To and From Orbit

The Pournelle, like all deep space craft, cannot land or take of from a planet. Built in space, she is serviced by two dedicated heavy lifter spaceplanes stored in hangerage forward of the cargo bay. Each lander has a payload capacity of 20 metric tons in a single, central bay .

The landers are powered by a conventional VASIMR drive and are equipped with MIGMA reactors capable of sustaining operations for several years. However, in order to provide the thrust necessary to gain orbit, the landers must be supplied with additional propellant (such as water or H2) after each planet to orbit flight.

In operation, the landers function as lifting body aircraft. Descent is by ballistic reentry followed by power assisted glide. The lander carries enough propellant for significant maneuvering and wave-off and return to orbit if necessary. By far the most fuel consumptive part of any mission is the return to orbit. After climbing to high altitude like a conventional aircraft, the power plant is then placed in high thrust mode and the craft is nudged into high orbit. If the lander fails to achieve stable orbit, it does not have enough propellant for a second attempt and must land and be refueled.

The craft may land in one of three mode. Powered, unpowered and emergency. In a powered landings, any reasonably flat and level surface at least 1000 meters long is acceptable. The craft effects landing like a conventional aircraft, and employs thrusters and a landing flare to shorten the landing field requirements.

A low energy glide can be effected if a landing space with sufficient space is available. At least 5 kilometers is recommended, although three is the minimum specification. A low energy landing will allow for a significant fuel saving, giving about a 20% reserve for the return trip to orbit.

In a catastrophic accident, the craft may be landed using steep descent and two parachutes. This type of landing can damage the vehicle and is for emergencies only.

Mission profiles for the lander can be altered by taking advantage of the modular nature of the cargo bay. For example, should the mission require low level survey flights, additional fuel can be carried in the cargo bay to allow for longer cruising time over the target. Each lander is capable of supersonic flight at all altitudes, and can cruise under low power down to 300 kph before losing lift. Slower speed cam be maintained by using the vectoring nozzles on the main engine.