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Mission Effectiveness Tradeoffs for Future Military Space Access Vehicles

Future military space access vehicles may include Two-Stage-To-Orbit (TSTO) launch vehicles consisting of a reusable booster stage coupled with reusable or expendable upperstages. The characteristics of such potentially responsive space launch architectures have to be matched with envisioned scenarios of future conflict that will drive program launch rates. There are publicly available assessments of notional military space plane sortie requirements. There are also notional concepts of the turnaround times and fleet sizes that may be viable for a new space launch program. Thus a fundamental question arises about the tactical usefulness of such a program, namely: can a given fleet of military space planes with a given turnaround time, meet the required number of sorties (capture rate) for various envisioned future demand scenarios, or more generally, what are requirements that enable responsiveness? A mission capture assessment was performed to determine how these launch architectures meet various operational requirements for future peace and wartime scenarios. The important parameter being examined here is mission capture rate or the percentage of required sorties flown. This is rate/metric dependent upon the turnaround time (between when a vehicle lands and then next takes off) of an individual vehicle and the number of available vehicles in the fleet. The sortie capture rate is directly proportional to fleet size and inversely proportional to turnaround time. The assessment process included the creation of a flight capture model in MS Excel and in the ModelCenter© collaborative design environment for probabilistic simulation of future demand. This analysis has shown that there are aggressive turnaround time requirements (under half-a day) for a potential responsive space launch fleet if it wants to meet a large percentage of required sorties. The output probability distribution of total program sorties has a very large spread. Subsequently, surge requirements will be an important driver to help lower overall Life Cycle Cost by optimizing fleet size and turnaround time.