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The last remaining debate was over the nature of the boosters. NASA had been looking at no less than four solutions to this problem, one a development of the existing Saturn lower stage, another using "dumb" pressure-fed liquid fuel engines of a new design, and finally either a large single solid rocket, or two (or more) smaller ones. The decision was eventually made on the smaller solids due to their lower development costs (a decision that had been echoed throughout the whole Shuttle program). While the liquid fueled systems provided better performace and enhanced safety, delivery capability to orbit is much more a function of the upper-stage performance and weight than the lower. The money was simply better spent elsewhere.

However reality was to interject and NASA found themselves with a rapidly plunging budget. Rather than stepping back and looking at their future as a whole given their new financial situation, they attempted to save as many of the individual projects as possible. The mission to Mars was quickly eliminated, but the Space Station and Shuttle continued on. Eventually only one of them could be saved, so it stood to reason that a low-cost Shuttle system would be the better bet, because without it a large station would never be affordable.

X-Prize
two weeks. This must be essentially the same vehicle: propellant can be replaced, but most of the rest of the vehicle must be reused. Even NASA's space shuttle falls short of this performance requirement, since it takes much more than two weeks to ready a given shuttle between flights. This prize foundation was created to encourage the development of private space travel, which is why government-funded projects are not allowed. The X Prize is designed to help create a space industry, and is modeled after many prizes from the early 20th century that helped prod the development of air flight—notably the $25,000 Orteig Prize that spurred Charles Lindbergh to make his solo flight across the Atlantic Ocean. The X-Prize Foundation (based in St. Louis, Missouri) maintains a list of organizations registered

Space Shuttle Discovery
Space Shuttle Discovery Shuttle Orbiter Discovery (NASA Designation: OV-103) is a NASA Space Shuttle. First flown on August 30, 1984, Discovery is the third operational shuttle (excluding test shuttle 'Enterprise'). The orbiter is still operational today, and has performed both research and International Space Station (ISS) assembly missions. The craft takes its name from a ship used by explorer James Cook. Table of contents showTocToggle("show","hide") 1 Flights 1..1 Related articles 1..2

Meanwhile the Air Force had a continuing interest in smaller systems with more rapid turn-around times, and were involved in their own spaceplane project called Dynasoar. In several instances groups from both worked together to investigate the state of the art.

Instead they looked to reduce the year-to-year costs of development to a stable figure. That is, they wished to see the development budgets spread out over several more years. This is somewhat difficult to do--you can't build half a rocket. The result was another intense series of redesigns in which the re-usable booster was eventually abandoned as impossible to pay for. Instead a series of simpler rockets would launch the system, and then drop away for recovery. Another change was that the fuel for the shuttle itself was placed in an external tank instead of internal tanks from the previous designs. This allowed a larger payload bay in an otherwise much smaller craft, although it also meant throwing away the tankage after each launch.