Bantam boosters - The key to small RLVS?

Abstract

Last year, in AIAA-96-2773, this author proposed arguments for the economic and technical benefits of smaller reusable launch vehicles (RLVs) enabled by our assist-stage concepts. In that paper, the author pointed out the potential business advantages of our Space Van concept with a 4 tonne payload relative to a much larger SSTO with a 20 tonne payload. This year, we extend these arguments to a still smaller RLV — our Bantam Van concept with a 400 kg payload. As noted last year, pre-operational investment is the dominant economic consideration for fully reusable launch systems. Assuming a business-investment environment, Third Millennium Aerospace has found that traffic levels must build to more than a few hundred flights per year before recurring operational costs begin to become as important as return on investment. Our studies suggest that this finding is largely independent of vehicle size. As a result of these findings, we do not believe that purely single-stage-to-orbit concepts are viable at this time from the business point of view. SSTOs are technically feasible with current technology if they are large enough, e.g. 800 metric tons gross liftoff mass. Unfortunately this size vehicle is necessarily expensive, considering that rather expensive technology is also required. The author believes that the current market for expendable launch vehicles (ELVs) is basically irrelevant to the new market that is appropriate to RLVs. This compounds the investment problem, since this new market is not likely to develop until an RLV is operational. This results in an extended time to build revenue and therefore makes a large investment impractical to recover without heavy subsidies. However, if one or more smaller RLVs first develop the space transportation market appropriate to RLVs, then it is likely that — eventually — SSTOs will also make sense from the business point of view. Smaller RLVs can build this new market and simultaneously earn appropriate returns on investment (ROI) — even when the time required to build the market is considered. Third Millennium has long advocated assist stage concepts as one of the most promising ways to minimize pre-operational investment. This minimizes the size and complexity of the expensive portion of the system: the orbiter stage. The assist stage is basically a reusable booster that is optimized more for total system cost — rather than for system size and booster performance. As such, this type of reusable booster can be relatively low cost. Moreover, system performance is relatively insensitive to assist-stage performance — which tends to stage at medium supersonic speeds and low dynamic pressures. Accordingly, the assist stage is generally designed for efficient operations and for maximum relief of loads and other requirements on the orbiter stage. RLV size can have a dramatic effect on near-term business potential. At a 26 percent ROI and traffic levels equal to about 100 tonnes per year to LEO — i.e. about 20 percent of current total tonnage to LEO — our analysis shows that the price per flight for each of five flights per year with an SSTO is about 130 times recurring costs. However, the price per flight for each of 250 flights per year with our proposed Bantam Van is less than three times recurring costs. Member, AIAA. Copyright © 1997 by Third Millennium® Aerospace, Inc. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission.