If all goes according to plan, Hamid Hemmati's plan will fall flat.
Hemmati is the project lead on the Two Dimensional Planetary Surface Landers, a NASA Innovative Advanced Concepts (NIAC) project that is in the planning stages. These flat probes would resemble solar panels, but with a flexible electronic body. Each lander would be less than a half inch thick and just over three feet on each side—small enough you could stack 10 to an orbiter. Sensors on board the probe would scan the terrain of a moon or planet below, giving insight into places no NASA lander has dared go. And then these two-dimensional explorers could deploy to the surface, providing a cheap way to reach some of the most difficult terrain in the solar system.
"The most geologically interesting places are also the most hazardous to land," Hemmati says, "so typically NASA and ESA [the European Space Agency] don't dare go to these places, because it doesn't look good if you lose a half a billion dollar lander."
The idea came to Hemmati at a conference on Mars. In presentation after presentation, something kept coming into his mind.
"The main thing that bothered me in all those presentations is that these were one-shot deals," he said. "If you lose it during landing you're done. So I was thinking of what could be done to have multiple landers at the same time, and simplify the process so that you don't have to have all these sophisticated landing schemes with multiple radars."
Cost is a big factor in rovers. The Mars Science Laboratory (Curiosity) has a projected lifetime cost of over $1 billion, which is why the one-shot sky crane landing was so harrowing. Send lots of small rovers, however, and the mission could succeed even if half of them crash.
Cheaper, disposable landers can visit extreme locales where a pricier bot would fear to tread. Think the lakeshore muds of Titan, the Valis Marinaris canyons on Mars, or the ice geysers of Europa.
"There's quite a bit of interest from the science community to land [on Europa], but there's quite a bit of hesitation still because the surface is unknown, if it's just ice or some other thing, so it's deemed too risky to just send a expensive spacecraft," Hemmadi says.
You can do a lot with a little lander. Onboard instruments could analyze soil. Gas-sensing films, cameras, weather monitors, seismometers, and magnetic field sensors can fit onto the flat surface of the lander to maximize its scientific payload. The flat rovers could stream data via UHF back to their orbiter mothership, which could relay it home to Earth. Hemmati says the rovers could also be equipped with legs that allow them to hook into the surface. That would allow them to stay in place at a location such as a comet, asteroid, or the moons of Mars, which have lower gravity than a planet.
Hemmati and his team have begun work on prototypes using off-the-shelf goods. But there are obstacles ahead before the landers are ready to drop.
Consider the issue of power. Because the expanses of the Solar System get much colder and darker the further you venture out from the sun, most probes must to be equipped with ways to stay warm. Usually, this is done through radioactive elements like iridium or plutonium that burn in Radioisotope Heater Units (RHUs.) But for compact two dimensional landers, that may not be an option, and no battery yet exists that can handle extreme cold without quickly losing life, absent a radioactive element.
For missions to the Moon or Mars, there's an easy workaround: solar power via panels on the sun-facing side of the spacecraft. But for deep solar system exploration, that's not an option. Without better batteries, flat rovers won't be able to visit Jupiter or beyond.
Then there are the sensors and other payload options. Tiny rovers need tiny components. But for some of the most useful science instruments, like a spectrometer, the technology to downsize just isn't there.
"There's no miniature mass spectrometer that I can put on there," Hemmati says, "but you can have 3D imaging, videos, cameras and all kinds of instruments to measure the fields, the temperature, and seismology."
His team must conquer those challenges if 2D landers are to visit the far reaches of the solar system. But even without those breakthrough innovations, the landers could be useful much closer to home. Hemmati said that miniature versions could travel to areas where helicopters or people can't or shouldn't go, including disaster areas or active volcanoes. They could gather data without endangering human lives.
And perhaps those Earthly visits will prepare the landers for some extraterrestrial journeys.
"It could be anywhere. It could be a comet, it could be an asteroid, it could be a planet, it could be a moon of a planet," Hemmadi says. "There are various interesting places to go, and each one of them has very different challenges."