Launch strategy for manned spacecraft: Improving safety or increasing of launch mass?

Traditionally the launch mass of a crew vehicle with a launch abort system (LAS) should be in compliance with the ultimate launch vehicle (LV) payload mass capability. The LAS is used to provide crew safety in the case of LV failure. An additional propellant for the LV (that exceeds the mass of propellant required for the injection into a nominal orbit) may contribute to crew safety in the case of LV failures. Currently rescue strategies used to provide emergency landing or splashdown along the ground track (for a spacecraft with a low lift-to-drag ratio (L/D), such as the Soyuz descent capsule) or landing on a back-up runway located near the flight path (for spacecraft with a high L/D, such as the Buran or Space Shuttle Orbiter). The advanced Russian human spacecraft with a low L/D that delivers crew to the International Space Station is designed to launch from the new Vostochny launch site. Major part of the LV ground track will pass over the Pacific Ocean. It means that any rescue operation will be challenging and complex. The paper explores possible launch abort strategies when an additional LV propellant is used. The optimal strategy is to provide a controlled abort landing into specified areas. The number and size of the areas should be minimal in order to minimize search-and-rescue time. A qualitative comparison between the traditional and proposed strategies is shortly discussed.

► Additional propellant may be increased crew safety for accident launch vehicle.
► Limiting load factor trajectories and maneuvers can be used for launch abort system.
► Emergency trajectory for low-altitude failure is guidance to specified landing point.
► Emergency trajectory for high-altitude failure is one-revolution flight with landing.