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Skylon Spaceplane Design Passes Key Review
gbjbaanb writes "A revolutionary UK spaceplane concept has been boosted by the conclusions of an important technical review. Skylon is a design for a spaceplane that uses engines that work as normal jets near the ground and switch to rocket propulsion in the upper atmosphere. The concept means the plane will not have to carry as much fuel and so will not need disposable stages. It is estimated (by its developers) that the Skylon will drop the cost of delivering payloads to orbit from $15,000 per kilo to $1000."
From what I learned in physics class, the cheapest way to get through the thick atmosphere is to go straight up.
That's only true for conventional rockets. The longer you remain in the lower atmosphere, you more rocket fuel you must carry. The more fuel you must carry, the larger the rocket you require. The larger the rocket you require, the larger the engine. The larger the engine, the more fuel you must carry. This is a nasty spiral simply because you obtain 100% of your lift from thrust.
With the skylon design, you are obtain a lot of your lift - from lift. Its only after you're passed through the lower atmosphere, where you don't get much lift and where you now need an oxydizer for your fuel, that you need to start a rocket engine. Thusly, they've side step a massive problem with traditional rockets.
Furthermore, its the first stage on traditional rockets which requires the most fuel to obtain orbital velocities. By using a plane's features, a massive weight burden (and associated size) is removed from the design.