Leslie Curtis

Propulsive Small Expendable Deployer System (ProSEDS)

Space Transportation Directorate, National Aeronautics and Space Administration, Marshall Space Flight Center,AL 35812, 256-544-2486, leslie.curtis@msfc.nasa.gov; 256-544-0614, les.johnson@msfc.nasa.govAbstract. The Propulsive Small Expendable Deployer System (ProSEDS) space experiment will demonstrate the use of anelectrodynamic tether propulsion system to generate thrust in space by decreasing the orbital altitude of a Delta IIExpendable Launch Vehicle second stage. ProSEDS, which is planned on an Air Force GPS Satellite replacement missionin June 2002, will use the flight proven Small Expendable Deployer System (SEDS) to deploy a tether (5 km bare wire plus10 km non-conducting Dyneema) from a Delta II second stage to achieve --q3.4Ndrag thrust. ProSEDS will utilize thetether-generated current to provide limited spacecraft power. The ProSEDS instrumentation includes Langmuir probes andDifferential Ion Flux Probes, which will determine the characteristics of the ambient ionospheric plasma. Two GlobalPositioning System (GPS) receivers will be used (one on the Delta and one on the endmass) to help determine tetherdynamics and to limit transmitter operations to occasions when the spacecraft is over selected ground stations. The flightexperiment is a precursor to the more ambitious electrodynamic tether upper stage demonstration mission, which will becapable of orbit raising, lowering and inclination changes-all using electrodynamic thrust. An immediate application ofProSEDS technology is for the removal of spent satellites for orbital debris mitigation. In addition to the use of thistechnology to provide orbit transfer and debris mitigation it may also be an attractive option for future missions to Jupiterand any other planetary body with a magnetosphere.

Review of the ProSEDS Electrodynamic Tether Mission Development

The Propulsive Small Expendable Deployer System (ProSEDS) space experiment was ready to fly as a secondary payload on a Delta–II expendable launch vehicle in late March 2003. Concerns raised by the International Space Station (ISS) after the February 2003 Columbia shuttle accident resulted in the delay of the launch of ProSEDS. Issues associated with both the delayed launch date and a change in starting altitude resulted in the ultimate cancellation of the mission. ProSEDS was intended to deploy a tether (5-km bare wire plus 10-km non-conducting Dyneema) from a Delta–II second stage to achieve adequate electrodynamic drag thrust that would lower the orbit of the system over days—as opposed to months due to atmospheric drag. The experiment was also designed to utilize the tether-generated current to provide limited spacecraft power. Considerable effort and testing went into developing the ProSEDS system by a dedicated team. Throughout this effort, important technological issues were identified and addressed and this paper discusses some of the important technical issues and hurdles that had to be addressed to successfully prepare for flight. It is intended that this information will be of use for future tether mission and experiment designers.

Development of the flight tether for ProSEDS

The Propulsive Small Expendable Deployer System (ProSEDS) space experiment will demonstrate the use of an electrodynamic tether propulsion system to generate thrust in space by decreasing the orbital altitude of a Delta II Expendable Launch Vehicle second stage. ProSEDS will use the flight-proven Small Expendable Deployer System to deploy a newly designed and developed tether which will provide tether generated drag thrust of ∼0.4 N. The development and production of very long tethers with specific properties for performance and survivability will be required to enable future tether missions. The ProSEDS tether design and the development process may provide some lessons learned for these future missions. The ProSEDS system requirements drove the design of the tether to have three different sections of tether each serving a specialized purpose. The tether is a total of 15 kilometers long: 10 kilometers of a non-conductive Dyneema lead tether; 5 km of CCOR conductive coated wire; and 220 meters of insulated...