Scientists have long tested Solar energy in space, but it could soon arrive on the moon – in the form of rovers equipped with solar panels. On unmanned lunar missions, these tiny robotic vehicles will test the limits of how humans advance their explorations, navigate the lunar surface, and create potential human habitats far from home.
The team behind it includes Mike Provenzano, director of planetary mobility at Astrobotic in Pittsburgh. As part of a NASA contract, the robotics company has planned unmanned missions to the moon with the rover in tow for the next year. The first mission, Peregrine 1, is scheduled for late 2021.
These trips will mark a major milestone in space: they will mark the first US visit to the moon in 50 years.
A light but powerful rover
The CubeRover is the smallest vehicle from Astrobotic and is similar in size to a microwave oven and weighs up to 5 pounds – and will include a solar panel mounted on its top. Their fleet also includes the slightly larger MoonRanger, which weighs around 24 pounds.
Once the rover reaches the moon, the team hopes the landing gear will pull it in Search for water ice near the south pole of the moon, says Provenzano. In recent years, scientists have found forms of water over the lunar surface.
Provenzano explains that CubeRover is modeled on the scalable miniature satellite CubeSAT, the developed 1999 (and inspired by Beanie baby packaging).
Since then, the CubeSAT has served as a standardized component for larger satellites made up of several cubic modules. Because of its size and shape, the CubeRover can carry payloads that are the same size as CubeSATs, he explains, so that space partners can plan larger loads based on the well-known CubeSAT unit. With this, the designers of the CubeRover hope to set a standard for the “lunar economy” and interplanetary freight delivery. (Watch a video NASA testing CubeRover mobility.)
Astrobotic wants the CubeRover to “democratize access to the moon, make it easier for commercial and academic groups to take part in these scientific missions” and design their own experiments for the lunar surface, says Provenzano. Partners on board Peregrine 1 will come from six countries, including DHL and the Mexican space agency, Mexican space agency.
Chuck Taylor, program manager for Vertical Solar Array Technology (VSAT) at NASA's Langley Research Center, began researching solar energy off-planet about seven years ago. It was a coincidence, he says. After working in the Navy in Systems Engineering, he joined the NASA Space Power Program. With its expertise in autonomous systems, the Langley Center leads NASA's solar energy efforts and works with solar cell experts at NASA's Glenn Research Center.
For the polar missions, Taylor considered placing large solar panels fairly high on masts to generate solar energy. In contrast to what is common on Earth, this would require vertically aligned solar panels.
The basic premise is that when you are at the South Pole, the angle of the sun is very low on the horizon, explains Taylor. Cliffs and other terrain features, or a nearby lander, could cast shadows over low, horizontal fields.
As soon as solar panels absorb energy, it can be stored in batteries or transferred to vehicles. This transmission is either over cable (“proven,” says Taylor) or newer methods, including Power rays with lasers.
Solar obstacles
It will be difficult to get the sight of sun-powered rovers speeding across the lunar surface (as in Ad Astra) into reality. One of the biggest roadblocks, Provenzano says, is the moon's extreme temperatures, which radiation on its surface and moondust.
But first the equipment has to get through the start. Solar panels are fragile and don't need to fall apart when the missile leaves Earth and later when the lander descends towards its target. Cedric Corpa de la Fuente, an avionics engineer on Astrobotic's Planetary Mobility team, is preparing to laboratory test a “structural model” – a replica of the solar panels – under starting vibration conditions to verify the rover's panels withstand.
The moonlit night is perhaps the biggest hurdle for rovers and panels. The dark side of the moon is brutal: a lunar day lasts 14 earth days, and during the lunar night the temperatures drop for two weeks, Downfall to minus 280 degrees Fahrenheit. In order for a rover to survive such severe cold, it has to store enough energy for continuous use during this long, dark period. The vehicle also needs enough power to run heaters, which help the devices weather the frost. And during the long lunar day, the panels have to withstand hotter temperatures than is possible anywhere on earth.
Then there is the dust. If lunar sand or regolith smeared the solar panels, it could reduce the stored energy and lead to overheating. Regolith consists of around 50 percent silicon dioxide and is highly abrasive. Provenzano advises that it can damage rover connections and seals and cause sparks in equipment.
When the pandemic restrictions eased this spring, testing at Astrobotic resumed to simulate the rover's navigation in such harsh moonlight and dust conditions. The teams monitor how dust affects the movement of the rover and its solar panel, and how the regolith glues the panels together.
Navigation poses another conundrum as rovers cannot rely on Google Maps or GPS like we do on earth road trips. During the landing, the lander's cameras take a series of photos to create a high-resolution map of the area around the location where it touches down. When the rover is deployed, it takes its own photos to aid orientation. Then software with stereo vision and visual odometry (the process of determining position and orientation by analyzing camera images) creates local maps that correlate with the high-resolution maps of the lander.
This navigation technique is something similar with that of the ancient Polynesians, who compared the movements of ocean currents and stars. The team will also track the position of the sun, Corpa de la Fuente adds, and they will cast laser patterns on the surface to create 3D surface maps.
Once on the moon, the rover needs enough juice to venture off the lander. For this reason, Astrobotic is developing a contactless docking station with WiBotic, a company that specializes in industrial and wireless charging underwater. With the smart docking software, a rover can independently find a charging hub and start charging as soon as it is within range.
The smallest rover should be able to be charged in just 90 minutes thanks to a 125 watt charging system and a battery the size of a battery. Rovers could charge themselves by forming an array, a concept known as “Swarm technology.”
They can also be supplied with accessories: the British company Spacebit has developed mini rover robots that fit in a CubeSat. Your Asagumo rover is a four-legged robot weighing about 2 pounds; they plan to start a demo on Peregrine 1 (see Video).
All in all, there is enough to keep the mission team busy. “There are so many ways a spaceship can die,” mumbles Provenzano. But the rover's potential is exciting. “If he finds water ice, he will be the first rover to ever find it on another planetary body. So we're super excited. ”
Unmanned lunar test drives can also provide lessons for adventure elsewhere in the solar system, including Earth. For example, wireless chargers adapted for the moon could be useful in “harsh radiation environments” like nuclear power plants, says Provenzano, where they can power sensors to monitor temperature and pressure more efficiently than traditional wired methods.