February 1983:the Manned Escape System

The frequent use of the Space Shuttle raises the possibility of astronauts being stranded in orbit should something go wrong with their craft. Present rescue plans involve a second Shuttle Orbiter flying to recover the stricken astronauts - a lengthy process if another Orbiter is not immediately available. An alternative is to return the crew using reentry capsules based on proven satellite designs up to 20 years old.

Introduction

A Manned Escape System (MES) could be a scaled-up satellite reentry vehicle with provisions for a human payload and autonomous deorbit capability. Accommodations for humans would include attitude control for retrofire and impact attenuation during landing. Life support would be provided by pressure suits and not by the capsule itself.

The capsule would be equipped with contour couches, an ingress hatch, power supply and communications equipment. Up to four crew members could be seated around a central console. This arrangement permits compact seating without the need to fold back equipment for ingress and it allows semi-prone positioning for good acceleration tolerance.

An ablative heat shield would be attached to the conical portion of the reentry vehicle’s forebody. The basic structure of the vehicle would be two nested semi-monocoque aluminium shells of conventional fabrication connected through an aft bulkhead.

The attitude control system would not be dependent on the crew since they might be incapacitated or unqualified to fly the craft. Thus a fully automated three axis attitude control system using infrared horizon sensors and rate gyros would be provided. It would automatically stabilize and position the vehicle for retro fire.

Retro fire could be controlled by the crew or from a ground station when the tracking network was in the best position to determine the proper timing for touchdown. A deorbit module would contain all the attitude sensing components, the retro rocket, tankage, plumbing and other items associated with the fuel and oxidizer supply. A retardation system would consist of single or multiple parachutes with associated drogue, reefing and deployment devices. The shock of a land recovery would be reduced by an inflated bumper deployed just before touchdown. An Advanced Vehicle Recovery system with a gliding parachute could make corrections to the flight path of 25 miles or more in calm air or moderate the effect of prevailing wind conditions. It would also allow the crew to avoid obstacles.

MES Operation Modes

The basic Manned Escape System could be used in a variety of.ways. In the “Ground Standby/Launch on Demand” method the MES could be a ground-based unit mounted on its own booster, the Titan IIIB, along with an orbital rendezvous package. It would be maintained .on continuous standby for prompt launch when required. The upper stage/MES would manoeuvre to and rendezvous with the crippled craft. This mode could replace the present Space Shuttle rescue method in which another Shuttle is used as the rescue craft.

The major drawback of the "Launch on Demand” system is that even under the best conditions there would be an appreciable delay before the arrival of the rescue package to help the astronauts. This could be overcome by maintaining rescue packages in selected parking orbits. They would consist of a basic escape vehicle/s mounted on a bus module to provide limited orbital transfer, rendezvous, manoeuvre and docking capability, plus pointing for retrfire. Again, there is a drawback with this method. The rescue module could be considerably displaced along the orbital track, although at the same basic inclination as the stricken vehicle. An appreciable time lag could therefore occur before rendezvous.

The ‘life boat” method of operating the rescue package offers the most readily available system at an economical cost. In this mode the escape system is integrally mounted on the manned system, such as the Orbiter or a Space Operations Center, from the outset. A four-man escape system could be installed in the Shuttle Orbiter with direct access by way of the airlock and egress tunnel. The actual mounting interface between the escapre package and the Space Operations Center is envisaged as similar to a docking prort with the capability for repeated separation and reattachment of replacement escapre vehicles. The reentering escape package would remain within ± 50 miles along the ground track and ± 10 miles cross range. This allows for selective choice of landing sites with a degree of freedom limited only by the time in orbit before retro fire.