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Space salvage to enter the robotic age
tom gauld
46 | NewScientist | 10 November 2012
Save our satellite When things go wrong in space, there’s no easy way to fix them, says Maggie McKee. But that’s about to change
R
USSIAN roulette was nothing compared to this. The 2-tonne satellite was screaming toward Earth, and most of it was expected to survive the rigours of re-entry. If it stayed aloft another 10 minutes parts of the defunct German X-ray satellite could smash into Beijing. It was pure luck that prevented disaster. Thanks to the craft’s orientation and the density of the atmosphere at the time, it missed China altogether and splashed down safely last year in the Bay of Bengal. Thankfully, such situations are rare, yet things do go wrong in space. Each year about one satellite is launched into the wrong orbit or is unable to deploy a crucial component, hobbling it at the beginning of its life. Others die because they’ve run out of fuel, cutting short their careers. What if there was a way to save satellites that go wrong? Not only could we wring more out of the hundreds of billions of dollars of equipment above our heads, we could ensure the safety of neighbouring satellites, which risk getting smashed up unless they blast themselves out of the way. Seeing this promise, a number of organisations around the world are now working to create robots that could go into orbit and service wonky satellites and other spacecraft. One day they could behave like real-life Wall-Es, scavenging the parts they need from orbital junkyards to build new craft. Eventually, the same technologies could build things in orbit that are too large to be launched in a single rocket, such as
vast telescopes or spacecraft bound for Mars. Robotic space repair has a long pedigree – in fiction. “You can find lots of that in science fiction all the way back to the 1950s before the first satellites were launched,” says Scott Pace, of the Space Policy Institute at George Washington University in Washington DC. But so far, all the work has been done by real live astronauts. Satellite repairs, like DIY projects on Earth, rarely go off without a hitch, and humans are adept at changing tactics on the fly. For example, on the final servicing mission to the Hubble Space Telescope in 2009, spacewalking astronauts had trouble loosening a bolt on a handrail they needed to remove to access a failed circuit board. “In the end, the astronaut just bent the handle back and forth until it finally broke off,” says Jeffrey Hoffman of the Massachusetts Institute of Technology, who as a NASA astronaut serviced Hubble in 1993.
Grunt work “That’s the sort of thing that would be very hard for a robot,” he says, since robots can only do what they have been explicitly designed, built and programmed to do. Along with five Hubble servicing missions, astronauts have fixed several commercial satellites from the space shuttle, not to mention doing the bulk of the construction work on the $100-billion International Space Station (ISS). However, after the Columbia space shuttle disaster of 2003, sending humans hundreds of kilometres into space to do repairs began
to seem overly risky, and NASA started to look more seriously into robotic repairs. Significant advances over the past 10 years mean such robots are starting to become reality. The easiest job will be inspection – flying around a craft looking for damage from micrometeorites or space debris. An autonomous spacecraft could help identify a damaged satellite, which might mean it can be flown out of the path of others before a catastrophic malfunction renders it immobile and dangerous. It’s a tough task for a robot. The extremes of brightness in space can confound imagerecognition programs, but better algorithms and increased processing power are helping. In 2005, the US air force tested just such an inspector. Outfitted with sensors including a laser rangefinder, the XSS-11 satellite flew around for more than a year, taking images of more than US-owned spacecraft, including its own spent Minotaur 1 launch rocket. Much as it could look, however, the probe could not touch. Lacking that capability, it will be impossible to relocate rogue satellites, since that would require the space bot not only to approach its target but to nudge it gently enough not to create any new space debris. A botched maintenance mission in 1984 highlights some of the challenges associated with designing a good grasping mechanism. A misbehaving probe was due for repair, and the shuttle astronaut in charge was supposed to use a robotic docking device to automatically latch on to it. Unbeknownst to NASA, however, technicians had changed the configuration of protective gold foil covering the probe just before launch. As sophisticated as it was, the robotic device was totally unprepared to cope with the altered structure and in the end the astronauts had to do it manually. “They > managed to just reach out and grab [the 10 November 2012 | NewScientist | 47
User COMMERCIAL
276
MILITARY Navigation/GPS Surveillance CIVILIAN Meteorological
91 57
3
Space chase
48 | NewScientist | 10 November 2012
17 15
276
2 65 1
Medium Earth orbit
399 Number of satellites
But what’s the best way to catch stray space debris? The Clean Space Initiative, recently launched by the European Space Agency (ESA), is evaluating a number of technologies that can drag satellites out of low-Earth orbit, the area below 2000 kilometres where the vast majority of our space junk lives. About half of that is the result of spacecraft explosions or collisions. Not only could these fragments make further collisions with healthy satellites more likely, they could potentially thwart our own spacefaring ambitions. If we want to continue spaceflight unimpeded, says Luisa Innocenti, who directs the initiative, “five to 10 pieces of debris must be removed per year”. She is looking at several firms that are developing gripper technologies. UK-based Astrium, for example, just completed Earthbased testing on a prototype harpoon. Mounted on a chaser satellite, the harpoon would spear the defunct satellite or rocket. To make it less likely that the harpoon would cause the dead satellite to break up, Astrium designers outfitted the harpoon with a mechanism that reduces its speed on impact. Having speared the rogue object, the chaser satellite would then attach a propulsion pack that sends it into Earth’s atmosphere to burn up. Other concepts ESA is studying include a robot arm, a Spiderman-like net that would envelop the target, and robotic tentacles, grippers inspired by sea anemones. Each has its pros and cons, says Innocenti. “If you do the harpoon or the robotic arm, you are going to have to touch it at one specific point”, she says, which could be difficult if the target satellite is tumbling out of control. “If you use tentacles or the robotic
Geosynchronous orbit
... and which orbits they are in
Elliptical orbit
The number of satellites in orbit around the Earth...
341 Total 1016
118
Orbit distances from Earth Geosynchronous Elliptical
103
35,786 km 500 - 5786 km
268
Low Earth orbit
satellite] with the shuttle’s arm,” says Henry Spencer, a spaceflight engineer based in Toronto, Canada. One of the main problems is that satellites simply aren’t built with maintenance in mind. They don’t have reflectors to act as easily identifiable reference points, for example, or any handles that robots could fix onto. So an effective gripper is crucial, says Alin Albu-Schäffer, director of the German Aerospace Center’s Institute of Robotics and Mechatronics in Wessling, which is developing a satellite able to tow others with a robotic arm. “If you have a tumbling satellite and you fail in grasping it, most probably afterwards it will tumble even faster,” he says. “You should make it on the first try.”
Medium Earth 200 - 35,786 km Low Earth
200 km
EARTH
money-spinners
arm, you have to be close to attach it.” So far, ESA is only looking at technologies suitable for low-Earth orbit. But a proper grasping mechanism would also help robotic tow trucks clear traffic in the much higher geosynchronous orbits – 35,000 kilometres above the equator – favoured by communications satellites. Travelling all the way down to burn up in Earth’s atmosphere is unrealistic, so before satellites in geosynchronous orbits run out of fuel, they are supposed to blast themselves some 250 kilometres up, into stable “graveyard” orbits. To help an immobilised satellite do that, a private venture called ViviSat is designing a module called the Mission Extension Vehicle that would dock with the satellite and provide its propulsion, either staying with it or simply sending it on its way to a graveyard orbit. Regardless of orbit, however, the right grasping mechanism is just a start. The far more difficult prospect is refuelling or repairing satellites, says Benjamin Reed at NASA’s Satellite Servicing Capabilities Office. He is in charge of the agency’s Robotic Refueling Mission. This month, a two-armed robot that sits outside the ISS, called Dextre, will attempt to refuel a test satellite the size of a washing machine. In so doing, Dextre will have to face another of the problems inherent in satellites built without maintenance in mind. Before launch, their fuel caps are closed and wired to the main body to prevent them coming loose during launch. Earlier this year, Dextre managed to cut these wires and remove two fuel caps of different shapes on the test satellite. This month, it will go a step further, filling the module with liquid ethanol fuel. As Dextre is beginning to make clear, a successful servicing robot will need to be equipped with a veritable Swiss army knife
Can satellite servicing turn a profit? Repairing satellites in space is a very expensive and complex process, which is why it hasn’t got going yet, says Scott Pace, director of the Space Policy Institute at George Washington University in Washington DC. Commercial satellite operators are riskaverse, preferring to launch anew rather than attempt a repair. But the tide seems to be turning, thanks to the rise in robotic capabilities (see main story) and increasing revenues: the satellite industry last year was worth more than $170 billion. A big aerospace company might operate dozens of communications satellites in the geosynchronous beltway above the equator, and because a service outage means big losses, an immediate repair might be preferable to waiting for a replacement satellite to be launched. A service robot could potentially last up to 15 years, zipping from one satellite to the next to do maintenance projects without using too much fuel. A few companies have thrown their hats into the ring to do exactly that. For
a retired communications satellite in the graveyard orbit and reuse the useful bits. The large antennas typically found on communications satellites are a good place to start. Not only are they valuable, they have no electronics or moving parts, so should last much longer than the original satellite. Phoenix will slice away the 1.5-metre-wide antenna, then attach it to tiny satellites that will serve as new power and control systems, giving the antenna new life. The agency hopes to launch the mission in 2015, and says it will share the technological lessons learned, to help develop a commercial servicing industry. “It could potentially change the way we do business in space,” says Hoffman (see “Money spinners”, above).
”Robots in orbit could assemble telescopes a dozen or more times as large as any Earth-based observatory, not to mention bigger spaceships” of tools. “Every satellite is different from the next,” Reed says. The technical challenge is to ferret out the similarities and design multifunction tools that can handle any job. Dextre has four tools but operational servicers will likely need up to a dozen. Although no satellite has yet been fixed by a robot, the US military’s research arm, DARPA, is already planning to take space mechanics to the next level: harvesting spare parts. Its Phoenix project aims to partially disassemble
Beyond that, however, a robust space servicing industry would have broader consequences for space science and human spaceflight, paving the way for orbital construction of structures that are too big to fit into one rocket. “Repair and assembly are not so different,” says Albu-Schäffer. Robots could assemble telescopes a dozen or more times as large as any Earth-based observatory. With such a huge light bucket, astronomers could catch photons from
example Canada’s MDA Corporation, which built the robotic arms on the space shuttle and International Space Station, hopes to have a refuelling mission ready to fly in three to four years. It’s a different story in low-Earth orbit, though, where satellites orbit in many different planes. Here it would require too much costly fuel for a robot mechanic to hop from one satellite to another. However, cost is not the only hurdle. Insurance agreements would have to be ironed out - who would be liable for damages to nearby spacecraft if a service robot ended up crashing into its intended client, generating sprays of debris? Any nation intending to service a satellite belonging to another nation would also have to have express permission to do so, according to UN treaties. However, with that permission, “I could posit a future in which 50 years from now, there are junk dealers in space that salvage this stuff and make money,” says Roger Launius, a space historian at the Smithsonian Institution in Washington DC.
the most distant – and therefore oldest – objects in the universe, and look for signs of life on Earth-like planets. “Ultimately, we want to build bigger and bigger telescopes,” says Hoffman. Not to mention bigger spaceships. In 1948, nearly a decade before the first satellite launched into orbit, aerospace pioneer Wernher von Braun wrote a science fiction novel about a human mission to Mars and, being a rocket scientist, worked out how to make it happen. His scheme called for 10 Marsbound spaceships, each weighing nearly 4000 tonnes to be assembled in Earth orbit from parts ferried there by 46 space shuttles. Today, proposed Mars missions are much more modest, but a rocket capable of carrying people is likely to weigh at least 150 tonnes, says Grant Bonin of the University of Toronto Space Flight Laboratory in Canada. That is 20 tonnes more than the largest rocket now on the drawing board, NASA’s Space Launch System – and nearly seven times as much as the space shuttle would have been able to carry. “A lot of people see it as inevitable that at some point we’re going to have to embrace on-orbit assembly,” he says. Space repair bots’ first jobs will likely be rather workaday – acting as tow trucks, gas station attendants or mechanics – but their ultimate mission may be much grander than today’s manufacturers imagine. n Maggie McKee is a journalist based in Boston, Massachusetts 10 November 2012 | NewScientist | 49
46 | NewScientist | 10 November 2012
Save our satellite When things go wrong in space, there’s no easy way to fix them, says Maggie McKee. But that’s about to change
R
USSIAN roulette was nothing compared to this. The 2-tonne satellite was screaming toward Earth, and most of it was expected to survive the rigours of re-entry. If it stayed aloft another 10 minutes parts of the defunct German X-ray satellite could smash into Beijing. It was pure luck that prevented disaster. Thanks to the craft’s orientation and the density of the atmosphere at the time, it missed China altogether and splashed down safely last year in the Bay of Bengal. Thankfully, such situations are rare, yet things do go wrong in space. Each year about one satellite is launched into the wrong orbit or is unable to deploy a crucial component, hobbling it at the beginning of its life. Others die because they’ve run out of fuel, cutting short their careers. What if there was a way to save satellites that go wrong? Not only could we wring more out of the hundreds of billions of dollars of equipment above our heads, we could ensure the safety of neighbouring satellites, which risk getting smashed up unless they blast themselves out of the way. Seeing this promise, a number of organisations around the world are now working to create robots that could go into orbit and service wonky satellites and other spacecraft. One day they could behave like real-life Wall-Es, scavenging the parts they need from orbital junkyards to build new craft. Eventually, the same technologies could build things in orbit that are too large to be launched in a single rocket, such as
vast telescopes or spacecraft bound for Mars. Robotic space repair has a long pedigree – in fiction. “You can find lots of that in science fiction all the way back to the 1950s before the first satellites were launched,” says Scott Pace, of the Space Policy Institute at George Washington University in Washington DC. But so far, all the work has been done by real live astronauts. Satellite repairs, like DIY projects on Earth, rarely go off without a hitch, and humans are adept at changing tactics on the fly. For example, on the final servicing mission to the Hubble Space Telescope in 2009, spacewalking astronauts had trouble loosening a bolt on a handrail they needed to remove to access a failed circuit board. “In the end, the astronaut just bent the handle back and forth until it finally broke off,” says Jeffrey Hoffman of the Massachusetts Institute of Technology, who as a NASA astronaut serviced Hubble in 1993.
Grunt work “That’s the sort of thing that would be very hard for a robot,” he says, since robots can only do what they have been explicitly designed, built and programmed to do. Along with five Hubble servicing missions, astronauts have fixed several commercial satellites from the space shuttle, not to mention doing the bulk of the construction work on the $100-billion International Space Station (ISS). However, after the Columbia space shuttle disaster of 2003, sending humans hundreds of kilometres into space to do repairs began
to seem overly risky, and NASA started to look more seriously into robotic repairs. Significant advances over the past 10 years mean such robots are starting to become reality. The easiest job will be inspection – flying around a craft looking for damage from micrometeorites or space debris. An autonomous spacecraft could help identify a damaged satellite, which might mean it can be flown out of the path of others before a catastrophic malfunction renders it immobile and dangerous. It’s a tough task for a robot. The extremes of brightness in space can confound imagerecognition programs, but better algorithms and increased processing power are helping. In 2005, the US air force tested just such an inspector. Outfitted with sensors including a laser rangefinder, the XSS-11 satellite flew around for more than a year, taking images of more than US-owned spacecraft, including its own spent Minotaur 1 launch rocket. Much as it could look, however, the probe could not touch. Lacking that capability, it will be impossible to relocate rogue satellites, since that would require the space bot not only to approach its target but to nudge it gently enough not to create any new space debris. A botched maintenance mission in 1984 highlights some of the challenges associated with designing a good grasping mechanism. A misbehaving probe was due for repair, and the shuttle astronaut in charge was supposed to use a robotic docking device to automatically latch on to it. Unbeknownst to NASA, however, technicians had changed the configuration of protective gold foil covering the probe just before launch. As sophisticated as it was, the robotic device was totally unprepared to cope with the altered structure and in the end the astronauts had to do it manually. “They > managed to just reach out and grab [the 10 November 2012 | NewScientist | 47
User COMMERCIAL
276
MILITARY Navigation/GPS Surveillance CIVILIAN Meteorological
91 57
3
Space chase
48 | NewScientist | 10 November 2012
17 15
276
2 65 1
Medium Earth orbit
399 Number of satellites
But what’s the best way to catch stray space debris? The Clean Space Initiative, recently launched by the European Space Agency (ESA), is evaluating a number of technologies that can drag satellites out of low-Earth orbit, the area below 2000 kilometres where the vast majority of our space junk lives. About half of that is the result of spacecraft explosions or collisions. Not only could these fragments make further collisions with healthy satellites more likely, they could potentially thwart our own spacefaring ambitions. If we want to continue spaceflight unimpeded, says Luisa Innocenti, who directs the initiative, “five to 10 pieces of debris must be removed per year”. She is looking at several firms that are developing gripper technologies. UK-based Astrium, for example, just completed Earthbased testing on a prototype harpoon. Mounted on a chaser satellite, the harpoon would spear the defunct satellite or rocket. To make it less likely that the harpoon would cause the dead satellite to break up, Astrium designers outfitted the harpoon with a mechanism that reduces its speed on impact. Having speared the rogue object, the chaser satellite would then attach a propulsion pack that sends it into Earth’s atmosphere to burn up. Other concepts ESA is studying include a robot arm, a Spiderman-like net that would envelop the target, and robotic tentacles, grippers inspired by sea anemones. Each has its pros and cons, says Innocenti. “If you do the harpoon or the robotic arm, you are going to have to touch it at one specific point”, she says, which could be difficult if the target satellite is tumbling out of control. “If you use tentacles or the robotic
Geosynchronous orbit
... and which orbits they are in
Elliptical orbit
The number of satellites in orbit around the Earth...
341 Total 1016
118
Orbit distances from Earth Geosynchronous Elliptical
103
35,786 km 500 - 5786 km
268
Low Earth orbit
satellite] with the shuttle’s arm,” says Henry Spencer, a spaceflight engineer based in Toronto, Canada. One of the main problems is that satellites simply aren’t built with maintenance in mind. They don’t have reflectors to act as easily identifiable reference points, for example, or any handles that robots could fix onto. So an effective gripper is crucial, says Alin Albu-Schäffer, director of the German Aerospace Center’s Institute of Robotics and Mechatronics in Wessling, which is developing a satellite able to tow others with a robotic arm. “If you have a tumbling satellite and you fail in grasping it, most probably afterwards it will tumble even faster,” he says. “You should make it on the first try.”
Medium Earth 200 - 35,786 km Low Earth
200 km
EARTH
money-spinners
arm, you have to be close to attach it.” So far, ESA is only looking at technologies suitable for low-Earth orbit. But a proper grasping mechanism would also help robotic tow trucks clear traffic in the much higher geosynchronous orbits – 35,000 kilometres above the equator – favoured by communications satellites. Travelling all the way down to burn up in Earth’s atmosphere is unrealistic, so before satellites in geosynchronous orbits run out of fuel, they are supposed to blast themselves some 250 kilometres up, into stable “graveyard” orbits. To help an immobilised satellite do that, a private venture called ViviSat is designing a module called the Mission Extension Vehicle that would dock with the satellite and provide its propulsion, either staying with it or simply sending it on its way to a graveyard orbit. Regardless of orbit, however, the right grasping mechanism is just a start. The far more difficult prospect is refuelling or repairing satellites, says Benjamin Reed at NASA’s Satellite Servicing Capabilities Office. He is in charge of the agency’s Robotic Refueling Mission. This month, a two-armed robot that sits outside the ISS, called Dextre, will attempt to refuel a test satellite the size of a washing machine. In so doing, Dextre will have to face another of the problems inherent in satellites built without maintenance in mind. Before launch, their fuel caps are closed and wired to the main body to prevent them coming loose during launch. Earlier this year, Dextre managed to cut these wires and remove two fuel caps of different shapes on the test satellite. This month, it will go a step further, filling the module with liquid ethanol fuel. As Dextre is beginning to make clear, a successful servicing robot will need to be equipped with a veritable Swiss army knife
Can satellite servicing turn a profit? Repairing satellites in space is a very expensive and complex process, which is why it hasn’t got going yet, says Scott Pace, director of the Space Policy Institute at George Washington University in Washington DC. Commercial satellite operators are riskaverse, preferring to launch anew rather than attempt a repair. But the tide seems to be turning, thanks to the rise in robotic capabilities (see main story) and increasing revenues: the satellite industry last year was worth more than $170 billion. A big aerospace company might operate dozens of communications satellites in the geosynchronous beltway above the equator, and because a service outage means big losses, an immediate repair might be preferable to waiting for a replacement satellite to be launched. A service robot could potentially last up to 15 years, zipping from one satellite to the next to do maintenance projects without using too much fuel. A few companies have thrown their hats into the ring to do exactly that. For
a retired communications satellite in the graveyard orbit and reuse the useful bits. The large antennas typically found on communications satellites are a good place to start. Not only are they valuable, they have no electronics or moving parts, so should last much longer than the original satellite. Phoenix will slice away the 1.5-metre-wide antenna, then attach it to tiny satellites that will serve as new power and control systems, giving the antenna new life. The agency hopes to launch the mission in 2015, and says it will share the technological lessons learned, to help develop a commercial servicing industry. “It could potentially change the way we do business in space,” says Hoffman (see “Money spinners”, above).
”Robots in orbit could assemble telescopes a dozen or more times as large as any Earth-based observatory, not to mention bigger spaceships” of tools. “Every satellite is different from the next,” Reed says. The technical challenge is to ferret out the similarities and design multifunction tools that can handle any job. Dextre has four tools but operational servicers will likely need up to a dozen. Although no satellite has yet been fixed by a robot, the US military’s research arm, DARPA, is already planning to take space mechanics to the next level: harvesting spare parts. Its Phoenix project aims to partially disassemble
Beyond that, however, a robust space servicing industry would have broader consequences for space science and human spaceflight, paving the way for orbital construction of structures that are too big to fit into one rocket. “Repair and assembly are not so different,” says Albu-Schäffer. Robots could assemble telescopes a dozen or more times as large as any Earth-based observatory. With such a huge light bucket, astronomers could catch photons from
example Canada’s MDA Corporation, which built the robotic arms on the space shuttle and International Space Station, hopes to have a refuelling mission ready to fly in three to four years. It’s a different story in low-Earth orbit, though, where satellites orbit in many different planes. Here it would require too much costly fuel for a robot mechanic to hop from one satellite to another. However, cost is not the only hurdle. Insurance agreements would have to be ironed out - who would be liable for damages to nearby spacecraft if a service robot ended up crashing into its intended client, generating sprays of debris? Any nation intending to service a satellite belonging to another nation would also have to have express permission to do so, according to UN treaties. However, with that permission, “I could posit a future in which 50 years from now, there are junk dealers in space that salvage this stuff and make money,” says Roger Launius, a space historian at the Smithsonian Institution in Washington DC.
the most distant – and therefore oldest – objects in the universe, and look for signs of life on Earth-like planets. “Ultimately, we want to build bigger and bigger telescopes,” says Hoffman. Not to mention bigger spaceships. In 1948, nearly a decade before the first satellite launched into orbit, aerospace pioneer Wernher von Braun wrote a science fiction novel about a human mission to Mars and, being a rocket scientist, worked out how to make it happen. His scheme called for 10 Marsbound spaceships, each weighing nearly 4000 tonnes to be assembled in Earth orbit from parts ferried there by 46 space shuttles. Today, proposed Mars missions are much more modest, but a rocket capable of carrying people is likely to weigh at least 150 tonnes, says Grant Bonin of the University of Toronto Space Flight Laboratory in Canada. That is 20 tonnes more than the largest rocket now on the drawing board, NASA’s Space Launch System – and nearly seven times as much as the space shuttle would have been able to carry. “A lot of people see it as inevitable that at some point we’re going to have to embrace on-orbit assembly,” he says. Space repair bots’ first jobs will likely be rather workaday – acting as tow trucks, gas station attendants or mechanics – but their ultimate mission may be much grander than today’s manufacturers imagine. n Maggie McKee is a journalist based in Boston, Massachusetts 10 November 2012 | NewScientist | 49