PROPOSAL NUMBER 00-1 03.02-9726 (Chron: 000275 )
Stabilization of Electrodynamic Space Tethers

Electrodynamic tether propulsion can provide propellantless propulsion capability for a number of important missions in LEO, including stationkeeping for small satellites, boosting of the International Space Station, deorbit of malfunctioning satellites, and orbit raising of payloads. Theoretical analyses, however, indicate that electro-dynamic tethers will experience dynamical instabilities in which the electro-dynamic forces continually pump energy into the tether librations and oscillations. Unless these dynamics are controlled, these instabilities will lead to reduced thrust efficiency and, at worst, loss of control of the tether system. The proposed SBIR effort will develop methods for reliably monitoring the dynamics of both conducting and nonconducting tether structures, and develop control algorithms for stabilizing the dynamical behavior of electro-dynamic tethers. The effort will evaluate several different methods for accomplishing the dynamics monitoring and control, and select for further development the method that provides the optimum balance between reliable control and low hardware and computational costs. The SBIR effort will result in a tether dynamics control package, composed of both dynamics-sensing hardware and feedback control software algorithms, that will enable electro-dynamic tether systems such as propellantless orbital transfer, ISS tether reboost, momentum-exchange/electro-dynamic-reboost tether facilities, and microsatellite stationkeeping to operate safely and effectively.

The Tether Control System will find commercial applications in a number of electro-dynamic tether systems. The Boeing Company is currently investigating electro-dynamic reboost of the International Space Station, and MirCorp is planning on using an electro-dynamic tether to maintain the orbit of the MIR Space Station. Tethers Unlimited, Inc. is developing a small electro-dynamic tether to provide stationkeeping and formation flying propulsion for microsatellites, and is developing an electro-dynamic drag tether system for end-of-life deorbit of spacecraft. Tethers Unlimited is also collaborating with the Boeing Company to develop momentum-exchange/electro-dynamic-reboost tether facilities for propellantless in-space propulsion and as components of an Earth-to-Orbit launch architecture. Other companies are pursuing electro-dynamic tethers for LEO orbital tug applications. All of these applications of electro-dynamic tethers will require a reliable and low cost system for stabilizing the dynamics of the tether system and for optimizing its long-term efficiency. In addition, Tethers Unlimited, Inc. is collaborating with Mirada, Inc. to develop tethered unmanned gliders for high-angle and over-the-horizon sensing for commercial applications such as the fishing industry, law enforcement, and customs enforcement. The proposed SBIR effort is expected to contribute to this spin-off application of the space tether technologies.

NAME AND ADDRESS OF PRINCIPAL INVESTIGATOR (Name, Organization Name, Mail Address, City/State/Zip)
Robert Hoyt
Tethers Unlimited, Inc.
1917 NE 143rd
Seattle , WA   98125 - 3236

NAME AND ADDRESS OF OFFEROR (Firm Name, Mail Address, City/State/Zip)
Tethers Unlimited, Inc.
8114 Pebble Ct.
Clinton , WA   98236 - 9240