A Launch Loop is a metal loop in an evacuated tube that spins at high speed on magnetic bearings. As it speeds up one side of the loop is projected up to a high altitude. Vehicles are electromagnetically accelerated on top of the tube up to orbital speeds and can be launched into low earth orbit or beyond.

For safety and astrodynamic reasons, launch loops would be located in the ocean near the equator, well away from habitation.


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The launch loop is due to Keith Lofstrom. It is essentially a hybrid of the orbital ring concept and the space fountain. It is an oval ring around 2000 km long, on one side of the ring it has two base stations about 2000km apart on Earth which can launch and catch the moving loop to and from high altitude. Although the loop is very long, the loop and sheath is very thin, only around 5 cm diameter, and is cable-like.

The loop starts off at ground level, and is contained in an evacuated tube. The loop is spun up on magnetic bearings to 14 km/s. As the speed increases one half of the loop is arranged to push upwards into an approximate arch shape, until it reaches its operating altitude of around 60-80 kilometers where the loop is restrained and shaped by tensile cables.

To launch, vehicles are electromagnetically accelerated up the arch at around 3g acceleration, until they are above the atmosphere and at orbital velocity, and are then released, and a rocket engine is then employed to circularise the trajectory to an Earth orbit.PDF version of Lofstrom's 1985 launch loop publication (AIAA 1985)

the ISDC2002 slide show

Uses for launch loops

Uses for smaller-scale launch loops

Groups benefiting from building launch loops