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The Space Shuttle program is an ongoing
endeavour, started in the late 1960s, that has created the world's
first partially reusable space launch system, and the first
spacecraft capable of carrying large satellites both to and from
low Earth orbit. Each shuttle is designed for a projected lifespan
of 100 launches. The original purpose of the program was to ferry
supplies to a space station. In reality, the Shuttle is the United
States' sole manned launch vehicle and has totally dominated
NASA's operations since the mid 1970s. With the construction of
the International Space Station the Shuttle has finally begun to
be used for its original purpose. In January 2004, it was
announced that the Shuttle fleet would be replaced by 2010.
The idea for the shuttle began around the 1960s as the Apollo
development was winding down. NASA had wanted to develop reusable
spacecraft to replace their costly "one-off" systems like Mercury,
Gemini, and Apollo. Meanwhile the Air Force had a continuing
interest in smaller systems with more rapid turn-around times, and
were involved in their own space plane project called Dynasoar.
NASA had plans for a program consisting of a large space station
being launched on huge boosters, served by a reusable logistics
"space shuttle", both providing services for a permanently manned
Lunar colony and eventual manned missions to Mars.
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, so too was the Space
Station plan rather reluctantly. They continued with the low-cost
Shuttle plan as without it a large station would never be
affordable in the future.
A number of designs were proposed, but many of them were complex
and varied widely in their systems. An attempt to re-simplify was
made in the form of the "DC-3". The DC-3 was a small craft with a
20,000lbs (or less) payload and a four-man crew. it was simple in
design and cheap to operate. looking back this design may have
served NASA better than what they ended up with.
With NASA's funding being cut more and more the only way they
could go further was to join their project with the Air Forces
need to launch Spy Satellites, something the Air Force was doing
on Titan rockets.
The Air Force agreed to pitch in for the shuttle as it made sense
on paper to share the cost of the project, but the Air Force had
different needs to NASA so they demanded a large increase in
capability to allow for launching their spy satellites into polar
orbits, which requires more energy to get to than the more common
low Earth orbit.
The result was that the simple DC-3 was clearly out of the picture
because it had neither the cargo capacity nor the cross-range the
Air Force demanded. In fact all existing designs were far too
small, as a 40,000 lbs delivery to polar orbit equates to a 65,000
lbs delivery to a "normal" 28 degree equatorial orbit. In fact any
design using simple straight or fold-out wings was not going to
meet the cross range requirements, so any future design would
require a more complex, heavier delta wing.
Worse, any increase in the weight of the upper portion of a launch
vehicle, which had just occurred, requires an even bigger increase
in the capability of the lower stage used to launch it. Suddenly
the two-stage system grew in size to something larger than the
Saturn V, and the complexity and costs to develop it skyrocketed.
With the budgets being pressed by inflation at home and the
Vietnam War abroad, Congress and the Administration generally
couldn't care less about anything as long-term as space
exploration and were therefore looking to make further deep cuts
to NASA's budget. But with a single long term project on the
books, there wasn't much they could do in terms of cutting whole
projects -- the shuttle was all that was left, cut that and there
would be no US manned space program by 1980.
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.
The shuttle program was launched on January 5, 1972 and the
prototype shuttle "the enterprise" was complete by 1976 and only
used for testing. The first fully functional shuttle orbited was
the Columbia, which was delivered to Kennedy Space Centre on March
25, 1979 and was first launched on April 12, 1981 with a crew of
two. Challenger was delivered to KSC in July 1982, Discovery was
delivered in November 1983, and Atlantis was delivered in April
1985. Challenger was destroyed in an explosion during launch in
January 1986 with the loss of all seven astronauts on board, and
Endeavour was built as a replacement (using spare parts originally
built for the other orbiters) and delivered in May 1991. Columbia
was lost, with all seven crew, in a re-entry mishap on February 1,
2003.
Whilst the shuttle has been a reasonably successful launch
vehicle, it had been unable to meet its goals of radically
reducing flight launch costs, as each flight costs on the order of
$500 million rather than initial projections of $10 to $20
million. continual design improvements and testing has 25000
people working on the shuttle program, the idea behind a reusable
craft was to get the shuttle working on a two week turn around, in
reality this can take months. The Reason for designing the Shuttle
the way it is was to get the Air Force involved, by the time the
project had got too far the Air Force gave up on the shuttle and
returned to using titan rockets. Today NASA are looking to
supplement the Shuttle with an Orbital Space Plane project to
become a ferry to and from the ISS, this OSP will be a simpler
design perhaps not far different to what NASA wanted in the first
place.
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