Following the recent tragic loss of the Columbia, I understand that NASA has been considering the possibility that the undercarriage door on the left wing may have opened during re-entry.

Whatever the cause of the accident, having doors in a critical item like a heatshield can't be a good idea. A heatshield with doors must be more vulnerable than one without. There is no law that says a spacecraft must re-enter the atmosphere in an upright attitude.

The answer would be to design a vehicle which has an unbroken heatshield over its top face while all the hatches (undercarriage doors, cargo, crew etc) and windows are on the underside. The vehicle re-enters the atmosphere in the inverted attitude so the heatshield protects the vehicle. Once the vehicle has slowed to a speed where heating is no longer a problem it rolls to the upright position, lowers its undercarriage and lands in the usual way.

Denis Sharp Arundel, UK

Source: Flight International