Robotic Refueling Mission (RRM) - 10.21.14
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The Robotic Refueling Mission (RRM) investigation uses the International Space Station’s two-armed robotic handyman, Dextre, to show how future robots could service and refuel satellites in space. RRM tests NASA-developed technologies, tools and procedures to refuel and repair satellites that were not originally designed to be serviced. RRM is expected to pave the way for future robotic servicing missions in space.
Science Results for Everyone
Goddard Space Flight Center, Greenbelt, MD, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
March 2011 - March 2014
Previous ISS Missions
This is the first operation of RRM in microgravity.
The Robotic Refueling Mission (RRM) demonstrates robotic satellite-servicing technology and techniques using Dextre, the International Space Station's (ISS) twin-armed Canadian robotic handyman; four unique RRM tools; and an RRM module containing satellite piece parts, refueling components and a series of interface testing activity boards. During operations, Dextre uses four unique RRM tools to demonstrate satellite-servicing and refueling tasks, including cutting and manipulating protective blankets and wires, unscrewing caps and accessing valves, transferring fluid, and leaving a new cap in place for future refueling activities. The investigation also demonstrates general space robotic operations. RRM marks the first use of Dextre beyond the planned maintenance of the ISS and uses Dextre for technology research and development.
To meet the challenge of on-orbit robotic servicing, the RRM development team assessed what tasks would be necessary for a robot to service a satellite and to access the triple-sealed fuel valve of an orbiting satellite to refuel it. They then developed the cube-shaped RRM module that breaks down each servicing activity into distinct, testable tasks and provides the components, activity boards, and tools to practice them. RRM is the first NASA on-orbit demonstration of the technology needed to robotically refuel and service spacecraft not originally built for in-flight service.
- RRM is designed to demonstrate that remote-controlled robots can perform servicing and refueling tasks in orbit via ground commanding. As the first on-orbit attempt to test robotic refueling techniques for spacecraft not built with on-orbit servicing in mind, RRM is expected to reduce risks and lay the foundation for future robotic servicing mission.
NASA's Robotic Refueling Mission (RRM) is an external International Space Station investigation designed to demonstrate and test the tools, technologies and techniques needed to robotically refuel and repair satellites in space, especially satellites that were not designed to be serviced. A joint effort between NASA and the Canadian Space Agency (CSA), RRM is the first in-orbit attempt to test robotic refueling and servicing techniques for spacecraft not built with in-orbit servicing in mind. It is expected to reduce risks and lay the foundation for future robotic servicing missions. RRM also marks the first use of Dextre beyond assembly and maintenance of the space station for technology research and development.
After Atlantis docks with station, RRM is transferred during a spacewalk to Dextre’s Enhanced Orbital Replacement Unit Temporary Platform (EOTP). Following the shuttle’s departure, RRM remains on the EOTP until Dextre and Canadarm2 finally transfer RRM to its permanent location on ExPRESS Logistics Carrier 4 (ELC-4). The ELC provides command, telemetry and power support for the investigation. RRM operations are be entirely remotely controlled by flight controllers at NASA's Goddard Space Flight Center in Greenbelt, Md., Johnson Space Center in Houston, Marshall Space Flight Center in Huntsville, Ala., and the CSA's control center in St. Hubert, Quebec.
To meet the challenge of satellite servicing and robotic refueling, the RRM development team assessed what tasks would be necessary for a robot to perform various servicing tasks, including accessing the triple-sealed fuel valve of an orbiting satellite to refuel it. They then developed the cube-shaped RRM module that breaks down each servicing activity into distinct, testable tasks and provides the components, activity boards, and tools to practice them. The RRM module is about the size of a washing machine and weighs approximately 550 pounds (250 kg), with dimensions of 43" by 33" by 45" (109 cm by 84 cm by 114 cm). RRM includes 0.45 gallon (1.7 liters) of ethanol that is used to demonstrate fluid transfer in orbit.
With the RRM module securely mounted to the space station’s ELC-4 platform, mission controllers direct the Dextre robot, the space station’s Canadian, twin-armed “handyman,” to retrieve RRM tools from the module and perform a full set of servicing and refueling tasks. Dextre uses the RRM tools to cut and manipulate protective blankets and wires, unscrew caps and access valves, transfer fluid, and leave a new fuel cap in place. At one stage of the mission, Dextre uses RRM tools to open up a fuel valve, similar to those commonly used on satellites today, and transfer liquid ethanol across a robotically mated interface via a sophisticated robotic fueling hose. Each task is performed using the components and activity boards contained within and covering the exterior of the RRM module. The investigation also demonstrates general space robotic repair and servicing operations. Completing the demonstration validates the tool designs (complemented with cameras), the fuel pumping system, and the robotic task planning, all of which can be used during the design of a potential future servicing spacecraft.
The six RRM tasks consist of:
- Launch Lock Removal and Vision - On September 6-7, 2011, mission controllers use the Dextre robot to successfully release the "launch locks" on the four RRM servicing tools. These locks keep the RRM tools secure within the RRM module during the shuttle Atlantis' flight to the International Space Station. Once this task is complete, the RRM team then uses Dextre's cameras to image the RRM hardware in both sunlight and darkness, providing data that NASA's Satellite Servicing Capabilities Office uses to develop machine vision algorithms that work in spite of harsh on-orbit lighting. All subsequent RRM tasks are performed using RRM Tools.
- Gas Fittings Removal - Marking the first use of RRM Tools on orbit, Dextre uses the RRM tools to remove the fittings that many spacecraft have for the filling of special coolant gases.
- Refueling - After Dextre opens up a fuel valve that is similar to those commonly used on satellites today, it tests the transfer of liquid ethanol through a sophisticated robotic fueling hose.
- Thermal Blanket Manipulation - Dextre practices slicing off thermal blanket tape and folding back the thermal blanket to reveal the contents underneath.
- Screw (Fastener) Removal - Dextre robotically unscrews satellite bolts (fasteners).
- Electrical Cap Removal - Dextre removes the caps that would typically cover a satellite's electrical receptacle.
- The Wire Cutter Tool's precision and fine-grabbing capabilities allow it to both snip tiny wires and safely move aside delicate thermal blankets. A spade bit on the tool's tip can slice blanket tape. Its parallel jaw grippers are able to grab a satellite's appendages.
- The Multifunction Tool lives up to its name by effectively doing the work of four tools. It connects with four unique adapters to capture and remove three distinct caps and remove one gas "plug" on the RRM module.
- The Safety Cap Tool removes and stows a typical fuel-valve safety cap and its seal. Small adapters allow it to also manipulate screws and remove caps on the RRM module.
The Nozzle Tool connects to, opens and ultimately closes a satellite fuel valve. Using an attached hose, it transfers a representative satellite fuel in a continuous loop to simulate the refueling of a satellite. The fuel cap that the tool leaves behind has a "quick disconnect" fitting that gives operators easy future access to the valve, should it be needed.
Drawing upon 20 years of experience servicing the Hubble Space Telescope, the Satellite Servicing Capabilities Office (SSCO) at NASA's Goddard Space Flight Center initiated the development of RRM in 2009. Atlantis, the same shuttle that carried tools and instruments for the final, crewmember-based Hubble Space Telescope Servicing Mission 4, now carries the first step to on-orbit robotic refueling and satellite servicing on the last shuttle mission to space.
RRM is showing that remote-controlled robots, with the right set of tools and technologies, can perform complicated servicing and refueling tasks in orbit. Refueling and repairing satellites with robots would extend satellites’ lifespans, thus saving money while reducing orbital debris. Extending a satellite’s life can ease or eliminate disruptions in the services that the spacecraft provide.
Robotic satellite refueling and servicing would allow spacecraft to live and operate longer in space. Satellite owners and operators could save significant cost and effort, which would otherwise be spent building new replacements. Additionally, NASA’s Remote Robotic Oxidizer Transfer Test, which built upon RRM technology, could one day be used to keep humans at a safe distance while satellites are filled with propellant on the ground – an extremely hazardous operation.
During RRM operations, Dextre uses four unique RRM tools to demonstrate a suite of satellite-servicing and refueling tasks, including cutting and manipulating protective blankets and wires, unscrewing caps and accessing valves, transferring fluid, and leaving a new cap in place for future refueling activities. The investigation also demonstrates general space robotic operations.
RRM operations are being managed from Goddard Space Flight Center. Robotic operations are controlled by Johnson Space Center, with payload commanding performed from Marshall Space Flight Center.
Before a satellite leaves the ground, technicians fill its fuel tank through a valve that is then triple-sealed and covered with a protective blanket, designed never to be accessed again. RRM tests whether a robot can remove these barriers and refuel such a satellite in space through a series of activity boards and four unique RRM tools specially designed to get the job done. It also demonstrates a suite of general robotic satellite-servicing tasks and activities.
During RRM operations, Dextre, the ISS's twin-armed Canadian robotic handyman, acts as a skilled spacecraft servicing and refueling technician. Dextre was developed by the CSA to perform delicate assembly and maintenance tasks on the ISS's exterior as an extension of its 57-foot-long (17.6 meter) robotic arm, Canadarm2. The RRM box, which was ultimately mounted on an external ISS platform, includes protective thermal blankets, caps, valves, simulated fuel, and other components that need to be pushed back, cut through, unscrewed and transferred. Each component and activity board represents an individual refueling task, and each RRM tool is designed to efficiently complete a wide range of targeted tasks.
For instance, to fill up RRM's fuel tank with a simulated fuel, one of Dextre's robotic end-effectors or ORU Tool Change Out Mechanisms (OTCM) would retrieve the Nozzle Tool from RRM, securely connect the tool to the fuel valve on the RRM box, and transfer fluid (the simulated fuel) through the valve. While such activities are similar to grabbing a fuel nozzle at the gas station and filling up a car’s gas tank, each RRM task requires a high level of robotic precision and demonstrates state-of-the-art refueling technology, tools and techniques.
Satellite Servicing Capabilities Office
Robotic Refueling Mission
This artistic representation shows ISS’s Dextre robot (right) performing a robotic refueling task on RRM (center), mounted to ELC4. Image Credit: NASA
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In this artistic representation, the Wire Cutter and Blanket Manipulation Tool (right) approaches the RRM module (left) to cut wire on a sealed cap. Integral cameras with built-in LEDs and sensors light the way and give Mission Controllers a front-seat view of the tool’s action. Image Credit: NASA
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The RRM module is peppered with refueling components and activity boards and contains a fluid transfer system. Four unique tools are stowed within RRM until Dextre retrieves them. Image Credit: NASA
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07.12.2011 - On July 12, 2011, spacewalking crewmembers Mike Fossum and Ron Garan successfully transfer the Robotic Refueling Mission module from the Atlantis shuttle cargo bay to an temporary platform on the International Space Station's Dextre robot. Image Credit: NASA
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The Robotic Refueling Mission module on the International Space Station, temporarily installed on the Dextre robot's Enhanced ORU Temporary Platform. On September 2, 2011, space station's Canadarm2 and Dextre robot transfer RRM to its permanent location on the ExPRESS (Expedite the Processing of Experiments to the Space Station) Logistics Carrier-4. Image Credit: NASA
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The Wire Cutter Tool has the functionality of four: it grabs, it snips, it manipulates, and it slices. Image Credit: NASA/Chris Gunn
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