Getting to Mars is only half the battle, the return trip requires a lot of moxie
It seems inevitable that humans will some day journey to Mars. The current goal, according to NASA estimates, is to achieve the feat by 2040. Getting there, however, will require a lot of doing.
“A trip to Mars is an order of magnitude more ambitious than anything we’ve done before,” notes Jeffrey Hoffman, a former astronaut who logged five missions aboard the Space Shuttle. “Not only from a technical standpoint, but also when it comes to the health and psychology factors of being confined in tight quarters so far from home.”
For starters, it’s a really long way to go. The average distance between Earth and Mars, depending on their orbits, is 140 million miles (225 million km). During the trip, astronauts also would be exposed to a constant barrage of radiation (as much as 700 times the levels on Earth).
And reaching Mars is only half the battle. Once a crew has landed, provisions not only have to be made for sustaining life during their stay on the planet, but precise plans also need to be in place to ensure a successful return trip home.
In addition to being a breath of fresh air, oxygen is a big part of rocket fuel propellant—space travel literally requires tons of the chemical. Getting four astronauts off the Martian surface, for example, would require about 15,000 lbs (7 metric tons) of rocket fuel and 55,000 lbs (25 metric tons) of oxygen. By comparison, astronauts living and working on Mars would require far less oxygen to breathe, according to NASA.
Needless to say, transporting that much oxygen—in addition to what’s needed to leave the Earth’s atmosphere and maneuver in space—isn’t practical. The alternative is to make use of local resources to produce oxygen on Mars and fuel the trip back home.
“It’s called in situ resource utilization, which basically means living off the land,” Hoffman explains, noting that explorers having been doing this on Earth forever. “When early sailors came across an island, they’d stock up on food and other supplies so they didn’t have to bring everything with them. It’s the same concept in space. While we can’t make clothes there, oxygen is another story.”
And that’s exactly what Hoffman, as part of a joint effort between NASA and the Massachusetts Institute of Technology (MIT), has been testing for the last few years—both on Earth and Mars. Hoffman is a professor in MIT’s Department of Aeronautics and Astronautics and the director of the university’s Human Systems Lab.
As part of NASA’s 2021 mission to Mars, the Perseverance rover has been diligently exploring the red planet’s surface, searching for signs of ancient life, collecting geological and climate data, and putting new technologies to work. This includes the Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE).
The device, which is about the size of a bread box, was first tested April 20, 2021, 60 Martian days (sols) after it landed. Since then, MOXIE has been repeatedly tested under various conditions, times of day and seasons of the year to ensure it will function as intended whenever needed.
How does it work? Unlike the Moon, Mars has a thin atmosphere. “It’s about 1% the density of the Earth’s atmosphere at sea level—like being at 100,000 feet,” says Hoffman, who also serves as MOXIE deputy principal investigator. “But it’s almost pure, 96%, carbon dioxide (CO₂).”
Martian air is drawn in through a filter that decontaminates it. Next, the air is pressurized and sent through a Solid OXide Electrolyzer (SOXE). Developed by OxEon Energy, SOXE electrochemically separates oxygen from CO₂ molecules, which consist of one carbon atom and two oxygen atoms. Carbon monoxide waste is emitted into the Martian atmosphere.
To handle temperatures up to 1,470° F (800° C) during the conversion process, the MOXIE unit is made with heat-tolerant materials. These include 3D-printed nickel-alloy parts, which heat and cool the gases flowing through it, and a lightweight aerogel that helps hold in the heat. A thin gold coating on the outside reflects infrared heat, according to NASA, keeping it from radiating outward and potentially damaging other parts of Perseverance.
During the Mars experiments, which concluded in August, MOXIE generated a peak of 12 grams of oxygen per hour and a total of 122 g over 16 demonstrations, which is about what a small dog breathes in 10 hours. Researchers also have been testing the technology on Earth.
“The demonstrations have worked brilliantly,” Hoffman enthuses. “In fact, we’ve essentially satisfied all of our scientific requirements. Now it’s a matter of analyzing all the data accumulated over the last few years. And we’ll need to liquefy the oxygen for use as a propellant.”
The MOXIE aboard Perseverance is said to be the first demonstration of chemically transforming resources on the surface of another planet that could be used for a human mission. In the future, a scaled-up version of the technology operating on Mars could produce enough oxygen to help support human visitors, and to fuel rockets returning to Earth.
While a manned mission to Mars likely is still nearly two decades away, NASA is ramping up efforts to return to the Moon. After more than 50 years (December 1972), mankind could walk on the surface again as soon as 2026.
There are a lot of good reasons for another lunar expedition, according to Hoffman. “We have to get back and learn how to operate on the surface of another planetary body, and many of the things we’ll be doing will help us when we eventually go to Mars.”
The moon also is a great cosmic study guide. “It has captured the history of our solar system in a way that Earth’s surface doesn’t, because the Earth is constantly changing from erosion and continental drift,” Hoffman explains. “The moon is pretty much like it was 4.5 billion years ago; it’s very interesting for scientific reasons.”
And it has resources that could potentially be used on Earth, such as a large amount of water believed to be near the moon’s south pole. “If you can use that water and electrolyze it, you can create hydrogen and oxygen that can then be used as rocket fuel,” Hoffman says.
He also lists the potential to mine heavy metals—including silver and gold—and rare earth elements deposited by asteroids, as reasons to land on the moon. The Moon also could provide a good base to generate solar power, and there’s the potential to eventually use it as a production base. Although cautioning that manufacturing in space likely will come about slowly, Hoffman notes that 3D printing is opening new avenues for MRO-type applications if something breaks or needs to be replaced.
As for a manned mission to Mars, Hoffman concedes a lot of advances need to happen before liftoff. Chief among them is cutting travel time. To this end, NASA is partnering with the U.S. Defense Advanced Research Projects Agency to develop a rocket that uses nuclear propulsion, which Hoffman says is promising. But he views advanced electric plasma power as a better long-term solution.
At this point, Hoffman holds no illusions that he’ll ever make it to Mars. But he’s gratified that one of the last projects he worked on in his scientific career demonstrates the process that ultimately will help next-generation astronauts get there—and even take a breath of oxygen. Talk about a great origin story.
It’s not often that you get to talk to a real astronaut. So, naturally, Manufacturing Engineering (ME) Lead Editor Steve Plumb jumped at the chance to speak with Jeffrey Hoffman, a retired astronaut who was part of NASA’s inaugural Space Shuttle team, who is now a professor of aeronautics and astronautics at MIT. An edited version of their conversation follows:
ME: Have you always been interested in space travel?
Hoffman: I grew up in the 1950s at the dawn of the Space Age, and, even before Sputnik, the newspapers, magazines and television shows were full of talk about going to the moon and science fiction. My childhood heroes, before there were real astronauts, were Flash Gordon, Buck Rogers and Tom Corbett. I continued to be fascinated by the topic, and actually did my doctorate in high-energy astrophysics, looking at X-rays and gamma rays from space.
ME: How did you eventually become an astronaut?
Hoffman: I was working as an astrophysicist at MIT in the late ‘70s when NASA developed the Space Shuttle and began looking for new astronauts. The Shuttle, which had a crew of seven, only needed two pilots. That’s what really opened things up for scientists, engineers and medical doctors. I was lucky enough to get accepted in the first group of Space Shuttle astronauts in 1978.
ME: What’s it like to go up and live in space?
Hoffman: Well, it was every bit as incredible as I thought it would be. The launch is pure excitement, with an unbelievable amount of power. You’re sitting on top of four and a half million pounds of high explosives, and the idea is to release all that energy in a controlled way. There’s a lot of shaking and vibration, but it’s all over in less than nine minutes, then everything gets quiet and you start floating. It’s totally different in so many ways from any experience you’ve ever had before.
ME: You’ve spent more than 50 days in space in the course of five missions. Any special highlight?
Hoffmann: The most significant thing I did as an astronaut was fixing the Hubble Space Telescope. I was one of the space-suited astronauts who went out in December of 1993 and fixed the optics that have provided such extraordinary images of the universe. To put my hands on the Hubble Space Telescope up in space and actually fix it, that was a real thrill.
ME: The view has to be spectacular, right?
Hoffman: It’s something I never got tired of, seeing the Earth from that perspective. At the same time, when you look out the window, you realize that most of the universe is completely hostile to life, and you’d quickly die outside the shuttle. Then you look down at this beautiful blue-green planet and realize what our home provides us—life.
ME: It sounds like a truly life-altering, profound experience?
Hoffman: As an astronaut, you’re in a spacecraft, which is a totally closed system and depends on systems for producing clean water and oxygen to breathe. Then you realize that’s what the Earth is doing for us, but humanity has not dealt with the fact that the Earth is finite. The fact that we can see from a cosmic perspective the damage we’re doing is pretty scary. It’s an incredible planet, and many astronauts come back with a better sense of the need to protect it.
ME: If you had an opportunity to go back to space, especially if it was on a mission to Mars, would you do it?
Hoffman: Oh, I’d go in a in a heartbeat. I volunteered to go up to the Mir and the International Space Station, but the transportation at the time was in the Russian Soyuz, and I’m about three inches too tall to fit. They’ve made the Soyuz a little bigger now, but it was too late for me by then. I’m now one year older (78) than John Glenn was when he last flew (in 1998). So, send me in coach. It’s just an extraordinary experience.
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