Minimum satellite vehicles
- Paper ID
BIS-51-05
- author
- company
British interplanetary society
- country
United Kingdom
- year
1951
- abstract
One’s first duty in presenting a paper of this kind is to define precisely what is meant by the term, Minimum Satellite Vehicle, as there are clearly several objectives that can be fulfilled by “minimum” rockets designed for specific experimental tasks. In this survey, four vehicles are considered and to obtain a useful comparison between them, we have adopted the following standard parameters: height of orbit, 800 kms. (500 miles) ; propellant, liquid oxygen/hydrazine, specific impulse, 325 seconds. In every case, the rockets are considered as three-step vehicles, with the fourth scheme illustrating the application of Expendable- Tanks; the performance is based on a characteristic velocity of 10km./sec. Accelerations have been taken as Ig. effective at take-off, rising to 6 g. at "all- burnt” for the first and second steps of Schemes A, B and C, whilst in the case of Scheme D, the variation is slightly greater as the result of expendable construction, being between 1 g. and 6'6 g. for the first step and between 1 g. and 7-25 g. for the second step. It may be pointed out that since the third steps will be firing tangentially to the Earth’s surface for all these schemes and are therefore undergoing negligible "g” loss, a low acceleration may be used, which gives the dual advantage of reduced motor weight and more sensitive control of velocity towards the “all-burnt” stage. The “Absolute Minimum Vehicle,” to which we refer as Scheme A, will be designed with the primary object of projecting a body into a closed orbit with a minimum of controlling equipment. This experiment would be of the nature of a first approximation for checking the stability of the orbit in conjunction with tracking radar. Scheme B may be regarded as an extension of Scheme A to allow for a useful payload of 100 kg. (220 lb.), sufficient for the installation of a small multiple-channel telemetering system for recording various data (e.g. cosmic radiation, ultra-violet radiation, ambient temperature, etc.). Scheme C is basically similar to Scheme B, with additional control equipment for obtaining improved accuracy over the final path of the trajectory. Finally, Scheme D illustrates the influence of Expendable-Tank Construction and affords a direct comparison with Scheme C in terms of variation in payload, the all-up weight and weight of control equipment being the same for both projects.