Using the International Space Station as an Engineering Technology Research Laboratory for Space Based Telescopes

Transcription

1 Using the International Space Station as an Engineering Technology Research Laboratory for Space Based Telescopes David W. Miller Director, Professor, MIT Dept. of Aeronautics and Astronautics Javier de Luis Visiting Engineer, Chief Scientist, Payload Systems Incorporated Jeffrey A. Hoffman Professor, MIT Dept. of Aeronautics and Astronautics ISS for Space Based Telescopes - Page No.1

2 Motivation International Space Station can support future space telescopes in multiple roles: For technology development For construction For demonstration and validation As a technology development laboratory, it provides many capabilities which are attractive to experimenters: Infrastructure: provides communication, power, video, mounting, attitude control, etc. Upgradability/Retrievability: experiments can be modified either on-orbit or retrieved for modifications on the ground Crew Access: crew can perform functions (reconfiguration, refueling, recharging, troubleshooting, etc.) which do not have to be automated and built into experiment. These capabilities are features of ISS which do not have to be built into (and therefore paid for) by the individual experiments. ISS for Space Based Telescopes - Page No.2

3 Motivation (cont.) Fabrication of space telescopes can occur at or near ISS: EVA or robotic assembly can be used. Allows for recovery from failures and checkout of telescope prior to deployment to final orbit Contamination, and orbital transfer to final orbits could be issues with some telescope designs. Even if fabrication at ISS is not desired, the station can be used to demonstrate techniques needed for space telescope deployment Robotic assembly demonstration prior to launch of operational spacecraft EVA assembly, assuming future human presence at Lagrange points ISS is a technology development laboratory with a wide array of capabilities that can support future space telescope missions ISS for Space Based Telescopes - Page No.3

4 Experiments to Support Space Telescope Missions What kind of technology needed by future space telescopes could be tested using the ISS? Some examples: Deployable/Erectable Systems Human assembled components and systems Robotic assembly or deployment. Automatic deployment or unfolding of large telescopes For all these operations, humans can monitor operations, and assist in case of mishaps. Support systems Electric propulsion testbeds Dynamics and control of structures, including non-linear behavior Laser communication Instrumentation (star trackers, positioning systems, etc.) Optical Metrology Exposure facility Mirrors, detectors, actuators, etc. ISS for Space Based Telescopes - Page No.4

5 What Kinds of Experiments Should Be Conducted on ISS? Experiments can be conducted in support of any of the following needs: Demonstration and Validation Sometimes provides only acceptable information for a go/no-go decision Can be conducted on component, sub-system, or system-level hardware Repeatability and Reliability Develop technology heritage and confidence by demonstrating reliable and repeatable behavior Determination of Simulation Accuracy Calibrates a simulator and reveals additional features that need to be modeled Can be performed throughout the lifetime of the project, in particular early in the concept development phase where real data can be extremely limited. Identification of Performance Limitations Can result from sensor-actuator dynamics, modes in roll-off region, and noise Performance limitations can depend on test conditions, which may only be duplicated in space. ISS for Space Based Telescopes - Page No.5

6 Why Conduct Experiments on ISS? (cont.) Operational Drivers Power consumption, saturation, drift, etc. become part of the control design Often these only become apparent as the testing environment approaches reaches a higher fidelity which can only be duplicated on orbit. Process Development Experience refines system identification, refinement, and implementation processes Reconfigurability, crew presence allows rapid turn-around for process changes. Investigation of New Physical Phenomena Identify gravity-dependent non-linearity, relaxation errors, etc. Early identification of unknown unknowns. ISS experiments support the hardware design and testing as well as the mission operational development ISS for Space Based Telescopes - Page No.6

7 Past Experience MIT and other universities (e.g., U. of Colorado, U. of Maryland), along with their industrial partners, have conducted a wide range of technology experiments on-board Shuttle, Mir, and ISS Average project duration from contract start to flight was under 3 years. Average cost was approximately $2 M Integration and flight hardware fabrication difficulties were minimized through the use of experienced personnel from industrial partners Individual experiments were designed with generic as well as unique components, allowing easy modification and re-flight of hardware at much lower costs. ISS for Space Based Telescopes - Page No.7

8 Examples Experiment Cost ($M) Contract Start to Flight (years) On-Orbit Time (weeks) Technology Research Area MODE Microgravity fluid and structural dynamics tested on scaled test articles MODE-R Non-linear structural dynamics on truss structure DLS Crew-induced dynamic disturbance isolation MACE Advance control design on non-linear structure MACE-R Neural net, non-linear control design SPHERES (expected) 40 + (expected) Rendezvous and docking, satellite constellation ops. MADE 4 (not presently funded for flight) 40 + (planned) Nano-accuracy deployment testbed. ISS for Space Based Telescopes - Page No.8

9 Acronyms and Experiment Dates Middeck 0-g Dynamics Experiment (MODE) [ STS-48, September 1991] Middeck 0-G Dynamics Experiment Reflight (MODE-Reflight) [STS-62, March 1994] Dynamic Load Sensors (DLS) [MIR Space Station, ] Middeck Active Control Experiment (MACE) [ STS-67, March 1995] Middeck Active Control Experiment Reflight (MACE-Reflight) [ISS, September 2000 to August 2001] Synchronized Position, Hold, Engage, Reorient Experimental Satellites (SPHERES) Scheduled for launch to ISS in July, 2003 Micron-Accuracy Deployment Experiment (MADE) In development by the University of Colorado Not presently funded for flight ISS for Space Based Telescopes - Page No.9

10 Middeck 0-G Dynamics Experiment Calibrate non-linear, gravity-dependent dynamic models of fluid slosh and truss structures Testbed features: Data storage, operator interface, power amplification, signal conditioning and experiment control functions placed in ESM Shared between FTA and STA tests ESM re-used on subsequent flights Reconfigurable: Seven different test articles tested Four FTAs for testing silicon oil and water in two different geometry tanks Three STA geometries made from deployable and erectable truss segments as well as a variable friction alpha joint Reconfiguration capability using astronauts maximized research return Experiment Support Module (ESM) & Fluid Test Article (FTA) Structural Test Article (STA) ISS for Space Based Telescopes - Page No.10

11 Middeck Active Control Experiment Develop D&C tools for predicting & refining robust, multi-variable control on systems that cannot be fully tested in 1-G The 1.5 meter test article had two 2-axis gimbals, a reaction wheel triax, 9 actuators, 20 sensors, & 80 state controllers at 500Hz. Ku-Band access allowed data down-link and algorithm up-link Risk-Tolerant Design accommodated unstable behavior Software Reconfiguration Permitted test of different algorithm types Human Observation & Manipulation Crew relayed observations, altered test sequence & down-linked select video Facilitate Iterative Research Process (Up)down-link allowed five redesign cycles over two week mission Experiment Support Module Test Article on Middeck ISS for Space Based Telescopes - Page No.11

12 MACE-Reflight Collaboration between AFRL and MIT First crew-interactive experiment on the International Space Station Research ranged from neural networks to adaptive reaction wheel isolation to nonlinear dynamic modeling Hardware modified with flexible appendages attached to gimbal faces Multiple Investigators Both MIT and AFRL brought university, industry and government guest investigators Identical hardware on ground allowed modeling & software issues to be resolved prior to up-link Not having PI on call during operations lengthens anomaly resolution time ISS for Space Based Telescopes - Page No.12 Operations Inside ISS

13 SPHERES Risk-tolerant laboratory for maturing metrology, control, and autonomy technologies for formation flight and rendezvous and docking missions. Launch to ISS in mid 03. Hardware Reconfiguration Several interfaces on each SPHERE allows peripherals to be attached Re-supply missions can brink optical elements, docking ports, cameras, etc. Risk Tolerant Environment If prematurely expel propellant, collide, or go unstable, crew terminates experiment, fixes problem, and proceeds. The SPHERES design recognizes that no research experiment is free of anomalies. Facilitating Iterative Research Process Laptop (GFE) used to program SPHERES and archive state data. Laptops have access to Ku-Band system allowing uplink of algorithms and down-link of data Supporting Multiple Investigators Perhaps most challenging aspect is supporting a vibrant guest investigator program. Models, simulations, interface definitions, 1-g testing, video coverage, etc. are all aspects of such a program. ISS for Space Based Telescopes - Page No.13

14 MADE (L. Petterson, U. of Col.) Optical telescopes need to be stable to nanometers of precision for long periods Microscopic loss of friction in the deployment mechanisms leads to loss of stability Ground research tells us these instabilities are: DC (quasi-static) to KHz in frequency 1 nanometer to 10 microns in size Excited by mechanical or thermal loads Expected to change from 1-g to 0-g MADE allows testing of: Deployment Repeatability Long-Term Structural Stability Stability Under Mechanical and Thermal Loads Effectiveness of Active Control Schemes Correlate 1-g to 0-g via Theoretical Models Low Cost, Low Risk: Attaches to ISS Truss (Express pallet) Swapped out by Shuttle Software reconfigurable Multiple test articles 1/4-Scale Model Deployable Mirror Petal on MADE Full-Scale Precision Mechanisms ISS for Space Based Telescopes - Page No.14

15 Summary Future space telescopes will be expensive and risk-intolerant Designs are conservative and few if any tests are conducted that stretch capabilities or explore variations Many systems and components will not get tested in a representative environment until late in the maturation process Difficult to comprehensively validate prior to launch System level free-flying technology demonstrations extremely expensive There is a need to incrementally test technologies in a representative environment earlier in the maturation process ISS provides unique laboratory setting for these tests Long duration space environment Risk-tolerant environment Repair, replenish, upgrade Existing infrastructure ISS technology experiments can be conducted in a cost and time-effective manner and should be considered for maturing technology in support of space telescopes. ISS for Space Based Telescopes - Page No.15