Criticism of the Space Shuttle program
Encyclopedia
Criticism of the Space Shuttle program stems from claims that NASA's
Shuttle program
has failed to achieve its promised cost and utility goals, as well as design, cost, management, and safety issues. More specifically, it has 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: by 2011, the incremental cost per flight of the Space Shuttle was estimated at $450 million, or $18,000 per kilogram to low Earth orbit
(LEO). By comparison, Russian Proton expendable launchers, still largely based on the design that dates back to 1965, are said to cost as little as $110 million, or around $5,000/kg to LEO. When all design and maintenance costs are taken into account, the final cost of the Space Shuttle program, averaged over all missions and adjusted for inflation, was estimated to come out to $1.5 billion per launch, or $60,000/kg to LEO. This should be contrasted with the originally envisioned costs of $118 per pound of payload in 1972 dollars ($1,400/kg, adjusting for inflation to 2011).
It failed in the goal of achieving reliable access to space, partly due to multi-year interruptions in launches following Shuttle failures. NASA budget pressures caused by the chronically high NASA Space Shuttle program costs have eliminated NASA manned space flight beyond low earth orbit since Apollo, and severely curtailed more productive space science using unmanned probes. NASA's promotion of and reliance on the Shuttle slowed domestic commercial expendable launch vehicle (ELV) programs until after the 1986 Challenger disaster
.
s. It would afford the opportunity to conduct science experiments on board the shuttle to be used to study the effects of space flight on humans, animals and plants. Other experiments would study how things can be manufactured in space. The shuttle would also enable astronauts to launch satellites from the shuttle and even repair satellites already out in space. The Shuttle was also intended for research into the human response to zero gravity.
The Shuttle was originally billed as a space vehicle that would be able to launch once a week and give low launch costs through amortization
. Development costs were expected to be recouped through frequent access to space. These claims were made in an effort to obtain budgetary funding from the United States Congress
. Beginning in 1981, the space shuttle began to be used for space travel. However, by the mid-1980s the concept of flying that many shuttle missions proved unrealistic and scheduled launch expectations were reduced 50%. Following the Challenger accident in 1986, missions were halted pending safety review. This hiatus became lengthy and ultimately lasted almost three years as arguments over funding and the safety of the program continued. Eventually the military resumed the use of expendable launch vehicles instead. Missions were put on hold again after the loss of Columbia in 2003. Overall, 135 missions were launched during the 30 years after the first orbital flight of Columbia, averaging approximately one every 3 months.
years as a way to rehabilitate America's post-Vietnam
prestige.
The physicist Richard Feynman
, who was appointed to the official inquiry on the Challenger disaster, estimated the risk to be "on the order
of a percent" in his report, adding, "Official management, on the other hand, claims to believe the probability of failure is a thousand times less. One reason for this may be an attempt to assure the government of NASA perfection and success in order to ensure the supply of funds. The other may be that they sincerely believed it to be true, demonstrating an almost incredible lack of communication between themselves and their working engineers.
Despite Feynman's warnings, and despite the fact that Vaughan served on safety boards and committees at NASA, the subsequent press coverage has found some evidence that NASA's relative disregard for safety might persist to this day. For example, NASA discounted the risk from small foam chunk breakage at launch and assumed that the lack of damage from prior foam collisions suggested the future risk was low.
set the pre-Challenger record by launching twice within 54 days, while Columbia
set the post-Challenger record of 88 days. Naturally, the Shuttle program's goal of returning its crew to Earth safely conflicts with the goal of a rapid and inexpensive payload launch. Furthermore, because in many cases there are no survivable abort modes
, many pieces of hardware simply must function perfectly and so must be carefully inspected before each flight. The result is high labor cost, with around 25,000 workers in Shuttle operations and labor costs of about $1 billion per year.
Some shuttle features initially presented as important to Space Station support have proved superfluous:
While the technical details of the Challenger and Columbia accidents are different, the organizational problems show similarities. In both cases events happened that were not planned for nor anticipated. Flight engineers' concerns about possible problems were not properly communicated to or understood by senior NASA managers. The vehicle gave ample warning beforehand of abnormal problems. A heavily layered, procedure-oriented bureaucratic structure inhibited necessary communication and action.
With Challenger, an O-ring
that should not have eroded at all did erode on earlier shuttle launches. Yet managers felt that because it had not previously eroded by more than 30%, this was not a hazard as there was "a factor of three safety margin". Morton-Thiokol
designed and manufactured the SRBs, and during a pre-launch conference call with NASA, Roger Boisjoly
, the Thiokol engineer most experienced with the O-rings, pleaded with management repeatedly to cancel or reschedule the launch. He raised concerns that the unusually low temperatures would stiffen the O-rings, preventing a complete seal, which was exactly what happened on the fatal flight. However, Thiokol's senior managers overruled him, dismissing his safety concerns, and allowed the launch to proceed. Challengers O-rings eroded completely through as predicted, resulting in the complete destruction of the spacecraft and the loss of all seven astronauts on board.
Columbia was destroyed because of damaged thermal protection
from foam debris that broke off from the external tank during ascent. The foam had not been designed or expected to break off, but had been observed in the past to do so without incident. The original shuttle operational specification said the orbiter thermal protection tiles were designed to withstand virtually no debris hits at all. Over time NASA managers gradually accepted more tile damage, similar to how O-ring damage was accepted. The Columbia Accident Investigation Board
called this tendency the "normalization of deviance" — a gradual acceptance of events outside the design tolerances of the craft simply because they had not been catastrophic to date.
The subject of missing or damaged thermal tiles on the Shuttle fleet only became an issue following the loss of Columbia in 2003, as it broke up on re-entry
. In fact, Shuttles had previously come back missing as many as 20 tiles without any problem. STS-1
and STS-41
had all flown with missing thermal tiles from the orbital maneuvering system pods (visible to the crew). This image from the NASA archives shows many missing tiles on the STS-1 OMS pods. The problem on Columbia was that the damage was sustained from a foam strike to the reinforced carbon-carbon
leading edge panel of the wing, not the heat tiles. The first Shuttle mission, STS-1, had a protruding gap filler that diverted hot gas into the right wheel well on re-entry, resulting in a buckling of the right main landing gear door.
's April 1981 launch, The Washington Monthly
accurately forecast many of the Shuttle's issues, including an overambitious launch schedule and the consequent higher-than-expected marginal cost per flight; the risks of depending on the Shuttle for all payloads, civilian and military; the lack of a survivable abort scenario if a Solid Rocket Booster were to fail; and the fragility of the Shuttle's thermal protection system.
In order to get the Shuttle approved, NASA over-promised its economies and utility. To justify its very large fixed operational program cost, NASA initially forced all domestic, internal, and Department of Defense
payloads to the shuttle. When that proved impossible (after the Challenger disaster), NASA used the International Space Station
(ISS) as a justification for the shuttle. Some speculate that, had NASA avoided the Shuttle program and instead continued to use Saturn
and commercially available boosters, costs might have been lower, freeing funds for manned exploration and more unmanned space science. In particular, NASA administrator Michael D. Griffin
argued in a 2007 paper that the Saturn program, if continued, could have provided six manned launches per year — two of them to the moon — at the same cost as the Shuttle program, with an additional ability to loft infrastructure for further missions:
Some have argued that the shuttle program is flawed. Achieving a reusable vehicle with early 1970s technology forced design decisions that compromised operational reliability and safety. Reusable main engines were made a priority. This necessitated that they not burn up upon atmospheric reentry, which in turn made mounting them on the orbiter itself (the one part of the shuttle system where reuse was paramount) a seemingly logical decision. However, this had the following consequences:
A concern expressed by the 1990 Augustine Commission
was that, "the civil space program is overly dependent upon the Space Shuttle for access to space." The committee pointed out, "that it was, for example, inappropriate in the case of Challenger to risk the lives of seven astronauts and nearly one-fourth of NASA's launch assets to place in orbit a communications satellite."
, which would eventually have been the VentureStar
. During design that program increased in complexity and development cost, encountered problems and was finally cancelled.
A variant of SSTO is a hypersonic
, scramjet
-powered, airbreathing vehicle. This would be launched and landed horizontally like an airliner. It would achieve much of orbital velocity while still within the upper atmosphere. It was originally investigated by the U.S. Department of Defense
, but passenger-carrying civilian versions were planned. The official name was the Rockwell X-30
. Like the X-33, the X-30 development encountered major technical difficulties, primarily due to the system complexity and materials required for hypersonic flight, and was also canceled.
Another approach is lower-cost expendable launch vehicles. NASA currently uses commercial ELVs for unmanned launches, and could use commercial ELVs for future manned launches. This would fit with NASA's mandate to promote commercial access to and use of space.
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...
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...
has failed to achieve its promised cost and utility goals, as well as design, cost, management, and safety issues. More specifically, it has 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: by 2011, the incremental cost per flight of the Space Shuttle was estimated at $450 million, or $18,000 per kilogram to 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...
(LEO). By comparison, Russian Proton expendable launchers, still largely based on the design that dates back to 1965, are said to cost as little as $110 million, or around $5,000/kg to LEO. When all design and maintenance costs are taken into account, the final cost of the Space Shuttle program, averaged over all missions and adjusted for inflation, was estimated to come out to $1.5 billion per launch, or $60,000/kg to LEO. This should be contrasted with the originally envisioned costs of $118 per pound of payload in 1972 dollars ($1,400/kg, adjusting for inflation to 2011).
It failed in the goal of achieving reliable access to space, partly due to multi-year interruptions in launches following Shuttle failures. NASA budget pressures caused by the chronically high NASA Space Shuttle program costs have eliminated NASA manned space flight beyond low earth orbit since Apollo, and severely curtailed more productive space science using unmanned probes. NASA's promotion of and reliance on the Shuttle slowed domestic commercial expendable launch vehicle (ELV) programs until after the 1986 Challenger disaster
Space Shuttle Challenger disaster
The Space Shuttle Challenger disaster occurred on January 28, 1986, when Space Shuttle Challenger broke apart 73 seconds into its flight, leading to the deaths of its seven crew members. The spacecraft disintegrated over the Atlantic Ocean, off the coast of central Florida at 11:38 am EST...
.
Purpose of the system
The "Space Transportation System" (NASA's formal name for the overall Shuttle program) was created to transport crewmembers and payloads into low Earth orbitLow 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...
s. It would afford the opportunity to conduct science experiments on board the shuttle to be used to study the effects of space flight on humans, animals and plants. Other experiments would study how things can be manufactured in space. The shuttle would also enable astronauts to launch satellites from the shuttle and even repair satellites already out in space. The Shuttle was also intended for research into the human response to zero gravity.
The Shuttle was originally billed as a space vehicle that would be able to launch once a week and give low launch costs through amortization
Amortization
Amortization is the process of decreasing, or accounting for, an amount over a period. The word comes from Middle English amortisen to kill, alienate in mortmain, from Anglo-French amorteser, alteration of amortir, from Vulgar Latin admortire to kill, from Latin ad- + mort-, mors death.When used...
. Development costs were expected to be recouped through frequent access to space. These claims were made in an effort to obtain budgetary funding from the United States Congress
United States Congress
The United States Congress is the bicameral legislature of the federal government of the United States, consisting of the Senate and the House of Representatives. The Congress meets in the United States Capitol in Washington, D.C....
. Beginning in 1981, the space shuttle began to be used for space travel. However, by the mid-1980s the concept of flying that many shuttle missions proved unrealistic and scheduled launch expectations were reduced 50%. Following the Challenger accident in 1986, missions were halted pending safety review. This hiatus became lengthy and ultimately lasted almost three years as arguments over funding and the safety of the program continued. Eventually the military resumed the use of expendable launch vehicles instead. Missions were put on hold again after the loss of Columbia in 2003. Overall, 135 missions were launched during the 30 years after the first orbital flight of Columbia, averaging approximately one every 3 months.
Costs
Some reasons for the higher-than-expected operational costs are:- The final design differs from the original concept, causing, among other things, the shuttle orbiter to be almost 20% over its specified weight - resulting in it being unable to boost the US Air Force's payloads into polar orbitPolar orbitA polar orbit is an orbit in which a satellite passes above or nearly above both poles of the body being orbited on each revolution. It therefore has an inclination of 90 degrees to the equator...
s. - Maintenance of the thermal protection tiles is a very labor-intensive and costly process, with some 35,000 tiles needing to be inspected individually and with each tile specifically manufactured for one specific slot on the shuttle.
- The Space Shuttle Main EngineSpace Shuttle main engineThe 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...
s (SSMEs) were highly complex and maintenance-intensive, necessitating removal and extensive inspection after each flight. Before the current "Block II" engines, the turbopumpTurbopumpA turbopump is a gas turbine that comprises basically two main components: a rotodynamic pump and a driving turbine, usually both mounted on the same shaft, or sometimes geared together...
s (a primary engine component) had to be removed, disassembled, and totally overhauled after each flight. - The toxic propellants used for the OMS/RCS thrusters require special handling, during which time no other activities can be performed in areas sharing the same ventilation system. This increases turn-around time.
- The launch rate has been significantly lower than initially expected. While not reducing absolute operating costs, more launches per year gives a lower cost per launch. Some early hypothetical studies examined 55 launches per year (see above), but the maximum possible launch rate was limited to 24 per year based on manufacturing capacity of the Michoud facilityMichoud Assembly FacilityThe 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...
that constructs the external tank. Early in shuttle development, the expected launch rate was about 12 per year. Launch rates reached a peak of 9 per year in 1985 but averaged fewer thereafter. - When the decision was made on the main shuttle contractors in 1972, work was spread among companies to make the program more attractive to Congress, such as the contract for the Solid Rocket Boosters to Morton Thiokol in Utah. Over the course of the program, this raised operational costs, though the consolidation of the US aerospace industry in the 1990s means the majority of the Shuttle is now with one company: the United Space AllianceUnited Space AllianceUnited Space Alliance is a spaceflight operations company. USA is a joint venture which was established in August 1995 as a Limited Liability Company , equally owned by Boeing and Lockheed Martin. The company is headquartered in Houston, Texas and, employed approximately 8,800 people in Texas,...
, a joint venture of BoeingBoeingThe Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
and Lockheed MartinLockheed MartinLockheed Martin is an American global aerospace, defense, security, and advanced technology company with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It is headquartered in Bethesda, Maryland, in the Washington Metropolitan Area....
.
Cultural issues and problems
Some researchers have criticized a pervasive shift in NASA culture away from safety in order to ensure that launches took place in a timely fashion. Allegedly, NASA upper-level management embraced this decreased safety focus in the 1980s while some engineers remained wary. According to Vaughan, the aggressive launch schedules arose in the ReaganRonald Reagan
Ronald Wilson Reagan was the 40th President of the United States , the 33rd Governor of California and, prior to that, a radio, film and television actor....
years as a way to rehabilitate America's post-Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
prestige.
The physicist Richard Feynman
Richard Feynman
Richard Phillips Feynman was an American physicist known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics...
, who was appointed to the official inquiry on the Challenger disaster, estimated the risk to be "on the order
Order of magnitude
An order of magnitude is the class of scale or magnitude of any amount, where each class contains values of a fixed ratio to the class preceding it. In its most common usage, the amount being scaled is 10 and the scale is the exponent being applied to this amount...
of a percent" in his report, adding, "Official management, on the other hand, claims to believe the probability of failure is a thousand times less. One reason for this may be an attempt to assure the government of NASA perfection and success in order to ensure the supply of funds. The other may be that they sincerely believed it to be true, demonstrating an almost incredible lack of communication between themselves and their working engineers.
Despite Feynman's warnings, and despite the fact that Vaughan served on safety boards and committees at NASA, the subsequent press coverage has found some evidence that NASA's relative disregard for safety might persist to this day. For example, NASA discounted the risk from small foam chunk breakage at launch and assumed that the lack of damage from prior foam collisions suggested the future risk was low.
Shuttle operations
The Shuttle was originally conceived to operate somewhat like an airliner. After landing, the orbiter would be checked out and start "mating" to the rest of the system (the ET and SRBs), and be ready for launch in as little as two weeks. Instead, this turnaround process usually takes months; AtlantisSpace Shuttle Atlantis
The Space Shuttle Atlantis is a retired Space Shuttle orbiter in the Space Shuttle fleet belonging to the National Aeronautics and Space Administration , the spaceflight and space exploration agency of the United States...
set the pre-Challenger record by launching twice within 54 days, while Columbia
Space Shuttle Columbia
Space Shuttle Columbia was the first spaceworthy Space Shuttle in NASA's orbital fleet. First launched on the STS-1 mission, the first of the Space Shuttle program, it completed 27 missions before being destroyed during re-entry on February 1, 2003 near the end of its 28th, STS-107. All seven crew...
set the post-Challenger record of 88 days. Naturally, the Shuttle program's goal of returning its crew to Earth safely conflicts with the goal of a rapid and inexpensive payload launch. Furthermore, because in many cases there are no survivable abort modes
Space Shuttle abort modes
A 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...
, many pieces of hardware simply must function perfectly and so must be carefully inspected before each flight. The result is high labor cost, with around 25,000 workers in Shuttle operations and labor costs of about $1 billion per year.
Some shuttle features initially presented as important to Space Station support have proved superfluous:
- As the Russians demonstrated, capsules and unmanned supply rockets are sufficient to supply a space station.
- NASA's initial policy of using the Shuttle to launch all unmanned payloads declined in practice, and eventually was discontinued. Expendable Launch VehiclesExpendable launch systemAn expendable launch system is a launch system that uses an expendable launch vehicle to carry a payload into space. The vehicles used in expendable launch systems are designed to be used only once , and their components are not recovered for re-use after launch...
(ELVs) proved much cheaper and more flexible. - Following the Challenger disaster, use of the Shuttle to carry the powerful liquid fueledLiquid rocketA 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...
CentaurCentaur (rocket stage)Centaur is a rocket stage designed for use as the upper stage of space launch vehicles. Centaur boosts its satellite payload to geosynchronous orbit or, in the case of an interplanetary space probe, to or near to escape velocity...
upper stages planned for interplanetary probes was ruled out for Shuttle safety reasons. - The Shuttle's history of unexpected delays also makes it liable to miss narrow launch windowLaunch windowLaunch window is a term used in spaceflight to describe a time period in which a particular launch vehicle must be launched. If the rocket does not launch within the "window", it has to wait for the next window....
s. - Advances in technology over the last decade have made probes smaller and lighter. As a result, robotic probes and communications satellites can now use expendable launch vehicles, such as the DeltaDelta rocketDelta is a versatile family of expendable launch systems that has provided space launch capability in the United States since 1960. There have been more than 300 Delta rockets launched, with a 95 percent success rate. Two Delta launch systems – Delta II and Delta IV – are in active use...
and Atlas VAtlas VAtlas V is an active expendable launch system in the Atlas rocket family. Atlas V was formerly operated by Lockheed Martin, and is now operated by the Lockheed Martin-Boeing joint venture United Launch Alliance...
, which are less expensive and perceived to be more reliable than the Shuttle.
Accidents
With Challenger, an O-ring
O-ring
An O-ring, also known as a packing, or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a disc-shaped cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.The O-ring...
that should not have eroded at all did erode on earlier shuttle launches. Yet managers felt that because it had not previously eroded by more than 30%, this was not a hazard as there was "a factor of three safety margin". Morton-Thiokol
Thiokol
Thiokol is a U.S. corporation concerned initially with rubber and related chemicals, and later with rocket and missile propulsion systems...
designed and manufactured the SRBs, and during a pre-launch conference call with NASA, Roger Boisjoly
Roger Boisjoly
Roger M. Boisjoly is a mechanical engineer, fluid dynamicist and an aerodynamicist who worked for Morton Thiokol, the manufacturer of the solid rocket boosters for the Space Shuttle program...
, the Thiokol engineer most experienced with the O-rings, pleaded with management repeatedly to cancel or reschedule the launch. He raised concerns that the unusually low temperatures would stiffen the O-rings, preventing a complete seal, which was exactly what happened on the fatal flight. However, Thiokol's senior managers overruled him, dismissing his safety concerns, and allowed the launch to proceed. Challengers O-rings eroded completely through as predicted, resulting in the complete destruction of the spacecraft and the loss of all seven astronauts on board.
Columbia was destroyed because of damaged thermal protection
Space Shuttle thermal protection system
The Space Shuttle thermal protection system is the barrier that protects the Space Shuttle Orbiter during the searing heat of atmospheric reentry...
from foam debris that broke off from the external tank during ascent. The foam had not been designed or expected to break off, but had been observed in the past to do so without incident. The original shuttle operational specification said the orbiter thermal protection tiles were designed to withstand virtually no debris hits at all. Over time NASA managers gradually accepted more tile damage, similar to how O-ring damage was accepted. The Columbia Accident Investigation Board
Columbia Accident Investigation Board
The Columbia Accident Investigation Board was convened by NASA to investigate the destruction of the Space Shuttle Columbia during STS-107 upon atmospheric re-entry on February 1, 2003. In addition to determining the cause of the accident, the panel also recommended changes that should be made...
called this tendency the "normalization of deviance" — a gradual acceptance of events outside the design tolerances of the craft simply because they had not been catastrophic to date.
The subject of missing or damaged thermal tiles on the Shuttle fleet only became an issue following the loss of Columbia in 2003, as it broke up on re-entry
Atmospheric reentry
Atmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...
. In fact, Shuttles had previously come back missing as many as 20 tiles without any problem. STS-1
STS-1
STS-1 was the first orbital flight of NASA's Space Shuttle program. Space Shuttle Columbia launched on 12 April 1981, and returned to Earth on 14 April, having orbited the Earth 37 times during the 54.5-hour mission. It was the first American manned space flight since the Apollo-Soyuz Test Project...
and STS-41
STS-41
STS-41 was the eleventh mission of the Space Shuttle Discovery. The four-day mission with a primary objective to launch the Ulysses probe as part of the "International Solar Polar Mission".-Crew:-Mission parameters:*Mass:...
had all flown with missing thermal tiles from the orbital maneuvering system pods (visible to the crew). This image from the NASA archives shows many missing tiles on the STS-1 OMS pods. The problem on Columbia was that the damage was sustained from a foam strike to the reinforced carbon-carbon
Reinforced carbon-carbon
Carbon fibre-reinforced carbon is a composite material consisting of carbon fibre reinforcement in a matrix of graphite. It was developed for the nose cones of intercontinental ballistic missiles, and is most widely known as the material for the nose cone and wing leading edges of the Space Shuttle...
leading edge panel of the wing, not the heat tiles. The first Shuttle mission, STS-1, had a protruding gap filler that diverted hot gas into the right wheel well on re-entry, resulting in a buckling of the right main landing gear door.
Retrospect
While the system was developed within the original cost and time estimates given to President Richard M. Nixon in 1971, the operational costs, flight rate, payload capacity, and reliability have been much worse than anticipated. A year before STS-1STS-1
STS-1 was the first orbital flight of NASA's Space Shuttle program. Space Shuttle Columbia launched on 12 April 1981, and returned to Earth on 14 April, having orbited the Earth 37 times during the 54.5-hour mission. It was the first American manned space flight since the Apollo-Soyuz Test Project...
's April 1981 launch, The Washington Monthly
The Washington Monthly
The Washington Monthly is a bimonthly nonprofit magazine of United States politics and government that is based in Washington, D.C.The magazine's founder is Charles Peters, who started the magazine in 1969 and continues to write the "Tilting at Windmills" column in each issue. Paul Glastris, former...
accurately forecast many of the Shuttle's issues, including an overambitious launch schedule and the consequent higher-than-expected marginal cost per flight; the risks of depending on the Shuttle for all payloads, civilian and military; the lack of a survivable abort scenario if a Solid Rocket Booster were to fail; and the fragility of the Shuttle's thermal protection system.
In order to get the Shuttle approved, NASA over-promised its economies and utility. To justify its very large fixed operational program cost, NASA initially forced all domestic, internal, and Department of Defense
United States Department of Defense
The United States Department of Defense is the U.S...
payloads to the shuttle. When that proved impossible (after the Challenger disaster), NASA used the International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...
(ISS) as a justification for the shuttle. Some speculate that, had NASA avoided the Shuttle program and instead continued to use Saturn
Saturn (rocket family)
The Saturn family of American rocket boosters was developed by a team of mostly German rocket scientists led by Wernher von Braun to launch heavy payloads to Earth orbit and beyond. Originally proposed as a military satellite launcher, they were adopted as the launch vehicles for the Apollo moon...
and commercially available boosters, costs might have been lower, freeing funds for manned exploration and more unmanned space science. In particular, NASA administrator Michael D. Griffin
Michael D. Griffin
Michael Douglas Griffin is an American physicist and aerospace engineer. From April 13, 2005 to January 20, 2009 he served as Administrator of NASA, the space agency of the United States...
argued in a 2007 paper that the Saturn program, if continued, could have provided six manned launches per year — two of them to the moon — at the same cost as the Shuttle program, with an additional ability to loft infrastructure for further missions:
Some have argued that the shuttle program is flawed. Achieving a reusable vehicle with early 1970s technology forced design decisions that compromised operational reliability and safety. Reusable main engines were made a priority. This necessitated that they not burn up upon atmospheric reentry, which in turn made mounting them on the orbiter itself (the one part of the shuttle system where reuse was paramount) a seemingly logical decision. However, this had the following consequences:
- a more expensive 'clean sheet' engine design was needed, using more expensive materials, as opposed to existing and proven off-the-shelf alternatives (such as the Saturn V mains);
- increased ongoing maintenance costs related to keeping the reusable SSMEs in flying condition after each launch, costs which in total may have exceeded that of building disposable main engines for each launch;
- less absolute tonnage available to be lifted into space, since the mass of the SSMEs attached to the orbiter necessarily cut into the craft's 'payload budget' (more payload launched at any one time, by definition, reduces launch costs per pound).
A concern expressed by the 1990 Augustine Commission
Advisory Committee on the Future of the United States Space Program
The Advisory Committee on the Future of the United States Space Program was a 1990 space policy group requested by Vice President Dan Quayle, chairman of the National Space Council. The objective of the committee was to evaluate the long-term future of NASA and the United States civilian space...
was that, "the civil space program is overly dependent upon the Space Shuttle for access to space." The committee pointed out, "that it was, for example, inappropriate in the case of Challenger to risk the lives of seven astronauts and nearly one-fourth of NASA's launch assets to place in orbit a communications satellite."
Future
Designers look to more economical and reliable launch systems for the future, with lower maintenance and operational costs. One approach is Single Stage To Orbit (SSTO), which would be 100% reusable and use a single stage. NASA evaluated several concepts in the 1990s, and selected the X-33Lockheed Martin X-33
The Lockheed Martin X-33 was an unmanned, sub-scale technology demonstrator suborbital spaceplane developed in the 1990s under the U.S. government-funded Space Launch Initiative program. The X-33 was a technology demonstrator for the VentureStar orbital spaceplane, which was planned to be a...
, which would eventually have been the VentureStar
VentureStar
VentureStar was a proposed spaceplane design for a single-stage-to-orbit reusable launch system by Lockheed Martin. The program's primary goal as a United States federally funded program was to develop a reusable unmanned spaceplane for launching satellites into orbit at a fraction of the cost of...
. During design that program increased in complexity and development cost, encountered problems and was finally cancelled.
A variant of SSTO is a hypersonic
Hypersonic
In aerodynamics, a hypersonic speed is one that is highly supersonic. Since the 1970s, the term has generally been assumed to refer to speeds of Mach 5 and above...
, scramjet
Scramjet
A scramjet is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow...
-powered, airbreathing vehicle. This would be launched and landed horizontally like an airliner. It would achieve much of orbital velocity while still within the upper atmosphere. It was originally investigated by the U.S. Department of Defense
United States Department of Defense
The United States Department of Defense is the U.S...
, but passenger-carrying civilian versions were planned. The official name was the Rockwell X-30
Rockwell X-30
-See also:-References: 2. -External links:*...
. Like the X-33, the X-30 development encountered major technical difficulties, primarily due to the system complexity and materials required for hypersonic flight, and was also canceled.
Another approach is lower-cost expendable launch vehicles. NASA currently uses commercial ELVs for unmanned launches, and could use commercial ELVs for future manned launches. This would fit with NASA's mandate to promote commercial access to and use of space.
External links
- When Physics, Economics, and Reality Collide: The Challenge of Cheap Orbital Access
- Review of ELV cost-to-orbit per pound
- Space Transportation Costs: Trends in Price Per Pound to Orbit
- http://books.google.com/books?id=tE0idc3G364C&pg=PA69&dq=popular+science+von+braun&hl=en&ei=l0SKTIqiHsH58AauzcnvCw&sa=X&oi=book_result&ct=result&resnum=9&ved=0CFEQ6AEwCA#v=onepage&q=popular%20science%20von%20braun&f=falsePopular Science November 1974, "Reusable space shuttle" by Wernher von BraunWernher von BraunWernher Magnus Maximilian, Freiherr von Braun was a German rocket scientist, aerospace engineer, space architect, and one of the leading figures in the development of rocket technology in Nazi Germany during World War II and in the United States after that.A former member of the Nazi party,...
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