ISS Utilization: RRM (Robotic Refueling Mission)
RRM is a multi-phased ISS investigation, a joint effort of NASA and CSA (Canadian Space Agency) utilizing: SSRMS (Space Station Remote Manipulator System) or Canadarm2 and SPDM (Special Purpose Dexterous Manipulator) or Dextre . The primary goal is to advance robotic servicing technology by demonstrating the use of innovative robotic tools and techniques to remotely manipulate standard satellite interfaces that were not designed to be manipulated robotically. 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 that could benefit from such a service. 1) 2) 3) 4)
In 2009, SSCO (Satellite Servicing Capabilities Office) at NASA/GSFC initiated the development of the RRM program. 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. The prime contractor base consists of Lockheed Martin, Stinger Ghaffarian Technologies, Orbital Sciences Corporation, Alliant Techsystems, Jackson and Tull, and Arctic Slope Regional Corporation. The goal of the RRM program is to give NASA the confidence to robotically refuel, repair and maintain satellites in both near and distant orbits.
RRM consists of the "RRM module" and four RRM Tools (in the first phase of operations). The International Space Station's twin-armed Canadian Dextre robot acts as a skilled spacecraft refueling and servicing technician of an unprepared client satellite on ISS. The RRM payload consists of a task board that includes worksites hosting representative satellite interfaces for coolant, fuelling, electrical or power, and communications or diagnostics. In order for Dextre to perform the necessary tasks, specialized tools were required to act as interfaces between Dextre’s Orbital Replaceable Unit (ORU) Tool Change-Out Mechanisms (OTCMs) and the multiple worksite types integrated into the RRM. The four tools launched inside the RRM payload were designed to interface with Dextre’s OTCMs and the hardware they must manipulate.
During operations, controllers on the ground remotely control Dextre to reach into the RRM module and pick up RRM tools. Dextre then goes to work on RRM's components and activity boards, demonstrating such servicing tasks such as cutting and peeling back protective thermal blankets, unscrewing caps, turning valves, and transferring fluid. 5) 6)
RRM represents the first time the space station's Dextre robot was used for technology research and development, moving it beyond robotic maintenance of the orbiting superstructure.
The RRM module is about the size of a washing machine and weighs ~250 kg, with dimensions of 84 cm x 110 cm x 114 cm. RRM includes 1.7 liter of ethanol to demonstrate fluid transfer in orbit. Protective thermal blankets, caps, valves, simulated fuel, and other spacecraft components allow the team to practice a wide range of satellite-servicing tasks.
Figure 1: Photo of the RRM module (image credit: NASA)
Launch: RRM was launched on STS-135 ISS ULF7 flight of Atlantis (July 8-21, 2011, 13 day mission), representing the final Shuttle mission. The RRM module, an external ISS experiment, was part of the Raffaello MPLM (Multi-Purpose Logistics Module) payload on STS-135. 7) 8) 9)
• On July 13, 2011, the RRM module on the ISS was temporarily installed on the Dextre robot's Enhanced ORU Temporary Platform. 10)
Figure 2: Photo of the the RRM module temporarily installed on the Dextre robot's Enhanced ORU Temporary Platform (image credit: NASA) 11)
• On Sept. 2, 2011, Canadarm2 and the Dextre robot transferred the RRM to its permanent location on the ELC-4 [(ExPRESS (Expedite the Processing of Experiments to the Space Station) Logistics Carrier-4].
• On Sept. 6. 2011, the RRM module was successfully installed onto its permanent location on the International Space Station's ELC-4.
Figure 3: Photo of the RRM module installed on ELC-4 (image credit: NASA)
RRM was launched to the space station with four specialized and unique tools:
- WCT (Wire Cutter Tool)
- MFT (Multifunction Tool)
- SCT (Safety Cap Removal Tool)
- ENT (EVR Nozzle Tool)
The tools are stored in storage bays in RRM module until retrieved by the ISS Dextre Robot. Each tool has integrated cameras for ground operator vision and includes specialized features tailored to complete each unique task.
Figure 4: Illustration of the first set of tools provided for the Phase 1 tasks (image credit: NASA)
Figure 5: The MFT provides an interface with several adapters and the pressure valves (image credit: NASA)
RRM Phase 1 tasks:
Tasks required to refuel storable propellants in legacy spacecraft:
1) Take apart components (cut wire, manipulate thermal blankets and fasteners, remove caps)
2) Connect refueling hardware and transfer fluid
3) Reseal fuel port
The initial tasks required to replenish cryogens in existing satellites not designed for servicing.
- The first RRM experiment was conducted very successfully on March 7-9, 2012, marking important milestones in satellite-servicing technology and the use of the space station robotic capabilities. During the three-day RRM Gas Fittings Removal task, Dextre performed the most intricate task ever attempted by a space robot: cutting two separate "lock wires" of 0.5 mm in diameter using the RRM WCT (Wire Cutter Tool). Deftly maneuvered by ground-based mission operators and Dextre, the WCT smoothly slid its hook under the individual wires and severed them with only a few mm of clearance. This wire-cutting activity is a prerequisite to removing and servicing various satellite parts during any future in-orbit missions. 12)
- January 2013: The RRM tests from January 14-25 culminated in a first-of-its-kind robotic fluid transfer, a demonstration that could be a catalyst to expanded robotic satellite-servicing capabilities and lead to a greener, more sustainable space. NASA's RRM demonstrated remotely controlled robots using current-day technology could refuel satellites not designed to be serviced. 13)
- May 2013: The latest round of NASA's RRM (Robotic Refueling Mission) satellite-servicing tasks was completed on May 10, 2013. Five days of operations were held aboard the ISS, during which the Canadian-built Dextre robot with RRM tools demonstrated how tiny caps can be retrieved and stowed in space. This task, along with slicing through satellite blanket tape (MLI task) were performed on the RRM module affixed outside the space station. The conclusion of the May operations marked the end of the first phase of tasks (Phase 1) for RRM, a modular activity box with tools that launched to the space station aboard the final space shuttle flight. All objectives of the Phase 1 servicing tasks were successfully conducted, including the first ever in-space robotic refueling operation. 14) 15)
The results of RRM operations show that current-day robotic technology can refuel the common, triple-sealed satellite fuel valves of orbiting satellites (Ref. 13).
Figure 6: RRM configuration (image credit: NASA)
Launch: The HTV-4 ( H-II Transport Vehicle) of JAXA was launched on August 3, 2013 from TNSC (Tanegashima Space Center) in Japan with the new RRM hardware on board. HTV-4 was installed on its berthing port on the Earth-facing side of the International Space Station’s Harmony node on August 9, 2013, delivering a total of ~5400 kg of cargo to the ISS. 16)
The new RRM hardware of the HTV-4 consists of:
• ROTC (RRM On-orbit Transfer Cage) of NASA. ROTC is designed to transfer hardware outside of the space station. Astronauts will mount the ROTC on the sliding table within the Japanese airlock and then install the task board onto the ROTC, giving the Canadian Dextre robot an easy platform from which to retrieve and subsequently install the new hardware. The Phase 2 hardware complement on HTV-4 consists of: 17)
- Two new RRM TBs (Task Boards): TB3 and TB4. TB3 features new hardware to test cryogen replenishment, which includes five brand new adapters for the RRM MFT (Multi Function Tool). TB3 and TB4 will be transferred outside the ISS via a new piece of hardware also launching on HTV-4, called the ROTC (RRM On-orbit Transfer Cage).
- The ROTC (RRM On-orbit Transfer Cage): an original device developed by SSCO (Satellite Servicing Capabilities Office) of NASA/GSFC to transfer hardware outside of the International Space Station.
Figure 7: Phase 2 RRM task boards, task board 3 (left), task board 4 (right), image credit: NASA
Figure 8: Photo of the ROTC during launch preparations at NASA/GSFC (image credit: NASA)
A further launch in 2014 will deliver the VIPIR (Visual Inspection Poseable Invertebrate Robot) to the ISS for installation. VIPIR , another Phase 2 hardware device, is an SSCO-built borescope inspection tool that provides a set of eyes for internal satellite repair jobs.
RRM Phase 2 tasks:
Phase 2 of RRM began in August 2013 with the launch of the phase 2 RRM hardware to the ISS aboard the Japanese HTV-4 (H-II Transfer Vehicle 4). In its second phase, RRM is now moving on to demonstrate how a space robot can complete intermediate tasks required to replenish croygen in the instruments of "legacy" satellites: existing, orbiting spacecraft that were not designed to be serviced.
The RRM Phase 2 tasks consist of installing 2 new modular task boards onto the existing RRM experiment that was installed on the ISS ELC-4 (EXPRESS Logistics Carrier-4) in August 2011. The modular task boards are designed to mimic satellite interfaces that can be used in robotic servicing. The demonstrations on the task boards will reduce risks, refine techniques, and increase the reliability and technical proficiency of future robotic servicing missions.
The five RRM tasks consist of: 18)
1) Using existing robotic tools and new unique adapters, mechanically capture, remove, translate and Install a coolant line hose and bayonet into an open service line port
2) Using robotic tools, capture, remove, translate and install a vent plug into an open vent port, verify environment seal
3) Using robotic tools, capture, remove, translate and
- Stow an electrical loop back plug
- Install an electrical plug and check for electrical continuity
4) Using Robotic tools, capture, remove, translate and install an inspection camera onto an open tube. a) Deploy and articulate a stowed flexible inspection camera into the tube.
5) Using robotic tools, capture, remove, translate and install and latch a blind mate SMA plug into a recessed SMA receptacle box and check for electrical continuity.
1) Jill McGuire, “NASA’s Robotic Refueling Mission,” 2nd Annual ISS Research and Development Conference, Denver, CO, USA, July 16-18, 2013, URL: http://www.astronautical.org/sites/default/files/issrdc/2013/issrdc_2013-07-17-1600_mcguire.pdf
2) “Robotic Refueling Mission,” NASA; URL: http://ssco.gsfc.nasa.gov/images/RRM_Factsheet.pdf
3) Frank Cepollina, “Satellite Servicing and The Spirit of Innovation,” NASA, June 29, 2012, URL: http://www.goddard-contractors-association.org/presentations/GCA%20Satellite%20Servicing-Ceppi%202012June29.pdf
4) M. Caron, I. Mills, “Planning and Execution of Tele-Robotic Maintenance Operations on the ISS,” Proceedings of SpaceOps 2012, The 12th International Conference on Space Operations, Stockholm, Sweden, June 11-15, 2012, http://www.spaceops2012.org/proceedings/documents/id1272635-Paper-001.pdf
5) RRM (Robotic Refueling Mission),” NASA, August 10, 2013, URL: http://ssco.gsfc.nasa.gov/robotic_refueling_mission.html
6) Teri H. Gregory, Miles Newman, “Thermal Design Considerations of the Robotic Refueling Mission (RRM),” 41st International Conference on Environmental Systems, Portland, OR, USA, July 17-21, 2011, paper: AIAA 2011-5072
7) “STS-135 Press Kit: The Final Mission,” NASA, July 2011, URL: http://www.nasa.gov/pdf/566071main_STS-135_Press_Kit.pdf
8) Ken Kremer, “Revolutionary Robotic Refueling Experiment Opens New Research Avenues at Space Station,” Universe Today, July 16, 2011, URL: http://www.universetoday.com/87419/revolutionary-robotic-refueling
11) “Robotic Refueling Module, Soon To Be Relocated to Permanent Space Station Position,” NASA, August 16, 2011, URL: http://www.nasa.gov/topics/shuttle_station/features/rrm-issposition.html
13) “NASA's Successful Robotic Refueling Demo Points To a Bright Satellite-Servicing Future,” NASA, February 8, 2013, URL: http://www.nasa.gov/mission_pages/station/research/news/rrm_success.html
14) Adrienne Alessandro, “NASA's Robotic Refueling Mission Practices New Satellite-Servicing Tasks,”, NASA May 10, 2013, URL: http://www.nasa.gov/mission_pages/station/research/news/rrm_practice.html
15) Patric Blau, “Robotic Refueling Mission completes Phase I of Demonstrations,” Spaceflight 101, May 10, 2013, URL: http://www.spaceflight101.com/robotic-refueling-mission.html
16) “Japanese Cargo Craft Captured, Berthed to Station,” NASA, Aug. 9, 2013, URL: http://www.nasa.gov/content/station-crew-captures-japanese-cargo-craft/#.UgY3fazODWI
17) “It may be called the Robotic Refueling Mission (RRM), but NASA built RRM to demonstrate much more than just robotic satellite refueling,” NASA, Aug. 10, 2013, URL: http://ssco.gsfc.nasa.gov/rrm_phase2.html
18) “Robotic Refueling Mission Phase 2 (RRM-P2),” NASA Fact sheet, May 28, 2013, URL: http://www.nasa.gov/mission_pages/station/research/experiments/946.html
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.