Hundreds of man-made satellites are currently in orbit around the Earth. Over the next decade, governments and companies around the globe plan to launch hundreds of new spacecraft for a variety of communications, defense and remote sensing projects. The placement of satellites into Earth orbit can cost many millions of dollars. A conventional launch involves a large multi-stage, single-use rocket to lift a satellite into a geosynchronous orbit.
A general description of conventional nuclear-propulsion systems may be found in a text entitled A Critical Review of Space Nuclear Power and Propulsion, edited by Mohamed S. El-Genk, which was published by the American Institute of Physics in 1994.
The U.S. Departments of Energy and Defense and NASA developed plans for a Generic Flight System for space-based defense systems and NASA exploration missions called SP-100 in the mid-1980's. The SP-100 was designed to supply nuclear-power for military and civilian space systems. This early system was designed as a single-use power stage for a single, permanently attached payload; and was never configured for any on-orbit rendezvous, docking or servicing missions. The SP-100 is described in the SP-100 Technical Summary Report, which was prepared for the U.S. Department of Energy by the Jet Propulsion Laboratory and the California Institute of Technology in September, 1994.
Various nuclear electric propulsion systems are described in a publication entitled Nuclear Electric Propulsion, A Summary of Concepts Submitted to the NASA/DoE/DoD Nuclear Electric Propulsion Workshop, which was held in Pasadena, Calif. on 19–22 Jun. 1990.
The Aerospace Division of the Olin Corporation proposed a small engine for the small satellite community called the Small Upper Stage (SUS). The SUS was designed to accomplish low Earth orbit transfers, orbit circularizations and plane changes using hydrazine propulsion.
TRW has patented several methods and apparatus intended for the space transportation market. In U.S. Pat. No. 4,471,926, Steel describes a Transfer Vehicle for Use in Conjunction with a Reusable Space Shuttle. This spacecraft has a propulsion system that uses a low-thrust bi-propellant liquid rocket engine to provide a soft, low-acceleration ascent. In U.S. Pat. No. 4,575,029, Harwood and Love disclose a spacecraft for transporting a payload from a space shuttle in a low altitude parking orbit to an operational orbit. In U.S. Pat. No. 4,943,014, Harwood and Love reveal their “soft ride” method for changing the altitude or position of a spacecraft in orbit using a liquid bi-propellant engine.
In U.S. Pat. No. 4,664,344, Harwell describes an apparatus and method of capturing an orbiting spacecraft. This device comprises a relatively small mechanical probe and fixture operated by an astronaut during a spacewalk.
In an article entitled Topaz Two Proves to Be a Gem for International Tech Transfer, contained in Technical Applications Report from Ballistic Missile Defense Organization, 1995, thermoionic reactors for space-based power generation are disclosed.
Prospects for Nuclear Electric Propulsion Using Closed-Cycle Magnetohydrodynamic Energy Conversion, by R. Litchford et al. was presented at the 12th Annual Advanced Space Propulsion Workshop in Huntsville, Ala. on 3–5 Apr. 2001.
J. Collins et al. disclose a Small Orbit Transfer Vehicle for On-Orbit Servicing and Resupply which was presented at the 15th Annual Utah State University Conference on Small Satellites at Logan, Utah, 13–16 Aug. 2001.
In U.S. Pat. No. 4,754,601, Minovitch discloses “a propulsion system for reusable space-based vehicles is presented wherein the propulsive working fluid is atmospheric gas.”
In U.S. Pat. No. 5,260,639, De Young et al. describe “a method of supplying power to a device such as a lunar rover located on a planetary surface.”
In U.S. Pat. No. 6,213,700, Koppel discloses a “method [which] serves to place a space vehicle, such as a satellite, on a target orbit such as the orbit adapted to normal operation of the space vehicle and starting from an elliptical initial orbit that is significantly different from, and in particular more eccentric than the target orbit.”
In U.S. Pat. No. 6,357,700, Provitola describes “an spacecraft/airship, which uses buoyancy and thrusters to ascend into space with lifting gas as propellant or fuel for thrusters, which may be conventional thrusters or electric turbojets or ion thrusters.”
In U.S. Pat. No. 5,260,639, Basuthakur et al reveal “a satellite assembly [that] is formed from any number of bus modules which have a substantially common shape and interior space volume.”
In U.S. Pat. No. 6,478,257, Oh et al. describe “systems and methods that employ a phase change material to provide thermal control of electric propulsion devices.”
In U.S. Pat. No. 3,825,211, Minovitch presents a “space vehicle [which] carries a vaporizable propellant . . . [E]nergy is transmitted to the vehicle while in space by a laser beam originating on the ground or some other body or satellite.”
The development of an in-orbit space transportation and rescue vehicle would dramatically reduce the cost of changing the orbital position of a satellite. Such a system would revolutionize the military and commercial space industries, and fill a long-felt need in the telecommunications, direct-broadcast and remote-sensing industries.