Optimization of ETO Launch Systems for Airplane-like Safety and Reliability

Achieving airplane-like safety and reliability on ETO launch systems requires fundamental changes in vehicle propulsion and flight trajectories. Current launch systems all have extended regions where catastrophic engine failure means loss-of-vehicle (LOV) either through loss of control or insufficient thrust to weight (T/W < 1.0). These regions have been euphemistically termed “dead zones” for obvious reasons. The most straightforward solution is to supply extra engines to give “engine-out capability”, but this approach has limited use because of the additional cost and weight penalties, and the fact that uncontained engine failures will often result in “engine fratricide”, which can still reduce T/W < 1. In this paper we examine causes of unreliability, available intact abort options, and a variety of approaches for enhancing the safety of different reusable launch systems. We are focusing on reusable launch systems because reuse has historically resulted in one to two orders of magnitude reduction in vehicle loss rate (after a reasonable flight test program).