Session
Technical Session XI: Orbital Manuvering
Abstract
This paper describes the work performed at the Surrey Space Centre to produce low cost propulsion systems for small spacecraft with relatively low velocity-change (ÄV) requirements. Traditionally, cold gas nitrogen systems have been used for this type of application, however these have high storage volume requirements which can be a problem given the typical volume constraints of small spacecraft. An alternative solution is to use liquefied gases, which store as liquids and hence have reasonable densities, whilst still being suitable for use in a cold gas thruster. Thus, liquefied butane gas has been selected as our propellant of choice: Although it has slightly lower specific impulse than nitrogen, it has a significantly higher storage density, and, conveniently, it stores at a very low pressure, hence no pressure-regulation system is required. On 28th June 2000 Surrey launched its first nano-satellite: SNAP-1. This spacecraft was equipped with a small cold gas propulsion system utilising 32.6 grams of butane propellant, which, since launch, has been used to raise the spacecraft's semi-major axis by over 3 kilometres. In this paper, we describe SNAP-1’s propulsion system, highlighting its low-cost features. Telemetry data are used to illustrate orbital control operations, and to derive an overall mission specific impulse. Surrey Satellite Technology Ltd (SSTL) are currently under contract to build three Earth-observation spacecraft for a Disaster Monitoring Constellation (DMC). Each spacecraft will weigh approx 100 kg and have a ÄV requirement of 10 m/s. A new butane system is being designed and manufactured to meet the requirements of these spacecraft. The system is based very much on the flight heritage of the SNAP-1 system, but with the addition of greater propellant storage capacity. The lessons learnt from SNAP-1 operations are reviewed and the resulting design improvements for the DMC propulsion system are detailed.
Low Cost Butane Propulsion Systems for Small Spacecraft
This paper describes the work performed at the Surrey Space Centre to produce low cost propulsion systems for small spacecraft with relatively low velocity-change (ÄV) requirements. Traditionally, cold gas nitrogen systems have been used for this type of application, however these have high storage volume requirements which can be a problem given the typical volume constraints of small spacecraft. An alternative solution is to use liquefied gases, which store as liquids and hence have reasonable densities, whilst still being suitable for use in a cold gas thruster. Thus, liquefied butane gas has been selected as our propellant of choice: Although it has slightly lower specific impulse than nitrogen, it has a significantly higher storage density, and, conveniently, it stores at a very low pressure, hence no pressure-regulation system is required. On 28th June 2000 Surrey launched its first nano-satellite: SNAP-1. This spacecraft was equipped with a small cold gas propulsion system utilising 32.6 grams of butane propellant, which, since launch, has been used to raise the spacecraft's semi-major axis by over 3 kilometres. In this paper, we describe SNAP-1’s propulsion system, highlighting its low-cost features. Telemetry data are used to illustrate orbital control operations, and to derive an overall mission specific impulse. Surrey Satellite Technology Ltd (SSTL) are currently under contract to build three Earth-observation spacecraft for a Disaster Monitoring Constellation (DMC). Each spacecraft will weigh approx 100 kg and have a ÄV requirement of 10 m/s. A new butane system is being designed and manufactured to meet the requirements of these spacecraft. The system is based very much on the flight heritage of the SNAP-1 system, but with the addition of greater propellant storage capacity. The lessons learnt from SNAP-1 operations are reviewed and the resulting design improvements for the DMC propulsion system are detailed.
