1. Technical Field
This is related to spacecraft, and in particular, to tethered spacecraft.
2. Background Technology
Tethered spacecraft have been developed that include two end bodies and a tether between the end bodies. The spacecraft must have the ability to separate the two end bodies in space.
The Tether Physics and Survivability Satellite (TIPs) was developed by the Naval Research Laboratory, and launched in 1996. The TIPs free flying satellite had two end bodies connected by a four kilometer non-conducting tether, as described in M. L. Cosmo and E. C. Lorini in NASA, Tethers in Space Handbook, third edition, December 1997. The TIPS satellite had a separation mechanism that included a group of springs placed in a circle with a diameter of approximately twelve inches, in the center of the two end bodies. The end bodies were sufficiently massive to allow the use of matching multiple springs to provide the separation energy. However, for smaller end bodies with small masses, any mismatch in the springs can result in large tipoff rates, which can cause the tether to not deploy completely.
R. Ullrich et al., “The STEREO IMPACT Boom”, Space Science Review, Vol. 136, pp. 185-201, 2008 discloses a spacecraft boom formed of telescoping concentric tubes that are pushed outward by a stacer and form a rigid platform for supporting imaging instruments. Another stacer-based system is described in D. Auslander et al., “Instrument Boom Mechanisms on the THEMIS Satellites; Magnetometer, Radial Wire, and Axial Booms”, Space Science Review, vol. 141, pp. 185-211, 2008.
U.S. Pat. No. 6,597,631 to Kitchin et al. discloses a deployment mechanism that includes a stacer for deploying sensors. U.S. Pat. No. 7,178,763 to Licata discloses a passive deployment mechanism for space tethers that includes a tether wound upon a spool and a spring separation mechanism.