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Space Shuttle Discovery



Space Shuttle Program Background
Written and Edited by Cliff Lethbridge


Born in 1968 at the height of the Apollo program, the Space Shuttle was designed to fulfill two basic roles in NASA post-Apollo manned flight objectives.

The first goal of the Space Shuttle program was to provide NASA with an efficient, re-usable method of carrying astronauts to and from a permanently manned space station.

At the time, NASA envisioned a space station which would be staffed by 12 to 24 people. The space station was intended to assure a permanent manned U.S. presence in space following the Apollo lunar landings.

The space station would support a plethora of scientific research objectives, plus act as an engineering and support base for manned journeys to the planets.

In addition, NASA believed that Space Shuttles could serve as multi-purpose satellite delivery vehicles with the potential to completely replace Atlas-Centaur, Delta and Titan rockets.

The words "cheap" and "routine" were the words which most closely matched the objectives for Space Shuttles as expressed by NASA. Of course, history would prove otherwise.

On January 31, 1969, NASA issued feasibility design study contracts for their "Integrated Launch and Re-entry Vehicle" (ILRV). Invitations were given to four aerospace contractors to present design proposals on re-usable and partially re-usable manned spacecraft.

These companies presented reports to NASA by November 1, 1969. They unanimously recommended a fully re-usable, two-stage vehicle.

Early in 1970, NASA refined their technical requirements for the vehicle. The name "Space Shuttle" first appeared in the "purpose" section of an official invitation for production contract bids issued on February 18, 1970.

The name "Space Shuttle" subsequently became a permanent fixture for the vehicle, which NASA agreed should incorporate a fully re-usable, two-stage design.

With great optimism, NASA initially expected that the first Space Shuttle would enter service by 1977. In 1971, North American Rockwell and McDonnell Douglas were granted production contracts.

From that point on, development of the Space Shuttle became extremely complicated, with the future of the vehicle often in doubt from one year to the next.

At first, doubts surfaced about the feasibility of developing a two-stage Space Shuttle. To analyze these concerns, NASA issued study contracts to Grumman/Boeing, Lockheed and Chrysler in June, 1971.

In basic terms, the initial NASA concept for the two-stage Space Shuttle called for a smaller manned winged vehicle to sit atop a larger manned winged vehicle. These would be pad-launched from a vertical position.

The larger winged vehicle would be called the "Booster", while the smaller winged vehicle would be called the "Orbiter". The Booster would carry the Orbiter to an altitude of about 50 miles. The Orbiter would then separate and fire its own engines to reach orbit.

After separation, the Booster would turn and descend through the atmosphere for a landing near the launch site. The Orbiter would return for a landing upon the conclusion of its space mission.

The Booster would, in essence, be a fuel tank with wings. In this two-stage concept, both the Booster and Orbiter would require cockpits, hardware and instrumentation to facilitate landings.

Both were designed to carry internal turbo-fan engines which would produce controlled flight during landing operations. Each vehicle would carry its own fuel tanks.

As originally described by NASA in 1970, this two-stage Space Shuttle would be able to carry a 25,000-pound payload to a maximum 300-mile circular orbit.

As we now know, this early two-stage concept obviously does not resemble the Space Shuttles which were eventually built. This was due to the economic realities facing NASA in the early 1970's.

In a time of general recession, it was clear that NASA could not afford to build a fleet of complicated two-stage Space Shuttles along with a space station at the same time. Utilizing the intent of the day for the Space Shuttle, one without the other made no sense at all.

Matters were further complicated in 1971 as NASA negotiated with the U.S. Air Force regarding shared use of the Space Shuttle fleet. Military funding for the Space Shuttle program was vital if NASA hoped to build the vehicle at all.

But the U.S. Air Force specified a total payload capability of 65,000 pounds for Space Shuttles capable of carrying large, sophisticated military satellites into orbit. This figure was nearly three times more than NASA had originally planned.

These major factors led to a dramatic redesign of the Space Shuttle and the proposed space station.

The NASA space station was originally designed following the Skylab pattern. A single multi-deck structure which made up the space station would be carried into orbit by a Saturn V rocket. Space Shuttles would then only be needed to ferry astronauts, equipment and supplies.

It was thought that this type of space station would have a useful life of about ten years, at which time it could simply be replaced by another. However, an "all at once" space station did not fit the NASA budget.

NASA decided to adopt a modular concept for the space station. The space station would be built piece by piece over a period of years, with separate modules carried into orbit by Space Shuttles.

This was a prudent move for NASA. Not only did it provide a more realistic approach for constructing a space station, it also made possible the production of a redesigned Space Shuttle capable of carrying heavy military payloads and even commercial satellites.

In redesigning the Space Shuttle as a space station module carrier, U.S. Air Force payload criteria were met, thus assuring critical military funding. Just as important, the redesign would allow NASA to carry a plethora of satellites aboard Space Shuttles.

Over time, this could produce tremendous cost savings for NASA. Not only could NASA secure private funding to carry commercial satellites aboard Space Shuttles, the costs of maintaining Atlas-Centaur, Delta and Titan rocket fleets could be phased out and ultimately eliminated.

With an event like the Challenger explosion never anticipated, NASA made a decision, so to speak, to "put all of their eggs in one basket". The Space Shuttle was to be a multi-purpose manned vehicle which would carry NASA into the next century.

Even with major design modifications, NASA faced a huge price tag for its Space Shuttle fleet. On July 1, 1971, NASA granted four-month contract extensions to Rockwell and McDonnell Douglas to come up with methods of cutting their projected $10 billion development costs.

The contractors decided that the most suitable method of cutting costs was to scrap the manned Booster stage of the Space Shuttle. NASA opted instead to create a more traditional expendable system to carry the manned Orbiter into space.

NASA kept the manned Booster on the drawing boards, though, in case it could be afforded at a later date. Reduction in the overall size and complexity of the Space Shuttle booster system and redesign of the Orbiter did provide cost savings, but additional changes were ahead.

A smaller version of the Orbiter, called Mark I, was planned initially. This could later be replaced by a larger Mark II version of the Orbiter. The development of the Mark I and Mark II Space Shuttle fleet was to be phased in over a period of several years.

The Orbiter itself could be scaled down considerably as NASA agreed to use external fuel tanks to carry the fuel the spacecraft would need to reach orbit. In previous designs, the Orbiter would carry its own fuel tanks on board.

In September, 1971, Boeing proposed using a modified S-IC first stage from the Saturn V to act as a main fuel tank for the Space Shuttle. In one version, the S-IC could be equipped with a crew compartment, wings and aerodynamic equipment to facilitate a manned Booster landing.

The "Re-usable S-IC" Booster, called RS-IC, would carry the Orbiter aloft. Following separation, the Orbiter would reach orbit powered by its own engines, fed by two external liquid hydrogen tanks which would be jettisoned in space. The RS-IC would then return for a landing.

A more cost-effective version involved using a modified S-IC Saturn V first stage as an unmanned Booster which would be attached to a large external fuel tank. This array would be mated to the Orbiter.

The S-IC would then act as an expendable Booster which would separate at an altitude of about 45 miles, leaving the Orbiter to reach orbit using its own engines fueled by the remaining single external fuel tank which would be jettisoned in space.

With the exception of the S-IC booster, this design was somewhat similar to the vehicles which eventually flew. The S-IC option was scrapped because the booster burned liquid oxygen and kerosene. This fuel combination was deemed too inefficient for the Space Shuttle.

Space Shuttle development contracts for Rockwell, Grumman/Boeing and Lockheed were extended through February, 1972, and two core concepts for the spacecraft emerged. These were divided into parallel burn and series burn concepts.

In the parallel burn concept, the Orbiter's engines ignited at the same time as the Booster. The Orbiter's engines would fire all the way to orbit, which would require them to be fed by a large external fuel tank.

The Booster system would be jettisoned at some point during ascent. Initial options for the Booster called for various combinations of large or medium-sized solid rocket boosters with the possibility of high-pressure liquid fuel assist.

One popular parallel burn Booster combination called for two large solid rocket boosters to be assisted by four smaller solid rocket boosters which would be strapped to the Orbiter's large external fuel tank.

In the series burn concept, or multi-stage approach, the Orbiter's engines would still be fed by an external fuel tank. However, the Orbiter's engines would not fire until a first stage Booster had first been expended in flight.

Series burn first stage arrays on the drawing board for the Space Shuttle called for various combinations of clustered solid rocket boosters, clustered modified Saturn V F-1 engines or new high-pressure liquid fueled engines.

NASA again encountered development difficulties because all of the parallel and series burn concepts presented proved to be too expensive to be manufactured under tight budgetary constraints.

A company named Mathematica was retained by NASA to perform an economic analysis of the entire Space Shuttle program. The company would recommend the most cost-effective design for the vehicle, as well as tally funding alternatives such as commercial launch revenue.

Mathematica did provide some encouragement at a critical time for NASA. It was almost immediately determined that the U.S. manned space program would be more cost-effectively served by Space Shuttles rather than continued use of expendable rockets like Saturn IB and Saturn V.

The federal Office of Management and Budget (OMB) scrutinized NASA expenditures and the agency's proposals for the Space Shuttle. Initial reactions of OMB to the Space Shuttle were not encouraging, so NASA took its case directly to President Richard M. Nixon.

Late in 1971, there was a chance that the Space Shuttle program would be halted for more than one year. NASA had no guarantee that President Nixon would recommend any expenditures for the Space Shuttle in his fiscal year 1973 budget, which ran from July 1, 1972 to June 30, 1973.

President Nixon was ready to present his fiscal year 1973 budget to the U.S. Congress in early January, 1972. If he did not endorse funds for the Space Shuttle in this budget, the program could have faced a stall until July, 1973 at the earliest.

NASA Administrator James Fletcher and NASA Deputy Administrator George Low met with President Nixon for 45 minutes at the "San Clemente White House" on January 5, 1972. A decision had already been made based on previous correspondences between NASA and the President.

At 11:15 a.m. Pacific Time on January 5, 1972, President Nixon announced his commitment to fund the development of the Space Shuttle. Just 19 days later, his budget was presented to Congress. Necessary funding for the Space Shuttle was ultimately approved.

NASA still lacked a firm design for the Space Shuttle. Mathematica reported that two options remained economically feasible for the Booster stage. Either a large solid rocket booster system or a high-pressure liquid fueled Booster system were considered feasible.

A high-pressure liquid fueled series or parallel burn Booster was projected to cost $7 billion to develop and $100 per pound of payload to operate.

A parallel burn Booster utilizing large solid rocket boosters was projected to cost $5.5 billion to develop and $160 per pound of payload to operate.

While the Booster employing large solid rocket boosters would likely be more expensive to operate, NASA opted to take advantage of huge cost savings up front.

Since costs of ultimate operation could be absorbed throughout the life of the Space Shuttle program, the parallel burn Booster using large solid rocket boosters was selected.

On March 15, 1972, NASA officially announced plans to incorporate this design into the Space Shuttle. The solid rocket boosters were to be recovered and re-used following each launch. NASA claimed each solid rocket booster could be flown 100 to 500 times prior to retirement.

As per this parallel burn configuration, the Orbiter's engines would be ignited at launch and fed by liquid fuel contained in a large external fuel tank which would be jettisoned after the spacecraft neared orbit.

On March 17, 1972, NASA requested bids for construction of the Orbiter. Responses from Rockwell, Grumman, McDonnell Douglas and Lockheed were received by May 12, 1972.

Space Shuttle Main Engine (SSME) development remained the responsibility of Rocketdyne under a contract which had already been issued in July, 1971. NASA updated their SSME specifications and submitted them to Rocketdyne in April, 1972.

The International Space Division of Rockwell received the contract to develop and manufacture the Orbiter, as well as manage overall vehicle integration, on July 25, 1972.

By this time, the accepted design of the Space Shuttle was quite similar to the vehicles that eventually entered service. However, a few design changes would follow.

NASA made a decision to scrap two abort solid rocket motor assemblies which would have been attached to the Orbiter's tail. During an in-flight emergency, these motors would have been fired to propel the Orbiter away from its main solid rocket boosters.

It was determined that the Space Shuttle's main engines would be able to adequately guide the spacecraft away from the solid rocket boosters if a "Return-to-Launch Site" (RTLS) abort became necessary.

In addition, two turbofan engines which would have been fitted to the Orbiter's rear fuselage were scrapped. The turbofan engines would have enabled the Orbiter to maintain powered flight during landing operations and powered flight transfer between ground facilities.

Instead, NASA decided that the Orbiter could safely glide to a landing. Point-to-point flying of the Orbiter between facilities would be accomplished by carrying the spacecraft "piggyback" atop a modified Boeing 747 aircraft.

Martin Marietta was granted a construction contract for the Space Shuttle's External Tank (ET) in August, 1973. Originally, this contract specified that a small solid rocket booster be attached atop the ET.

The small solid rocket booster would be fired following ET jettison to propel the tank back toward the atmosphere. However, studies indicated that the ET could not achieve orbit on its own inertia and would fall back, then break up in the atmosphere by itself.

Thiokol Corporation was granted a contract to manufacture the Space Shuttle's Solid Rocket Boosters (SRB) in November, 1973. The company had already demonstrated a successful track record of providing reliable solid rocket boosters for a plethora of rockets.

A dispute regarding the SRB contract was initiated by Lockheed following its issuance. While the contract remained with Thiokol after a resolution of the action, the grievance process effectively froze the contract until June, 1974.

Rockwell began work on Space Shuttle Enterprise, designated Orbiter Vehicle-101 (OV-101), on June 4, 1974. All of the subcontractors delivered their Enterprise components to Rockwell by the end of 1975.

Enterprise was rolled out of the Rockwell hangar at Palmdale, California on September 17, 1976. The spacecraft was subsequently rolled to the NASA Dryden Flight Research Center at Edwards Air Force Base, California for flight testing.

Rockwell continued the development of Space Shuttles Columbia (OV-102), Discovery (OV-103) and Atlantis (OV-104). Although Enterprise was intended to be re-fitted as an operational Space Shuttle, NASA opted instead to construct Challenger (OV-099) from what was originally a high-fidelity Structural Test Article (STA-099).

NASA anticipated that its full fleet of four Space Shuttles would be in complete operation by 1984. NASA would decide to build a fifth operational Space Shuttle, Endeavour (OV-105), specifically to replace Challenger, which was lost on January 28, 1986. However, a fifth operational Space Shuttle was not originally anticipated.

NASA expected the Space Shuttle fleet to ultimately complete 25 to 60 missions per year. Plans called for up to 20 launches per year from each of three launch pads.

Although NASA reviewed several detailed proposals for constructing virgin Space Shuttle processing, launch and landing sites in various parts of the country, the space agency wisely opted to conserve scarce resources by modifying existing facilities.

The two Apollo launch pads at the Kennedy Space Center, 39A and 39B, were renovated for the Space Shuttle. A third Space Shuttle launch site was constructed at Vandenberg Air Force Base, California by renovating Titan III launch complex SLC-6, nicknamed "Slick-6", although Space Shuttles never ended up being launched from there.

One of the first important tasks of the Space Shuttle fleet was to have been to boost the Skylab space station to a higher orbit. NASA had considered renovating and occupying Skylab as a cost-effective way of starting up a "new" space station program.

When Skylab was initially abandoned on February 8, 1974 it was purposely boosted to a slightly higher orbit which varied from 269 to 283 miles. Calculations indicated that Skylab would remain in orbit for at least nine years, giving NASA ample time to get the Space Shuttle program rolling.

NASA had optimistically envisioned that a Space Shuttle would be able to attempt a docking with Skylab as early as the fifth Space Shuttle flight, which was originally expected to occur as early as the latter part of 1979.

The Skylab rescue mission was formally approved by NASA in September, 1977 and slated for the fifth Space Shuttle flight. In November, 1977 NASA awarded a contract to Martin Marietta for the design and construction of suitable docking and boost mechanisms.

By late 1978, National Oceanographic and Atmospheric Administration studies indicated that solar activity was forecast to become the second most intense in the century, with solar winds likely to be strong enough to push Skylab back into the atmosphere within a year.

The revelation prompted NASA to determine how, if necessary, Skylab could be guided back to Earth in a manner necessary to avoid damage to populated areas. NASA was also prompted to step up its development of Space Shuttle hardware necessary to save the space station.

Martin Marietta had already designed a teleoperator docking unit that could be remotely guided by an astronaut to dock with Skylab. Once docking was completed, engines in the docking mechanism could be fired to boost Skylab to a safe orbit.

The docking unit was scheduled to be delivered to the Kennedy Space Center by August, 1979 for a Space Shuttle flight scheduled for September, 1979. Due to development delays, the September, 1979 Space Shuttle flight would be the third, not the fifth as envisioned.

It was discovered that Skylab operational systems were working well, and NASA remained optimistic that the space station could be saved. But time was clearly running out. The effort to save Skylab ended abruptly in December, 1978.

NASA had run into development problems with the Space Shuttle Main Engines, and it became clear that even the first Space Shuttle launch would not occur until well after the solar winds had forced the Skylab orbit to decay beyond hope of rescue.

On December 15, 1978 NASA Administrator Robert Frosch informed President Jimmy Carter that Skylab could not be saved, and that NASA would attempt to guide the space station to a controlled re-entry as far away from populated areas as possible.

Skylab, however, would refuse to die quietly. At 3:45 a.m. EDT on July 11, 1979 controllers at the NASA Johnson Space Center commanded Skylab to tumble, hoping the space station would break apart upon re-entry. It did not, however, break apart as expected, and at 12:37 p.m. EDT on July 11, 1979 Skylab rained debris near Perth, Australia.

Although the Skylab rescue mission was never completed, the Space Shuttle fleet was slated to support the launch of a plethora of scientific, commercial and military satellites. It would also facilitate on-orbit scientific investigations and aid NASA in a slower, more methodical approach to completing a space station.

The Space Shuttle fleet was never, however, destined to perform up to 60 missions per year as intended. As NASA approached a more modest launch rate of about 24 missions per year by the late 1980's, the Space Shuttle had already proven to be much more expensive and time-consuming to service and maintain than originally envisioned.

And, the entire program was halted on January 28, 1986 when Space Shuttle Challenger exploded 73 seconds after launch. This was just the 25th Space Shuttle mission, and it became stunningly clear that major modifications to the entire Space Shuttle program were called for.

With the launch of Space Shuttle Discovery on September 29, 1988 NASA entered a brand new era of Space Shuttle operations, adopting a more relaxed pace averaging about eight launches per year. Learning from one of its greatest tragedies, NASA was able to rebuild and maintain a Space Shuttle program that has been remarkably safe and reliable.

In April, 1996 NASA began a four-phase plan to keep the existing Space Shuttle fleet healthy and flying through at least the year 2012. The plan also proposed modifications and upgrades that might keep the Space Shuttle fleet flying through the year 2030.

Called the Space Shuttle Upgrade Program, some of the modifications have already been implemented. Phase One of the plan calls for the necessary improvements to the Space Shuttle to allow it to support construction and maintenance of the International Space Station, which will be the chief program goal well into the 21st Century.

Phase Two of the plan calls for operational and cost improvements in ground operations that will decrease Space Shuttle servicing and maintenance time in order to support an average of 15 launches per year. A new Checkout and Launch Control System is under development at the Kennedy Space Center to facilitate this goal.

Phase Three of the plan calls for a number of modifications to Space Shuttle Orbiter on-board systems which will also result in decreased processing and maintenance time. More ambitious elements of this plan call for completely replacing toxic fuels with non-toxic fuels in key Orbiter systems.

Phase Four of the plan calls for significant re-design of the Space Shuttle fleet and its basic configuration. An interesting proposal in this phase is the introduction of a Liquid Fly-back Booster (LFBB), which would fly back to the launch site and save precious servicing time.

No one can say exactly which direction the Space Shuttle program will take in the 21st Century. But, if NASA is able to implement all of its Space Shuttle Upgrade Program, there is a chance that at the end of the Space Shuttle program, the vehicle may look and perform like it was originally intended to when the program began in the late 1960's.

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