spheres 0-g autonomous rendezvous and docking testbed presented to darpa orbital express december...
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SPHERES 0-G Autonomous SPHERES 0-G Autonomous Rendezvous and Docking TestbedRendezvous and Docking Testbed
Presented To
DARPAOrbital ExpressDecember 2000
MIT Space Systems Laboratory
David W. Miller
(617) 253-3288
MIT, Cambridge MA
SPHERES (AFRL-0012) SPHERES (AFRL-0012) CONCEPTCONCEPT
OBJECTIVE
— Provide a testbed for long duration, micro-gravity, low risk development of metrology, autonomy and control technologies in support of autonomous rendezvous and docking for DoD and NASA missions.
DESCRIPTION
— Three 0.25 meter diameter, 3.0 kilogram, self-contained satellites with on-board propulsion, processing, RF communication and metrology.
— Communicates with Shuttle/ISS ThinkPads (laptops) for Ku-band (up)downlink access.
— Patterned after MIT MODE (STS-40, 48, 62) and MACE (STS-67, ISS) controls laboratories.
— Successfully completed prototype testing on Air Force, NASA, and MIT funded KC-135 flights in Feb and Mar 2000.
— Manifested on ISS-9a in May 2002
Using ISS to Mature Mission TechnologiesUsing ISS to Mature Mission Technologies
SPHERES on ISS is designed to mature algorithmic technologies (metrology, autonomy and control) for multi-vehicle autonomous rendezvous & docking.
SPHERES has access to long duration -G that allows 6 DOF per vehicle testing under large relative motions between vehicles in close proximity.
SPHERES is a unique facility that allows algorithms at low TRL to be matured in a representative space environment
— Tolerant to risk associated with low TRL since crew can replenish consumables, terminate tests exhibiting anomalous behavior, etc.
— Fosters technology maturation due to crew observations, video coverage, and uplink of algorithms and downlink of data within days
R&D has gone to great lengths to simulate the space environment in the research laboratory. Now, ISS simulates the research laboratory in space.
SPHERES provides a low cost facility in space for developing & downselecting between algorithms for OE
Current Testing Using SPHERESCurrent Testing Using SPHERES
Single SPHERE maneuver control on the KC-135 in February 2000
Multi-SPHERE formation flight coordination on the KC-135
Multi-SPHERE rendezvous and docking in the SSL 1-G laboratory
Future upgrades— Emulate docking with a target
vehicle in free drift— Emulate a thruster failure in
resupply vehicle— Once docked, autonomously
identify new inertia properties and reconfigure control
— Replace velcro with more advanced docking capability
Current Testing Using SPHERESCurrent Testing Using SPHERES
Single and Multiple SPHERES units maneuvers in the KC-135, February and March 2000
— Testbed Validation— Initial Formation Flight
Current Testing Using SPHERESCurrent Testing Using SPHERES
One-g SSL Laboratory Experiment— Development of 3DOF rendezvous and docking using global coordinates
Relevance to DARPA’s Orbital Express (I)Relevance to DARPA’s Orbital Express (I)
Orbital Express must demonstrate three key features
— (1) fuel transfer, (2) avionics upgrade & (3) routine auto. rendezvous & docking
— These are essential to replenishment, inspection, and repair of existing assets to lengthen life, recover from partial failures, upgrade technologies, and identify causes
Fuel transfer demonstrated in Shuttle’s payload bay
Avionics upgrade performed by astronauts on the Hubble Space Telescope: human-in-the-loop
Rendezvous and docking demonstrated in limited forms
— Manual human-in-the-loop with Shuttle to MIR and ISS
— Automated with human-supervisory-control of Progress to MIR
Orbital Express requires routine autonomous rendezvous & docking
— Without human supervision— With ability to adapt to low level
anomalies— That can accommodate cooperative, non-
cooperative, and eventually un-cooperative target vehicles
Routine autonomous rendezvous & docking is the most immature
Routine autonomous rendezvous & docking raises several questions
— How does the problem change as different information becomes available from the two vehicles?
— Both vehicles communicate and coordinate their motion
— Target nulls residual velocities while docking vehicle performs all maneuvers
— Docking vehicle must match residual motion of non-cooperative target
— Can safe mode and recovery logic be developed that requires minimal human intervention?
— Can autonomous close proximity operations avoid collision and plume impingement?
These define a wide design space which must be explored before committing these algorithms to OE flight demonstration
The SPHERES Autonomous Rendezvous and Docking Testbed can be used to mature these algorithms in an environment that:
— Provides long duration micro-G for close proximity operations
— Is risk tolerant by allowing IFM and replenishment of consumables
— Has access to video coverage and Ku-Band (up)downlink facilitating iterative algorithm refinement
— Has low cost and high visibility
Relevance to DARPA’s Orbital Express (II)Relevance to DARPA’s Orbital Express (II)
SPHERES (AFRL-0012) SPHERES (AFRL-0012) DETAILED OVERVIEWDETAILED OVERVIEW
FLIGHT SYSTEM— Flight H/W (fits in 1-1.5 middeck lockers)
— 3 SPHERES, 4 metrology transmitters, 1 laptop (GFE)
— SPHERE satellite contents — CO2 propulsion tank, RF
communication, IR-ultrasonic global metrology, Inertial Measurement Unit (IMU), AA battery power
— Researcher uplinks algorithms, crew down-loads from laptop, crew initiates test and replenishes consumables, crew downloads and downlinks data to ground, researcher reviews data and refines algorithms, researcher uplinks refined algorithms. Cycle completed in days.
STATUS— Currently manifested on ISS-9a in May 2002
for 4-6 months on ISS.
— High fidelity prototype built & operating in lab & KC-135, Phase 0/1 Safety Package complete, EMI tests conducted
PRIORITY — DoD SERB rank 15/34— AF SERB rank 9/14
FUNDING NEEDED— Need $900k to transition from high
fidelity prototype to operation on ISS
— Flight hardware fabrication, STS-ISS integration, operations
— Potential non-DARPA sources include NASA ST-6 proposal & SBIR, and Lockheed & AFRL
SPHERES Team CapabilitySPHERES Team Capability
MIT Space Systems Laboratory— David W. Miller
— Formation flight, rendezvous and docking research in support of Techsat21, ST-3, Terrestrial Planet Finder
— Design and PI of 0-g dynamics and controls laboratories
MODE STS-40, 48, 62 DLS on MIR MACE STS-67, 106, ISS
— Jonathan P. How— Formation flight, differential
GPS, robust control— Brian Williams
— Spacecraft autonomy, remote agent, Livingstone autonomous model-based diagnosis on DS-1
Payload Systems Incorporated— Developer and integrator of
experiments in human-rated space platforms (Shuttle, MIR, ISS)
The fact that our facilities have more reflights first flights is testimony to the versatility of, and demand for, our dynamics and controls laboratories