An expendable launch system is a launch system that uses an expendable launch vehicle (ELV) to carry a payload into space. The vehicles used in expendable launch systems are designed to be used only once (i.e. they are "expended" during a single flight), and their components are not recovered for re-use after launch. The vehicle typically consists of several rocket stages, discarded one by one as the vehicle gains altitude and speed.
The ELV design differs from that of reusable launch systems, where the vehicle is launched and recovered more than once. Reuse might seem to make systems like the Space Shuttle more cost effective than ELVs, but in practice launches using ELVs have been less expensive than Shuttle launches. (See Space Shuttle Program and Criticism of the Space Shuttle program for discussion of Space Shuttle economics). Most satellites are currently launched using expendable launchers; they are perceived as having a low risk of mission failure, a short time to launch and a relatively low cost.
Many orbital expendable launchers are derivatives of 1950s-era ballistic missiles. Many see this as unfortunate because cost was not a major consideration in their design. A prime example of this is the Titan IV, probably the costliest per-unit launch vehicle in history (perhaps following the Space Shuttle).
On the other hand, a reusable launcher such as the Shuttle requires a heavier structure and a recovery system (wings, thermal protection system, wheels, etc) that reduce payload capacity. The Shuttle additionally carries a crew (though not inherent to a reusable system) whose weight, supplies and life support systems further decrease payload capacity.
A Shuttle orbiter is a major national asset, and its high cost (far more than a single expendable launch vehicle) and presence of a crew require stringent "man rated" flight safety precautions that increase launch and payload costs. Only five orbiters were built, and the unexpected loss of two (Challenger and Columbia) significantly impacted the capacity and viability of the Shuttle program. Each loss also resulted in an extended hiatus in Shuttle flights compared to that following most expendable launch failures, each of which impacted only that model of launcher.
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