Robotic repairman
Published on Mar 13, 2007 at 7:09 am.
1 Comment.
Filed under space exploration.
Years ago, science fiction writers introduced the concept of robots capable of doing difficult and hazardous duties so that human lives would not be endangered. One of these tasks would be servicing satellites in orbit. Eventually, scifi writers began to introduce the idea of autonomous servicing satellite, capable of maneuvering to rendezvous with a satellite that needs servicing, conducting that service, and then go service another satellite. Now, that dream is close to being realized.
Last week, a pair of spacecraft lifted off from Cape Canaveral Air Force Station in a test of technology that may let this happen. The test program, dubbed Orbital Express is managed by DARPA (Defence Advanced Research Projects Agency). The satellites were constructed by Boeing Integrated Defense Systems, and sophisticated guidance systems for the craft were developed by NASA. The project is basically a research program designed to support military satellites, but the technology, or a derivative of it, would also be available to work with civilian satellites.
Orbital Express consists of two satellites. One is a target satellite, and the other simulates the repair satellite. The two craft will orbit for the next three months or so docking, undocking, moving apart, finding one another, and docking again to test the technology. To find one another, the service vehicle bounces lasers off of special reflectors fixed to the target vehicle. The guidance systems are designed to be autonomous. The service vehicle is supposed to be able to find and dock with the target without any input from ground controllers. Ultimately, the goal would be for the service vehicle to also conduct certain routine servicing also without input from the ground. More complex missions would likely always require ground controllers.
This is really an important step towards making space more affordable. At present, if a satellite breaks, runs out of coolant, fuel, etc., then it is basically just so much expensive space junk. The ability to service and rehabilitate satellites on orbit was one of the big selling points for the Space Shuttle. In fact, the Shuttle was used to service some satellites, but it never lived up to its promise of routine service missions to refurbish satellites. The only satellite routinely serviced has been the Hubble Space Telescope. One problem is that the Space Shuttle is nowhere near as safe as it had been billed in its first years of operation. Every launch is a risk to astronauts’ lives. So, a cost and benefit analysis must be made for each launch. Routine repair of average satellites is not thought worth the risk to the astronauts. Servicing Hubble, though, is a bit different, since it is a special one of a kind piece of equipment. If a weather or communication satellite fails, another can be launched to take its place (in fact there are redundancies, so one already in orbit would take its place first).
But, a fleet of autonomous service and repair satellites in orbit could change all that. There is no risk to astronaut lives, and a number of these could be launched and parked in useful orbits. When a satellite need service, the best positioned service craft could do the job. Generally, I would imagnie this would be for geosynchronous orbits, because low Earth orbits are harder to match up without a lot of forethought. But, a craft could be launched specifically to fix a particular low Earth orbit satellite if needed, and if it were cost effective.
-Astroprof
Image Credits: United Launch Alliance, Boeing, DARPA
Astroprof’s Page » CUSat: Nanosat-4 Winner on April 5, 2007 at 4:24 pm: 1
[…] A few weeks ago, I wrote about the Orbital Express mission.  One of the goals of that mission is to evaluate technology that may allow autonomous robotic maintenance satellites to perform routine maintenance and repairs on satellites in orbit. Today, I am going to write about CUSat, a student designed satellite from Cornell University. CUSat was selected last week as the winner of the University Nanosatellite Program (Nanosat-4 Competition). The goal of this program is to promote space engineering by allowing students to work on designs for very small and inexpensive satellites (inexpensive is relative: It will still cost about $500,000 to complete the CUSat satellite). As winner of the competition, CUSat will be launched for free, so all the money raised for the project can go towards construction and operation of CUSat. If everything goes well, then CUSat might be able to be launched within two years or so. CUSat is launched as a small hexagonal “cylinder” that separates into two identical pieces in orbit.  The pieces then move about 10 meters apart.  Each sub-satellite can then maneuver around the other one taking pictures of its companion. Using GPS positioning, the CUSat team believes that the CUSat can achieve up to a 2 degree pointing accuracy. The high resolution images are then beamed back to Earth, where they can be used to create a highly accurate 3-D model of the object being studied. […]