Advanced propulsion for geostationary orbit insertion and north-south station keeping

Abstract

Solar electric propulsion technology is currently being used for geostationary satellite station keeping.Analyses show that electric propulsiou technologies can be used to obtain additional increases in payload mass by using them to perform part of the orbit transfer.Three electric propulsion technologies are examined at two power levels for geostationary insertion of an Atlas llAS class spacecraft.The onboardchemical propulsion apogee engine fuel is rednced in this analysis to allow the use of electric propulsion.A uumerical optimizer is used to determine the chemical bums that will minimize the electric propulsion transfer times.For a lS50-kg Atlas llAS class payload, increases in net mass (geostationary satellite mass less wet propulsion system mass) of 150-800 kg are enabled by using electric propulsion for station keeping, advanced chemical engines for part of the transfer, and electric propulsion for the remainder of the transfer.'nip times are between one and four months.masses, and the launch vehicles to deliyer them, also have grown.Early Intelsats were well under lOoo-kg dry mass.The planned Intelsat 8!8A series will have a 1530-kg dry mass.End-of-life power levels have increased from hundreds of watts for Intelsats 1-4, to over 5 kW for Intelsat 7A.Intelsat 8/8A will use the Lockheed Marietta Astro Space Series 7000 satellite which has a beginningof-life power level over 7 kW.Finally, communication bandwidths on Intelsat spacecraft have increased from 50 MHz on Intelsat 1 to 2856 MHz on the planned Intelsat 8/8A series.These continuing trends toward larger, more capable, longer life and higher-power spacecraft were used to select the spacecraft characteristics in this study.Higher-power spacecraft permit expansion of the use of electric propulsion systems beyond the already-demonstrated station-