NASA - National Aeronautics and Space Administration

Overview | Description | Applications | Operations | Results | Publications | Images

Experiment/Payload Overview

Brief Summary

The Robotic Refueling Mission (RRM) investigation demonstrates and tests the tools, technologies and techniques needed to robotically service and refuel satellites in space, especially satellites not originally designed to be serviced. RRM is expected to reduce risks and lay the foundation for future robotic servicing missions in microgravity.

Principal Investigator

Frank Cepollina, , Goddard Space Flight Center, Greenbelt, MD, United States

Co-Investigator(s)/Collaborator(s)

Benjamin Reed, , Goddard Space Flight Center, Greenbelt, MD, United States

Payload Developer

Goddard Space Flight Center, Greenbelt, MD, United States

Sponsoring Space Agency

National Aeronautics and Space Administration (NASA)

Sponsoring Organization:

Human Exploration and Operations Missions Directorate (HEOMD)

ISS Expedition Duration:

March 2011 - March 2013

Expeditions Assigned

27/28, 29/30, 31/32, 33/34

Previous ISS Missions

This is the first operation of RRM in microgravity.

^ back to top

---

Experiment/Payload Description

Research Summary

• The Robotic Refueling Mission (RRM) demonstrates robotic satellite-servicing technology and techniques using the Special Purpose Dexterous Manipulator (SPDM), also known as Dextre (the International Space Station's (ISS) the 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 the mission, Dextre uses four unique RRM tools to demonstrate a full 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 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 perform robotic refueling and servicing of spacecraft not originally built to be serviced.



• 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 missions.

Description

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.

RRM launches to the space station with four unique tools developed at Goddard: the Wire Cutter and Blanket Manipulation Tool, the Multifunction Tool, the Safety Cap Removal Tool and the Nozzle Tool. Each tool is stored in its own storage bay in the RRM module until Dextre retrieves it for use. To give mission controllers the ability to see and control the tools, each tool contains two integral cameras with built-in LEDs.

• 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.

One of the secondary goals of RRM is to collect performance data from all RRM operations conducted on the space station and use this information to validate "tool-to-spacecraft" simulations of contact dynamics on the ground. The Goddard Satellite Servicing Center (GSSC) was developed in parallel with the RRM flight hardware. One objective is to validate that GSSC accurately simulates the dynamic space environment of the space station. Such a confirmation would validate Goddard?s capability to develop and test any future space robotic servicing and assembly missions with a very high degree of accuracy. More information about the facility is available here: http://ssco.gsfc.nasa.gov/facility.html

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.

SSCO's prime contractor base consists of Lockheed Martin, Stinger Ghaffarian Technologies, Orbital Sciences Corporation, Alliant Techsystems, Jackson and Tull, and Arctic Slope Regional Corporation.

^ back to top

---

Applications

Space Applications

Robotic refueling and servicing could extend a satellite's lifespan, potentially offering satellite owners and operators years of additional service and revenue, more value from the initial satellite investment, and significant savings in delayed replacement costs. Numerous satellites are in orbit today in that could benefit from such a service.

In-orbit robotic refueling and servicing have also been identified by several nations and space agencies as a critical capability that supports overarching autonomy and expansion in space. If applied in conjunction with a fuel depot, robotic refueling would eliminate the need for space explorers and satellites to carry up heavy amounts of fuel at launch, thus freeing up weight for mission-critical equipment and capabilities. Robotic refueling and servicing have the potential to allow human and robotic explorers to reach distant destinations more efficiently and effectively.

As an ISS investigation, RRM reduces the risk associated with performing robotic servicing tasks in-orbit and lays the foundation for a future robotic servicing mission to a free-flying satellite. It also advances space robotic capabilities. It is the first NASA technology demonstration to test and prove technology needed to perform robotic refueling and servicing on spacecraft not originally built for them, and the first use of Dextre beyond robotic maintenance of the space station for technology research and development.

One of RRM's secondary goals is to collect performance data from all RRM operations conducted on Space Station and use this information to validate a Tool-to-Spacecraft contact dynamics robotics simulation facility that has been developed on the ground in parallel with the RRM flight hardware. The Goddard Satellite Servicing Center?s first objective is to validate that the facility accurately simulates the dynamic space environment of Space Station. With that knowledge, the team then plans to expand the Center's capability to develop and test any future space robotic servicing and assembly missions with a higher degree of assurance.

Earth Applications

Robotic refueling extends the lifetime of satellites, allowing owners and operators to gain additional years of use from assets already operating in space. Technology spinoffs have the potential to benefit humankind in yet-undiscovered ways.

^ back to top

---

Operations

Operational Requirements

During the mission, 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 Mission 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.

Operational Protocols

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.

^ back to top

---

Results/More Information

^ back to top

---

Related Web Sites

SSCO

RRM

^ back to top

---

Publications

^ back to top

---

Ground Based Results Publications

^ back to top

---

ISS Patent Publications

^ back to top

---

Related Publications

^ back to top

---

Images

This artistic representation shows ISS?s Dextre robot (right) performing a robotic refueling task on RRM (center), mounted to ELC4.

+ View Larger Image


In this artistic representation, the Wire Cutter and Blanket Manipulation Tool (right) approaches the RRM box (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.

+ View Larger Image


The RRM payload box 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.

+ View Larger Image


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
+ View Larger Image


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
+ View Larger Image


The Dextre robot (left) approaches the Robotic Refueling Mission module (on bottom platform, left side) to perform the Launch Lock Task. Image Credit: NASA
+ View Larger Image


With the International Space Station's accordion solar array in the background, the Dextre "OTCM" (at end of arm) uses its built-in cameras and lights to scan the Robotic Refueling Mission module during the Vision Task. This data will help develop machine vision algorithms against the harsh lighting on orbit, aiding future autonomous robotic operations beyond RRM. Image Credit: NASA
+ View Larger Image


The Wire Cutter Tool has the functionality of four: it grabs, it snips, it manipulates, and it slices. Image Credit: NASA/Chris Gunn
+ View Larger Image