NASA's Top 5 Technical Challenges Countdown: #5: High-Powered Robotics
In this series we are exploring NASA's top five challenges as detailed in its Civil Space Shortfall Ranking, which is basically NASA's Christmas wish list. These are the technologies that NASA believes we need to develop if we want to go to space…and stay there.
And we'll start with number five: high-powered robotics.
Space is hard. There's no doubt about that. It's completely unlike any environment we have ever faced on the Earth. Explorers in space, whether human or robotic, have to tackle literally out-of-this-world challenges. For example, there are extreme temperature fluctuations. One minute it could be hot enough to boil water, and the next minute cold enough to freeze nitrogen. Without thick atmospheres to balance and distribute heat, within the inner solar system you're at the mercy of the Sun: if you're in sunlight, it's generally going to be too warm, and if you're in the shade, it's hundreds of degrees colder. In the outer solar system? It's just...cold. Always, miserably cold.
And then there's the dust. On the Earth, dust is irritating – it makes us sneeze and it can jam up gears or wheels or cause your breaks to make that loud SQUEEEL sound. But in space dust is next-level. The surface of the Moon is covered in a fine powder, regolith, that is both tiny and, microscopically, fully of tiny, jagged edges. This dust can worm itself through even our best-sealed compartments, or just get carried along for the ride – where it immediately just sticks to everything.
And hey, who doesn't love a dose of deadly radiation every single second of every single day? Without a protective magnetic field and the security blanket of a nice thick atmosphere, operations on the Moon and Mars require constant exposure to cosmic rays, tiny charged particles slamming through the universe. Cosmic rays are caused by super-energetic events like supernovae and active galactic nuclei, and a typical cosmic ray particle is traveling somewhere around 99.999999% the speed of light. That's a lot of nines, and a lot of trouble. These cosmic rays can fry electronics and snip apart DNA.
And yeah, we've been sending robots into this extreme environment for decades, but if we want a more permanent presence on the Moon and Mars, we have to do better. For sure, we've had some huge successes, like the Cassini mission that spent 13 years in orbit around Saturn, or the Mars Exploration Rovers – Spirit and Opportunity – which lasted years longer than their planned 90-day missions. Those missions produced an enormous amount of science results, like the fact that we now have firm evidence that liquid water once existed on the Martian surface. We have been able to gather this evidence with the instruments on our rovers like rock abrasion tools and alpha particle X-ray spectrometer, in addition to a good old-fashioned camera.
But the presence of liquid water in the Martian past has opened up a powerful, difficult question: did Mars once harbor life? Unfortunately our current suite of robotic instruments are too limited to tell us. We need to be able to dig deeper into the soil, survey more regions, and bring more powerful instruments to answer that burning question.
This isn't just limited to Mars rovers. In general, every robot we send into space has a limited lifespan, is not meant to be repaired, and is extremely limited in what it can do. And still, those missions cost hundreds of millions, or even billions, of dollars, because we're trying to battle all those hostile environmental factors.
On the Earth, we've made great strides in making larger and more powerful robots. We have heavy-duty robots that assemble cars, and we have versatile ones that can walk like humans.
To make more impressive robots, designers have focused on increasing the power density: the amount of energy that robots can store and send through their various parts and systems. These systems include sensing, actuation (moving various bits and parts around), and aviation (like flight control). The more power you have available to all these systems, the more you can do. But if we rank power density on a scale, like a wind-up toy being a 1 and a Kaiju-killing Jaeger a 10, our robotic space probes are like a…3. Maybe 4 if we're being generous.
It's not just about having a big battery pack or solar cell. We need the ability to get this power to a robot's subsystems. We need more powerful electric motors, gearing, and drive train components. We need more capable sensors, with more dynamic range, more perception, more force. We need long-lived power distribution systems; you know, like cables and wires. We need more powerful computers to drive this all.
And, if this weren't enough, we need future robots to be modular, so that we can easily swap out components to allow the robot to fulfill a new mission objective, and we need our robots to be repairable and maintainable, because we simply can't build up a healthy lunar or Martian infrastructure with single-shot craft.
In fact, we probably need space-based robots that are even more capable and more power-dense than their current terrestrial cousins. Meaning that our goal isn't just to make current top-of-the-line Earth robots capable of facing the dangers and challenges of space environments. No, we need EVEN BETTER.
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