Before the Apollo 11Moon landing in 1969, NASA began studies of Space Shuttle designs as early as October 1968. The early studies were denoted "Phase A", and in June 1970, "Phase B", which were more detailed and specific. The primary intended use of the Space Shuttle was supporting the future space station, ferrying a minimum crew of four and about 20,000 pounds (9,100kg) of cargo, and being able to be rapidly turned around for future flights.
Two designs emerged as front-runners. One was designed by engineers at the Manned Spaceflight Center, and championed especially by George Mueller. This was a two-stage system with delta-winged spacecraft, and generally complex. An attempt to re-simplify was made in the form of the DC-3, designed by Maxime Faget, who had designed the Mercury capsule among other vehicles. Numerous offerings from a variety of commercial companies were also offered but generally fell by the wayside as each NASA lab pushed for its own version.
All of this was taking place in the midst of other NASA teams proposing a wide variety of post-Apollo missions, a number of which would cost as much as Apollo or more[citation needed]. As each of these projects fought for funding, the NASA budget was at the same time being severely constrained. Three were eventually presented to Vice President Agnew in 1969. The shuttle project rose to the top, largely due to tireless campaigning by its supporters[citation needed]. By 1970 the shuttle had been selected as the one major project for the short-term post-Apollo time frame.
When funding for the program came into question, there were concerns that the project might be canceled. This led to an effort to interest the US Air Force in using the shuttle for their missions as well. The Air Force was mildly interested but demanded a much larger vehicle, far larger than the original concepts, which NASA accepted since it was also beneficial to their own plans. To lower the development costs of the resulting designs, boosters were added, a throw-away fuel tank was adopted, and many other changes were made that greatly lowered the reusability and greatly added to the vehicle and operational costs. With the Air Force's assistance, the system emerged in its operational form.
Based on the advice of the Space Council, President Nixon made the decision to pursue the low Earth orbital infrastructure option. This program mainly consisted of the construction of a space station, along with the development of a Space Shuttle. Funding restrictions precluded pursuing the development of both programs simultaneously, however. NASA chose to develop the Space Shuttle program first, and then planned to use the shuttle in order to construct and service a space station.
Shuttle design debate
Original North American Rockwell Shuttle delta wing design, 1969: fully reusable, with a flyback crewed boosterMaxime Faget's DC-3 concept employed conventional straight wings.
During the early shuttle studies, there was a debate over the optimal shuttle design that best-balanced capability, development cost, and operational cost. Initially, a fully reusable design was preferred. This involved a very large winged crewed booster which would carry a smaller winged crewed orbiter. The booster vehicle would lift the orbiter to a certain altitude and speed, then separate. The booster would return and land horizontally, while the orbiter continued into low Earth orbit. After completing its mission, the winged orbiter would re-enter and land horizontally on a runway. The idea was that full reusability would promote lower operating costs.
However, further studies showed a huge booster was needed to lift an orbiter with the desired payload capability. In space and aviation systems, the cost is closely related to mass, so this meant the overall vehicle cost would be very high. Both booster and orbiter would have rocket engines plus jet engines for use within the atmosphere, plus separate fuel and control systems for each propulsion mode. In addition, there were concurrent discussions about how much funding would be available to develop the program.
Another competing approach was maintaining the Saturn V production line and using its large payload capacity to launch a space station in a few payloads rather than many smaller shuttle payloads. A related concept was servicing the space station using the Air Force Titan III-M to launch a larger Gemini capsule, called "Big Gemini", or a smaller "glider" version of the shuttle with no main engines and a 15ft ×30ft (4.6m ×9.1m) payload bay.
The shuttle supporters answered that given enough launches, a reusable system would have lower overall costs than disposable rockets. If dividing total program costs over a given number of launches, a high shuttle launch rate would result in lower pre-launch costs. This in turn would make the shuttle cost-competitive with or superior to expendable launchers. Some theoretical studies mentioned 55 shuttle launches per year; however, the final design chosen did not support that launch rate. In particular, the maximum external tank production rate was limited to 24 tanks per year at NASA's Michoud Assembly Facility.
The combined space station and Air Force payload requirements were not sufficient to reach desired shuttle launch rates. Therefore, the plan was for all future U.S. space launches—space stations, Air Force, commercial satellites, and scientific research—to use only the Space Shuttle. Most other expendable boosters would be phased out.
The reusable booster was eventually abandoned due to several factors: high price (combined with limited funding), technical complexity, and development risk. Instead, a partially (not fully) reusable design was selected, where an external propellant tank was discarded for each launch, and the booster rockets and shuttle orbiter were refurbished for reuse.
Initially, the orbiter was to carry its own liquid propellant. However, studies showed carrying the propellant in an external tank allowed a larger payload bay in an otherwise much smaller craft. It also meant throwing away the tank after each launch, but this was a relatively small portion of operating costs.
Earlier designs assumed the winged orbiter would also have jet engines to assist maneuvering in the atmosphere after re-entering. However NASA ultimately chose a gliding orbiter, based partially on experience from previous rocket-then-glide vehicles such as the X-15 and lifting bodies. Omitting the jet engines and their fuel would reduce complexity and increase payload.
Another decision was the size of the crew. Some said that the shuttle should not carry more than four, the most that could use ejection seats. A commander, pilot, mission specialist, and payload specialist were sufficient for any mission. NASA expected to carry more space flight participants as payload specialists, so designed the vehicle to carry more.[2]
The last remaining debate was over the nature of the boosters. NASA examined four solutions to this problem: development of the existing Saturn lower stage, simple pressure-fed liquid-fuel engines of a new design, a large single solid rocket, or two (or more) smaller ones. Engineers at NASA's Marshall Space Flight Center (where the Saturn V development was managed) were particularly concerned about solid rocket reliability for crewed missions.
Air Force involvement
During the mid-1960s the United States Air Force had both of its major piloted space projects, X-20 Dyna-Soar and Manned Orbiting Laboratory, canceled. This demonstrated its need to cooperate with NASA to place military astronauts in orbit. In turn, by serving Air Force needs, the Shuttle became a truly national system, carrying all military as well as civilian payloads.[3]
NASA sought Air Force support for the shuttle. After the Six-Day War and the Soviet invasion of Czechoslovakia exposed limitations in the United States satellite reconnaissance network, Air Force involvement emphasized the ability to launch spy satellites southward into polar orbit from Vandenberg AFB. This required higher energies than for lower inclination orbits. The Air Force also hoped that a shuttle could retrieve Soviet satellites and quickly land. It thus desired the ability to land at the Vandenberg liftoff point after one orbit, despite the Earth rotating 1,000 miles beneath the orbital track. This required a larger delta wing size than the earlier simple "DC-3" shuttle. However, NASA also desired this increased maneuvering capability since further studies had shown the DC-3 shuttle design had limitations not initially foreseen. The Air Force launched more than 200 satellite reconnaissance missions between 1959 and 1970, and the military's large volume of payloads would be valuable in making the shuttle more economical.[4]:213–216
Despite the potential benefits for the Air Force, the military was satisfied with its expendable boosters and did not need or want the shuttle as much as NASA did. Because the space agency needed outside support, the Defense Department (DoD) and the National Reconnaissance Office (NRO) gained primary control over the design process. For example, NASA planned a 40-by-12-foot (12.2 by 3.7m) cargo bay, but NRO specified a 60-by-15-foot (18.3 by 4.6m) bay because it expected future intelligence satellites to become larger. When Faget again proposed a 12ft (3.7m) wide payload bay, the military almost immediately insisted on retaining the 15ft (4.6m) width. The Air Force also gained the equivalent of the use of one of the shuttles for free despite not paying for the shuttle's development or construction. In exchange for the NASA concessions, the Air Force testified to the Senate Space Committee on the shuttle's behalf in March 1971.[4]:216,232–234[5]
As another incentive for the military to use the shuttle, Congress reportedly told DoD that it would not pay for any satellites not designed to fit into the shuttle cargo bay.[6] Although NRO did not redesign existing satellites for the shuttle, the vehicle retained the ability to retrieve large cargos such as the KH-9 HEXAGON from orbit for refurbishment, and the agency studied resupplying the satellite in space.[7]
Potential military use of the shuttle—including the possibility of using it to verify Soviet compliance with the SALT II treaty—probably caused President Jimmy Carter to not cancel the shuttle in 1979 and 1980, when the program was years behind schedule and hundreds of millions of dollars over budget.[8] The Air Force planned on having its own fleet of shuttles and re-built a separate launch facility originally derived from the canceled Manned Orbiting Laboratory program at Vandenberg called Space Launch Complex Six (SLC-6). However, for various reasons, due in large part to the loss of Space Shuttle Challenger on January 28, 1986, work on SLC-6 was eventually discontinued no shuttle launches from that location ever took place. SLC-6 was eventually used for launching the Lockheed Martin-built Athena expendable launch vehicles, which included the successful IKONOS commercial Earth observation satellite in September 1999 before being reconfigured once again to handle the new generation of BoeingDelta IV's. The first launch of the Delta IV heavy from SLC-6 occurred in June 2006, launching NROL-22, a classified satellite for the U.S. National Reconnaissance Office (NRO).
Final design
Final semi-reusable design with throwaway external fuel tank and recoverable solid rocket boosters
While NASA would likely have chosen liquid boosters had it complete control over the design, the Office of Management and Budget insisted on less expensive solid boosters due to their lower projected development costs.[4]:416–423[9] While a liquid-fueled booster design provided better performance, lower per-flight costs, less environmental impact and less developmental risk, solid boosters were seen as requiring less funding to develop at a time when the Shuttle program had many different elements competing for limited development funds. The final design which was selected as a winged orbiter with three liquid-fueled engines, a large expendable external tank which held liquid propellant for these engines, and two reusable solid rocket boosters.
In the spring of 1972 Lockheed Aircraft, McDonnell Douglas, Grumman, and North American Rockwell submitted proposals to build the shuttle. The NASA selection group thought that Lockheed's shuttle was too complex and too expensive, and the company had no experience with building crewed spacecraft. McDonnell Douglas's was too expensive and had technical issues. Grumman had an excellent design which also seemed too expensive. North American's shuttle had the lowest cost and most realistic cost projections, its design was the easiest for ongoing maintenance, and the Apollo 13 accident involving North American's command and service module demonstrated its experience with electrical system failures. NASA announced its choice of North American on July 26, 1972.[4]:429–432
The Space Shuttle program used the HAL/S programming language.[10] The first microprocessor used was the 8088 and later the 80386. The Space Shuttle orbiter avionics computer was the IBM AP-101.
Early concept of how the Space Shuttle was to be serviced
Opinions differ on the lessons of the Shuttle. It was developed with the original development cost and time estimates given to President Richard M. Nixon in 1971,[11] at a cost of $6.744billion in 1971 dollars (equivalent to $37.5billion in 2022)[12] versus an original $5.15billion estimate.[13] The operational costs, flight rate, payload capacity, and reliability have been different than anticipated, however.[11]
The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program name was Space Transportation System (STS), taken from a 1969 plan for a system of reusable spacecraft where it was the only item funded for development.
A single-stage-to-orbit (SSTO) vehicle reaches orbit from the surface of a body using only propellants and fluids and without expending tanks, engines, or other major hardware. The term usually, but not exclusively, refers to reusable vehicles. To date, no Earth-launched SSTO launch vehicles have ever been flown; orbital launches from Earth have been performed by either fully or partially expendable multi-stage rockets.
The Space Shuttle program was the fourth human spaceflight program carried out by the U.S. National Aeronautics and Space Administration (NASA), which accomplished routine transportation for Earth-to-orbit crew and cargo from 1981 to 2011. Its official name, Space Transportation System (STS), was taken from a 1969 plan for a system of reusable spacecraft of which it was the only item funded for development. It flew 135 missions and carried 355 astronauts from 16 countries, many on multiple trips.
The RM-81 Agena was an American rocket upper stage and satellite bus which was developed by Lockheed Corporation initially for the canceled WS-117L reconnaissance satellite program. Following the split-up of WS-117L into SAMOS and Corona for image intelligence, and MIDAS for early warning, the Agena was later used as an upper stage, and an integrated component, for several programs, including Corona reconnaissance satellites and the Agena Target Vehicle used to demonstrate rendezvous and docking during Project Gemini. It was used as an upper stage on the Atlas, Thor, Thorad and Titan IIIB rockets, and considered for others including the Space Shuttle and Atlas V. A total of 365 Agena rockets were launched between February 28, 1959 and February 1987. Only 33 Agenas carried NASA payloads and the vast majority were for DoD programs.
A reusable launch vehicle has parts that can be recovered and reflown, while carrying payloads from the surface to outer space. Rocket stages are the most common launch vehicle parts aimed for reuse. Smaller parts such as rocket engines and boosters can also be reused, though reusable spacecraft may be launched on top of an expendable launch vehicle. Reusable launch vehicles do not need to make these parts for each launch, therefore reducing its launch cost significantly. However, these benefits are diminished by the cost of recovery and refurbishment.
The Lockheed Martin X-33 was a proposed uncrewed, sub-scale technology demonstrator suborbital spaceplane that was developed for a period in the 1990s. The X-33 was a technology demonstrator for the VentureStar orbital spaceplane, which was planned to be a next-generation, commercially operated reusable launch vehicle. The X-33 would flight-test a range of technologies that NASA believed it needed for single-stage-to-orbit reusable launch vehicles, such as metallic thermal protection systems, composite cryogenic fuel tanks for liquid hydrogen, the aerospike engine, autonomous (uncrewed) flight control, rapid flight turn-around times through streamlined operations, and its lifting body aerodynamics.
Delta IV was a group of five expendable launch systems in the Delta rocket family introduced in the early 2000s. Originally designed by Boeing's Defense, Space and Security division for the Evolved Expendable Launch Vehicle (EELV) program, the Delta IV became a United Launch Alliance (ULA) product in 2006. The Delta IV was primarily a launch vehicle for United States Air Force (USAF) military payloads, but was also used to launch a number of United States government non-military payloads and a single commercial satellite.
Titan IV was a family of heavy-lift space launch vehicles developed by Martin Marietta and operated by the United States Air Force from 1989 to 2005. Launches were conducted from Cape Canaveral Air Force Station, Florida and Vandenberg Air Force Base, California.
A launch vehicle is typically a rocket-powered vehicle designed to carry a payload from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage rocket, but the term is more general and also encompasses vehicles like the Space Shuttle. Most launch vehicles operate from a launch pad, supported by a launch control center and systems such as vehicle assembly and fueling. Launch vehicles are engineered with advanced aerodynamics and technologies, which contribute to high operating costs.
Atlas V is an expendable launch system and the fifth major version in the Atlas launch vehicle family. It was originally designed by Lockheed Martin, now being operated by United Launch Alliance (ULA), a joint venture between Lockheed Martin and Boeing. It is used for DoD, NASA, and Commercial payloads. It is America's longest-serving active rocket. After 87 launches, in August 2021 ULA announced that Atlas V would be retired, and all 29 remaining launches had been sold. As of 6 October 2023, 17 launches remain.
The Exploration Systems Architecture Study (ESAS) is the official title of a large-scale, system level study released by the National Aeronautics and Space Administration (NASA) in November 2005 of his goal of returning astronauts to the Moon and eventually Mars—known as the Vision for Space Exploration. The Constellation Program was cancelled in 2010 by the Obama Administration and replaced with the Space Launch System, later renamed as the Artemis Program in 2017 under the Trump Administration.
Space Launch Complex 6 at Vandenberg Space Force Base in California is a launch pad and support area. The site was originally developed starting in 1966, but no launches occurred until 1995, as it was repurposed sequentially for three programs that were subsequently cancelled. Initially to be used for Titan IIIM rockets and the Manned Orbiting Laboratory, these were cancelled before construction of SLC-6 was complete. The complex was later rebuilt to serve as the west coast launch site for the Space Shuttle, but went unused due to budget, safety and political considerations. The pad was subsequently used for four Athena rocket launches before being modified to support the Delta IV launch vehicle family, which used the pad for ten launches from 2006 until 2022. The last Delta IV launched in September 2022, and SpaceX leased SLC-6 in 2023 to convert it to launch Falcon 9 and Falcon Heavy starting in 2025.
Criticism of the Space Shuttle program stemmed from claims that NASA's Space Shuttle program failed to achieve its promised cost and utility goals, as well as design, cost, management, and safety issues. Fundamentally, it failed in the goal of reducing the cost of space access. Space Shuttle incremental per-pound launch costs ultimately turned out to be considerably higher than those of expendable launchers. In 2010, the incremental cost per flight of the Space Shuttle was $409 million, or $14,186 per kilogram to low Earth orbit (LEO). In contrast, the comparable Proton launch vehicle cost was $141 million, or $6,721 per kilogram to LEO and the Soyuz 2.1 was $55 million, or $6,665 per kilogram, despite these launch vehicles not being reusable.
Atlas is a family of US missiles and space launch vehicles that originated with the SM-65 Atlas. The Atlas intercontinental ballistic missile (ICBM) program was initiated in the late 1950s under the Convair Division of General Dynamics. Atlas was a liquid propellant rocket burning RP-1 kerosene fuel with liquid oxygen in three engines configured in an unusual "stage-and-a-half" or "parallel staging" design: two outboard booster engines were jettisoned along with supporting structures during ascent, while the center sustainer engine, propellant tanks and other structural elements remained connected through propellant depletion and engine shutdown.
The DC-3 was one of several early design proposals for the NASA Space Shuttle designed by Maxime Faget at the Manned Spacecraft Center (MSC) in Houston. It was nominally developed by North American Aviation (NAA), although it was a purely NASA-internal design. Unlike the design that eventually emerged, the DC-3 was a fully reusable launch vehicle two-stage-to-orbit spaceplane design with a small payload capacity of about 12,000 lb (5,400 kg) and limited maneuverability. Its inherent strengths were good low-speed handling during landing, and a low-risk development that was relatively immune to changes in weight and balance.
The Lockheed Star Clipper was a proposed Earth-to-orbit spaceplane based on a large lifting body spacecraft and a wrap-around drop tank. Originally proposed during a United States Air Force program in 1966, the basic Star Clipper concept lived on during the early years of the NASA Space Shuttle program, and as that project evolved, in a variety of new versions like the LS-200.
The DARPA XS-1 was an experimental spaceplane/booster with the planned capability to deliver small satellites into orbit for the U.S. Military. It was reported to be designed to be reusable as frequently as once a day, with a stated goal of doing so for 10 days straight. The XS-1 was intended to directly replace the first stage of a multistage rocket by taking off vertically and flying to hypersonic speed and high suborbital altitude, enabling one or more expendable upper stages to separate and deploy a payload into low Earth orbit. The XS-1 would then return to Earth, where it could ostensibly be serviced fast enough to repeat the process at least once every 24 hours.
A super heavy-lift launch vehicle is a rocket that can lift to low Earth orbit a "super heavy payload", which is defined as more than 50 metric tons (110,000 lb) by the United States and as more than 100 metric tons (220,000 lb) by Russia. It is the most capable launch vehicle classification by mass to orbit, exceeding that of the heavy-lift launch vehicle classification.
New Glenn is a heavy-lift orbital launch vehicle in development by Blue Origin, named after NASA astronaut John Glenn, the first American astronaut to orbit Earth. Design work on the vehicle began in 2012; illustrations of the vehicle, and the high-level specifications, were initially publicly unveiled in September 2016. New Glenn is a two-stage rocket with a diameter of 7 m (23 ft). Its first stage will be powered by seven BE-4 engines that are also being designed and manufactured by Blue Origin.
During the lifetime of the Space Shuttle, Rockwell International and many other organizations studied various Space Shuttle designs. These involved different ways of increasing cargo and crew capacity, as well as investigating further reusability. A large focus of these designs were related to developing new shuttle boosters and improvements to the central tank, but also looked to expand NASA's ability to launch deep space missions and build modular space stations. Many of these concepts and studies would shape the concepts and programs of the 2000s such as the Constellation, Orbital Space Plane Program, and Artemis program.
1 2 "Columbia Accident Investigation Board Public Hearing". Columbia Accident Investigaion Board Report(PDF) (Technical report). Vol.VI. Houston, Texas (published October 2003). April 23, 2003. pp.219–245. Archived(PDF) from the original on May 11, 2023.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
