An illustration of Mars surface operations with the Single-Person Spacecraft. Credit: Genesis Engineering Solutions
The idea of humans in spacesuits trying to walk on the tiny, potato-shaped Martian moon Phobos is not in the least bit practical.
With surface gravity roughly 2,000 times lower than that of Earth, “walking would be a real problem due to the low gravity. Even extremely slow steps would cause you to take huge leaps,” said Stephan Ulamec of the German Aerospace Center, DLR, who faced similar problems when his team landed the Philae spacecraft on a comet in 2014. Philae bounced, big time — but still took great pictures.
Happily, as delegates at AIAA’s ASCEND conference in Las Vegas learned on Thursday, a Boeing-led team has worked out one possible way that astronauts could explore the surface of Phobos without the gravitational hassle of effectively weighing around a mere 50 grams: inside the Single Person Spacecraft, a cylindrical extravehicular activity pod that’s being developed by Genesis Engineering of Maryland. The company has been developing the technology for the last decade, and it was optioned in 2021 for solo spacewalking excursions from Blue Origin’s Orbital Reef space station.
Defying Phobos’ low gravity by vectoring with its 16 nitrogen thrusters and equipped with arrays of dexterous robotic graspers and manipulators, the SPS could assist with any surface exploration and sampling operations, said Ben Donahue, principal investigator with Boeing’s Space Launch System applications research team in Huntsville, Alabama.
Donahue is interested in making spacewalks possible on Phobos because, as he said during his paper presentation, he is proposing that by 2035, NASA could launch a crewed, nuclear-powered mission to the moon involving at least four launches of its Space Launch System rockets. The idea is that the mission would establish an off-Mars “staging post” 6,000 km above Mars. There, the technologies for Mars surface exploration and communication for human missions on Mars itself could be more cost-effectively validated outside the planet’s gravity well and atmosphere.
“It’d be a base station for the future on Mars. One of its main purposes would be to validate the transportation and habitation components, so you don’t have to deal with all that on later missions to Mars’ surface,” Donahue told me by phone in a break between ASCEND sessions.
Multiple launches would be needed because Donahue and his co-authors want to mate together four separate components for a large Mars Transfer vehicle at the Earth-Moon Lagrange-2 point: two identical hydrogen and uranium-fueled nuclear-thermal propulsion stages; a long-duration crew habitat; a crewed Orion spacecraft and a small Earth reentry capsule.
Once mated, the Orion would be jettisoned, and the MTV sets off from the Lagrange point toward Mars.
After the nine-month outbound trip, the MTV would closely orbit Phobos, perhaps being anchored to it, and crews would have 600 days to complete their mission before embarking on the nine-month journey back to Earth, Donahue said. Astronauts would also embark on explorations of the Mars surface in SPS vehicles, gathering samples and teleoperating robots such as rovers’ helicopters and balloons. They would also establish Phobos as a telecommunications relay for future Mars missions.
Inside the SPS, an astronaut would breathe a normal oxygen and nitrogen mixture at regular air pressure and wouldn’t require a spacesuit — eliminating the time-consuming need to pre-breathe oxygen for many hours before any surface excursions.
This is the design’s chief advantage, said Donahue: “You can stay out longer, you can fly around and cover greater distances. It’s just an appropriate solution to this mission.”
Still, challenges remain, according to Ulamec of DLR. His team is readying its own Phobos mission: the IDEFIX rover that is to ride along on the Japan Aerospace Exploration Agency’s MMX sample return mission that’s set to launch in 2026.
“If you want to anchor a big spacecraft to Phobos, doing so is not trivial. How would it be done?” he asked.