U.S. patent application number 13/196750 was filed with the patent office on 2012-05-10 for satellite refuelling system and method.
This patent application is currently assigned to MACDONALD DETTWILER & ASSOCIATES INC.. Invention is credited to Derry CRYMBLE, Lawrence GRYNIEWSKI, John Cameron OWER.
Application Number | 20120112009 13/196750 |
Document ID | / |
Family ID | 39758947 |
Filed Date | 2012-05-10 |
United States Patent
Application |
20120112009 |
Kind Code |
A1 |
GRYNIEWSKI; Lawrence ; et
al. |
May 10, 2012 |
SATELLITE REFUELLING SYSTEM AND METHOD
Abstract
The present invention provides a method, system and apparatus
for robotic refuelling of satellites. The system may include a
dedicated refuelling satellite launched directly from either earth,
or alternatively it could be launched from another larger mother
spacecraft or space station in which the refuelling satellite is
ferried into space in the case of the larger space craft or it may
be stored on the space station until needed from which it can be
launched. The system includes a robotic arm, suitable tools which
can be affixed to the end effector of the robotic arm required for
accessing, opening and closing the fuel fill valve on the satellite
being serviced, storage and retrieval stations on a tool caddy on
which the tools and various fuel fill valve caps are stored. The
system is under teleoperation by a remotely located operator, for
example located on earth, in the mother station or in the space
station. Cameras are included focussed on the robotic arm and end
effector and images are transmitted to the operator to allow the
operator to direct and control the refuelling procedure. The system
may also be configured to be operated autonomously under computer
control.
Inventors: |
GRYNIEWSKI; Lawrence;
(Mississauga, CA) ; CRYMBLE; Derry; (Toronto,
CA) ; OWER; John Cameron; (Oakville, CA) |
Assignee: |
MACDONALD DETTWILER &
ASSOCIATES INC.
Brampton
CA
|
Family ID: |
39758947 |
Appl. No.: |
13/196750 |
Filed: |
August 2, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12073795 |
Mar 10, 2008 |
8074935 |
|
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13196750 |
|
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60905827 |
Mar 9, 2007 |
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Current U.S.
Class: |
244/172.2 ;
901/41; 901/46 |
Current CPC
Class: |
B67D 2007/0417 20130101;
B64G 1/1078 20130101; B64G 1/402 20130101; B25J 11/00 20130101;
B64G 4/00 20130101; B67D 2007/0403 20130101; B64G 5/00 20130101;
B64G 1/14 20130101; B67D 2007/0432 20130101; B67D 2007/0405
20130101 |
Class at
Publication: |
244/172.2 ;
901/41; 901/46 |
International
Class: |
B64G 1/22 20060101
B64G001/22 |
Claims
1. A method of transferring fluid from a servicer spacecraft to a
client spacecraft, said client spacecraft including a tank and a
fluid port coupled to said tank, said fluid port including a fluid
valve, said fluid valve including a valve actuation nut for opening
and closing said fluid valve, said fluid being selected from the
group consisting of fuel and oxidizer, the method comprising:
instructing a robotic arm on said servicer spacecraft to perform
the steps of: removing an access valve cap on said fluid valve;
attaching a fluid line to said fluid valve; and opening said fluid
valve by actuating said valve actuation nut, thereby transferring
fluid into said tank.
2. The method of claim 1, wherein said step of removing said access
valve cap is performed by: affixing an access valve cap removal
tool to a distal end of said robotic arm, and engaging said access
valve cap removal tool to detach said access valve cap.
3. The method of claim 2, wherein subsequent to said step of
removing said access valve cap, the method further includes the
step of: removing and storing said access valve cap removal
tool.
4. The method of claim 1, wherein said step of removing said access
valve cap is performed by: affixing a valve tool to a distal end of
said robotic arm, affixing an access valve cap removal tool said
valve tool, and engaging said access valve cap removal tool to
detach said access valve cap.
5. The method of claim 2, wherein subsequent to said step of
removing said access valve cap, the method further includes the
step of: storing said access valve cap; and removing and storing
said access valve cap removal tool.
6. The method of claim 5, wherein said step of attaching said fluid
line is performed by: affixing a valve tool having said fluid line
to said distal end, and coupling said fluid line to said fluid
valve.
7. The method of claim 6, wherein said step of opening said fluid
valve is performed by engaging said valve tool to actuate said
valve actuation nut.
8. The method of claim 7, further including the step of: closing
said fluid valve by engaging said valve tool to actuate said valve
actuation nut.
9. The method of claim 7, further including the step of: clamping
said valve tool to a reaction area on said fluid valve, and closing
said fluid valve by engaging said valve tool to actuate said valve
actuation nut.
10. The method of claim 5, wherein said step of attaching said
fluid line is performed by: affixing a valve tool to said distal
end of said robotic arm, affixing said fluid line to said valve
tool, and coupling said fluid line to said fluid valve.
11. The method of claim 10, wherein said step of opening said fluid
valve is performed by engaging said valve tool to actuate said
valve actuation nut.
12. The method of claim 5, wherein said step of attaching said
fluid line is performed by: affixing a valve tool having said fluid
line to said distal end, clamping said valve tool to a reaction
area on said fluid valve, and coupling said fluid line to said
fluid valve.
13. The method of claim 1, wherein said step of removing said
access valve cap is performed by: affixing a valve tool to a distal
end of said robotic arm, clamping said valve tool to a reaction
area on said fluid valve, and engaging said valve tool to detach
said access valve cap.
14. The method of claim 13, further including the step of: removing
and storing said valve tool.
15. The method of claim 1, wherein subsequent to said step of
removing said access valve cap, the method further includes the
step of: storing said access valve cap.
16. The method of claim 15, wherein said step of storing said
access valve cap is performed by: clamping said robotic arm to a
reaction area on a storage post and attaching said access valve cap
to said storage post.
17. The method of claim 16, wherein said step of attaching said
access valve cap is performed by: rotating said access valve cap in
a tightening direction.
18. The method of claim 1, further including the step of: closing
said fluid valve.
19. The method of claim 18, wherein said step of closing said fluid
valve is performed by actuating said valve actuation nut.
20. The method of claim 18, wherein said step of closing said fluid
valve is performed by: clamping said robotic arm to a reaction area
on said fluid valve and actuating said valve actuation nut.
21. The method of claim 1, wherein said step of opening said fluid
valve is performed by clamping said robotic arm to a reaction area
on said fluid valve and rotating said valve actuation nut in a
first direction.
22. The method of claim 21, further including the step of: closing
said fluid valve by clamping said robotic arm to said reaction area
and rotating said valve actuation nut in a second direction
opposite to said first direction.
23. The method of claim 1, wherein said step of removing said
access valve cap is performed by clamping said robotic arm to a
reaction area on said fluid valve and detaching said access valve
cap from said fluid valve.
24. The method of claim 23, wherein said step of detaching said
access valve cap is performed by rotating said access valve cap in
a loosening direction.
25. The method of claim 1, wherein said step of attaching said
fluid line is performed by clamping said robotic arm to a reaction
area on said fluid valve and coupling said fluid line to said fluid
valve.
26. The method of claim 1, further including the step of: detaching
said fluid line from said fluid valve.
27. The method of claim 26, wherein said step of detaching said
fluid line is performed by clamping said robotic arm to a reaction
area on said fluid valve and de-coupling said fluid line from said
fluid valve.
28. The method of claim 26 wherein, subsequent to said step of
detaching said fluid line, the method further includes the step of:
replacing said access valve cap onto said fluid valve.
29. The method of claim 1, further including the step of: closing
said fluid valve by actuating said valve actuation nut; and
detaching said fluid line from said fluid valve.
30. The method of claim 29 wherein said step of closing said fluid
valve and said step of detaching said fluid line are each performed
while said robotic arm is clamped to a reaction area on said fluid
valve.
31. The method of claim 29, wherein said step of removing said
access valve cap, said step of attaching said fluid line, said step
of opening said fluid valve, said step of closing said fluid valve,
and said step of detaching said fluid line, are each performed
while said robotic arm is clamped to a reaction area on a storage
post.
32. The method of claim 1 wherein, prior to said step of opening
said fluid valve, the method further includes the step of: cutting
a lockwire on said valve actuation nut.
33. The method of claim 32 wherein said step of cutting said
lockwire is performed by: affixing a wire cutter tool on a distal
end of said robotic arm, and engaging said wire cutter tool to cut
said lockwire.
34. The method of claim 1 wherein, prior to said step of opening
said fluid valve, the method further includes the step of: sensing
the presence of a lockwire on said valve actuation nut, and if said
lockwire is sensed, cutting said lockwire.
35. The method of claim 34, wherein said sensing is performed by
transmitting visual images of a region of said client spacecraft to
a teleoperator remote from said servicer spacecraft via a user
interface.
36. The method of claim 1 wherein, prior to said step of removing
said access valve cap, the method further includes the step of:
cutting a lockwire on said access valve cap.
37. The method of claim 36 wherein, said step of cutting said
lockwire is performed by: affixing a wire cutter tool on a distal
end of said robotic arm, and engaging said wire cutter tool to cut
said lockwire.
38. The method of claim 1 wherein, prior to said step of removing
said access valve cap, the method further includes the step of:
sensing the presence of a lockwire on said access valve cap, and if
said lockwire is sensed, cutting said lockwire.
39. The method of claim 38, wherein said sensing is performed by
transmitting visual images of a region of said client spacecraft to
a teleoperator remote from said servicer spacecraft via a user
interface.
40. The method of claim 1, wherein, prior to said step of removing
said access valve cap, the method further including the step of
cutting a lockwire on said access valve cap; and wherein, prior to
said step of opening said fluid valve, the method further including
the step of cutting a lockwire on said valve actuation nut.
41. The method of claim 1 wherein, prior to said step of removing
said access valve cap, the method further includes the step of:
removing an outer cap covering said fluid valve.
42. The method of claim 1 wherein, prior to said step of removing
said access valve cap, the method further includes the step of:
sensing the presence of an outer cap covering said fluid valve, and
if said outer cap is sensed, removing said outer cap.
43. The method of claim 42, wherein said sensing is performed by
transmitting visual images of a region of said client spacecraft to
a teleoperator remote from said servicer spacecraft via a user
interface.
44. The method of claim 1 wherein, prior to said step of removing
said access valve cap, the method further includes the step of:
cutting a lockwire on an outer cap covering said fluid valve, and
removing said outer cap.
45. The method of claim 1 wherein, prior to said step of removing
said access valve cap, the method further includes the step of:
sensing the presence of a lockwire on an outer cap covering said
fluid valve, and if said lockwire and said outer cap are sensed,
cutting said lockwire and removing said outer cap.
46. The method of claim 45, wherein said sensing is performed by
transmitting visual images of a region of said client spacecraft to
a teleoperator remote from said servicer spacecraft via a user
interface.
47. The method of claim 1 wherein, prior to said step of removing
said access valve cap, the method further includes the step of:
affixing a cap removal tool to a distal end of said robotic arm,
and removing an outer cap covering said fluid valve.
48. The method of claim 1 wherein, prior to said step of removing
said access valve cap, the method further includes the step of:
affixing a cap removal tool to a distal end of said robotic arm,
removing an outer cap covering said fluid valve, removing said cap
removal tool from said distal end, affixing a wire cutter tool to
said distal end, cutting a lockwire on said access valve cap, and
removing said wire cutter tool from said distal end.
49. The method of claim 1 wherein, prior to said step of removing
said access valve cap, further including the step of: cutting an
access opening in a thermal blanket encasing said fluid valve.
50. The method of claim 1 wherein, prior to said step of removing
said access valve cap, further including the step of: sensing the
presence of a thermal blanket encasing said fluid valve, and if
said thermal blanket is sensed, cutting an access opening in said
thermal blanket.
51. The method of claim 50, wherein said sensing is performed by
transmitting visual images of a region of said client spacecraft to
a teleoperator remote from said servicer spacecraft via a user
interface.
52. The method of claim 1 wherein, prior to said step of removing
said access valve cap, further including the step of: affixing a
blanket cutter tool to a distal end of said robotic arm; cutting an
access opening in a thermal blanket encasing said fluid valve; and
removing and storing said blanket cutter tool.
53. The method of claim 1 wherein, subsequent to said step of
closing said fluid valve, the method further includes the step of:
venting any excess fluid in said fluid line away from said client
spacecraft.
54. The method of claim 53 wherein said step of venting said any
excess fluid is performed by routing said any excess fluid into a
plenum filled substantially with vacuum, pressurizing said plenum
with a gas, and opening said plenum to vent away from said client
spacecraft.
55. The method of claim 53 wherein said step of venting said any
excess fluid is performed by opening a plenum to outer space;
routing said any excess fluid into said plenum, pressurizing said
plenum with a gas, and opening said plenum to vent away from said
client spacecraft.
56. The method of claim 55, wherein said gas is helium.
57. The method of claim 1, wherein prior to said step of removing
said access valve cap, the method further includes the steps of:
sensing the presence of a thermal blanket encasing said fluid
valve, and if said thermal blanket is sensed, cutting an access
opening in said thermal blanket; sensing the presence of an outer
cap covering said fluid valve, and if said outer cap is sensed,
removing said outer cap; and sensing the presence of a lockwire on
said access valve cap, and if said lockwire is sensed, cutting said
lockwire.
58. The method of claim 57, wherein said sensing is performed by
transmitting visual images of a region of said client spacecraft to
a teleoperator remote from said servicer spacecraft via a user
interface.
59. The method of claim 1, wherein tools may be mounted to a distal
end of said robotic arm, and wherein said step of removing said
access valve cap, said step of attaching said fluid line, said step
of opening said fluid valve, are each performed by one or more
tools mounted on said distal end of said robotic arm.
60. The method of claim 29, wherein tools may be mounted to a
distal end of said robotic arm, and wherein said step of removing
said access valve cap, said step of attaching said fluid line, said
step of opening said fluid valve, said step of closing said fluid
valve, and said step of detaching said fluid line, are each
performed by one or more tools mounted on said distal end of said
robotic arm.
61. The method of claim 1, wherein prior to said step of removing
said access valve cap, the method includes the step of affixing a
valve tool to a distal end of said robotic arm; wherein said step
of removing said access valve cap is performed by said valve tool;
wherein said step of attaching said fluid line to said fluid valve
is performed by said valve tool; and wherein said step of opening
said fluid valve is performed by said valve tool.
62. The method of claim 61, further including the step of: closing
said fluid valve with said valve tool.
63. The method of claim 62, further including the step of: removing
and storing said valve tool.
64. The method of claim 1, wherein prior to said step of removing
said access valve cap, the method includes the step of affixing a
valve tool to a distal end of said robotic arm; wherein said step
of attaching said fluid line is performed by: affixing a fluid line
coupling to said valve tool; engaging said fluid line coupling
connected to said fluid line with said fluid valve; wherein said
step of opening said fluid valve is performed by said valve
tool.
65. The method of claim 64, wherein said step of removing said
access valve cap is performed by: affixing an access valve cap
removal tool to said valve tool; removing said access valve cap
with said access valve cap removal tool; and removing said access
valve cap removal tool from said valve tool.
66. The method of claim 64, wherein said step of removing said
access valve cap is performed by: affixing an access valve cap
removal tool to said valve tool; removing said access valve cap
with said access valve cap removal tool; storing said access valve
cap; removing said access valve cap removal tool from said valve
tool; wherein the method further includes the steps of: closing
said fluid valve; removing said fluid line coupling from said valve
tool; affixing said access valve cap removal tool to said valve
tool; retrieving the stored said access valve cap with said access
valve cap removal tool; and mounting said access valve cap onto
said fluid valve.
67. The method of claim 1, wherein said robotic arm is controlled
by a teleoperation system configured for remote operation with a
human teleoperator issuing commands via a user interface.
68. The method of claim 1, wherein said robotic arm is controlled
by a mixed autonomous/teleoperation control system including: a
computer controller programmed to operate some or all of the fluid
transfer operations, and a teleoperation system configured to have
a human teleoperator remotely operate some or all of the fluid
transfer operations through a user interface, and wherein said
mixed autonomous/teleoperation control system is configured to work
in any one of three modes, including a first autonomous mode in
which the computer controller controls all fluid transfer
operations, a second teleoperation mode in which said human
teleoperator remotely operates said robotic arm through said user
interface to control all fluid transfer operations, and a third
supervised autonomy mode in which said robotic arm is autonomously
operated but all autonomous operations are monitored, can be halted
and must be approved by a human operator.
69. A method of transferring fluid from a servicer spacecraft to a
client spacecraft, said client spacecraft including a tank and a
fluid port coupled to said tank, said fluid port including a fluid
valve, said fluid valve including a valve actuation nut for opening
and closing said fluid valve, said fluid being selected from the
group consisting of fuel and oxidizer, the method comprising:
instructing a robotic arm on said servicer spacecraft to perform
the steps of: retrieving an access valve cap removal tool and
mounting same to a distal end of said robotic arm; engaging said
access valve cap removal tool to remove an access valve cap on said
fluid valve; detaching and storing said access valve cap removal
tool; retrieving a fluid line coupling and mounting said fluid line
coupling to said distal end of said robotic arm; coupling said
fluid line coupling to said fluid valve; and opening said fluid
valve by actuating said valve actuation nut, thereby transferring
fluid into said tank.
70. The method of claim 69, wherein a valve tool is mounted on said
robotic arm such that said distal end of said robotic arm is an end
of said valve tool.
71. The method of claim 70, wherein said step of opening said fluid
valve is performed by engaging said valve tool to actuate said
valve actuation nut.
72. The method of claim 69, wherein a valve tool is mounted on said
robotic arm such that said fluid line coupling is affixed to said
valve tool.
73. The method of claim 72, wherein said step of opening said fluid
valve is performed by engaging said valve tool to actuate said
valve actuation nut.
74. The method of claim 69, wherein a valve tool is mounted on said
robotic arm such that said access valve cap removal tool and said
fluid line coupling are affixed to said valve tool.
75. The method of claim 74, wherein said step of opening said fluid
valve is performed by engaging said valve tool to actuate said
valve actuation nut.
76. The method of claim 69, further including the steps of: closing
said fluid valve; detaching and storing said fluid line
coupling.
77. The method of claim 76, wherein prior to said step of
retrieving said access valve cap removal tool, the method further
includes the steps of: retrieving and mounting a wire cutter tool
to said distal end of said robotic arm; cutting a wire on said
access valve cap; and detaching and storing said wire cutter
tool.
78. The method of claim 69, further including the steps of:
retrieving and mounting a wire cutter tool to said distal end of
said robotic arm; cutting a wire on said valve actuation nut; and
detaching and storing said wire cutter tool.
79. The method of claim 76, wherein prior to said step of
retrieving said access valve cap removal tool, the method further
includes the steps of: retrieving and mounting a wire cutter tool
to said distal end of said robotic arm, cutting a wire on an outer
cap covering said fluid valve, and detaching and storing said wire
cutter tool; retrieving and mounting an cap removal tool to said
distal end of said robotic arm, removing said outer cap, and
detaching and storing said cap removal tool.
80. The method of claim 76, wherein prior to said step of
retrieving said access valve cap removal tool, the method further
includes the steps of: retrieving and mounting a wire cutter tool
to said distal end of said robotic arm, cutting a wire on an outer
cap covering said fluid valve, and detaching and storing said wire
cutter tool; retrieving and mounting a cap removal tool to said
distal end of said robotic arm, removing said outer cap, and
detaching and storing said cap removal tool; and retrieving and
mounting said wire cutter tool to said distal end of said robotic
arm, cutting a wire on said access valve cap, and detaching and
storing said wire cutter tool.
81. The method of claim 69, wherein said robotic arm is controlled
by a teleoperation system configured for remote operation with a
human teleoperator issuing commands via a user interface.
82. The method of claim 69, wherein said robotic arm is controlled
by a mixed autonomous/teleoperation control system including: a
computer controller programmed to operate some or all of the fluid
transfer operations, and a teleoperation system configured to have
a human teleoperator remotely operate some or all of the fluid
transfer operations through a user interface, and wherein said
mixed autonomous/teleoperation control system is configured to work
in any one of three modes, including a first autonomous mode in
which the computer controller controls all fluid transfer
operations, a second teleoperation mode in which said human
teleoperator remotely operates said robotic arm through said user
interface to control all fluid transfer operations, and a third
supervised autonomy mode in which said robotic arm is autonomously
operated but all autonomous operations are monitored, can be halted
and must be approved by a human operator.
Description
CROSS REFERENCE TO RELATED U.S PATENT APPLICATION
[0001] This patent application is a continuation of application
Ser. No. 12/073,795, which claims priority benefit from U.S.
provisional patent application No. 60/905,827 filed on Mar. 9, 2007
entitled ROBOTIC SATELLITE REFUELLING METHOD AND SYSTEM, filed in
English, which is incorporated herein in its entirety by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a satellite refuelling
system and method for refuelling satellites.
BACKGROUND OF THE INVENTION
[0003] Many geosynchronous orbit communication satellites currently
in operation were designed with a finite amount of fuel and were
not designed for the possibility of being refuelled. The design
philosophy relied upon replacement of the satellites after they had
exhausted the on-board fuel supply. In view of the expense of
replacing satellites, it would be very advantageous to be able to
refuel communication satellites which are either near their end of
life, or have suffered an infant propulsion system failure, thereby
extending their operational life by several years.
[0004] In many incidents, at the end of a satellite's 10 to 15 year
life all of its subsystems are still functional and it is only the
depletion of the carefully budgeted fuel load that drives
retirement of the satellite. Using a current economic model, the
ability to refuel 10 to 12 of these end of life satellites in one
mission, would extend their useful life by 3 to 5 years and thereby
delay the need to outlay the $150 -$250 M to launch a replacement.
Some satellites suffer from primary propulsion system failures soon
after they are launched. In these cases the entire book value must
be written off and compensation paid to the operator by the space
insurer. The satellite becomes an asset of the space insurer and
will eventually have to be disposed of in a graveyard orbit. If one
of these assets can be refueled, extending its life by 5 to 10
years, most of the value of the spacecraft can be recovered.
[0005] The key technical difficulty is that these satellites were
not designed for robotic servicing, and it is not generally
accepted that such missions are technically possible. Specifically,
most satellites are designed with fuel fill and drain valves that
were intended to be filled once prior to launch and never opened or
manipulated again. Thus, accessing these fill and drain valves
remotely presents several major challenges and would involve
several operations, each of which is difficult to accomplish
robotically including: cutting and removal of the protective
thermal blankets, removal of several lockwires hand wrapped around
the valves, unthreading and removing outer and inner valve caps,
mating the fuel fill line to the valve nozzle, mechanically
actuating the valve, and when refuelling is complete, replacing the
inner valve cap.
[0006] On-orbit servicing has been the subject of much study over
the past thirty years. The idea of maintaining space assets rather
than disposing of and replacing them has attracted a variety of
ideas and programs. So far the concept has only found a home in the
manned space program where some success can be attributed to the
Hubble Space Telescope repair missions, Palapa-B2 and Westar rescue
missions and the assembly and maintenance of the International
Space Station.
[0007] Robotic capture and servicing of existing geostationary
spacecraft has never been demonstrated. Over the past decade
several of the key technologies required for orbital servicing have
matured. These include autonomous rendezvous (ETS-VII (1998),
XSS-11 (2005), DART (2006), Orbital Express (2007), autonomous
docking (ETS-VII, Soyuz, Orbital Express), ground based robotic
tele-operation (ETS-VII, SSRMS (2005), Orbital Express), and on
orbit fluid transfer (ISS). However a gap exists in the
technologies required to service or re-fuel an un-prepared
satellite in orbit. An unprepared satellite is defined here as a
spacecraft that was not designed to be manipulated or repaired by a
robotic system. Some advances have been made in the technologies
required to dock with an unprepared satellite, and both DLR (German
Aerospace Center)and MDA have demonstrated through various R&D
efforts that docking to a GEO communication satellite via the
spacecraft's apogee kick motor is a viable docking option.
[0008] To date there have been no technologies disclosed that can
solve the problem of accessing the fuel system of an unprepared
satellite for the purpose of replenishing station keeping fuel. The
majority of satellites in orbit today were not designed with
orbital refuelling in mind and access to the fuel system is
designed to be accessed by a human on earth before launch. The
technologies required to access the target spacecraft's fuel system
for the purposes of refuelling still have a very low technology
readiness level, and are generally considered to be the main
obstacle to a successful servicing mission.
[0009] United States Patent Publication No. 2006/0151671 (Kosmos)
discloses an actuator arm mounted on a spacecraft designed as a
servicing manipulator for use within a spacecraft service bay and
includes an actuator arm connected to a base using flexible
connection tapes.
[0010] United States Patent Publication No. 2006/0151671 discloses
a servicing communication architecture in which the communication
between a ground station and the servicing satellite is carried out
via the communication system of the client satellites communication
links. Also disclosed is a general servicing architecture in which
target satellites are captured and returned to a servicing
spacecraft. Within this servicing spacecraft it is proposed that
any required servicing operations could be conducted.
[0011] The publication "On-Orbit Servicing by "HERMES
On-Orbit-Servicing System, Policy Robust Planning", C. Kosmos,
American Institute of Aeronautics and Astronautics, SpaceOps 2006
conference proceedings", pp 1 to 6, Apr. 26, 2006, discloses a
satellite refuelling architecture that requires each satellite to
be serviced to have a custom quick disconnect (QD) coupling
attached to its service valve before launch. A preliminary design
for a valve access tool used to access this valve is also
presented.
[0012] Therefore, it would be very advantageous to provide a
satellite refuelling system for earth-based controlled refuelling
of unprepared satellites.
SUMMARY OF THE INVENTION
[0013] The present invention provides a method, system and
apparatus for robotic refuelling of satellites. The system may
include a dedicated refuelling satellite launched directly from
either earth, or alternatively transiting from another larger
mother spacecraft or space station in which the refuelling
satellite is launched into space for the refuelling mission or it
may be stored on the space station, on-call for the next needed
refuelling operation. The system includes a positioning mechanism
such as a robotic arm, suitable tools which can be affixed to the
end effector of the robotic arm required for accessing, opening and
closing the fuel fill valve(s) on the satellite being serviced,
storage and retrieval stations on a tool caddy on which the tools
and various fuel fill valve caps are stored.
[0014] In one embodiment, the system is tele-operated by a remotely
located operator, for example located on earth, or in a space
station. Cameras in the refuelling system are focussed on the
robotic arm and end effector, with the operator using the
transmitted images to direct and control the refuelling
procedure.
[0015] In another embodiment, the refuelling system may be equipped
with an artificial vision function which is used to register the
worksite in the vicinity of the fill-drain valve, providing
relative positions between the servicing arm/tool combination with
the valves. The refuelling system is then controlled in a
supervised autonomous manner using an updated model of the worksite
derived from the artificial vision function registration
information. The system disclosed herein may also be used for
fuelling for the first time satellites prior to launch, thereby
eliminating or at least reducing the risk of a refuelling
technician being exposed to the toxic fuel in the event of a
mishap.
[0016] An embodiment of the invention provides a method of
transferring fluid from a servicer spacecraft to a client
spacecraft, said client spacecraft including a tank and a fluid
port coupled to said tank, said fluid port including a fluid valve,
said fluid valve including a valve actuation nut for opening and
closing said fluid valve, said fluid being selected from the group
consisting of fuel and oxidizer, the method comprising:
[0017] instructing a robotic arm on said servicer spacecraft to
perform the steps of: [0018] removing an access valve cap on said
fluid valve; [0019] attaching a fluid line to said fluid valve; and
[0020] opening said fluid valve by actuating said valve actuation
nut, thereby transferring fluid into said tank.
[0021] Another embodiment of the present invention provides a
method of transferring fluid from a servicer spacecraft to a client
spacecraft, said client spacecraft including a tank and a fluid
port coupled to said tank, said fluid port including a fluid valve,
said fluid valve including a valve actuation nut for opening and
closing said fluid valve, said fluid being selected from the group
consisting of fuel and oxidizer, the method comprising:
[0022] instructing a robotic arm on said servicer spacecraft to
perform the steps of: [0023] retrieving an access valve cap removal
tool and mounting same to a distal end of said robotic arm;
engaging said access valve cap removal tool to remove an access
valve cap on said fluid valve; detaching and storing said access
valve cap removal tool; [0024] retrieving a fluid line coupling and
mounting said fluid line coupling to said distal end of said
robotic arm; coupling said fluid line coupling to said fluid valve;
and [0025] opening said fluid valve by actuating said valve
actuation nut, thereby transferring fluid into said tank.
[0026] A further understanding of the functional and advantageous
aspects of the invention can be realized by reference to the
following detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The invention will be more fully understood from the
following detailed description thereof taken in connection with the
accompanying drawings, which form part of this application, and in
which:
[0028] FIG. 1 is shows a robotic satellite refuelling apparatus for
refuelling satellites mounted on a servicing spacecraft and
refuelling a satellite;
[0029] FIG. 2 shows a perspective view of the apparatus of FIG. 1
with two cameras mounted on booms focused on the refuelling tool
for visually assisting operators on earth instructing the robot in
the refuelling procedure;
[0030] FIG. 3 shows a perspective view of a partially assembled
valve tool forming part of the refuelling system of the present
invention;
[0031] FIG. 4 shows an exploded disassembled view of the valve
tool;
[0032] FIG. 4b shows a perspective view of a clamping mechanism
forming part of the valve tool;
[0033] FIG. 4c shows an elevational view of a valve actuation
mechanism forming part of the valve tool;
[0034] FIG. 5 shows the fully assembled valve tool holding a socket
module;
[0035] FIG. 6 shows a module caddy on which various refuelling and
draining connectors are mounted;
[0036] FIG. 7a is a an exploded disassembled view of the caddy of
FIG. 6 looking from one direction;
[0037] FIG. 7b is a an exploded disassembled view of the caddy of
FIG. 6 looking from similar to FIG. 7a but looking from another
direction;
[0038] FIG. 8 shows the valve tool forming part of the present
invention holding a fuel line coupling and connecting it to a fuel
valve;
[0039] FIG. 8a shows a portion of a valve tool engaging a valve cap
on a client satellite;
[0040] FIG. 9 shows a cross sectional view of a typical fuel fill
valve mounted on a satellite to be refueled by the system forming
the present invention;
[0041] FIG. 10 shows the clearances and interferences between the
B-nut and the valve actuator nuts and the valve actuator;
[0042] FIG. 11 shows a fuel/oxidizer spillage management system
forming part of the present invention; and
[0043] FIG. 12 is a flow diagram showing the steps involved in
refueling a satellite using the method and system forming part of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0044] Generally speaking, the systems described herein are
directed to a satellite refuelling method and apparatus for
refuelling satellites. As required, embodiments of the present
invention are disclosed herein. However, the disclosed embodiments
are merely exemplary, and it should be understood that the
invention may be embodied in many various and alternative forms.
The Figures are not to scale and some features may be exaggerated
or minimized to show details of particular elements while related
elements may have been eliminated to prevent obscuring novel
aspects. Therefore, specific structural and functional details
disclosed herein are not to be interpreted as limiting but merely
as a basis for the claims and as a representative basis for
teaching one skilled in the art to variously employ the present
invention. For purposes of teaching and not limitation, the
illustrated embodiments are directed to a satellite refuelling
apparatus, system for and method for refuelling satellites.
[0045] Referring to FIGS. 1 and 1a, broadly, the present invention
is directed to refuelling system for refuelling an unprepared or
partially prepared client satellite 14. The system includes a fluid
transfer system 41 for transferring fuel from a fuel storage tank
15 on the servicer spacecraft 12 to a fuel tank 21 on the client
satellite 14 and for transferring oxidizer from an oxidizer storage
tank 13 on a servicing spacecraft 12 to an oxidizer tank 17 on the
client satellite 14. The system includes a tool mechanism 30 for
coupling a fuel fill line 19 to a fuel port 23 on fuel tank 21 and
decoupling the fuel fill line 19 therefrom, and for attaching an
oxidizer fill line 25 to an oxidizer port 27 on the oxidizer tank
17 and decoupling the oxidizer fill line 25 therefrom. It will be
appreciated that while FIGS. 1 and 1a, do not show the details,
fluid transfer system 41 in addition to containing the storage
tanks for oxidizer and fuel, also contain all the other required
equipment for pumping oxidizer and fuel from system 41, such as,
but not limited to liquid pumps, filters, propellant management
devices, valves, valve actuators and various sensors and monitors.
The fluid transfer system described will be used to replenish
either fuel or oxidizer or both to satellites which require these
fluids replenished. This includes both bi-propellant propulsion
system satellites and mono-propellant propulsion system
satellites.
[0046] The refuelling system includes a sensing array 26 for
determining a relative displacement between the tool mechanism and
fuel and oxidizer ports 23 and 27 on the client satellite 14. The
system includes a positioning mechanism 16 connected to the sensing
array 26 for positioning the tool mechanism 30 with respect to the
fuel and oxidizer ports 23 and 27 on the client satellite 14 for
coupling and decoupling the fuel and oxidizer fill lines to the
fuel and oxidizer ports respectively. The system includes a control
system 29 in communication with the sensing mechanism, positioning
means and tool mechanism to control operation of the positioning
mechanism and the tool mechanism based on feedback from the sensing
mechanism.
[0047] In the context of the present patent application, the phrase
"unprepared client satellite" means a satellite that has been
launched into orbit without any design features that would simplify
or facilitate on orbit refuelling or servicing.
[0048] In the context of the present patent application, the phrase
"partially prepared client satellite" means a satellite on which on
orbit servicing or refuelling has been considered in its design.
Standard interfaces are used on these satellites but implemented
with consideration to facilitate on orbit servicing. An example of
this could be a redesign of the thermal system to that would allow
removal of thermal blankets from the region around the fuel or
oxidizer fill ports.
[0049] As shown in FIG. 1 the positioning mechanism 16 includes a
robotic arm (which may be as a simple as a two degree-of-freedom
mechanism) and an end effector 18 which is adapted to receive and
mate with various tools such as valve tool 30, along with the other
tools that are contained in a tool storage container 20. The tools
include the valve tool 30 as mentioned above, as well and cutters
for cutting thermal blankets enveloping the fill valves, tools for
disabling lockwires that may be fixing various moving components on
the fill valves and a tool to unfasten and remove outer caps on the
fill valve.
[0050] Client satellite 14 may be of any kind in any orbit
requiring fuel to increase the lifetime of the satellite. The
servicing spacecraft 12, while shown in the form of the space
shuttle may be any type of spacecraft, manned or unmanned as long
as it is in communication with operators on earth to direct the
robotic arm 16 during the refuelling process. Alternatively, the
robotic arm 16 may be operated autonomously during the refuelling
process as will be discussed hereinafter. In this mode of
operation, the refuelling system is equipped with an artificial
vision function which is used to register the worksite in the
vicinity of the fill-drain valve.
[0051] The refuelling system is then controlled in an autonomous
manner using an updated model of the worksite derived from the
artificial vision function registration information. The sensor
system 26 is shown in the embodiment in FIGS. 1 and 1b as two
cameras included to provide visual images of the tool 30 which are
transmitted to the ground station for providing confirmation to the
operator of the autonomous refuelling operation procedure. While
two cameras are shown, and are considered to be the optimum number
needed, it will be understood more or less cameras 26 may be
included.
[0052] As mentioned above, the control system used for controlling
the refuelling system may be configured in one of several ways. In
one embodiment of the system, the refuelling operation may be
controlled by a teleoperator, namely a person remotely operating
the system through a user interface who may be located on earth or
in another spacecraft or space station. In another embodiment the
system may be configured to be operated in an autonomous mode of
operation, in which the control system includes computers which
control all or some of the servicer refuelling operations. These
computers may be located on the servicer spacecraft or they may be
located on earth, or on another spacecraft. In another embodiment
the refuelling system may be configured to operate in a supervised
autonomy mode such that the control system involves a combination
of teleoperation and autonomous operation. In supervised autonomy a
user monitors the servicing operations, and gives proceed commands
to the autonomous operations which can be elemental operations or
preprogrammed chains of commands. Thus the control system may be
configured to have some tele-operation, and some autonomous or
supervised autonomous operation for this mission. The system may be
configured to be able to use all these modes of operation with a
user able to switch between the different modes.
[0053] The valve tool 30 includes a support frame, a socket module
holder mechanism mounted on the support frame configured to accept
interchangeable socket modules to be described hereinafter, and a
socket drive mechanism mounted on the support frame for actuating
the socket modules when seated in the socket module holder
mechanism. The valve tool 30 includes a clamping mechanism mounted
on the support frame to secure the valve tool 30 to a reaction area
of the fuel fill valve and oxidizer fill valve. The clamping
mechanism is configured to localize torque generated by the valve
tool 30 for ensuring that any reaction torques from the socket
drive mechanism are reacted locally to prevent damage to the valves
on the tanks of the client satellite. The valve tool 30 includes a
valve actuation mechanism mounted on the support frame used to open
and close the fuel and oxidizer fill valves by actuating their
respective valve actuation nuts. These components making up the
valve tool 30 will now be discussed in more detail.
[0054] FIG. 2 shows a close up of an embodiment of valve tool 30
mounted on end effector 18 with cameras 26 mounted on booms 28
which are configured to provide a clear and unobstructed view of
the tool 30 and valve 55 on the satellite 14, FIG. 3 shows a
perspective view of the partially assembled valve tool 30 and FIG.
4 shows the valve tool 30 disassembled. Referring to both FIGS. 3
and 4, the support frame includes a base plate 40 with two long
standoffs 50 secured to base 40. A motor frame plate 56 is bolted
on top of three spacers 58 which in turn are bolted to base plate
40. The socket module holder mechanism includes socket module
holder 60, and a module retaining bar 63.
[0055] The socket drive mechanism includes motor-gearbox units 54b,
one of the couplings 68, bolts 61, an external gear 70, bearings 72
and 73, and a shaft 106 and a pinion 108. The socket drive
mechanism is used to activate the sockets located in a socket
module holder 60 and is driven by motor-gearbox unit 54b, which
along with motor-gear box unit 54c used to drive a clamp mechanism
77 to be discussed below, are mounted on motor frame plate 56 and
the shaft of each motor 54a, 54b and 54c is connected to an
associated coupling 68. Three short standoffs 52 are bolted on top
of motor frame plate 56. A middle base section 62 is mounted on top
of a lower base section 64 and both are bolted together to base
plate 40 by bolts 66. A gear 70 is seated in the circular opening
in middle base section 62 and the socket module holder 60 is seated
in the gear 70 (seen only in FIG. 4). The gear 70 and module holder
60 are supported by an upper ball bearing 72 and a lower ball
bearing 73. The upper bearing 72 is supported by the base plate 40.
The lower bearing 73 is supported by the middle base section
62.
[0056] Referring to FIGS. 4 and 4b, clamping mechanism 77 with two
fingers 48 is bolted to middle base section 62 by a bolt 76 and the
two fingers pivot about an axis defined by bolt 76. A clamp support
80 is mounted on the side of the middle base section 62. Tool 30
includes two clamp links 84 and 86 pinned to the clamp finger 48
and to the clamp shaft 88 perpendicular to the plane of actuation
of the clamp fingers 48 containing axis 51 (FIG. 4b). As motor-gear
box unit 54c rotates the clamp-shaft 88 through a half turn about
shaft axis 49, the clamp links 84 and 86 either push the ends of
the clamp fingers 48 apart, which closes the gripping surfaces on
the clamp onto the reaction area of valve 55, or pulls the ends of
the clamp fingers 48 together, which opens the clamp sufficiently
to allow the valve 55 to pass through. The clamp-shaft 88 is
supported on both ends by bushings 90. The top bushing 90 is
press-fit in the base plate 40 and bottom bushing 90 is press-fit
into the clamp-support 80 which is attached to the middle base
section 62.
[0057] Referring to FIG. 4c, a valve actuation mechanism 87
includes an external gear 96 with an internal wrench profile as
shown in FIG. 10. External gear 96 is supported by a bearing 98 and
is affixed to that bearing with bearing holder 100. The external
gear 96 is driven by a pinion 104 attached to shaft 102. Shaft 102
is coupled to motor gear-box 54a via coupling 68. The ends of shaft
102 are inserted into bushings 103 with the top bushing press-fit
into base plate 40 and the bottom end is press fit into base plate
64.
[0058] The valve actuation mechanism 87 is driven by motor gearbox
54a. As motor-gearbox 54a rotates, shaft 102 rotates and pinion 104
driving gear 96 which has parallel flats, similar to a wrench, that
engage the valve actuation nut of the valve 55. The engagement
allows the gear 96 to open and close the valve 55.
[0059] The front view of the fully assembled tool 30 is shown in
FIG. 5. The support frame includes a top plate 57 is bolted to the
two long standoffs 50 and the three short standoffs 52. A fuel line
socket module 192 is shown gripped by tool 30. A grapple fixture 59
is bolted to the top of top plate 57 and is used by end effector 18
to grasp the tool 30. Mounted adjacent to the grapple 59 is an
n-pin electrical connector half (not shown). Mounted on the
end-effector 18 is a connector mating mechanism (not shown). Once
the end-effector 18 completes grappling of the tool 30, the
connector mating mechanism extends the opposite half of the
electrical connector on to the connector mounted on plate 57,
thereby providing power and control signals to the tool.
[0060] The base plate 40, middle base section 62 and lower base
section 64 form the basic body of the tool 30 supporting all the
internal components. The frame includes motor frame plate 56, the
short standoffs 52 and the long standoffs 50 and top plate 57. This
frame has three functions, i) protect the motors 54a, b and c, ii)
provide structure to attach the base (formed by the base plate 40,
middle base section 62 and lower base section 64) to the top plate
57, and iii) provide lineup guides (the long standoffs 50) for
operations using the caddy shown in FIG. 7 discussed
hereinafter.
[0061] The three motor-gearbox units 54a, 54b and 54c may be
identical, even though they do not need to be. The motors that are
used are DC brush motors however it will be understood that DC
brushless motors, stepper motors, AC motors, servomotors, or other
types of motor could be used. The gearboxes that are used are
planetary gearboxes. Other gearboxes such as spur gearboxes could
be used. Ideally, but not necessarily, the gearboxes would be
backdrivable. If the motors can provide sufficient torque the
gearboxes may not be needed at all.
[0062] The function of the clamping mechanism 77 is to secure the
valve tool 30 to the reaction area of the valve 55, thereby
ensuring that any reaction torques from the socket drive mechanism
or valve actuator are reacted locally to prevent damage to the
valve.
[0063] Referring to FIG. 4b, the clamping mechanism 77 is a double
four-bar linkage and the four main parts of the linkage are the
clamp-shaft 88, the clamp-link 84 or 86, the clamp-fingers 48 and
the base of the valve tool 30 formed by middle base section 62 and
lower base section 64. The clamp is driven by the gear-motor 54 on
the right hand side of the tool shown in FIG. 5. The gear-motor 54c
drives the clamp-shaft 88 through its associated flexible coupling
68. The clamp-shaft 88 is the input, and rotates about 1/2 turn for
the clamp to go from open position to closed position. The clamp
links 84 and 86 push and pull respectively the clamp-fingers 48
closed or open.
[0064] The geometry of the clamp four bar mechanism has been
selected so that in the closed position, the clamp has an
"over-centre" locking characteristics. The motor-gearbox unit 54c
is used to open or close the clamp mechanism, but when the clamp
mechanism is in either position, any forces exerted by the valve 55
on the "reaction area" are transferred directly through clamp-shaft
88 and not through the motor 54c. This allows the motor 54c to be
significantly smaller and lighter than would the case if the design
of the clamp was such that any forces exerted by the valve on the
"reaction area" were instead transferred directly through the motor
54c.
[0065] The socket module holder 60 mechanism has two functions: 1)
to drive the B-nut or fuel-line-nut on or off the valve of the fuel
tank on the satellite being refueled; and 2) accept and retain the
corresponding modules required for coupling the fluid transfer
system to the oxidizer and fuel tanks on the client satellite.
[0066] The socket module holder 60 is driven by gear motor 54b in
the centre of the group of three motors 54a to 54c in FIG. 5. The
centre gear motor 54b drives the shaft 106 through its associated
flexible coupling 68 (FIG. 4). The shaft 106 is supported on both
ends by bushings 109. The top bushing 109 is press-fit in the base
plate 40 and the bottom bushing 109 is press-fit into the middle
base section 62.
[0067] Referring particularly to FIG. 4, the pinion 108 is attached
to the shaft 106 by a radial dowel pin 111. Then pinion 108 drives
the gear 70. The gear 70 is attached to the module holder 60 with
two screws 61.
[0068] The socket module holder 60 is designed to accept and drive
the hexagonal B-nut of the valves located on the fuel tank and the
oxidizer tank of the satellite being serviced, and to accept and
retain the various socket modules. The fuel line and oxidizer line
socket 192/194 and socket modules 196/198 (FIG. 3) are contained or
held in place with the module retaining bar 63. The module
retaining bar 63 rotates about a set-screw 65. The module retaining
bar 63 features a detent system that holds the retaining bar 63 in
either the "open" or "closed" position. This detent system
comprises a ball-detent-spring 67 situated in the module holder 60
that engages two holes in the module retaining bar 63,
corresponding to the "open" and "closed" positions, on the B module
retaining bar 63. The various sockets are all designed to include a
V-groove 79 situated on the circumference of the socket so that
when the socket is inserted into the socket module holder 60,
retaining bar 63 can be toggled into groove 79, capturing the
socket, preventing it from being forced out of the socket module
holder 60 during operation.
[0069] FIG. 6 shows a perspective view of the assembled module
caddy 190 for holding the different socket modules, one fuel line
socket module 192 being for engaging the fuel fill valve 55,
thereby coupling the fuel tank on the client satellite to the fuel
transfer system on the servicer spacecraft through the tube forming
part of the fuel line socket module 192, another oxidizer line
socket module 194 being for engaging the oxidizer fill valve
thereby coupling the oxidizer tank on the client satellite to the
fuel transfer system on the servicer spacecraft through the tube
forming part of the oxidizer line socket module 192, and a third
socket module 196 being for engaging the valve access cap (B-nut)
on the fuel fill valve, and a fourth socket module 198 being for
engaging the valve access cap (B-nut) on the oxidizer fill valve.
There is also a storage place 208 on rail 200 for the B-nut.
[0070] While not shown in FIG. 6, tool caddy 190 includes a holder
for valve tool 30, and other tools such as the blanket cutter,
outer cap removal and replacement tool and the blanket spreader
tool. Thus, initially when the refueling system is deployed, any of
the required tools can be attached to the end effector of the
positioning mechanism 16, used and then stowed into the storage
holder.
[0071] FIGS. 7a and 7b shows the module caddy 190 disassembled.
Referring to FIGS. 6, 7a and 7b, caddy 190 includes a tubular rail
200 on which four module caddies 202 are mounted. FIG. 7 shows in
more detail the components of the caddies 202. Each caddy 202
includes a base plate 206, a socket module retaining plate 210 and
a top plate 214. Socket module retaining plate 210 is bolted
directly to the base plate 206 by bolts 216 and top plate 214 is
spaced above base plate 206 by spacers 218 and bolted to the
spacers 218 by bolts 220 while the spacers are bolted to the base
plate 206 by bolts 222. The `V` groove 79 located at the top of
socket modules 192, 194, 196 and 198 are configured to mate with a
spring ball detent 232 to hold the modules 192, 194, 196 and 198 in
place in each of the four socket module holders 202.
[0072] The module retaining bar 63 is activated by a tab 234 (shown
in FIG. 7b) on the socket module retaining plate 210. When the tool
30 is fully engaged to the module caddy 190, the tab 234 on socket
module retaining plate 210 is close to the outer diameter of the
module holder 60. The module retaining bar 63 protrudes outside of
this diameter. When the motor 54b of the socket drive mechanism is
activated the module retaining bar 63 will eventually come in
contact with the tab 234 on the socket module retaining plate 210
and be toggled to the opposite position. Driving the socket
clockwise will lock the module in the module holder 60, and
conversely, driving the socket counter-clockwise will unlock the
module.
[0073] A second ball-detent-spring in the hex-socket portion of the
module holder 60 is used to engage the B-Nut of the valve and hold
it in place when it is being transferred from the valve to its
storage location 208.
[0074] FIG. 8 shows the refuelling system coupled with the fuel
valve 55 of the client satellite with valve tool 30 holding a fuel
line socket module 192 engaged with valve 55 thereby coupling the
fuel line of socket module 192 to the fuel valve 55. This
configuration is achieved after the servicer satellite has captured
and docked with the client satellite, and the fuelling system on
the servicer satellite has been deployed and the access valve caps
(B-nuts) on the fuel/oxidizer tanks have been removed using the
socket modules 196 and 198, which processes are laid out below in
more detail. As can be seen from FIG. 8, the lower base section 64
of the support frame includes a passageway which has dimensions and
associated lead-ins 410 to receive therein a portion of the fuel
fill valve 55 (and the comparable valve located on the fill port of
the oxidizer tank of the client satellite). As mentioned above,
several sections of valve tool 30 are designed specifically for
robotic teleoperation by providing lead-in features such as the
base bottom section 64 which include lead-ins (chamfer) 410. These
lead-ins along with the cut-outs 46 enable the bottom section of
base bottom section 64 to be mated to the fuel valve 55 thereby
coupling the fuel line socket module 192 to the valve 55. The
socket module holder 60 is mounted in the mid base section 62 such
that when a socket module is located in the module holder 60 a
portion of the socket module projects into the passageway to engage
the fuel fill valve and said oxidizer fill valve.
[0075] FIG. 9 shows a cross sectional view of a typical fuel fill
valve 55 mounted on the client satellite to be refueled by valve
tool 30. Valve 55 includes an outer cap 362 and an outer cap
lockwire 370 secured to base 380. A B-nut cap 364 is threaded onto
the valve stem 368 and a lockwire 366 secures the B-nut cap 364 to
the valve stem. An actuation nut 374 is rotated to open or close
the valve. The lockwire 372 secures the actuation nut 374 to the
valve stem 368.
[0076] Referring to FIG. 10, the valve actuator gear 96 is designed
to accept and drive the square of the valve actuator of the valve.
The "wrench" portion of the valve actuator is configured so that it
allows maximum clearance, when passing over the B-nut of the valve,
and sufficient contact area to drive the valve actuator of the
valve.
[0077] Tool 30 is configured with to be able to be used in
conjunction with camera views from cameras 26. The openness of the
frame and the cutouts in the base allow cameras to see all of the
critical phases of the tool operation. There are cutouts 69 in the
base middle section 62 and cutouts 46 in the base bottom section 64
(see FIGS. 3 and 5). There are features machined into the following
pieces and in the frame design to allow easy interpretation of
position with cameras 26: module holder 60, gear 96, module
retaining bar 63 and clamp 77.
[0078] Several pieces of valve tool 30 and the tool caddy 190 are
designed specifically for robotic teleoperation by providing
lead-in features. They include the base bottom section 64 which
include lead-ins (chamfer) 410 (FIG. 8), gear 96 which include
lead-ins (chamfer) 412, module holder 60 which includes lead-ins
(chamfer) 414 (FIG. 8a) and (chamfer) 416 (top for modules and
bottom for B-Nuts), the tool frame design, the module caddy top
plate 214 which includes lead-ins 420, and the module caddy base
plate 206 which includes lead-ins 418 (FIGS. 6 and 7).
[0079] An embodiment of the system may include a fuel spillage
management system. During each connection-disconnection cycle there
is a minimal leakage of propellant in the range of 2 cm.sup.2. In
many cases this spillage will not cause any harm to either the
client satellite or the servicing spacecraft, and can be slowly
evacuated to space. In other cases, client spacecraft with
sensitive elements, such as optics or exposed gears, may
necessitate the management of the spilled fuel. Quick disconnect
couplings offer a means to minimize the spillage to an acceptable
level, but these couplings would have to be installed onto client
satellites pre-launch.
[0080] The spillage management system illustrated generally at 600
in FIG. 11, evacuates the spillage volume into a vacuum plenum 602
located onboard the servicer spacecraft, diluting the spillage,
before it is eventually evacuated to space in a controlled manner.
Thus, before the servicing tool is separated from the client
service valve, the spillage is routed to the vacuum plenum 602
diluting the spilled liquid. More particularly, once the servicing
spacecraft has coupled with the client satellite, and the fluid
transfer system has been coupled to the fuel tank of the client
satellite, in the initial state the valves A, B, C, and D are
closed. Valve D is then opened to vent the plenum 602 to vacuum,
and once that is complete valve D is closed. Upon completion of the
transfer of fuel from the holding tank on the servicer craft to the
client satellite fuel tank, any excess fuel in the lines need to be
removed. To dilute excess fuel valve B is then opened and fuel
remaining in the fuel transfer lines are drawn into plenum 60. The
plenum 602 is then pressurized with helium and valve D is then
opened to vent the dilute fuel vapor to the zenith side of the
servicer craft through vent 604. The vented plume of fuel or
oxidizer are directed away from the servicer-client spacecraft
stack minimizing the potential for corrosion of sensitive
spacecraft components.
[0081] FIG. 12 shows a flow diagram of all the steps in refuelling
the spacecraft. After removal of the thermal blanket, fill valve
outer cap and the lockwires have been cut, the valve tool is
affixed to the end effector. When the tool is in operation, the
operational sequences to "refuel" one of the fuel lines is as
follows:
[0082] 1. Mount B-Nut Module
[0083] 2. Remove B-Nut
[0084] 3. Store B-Nut
[0085] 4. Store B-Nut Module
[0086] 5. Mount Fuel-line Module
[0087] 6. Attach Fuel-line
[0088] 7. Open Valve
[0089] 8. Refuel . . .
[0090] 9. Close Valve
[0091] 10. Detach Fuel-line
[0092] 11. Store Fuel-line Module
[0093] 12. Mount B-Nut Module
[0094] 13. Retrieve B-Nut
[0095] 14. Replace B-Nut
[0096] 15. Store B-Nut Module
[0097] Operations concluded
[0098] These tasks are broken down in to detailed steps below.
[0099] Note: [Tool] refers to actions that the tool will do.
[0100] [Robot] refers to action the robot will do.
[0101] Mount B-Nut Module
[0102] 1. [Robot] Move valve tool 30 close to tool caddy 190 with
B-nut module 198
[0103] 2. [Robot] Set height of valve tool 30 so that tool top
plate 57 is above the top of B-nut module 198 and so that the valve
tool middle plate 40 is below the bottom of B-nut module 198. A
camera view will be used to position the tool 30 relative to the
tool caddy 190. (tool change camera)
[0104] 3. [Robot] Move valve tool 30 towards tool caddy 190
lining-up valve tool posts 50 onto tool caddy guides 214. Ensure
posts 50 are touching guides 214 lightly.
[0105] 4. [Tool] Activate valve tool B-nut actuator 54b to set
module retaining bar 63 away from tool caddy 190.
[0106] 5. [Robot] Move valve tool 30 up until valve tool middle
plate 40 touches tool caddy bottom tab 234 socket module retaining
plate 210.
[0107] 6. [Tool] Activate valve tool B-Nut Actuator 54b in "Lock"
direction until Locking Mechanism is engaged (approximately 1/2
turn)
[0108] 7. [Robot] Move valve tool 30 down until B-Nut Module 198
(now attached to valve tool 30) is below the bottom of the tool
caddy 190
[0109] 8. [Robot] Move valve tool 30 directly away from tool caddy
190
[0110] 9. With the B-nut module 190 now mounted, proceed with next
task.
[0111] Remove B-Nut
[0112] Assume B-Nut Module is mounted
[0113] 1. [Robot] Move Tool 30 close above Valve 360. This can be
accomplished by moving the robot to a pre-programmed position.
[0114] 2. [Robot] Align centre of Tool 30 with Valve. The alignment
can be achieved using two orthogonal camera views. (alignments
cameras)
[0115] 3. [Robot] Align Tool with reaction area 376 flats on Valve.
This alignment is achieved by rotating the tool 30 about its long
axis until the rectangular plate 372 to which the valve is mounted,
appears square in both alignment camera views.
[0116] 4. [Tool] Ensure Clamp 77 is Open
[0117] 5. [Robot] Seat the tool 30 down onto the valve 360. Two
approaches will work to accomplish this:
[0118] 6. Approach 1: Pre-align the contact surfaces of the tool to
match the corresponding surfaces of the valve using camera views
that have a clear view of the tool contact surfaces, as follows:
[0119] a. [Robot] Align Tool 30 with reaction area 376 flats on
Valve 360 [0120] b. [Tool] Align hex on B-Nut Actuator 60 with
B-Nut 364 on Valve 360 [0121] c. [Tool] Align Valve-Actuator 96
flats on Tool 30 with flats for valve-actuator 374 on Valve [0122]
d. [Robot] Move Tool 30 down until Tool is seated completely.
[0123] 7. Approach 2: Slide the tool 30 down over the valve 360
until it gets stuck on a valve feature. The tool will get stuck if
the B-nut socket is not aligned with the B-nut 364 or the
Valve-Actuator 96 flats on the tool is not aligned with the valve
actuator 374 on the valve. Fiducial marks on the alignment camera
view will indicate which feature is not aligned. The tool may get
stuck on both, none, or one of the features. [0124] a. Slide the
tool 30 down over the valve until the B-nut actuator 60 on the tool
gets stuck on the B-Nut 364. [0125] b. Slowly tighten the B-nut
actuator 60 until the tool becomes unstuck. [0126] c. If the tool
now gets stuck on the valve actuator 374, slowly tighten the valve
actuation wrench 96 on the tool 30 until it becomes unstuck.
[0127] 8. [Tool] Close Clamp 77
[0128] 9. [Tool] Activate Valve-Actuator 96 in "Tightening"
direction
[0129] 10. [Tool] Activate B-Nut Actuator 60 in "Loosening"
direction until B-Nut is fully un-threaded. (approx 5
revolutions)
[0130] 11. [Robot] Exert downward force.
[0131] 12. [Tool] Open Clamp 77
[0132] 13. [Robot] Move Tool 30 up until clear of Valve 360
[0133] 14. [Robot] Move Tool 30 away from Valve 360
[0134] 15. Ready to proceed with next task
[0135] Store B-Nut
[0136] Assume B-Nut Module 90 is mounted and B-Nut 364 is in
Tool
[0137] 1. [Robot] Move Tool 30 close above B-Nut Storage Post 208.
This can be accomplished commanding the robot to move to a
pre-programmed position.
[0138] 2. [Robot] Align centre of Tool 30 with B-Nut Storage Post
208 using the tool change camera.
[0139] 3. [Robot] Align Tool 30 with reaction area flats on 208
B-Nut Storage Post
[0140] 4. [Tool] Ensure Clamp 77 is Open
[0141] 5. [Robot] Move Tool down until Tool is seated
completely
[0142] 6. [Tool] Close Clamp 77
[0143] 7. [Tool] Activate B-Nut Actuator 66 in "Tightening"
direction until B-Nut 364 is fully threaded. (approx 5
revolutions).
[0144] 8. [Tool] Align Valve-Actuator flats 96 with flats on B-Nut
364
[0145] 9. [Tool] Open Clamp 77
[0146] 10. [Robot] Move Tool 30 up until clear of B-Nut Storage
Post 208.
[0147] 11. [Robot] Move Tool 30 away from B-Nut Storage Post
208
[0148] 12. Ready to proceed with next task
[0149] Store B-Nut Module
[0150] Assume B-Nut 364 is not in Tool 30
[0151] 1. [Robot] Move Tool 30 close to Caddy 202
[0152] 2. [Robot] Set Tool 30 height so that Tool top plate 57 is
above Caddy top and so that the B-Nut Module top 198 is below Caddy
bottom 206
[0153] 3. [Robot] Move Tool 30 towards Caddy 202 lining-up Tool
posts 50 onto Caddy guides #7 and #8. Ensure posts are touching
guides lightly
[0154] 4. [Tool] Activate Tool B-Nut Actuator 54b to set Locking
Mechanism away from Caddy 202.
[0155] 5. [Robot] Move Tool up 30 until Tool middle plate 40
touches Caddy bottom tab 234
[0156] 6. [Tool] Activate Tool B-Nut Actuator 54b in "Unlock"
direction until Locking Mechanism is disengaged (1 turn)
[0157] 7. [Robot] Move Tool down until Tool middle plate 40 is
below bottom of B-Nut Module 198
[0158] 8. [Robot] Move Tool 30 directly away from Caddy 202
[0159] 9. Ready to proceed with next task
[0160] Mount Fuel-line Module
[0161] Assume there are no modules in Tool
[0162] 1. [Robot] Move Tool 30 close to Caddy with Fuel-line
Module
[0163] 2. [Robot] Set Tool height so that Tool top plate 57 is
above the top of Fuel-line Socket Module 192 and so that Tool
middle plate 40 is below the bottom of Fuel-line Socket Module
192
[0164] 3. [Robot] Move Tool 30 towards Caddy 202 lining-up Tool
posts 50 onto Caddy guides #7, #8. Ensure posts are touching guides
#7,#8 lightly
[0165] 4. [Tool] Activate Tool B-Nut Actuator 54b to set Locking
Mechanism 63 away from Caddy 202.
[0166] 5. [Tool] Align hex of B-Nut Actuator 54b with hex of
Fuel-line Socket Module fitting 192
[0167] 6. [Robot] Move Tool 30 up until Tool Middle plate 40
touches Caddy bottom tab 234.
[0168] 7. [Tool] Activate Tool B-Nut Actuator 54b in "Lock"
direction until Locking Mechanism is engaged (approximately 1
turn)
[0169] 8. [Robot] Move Tool 30 down until Fuel-line Socket Module
192 (now attached to Tool) is below Caddy bottom 206.
[0170] 9. [Robot] Move Tool 30 directly away from Caddy 202
[0171] 10. Ready to proceed with next task
[0172] Attach Fuel-line
[0173] Assume Fuel-line Module 192 is mounted. The use of the
camera 26 views described for the removal of the B-Nut operation,
will be used for this operation, but is not described here.
[0174] 1. [Robot] Move Tool 30 close above Valve 360
[0175] 2. [Robot] Align centre of Tool 30 with Valve 360
[0176] 3. [Robot] Align Tool 30 with reaction area flats 376 on
Valve
[0177] 4. [Tool] Ensure Clamp 77 is Open
[0178] 5. [Tool] Align Valve-Actuator 96 flats on Tool with flats
for valve-actuator 374 on Valve 360
[0179] 6. [Robot] Move Tool 30 down until Tool 30 is seated
completely.
[0180] 7. [Tool] Close Clamp 77
[0181] 8. Ready to proceed with opening valve
[0182] Open Valve
[0183] Assume Fuel-line 192 has been attached to Valve 360 (and
therefore Tool 30 is still on Valve 360)
[0184] 1. [Tool] Ensure Clamp 77 is closed
[0185] 2. [Tool] Activate Valve Actuator 54a in "Loosening"
direction until valve-actuator 96 has opened 1 revolution (=approx
5 revolution of coupling 68).
[0186] 3. Ready to proceed with refuelling
[0187] Refuel
[0188] Activate Refuelling system.
[0189] Close Valve
[0190] Assume refuelling has been completed
[0191] 1. [Tool] Ensure Clamp 77 is closed
[0192] 2. [Tool] Activate Valve Actuator 54a in "Tightening"
direction until valve actuator 96 is fully closed. (approx 1
revolution of valve actuator or 5 revolutions of coupling 68).
[0193] 3. [Tool] Activate Valve Actuator 54a in "Loosening"
direction a small step to relieve the force on the valve actuator
96.
[0194] 4. Ready to proceed with detaching fuel-line
[0195] Detach Fuel-line
[0196] Assume Valve 360 has been closed
[0197] 1. [Tool] Activate B-Nut Actuator 54b in "Loosening"
direction until B-Nut 364 of Fuel-line is fully un-threaded.
(approx 5 revolutions)
[0198] 2. [Robot] Exert downward force.
[0199] 3. [Tool] Open Clamp 77
[0200] 4. [Robot] Move Tool 30 up until clear of Valve 360
[0201] 5. [Robot] Move Tool 30 away from Valve 360
[0202] 6. Ready to proceed to next task
[0203] Store Fuel-line Module
[0204] 1. [Robot] Move Tool 30 close to Caddy 202
[0205] 2. [Robot] Set Tool height so that Tool top plate 57 is
above Caddy top 214 and so that the Fuel-line Module 192 top is
below Caddy bottom 206.
[0206] 3. [Robot] Move Tool 30 towards Caddy 202 lining-up Tool
posts 50 onto Caddy guides #7 and #8. Ensure posts are touching
guides lightly
[0207] 4. [Tool] Activate Tool B-Nut Actuator 54b to set Locking
Mechanism 63 away from Caddy.
[0208] 5. [Robot] Move Tool 30 up until Tool middle plate 40
touches Caddy bottom tab 234
[0209] 6. [Tool] Activate Tool B-Nut Actuator 54b in "Unlock"
direction until Locking Mechanism 63 is disengaged (1 turn)
[0210] 7. [Robot] Move Tool 30 down until Tool middle plate 40 is
below bottom of Fuel-line Module 192
[0211] 8. [Robot] Move Tool 30 directly away from Caddy 202
[0212] 9. Ready to proceed to next task
[0213] Mount B-Nut Module
[0214] (as described above)
[0215] Retreive B-Nut
[0216] 1. [Robot] Move Tool 30 close above B-Nut Storage Post
208
[0217] 2. [Robot] Align centre of Tool 30 with Storage Post 208
[0218] 3. [Robot] Align Tool 30 with reaction area flats on B-Nut
Storage Post 208
[0219] 4. [Tool] Ensure Clamp 77 is Open
[0220] 5. [Tool] Align hex on B-Nut Actuator 60 with B-Nut 364 on
Storage Post 208
[0221] 6. [Robot] Move Tool 30 down until Tool 30 is seated
properly.
[0222] 7. [Tool] Close Clamp 77
[0223] 8. [Tool] Activate B-Nut Actuator 60 in "Loosening"
direction until B-Nut is fully un-threaded. (approx 5
revolutions)
[0224] 9. [Tool] Open Clamp 77
[0225] 10. [Robot] Move Tool 30 up until clear of B-Nut Storage
Post 208
[0226] 11. [Robot] Move Tool 30 away from B-Nut Storage Post
208
[0227] 12. Ready to proceed with next task
[0228] Replace B-Nut
[0229] Assume B-Nut Module 198 is mounted and B-Nut 364 has been
retrieved.
[0230] 1. [Robot] Move Tool 30 close above Valve 360
[0231] 2. [Robot] Align centre of Tool 30 with Valve 360
[0232] 3. [Robot] Align Tool 30 with reaction area flats on Valve
376
[0233] 4. [Tool] Ensure Clamp 77 is Open
[0234] 7. [Tool] Align hex on Valve Actuator 96 flats on Tool with
flats for Valve Actuator 374 on valve.
[0235] 8. [Robot] Move Tool 30 down until Tool is seated
completely
[0236] 5. [Tool] Close Clamp 77
[0237] 6. [Tool] Activate B-Nut Actuator 54b in "Tightening"
direction until B-Nut 364 is fully threaded. (approx 5
revolutions).
[0238] 7. [Tool] Align Valve-Actuator 96 flats with flats on B-Nut
364
[0239] 8. [Tool] Open Clamp 77
[0240] 9. [Robot] Move Tool 30 up until clear of Valve 360.
[0241] 10. [Robot] Move Tool 30 away from Valve 360
[0242] 11. Ready to proceed with next task
[0243] Store B-Nut Module
[0244] (as described above)
[0245] The system for refuelling satellites disclosed herein may
include a dedicated refuelling satellite launched directly from
earth on which the refuelling apparatus including the tool caddy,
robotic arm and various tools are mounted. Such a dedicated
satellite may include a spacecraft docking mechanism such as that
disclosed in U.S. Pat. No. 6,969,030 issued Nov. 29 2005, which
patent is incorporated herein in its entirety by reference. The
apparatus may be retrofitted onto any suitable satellite. The
refuelling satellite with the refuelling apparatus mounted thereon
could be carried on a larger "mother ship" and launched from there
or stored on an orbiting space station and launched from there when
needed. The system is under teleoperation by a remotely located
operator, for example located on earth, in the "mother ship" or in
an orbiting space station.
[0246] While the system disclosed herein has been described as a
remote fuelling system for refuelling satellites in orbit once the
fuel has been depleted, it will be understood the present system
may also be used for safely fuelling satellites prior to being
launched into space. In this context, no direct human contact is
needed during the fuelling procedure since the whole process can be
remotely controlled from a safe distance. In this situation the
fuelling is done prior to sealing the thermal blankets and wiring
the valves with the various lockwires so these would not have to be
cut off.
[0247] As used herein, the terms "comprises", "comprising",
"including" and "includes" are to be construed as being inclusive
and open-ended. Specifically, when used in this document, the terms
"comprises", "comprising", "including", "includes" and variations
thereof, mean the specified features, steps or components are
included in the described invention. These terms are not to be
interpreted to exclude the presence of other features, steps or
components.
[0248] The foregoing description of the preferred embodiments of
the invention has been presented to illustrate the principles of
the invention and not to limit the invention to the particular
embodiment illustrated. It is intended that the scope of the
invention be defined by all of the embodiments encompassed within
the following claims and their equivalents.
* * * * *