor’s note: It’s been 35 years since a pair of robotic balloons explored the clouds of Venus. The Soviet Vega 2 and Vega 2 probes didn’t manage to find any Venusians, but that may have been because we didn’t know exactly what to look for. On 14 September 2020, a study published in Nature suggested that traces of phosphine in Venus’ atmosphere could be an indication of a biological process: that is, of microbial alien life. If confirmed, such a finding could completely change the way we think about the universe, which has us taking a serious look at what it would take to get human explorers to Venus in the near future. This article was originally published on 16 December 2014.

It has been accepted for decades that Mars is the next logical place for humans to explore. Mars certainly seems to offer the most Earth-like environment of any other place in the solar system, and it’s closer to Earth than just about anyplace else, except Venus. But exploration of Venus has always been an enormous challenge: Venus’s surface is hellish, with 92 atmospheres of pressure and temperatures of nearly 500 °C.

The surface of Venus isn’t going to work for humans, but what if we ignore the surface and stick to the clouds? Dale Arney and Chris Jones, from the Space Mission Analysis Branch of NASA’s Systems Analysis and Concepts Directorate at Langley Research Center, in Virginia, have been exploring that idea. Perhaps humans could ride through the upper atmosphere of Venus in a solar-powered airship. Arney and Jones propose that it may make sense to go to Venus before we ever send humans to Mars.

To put NASA’s High Altitude Venus Operational Concept (HAVOC) mission in context, it helps to start thinking about exploring the atmosphere of Venus instead of exploring the surface. “The vast majority of people, when they hear the idea of going to Venus and exploring, think of the surface, where it’s hot enough to melt lead and the pressure is the same as if you were almost a mile underneath the ocean,” Jones says. “I think that not many people have gone and looked at the relatively much more hospitable atmosphere and how you might tackle operating there for a while.”

At 50 kilometers above its surface, Venus offers one atmosphere of pressure and only slightly lower gravity than Earth. Mars, in comparison, has a “sea level” atmospheric pressure of less than a hundredth of Earth’s, and gravity just over a third Earth normal. The temperature at 50 km on Venus is around 75 °C, which is a mere 17 degrees hotter than the highest temperature recorded on Earth. It averages -63 °C on Mars, and while neither extreme would be pleasant for an unprotected human, both are manageable.

What’s more important, especially relative to Mars, is the amount of solar power available on Venus and the amount of protection that Venus has from radiation. The amount of radiation an astronaut would be exposed to in Venus’s atmosphere would be “about the same as if you were in Canada,” says Arney. On Mars, unshielded astronauts would be exposed to about 0.67 millisieverts per day, which is 40 times as much as on Earth, and they’d likely need to bury their habitats several meters beneath the surface to minimize exposure. As for solar power, proximity to the sun gets Venus 40 percent more than we get here on Earth, and 240 percent more than we’d see on Mars. Put all of these numbers together and as long as you don’t worry about having something under your feet, Jones points out, the upper atmosphere of Venus is “probably the most Earth-like environment that’s out there.”

It’s also important to note that Venus is often significantly closer to Earth than Mars is. Because of how the orbits of Venus and Earth align over time, a crewed mission to Venus would take a total of 440 days using existing or very near-term propulsion technology: 110 days out, a 30-day stay, and then 300 days back—with the option to abort and begin the trip back to Earth immediately after arrival. That sounds like a long time to spend in space, and it absolutely is. But getting to Mars and back using the same propulsive technology would involve more than 500 days in space at a minimum. A more realistic Mars mission would probably last anywhere from 650 to 900 days (or longer) due to the need to wait for a favorable orbital alignment for the return journey, which means that there’s no option to abort the mission and come home earlier: If anything went wrong, astronauts would have to just wait around on Mars until their return window opened.

HAVOC comprises a series of missions that would begin by sending a robot into the atmosphere of Venus to check things out. That would be followed up by a crewed mission to Venus orbit with a stay of 30 days, and then a mission that includes a 30-day atmospheric stay. Later missions would have a crew of two spend a year in the atmosphere, and eventually there would be a permanent human presence there in a floating cloud city.

The defining feature of these missions is the vehicle that will be doing the atmospheric exploring: a helium-filled, solar-powered airship. The robotic version would be 31 meters long (about half the size of the Goodyear blimp), while the crewed version would be nearly 130 meters long, or twice the size of a Boeing 747. The top of the airship would be covered with more than 1,000 square meters of solar panels, with a gondola slung underneath for instruments and, in the crewed version, a small habitat and the ascent vehicle that the astronauts would use to return to Venus’s orbit, and home.

Getting an airship to Venus is not a trivial task, and getting an airship to Venus with humans inside it is even more difficult. The crewed mission would involve a Venus orbit rendezvous, where the airship itself (folded up inside a spacecraft) would be sent to Venus ahead of time. Humans would follow in a transit vehicle (based on NASA’s Deep Space Habitat), linking up with the airship in Venus orbit.

Since there’s no surface to land on, the “landing” would be extreme, to say the least. “Traditionally, say if you’re going to Mars, you talk about ‘entry, descent, and landing,’ or EDL,” explains Arney. “Obviously, in our case, ‘landing’ would represent a significant failure of the mission, so instead we have ‘entry, descent, and inflation,’ or EDI.” The airship would enter the Venusian atmosphere inside an aeroshell at 7,200 meters per second. Over the next seven minutes, the aeroshell would decelerate to 450 m/s, and it would deploy a parachute to slow itself down further. At this point, things get crazy. The aeroshell would drop away, and the airship would begin to unfurl and inflate itself, while still dropping through the atmosphere at 100 m/s. As the airship got larger, its lift and drag would both increase to the point where the parachute became redundant. The parachute would be jettisoned, the airship would fully inflate, and (if everything had gone as it’s supposed to), it would gently float to a stop at 50 km above Venus’s surface.

Near the equator of Venus (where the atmosphere is most stable), winds move at about 100 meters per second, circling the planet in just 110 hours. Venus itself barely rotates, and one Venusian day takes longer than a Venusian year does. The slow day doesn’t really matter, however, because for all practical purposes the 110-hour wind circumnavigation becomes the length of one day/night cycle. The winds also veer north, so to stay on course, the airship would push south during the day, when solar energy is plentiful, and drift north when it needs to conserve power at night.

Meanwhile, the humans would be busy doing science from inside a small (21-cubic-meter) habitat, based on NASA’s existing Space Exploration Vehicle concept. There’s not much reason to perform extravehicular activities, so that won’t even be an option, potentially making things much simpler and safer (if a bit less exciting) than a trip to Mars.

The airship has a payload capacity of 70,000 kilograms. Of that, nearly 60,000 kg will be taken up by the ascent vehicle, a winged two-stage rocket slung below the airship. (If this looks familiar, it’s because it’s based on the much smaller Pegasus rocket, which is used to launch satellites into Earth orbit from beneath a carrier aircraft.) When it’s time to head home, the astronauts would get into a tiny capsule on the front of the rocket, drop from the airship, and then blast back into orbit. There, they’ll meet up with their transit vehicle and take it back to Earth orbit. The final stage is to rendezvous in Earth orbit with one final capsule (likely Orion), which the crew will use to make the return to Earth’s surface.

The HAVOC team believes that its concept offers a realistic target for crewed exploration in the near future, pending moderate technological advancements and support from NASA. Little about HAVOC is dependent on technology that isn’t near-term. The primary restriction that a crewed version of HAVOC would face is that in its current incarnation it depends on the massive Block IIB configuration of the Space Launch System, which may not be ready to fly until the late 2020s. Several proof-of-concept studies have already been completed. These include testing Teflon coating that can protect solar cells (and other materials) from the droplets of concentrated sulfuric acid that are found throughout Venus’s atmosphere and verifying that an airship with solar panels can be packed into an aeroshell and successfully inflated out of it, at least at 1/50 scale.

Many of the reasons that we’d want to go to Venus are identical to the reasons that we’d want to go to Mars, or anywhere else in the solar system, beginning with the desire to learn and explore. With the notable exception of the European Space Agency’s Venus Express orbiter, the second planet from the sun has been largely ignored since the 1980s, despite its proximity and potential for scientific discovery. HAVOC, Jones says, “would be characterizing the environment not only for eventual human missions but also to understand the planet and how it’s evolved and the runaway greenhouse effect and everything else that makes Venus so interesting.” If the airships bring small robotic landers with them, HAVOC would complete many if not most of the science objectives that NASA’s own Venus Exploration Analysis Group has been promoting for the past two decades.

“Venus has value as a destination in and of itself for exploration and colonization,” says Jones. “But it’s also complementary to current Mars plans.…There are things that you would need to do for a Mars mission, but we see a little easier path through Venus.” For example, in order to get to Mars, or anywhere else outside of the Earth-moon system, we’ll need experience with long-duration habitats, aerobraking and aerocapture, and carbon dioxide processing, among many other things. Arney continues: “If you did Venus first, you could get a leg up on advancing those technologies and those capabilities ahead of doing a human-scale Mars mission. It’s a chance to do a practice run, if you will, of going to Mars.”

It would take a substantial policy shift at NASA to put a crewed mission to Venus ahead of one to Mars, no matter how much sense it might make to take a serious look at HAVOC. But that in no way invalidates the overall concept for the mission, the importance of a crewed mission to Venus, or the vision of an eventual long-term human presence there in cities in the clouds. “If one does see humanity’s future as expanding beyond just Earth, in all likelihood, Venus is probably no worse than the second planet you might go to behind Mars,” says Arney. “Given that Venus’s upper atmosphere is a fairly hospitable destination, we think it can play a role in humanity’s future in space.”

SpaceX Returns U.S. Astronauts to Space

Post Syndicated from Stephen Cass original https://spectrum.ieee.org/tech-talk/aerospace/space-flight/spacex-returns-us-astronauts-to-space

With a “let’s light this candle,” and an ear-shattering roar and a blaze of light in Florida this afternoon, the United States rejoined an exclusive club of nations: those capable of launching people into space. Since the space shuttle fleet was decommissioned in 2011, American astronauts have had to hitch a ride on Russian Soyuz spacecraft. The launch today was the second attempt after the first attempt earlier this week was cancelled due to weather concerns. All went well, including a successful recovery of the the Falcon booster’s first stage, with a soft landing on the drone ship Of Course I Still Love You, stationed in the Atlantic.

This nine-year gap has highlighted how moribund the United States’ official space program has become: after all, between 1960 and 1969, NASA developed and flew three new crewed spacecraft—Gemini, the Apollo Command and Service Module, and the Lunar Lander, not to mention launch boosters such as the Saturn IB and Saturn V. But this return to human spaceflight marks more than just a return to the status quo, but heralds a new epoch when commercial, rather than government entities, take the lead in designing, delivering, and operating new spacecraft. The Dragon 2 spacecraft and Falcon 9 booster were both created by SpaceX, the current leader in the still nascent world of private spaceflight.

To be clear, NASA has always relied on commercial contractors to build most of its hardware. Gemini was built by McDonnell Aircraft (now absorbed into Boeing) for example, and each of the Saturn V’s three stages was built by a separate company—Boeing, North American (now part of Boeing), and Douglas (now also part of Boeing)—with the rocket’s instrumentation, telemetry, and computer module built by IBM. But during the Apollo era, NASA kept these contractors on a very tight leash, dictating many aspects of the design, and also had the advantage of vast budgets devoted to testing and debugging. NASA also exerted complete control of the entire flight from delivery of the hardware through launch and the subsequent mission.

But today, NASA’s took a back seat. While NASA’s mission control in Houston remains in charge of the overall mission to the International Space Station (ISS), SpaceX’s mission control in Hawthorne, California, was responsible for the launch and flight into orbit. The Dragon capsule won’t reach the ISS until tomorrow, when it will dock and essentially become part of the station until it is time for it to return.

The two astronauts flying onboard the Dragon—Robert Behnken and Douglas Hurley—are both veteran of the space shuttle program. SpaceX’s replacement is like the shuttle in that it is intended to be a largely resuable mode of transport, including a booster that can fly itself home to a safe landing, but the overall approach is more reminiscent of the Gemini spacecraft of the 1960s than anything since.

Few remember today, but the snub-nosed, matt-black-and-white Gemini spacecraft, with their stylish red trim, was originally designed with reusability in mind. Components were arranged to make servicing between flights easier, and a version was in the works to bring astronauts to and from a military space station, the Manned Orbiting Laboratory (MOL). The MOL was cancelled abruptly, and so only one refurbished Gemini capsule was ever reflown in an uncrewed test, and it’s planned role as reusable space station visitor largely forgotten.

Like Gemini, the Dragon 2 is comprised of two main components: a bell-shaped crew compartment with a curved heatshield and an unpressurized “trunk” section behind the heatshield that acts as both an adapter for mating the spacecraft to the launch rocket and provides additional payload space. Like Gemini, when returning to Earth, the unpressurized section is jettisoned, and the crew capsule alone makes a so-called “blunt body” descent through the atmosphere before releasing parachutes and splashing down in the ocean for pickup.

But the Dragon 2 also features enormous improvements. For one thing, it’s much bigger than Gemini, capable of carrying up to seven people, compared to Gemini’s two. The unpressurized section is also coated with solar cells to generate power, a first for U.S. crewed spacecraft, which previously relied exclusively on batteries or fuel cells. The crew capsule is also outfitted with rockets that are powerful enough for orbital maneuvering, while Gemini relied on thrusters in its disposable section. These rockets also mean that the crew capsule is capable of being its own launch escape system, pulling the crew the safety in the event of a booster failure. Gemini relied on two airplane-style ejector seats for launch emergencies, something that few astronauts seemed to have any confidence in.

The Dragon spacecraft also has a sophisticated autonomous guidance system: in theory, astronauts could just sit back at launch and let the spacecraft fly all the way into dock at the ISS. However, during this proving flight, the astronauts will take control of the spacecraft to test the manual backup controls, albeit in a much slicker manner than the old Gemini days, when Buzz Aldrin had to bust out a sextant to make a rendezvous after Gemini 12’s radar stopped working. The new system interface is more reminiscent of a video game than a piece of navigation equipment—in fact, you can try your own hand at space station docking using a replica of the interface online.

Exactly how long the crew will stay onboard the ISS is unknown, although there is a limit of 119 days due to concerns about the longevity of the Dragon’s solar panels in orbit.

What It’s Like to Sweat the Launch of a New Spaceship

Post Syndicated from James Oberg original https://spectrum.ieee.org/tech-talk/aerospace/space-flight/launch-new-spaceship-spacex-nasa-news-history

Much has been made of the long gap—nine years—since the last human space launch from U.S. soil. Soon, astronauts will fly again from Cape Canaveral. But there’s an even longer gap that hasn’t been mentioned, even though it’s probably much more significant for the success of today’s SpaceX launch.

It’s been almost forty years since the last time Americans flew on a completely new spacecraft. That was on 12 April 1981 with the space shuttle Columbia. Special preparation is always needed for this kind of first, as I remember well. I was in mission control with the ascent team, looking after the launch.

NASA Funds Project for Spacecraft That Make Make Their Own Landing Pads

Post Syndicated from Evan Ackerman original https://spectrum.ieee.org/tech-talk/aerospace/space-flight/nasa-landers-instant-landing-pads

Planetary landings are a messy business that can be dangerous for anything nearby, but they can also be risky for the landers themselves. Engine plumes can kick dust, dirt, and rocks back up towards the spacecraft, endangering engines, science payloads (this happened to a weather instrument on the Curiosity Mars rover), and potentially even astronauts.

We’ve managed so far because most unmanned probes, and even the Apollo lunar landers, have been light enough that their engine plumes have been relatively mild. But as we look towards scaling up our presence on the moon, we’re going to need rockets that are much, much bigger. NASA’s proposed Artemis landers will be somewhere between double and quadruple the mass of Apollo, and modeling suggests that one of these could displace something like 470 tons (!) of lunar soil during landing.

Through NASA’s Innovative Advanced Concepts (NAIC) program, the space agency is funding a creative new approach towards making planetary landings safer for large spacecraft. Masten Space Systems is developing a concept for “Instant Landing Pads,” where a spacecraft builds its own landing pad as it descends towards the surface. By not requiring landing pads to be constructed in advance, this technique would be safer, cheaper, and help us establish a base on the moon as quickly and efficiently as possible.

In all of the renderings of lunar landings that we’ve seen so far (from folks like Blue Origin, Boeing, SpaceX, and NASA itself), the landers themselves have touched down on the lunar surface directly, without a landing pad. It’s certainly possible to do this with large landers, if you’re choosy about where you land and add enough shielding to your vehicle for it to be able to withstand whatever it might kick up. And depending on the size and power of the engine (or engines) and the surface that they’re interacting with, this can be a lot of material—Masten has been doing some testing on Earth, and you can see how much of a problem this can be:

Finding the right landing location to avoid effects like this, and adding enough shielding to protect the lander, would be restrictive to any lunar program. Shielding is a significant amount of mass that takes away from payload, and if there’s no safe landing area near where you want your moon base to be, you’re out of luck.

The conventional solution is to send smaller landers first, and use local material to construct a landing pad. A project called PISCES is working on doing this with robots, for example. This could certainly work, but you’re adding months or years of lead time to your overall mission, and Masten estimates that it would cost over $100 million for every dedicated lunar pad building or preparation logistics mission.

What Masten wants to do instead is to put a pad, instantly, on a planetary surface underneath any rocket just a few seconds before landing. 

The system that Masten is developing with NIAC funding is called FAST, or in-Flight Alumina Spray Technique. Here’s how it would work: a few hundred meters above the surface of the moon (or Mars, or anywhere else you want to land), your lander comes to a hover. Alumina pellets are then fed into the engine exhaust nozzle, where they get partially melted in the engine plume and blasted down onto the surface. Most planetary surfaces that a spacecraft would be landing on are cold enough that the alumina cools and hardens on contact, and over the course of about 15 seconds, something like 300 kg of alumina gets layered into a totally functional landing pad. You then land as normal, ablating the pad a little bit but not digging a crater under yourself or blasting dirt and rocks all over the place. 

Masten has been testing rockets on Earth for years; their fleet of terrestrial test vehicles has accumulated more than 600 rocket powered landings (on landing pads). This idea came directly out of testing how rocket engine plumes kick up material, Masten Chief Engineer Matthew Kuhns tells us. “I started brainstorming ideas around ways you could land without needing a precursor mission to create landing pads. Lots of crazy ideas later, this one stood out.” 

NIAC is all about funding ideas that seem crazy, but that have enough technical feasibility that they could ultimately pay off.

“We will spend the next 9 months looking at how this would benefit the Artemis moon landings,” Kuhns says. “NIAC projects as a rule are very ambitious and usually 10+ years out to use, but in this case since we can build on a terrestrial technology I think we can move a bit faster.”

Masten will be teaming up with Honeybee Robotics to figure out exactly how engines can be modified to use FAST. FAST requires a system to transport the landing pad material into the engine, which is basically the opposite of a pneumatic sampling system that Honeybee has been working on. Testing is still to come, says Kuhns, but with Masten’s rocket experience, we’re hoping that moving “a bit faster” is a bit of an understatement.

We also asked Kuhns if he sees any problem with leaving these instant landing pads scattered about on the moon. “That would be a good problem to have,” he told us. “It would mean many many missions to the moon, a sustainable presence, and lots of science. Depending on their location and material, you could actually do science with the FAST landing pads and use them as laser or radio reflective arrays.” 

NIAC projects are typically funded through three different phases as their technology readiness level increases. A year from now, we hope to see these Instant Landing Pads make it to phase two, which will bring them that much closer to helping us return to the moon.

Galactic Energy Prepares Ceres-1 Rocket for First Launch

Post Syndicated from Andrew Jones original https://spectrum.ieee.org/tech-talk/aerospace/space-flight/galactic-energy-prepares-ceres1-rocket-first-launch

Galactic Energy, a low-key private Chinese rocket firm, celebrated its second birthday in February. That’s early days for a launch company, and yet the company is set to make its first attempt to reach orbit this June.

The rocket is named Ceres-1, after the largest body in the asteroid belt, and will launch from China’s Jiuquan Satellite Launch Center in the Gobi Desert. With three solid fuel stages and a liquid propellant fourth stage, it will be able to lift 350 kilograms of payload to an altitude of 200 kilometers in low Earth orbit.

The firm’s ability to move this quickly is due to a mix of factors—strong corporate leadership, an experienced team, and policy support from the Chinese state. 

Aerospace Companies Compete to Build Lunar Landers for NASA’s Project Artemis

Post Syndicated from Ned Potter original https://spectrum.ieee.org/tech-talk/aerospace/space-flight/aerospace-companies-compete-to-build-lunar-landers-for-nasas-project-artemis

After 50 years of lamenting that America had abandoned the moon, astronauts are in a rush again, trying to go back within five—and NASA has asked aerospace companies to design the lunar landers that will get them there. The project is called Artemis, and the agency is now reviewing proposals to build what it calls the Human Landing System, or HLS. In January, it says, it will probably select finalists.

NASA had said a landing was possible by 2028. Then, the White House said to do it by 2024.

“Urgency must be our watchword,” said U.S. Vice President Mike Pence when he announced the new deadline in March 2019. “Now, let’s get to work.”

Startup Tries to Revive Interest in Aerospike Rocket Engines

Post Syndicated from Rina Diane Caballar original https://spectrum.ieee.org/tech-talk/aerospace/space-flight/australian-startup-aims-to-change-the-course-of-aerospike-rocket-engines

Space fever is spreading on Earth. Plans for lunar habitats are underway, China recently completed a biological growth experiment on the moon, and the first all-woman space walk took place earlier this year.

NextAero, a startup based in Melbourne, Australia, wants to capitalize on this energy with its 3D-printed aerospike engines. Compared to conventional rocket engines with bell-shaped nozzles, aerospike engines have conical nozzles shaped like funnels that protrude from the engine—hence the spike.

Unlike Relativity Space, which can 3D print an entire rocket, NextAero’s focus is on building propulsion systems for small satellite launch vehicles. The small satellite market is set to become a US $15 billion industry by 2026, with growing demand for CubeSats in sectors such as agriculture, energy, defense, and communications.

4 Products That Make Sense to Manufacture in Orbit

Post Syndicated from Prachi Patel original https://spectrum.ieee.org/aerospace/space-flight/4-products-that-make-sense-to-manufacture-in-orbit

Space is open for business, and some entrepreneurs plan to make the final frontier into a manufacturing hub. There’s plenty of real estate. But it takes a few thousand dollars to launch a kilogram of stuff into space.

“The key question is: What is it that justifies the expense of doing these things in low Earth orbit?” says William Wagner, director of the University of Pittsburgh’s McGowan Institute for Regenerative Medicine, which will conduct biomedical research on the International Space Station (ISS).

Here are some technologies that might merit the “made in space” label.

  • Fiber-optic Cable

    Made from fluoride glass, a kind of fiber-optic cable called ZBLAN could have as little as one-tenth the signal loss of silica-based optical fibers.

    But quality ZBLAN fibers are hard to make on Earth. As the molten glass is stretched into fibers as thin as fishing line and then cooled, tiny crystals sometimes form, which can weaken signals. Microgravity suppresses the formation of these crystals, so fibers made in space would carry more data over longer distances.

    More data plus the need for fewer repeaters under the ocean would justify a higher price, says Austin Jordan of Made in Space, which plans to produce such fibers in space for terrestrial clients. “The math works. It would pay for itself and drive a profit,” he says.

    Two other companies, Fiber Optic Manufacturing in Space and Physical Optics Corp., also plan to make ZBLAN fibers in low Earth orbit.

  • Organs

    There are 120,000 people waiting for an organ transplant in the United States alone. “Most will never see one, there is such a shortage,” says Eugene Boland, chief scientist at Techshot, which wants to print human hearts in space.

    The heart, with its four empty chambers and highly organized muscle tissue made of different types of cells, is virtually impossible to print on the ground. On Earth, tissues printed with runny bioinks made of gel and human stem cells collapse under their own weight. Scientists must add toxic chemicals or a scaffold.

    Printing hearts and other organs in microgravity could be done using pure bioinks. “The cylindrical shape extruded from the nozzle is maintained, so you can build a more fragile 3D structure that would allow cells in the gels to secrete their own matrix and strengthen up,” says Wagner. And the printed layers fuse together without forming the striations seen in constructs printed on the ground, Boland says.

    Techshot, which is based in Greenville, Ind., is partnering with 3D-bioprinter manufacturer nScrypt. Their first bioprinter went to the ISS in July, but the small patch of heart muscle it printed didn’t survive reentry. The next mission, which launched in November, should result in thicker tissue that can be tested on Earth when it returns in January.

  • Metal Alloys

    Outer space is the perfect place to make metal alloys. Microgravity allows the metals and other elements to mix together more evenly.

    Magnesium alloys for medical implants have especially high potential. At half the weight of titanium alloys, magnesium alloys more closely match the density and strength of bone, and they harmlessly biodegrade in the body, says University of Pittsburgh bioengineering professor Prashant Kumta, who is working with Techshot to produce his patented alloys in a high-temperature furnace on the ISS.

    Making these alloys involves melting highly reactive magnesium with other elements such as calcium and zinc, keeping the melted materials in a vacuum for a long time so the elements mix evenly, and then cooling it all down.

    On Earth, impurities settle to the bottom, and the upper layer oxidizes to form an unusable skin. Both have to be thrown out. Even the usable middle layer has pores and pockets of unmixed elements and must be further processed to make a quality material. None of these problems occur when alloys are manufactured in microgravity.

  • Meat

    What Techshot and nScrypt want to do with human organs, Israeli food-tech startup Aleph Farms plans to do with meat. The two-year-old Rehovot-based company grows cultured beefsteaks that look and taste like the real thing. “While other companies use only muscle cell, we also grow connective tissue, blood vessels, and fat cells, which lets us make beefsteaks instead of patties,” says Yoav Reisler, external relations manager at the company.

    In September, the company teamed up with Russian company 3D Bioprinting Solutions to create the first tiny piece of meat on the ISS. It isn’t a huge technical advance, but it could feed astronauts on long-term crewed missions, as well as future space settlers as they set up a permanent base.

This article appears in the December 2019 print issue as “ 4 Products To Manufacture In Orbit.”

The World’s Largest 3D Metal Printer Is Churning Out Rockets

Post Syndicated from Bryce Salmi original https://spectrum.ieee.org/aerospace/space-flight/the-worlds-largest-3d-metal-printer-is-churning-out-rockets

I’ll never forget the first time I saw a rocket materialize before my eyes.

In October 2018, I stood in a small room and watched a massive robotic arm move elegantly around a large metal shape, which was rapidly growing larger as I gazed at it. The arm precisely deposited a stream of liquid aluminum to build up the structure, layer by layer, while two other arms waited, with finishing tools at the ready. I was standing in the Los Angeles headquarters of the upstart rocket company Relativity Space, staring in awe as a piece of its first launch vehicle, the Terran 1 rocket, came into existence.

I had only recently arrived at Relativity as the first engineer hired for its avionics department. Relativity offered quite a change of scenery from my prior jobs, even though the other companies I’d worked for also built rockets. But they did so in massive rooms, measuring thousands of square meters, enough to hold ranks of bulky manufacturing tools such as metal rollers, dome spinners, and friction-stir welding machines. At Relativity, though, most of the launch vehicle is built inside the small room where I was standing, which measures just 9 meters across.

The room contained Stargate, the largest metal 3D printer in the world. Relativity invented the Stargate printer for the audacious purpose of 3D printing an entire rocket that’s intended to fly to low Earth orbit. We hope our rockets will eventually fly even farther. Perhaps one day we’ll ship our 3D printers to Mars, so rockets can be constructed on the Red Planet. From there, who knows where they’ll go.

Does this sound crazy? Crazy ambitious, maybe. But plenty of people are taking our idea seriously. Four commercial customers have signed up for launches to Earth orbit beginning in early 2021. The U.S. Air Force has approved our request to build a launch site at Cape Canaveral, the famed Florida facility that launched many historic human spaceflight missions. And NASA has leased us a building at its Stennis Space Center, in Bay St. Louis, Miss., where Relativity will build a factory capable of turning out 24 rockets per year. Such mass production will represent a revolution in rocketry. By embracing additive manufacturing—that is, 3D printing—we believe we can pull it off.

Launching a rocket into orbit is a binary proposition: Either you succeed or you fail. During the roughly 10-minute flight from launchpad to space, a mind-boggling array of systems must work together perfectly—plumbing, avionics, software, pyrotechnics, and pneumatics, to name just a few. If any component fails, the whole endeavor can literally come crashing down.

The cost of a rocket is not determined by its raw materials; those are pretty cheap. It’s largely driven by the human labor needed to work those materials into usable components and verify that they will function for flight. There are two ways to reduce these labor costs: You can reduce the total number of parts in a rocket so less labor is needed, or you can change manufacturing processes to reduce the need for human minds and hands.

Blue Origin, SpaceX, and Virgin Orbit—companies that are leading the charge in the new commercial space sector—have tried a combination of these two methods to reduce labor costs. But these companies’ reliance on traditional “subtractive” manufacturing techniques, in which chunks of raw material are cut down and shaped, limits their options. The companies have automated much of their supply chains, yet they still have tens of thousands of parts to track through complex manufacturing systems. Automating the manufacturing process has reduced human labor, but it requires expensive customized tooling that matches the dimensions of a particular rocket.

Relativity approaches the labor challenge head on by leveraging additive manufacturing to print complex components, using a single operation to turn raw material into finished product. This approach dramatically reduces part count because one of our components is often the equivalent of dozens of small parts made via traditional manufacturing. Our process also relies on our 3D printers rather than fixed tooling, which enables us to be nimble and inventive. We can make large design changes with relatively little cost or time lost.

Rocketry operates on a different scale than other manufacturing sectors. Consider that the Volkswagen plant in Wolfsburg, Germany, turns out about 3,500 vehicles per day. In contrast, any aerospace company that could build 100 rockets in a year would be monumentally successful. What’s considered high-volume production in rocketry is relatively low-volume in other industries. That means that additive manufacturing can have a big impact on the industry. Because only dozens or hundreds of a particular part may be needed in a year, it doesn’t necessarily make sense to invest in highly optimized tooling to turn out that part in mass quantities—the tools might not pay for themselves before the part becomes obsolete.

Making a new part using a 3D printer requires little to no up-front cost. For example, one of our Stargate printers can produce a 2-meter-diameter propellant tank followed by a 3-meter-diameter tank with minimal downtime. Rather than having to retool an entire manufacturing facility to fabricate the next piece of hardware in the queue, we have to make only a few software-configuration changes.

Our company’s cofounders, Jordan Noone and Tim Ellis, met in college at the University of Southern California’s Rocket Propulsion Laboratory, in Los Angeles. Noone went on to work at SpaceX and Ellis at Blue Origin before they got back together and formed Relativity in 2015.

Both of their former companies use additive manufacturing to build some rocket components, but Noone and Ellis wanted to take the approach much further. They saw an opportunity to completely rethink how rockets are designed and manufactured. By simplifying designs and production processes, they figured, they would also simplify the mental labor, the “cognitive overhead,” involved in building a rocket.

Rockets typically have a huge number of individual parts: The space-shuttle system, for example, consisted of 2.5 million moving parts. All the pieces must fit together just right and can’t unexpectedly add up to an out-of-tolerance assembly. Every part must be manufactured, tested, installed, and tested again. More work ensues if a part needs to be fixed. And all these processes require engineers, technicians, tooling, and paperwork.

With additive manufacturing, you can design parts that incorporate several pieces that would traditionally be manufactured separately and assembled. Fewer parts means fewer interfaces and fewer chances for something to go wrong.

Our approach to designing and building our rocket engine is a case in point. Inside a typical rocket engine you’ll find an injector that mixes the fuel with the oxidizer as they enter the combustion chamber, where an igniter starts the fire. The combustion produces hot gas, which moves through a nozzle to create thrust. It sounds simple in principle, but the reality is staggeringly complex. Consider that Rocketdyne’s F-1 engine, which launched Saturn V rockets during NASA’s Apollo program, contained a combustion chamber and nozzle assembly composed of more than 5,000 individually manufactured parts (and that’s not including the injector).

Relativity’s engine, Aeon 1, is a different story. To build the engine, we employ commercial 3D printers that use a process called direct metal laser sintering, in which a laser fuses together particles of metal powder, creating the required structure layer by layer. The simplest variant of the engine, a pressure-fed version that uses pressurized gas to push the fuel and oxidizer from their tanks into the combustion chamber, is manufactured by pressing the printer’s on button three times (to print three parts). And we’re going further: We expect commercial printers to become available soon that will allow us to print the injector, igniter, combustion chamber, and nozzle as a single part.

We use that pressure-fed engine for development and testing; the engine that will eventually fly will use turbopumps instead of simple pressurized gas to move the fuel (liquid methane) and oxidizer (liquid oxygen). These turbopumps, which are better suited for rockets with large fuel tanks, will increase the part count, but the manufacturing process will still be vastly simpler than any before.

Many rocket engines use a technique called regenerative cooling, in which liquid fuel is pumped through cooling channels around the combustion chamber to suck heat away. In a traditional manufacturing and assembly process, a thick piece of copper is shaped by spinning it rapidly while applying pressure to form the inner contours of the combustion chamber. It is then milled to create intricate cooling channels on the outside. A strong outer jacket is then brazed onto the copper structure, and a fuel-inlet manifold is welded onto the outer jacket. The whole engine assembly requires finish machining to hold tight tolerances where things fit together. Each of these processes is an opportunity for design or manufacturing error. The Aeon engine also uses regenerative cooling, but its combustion chamber is created in a single print. What’s more, 3D printing enables us to incorporate many more tiny cooling channels than can be produced by milling the metal.

It’s normally a monumental task to get a single engine designed, fabricated, and on the test stand. This process takes 10 to 12 months using traditional methods. A major redesign takes almost as long. But we’re able to iterate much faster. In our initial tests of the Aeon engine, we tried out five versions within 14 months, firing the engines more than 100 times.

As NASA astronaut Donald Pettit explained in his brilliant article “The Tyranny of the Rocket Equation,” published on the NASA website, getting out of Earth’s gravity well is not an easy task. Rockets are largely empty vessels waiting to be filled with fuel. Pettit explains that 94 percent of the mass of a can of soda comes from the soda, and 6 percent from the can. The space shuttle’s external fuel tank was 96 percent fuel and 4 percent tank, an impressive improvement over soda-can technology when you consider that the fuel tank held cryogenic liquids that had to be pumped out at a rate of 1.5 metric tons of fuel per second.

The entire Terran 1 rocket is designed for simplicity. The tanks that hold the fuel and oxidizer are “autogenously pressurized,” which means a small percentage of vaporized fuel and oxidizer is pumped back into their respective tanks to replace the volume of liquid as it drains. To continue Pettit’s analogy, picture an unopened soda can, which is rigid and strong despite the thin shell of the can; once the can has been opened, though, it can be crushed with ease. Similarly, rockets use internal pressure to help create a lightweight yet strong vehicle.

These autogenous systems on Terran 1’s tanks eliminate the need for the special pressure vessel that many rockets use inside their fuel and oxidizer tanks. Those pressure vessels hold inert gases such as helium at extremely high pressures until they’re ready to be released into the tank to provide internal pressure. These vessels are notoriously difficult systems to engineer and manufacture and have been involved in several rocket failures in the last decade, including the explosion of a SpaceX Falcon 9 rocket in 2015.

Commercial printers that use metal laser sintering are suitable for manufacturing our engines, but they wouldn’t be practical for producing the tanks. Those printers work by selectively melting the desired portions of metal powder to create the solid material in each layer of a part. Because the powder bed needs to be flat and even for each layer, the entire work space of a printer must be filled with powder, regardless of how much material will actually be solidified. Most of that powder can be recycled, but some is lost on every print. Producing a tank using a laser sintering printer would require an unrealistic amount of metal powder and would be very slow.

That’s why we designed and built Stargate, our enormous 3D printer of a different kind. It uses an existing technique called directed energy deposition but operates at a scale never before seen. The printer feeds a metal wire into the deposition area and uses energy (typically a powerful laser) to melt the wire, building up printed parts layer by layer.

Stargate places molten metal only where it is needed to build the structure, which significantly cuts down on wasted material. It uses three massive robotic arms, one of which terminates in the printer head that feeds out the wire; the two others hold working tools for finishing the printed component. We also wrote proprietary software to manage the “path planning” involved in turning a design into detailed instructions for the robotic arms.

Stargate has a few limitations. Its robotic arms move its working tools through free space as it prints, which means the geometries that can be printed are constrained by the kinematics of the robotic arms—they can reach only so far and must avoid colliding with the printed structure. And as the wire melts, the bead size resulting from the welding process sets the minimum resolution of the print. But these restrictions aren’t serious when it comes to large pressure vessels and structural elements.

Our Stargate printer is a novel piece of technology, and we believe it opens up new frontiers in aerospace manufacturing. But the novelty of this printing process also means that we cannot rely on preexisting material data or process parameters to achieve high-quality products. Relativity has in-house metallurgists who are honing the process, ensuring that our components meet the strict quality standards for aerospace hardware.

In traditional aerospace manufacturing, a design change can require almost a year of retooling and adjustments. Because hardware changes take so long, the avionics department is usually the most agile part of an aerospace company. Avionics teams (which handle the electronics that manage the rocket’s guidance, navigation, communications, and more) are accustomed to implementing last-minute software changes to fix issues on other parts of the vehicle.

The situation is completely reversed at Relativity, where the hardware team can make substantial design changes and still produce a new tank or engine within days. They can revise their plans so quickly that they challenge the avionics team’s ability to produce printed circuit boards (PCBs) and construct the cable harnessing that connects all the electronics and wiring. Avionics has to adapt to an ever-changing and improving rocket.

That’s why we designed the avionics of the Terran 1 rocket to be as modular as possible. We assume that sensors and actuators will be changed, and so we designed the electronics in a way that would limit the impact of such modifications. To accomplish this feat we devised a few proprietary methods of busing, minimizing the number of connectors and pins. We make every effort to reduce the amount of harnessing, which is one of the least reliable parts of the avionics on a rocket—every connection of every wire is a potential failure point. Wherever possible, we use standards such as the Controller Area Network bus protocol (for enabling communication between microcontrollers and devices) and Ethernet, and thus can use existing industry tools for testing and development. This approach means we don’t waste time hunting for bugs in custom protocols and can instead focus on ensuring the proper operation of our avionics in their specific use cases.

As we consider each small design choice in the avionics systems, we aim for global rather than local optimization. For example, we use standard tools that automate electronics design, such as Altium Designer, to create basic spaceflight-qualified circuits that we can use in multiple ways throughout the rocket. We call these “bread and butter circuits,” and we use them in voltage converters, processors, sensor interfaces, and other components. When our engineers tackle a new problem, they build on the work that’s already been done, rather than starting from scratch. While this may sound like a commonsense approach, you’d be surprised at how many rockets contain a complicated assortment of circuit designs simply because different engineers solved the same problem in slightly different ways.

Another example can be found in our firmware. For internal communications within our avionics boxes, we don’t always use a protocol that’s optimized for PCBs, which would provide tiny benefits in performance and mass. Instead we sometimes use a protocol that we also use for external box-to-box communications. This method cuts the cost and time of firmware development considerably. What’s more, it gives us flexibility for our design solutions: We can make changes within a centralized box, or we can add on some last-minute sensor in the harnessing, but the software doesn’t know the difference. This approach may not be optimal for the avionics systems viewed in isolation, but it gives us many advantages elsewhere in regard to designing, building, and flying rockets.

Relativity CEO Ellis often reminds us that we should put at least as much thought into designing and producing our company’s culture as we do into designing and building our rocket. Relativity is focused on maintaining flexibility, so experimentation is encouraged. This attitude is antithetical to the culture of traditional aerospace companies, which try to lock down their designs as soon as possible. We have an aggressive goal—to launch Terran 1 by early 2021. So we leverage our modular approach to swap out pieces, and we’re constantly tweaking to optimize our designs for the world’s first 3D-printed rocket.

The Terran 1, which is about 30 meters tall and 2 meters wide, is intended to launch modestly sized satellites into low Earth orbit at a cost that is radically lower than competitors can offer. It will enable smaller companies to book the whole payload of a rocket and send it to their desired orbit on their own schedule, rather than having to piggyback on the flight of a bigger rocket whose destination orbit and schedule is controlled by another company.

Relativity Space may stumble, but with our emphasis on design and manufacturing flexibility we can afford to fail many times over. We learn from every failure and forge ahead. We’re watching the future of rocketry materialize before our eyes.

This article appears in the November 2019 print issue as “3D Printing a Rocket.”

About the Author

Bryce Salmi is the lead avionics hardware engineer for the Los Angeles aerospace startup Relativity Space.