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

millerd@mit.edu

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