Economic Space Transportation

Abstract

SummaryThe paper re-examines the economics of the various types of orbital booster, ranging from completely expendable to completely recoverable vehicles. Previous studies have compared vehicles of equal payload. Here we have introduced the concept of the cost optimum vehicle. It is shown that the lower the degree of recoverability, the larger the optimum payload for a given total payload in orbit. Cost comparisons are then developed using the cost optimum vehicle in each case.Additionally, in our previous work we have confined ourselves to the economics of operating the launch vehicle. A recoverable launch vehicle generally automatically implies a capability for recovering the payload. The case for the recoverable vehicle becomes more and more attractive as the salvage value of the payload increases. The break-even points for a number of Payload Salvage Values (PSV) are presented.Data are included which show the high costs of present day satellite vehicles. These amount to tens of thousands of dollars per lb. If we assume that the PSV of such satellites is $7000 per lb the break-even point for the Aerospace Transporter is about 5 x 105 lb cumulative payload in orbit (COP). The cost of manufacturing such a satellite payload would be upwards of $5000m, which is several times the cost of producing and operating the launching vehicle. It therefore appears unlikely that the Aerospace Transporter will be employed simply to launch conventional satellites. In this connection it should be remembered, however, that the payload capability will revolutionise the approach to satellite design. Attitude control, the structural envelope, etc, will be provided by the launch vehicle in many cases. Thus the mission capability of the payload will be greatly increased. Furthermore, relaxations in payload weight constraints, which could lead to increases in payload reliability and decreases in cost, appear to be possible with such a vehicle.There are, however, some payloads which must be recovered and the most significant of these is man. Once recovery of the payload becomes mandatory the recoverable vehicle is always superior to the expendable vehicle. This is true no matter how small the number of shots. Thus once we are convinced of the future of man in the exploitation of space, the case for the recoverable vehicle (Aerospace Transporter) is unassailable.The capability for recovering the payload should add greatly to the value of other orbital operations. An obvious case is that of photographic reconnaissance. Here we have a mission requiring a large number of regular launches and recovery of at least part of the payload. An economic assessment should show the Aerospace Transporter in a very favourable light. At the end of this section the point is made that, although we can see a great many possibilities for utilisation of the Aerospace Transporter payload, this aspect will be so revolutionised that we feel in need of advice from specialists on a number of questions. For example: What types and sensitivity of sensors will be available in the next 15-20 years? How would a relaxation in the weight restrictions affect payload philosophy? How could the intelligence of man be employed? and the most important question: What would be the value of such operations to agriculture, water management, population control and other activities on earth?The last part of the paper deals with the sensitivity of a number of types of Aerospace Transporter to weight growth and vehicle life. It is shown that VTO vehicles are, if anything, less susceptible to weight growth than HTO vehicles. It is also concluded that there is little point in adding weight to increase the life beyond 50-100 re-uses.