NASA Space Shuttle decision
Encyclopedia
Even before the Apollo moon landing in 1969, in October 1968, NASA
began early studies of space shuttle designs. 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. This function would dictate most of the shuttle's features. The U.S. Air Force was also interested in using the shuttle, and NASA welcomed their participation and influence to ensure political and financial support for the shuttle program.
Initially, many potential shuttle designs were proposed during the 1960s, and they varied widely. Many were exceedingly complex. An attempt to re-simplify was made in the form of the "DC-3" by Maxime Faget
, who had designed the Mercury capsule among other vehicles. The DC-3
was a small craft with a 20,000-pound (9 metric ton) payload, a four-man capacity, and limited aerodynamic maneuverability. At a minimum, the DC-3 provided a baseline "workable" (but not significantly advanced) system by which other systems could be compared for price-performance compromises.
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 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.
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 manned booster
which would carry a smaller winged manned 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 reenter 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, cost is closely related to weight, 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 II-M to launch a larger Gemini
capsule, called "Big Gemini
", rather than using the shuttle.
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 per-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 would 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 weren't sufficient to reach desired shuttle launch rates. Therefore the plan was for all future U.S. space launches—space station, 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 a 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 propellent tank
was discarded for each launch, and the booster rocket
s 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 reentering. 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.
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 manned missions.
boosters, due to their lower projected development costs relative to a liquid propellant booster. 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 was 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
.
6.744 billion in 1971 dollars versus an original $5.15 billion estimate. The operational costs, flight rate, payload capacity, and reliability have been different than anticipated, however.
provided seating for 74 passengers in the Orbiter payload bay, with support for three days in Earth orbit. With a smaller 64 seat orbiter, costs for the late 1980s would be around 1.5 million USD per seat per launch. The Rockwell passenger module had two decks, 4 seats across on top and 2 on the bottom, including a 25 inch (63.5 cm) wide aisle and extra storage space.
Another design was Space Habitation Design Associates 1983 proposal for 72 passengers in the Space Shuttle Payload bay. Passengers were located in 6 sections, each with windows and its own loading ramp at launch, and with seats in different configurations for launch and landing. Another proposal was based on the Spacelab habitation modules, which provided 32 seats in the payload bay in addition to those in the cockpit area.
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
began early studies of space shuttle designs. 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. This function would dictate most of the shuttle's features. The U.S. Air Force was also interested in using the shuttle, and NASA welcomed their participation and influence to ensure political and financial support for the shuttle program.
Initially, many potential shuttle designs were proposed during the 1960s, and they varied widely. Many were exceedingly complex. An attempt to re-simplify was made in the form of the "DC-3" by Maxime Faget
Maxime Faget
Maxime "Max" A. Faget was the designer of the Mercury capsule, and contributed to the later Gemini and Apollo spacecraft as well as the Space Shuttle.- Life :...
, who had designed the Mercury capsule among other vehicles. The DC-3
North American DC-3
The DC-3 was a proposed space shuttle designed by Maxime Faget at the Manned Spacecraft Center in Houston. The design was nominally developed by North American Aviation , although it was a purely NASA-internal design....
was a small craft with a 20,000-pound (9 metric ton) payload, a four-man capacity, and limited aerodynamic maneuverability. At a minimum, the DC-3 provided a baseline "workable" (but not significantly advanced) system by which other systems could be compared for price-performance compromises.
Decision-making process
In 1969, United States Vice President Agnew chaired the National Aeronautics and Space Council, which discussed post-Apollo options for manned space activities. The recommendations of the Council would heavily influence the decisions of the administration. The Council considered four major options:- A Manned mission to MarsManned mission to MarsA manned mission to Mars has been the subject of science fiction, engineering, and scientific proposals throughout the 20th century and into the 21st century...
- follow-on lunar programMoon landingA moon landing is the arrival of a spacecraft on the surface of the Moon. This includes both manned and unmanned missions. The first human-made object to reach the surface of the Moon was the Soviet Union's Luna 2 mission on 13 September 1959. The United States's Apollo 11 was the first manned...
- A low earth orbitalLow Earth orbitA low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
infrastructure program - Discontinuing manned space activities
Based on the advice of the Space Council, President Nixon made the decision to pursue the low earth orbital
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
infrastructure option. This program mainly consisted of construction of a space station
Space station
A space station is a spacecraft capable of supporting a crew which is designed to remain in space for an extended period of time, and to which other spacecraft can dock. A space station is distinguished from other spacecraft used for human spaceflight by its lack of major propulsion or landing...
, along with the development of a Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
. Funding restrictions precluded pursuing the development of both programs simultaneously, however. NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
chose to develop the Space Shuttle program
Space Shuttle program
NASA's Space Shuttle program, officially called Space Transportation System , was the United States government's manned launch vehicle program from 1981 to 2011...
first, and then planned to use the shuttle in order to construct and service a space station.
Shuttle design debate
Booster rocket
A booster rocket is either the first stage of a multi-stage launch vehicle, or else a strap-on rocket used to augment the core launch vehicle's takeoff thrust and payload capability. Boosters are generally necessary to launch spacecraft into Earth orbit or beyond...
which would carry a smaller winged manned orbiter. The booster vehicle
Booster rocket
A booster rocket is either the first stage of a multi-stage launch vehicle, or else a strap-on rocket used to augment the core launch vehicle's takeoff thrust and payload capability. Boosters are generally necessary to launch spacecraft into Earth orbit or beyond...
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
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
. After completing its mission, the winged orbiter would reenter 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, cost is closely related to weight, 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
Saturn V
The Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...
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 II-M to launch a larger Gemini
Project Gemini
Project Gemini was the second human spaceflight program of NASA, the civilian space agency of the United States government. Project Gemini was conducted between projects Mercury and Apollo, with ten manned flights occurring in 1965 and 1966....
capsule, called "Big Gemini
Big Gemini
Big Gemini was proposed to NASA by McDonnell Douglas in August, 1969, as an advanced version of the Gemini spacecraft system...
", rather than using the shuttle.
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 per-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 would not support that launch rate. In particular the maximum external tank
Space Shuttle external tank
A Space Shuttle External Tank is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplies the fuel and oxidizer under pressure to the three Space Shuttle Main Engines in the orbiter...
production rate was limited to 24 tanks per year at NASA's Michoud Assembly Facility
Michoud Assembly Facility
The Michoud Assembly Facility is an 832-acre site owned by NASA and located in New Orleans East, a large district within the city of New Orleans, Louisiana, United States. Organizationally, it is part of NASA's Marshall Space Flight Center...
.
The combined space station and Air Force payload requirements weren't sufficient to reach desired shuttle launch rates. Therefore the plan was for all future U.S. space launches—space station, 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 a 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 propellent tank
Space Shuttle external tank
A Space Shuttle External Tank is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplies the fuel and oxidizer under pressure to the three Space Shuttle Main Engines in the orbiter...
was discarded for each launch, and the booster rocket
Booster rocket
A booster rocket is either the first stage of a multi-stage launch vehicle, or else a strap-on rocket used to augment the core launch vehicle's takeoff thrust and payload capability. Boosters are generally necessary to launch spacecraft into Earth orbit or beyond...
s and shuttle orbiter were refurbished for reuse.
Initially the orbiter was to carry its own liquid propellant
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
. However studies showed carrying the propellant in an external tank
Space Shuttle external tank
A Space Shuttle External Tank is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplies the fuel and oxidizer under pressure to the three Space Shuttle Main Engines in the orbiter...
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 reentering. 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
Lifting body
A lifting body is a fixed-wing aircraft configuration in which the body itself produces lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as a fuselage with little or no conventional wing...
. Omitting the jet engines and their fuel would reduce complexity and increase payload.
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
Marshall Space Flight Center
The George C. Marshall Space Flight Center is the U.S. government's civilian rocketry and spacecraft propulsion research center. The largest center of NASA, MSFC's first mission was developing the Saturn launch vehicles for the Apollo moon program...
(where the Saturn V
Saturn V
The Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...
development was managed) were particularly concerned about solid rocket
Solid rocket
A solid rocket or a solid-fuel rocket is a rocket engine that uses solid propellants . The earliest rockets were solid-fuel rockets powered by gunpowder; they were used by the Chinese in warfare as early as the 13th century and later by the Mongols, Arabs, and Indians.All rockets used some form of...
reliability for manned missions.
Final design
NASA eventually decided to use the smaller solid rocketSolid rocket
A solid rocket or a solid-fuel rocket is a rocket engine that uses solid propellants . The earliest rockets were solid-fuel rockets powered by gunpowder; they were used by the Chinese in warfare as early as the 13th century and later by the Mongols, Arabs, and Indians.All rockets used some form of...
boosters, due to their lower projected development costs relative to a liquid propellant booster. 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 was a winged orbiter
Space Shuttle program
NASA's Space Shuttle program, officially called Space Transportation System , was the United States government's manned launch vehicle program from 1981 to 2011...
with three liquid fueled engines
Space Shuttle main engine
The RS-25, otherwise known as the Space Shuttle Main Engine , is a reusable liquid-fuel rocket engine built by Pratt & Whitney Rocketdyne for the Space Shuttle, running on liquid hydrogen and oxygen. Each Space Shuttle was propelled by three SSMEs mated to one powerhead...
, a large expendable external tank
Space Shuttle external tank
A Space Shuttle External Tank is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplies the fuel and oxidizer under pressure to the three Space Shuttle Main Engines in the orbiter...
which held liquid propellant
Liquid rocket
A liquid-propellant rocket or a liquid rocket is a rocket engine that uses propellants in liquid form. Liquids are desirable because their reasonably high density allows the volume of the propellant tanks to be relatively low, and it is possible to use lightweight pumps to pump the propellant from...
for these engines, and two reusable solid rocket boosters
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
.
Retrospection after three decades
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, at a cost of US$United States dollar
The United States dollar , also referred to as the American dollar, is the official currency of the United States of America. It is divided into 100 smaller units called cents or pennies....
6.744 billion in 1971 dollars versus an original $5.15 billion estimate. The operational costs, flight rate, payload capacity, and reliability have been different than anticipated, however.
Passenger modules
One area of Space Shuttle applications is an expanded crew. Crews of up to 8 have been flown in the Orbiter, but it can hold at least a crew of ten. Various proposals for filling the payload bay with additional passengers have also been proposed as early as 1979. A proposal by RockwellRockwell
- People :* Dick Rockwell, an American comic strip and comic book artist, nephew of Norman Rockwell* Francis W. Rockwell, a United States Congressman from Massachusetts* Francis W...
provided seating for 74 passengers in the Orbiter payload bay, with support for three days in Earth orbit. With a smaller 64 seat orbiter, costs for the late 1980s would be around 1.5 million USD per seat per launch. The Rockwell passenger module had two decks, 4 seats across on top and 2 on the bottom, including a 25 inch (63.5 cm) wide aisle and extra storage space.
Another design was Space Habitation Design Associates 1983 proposal for 72 passengers in the Space Shuttle Payload bay. Passengers were located in 6 sections, each with windows and its own loading ramp at launch, and with seats in different configurations for launch and landing. Another proposal was based on the Spacelab habitation modules, which provided 32 seats in the payload bay in addition to those in the cockpit area.
See also
- Space shuttle programSpace Shuttle programNASA's Space Shuttle program, officially called Space Transportation System , was the United States government's manned launch vehicle program from 1981 to 2011...
- Single-stage-to-orbitSingle-stage-to-orbitA single-stage-to-orbit vehicle reaches orbit from the surface of a body without jettisoning hardware, expending only propellants and fluids. The term usually, but not exclusively, refers to reusable vehicles....
- Space Shuttle abort modesSpace Shuttle abort modesA Space Shuttle abort was an emergency procedure due to equipment failure on NASA's Space Shuttle, most commonly during ascent. A main engine failure is a typical abort scenario. There are fewer abort options during reentry and descent...
- Buran (spacecraft)
Further reading
- Dr. Wernher Von Braun - "The Spaceplane that can put YOU in orbit" (Popular Science, July 1970) (Google Books link)
- T.A. Heppenheimer - SP-4221 The Space Shuttle Decision (NASA, 1998)
External links
- CAIB transcript concerning shuttle development
- Astronautix space shuttle article
- From Dream to Reality (1968-72)Dead link
- NASA: The Space Shuttle Decision
- INTRODUCTION TO FUTURE LAUNCH VEHICLE PLANS �[1963-2001], M. Lindroos
- 10 Space Shuttles which never flew (Lockheed Starclipper, Chrysler SERV, Phase B Shuttles, Rockwell C-1057, Shuttle C, Air Launched Sortie Vehicle (ALSV), Hermes, Buran, Shuttle II, Lockheed Martin VentureStar)