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An alternative idea to the Beanstalk/Space Elevator, and similar to a Loftstrom Loop, as a method of launching - and keeping - objects into space. It was used in the book Starquake, and by Frederick Pohl in the book Mars Plus.

It's been long discussed that for humans to make a significant amount of use of space, that a more cost-effective method of transporting people and objects into orbit and beyond will be needed. Rockets and shuttles are expensive, clumsy, high in usage of resources, and not all that reliable.

With a space fountain, the idea is to build a space station on the ground. Underneath it is a type of launcher, one that will launch projectiles (such as little blocks of iron) directly upward at high speeds - high enough to reach orbit. The bottom of the station will have a mechanism on the underside which will take in the projectiles, and using magnets, redirect and launch the projectiles back toward the ground. The momentum of the projectile going up, and the action of shooting it back down, will both add upward momentum to the station. To avoid problems with air resistance, an evacuated tube would be constructed as the station rose, and magnets inside the tube sections would create electromagnetic drag, converting the momentum into energy.

Obviously, a LOT of projectiles, fired at very high speeds, and very rapidly would be needed to launch a space station with this method. Extreme accuracy would also be necessary - a slight deviation in the upward launch would cause the projectiles to miss the recepticle, and cause severe damage to the station, along with costing it momentum. Inaccuracy in the downward redirection would be dangerous for those on the ground, might cause collisions with upward moving particles, and would deplete the number of particles available to launch. Redundancy would also be important, as a failure that caused the station to fall downward would not be a good thing.

Calculations have been done to suggest that once the station is in place, only a very small amount of energy would be needed to keep the station aloft - as energy used to launch the projectiles would be largely reclaimed by the gaining of energy through gravity on the return trip. However, the initial energy requirements to get all the particles moving, and to put the station into space, would be tremendous.

Also, this technique could be easily adjusted to allow special "cars" that held cargo or people to be sent up or brough down from the station, as the projectile streams are already in place.

Interestingly, there appears to be at least one design concept for a space fountain that could be created with technology available today. And that the cost of getting something into orbit with the fountain would be about $2 per kg - as compared to today's cost, which is about $5000 per kg. Quite a difference. A model has even been developed by Roderick Hyde, at the Lawrence Livermore National Laboratory.

The ideas of the launch loop and orbital ring have both grown out of this concept.

Distant Star, www.distant-star.com/issue7/may_98_reviews.htm
Space Tethers, http://www.vectorsite.net/tatether.html
Interplanetary Travel: An Intro, http://www.geocities.com/Area51/Chamber/2838/space.html