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NASA Testing Robots for Satellite Refueling Missions

Satellites aren't usually intended to be serviced, but NASA's robots can make it happen anyway

2 min read
NASA Testing Robots for Satellite Refueling Missions

The whole concept of servicing satellites in space is just so crazy that with the very rare exception of bajillion dollar pieces of hardware like Hubble, satellites just aren't designed to be repaired or refueled. They get put into orbit, they last until they run out of fuel or suffer some other sort of basic malfunction, and then they just get forgotten about, left to one of any number of depressing fates: orbiting the Earth until the end of time, de-orbiting whenever they feel like it onto hopefully not someone's head, or having a violently destructive close encounter with a fellow satellite resulting in a chain reaction of debris that will increase exponentially until low Earth orbit turns into a shell of pointy metallic confetti that's just as deadly as you'd expect pointy metallic confetti to be.

But what if we could service satellites, hmm? NASA's been taking small steps toward the giant leap of making that possible.

If you remember, DARPA has been exploring ways of hacking dead satellites to bits and reassembling them into zombies. As cool as that is, NASA isn't trying to do anything so, um, zombie-ish. Rather, they've been working for quite a while on putting all the pieces together that would be required to go up into space, find a satellite, and pump some extra fuel into it to keep it alive. The next-generation Canadarm was designed with this in mind, and DEXTRE has been practicing for a live robotic refueling mission, and the latest step is a teleoperated real fuel transfer test here on Earth:

When we said up at the top of this article that the concept of servicing satellites is crazy enough that they haven't been designed for it, we're talking about the fact that the fuel valves have been wired shut. So, getting access to these valves is one of the trickiest parts of the whole business. Fortunately, it's not something that has to be rushed, and so teleoperation (even teleoperation on a noticeable time delay) is a realistic way to go about it. Once the valve is open, a nasty chemical called nitrogen tetroxide gets pumped into the satellite's fuel tank at 300 PSI. It's highly toxic, but has the useful property that it's hypergolic when mixed with hydrazine, meaning that it will spontaneously combust without requiring an ignition source.

This particular test is just one very specific aspect of satellite servicing, but the principle being explored here goes far beyond simple fuel transfers, as NASA describes:

The servicing capabilities SSCO is developing could greatly expand options for government and commercial operators in the future, providing new ways to recover from anomalies or prolong the lifespans of their satellites. Technologies needed for servicing -- including autonomous rendezvous and docking systems, advanced robotic tools, and propellant transfer systems, among others -- can help the Agency on its path to extended human exploration, observatory servicing, the on-orbit assembly of large space structures, and perhaps even planetary defense.

[ NASA ]

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Robot with threads near a fallen branch

RoMan, the Army Research Laboratory's robotic manipulator, considers the best way to grasp and move a tree branch at the Adelphi Laboratory Center, in Maryland.

Evan Ackerman
LightGreen

This article is part of our special report on AI, “The Great AI Reckoning.

"I should probably not be standing this close," I think to myself, as the robot slowly approaches a large tree branch on the floor in front of me. It's not the size of the branch that makes me nervous—it's that the robot is operating autonomously, and that while I know what it's supposed to do, I'm not entirely sure what it will do. If everything works the way the roboticists at the U.S. Army Research Laboratory (ARL) in Adelphi, Md., expect, the robot will identify the branch, grasp it, and drag it out of the way. These folks know what they're doing, but I've spent enough time around robots that I take a small step backwards anyway.

The robot, named RoMan, for Robotic Manipulator, is about the size of a large lawn mower, with a tracked base that helps it handle most kinds of terrain. At the front, it has a squat torso equipped with cameras and depth sensors, as well as a pair of arms that were harvested from a prototype disaster-response robot originally developed at NASA's Jet Propulsion Laboratory for a DARPA robotics competition. RoMan's job today is roadway clearing, a multistep task that ARL wants the robot to complete as autonomously as possible. Instead of instructing the robot to grasp specific objects in specific ways and move them to specific places, the operators tell RoMan to "go clear a path." It's then up to the robot to make all the decisions necessary to achieve that objective.

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