Canada’s robotics expertise is on display this week performing tasks never before attempted as part of a collaborative effort with NASA on the International Space Station (ISS).
Dextre, the Canadian Space Agency’s (CSA) dexterous robot is performing tasks in a project called the Robotic Refueling Mission (RRM). The three-day experiment will demonstrate if a robotic servicing satellite could in the future visit and refuel satellites in orbit, thus extending their lifetimes. Dextre is demonstrating the technologies, tools, and techniques needed to robotically service and refuel satellites in orbit, especially those not built with servicing in mind.
Dextre, which is short for Special Purpose Dexterous Manipulator or SPDM, was launched on shuttle mission STS123 in March 2008. Along with the Canadarm2 and the Mobile Servicing System, Dextre is Canada’s robotic contribution to the ISS.
The ability to refuel and service satellites could in the future save satellite operators millions of dollars. Communications satellites last many years – even decades. Their lifetimes are limited by the amount of fuel they have onboard. The fuel is used to operate small rocket thrusters that keep the satellite pointed in the right direction. When the fuel supply is exhausted, the satellite begins to tumble and is useless.
The engineering model for the Remote Refuelling Module on display at the Kennedy Space Center Press Site during the STS 135 countdown. Credit: SpaceRef
The hardware being used for this demonstration was launched on the last space shuttle flight, STS 135 last July. RRM and Dextre will proceed through several tasks over about the next two years designed to demonstrate a wide array of servicing capabilities. RRM results are expected to reduce the risks associated with satellite servicing as well as lay the foundation and encourage future robotic servicing missions. Such future missions could include the repair and repositioning of orbiting satellites.
The RRM tool kit and task box was designed and built at the Goddard Space Center in Maryland. Dextre operations for the Robotic Refueling Mission will be remotely controlled by flight controllers at NASA’s Johnson Space Center in Houston, Texas, and the Canadian Space Agency’s Mission Operations Centre in Saint-Hubert, Quebec.
Included within the RRM module are four unique tools to be used by Dextre: the Wire Cutter and Blanket Manipulation Tool, the Multifunction Tool, the Safety Cap Removal Tool, and the Nozzle Tool. Each tool is stowed in its own storage bay until Dextre retrieves it for use. Each tool contains two integral cameras with built-in LEDs to give mission controllers the ability to see and control the tools.
The test this week is called the Gas Fittings Removal task. During the first step, mission operators will direct Dextre to remove three of the RRM tools from the module and perform functional checkouts prior to in-orbit operations. The RRM Multifunction tool will be used to release the “launch locks” that kept three tool adapters tightly secure during the shuttle flight of RRM to the space station. Next, Dextre will use the Wire Cutter Tool to cut the lock wire that every spacecraft employs. This activity will show that even tiny lock wire, the thickness of four sheets of paper, can be isolated and cut using the latest robotic technologies, tools, and precision techniques.
During future demonstrations, Dextre will cut through the simulated satellite’s exterior, remove layers of insulation and cut away the wiring covering the fuel cap. In the next phase of the operation, the robotic handyman will connect a hose to the fuel valve and pump simulated liquid fuel into the mock spacecraft.
Subsequent RRM operations include practicing robotic satellite refueling and servicing tasks using Dextre, RRM tools, and the satellite piece parts and interfaces contained within and covering the cube-shaped RRM module.
The Robotic Refueling Mission (RRM) module on the International Space Station before it was installed on its permanent platform. RRM will demonstrate robotic servicing technology and lay the foundation for future missions. (Credit NASA)
The International Space Station played a critical role in RRM development. “RRM showcases the best of what the International Space Station can offer as a test bed for state-of-the-art space technologies,” says Frank Cepollina, veteran leader of five Hubble Space Telescope servicing missions and Associate Director of the Satellite Servicing Capabilities Office (SSCO) at NASA’s Goddard Space Flight Center in Greenbelt, Md.
“The Hubble servicing missions taught us the importance and value of getting innovative, cutting-edge technologies to orbit quickly to deliver great results,” continued Cepollina. “With the established infrastructure that the space station provides, our RRM team had support as we conceived, designed, built, and flew the RRM demo to space station in 18 months — a timeline that many declared impossible.”
The impact of the ISS as a useful technology test bed cannot be overstated, he said. “Fresh satellite-servicing technologies will be demonstrated in a real space environment within months instead of years. This is huge. This represents real progress in space technology advancement.”
“The significance of RRM is that it demonstrates that robotic satellite-servicing technology exists now and it works correctly on orbit,” says Benjamin Reed, Deputy Project Manager of SSCO.
The Canadian Space Agency is an essential partner in RRM operations. Dextre, the space station’s twin-armed Canadian robotic “handyman,” was developed by the CSA to perform delicate assembly and maintenance tasks on the station’s exterior as an extension of its 57-foot-long (17.6 meter) robotic arm, Canadarm2. CSA wrote the software to control Dextre during RRM operations. Along with NASA Goddard and Johnson Space Center, CSA tested the software with flight-like tools and the RRM high-fidelity mockup in January-February 2012 at the MacDonald, Dettwiler and Associates Ltd. facility in Brampton, Canada. “The Canadian Space Agency has played a pivotal role in the development of space robotics, from the early days of the space shuttle to the work they are doing with Dextre on ISS,” says Cepollina.
The work being done on the Robotic Refueling Mission is in line with Canada’s own efforts to advance state-of-the-of-art space robotics with the Next-Generation Canadarm project, a research and development initiative that is developing new robotic architectures, components, tools and techniques today for the servicing missions of tomorrow.
The next test phase of the RMM will be in May and July of this year.