Tag Archives: aerospace/space-flight

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.