The Manned Maneuvering Unit (MMU) is a proven free flying platform that can operate in a piloted or unpiloted mode. The MMU is a possible candidate for an on orbit AR&C demonstration. A pilot can transition the system between manual and automated modes, then monitor the automated system for safety

Whitsett, Edward

English

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CATEGORY 4 - OPERATIONS
N93
Operator-Assisted Planning and Execution of Proximity Operations Subject to
Operational Constraints I-O [by Arthur J. Grunwald and Stephen R. Ellis, Ames
Future multi-vehicle operations will involve multiple scenarios that will require a planning tool for
the rapid, interactive creation of fuel-efficient trajectories. The planning process must deal with
higher*order, non-linear processes involving dynamics that axe often counter-intuitive. The
optimization of resulting trajectories can be difficult to envision. An interactive proximity
operations planning system is being .developed to provide the operator with easily interpreted visual
feedback of trajectories and constraints. This system is hosted on an IRIS 4D graphics platform
and utilizes the Clohessy-Wiltshire equations. An inverse dynamics algorithm is used to remove
non-linearities while the trajectory maneuvers are decoupled and separated in a geometric
spreadsheet. The operator has direct control of the position and time of trajectory waypoints to
achieve the desired end conditions. Graphics provide the operator with visualization of satistying
operational constraints such as structural clearance, plume impingement, approach velocity limits,
and arrival or departure corridors. Primer vector theory is combined with graphical presentation to
improve operator understanding of suggested automated system solutions and to allow the operator
to review, edit, or provide corrective action to the trajectory plan.
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Collision Avoidance for CTV: Requirements and Capabilities /_ _z.J_,_
by Thomas Nosek,TRW - ._,/_9
Collision avoidance must be ensured during CTV operations near the space station. The design of
the Collision Avoidance Maneuver (CAM) will involve analysis of CTV failure modes during
rendezvous and proximity operations as well as analysis of possible problems external to the CTV,
but that would require CTV to execute a CAM. In considering the requirements and design of the
CAM for the CTV, the CAM design for the Orbital Maneuvering Vehicle (OMV) is a useful
reference point from which some lessons can be learned and many CTV design options can be set
forth
One design choice, the degree of integration of the CAM with the CTV's prim.ary avionics, will
greatly impact the CTV's CAM options. Also, staged CAM options at successive hold distances
and times provide options for fault recovery without prematurely terminating the mission.
Questions and issues: Is a dissimilar backup computer required (in spacecraft)? Some people
would like to remove the fifth "watchdog" computer unless or until it is shown to be necessary by
some requirement or calculation.
MMU Applications for Automated Rendezvous and Capture /z-/'_ _,--"=',O'_1by Ed Whitsett, NASA, JSC
The Manned Maneuvering Unit (MMU) is a proven free flying platform that can operate in a "_)/:
piloted or unpiloted mode. The MMU is a possible candidate for an on orbit AR&C
demonstration. A pilot can transition the system between manual and automated modes, then
monitor the automated system for safety.
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https://ntrs.nasa.gov/search.jsp?R=19930012249 2020-03-17T06:30:29+00:00Z
There is considerable flight experience with the MMUs. In February 1984, two MMUs were used
on Challenger (STS 41-B). Astronauts performed translations of 150 and 300 feet to and from the
orbiter. With a Trunnion Pin Attachment Device (TPAD) connected to the MMU control arms,
docking exercises were performed on the SESA and SPAS pallets.
Another Challenger mission (STS 41-C) carded two MMUs in April 1984. During EVA, an
astronaut attempted to capture a Solar MAX Satellite that was rotating and out of control.
Unfortunately, the TPAD could not achieve a hard dock with the trunnion pin.
Discovery (STS 51-A) carded the MMUs up to space again in November 1984. Using the MMU,
an astronaut rendezvoused with PALAPA B-2. This time, the TPAD affected a hard dock. The
astronaut stabilized the satellite using the MMU's Automatic Attitude Hold (AAH). A WESTAR
VI was captured two days later, using the same procedure.
Safe, noncontaminating gaseous nitrogen is the MMU propellant. Recharging can occur on-orbit
using the Shuttle's large nitrogen tanks. The MMU can achieve 66 feet per second total change in
velocity with a full charge and average sized astronaut. Other system characteristics are:
MMU weight with full charge:
Operation time on one (1) battery:
Distance in daylight:
Distance at night with running lights:
Translation velocity:
Rotation acceleration:
Height:
Width:
Length:
339 pounds
6 hours
450 feet
150 feet
0.3 ft/sec
10 deg/sec/sec
50 inches
33 inches
27 inches (arms folded)
The MMU can fly in either a pilot monitored or unmanned configuration. EVA Retriever programs
demonstrated automated systems interfaces using MMU flight hardware.
Primary elements of an MMU based on-orbit AR&C demonstration are the MMU, an avionics
package, and the Orbiter Remote Manipulator System (RMS) or Multiple Payload Experiment
Structural System (MPESS), for use as a target. An AR&C avionics package can attach to the
MMU between the control arms. The avionics container could be based on the IMAX camera
design and could be mounted in front of the pilot. The avionics include the docking/capture
sensor, GN&C processors, transmitter, additional power, and an optional pilot supervisory
display. A docking or berthing mechanism can fit on the exterior of the package. An interface
between the avionics package and the MMU would enable the AR&C system to access MMU gyro
data and allow control of the MMU propulsion subsystem.
Propulsion system commands can be issued through the handcontroller interface, based on
automated control algorithms. Control authority of the CTV can be emulated in a pulsed thruster
mode.
Options for the AR&C target are: (1) docking/capture target only; (2) target and docking
mechanism; or (3) spacecraft mockup with target and docking mechanism. Either the Orbiter RMS
or the MPESS can have a mounted target. The MPESS would be in the orbiter cargo bay.
A low cost on-orbit demonstration can start in the near term (~1.5 years). Facilities already exist
for the design, development, simulation, integration, ground test, and training. The Space
Operations Simulation (SOS) Laboratory provides a real-time simulation capability for rapid
development, simulation, and system performance evaluation. The JSC Precision Air Bearing
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Facility (PABF), using a MMU qualification-unit and EVA Retriever, can support physical
integration of the MMU and AR&C systems.
Questions were addressed at the end of the presentation: Can the range of the MMU extend beyond
300 feet? Yes, but at this time a mission rule limits the range to 450 feet. Can an unmanned MMU
be considered for an AR&D demonstration flight? Yes, but we want to make sure to provide
safety/override capability in the event of an anomaly. What is the astronauts' reaction to the Auto
R&D scenario? They do support the effort, but when safety reviews come up, the job of selling
the idea gets harder. _'3,.2 -_/_' .
The Realtime Operations of the Space Shuttle Orbiter _r
during Rendezvous and Proximity Operations //--/_ _ O_ ,).i,
by Andrew Dougherty, Goddard Space Flight Center (9 +
The Shuttle first demonstrated the capability to perform precision proximity flying in 1983 when
the SPAS-01 satellite was deployed and subsequently retrieved. This flight was intended to
validate the capability of the Shuttle to perform proximity operations with a co-orbiting vehicle in
preparation for the Solar Maximum Repair mission of the next year.
STS-39 was flown in April 1991 and contained the most complex relative trajectory flown by the
Shuttle yet. Existing onboard targeting algorithms were used to plan and execute the complex
flight profile. New techniques for using the software had to be developed to support the trajectory
and they proved to be more accurate than the ground software in executing maneuvers.
Shuttle rendezvous operations have two segments: phasing and "the day of rendezvous." Phasing
begins at lift-off and ends when the range to the target is approximately 40 nmi. The "day of
rendezvous" phase of operations covers the last 40 nmi to the target. The name comes from the
fact that most of the maneuvers executed during that last day are computed onboard, providing a
functional difference.
Shuttle proximity operations cover the f'mal phase of the rendezvous. The phase is characterized
by crew control of the trajectory based on radar data and out-the-window viewing of the target. It
begins immediately after the last rendezvous burn and ends with the successful grapple of the
target. A subsection of proximity operations involves the deployment and separations. There are
two phases of proximity operations, the standardized transition trajectory and the final approach.
As the name implies, transition trajectory is a well known and standard trajectory flown by the
crew to transition the Shuttle from an interception trajectory to formation flying with the target
some 130 meters in front of it on the velocity vector. The approach, however, is not as standard
because it depends on the characteristics of the target. Some targets are Local Vertical/Local
Horizontal (LVLH) stabilized and some axe inertially stabilized. The Shuttle program prefers the
target to be in a LVLH stabilized configuration for grapple and places tight restrictions on the
attitude and attitude rates of the target for nominal operations via the PIP.
Many significant lessons can be learned from the Shuttle program that can reduce mission planning
costs for future vehicles; for examples: unify flight design and real-time operations software,
integrate the flight design and real-time operations personnel, provide a control center and flight
vehicle that allows for quick software upgrades, and use new state-of-the-art software development
tools to reduce configuration control.
Significant benefits to both the Shuttle and Cargo Transfer Vehicle programs could be realized by
co-developing rendezvous and proximity operations software because of the commonality of the
algorithms.
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MMU applications for automated rendezvous and capture

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