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Helping hands for astronauts
By Matthias Gründer
The first time that the public and specialists became aware of the German capability in the development of robots was in 1993 when scientists from the German Aerospace Centre (DLR) steered their “Rotex” robotic arm from the earth so accurately during the D-2 space shuttle mission that they even succeeded in catching a free-floating object with it. However, the original impulse for developing such a capability in space had come from the failure of German telecommunications satellite TV-Sat1 to deploy one of its solar panels in 1988, making it tantamount to lost. “At that time the question was raised as to whether such problems could not be eliminated with robots,” reports Klaus Landzettel, coordinator for space robotics at the DLR Institute of Robotics and Mechatronics in Oberpfaffenhofen, “and since then we have been working on such solutions.”
A study was carried out, following which testing of such an Experimental Servicing Satellite (ESS) was considered. However, funding problems prevented the idea from becoming a reality, even though it was possible to accumulate a lot of useful experience and to developed and test some tools. Thus, a tool for capturing stranded satellites and the docking method were ready and waiting in cold storage. “One needs to have technologies stockpiled in case someone should subsequently ask for them,” says Landzettel, whose love for his work is very obvious.
Three primary roles for future robots were defined at that time:
1. Robots should support astronauts as assistants and in this capacity above all perform difficult or dangerous work under supervision;
2. They should be capable of disposing of hazardous materials or subassemblies, for example, moving satellites which have outlived their usefulness onto harmless crash trajectories; and
3. They should be able to work on remote planets autonomously.
With regard to the first point, although a lot of thought has already gone for psychological reasons into the question of whether these “metal companions” should be given a body, head and arms and voice control, these are not necessary for robots in other fields of activity. We therefore need to turn our backs on the popular notion that future, operational robots will be human-like machines with wills of their own. Rather, they will assume many different forms, as service boxes with one or two hands or claw arms, as running gear or as automatic rovers which roam around on the moon or Mars relatively independently and perform experiments there.
Klaus Landzettel's team at any rate continued working on a range of solutions and in 2004 they unveiled a mobile ROBUTLER at “Automatica” in Munich, whose robotic hands were, thanks to sophisticated sensors, already capable of responding to counterpressure and could ease their grip accordingly, thus ensuring, for example, that a raw egg was not crushed.
A successful robotics experiment designated Robotics Component Verification on the ISS (ROKVISS) is currently flying on the ISS. At the centre of the experiment is a compact piece of equipment with highly integrated, modular robotic components, an arm with two joints, a finger and two integrated cameras, which was installed on the external wall of the ISS in January 2005. Originally it was supposed to be tested for a year by remote control from earth, but it functions simply without problems, so the experiment is being continued for another year. In practice, an arm is controlled in three dimensions by joystick on earth through a milled-out labyrinth of openings, and even a spring can be tensioned by this means. Sensors report back the forces encountered, so that the operator, for example, has to respond with more pressure on the stick as the spring tension increases.
“With this device we have proved that our design works faultlessly and for prolonged periods under the conditions of free space,” says Klaus Landzettel proudly. “All the data we obtain from this experiment is practical proof of the quality of our design and will help us to realise future projects.”
If the funding is there, robots from Germany need not just be a dream
One of these projects is the ConeXpress space tug from Orbital Recovery which is intended to dock onto stranded, geostationary satellites and extend their service life with the aid of a dedicated onboard propulsion unit. It is to be launched with Ariane 5, and Klaus Landzettel's team has already completed the coupling system. This entails introducing a spindle into the nozzle of the onboard engine of the “old” satellite and anchoring it, following which the miniature assistant will take over attitude control of the satellite. The technology for this was developed during work on the above-mentioned ESS.
“We would now naturally like to couple our highly developed robotic arms with such a hunting device and send a wide variety of robots to work in space,” says Klaus Landzettel. The hunt for satellites which are no longer operational and their interception has already been successfully tested in collaboration with Japanese specialists during the mission of the JAXA satellite ETS-VII. In future the aim is to construct robotic satellites which are capable of carrying out repairs or assembly work in space, replacing defective components or replenishing empty fuel tanks.
More simple single-use models could intercept flying objects which no longer serve any useful purpose and induce them to crash above safe areas, for not all the components of a satellite burn up upon re-entry into the denser layers of the earth's atmosphere. For example, the massive glass mirrors of observation satellites, unless controlled, could smashed into the earth like bombs.
“To develop such robots we need about €100 million from the national space programme,” says Landzettel. This may sound a lot, but once the robots are sufficiently mature for series production they could bring in a lot more revenue. This money should be made available as a matter of urgency – before someone else conquers this market.
From FLUG REVUE 3/2007
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