Launch Ramp

Inclined launch ramp supported by large scale structures on a planetary surface

Image from Steve Bowers
This launch ramp is supported by a artificial mountain 30km high, largely constructed from graphene-lined cells inflated with buoyant gas. Spacecraft are accelerated up a hollow tube by magnetic levitation. When the craft reach the end of the ramp they use rocket motors to accelerate to orbital speed.

Launch ramps use maglev tracks or similar powered accelerators to accelerate spaceraft to high speed before leaving the planet; this cuts down on the amount of fuel required to attain orbit. One design uses an evacuated tube, inclined from ground level to high elevation; the spacecraft is accelerated within the tube until reaching the upper atmosphere. Note that the tube must be actively evacuated or pressure inside and outside will equalise.

The ramp is often tens of kilometres high, with a relatively gentle slope, and may be many hundreds of kilometres long. The diamondoid support structure may be augmented by inflatable cells for support, using a buoyant gas such as helium, or simply using warm air; on some worlds the launch ramp may be supported by a stack of tethered fullair balloons. Alternately the ramp may be dynamically supported by space fountain technology.

Launch ramps are large structures, larger than most cities. Many launch ramps double as arcologies or support various other forms of habitable infrastructure. Some contain industrial manufacturing facilities (including spacecraft construction yards) or environmental homeostasis systems. On worlds with non-Earthlike atmospheres, launch ramps may be constructed on the outside surfaces of domed habitats, using the structure of the dome for support.

A related concept is the Lofstrom Loop, a structure which requires much less mass as it is entirely self-levitating.
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Development Notes
Text by Steve Bowers
Initially published on 27 February 2012.