NASA’s been working on robotic cave exploration for a long, long time, and Team CoSTAR (and the SubT Challenge) fit right in with that. The team and its robots have been spending some time in lava tubes, and we asked some folks from NASA JPL how it’s been going.
In 2017, a team at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., was in the process of prototyping some small autonomous robots capable of exploring caves and subsurface voids on the Moon, Mars, and Titan, Saturn’s largest moon. Our goal was the development of new technologies to help us solve one of humanity’s most significant questions: is there or has there been life beyond Earth?
The more we study the surfaces of planetary bodies in our solar system, the more we are compelled to voyage underground to seek answers to this question. Planetary subsurface voids are not only one of the most likely places to find both signs of life, past and present, but thanks to the shelter they provide, are also one of the main candidates for future human habitation. While we were working on various technologies for cave exploration at JPL, DARPA launched the latest in its series of Grand Challenges, the Subterranean Challenge, or SubT. Compared to earlier events that focused on on-road driving and humanoid robots in pre-defined disaster relief scenarios, the focus of SubT is the exploration of unknown and extreme underground environments. Even though SubT is about exploring such environments on Earth, we can use the competition as an analog to help us learn how to explore unknown environments on other planetary bodies.
Just how do you bring home pieces of asteroid? Carefully, that’s how, with grudging respect for the curveballs the asteroid can throw you.
Sixteen years after NASA’s OSIRIS-REx mission was first proposed and two years after the robotic spacecraft went into orbit around asteroid 101955 Bennu, mission team members are now counting down to the moment when it will descend to the surface, grab a sample—and then get out of there before anything can go wrong.
Though the mission plan has so far been executed almost flawlessly, an outsider might be forgiven for thinking there’s something a bit…well, counterintuitive about it. The spacecraft has no landing legs, because it will never actually land. Instead, the OSIRIS-REx spacecraft vaguely resembles an insect with a long snout—a honeybee, perhaps, hovering over a flower to pollinate it. The “snout” is actually an articulated arm with a 30.5 cm round collection chamber at the end. It’s called TAGSAM – short for Touch-And-Go Sample Acquisition Mechanism. You’ve doubtless heard the old expression, “I wouldn’t touch that with a 10-foot pole.” The TAGSAM arm is an 11-foot pole.
The TAGSAM collector will gently bump the surface—and then try to kick up some rock and dust with a blast of nitrogen gas from a small pressurized canister. If all goes well, at least 60 grams of dirt will be caught in the collection chamber in the 5 to 10 seconds before the spacecraft pulls away.
The mission was conceived in 2004 at the Lunar and Planetary Laboratory at the University of Arizona. It was rejected twice by NASA before it won approval in 2011. The spacecraft was launched in 2016, reached Bennu in 2018, and has surveyed it for two years. If Tuesday’s sample pickup is successful (if not, there are two backup nitrogen canisters), the ship will bring its cargo back in a sealed re-entry capsule for a parachute landing in the Utah desert on Sept. 24, 2023.
Think about that: nearly 20 years of work, seven years in space, US$800 million spent, and the moment of truth—actually touching the asteroid—will not even last a minute.
And all for just 60 grams? “That’s like a few sugar packets that you use for your coffee,” says Michael C. Moreau, the deputy project manager at NASA’s Goddard Space Flight Center in Maryland. But for scientists involved in the mission, that’s enough to conduct their experiments and put some aside for future research. Bennu, and other near-Earth asteroids like it, are interesting because they are rich in carbon, probably dating back 4.5 billion years to the formation of the solar system. Might they tell us about the origins of life on Earth? “We are now optimistic that we will collect and return a sample with organic material—a central goal of the OSIRIS-REx mission,” said Dante Lauretta, the OSIRIS-REx principal investigator at the University of Arizona, who has been on the mission team from the start.
Bennu is not a friendly place for a spacecraft, especially a robotic probe operating on its own 334 million km from Earth, far enough away that commands from mission managers take 18 minutes to reach it. The asteroid is a rough, rocky spheroid, about 500 meters in diameter, and it spins fairly rapidly: a “day” on Bennu is about 4.3 hours long. It’s probably not solid. Scientists call it a rubble pile, a cluster of dirt and rock held together by gravity and natural cohesion. And when Moreau says Bennu threw them “a bunch of curveballs,” some of them were literal—pieces of debris being flung out into space from the surface, though not enough to endanger OSIRIS-REx.
An asteroid the size of Bennu has almost no gravity to speak of: an object on the surface would weigh 8 one-millionths of what it would on Earth. That means staying in orbit around it is very delicate business. OSIRIS-REx’s orbital velocity has been on the order of 0.2 km/hr, which means a tortoise could outrun it. More important, it can easily be thrown off course by solar wind, or heating on the sunlit side of the spacecraft, or other miniscule forces. “Wow, a[n extra] millimeter per second three days later changes the position by hundreds of meters,” says Moreau.
Which is an error they can’t afford. Scientists thought Bennu would have a fine-grained surface, but were surprised when the spacecraft’s images showed a rugged, craggy place with house-sized boulders. They had hoped to pick a touchdown spot 50 m across. But the best they could find was a depression they nicknamed Nightingale, all of 8.2 m wide, with a jagged rock nearby that they call Mount Doom. OSIRIS-REx has a hazard map on board; if it appears off-target it will automatically abort at an altitude of 5 meters.
So there will be some nail-biting on Tuesday, but after 16 years on the project, Dante Lauretta said they’re as ready as they can be. “It’s transcendental,” he said, “when you reach a moment that you’ve devoted most of your career to.”
In July, NASA launched the most sophisticated rover the agency has ever built: Perseverance. https://mars.nasa.gov/mars2020/ Scheduled to land on Mars in February 2021, Perseverance will be able to perform unique research into the history of microbial life on Mars in large part due to its robotic arms. To achieve this robotic capability, NASA needed to call upon innovation-driven contractors to make such an engineering feat a reality.
One of the company’s that NASA enlisted to help develop Perseverance was ATI Industrial Automation. https://www.ati-ia.com/ NASA looked to have ATI adapt the company’s own Force/Torque Sensor to enable the robotic arm of Perseverance to operate in the environment of space. ATI Force/Torque sensors were initially developed to enable robots and automation systems to sense the forces applied while interacting with their environment in operating rooms or factory floors.
However, the environment of space presented unique engineering challenges for ATI’s Force/Torque Sensor. The extreme environment and the need for redundancy to ensure that any single failure wouldn’t compromise the sensor function were the key challenges the ATI engineers faced, according to Ian Stern, Force/Torque Sensor Product Manager at ATI. https://www.linkedin.com/in/ianhstern/
“ATI’s biggest technical challenge was developing the process and equipment needed to perform the testing at the environmental limits,” said Stern. “The challenges start when you consider the loads that the sensor sees during the launch of the Atlas 5 rocket from earth. The large G forces cause the tooling on the end of the sensor to generate some of the highest loads that the sensor sees over its life.”
Once on Mars the sensor must be able to accurately and reliably measure force/torques in temperatures ranging from -110° to +70° Celsius (C). This presents several challenges because of how acutely temperature influences the accuracy of force measurement devices. To meet these demands, ATI developed the capability to calibrate the sensors at -110°C. “This required a lot of specialized equipment for achieving these temperatures while making it safe for our engineers to perform the calibration process,” added Stern.
In addition to the harsh environment, redundancy strategies are critical for a sensor technology on a space mission. While downtime on the factory floor can be costly, a component failure on Mars can render the entire mission worthless since there are no opportunities for repairs.
This need for a completely reliable product meant that ATI engineers had to develop their sensor so that it was capable of detecting failures in its
measurements as well as accurately measuring forces and torques should there be multiple failures on the measurement signals. ATI developed a patented process for achieving this mechanical and electrical redundancy.
All of this effort to engineer a sensor for NASA’s Mars mission may enable a whole new generation of space exploration, but it’s also paying immediate dividends for ATI’s more terrestrial efforts in robotic sensors.
“The development of a sensor for the temperatures on Mars has helped us to develop and refine our process of temperature compensation,” said Stern. “This has benefits on the factory floor in compensating for thermal effects from tooling or the environment.”
Stern points out as an example of these new temperature compensation strategies a solution that was developed to address the heat produced by the motor mounted to a tool changer. This heat flux can cause undesirable output on the Force/Torque data, according to Stern.
“As a result of the Mars Rover project we now have several different processes to apply on our standard industrial sensors to mitigate the effects of temperature change,” said Stern.
The redundancy requirements translated into a prototype of a Standalone Safety Rated Force/Torque sensor capable of meeting Performance Level d (PL-d) safety requirements.
This type of sensor can actively check its health and provide extremely high-resolution data allowing a large, 500 kilogram payload robot handling automotive body parts to safely detect if a human finger was pinched.
ATI is also leveraging the work it did for Perseverance to inform some of its ongoing space projects. One particular project is for a NASA Tech demo that is targeting a moon rover for 2023, a future mars rovers and potential mission to Europa that would use sensors for drilling into ice.
Stern added: “The fundamental capability that we developed for the Perseverance Rover is scalable to different environments and different payloads for nearly any space application.”
For more information on ATI Industrial Automation please click here.
Can artificial intelligence help the search for life elsewhere in the solar system? NASA thinks the answer may be “yes”—and not just on Mars either.
A pilot AI system is now being tested for use on the ExoMars mission that is currently slated to launch in the summer or fall of 2022. The machine-learning algorithms being developed will help science teams decide how to test Martian soil samples to return only the most meaningful data.
For ExoMars, the AI system will only be used back on earth to analyze data gather by the ExoMars rover. But if the system proves to be as useful to the rovers as now suspected, a NASA mission to Saturn’s moon Titan (now scheduled for 2026 launch) could automate the scientific sleuthing process in the field. This mission will rely on the Dragonfly octocopter drone to fly from surface location to surface location through Titan’s dense atmosphere and drill for signs of life there.
The hunt for microbial life in another world’s soil, either as fossilized remnants or as present-day samples, is very challenging, says Eric Lyness, software lead of the NASA Goddard Planetary Environments Lab in Greenbelt, Md. There is of course no precedent to draw upon, because no one has yet succeeded in astrobiology’s holy grail quest.
But that doesn’t mean AI can’t provide substantial assistance. Lyness explained that for the past few years he’d been puzzling over how to automate portions of an exploratory mission’s geochemical investigation, wherever in the solar system the scientific craft may be.
Last year he decided to try machine learning. “So we got some interns,” he said. “People right out of college or in college, who have been studying machine learning. … And they did some amazing stuff. It turned into much more than we expected.” Lyness and his collaborators presented their scientific analysis algorithm at a geochemistry conference last month.
ExoMars’s rover—named Rosalind Franklin, after one of the co-discoverers of DNA—will be the first that can drill down to 2-meter depths, beyond where solar UV light might penetrate and kill any life forms. In other words, ExoMars will be the first Martian craft with the ability to reach soil depths where living soil bacteria could possibly be found.
“We could potentially find forms of life, microbes or other things like that,” Lyness said. However, he quickly added, very little conclusive evidence today exists to suggest that there’s present-day (microbial) life on Mars. (NASA’s Curiosity rover has sent back some inexplicable observations of both methane and molecular oxygen in the Martian atmosphere that could conceivably be a sign of microbial life forms, though non-biological processes could explain these anomalies too.)
Less controversially, the Rosalind Franklin rover’s drill could also turn up fossilized evidence of life in the Martian soil from earlier epochs when Mars was more hospitable.
NASA’s contribution to the joint Russian/European Space Agency ExoMars project is an instrument called a mass spectrometer that will be used to analyze soil samples from the drill cores. Here, Lyness said, is where AI could really provide a helping hand.
The spectrometer, which studies the mass distribution of ions in a sample of material, works by blasting the drilled soil sample with a laser and then mapping out the atomic masses of the various molecules and portions of molecules that the laser has liberated. The problem is any given mass spectrum could originate from any number of source compounds, minerals and components. Which always makes analyzing a mass spectrum a gigantic puzzle.
Lyness said his group is studying the mineral montmorillonite, a commonplace component of the Martian soil, to see the many ways it might reveal itself in a mass spectrum. Then his team sneaks in an organic compound with the montmorillonite sample to see how that changes the mass spectrometer output.
“It could take a long time to really break down a spectrum and understand why you’re seeing peaks at certain [masses] in the spectrum,” he said. “So anything you can do to point scientists into a direction that says, ‘Don’t worry, I know it’s not this kind of thing or that kind of thing,’ they can more quickly identify what’s in there.”
Lyness said the ExoMars mission will provide a fertile training ground for his team’s as-yet-unnamed AI algorithm. (He said he’s open to suggestions—though, please, no spoof Boaty McBoatface submissions need apply.)
Because the Dragonfly drone and possibly a future astrobiology mission to Jupiter’s moon Europa would be operating in much more hostile environments with much less opportunity for data transmission back and forth to Earth, automating a craft’s astrobiological exploration would be practically a requirement.
All of which points to a future in mid-2030s in which a nuclear-powered octocopter on a moon of Saturn flies from location to location to drill for evidence of life on this tantalizingly bio-possible world. And machine learning will help power the science.
“We should be researching how to make the science instruments smarter,” Lyness said. “If you can make it smarter at the source, especially for planetary exploration, it has huge payoffs.”
If ever there was life onMars, NASA’s Perseverance rover should be able to find signs of it. The rover, scheduled to launch from Kennedy Space Center, in Florida, in late July or early August, is designed to drill through rocks in an ancient lake bed and examine them for biosignatures, extract oxygen from the atmosphere, and collect soil samples that might someday be returned to Earth.
But to succeed at a Mars mission, you always need a little ingenuity; that’s literally what Perseverance is carrying. Bolted to the rover’s undercarriage is a small autonomous helicopter called Ingenuity. If all goes as planned, it will become the first aircraft to make a powered flight on another planet.
Flying a drone on Mars sounds simple, but it has been remarkably difficult to design a workable machine. Ingenuity’s worst enemy is the planet’s atmosphere, which is less than 1 percent as dense as Earth’s and can drop to –100 °C at night at the landing site.
“Imagine a breeze on Earth,” says Theodore Tzanetos, flight test conductor for the project at NASA’s Jet Propulsion Laboratory, in Pasadena, Calif. “Now imagine having 1 percent of that to bite into or grab onto for lift and control.” No earthly helicopter has ever flown in air that thin.
Perseverance and Ingenuity are set to land in a crater called Jezero on 18 February 2021 and then head off to explore. About 60 Martian days later, the rover should lower the drone to the ground, move about 100 meters away, and watch it take off.
While the car-size Perseverance has a mass of 1,025 kilograms, the drone is just 1.8 kg with a fuselage the size of a box of tissues. Ingenuity’s twin carbon-fiber rotors sit on top of one another and spin in opposite directions at about 2,400 rpm, five times as fast as most helicopter rotors on Earth. If they went any slower, the vehicle couldn’t get off the ground. Much faster and the outer edges of the rotors would approach supersonic speed, possibly causing shock waves and turbulence that would make the drone all but impossible to stabilize.
Ingenuity is intended as a technology demonstration. Mission managers say they hope to make up to five flights over a 30-day period. No flight is planned to last more than 90 seconds, reach altitudes of more than 10 meters, or span more than 300 meters from takeoff to landing.
“It may be a bit less maneuverable than a drone on Earth,” says Josh Ravich, the project’s mechanical engineering lead at JPL, “but it has to survive the rocket launch from Earth, the flight from Earth to Mars, entry, descent, and landing on the Martian surface, and the cold nights there.”
That’s why engineers struggled through years of design work, trying to meet competing needs for power, durability, maneuverability, and weight. Most of the drone’s power, supplied by a small solar panel above the rotors and stored in lithium-ion batteries, will be spent not on flying but on keeping the radio and guidance systems warm overnight. They considered insulating the electronics with aerogel, a super-lightweight foam, but decided even that would add too much weight. Modeling showed that the Martian atmosphere, which is mainly carbon dioxide, would supply some thermal buffering.
The team calculated that the best time of day for the first flight will be late in the Martian morning. By then, the light is strong enough to charge the batteries for brief hops. But if they wait longer, the sun’s warmth would also cause air to rise, thinning it at the surface and making it even more difficult to generate lift.
To see if the drone would fly at all, they put a test model in a three-story chamber filled with a simulated Martian atmosphere. A wire rig pulled up on it to simulate Mars’s 0.38-g gravity. It flew, but, says Ravich, the real test will be on Mars.
If Ingenuity succeeds, future missions could use drones as scouts to help rovers—and perhaps astronauts—explore hard-to-reach cliff sides and volcanoes. “We’ve only seen Mars from the surface or from orbit,” says Ravich. “In a 90-second flight, we can see hundreds of meters ahead.”
This article appears in the July 2020 print issue as “A Mars Helicopter Preps for Launch.”
China aims to become only the second country to land and operate a spacecraft on the surface of Mars (NASA was first witha pair of Viking landers in 1976 if you don’t count the former Soviet Union’s 1971 Mars 3 mission). With just a few months before launch, China is still keeping key mission details quiet. But we can discern a few points about where and how it will attempt a landing on the Red Planet from recent presentations and interviews.
In 2020, Earth and Mars will align. Every 26 months, a launch window for a low-energy “Hohmann” transfer orbit opens between the two. This July, no fewer than four missions are hoping to begin the nine-month journey.
A joint mission between the European Space Agency (ESA) and Roscosmos, the Russian space agency, ExoMars 2020 is dedicated to the search for life, including anything that might be alive today. A Russian-built lander is intended to carry a European rover to the Martian surface. But the mission is technically challenging, and some experts doubt that Roscosmos is up to its task. “They’re relying on a Russian-built lander, which is worrying,” says Emily Lakdawalla, a senior editor at the Planetary Society. “Russia has not launched a successful planetary mission since 1984.” ESA has also acknowledged that there’s some doubt about whether the mission will launch at all, as the parachutes that will be used during landing have run into problems during high-altitude testing.
Assuming the spacecraft does alight on the Martian soil, the lander, called Kazachok, will monitor the climate and probe for subsurface water at the landing location. Meanwhile the rover, named Rosalind Franklin, will go further afield. Rosalind Franklin is equipped with a drill that can penetrate up to 2 meters beneath the ground, where organic molecules are more likely to be preserved than on the harsh surface. An onboard laboratory will analyze samples and in particular look at the molecules’ “handedness.” Complex molecules typically come in “right-handed” and “left-handed” versions. Nonbiological chemical reactions involve both in equal measure, but biology as we know it strongly prefers either right- or left-handed molecules in any given metabolic reaction.
NASA’s mission will explore the Martian surface using substantially the same rover design as that of the plutonium-powered Curiosity, which has been trundling around the Gale crater since 2012. The big difference is in the payload. Mars 2020 has a suite of scientific instruments based on the premise that Mars was much warmer and wetter billions of years ago, and that life may have originated then. Mars 2020 will look for evidence of ancient habitable environments and for chemical signatures of any microbes that lived in them.
Mars 2020 is also a test bed, with two major prototype systems. The first is the Mars Oxygen In-Situ Resource Utilization Experiment [PDF], or MOXIE. About the size of a car battery, MOXIE converts the carbon dioxide atmosphere of Mars into oxygen using electrolysis. Demonstrating this technology, albeit on a small scale, is a critical step toward human exploration of Mars.
The other prototype is the Mars Helicopter, a solar-powered, 1.8-kilogram autonomous twin-rotor drone. To cope with the thin Martian atmosphere, the rotors will spin 10 times as fast as those of a helicopter on Earth. If it can successfully take off, it will be the first aircraft to fly on another world. Currently five flights are planned for distances of up to a few hundred meters. “It makes the [rover] engineers twitch a little bit to help to accommodate that kind of stuff, but it is awfully fun,” says Lakdawalla.
In 2011, the first attempt by the China National Space Administration (CNSA) to send a probe to Mars failed when the Russian rocket carrying it couldn’t get out of Earth orbit. So the Chinese are going with their own Long March rocket for their next try. The HX-1 mission will search for the signs of life with an orbiter and a small rover. The rover has been fitted with a ground-penetrating radar that should have a much deeper range—up to 100 meters—than similar radars on ExoMars and Mars 2020, which can reach only a few meters down.
Although technical details about the mission are sparse, the CNSA has momentum behind it. “It’s really astonishing what they have accomplished with their lunar missions,” says Lakdawalla. She’s impressed that the Chinese engineers succeeded in depositing a lander and rover on the moon’s surface in 2013 “on their first-ever effort to land on another world.” Such success bodes well for Mars, she says: “They’ve clearly demonstrated technical capability and interplanetary navigation.”
Despite the UAE’s inexperience, its chances of entering the Mars club aren’t bad, explains Lakdawalla. “It is just an orbiter, so I think success on the first try is a lot easier, given how routine it’s become to put things in orbit,” she says. Lakdawalla notes that the UAE has excellent international partnerships, and says the new space agency isn’t focused on doing all of the technology development itself: “The UAE is about hiring the best consultants and getting help to leapfrog their own technology.”
This article appears in the January 2020 print issue as “Life on Mars?”
It will be China’s first independent attempt at an interplanetary mission, and comes with two ambitious goals. Launching in 2020, China’s Mars mission will attempt to put a probe in orbit around Mars and, separately, land a rover on the red planet.
The mission was approved in early 2016 but updates have few and far between. Last week, a terse update (available here in Chinese) from the Xi’an Aerospace Propulsion Institute, a subsidiary of CASC, China’s main space contractor, revealed that the spacecraft’s propulsion system had passed all necessary tests.
According to the report, the Shanghai Institute of Space Propulsion has completed tests of the spacecraft’s propulsion system for the hovering, hazard avoidance, slow-down, and landing stages of a Mars landing attempt. The successful tests verified the performance and control of the propulsion system, in which one engine producing 7,500 Newtons of thrust will provide the majority of force required to decelerate the spacecraft for landing.
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