Expendable_launch_system

Expendable launch system

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 after launch. The vehicles typically consists of several rocket stages, discarded one by one as the vehicle gains altitude and speed.

Design rationale

The ELV design differs from that of a reusable launch system, where the vehicle would be launched and recovered more than once. This might seem to make the ELV design a more expensive launch method, but in practice launches using ELVs have been less expensive than launches on the Space Shuttle, which is the only existing launch vehicle that is even partly reusable. (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.

There have also been proposals for single stage to orbit systems. Single stage to orbit vehicles would theoretically be less costly to develop and operate than comparable multistage launchers, but would not be able to launch as much payload per unit of gross liftoff weight due to the mass fraction advantages of multistage rockets.

History

Most orbital expendable launchers are derivatives of 1950s-era ballistic missiles. The Magellan probe was the first planetary spacecraft launched by a Space Shuttle.

Many see it as unfortunate that most "modern" orbital expendables are derived from ballistic missiles, as these missiles were built to Cold War specs and with Cold War budgets, and argue that this makes for horrendously expensive launch vehicles. 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, reusable launchers have to be built more robustly and thus carry extra dry weight to orbit, and require recovery systems, and thus everything else being equal (to a similarly constructed expendable), would have a very much smaller payload. Reusable launchers would thus not necessarily be enormously cheaper.

Development

European sponsorship

On March 26, 1980, the European Space Agency and the Centre National d'Etudes Spatiales (CNES) created Arianespace, the world's first commercial space transportation company. Arianespace produces, operates and markets the Ariane launcher family. By 1995 Arianespace lofted its 100th satellite and by 1997 the Ariane rocket had its 100th launch. Arianespace's 23 shareholders represent scientific, technical, financial and political entities from 10 different European countries. The major shareolder is the CNES, with 32,53% of capital.

American deregulation

From the beginning of the Shuttle program until the Challenger disaster in 1986, it was the policy of the United States that NASA be the public-sector provider of U.S. launch capacity to the world market. Initially NASA subsidized satellite launches with the intention of eventually pricing Shuttle service for the commercial market at long-run marginal cost.

On October 30, 1984, United States President Ronald Reagan signed into law the Commercial Space Launch Act. This enabled an American industry of private operators of expendable launch systems. Prior to the signing of this law, all commercial satellite launches in the United States were limited to NASA's Space Shuttle.

On November 5, 1990, United States President George H. W. Bush signed into law the Launch Services Purchase Act. The Act, in a complete reversal of the earlier Space Shuttle monopoly, ordered NASA to purchase launch services for its primary payloads from commercial providers whenever such services are required in the course of its activities.

Russian privatization

The Russian government sold part of its stake in RSC Energia to private investors in 1994. Energia together with Khrunichev constituted most of the Russian manned space program. In 1997, the Russian government sold off enough of its share to lose the majority position.

American subsidization

In 1996 the United States government selected Lockheed Martin and Boeing to each develop Evolved Expendable Launch Vehicles (EELV) to compete for launch contracts and provide assured access to space. The government's acquisition strategy relied on the strong commercial viability of both vehicles to lower unit costs. This anticipated market demand did not materialize, but both the Delta IV and Atlas V EELVs remain in active service.

Launch alliances

Since 1995 Khrunichev's Proton rocket is marketed through International Launch Services while the Soyuz rocket is marketed via Starsem. Energia builds the Soyuz rocket and owns part of the Sea Launch project which flies the Ukrainian Zenit rocket.

In 2003 Arianespace joined with Boeing Launch Services and Mitsubishi Heavy Industries to create the Launch Services Alliance. In 2005, continued weak commercial demand for EELV launches drove Lockheed Martin and Boeing to propose a joint venture called the United Launch Alliance to monopolize the United States government launch market.

Today many commercial space transportation companies offer launch services to satellite companies and government space organizations around the world. In 2005 there were 18 total commercial launches and 37 non-commercial launches. Russia flew 44% of commercial orbital launches, while Europe had 28% and the United States had 6%.

See also

External links

References

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