| PROPOSAL NUMBER: | 02-II A5.03-9245 (For NASA Use Only - Chron: 022754 ) |
| PHASE-I CONTRACT NUMBER: | NAS8-03014 |
| SUBTOPIC TITLE: | Nuclear and Exotic Propulsion |
| PROPOSAL TITLE: | A Grid-Sphere Electrode for Tether Current Collection |
SMALL BUSINESS CONCERN:
(Firm Name, Mail Address, City/State/ZIP, Phone)
SRS Technologies
1800 Quail Street, Suite 101
Newport Beach , CA 92660 - 0000
(256 ) 971 - 7000
PRINCIPAL INVESTIGATOR/PROJECT MANAGER:
(Name, E-mail, Mail Address, City/State/ZIP, Phone)
Dr. Nobie H. Stone
nstone@stg.srs.com
500 Discovery Drive
Huntsville , AL 35806 - 9999
(256 ) 971 - 7029
TECHNICAL ABSTRACT (LIMIT 200 WORDS)
The Grid-Sphere is a passive electrode contactor that relies on a very large area to allow the collection of large currents from the ionosphere. Dynamic drag is minimized by using a grid construction. This Grid-Sphere can provide electrodynamic tethers with the ability to passively collect arbitrarily large currents at the positive pole?requiring only low bias voltages. This makes current collection independent of tether length and eliminates hazardous high-voltage operations. The Phase-1 results include the development of grid-film materials with the required characteristics and the derivation of a linearized model of the current collection process?and clearly show the Grid-Sphere to be feasible and to collect current with virtually the same efficiency as a solid-surface spherical electrode of the same radius.
POTENTIAL NASA COMMERCIAL APPLICATION(S) (LIMIT 150 WORDS)
The Grid-Sphere electrode will be an attractive addition to space tether technology because it will allow the collection of arbitrarily large currents with arbitrarily short tether systems while maintaining very low dynamic drag. These characteristics will be enabling to applications such as the Tether Reboost System that has been proposed as a alternative means of reboosting and maintaining the orbit of the International Space Station?where the micro-gravity environment must be maintained, thereby prohibiting long tethers. It will also be a valuable asset for the MXER Tether Launch System concept being proposed as a low-cost alternative to second-stage boosters for missions requiring launch into deep space. In this case, high-power electrodynamic reboost of the MXER system will be essential to achieve efficiencies competitive with alternative launch technologies.
POTENTIAL NON-NASA APPLICATION(S) (LIMIT 150 WORDS)
The Grid-Sphere Electrode relies on deploying a very large-scale spherical body of 10 to 20 meters or more in radius. Dynamic drag is minimizing by using a grid construction so that orbital lifetime may be very long?even in LEO. The Grid-Sphere can, therefore, be used as a very large RF antenna that could remain in LEO for long periods of time. Grids can be upwards of 90-percent transparent, in order to minimize drag, and still allow grid spacings ranging from sub-millimeter to several centimeters to be used. Grid spacing can, therefore, be selected to match the frequency range of the RF band used. Placing such an antenna in LEO would minimize the distance to mobile ground-based transmitters, thereby reducing transmitter power requirements and improving receiver sensitivity.