SPACECRAFT PROPULSION - KTH

- 38 -ConclusionBipropellant systems are more complex and therefore moreexpensive than monopropellant hydrazine systems. However, theirpotential high system costs is compensated by their higher impulseperformance (high I ssp ) resulting in lower propulsion mass fractionallowing a higher payload mass. Therefore, bipropellant systems aremainly used for commercial spacecrafts with missions of highimpulse requirements. E.g. for geostationary communicationsatellites, they form a single unified propulsion system, givingmaximum flexibility in the shared use of the propellant between theorbit transfer operation, as well as the apogee and attitude controlfunctions.ADVANTAGES:- high I sp : ( 2900 Ns/kg) for F 25 N, I ssp ( 2800 Ns/kg)( 3110 Ns/kg) for F 500 N,- high thrust capability, - up to 45 000 N.DISADVANTAGES:- system complexity with added valves, regulators, etc.;- higher cost in comparison to monopropellant hydrazine systems.