Early on in the development stage for the Space Shuttle, NASA had investigated the possibility of building a fully reusable vehicle [4]. Their idea was to simply build a larger vehicle with all gas tanks and boosters inside the vehicle. As shown in Figure 1 below, the original concept was for a vehicle that was 202 feet long, and was fully reusable, with only a single stage. Later on, the designers decided to scale the vehicle down to 123 feet long, with the liquid hydrogen gas tanks externally attached. Finally, due to compromises with Congress and the then-current technology limitation, the Shuttle designers settled on a plan for a 110-foot long Shuttle, with both liquid hydrogen and liquid oxygen fuel tanks carried externally.
After the Shuttle was designed and built, NASA began investigating a possibility for an RLV called the X-33. The X-33 was a subscale technology demonstrator, meaning it was scaled-down version a full size vehicle, and was built to prove that the full-size vehicle could be built. The full-scale version was dubbed the VentureStar. The X-33 was designed with a vertical takeoff, horizontal landing configuration, similar to the Space Shuttle. NASA ended up budgeting $941 million for the project, and although the scientists and engineers did conduct drop tests of the model, no powered prototype ever flew.
Another noteworthy attempt at producing an RLV is the outcome of the current NASA project: the Space Launch Initiative (SLI), whose purpose is to eventually turn out a replacement for the Space Shuttle. One of the spacecraft being researched for the SLI is the X-37. The X-37 is a technology demonstrator, designed to validate concepts and designs that could be used in the future for an Orbital Space Plane (OSP). However, NASA doesn’t intend for the OSP to be fully reusable. The X-37 is only intended to be a stopgap measure while more time and money is spent studying a true RLV. This is shown by the fact that, so far, NASA has only conducted drop tests and structural tests on the X-37.
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Another noteworthy attempt at producing an RLV is the outcome of the current NASA project: the Space Launch Initiative (SLI), whose purpose is to eventually turn out a replacement for the Space Shuttle. One of the spacecraft being researched for the SLI is the X-37. The X-37 is a technology demonstrator, designed to validate concepts and designs that could be used in the future for an Orbital Space Plane (OSP). However, NASA doesn’t intend for the OSP to be fully reusable. The X-37 is only intended to be a stopgap measure while more time and money is spent studying a true RLV. This is shown by the fact that, so far, NASA has only conducted drop tests and structural tests on the X-37.