friction) can be different and Bolonkin claims that they could wedge in the tube; and the force and friction in the ground 28 km diameter turnaround sections are gigantic. In 2008, Bolonkin proposed a simple rotated close-loop cable to launch the space apparatus in a way suitable for current technology. Another project, the space cable, is a smaller design by John Knapman that is intended for launch assist for conventional rockets and suborbital tourism. The space cable design uses discrete bolts rather than a continuous rotor, as with the launch loop architecture. John Knapman has also mathematically shown that the meander instability can be tamed. The skyhook is another launch system concept. Skyhook could be either rotating or non-rotating. The non-rotating skyhook hangs from a low Earth orbit down to just above the Earth's atmosphere (skyhook cable is not attached to Earth). The rotating skyhook changes this design to decrease the speed of the lower end; the entire cable rotates around its center of gravity. The advantage of this is an even greater velocity reduction for the launch vehicle flying to the bottom end of the rotating skyhook which makes for an even larger payload and a lower launch cost. The two disadvantages of this are: the greatly reduced time available for the arriving launch vehicle to hook up at the lower end of the rotating skyhook (approximately 3 to 5 seconds), and the lack of choice regarding the destination orbit. See also Belt (mechanical) Cable transport Magnetic levitation Mass driver Megascale engineering Non-rocket spacelaunch Orbital ring Space elevator Space gun Space fountain Space tourism StarTram Tether propulsion References External links www.launchloop.com SpaceCable Another similar idea for launch assist/short range travel/recreational extremely high altitude trips Space Elevator Stage 1: Through the Stratosphere, John Knapman, Keith Lofstrom, presentation at Microsoft conference center, August 2011. Magnetic levitation Megastructures Spacecraft propulsion Magnetic propulsion devices Hypothetical technology Vertical transport devices Loop Space elevator