SPACE SERVICING: PAST, PRESENT AND FUTURE. Dan King

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1 Proceeding of the 6 th International Symposium on Artificial Intelligence and Robotics & Automation in Space: i-sairas 2001, Canadian Space Agency, St-Hubert, Quebec, Canada, June 18-22, SPACE SERVICING: PAST, PRESENT AND FUTURE Dan King MacDonald Dettwiler Space and Advanced Robotics, 9445 Airport Road, Brampton (On) L6S 4J3, Canada dking@mdrobotics.ca ABSTRACT This paper examines the past achievements and current developments in space servicing, with a focus on enabling space robotics systems. As well, an attempt is made to predict future space servicing missions and applications that may help set the path for space robotic technologies development. 1 INTRODUCTION Ever since the dawn of the Space Programs, Space Servicing (also known as "On-Orbit Servicing") has motivated and captured the imagination of space enthusiasts and engineers alike for over four decades. As a general broad definition, Space Servicing encompasses such on-orbit activities as spacecraft-tospacecraft rendezvous, inspection and docking, payload and satellite deployment, manipulation, retrieval, resupply and repair; as well as satellite re-orbiting and de-orbiting. Many of the above space servicing tasks have already been performed by various automation and robotics systems, or by astronauts and cosmonauts. New robotics systems are currently being deployed that will further demonstrate those capabilities. All these will help support new opportunities and applications that are emerging in the horizon. 2 PAST DEVELOPMENT Many countries around the world has endeavoured in space robotics development, notably Japan, United States, Europe, Russia and Canada. Canada in particular has chosen space robotics as one of its strategic development areas and continues to make significant technology investments on such. where the translational and rotational hand controllers direct the movement of the arm. Although less utilised, the Canadarm can also be operated automatically using pre-programmed trajectories to complete specific manoeuvres for the arm. The key parameters of the Canadarm is summarised in Table 1. Over the past two decades, the Canadarm has enabled space servicing missions such as payload/satellite deployment, manoeuvering, servicing and retrieval, EVA astronaut assist, shuttle inspection and servicing, ORU manipulation, as well as on-orbit construction and assembly. Some of the more notable missions include the rescue of Westar and Palapa satellites, Hubble Servicing Missions and the current International Space Station (ISS) assembly missions. Unplanned exercises for the Canadarm have included knocking a block of ice from a clogged waste-water vent that might have endangered the shuttle upon reentry, pushing a faulty antenna into place, and successfully activating a satellite (using a swatter made for briefing covers) that failed to go into proper orbit. To-date, the Canadarm has performed flawlessly on all its missions. All four Canadarms in active duty have recently been upgraded in anticipation of the more challenging ISS assembly and operations missions. For example, all the Canadarm joints have been modified to enhance the payload handling capability to 100,000 kg, which gives the Canadarm the ability to berth the Shuttle itself to the ISS. The Canadarm is key to almost all ISS assembly missions and will remain an integral part of the U.S. shuttle fleet for many years to come. 2.1 Shuttle Remote Manipulator System Perhaps the most well known robotics system that has ever flown is the Shuttle Remote Manipulator System ("SRMS"), also known as the "Canadarm". Since its debut in 1981, The Canadarm has successfully flown more than 50 missions on the U.S. fleet of five Space Shuttles (including Challenger). The Canadarm is a six (6) degrees of freedom remote manipulator comprising of an upper and lower arm boom, an end effector, and a control workstation at the aft flight deck of the shuttle Figure 1: "Canadarm" Shuttle Remote Manipulator System on Hubble Servicing Mission

2 Table 1: Canadarm Technical Details Canadarm Key Parameters Length: 15.2m Mass: 410 kg Speed of Movement: Unloaded 60 cm/sec Loaded 6 cm/sec Wrist Joint: Elbow Joint: Shoulder Joint: /Yaw Upper & Lower Arm Boom: Composite Material Rotational Hand Controller: Translational Hand Controller: Left/Right/Up/Down/ Forward/Backward by an astronaut or the SPDM. Canadarm2 also has the additional features of four TV cameras that feed wide and close-up views to the operators, force moment sensing and control to enhance smooth robotics operations, collision-avoidance to ensure operational safety, and an advanced vision systems to track payloads. The key Canadarm2 paramaters is summarised in Table Space Station Remote Manipulator System Perhaps the most sophisticated space robotics system ever flown, the Space Station Remote Manipulator System ("SSRMS") was successfully launched, installed and checked-out on the recent STS-100 Mission in April Also known as "Canadarm2", the SSRMS is a seven (7) degrees of freedom metre long arm capable of handling large payloads of up to 100,000 kg mass, including the Shuttle itself. The 7 DOF configuration gives it a greater ability to bend, rotate and maneuver itself into difficult spots. Since Canadarm2 can almost fully rotate all of its joints, it is more agile than a human arm and provides a critical capability for the complex ISS operational environment. Unlike the Shuttle Canadarm, the ISS Canadarm2 is not permanently anchored at the shoulder joint but is equipped on either side with the same Latching End Effector (LEE) that can be used as anchor point while the opposite one performs various robotics tasks, including grabbing another connecting point on the ISS. This gives the Canadarm2 a unique capability to move around the ISS like an "inchworm", flipping end-over-end among Power Data Grapple Fixtures (PDGFs) located on the ISS. As well, the ISS will later be equipped with the Mobile Based System (MBS), which services as a storage location and work platform for astronauts; and the Mobile Transporter (MT), which can transport both Canadarm2 and the MBS from one end of the ISS main truss to another. This provides a second mode of mobility for Canadarm2. Also unlike the Shuttle Canadarm, the ISS Canadarm2 is designed to stay in space for more than 15 years. This requirement necessitates an innovative design feature which allows astronauts or other robotics systems (such as the Special Purpose Dexterous Maniplator or "SPDM" that will be described in a later section) to repair Canadarm2 on-orbit. Canadarm2 is build in sections called Orbital Replaceable Units (ORU's) which are easily removed and then replaced Figure 2: "Canadarm2" International Space Station Remote Manipulator System The Canadarm2 was successfully installed on the ISS by Canadian astronaut Chris Hatfield and his fellow astronaut Scott Parazynski on April 22 nd, 2001 and within days, broke some new ground for Space Servicing. The first "inchworm" manoeuvre was successfully executed when Canadarm2 grasped a PDGF on the U.S. "Destiny" lab module and step out of its launch pallet transferring its anchor point from one hand to the other - taking its first maiden step on ISS. As well, near the end of the STS-100 mission, Canadarm2 picked up its launch pallet still attached to ISS and passed it back to the Shuttle's Canadarm, thereby completing the first robotics "handshake" in space (Figure 2). Canadarm2 is now fully operational on the ISS to fulfil its critical mission of ISS assembly and operations. Figure 3. First robotics "handshake" in space between Canadarm and Canadarm2 Page 2

3 Table 2: Canadarm2 Technical Details Canadarm2 Key Parameters Length: 17.6m Mass: 1641 kg Average Power: 1360W Peak Power: 2000W Speed of Movement: Unloaded 37 cm/sec Loaded 2-15 cm/sec Stopping Distance: 0.6 m Wrist Joint: Elbow Joint: Shoulder Joint: Joint Movements: 540 degrees Upper & Lower Arm Boom: Composite Material (19 plies) Boom Diameter: 35 cm Cameras: Four (4) Rotational Hand Controller: Translational Hand Controller: Left/Right/Up/Down/ Forward/Backward Force/Moment Control Collision Avoidance Other features Identical on both ends Built-in-redundancy Repairable in space (built in ORU sections) The ETS-VII experiments along with NASDA's earlier Manipulator Flight Demonstration (MFD) on STS-85 not only helped validate some of the specific Japanese space robotics technologies, but also provided the world space robotics community at large valuable insights into the challenges and solutions for space servicing in general. Figure 4: ETS-VII launch configuration 2.3 ETS-VII Unlike the Canadarm or Canadarm2 which were built for servicing new infrastructures in space (i.e. Shuttle and ISS), the ETS-VII mission (Ref.1) was flown by NASDA as a testing ground for robotics and space servicing technologies. The ETS-VII satellite was launched on November 28 th, 1997 and successfully conducted a series of rendezvous, docking and space robotic technology experiments. Some of the key experiments executed by the ETS-VII mission include: Visual inspection of on-board equipment by robotic vision system Handling of orbital replacement unit (ORU) and fuel (simulated) supply experiment Handling of small equipment by ETS-VII small robot arm including the use of a taskboard handling tool Handling of truss structure Antenna assembly experiment Ground teleoperation of ETS-VII robot Handling and berthing of the 410kg ETS-VII target satellite with ETS-VII robot on chaser satellite Rendezvous and docking by the ETS-VII chaser satellite with the ETS-VII target satellite Figure 5: ETS-VII On-Orbit Experiments 3 PRESENT DEVELOPMENT The next few years will promise to be very exciting for the space servicing community at large, with several new robotics systems currently under final development and scheduled to be flown. This includes the European Robotics Arm (ERA), the Japanese Experiment Module Remote Manipulator System (JEMRMS), the U.S. Ranger Telerobotic Shuttle Experiment and the Canadian Special Purpose Dexterous Manipulator System (SPDM). Page 3

4 3.1 European Robotics Arm (ERA) The European Robotics Arm (ERA) (Ref.2) is being built for use on the Russian Segment of the International Space Station. It consists of an 11 meter, six (6) degrees of freedom arm, an EVA Man Machine interface, an IVA Man Machine interface, a Refresher Trainer (RTR) and a Mission Preparation and Training Equipment (MPTE). Like Canadarm2, the ERA has a relocating capability by "hopping" from one power and communication interface basepoint to another on the Russian ISS segment. Table 3 summarises some of the key ERA parameters: Table 3: ERA Technical Details ERA Key Parameters Length: 11.3m Mass: 630kg Speed of Movement: 0.2m/s maximum Stopping Distance: 0.15 m Wrist Joint: Elbow Joint: Shoulder Joint: /Yaw JEM. A dexterous tool called the JEM Small Fine Arm (SFA) is also under development, which could be picked up by the JEM RMS to perform finer ORU servicing and maintenance. Table 4 summarises some of the key JEMRMS parameters: Table 4: JEMRMS Technical Details JEMRMS Key Parameters Length: 9.9m Mass Handling: 7000kg Positioning Accuracy: +/- 50mm Translat. +/- 1 deg Rotational Speed: 20-60mm/s Maximum Tip Force: > 30N Wrist Joint: Elbow Joint: Shoulder Joint: /Yaw Rotational Hand Controller: Translational Hand Controller: Left/Right/Up/Down/ Forward/Backward Figure 7: Japanese Experiment Module Remote Manipulator System ("JEMRMS") Figure 6: European Robotic Arm ("ERA") 3.2 Japanese Experiment Module Remote Manipulator System (JEMRMS) The Japanese Experiment Module Remote Manipulator System (JEMRMS) (Ref.3) is being built for use on the JEM Exposed Facility of the International Space Station. It consists of a 10 meter, six (6) degrees of freedom arm and a robotics control workstation within 3.3 RANGER Telerobotic Shuttle Experiment (RTSX) The Ranger Telerobotic Shuttle Experiment (RTSX) (Ref.4) is a 48 hour Space Shuttle-based flight experiment to demonstrate key telerobotic technologies for servicing assets in Earth orbit. Ranger is a four manipulator telerobot with one permanently attached to a Spacelab pallet. The manipulators perform dexterous manipulation, body repositioning, and stereo video viewing The flight system will be teleoperated from Page 4

5 onboard the Space Shuttle and from a ground control station at the NASA Johnson Space Center. The robot, along with supporting equipment and tasks elements, will be attached to a spacelab pallet carrier within the Shuttle payload bay. Table 5 summarises some of the key ERA parameters: Table 5: RTSX Technical Details RTSX Key Parameters Overall Size (stowed): 40" X 30" X 96" Total Mass: 1500 lb Two (2) 8 DOF Arms Length: 63" each Wrist Video Camera One (1) 6 DOF Positioning Leg Length: 75" One (1) 7 DOF video arm Working Envelope: 55" radius Stereo cameras and LED lights maintenance or upgrade. Alternatively the SPDM can be picked up by the free end of Canadarm2 and maneuvered into position next to the payload to be serviced. Table 6 summarises some of the key SPDM parameters: Table 6: SPDM Technical Details SPDM Key Parameters Length: 3.5m (each arm) Mass: 1662 kg Average Power: 600W Peak Power: 2000W Stopping Distance: 0.15 m Wrist Joint (each arm): Elbow Joint (each arm): Shoulder Joint (each arm): Body Joint: Roll Cameras: Three (3) Force/Moment Control Collision Avoidance Other features Built-in-redundancy Repairable in space (built in ORU sections) Figure 8: Ranger Telerobotic Shuttle Experiment (RTSX) 3.4 Special Purpose Dexterous Manipulator ("SPDM") The Special Purpose Dexterous Manipulator ("SPDM") is being built for carrying delicate maintenance and servicing tasks on the International Space Station. Its fifteen (15) degrees of freedom dual-arm configuration makes it highly dexterous and can undertake tasks such as installing, removing and servicing small payloads and ORUs. The SPDM is also equipped with lights, video equipment, a tool platform and four tool holders. The SPDM will normally sit on the Mobile Base System (MBS) and the ISS Canadarm2 will manipulate a payload to within the range of the SPDM for repair, Figure 9: Special Purpose Dexterous Manipulator System ("SPDM") Page 5

6 4 FUTURE MISSIONS As has been described in previous sections of this paper, a tremendous amount of experience and heritage has been acquired by the space servicing community at large with robotics missions on the Shuttle, ISS and experimental satellites. The logical question that comes to everyone's mind is: What Next? Indeed, the space servicing robotics community may have reached a crossroad: the transition from government dominated space servicing missions to commercial ones. Just as when Arthur C. Clarke conceived the idea of Geostationary Satellite Communications over half a century ago, it was probably hard for him then to imagine the bustling commercial satellite communications markets that exist today: a multi-billion a year market that includes Direct-To-Home broadcasting to millions of viewers throughout the world, Global Personal Communications, Live Messaging and Broadband Internet Access. Similarly, it was hard to imagine a decade or two ago how remote sensing data from satellites could impact each of our daily lives. From commercial fishing to agriculture to navigation to property assessment, such are the commercial applications that continues to transform the remote sensing sector from government to commercial applications. Similarly, those of us who have been associated with space robotics projects have for years dreamt of the emergence of a viable market for commercial on-orbit servicing. Much as the pioneers of the satellite communications and remote sensing enthusiasts have experienced in the past, we have "toyed" with and struggled through studies, demonstrations and ideas for potential commercial concepts such as satellite servicing (Figure 10) and space debris clean-up. The former concept remains commercially challenging as both servicing vehicles and target satellites to be serviced have equal access to advancement in launch and satellite technologies. Fundamentally if the cost of embarking on a servicing mission and an orbital asset replacement mission is equivalent then the value of the servicing mission becomes questionable. Only in cases where the relative cost of the servicing mission is much lower than that of the "serviced" asset (eg. ISS resupply and servicing) will the mission become economically attractive. The commercial challenges associated with orbital debris removal, on the other hand, faces the same issue that has plagued environment remediation on Earth. The fundamental question to be addressed is - who pays? Only until such time when there is a true financial or safety penalty caused by space debris would government or industry finance such clean-up missions. Fortunately there are recent indications that we may be turning the corner for other emerging markets for space servicing. For the first time in space history, the U.S. Underwriters Associations, a consortium of insurance underwriters, issued a RFP in 1999 for the rescue of the ORION 3 commercial communications satellite. ORION 3 was stranded in an elliptical low earth orbit in April 1999 when a Delta III upper stage malfunctioned and failed to inject it into the Geo Transfer Orbit. Although there has yet been a "rescue" deal signed for the mission to-date, it marks the beginning of a demand for commercial satellite rescue services. Boeing Satellite Systems (formerly part of Hughes) is already embarking on a growing business of taking damaged satellites abandoned by their owners and turning them into money makers starting with AsiaSat3 in 1998 and recently with PanAmSat s Galaxy 4 satellite. Meanwhile, you and I can now book a seat with Space Adventures Inc. (SAI) as a space tourist (for about US$100,000 per person) to experience a few minutes of microgravity at about km altitude. Accordingly to SAI there are already in excess of a hundred people who has registered for such an experience, which is expected to begin service a few years from now. Indeed, Mr. Dennis Tito became the world's first space tourist in April 2001 when he paid US$20M to fly on board a Russian Soyuz and spent a week on the Russian segment of the International Space Station (Figure 11). Figure 9: Satellite Servicing Page 6

7 Figure 10: Denis Tito - World's First Space Tourist Targeting a similar market, major corporations such as Hilton and Shimizu have already derived plans and blue prints for building orbiting space hotels (Figure 12). Accordingly to a recent NASA study, the Space Travel and Entertainment Market alone can easily develop into a multi-billion dollar per year industry. Other new commercial space industries that have been identified by NASA for the next millennium include Space Based Solar Power (Figure 13), Space FedEx Service, Space Based Manufacturing and Space Resources Mining (Ref.5). trains, planes and automobiles have created new economical opportunities for many parts of the world in the 19 th and 20 th centuries, space transportation development promises to create a similar outcome. To that end, NASA has just initiated a US$4.5B Space Launch Initiative (SLI) that promises to lower the cost of space access by an Order of Magnitude from what they are today. The start of SLI is synonymous to NASA initiating the Saturn Rocket Development Program in 1958 and the Shuttle Development Program in 1972, which underlines NASA s resolve to lower the cost of access to space for all and to help create a viable commercial space market. Apart from NASA s efforts, the private industry is also playing its role by creating the US$10M X-Prize which will be awarded to the first private team that can build and fly a reusable spaceship capable of carrying three individuals on a sub-orbital flight. The idea for the X- Prize is similar to the one won by Charles Lindberg at the beginning of the 20 th century which had been followed by a century of rapidly growing commercial activities in the civil aviation industry. Similarly, it is hoped that the X-Prize will help promote a new civil space industry in the 21 st century. Figure 11: Concept for Space "Hilton" Figure 12: Space Based Solar Power So what is required to help open up such commercial markets that will involve space servicing? Well you might have guessed it - one of the key secret ingredients is Low Cost Access to Space. Much as Page 7

8 5 CONCLUSIONS As has been demonstrated by the Canadarm and other space servicing systems and experiments in the past two decades, the complex on-orbit tasks that could be performed by automation and robotics technologies is tremendous. Given the general desire to pursue commercial applications for future Space Servicing missions, it is anticipated that the next generation space servicing systems will require higher operational efficiency in an increasingly unstructured work environment. This will demand technologies that support autonomous and semi-autonomous operations with as little human-inthe-loop intervention as possible. Adaptive robotics interfaces to handle non-cooperative and uncooperative payloads, as well as intelligent vision and control systems, will be required to support such challenging space servicing tasks. All these development will be geared towards lowering the cost and increasing reliability of any space servicing mission. Given my personal optimism for the future in space servicing, I would like to make a humble suggestion to space robotics enthusiasts around the world: keep up the good work, have faith and be creative because the best opportunities have yet to come. 6 REFERENCES [1] Yoshiaki OHKAMI, Mitsushige ODA, "NASDA's activities in space robotics", 5 th ISAIRAS (ESA SP- 440). Also NASDA official ETS-VII website. [2] Phillippe Schoonegans, Marc Oort "ERA, the Flexible Robot Arm", 5 th ISAIRAS (ESA SP-440). Also ESA official ISS website. [3] NASDA official JEM website [4] Joseph Parrish, "The Ranger Telerobotic Shuttle Experiment: An On-Orbit Satellite Servicer", 5 th ISAIRAS (ESA SP-440). Also University of Maryland "Ranger" official website. [5] D.V. Smitherman, "New Space Industries for the Next Millennium", NASA/CP Page 8