By Kalwinder KaurMar 15 2013
Introduction
Research
Current Applications
Future Developments
References
Introduction
NASA’s Satellite Servicing Capabilities Office (SSCO) is planning a mission that will introduce a robotic servicing vehicle that can access, repair and refuel satellites in a geosynchronous earth orbit (GEO).
SSCO has undertaken an aggressive development campaign in order to mature technologies in unexplored territories to enable such a robotic servicing mission.
Efforts in this direction include the following:
- Advanced robotic satellite servicing robots and dexterous robotics: RRM on the International Space Station.
- Autonomous docking and rendezvous systems: Argon tests at the Naval research Laboratory and Goddard.
- Propellant transfer systems for zero gravity: Development work conducted by NASA's Kennedy Space Center.
- Hose Reel Tests: Development work by SSCO at the University of Maryland and Goddard.
- Specialized algorithms (computer commands) to synchronize and orchestrate satellite-servicing operations: Flights on Zero-G airplanes by SSCO, University of West Virginia and Yaskawa America.
Research
RRM (Robotic Refueling Mission) tests conducted from January 14 to 25 ended in a robotic fluid transfer, the first of its kind, a demonstration that can enable improved robotic satellite servicing capabilities and result in a more sustainable, greener space.
According to the associate director of the Satellite Servicing capabilities office or SSCO at NASA’s Goddard Space Flight Center in Greenbelt, RRM provides NASA and the commercial satellite servicing industry the confidence to repair, refuel and maintain satellites robotically in both distant and nearby orbits.
NASA | Behind the Scenes at the Satellite Servicing Center and Robotic Lab
Operation of the Robotic Refueling Mission (RRM) on the International Space Station. Credits: NASA.
The idea of RRM was conceived by veterans of five manned servicing missions to NASA’s Hubble Space telescope, Cepollina and the SSCO team and these veterans enabled its rapid 18-month development to its launch on STS-135 in July 2011.
RRM, in a joint effort with the Canadian Space Agency used the space station as a test bed for R&D of robotic satellite servicing capabilities.
The sophisticated technologies exhibited by RRM shows that it can extend the lifespan of many of the hundreds of satellites present in GEO.
The RRM activities in January made use of the Canadian tele-operated Dextre robot, four advanced RRM tools and the RRM module to conduct a complete refueling demonstration on orbit.
Robotic controllers present at NASA’s Johnson Space Center in Houston initially commanded an RRM tool working at the end of over 21.34 m of combined Canadarm2 robotics and Dextre to cut a twisted wire pair each 0.02 inches in diameter. Exacting tasks were done after that with RRM tools cutting more wire used for securing satellite parts during launch.
The RRM nozzle was threaded with its attached hose onto the calve by the Johnson team, after which NASA’s Marshall Space Flight Center in Huntsville, Ala sent an accurate command sequence to activate the RRM Fluid Transfer System.
The sequence resulted in liquid ethanol flowing from the fluid transfer system into the muzzle tool and through the attached fuel calve pulsing back into the reservoir of the module.
On completion of the fluid transfer, an innovative technique is adopted by the nozzle tool for withdrawal from the valve leaving a clever fitting that will enable a simpler and effective future refueling connection.
RRM tasks scheduled for 2013 include thermal blanket cutting, electronic and fastener termination cap removal.
RRM operation results show that present day robotic technology can refuel the triple-sealed common satellite fuel valves of orbiting satellites. SSCO is planning to present the successful RRM results in the upcoming satellite 2013 conference and also during space station panels and other events.
Current Applications
GEO is one of the busiest highways in our solar system and is located 22,000 miles above the earth.
Each day around 400 satellites commute on the GEO providing services such as cell phone communications, government communications, TV broadcasts and air traffic management.
Maintenance and refueling of these costly assets can keep them operating for longer offering commercial and government stakeholders more value from initial investments and offer sufficient savings in replacement of spacecraft and launch costs.
It is important to service these satellites to ensure that space is more sustainable and greener.
Drifting and broken satellites take up valuable GEO real estate and pose a risk to their space neighbors.
Satellite servicing technologies are not just a way for satellite fixing, they enable deep-space discovery and exploration. With these robotic capabilities, NASA can be better equipped to assemble a habitat in space or an observatory, catch up with an asteroid, or fix a spacecraft en route to Mars.
Future Developments
The Goddard Satellite Servicing Center is similar to an incubator for satellite servicing technology where space components, systems and tasks are tested, honed and refined in simulated environments and declared ready for action in orbit.
These labs present on earth make use of a motion-based platform, industrial robots and standard algorithms to create space operation simulation on large and small scales.
Capabilities range from stimulation of a robotic arm to servicing a satellite in space to the response of a satellite to a tumbling object. Mission developers use the data of the facilities to fine-tune systems and controllers for optimum environment interaction and performance.
The facilities are not just simulation labs, they are technology test beds and development centers all in one.
The facilities make use of a 3D dynamic simulator powered by industrial robots and a motion-based platform offering a wide range of movement and dexterity. This enables facilities to deliver small and large-scale simulations with actual flight hardware and mock-ups.
The West Virginia facility is characterized by a combination of space-qualified and industrial robots, full scale models of space vehicles and a combination of space-qualified and industrial robots. The facility has a mock-up of a cargo and an airlock hold, a human exploration vehicle and satellite models.
NASA has one Satellite Servicing Center at the Goddard Space Flight Center in Greenbelt, which is devoted to flight hardware preparations and small-scale simulations. The West Virginia research and Technology Centre in Fairmont is dedicated to developing and evaluating evolving technologies.
References
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