Martin Sweeting

Cost effective propulsion systems for small satellites using butane propellant

Abstract This paper will describe the work performed at the Surrey Space Centre to produce cost effective propulsion systems for small spacecraft with relatively low deltaV (ΔV) requirements. Traditionally, cold gas nitrogen systems have been used for this type of application, however they have high storage volume requirements. This can be a problem on small spacecraft, which are typically volume limited. An alternative solution is to use liquefied gases, which store as liquids, hence have reasonable density levels, and can be used in a cold gas thruster. At the Surrey Space Centre, butane has been selected as the propellant of choice. Although it has slightly lower specific impulse performance than nitrogen, it has a significantly higher storage density and it stores at a very low pressure, hence no regulation system is required. On 28th June 2000 Surrey Satellite Technology Ltd (SSTL) launched it first nanosatellite SNAP-1. This 6.5kg spacecraft was equipped with a small cold gas propulsion system utilising 32.6 grams of butane propellant. During the propulsion system operation phase the spacecrafts semi major axis was raised by nearly 4 kilometers using the propulsion system. The design of the propulsion system will be described and the low cost features highlighted. Telemetry data will be used to describe the propulsion operations and an overall mission specific impulse will be derived. 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 ΔV requirement of 10 m/sec. A butane system has been 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, with the addition of greater propellant storage capacity. The lessons learnt from the SNAP-1 operation will be reviewed and the resulting design improvements on the DMC propulsion systems will be detailed.

25 YEARS OF SPACE AT SURREY—PIONEERING MODERN MICROSATELLITES

Abstract Space at Surrey has developed over 25 years from very modest beginnings in 1974 to an international space centre by 1998. It has pioneered small satellites and succeeded in launching 14 low cost but sophisticated microsatellites over the course of two decades. In the 1990s, small satellites have become fashionable—but this was not always so! This paper describes the 25 years history of “Space at Surrey”.

Low cost lunar orbiter system design

Lunar and interplanetary missions are extraordinarily expensive. Previous missions have cost hundreds of millions of dollars and for this reason were primarily the domain of large national space agencies. However, in recent years a trend has developed in which missions have become more affordable giving rise to a new world of space faring nations. Surrey Satellite Technology Ltd (SSTL) has been at the forefront of providing affordable access to space for a range of Low Earth Orbit (LEO) mission since 1979. Extending this philosophy to a lunar mission will demonstrate a new affordable lunar and interplanetary platform. This paper aims to summarize SSTLs interest and experience of missions beyond LEO. It outlines the current status of he low cost lunar orbiter system design, detailing the principle design drivers, platform budgets including overall mission cost and outline mission level trade-offs which effect cost the most. It assesses low cost launch options and makes a recommendation for a unique initial launch orbit. A practical Earth departure and lunar capture trajectory is proposed along with a cost-effective operations concept. While this research primarily focuses on platform demonstration the opportunity to undertake science has not been overlooked. This design for low-cost approach is challenging. However, the largely commercial off-the-shelf (COTS) system design, in part developed from the successful SNAP-1 nanosatellite avionics, suggests the mission is feasible for both low cost (

Integrated Semiempirical Methodology for Microvibration Prediction

25million dollars) and low risk.

UK Lunar Science Missions: Moonlite & Moonraker

In this paper, a full methodology to deal with microvibration predictions onboard satellites is described. Two important aspects are tackled: 1)xa0the characterization of the sources with a pragmatic procedure that allows integrating into the algorithm the full effect of the sources, including their dynamic coupling with the satellite structure; 2)xa0the modeling of the transfer function source receivers with a technique named in this paper as the Craig–Bampton stochastic method, which allows prediction of a nominal response and variations due to structural uncertainties as accurate as full Monte Carlo simulations but at a fraction of the computational effort. The paper then includes a statistical study of the data from the structural dynamic testing of the five identical craft of the Rapid-Eye constellation to set the magnitude of the uncertainties that should be applied in the analysis. Finally, the computational procedure is applied to the new high-resolution satellite SSTL-300-S1 and the predictions compa...

TMSAT: Thailand's first microsatellite for communications and earth observation

It has been 35 years since the last human presence on the Moon. Since then, our knowledge of the Solar System has expanded immeasurably, bringing us up against questions that are impossible to answer on Earth. There is now a global renewed interest in returning to the Moon, driven by the demands of science and as a stepping-stone for human exploration of the Solar System. The Moon provides a unique record of processes affecting evolution of terrestrial planets in early Solar System history (the first Gyr or so). This includes internal processes of geological evolution (e.g. differentiation and the first formation of a crust) and external processes caused by the environment (e.g. meteorite flux, interplanetary dust density, solar wind flux and composition, galactic cosmic ray flux) that are not as easily accessible anywhere else in our solar system.

CERISE microsatellite recovery from first detected collision in low Earth orbit

Abstract Mahanakorn University of Technology (Thailand) and the University of Surrey (UK) have commenced a collaborative programme in microsatellite technology transfer and training. The programme will train 12 young engineers in satellite engineering techniques at Surrey and will design and build Thailands first microsatellite (TMSAT) for launch into low Earth orbit in mid-1997. TMSAT will carry multi-spectral Earth observation cameras and digital store-&-forward communications payloads making extensive use of advanced on-board processing and autonomous GPS positioning techniques.

Space education through earth-orbiting satellites

Abstract The first ever collision between two catalogued space objects was detected in low Earth orbit in July 1996. After one year of perfect operation in space, controllers at the Space Mission Control Groundstation, Surrey Space Centre, UK observed a sudden change to the attitude dynamics of the CERISE microsatellite as it tumbled rapidly end-over-end in its 700 km polar Earth orbit. After initial investigations, a collision with a piece of space debris was suspected. The paper describes the analysis of the collision dynamics and the subsequent re-programming of the on-board computers with novel magnetic control algorithms to re-stabilise the otherwise undamaged microsatellite and regain almost full operational mission capability.

LunarEX-a proposal to cosmic vision

Abstract This paper outlines the criteria for the effective introduction of space education through satellites. It proceeds to outline the initiatives that are currently taking place within the U.K., that are aimed at meeting these criteria. In particular the role of the UoSAT Spacecraft Engineering Research Programme is examined, together with that of the U.K. Satellites in Education Programme - both operated from the University of Surrey, Guildford, England.