Proceeding of the 6th International Symposium on Artificial Intelligence and Robotics & Automation in Space:
i-SAIRAS 2001, Canadian Space Agency, St-Hubert, Quebec, Canada, June 18-22, 2001.
SPACE SERVICING: PAST, PRESENT AND FUTURE
Dan King
MacDonald Dettwiler Space and Advanced Robotics, 9445 Airport Road, Brampton (On) L6S 4J3, Canada
[email protected]
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.
2.1
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.
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
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 2
Table 1: Canadarm Technical Details
Canadarm Key Parameters
Length:
Mass:
Speed of Movement:
15.2m
410 kg
Unloaded 60 cm/sec
Loaded 6 cm/sec
Wrist Joint:
Pitch/Yaw/Roll
Elbow Joint:
Pitch
Shoulder Joint:
Pitch/Yaw
Upper & Lower Arm Boom:
Composite Material
Rotational Hand Controller:
Pitch/Yaw/Roll
Translational Hand Controller: Left/Right/Up/Down/
Forward/Backward
Control/Sensing
Astronaut/Automatic
2.2
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 2001. 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.
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 22nd, 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.
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 3. First robotics "handshake" in space
between Canadarm and Canadarm2
Page 2
Table 2: Canadarm2 Technical Details
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.
Canadarm2 Key Parameters
Length:
Mass:
Average Power:
Peak Power:
Speed of Movement:
17.6m
1641 kg
1360W
2000W
Unloaded 37 cm/sec
Loaded 2-15 cm/sec
Stopping Distance:
0.6 m
Wrist Joint:
Pitch/Yaw/Roll
Elbow Joint:
Pitch
Shoulder Joint:
Pitch/Yaw/Roll
Joint Movements:
540 degrees
Upper & Lower Arm Boom:
Composite Material
(19 plies)
Boom Diameter:
35 cm
Cameras:
Four (4)
Rotational Hand Controller:
Pitch/Yaw/Roll
Translational Hand Controller: Left/Right/Up/Down/
Forward/Backward
Control/Sensing
Astronaut/Automatic
Force/Moment Control
Collision Avoidance
Other features
Identical on both ends
Built-in-redundancy
Repairable in space
(built in ORU sections)
2.3
Figure 4: ETS-VII launch configuration
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 28th , 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:
q
q
q
q
q
q
q
q
Figure 5: ETS-VII On-Orbit Experiments
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
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
3.1
European Robotics Arm (ERA)
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:
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 4: JEMRMS Technical Details
JEMRMS Key Parameters
Length:
Mass Handling:
Positioning Accuracy:
Speed:
Maximum Tip Force:
Wrist Joint:
Elbow Joint:
Shoulder Joint:
Rotational Hand Controller:
Translational Hand Controller:
Table 3: ERA Technical Details
ERA Key Parameters
Length:
Mass:
Speed of Movement:
Stopping Distance:
Wrist Joint:
Elbow Joint:
Shoulder Joint:
Control/Sensing
11.3m
630kg
0.2m/s maximum
0.15 m
Pitch/Yaw/Roll
Pitch
Pitch/Yaw
Astronaut/Automatic
Control/Sensing
9.9m
7000kg
+/- 50mm Translat.
+/- 1 deg Rotational
20-60mm/s
> 30N
Pitch/Yaw/Roll
Pitch
Pitch/Yaw
Pitch/Yaw/Roll
Left/Right/Up/Down/
Forward/Backward
Astronaut/Automatic
Figure 7: Japanese Experiment Module Remote
Manipulator System ("JEMRMS")
Figure 6: European Robotic Arm ("ERA")
3.3
3.2
Japanese Experiment Module Remote
Manipulator System (JEMRMS)
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
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
Page 4
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.
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 5 summarises some of the key ERA parameters:
Table 6: SPDM Technical Details
Table 5: RTSX Technical Details
RTSX Key Parameters
Overall Size (stowed):
Total Mass:
Two (2) 8 DOF Arms
Length:
Wrist Video Camera
One (1) 6 DOF Positioning Leg
Length:
One (1) 7 DOF video arm
Working Envelope:
Stereo cameras and LED lights
SPDM Key Parameters
Length:
Mass:
Average Power:
Peak Power:
Stopping Distance:
Wrist Joint (each arm):
Elbow Joint (each arm):
Shoulder Joint (each arm):
Body Joint:
Cameras:
Control/Sensing
40" X 30" X 96"
1500 lb
63" each
75"
55" radius
Other features
3.5m (each arm)
1662 kg
600W
2000W
0.15 m
Pitch/Yaw/Roll
Pitch
Pitch/Yaw/Roll
Roll
Three (3)
Astronaut/Automatic
Force/Moment Control
Collision Avoidance
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
4
would government or industry finance such clean-up
missions.
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?
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 100150 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).
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
Figure 9: Satellite Servicing
Page 6
trains, planes and automobiles have created new
economical opportunities for many parts of the world
in the 19th and 20th 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 XPrize is similar to the one won by Charles Lindberg at
the beginning of the 20th 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 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).
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
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", 5th ISAIRAS (ESA SP440). Also NASDA official ETS-VII website.
[2] Phillippe Schoonegans, Marc Oort "ERA, the
Flexible Robot Arm", 5th 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-1998-209006
Page 8