Space Shuttle program

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This article is about the United States Space Shuttle program. For the Shuttle itself, see Space Shuttle. For information on the Soviet space shuttle program, see the article Buran program.
Space Shuttle program
Shuttle delivers ISS P1 truss.jpg
Duration 1972 - 2011
Tasks Construction and supply of the ISS; deployment, retrieval, and repair of satellites; access to LEO
Losses Challenger, at liftoff, 1986; Columbia, at reentry, 2003
Flights 135
Organization NASA
Shuttle Patch.svg

NASA's Space Shuttle Program, officially called the Space Transportation System (STS), was the United States government's manned launch vehicle program from 1981 to 2011, with the program officially beginning in 1972. The winged Space Shuttle orbiter was launched vertically, usually carrying four to seven astronauts (though crews as small as two and as large as eight have been carried) and up to 50,000 lb (22,700 kg) of payload into low Earth orbit (LEO). When its mission was complete, the Shuttle could independently move itself out of orbit using its Orbital Maneuvering System (it oriented itself heads down and tail first, firing its OMS engines, thus slowing it down) and re-enter the Earth's atmosphere. During descent and landing the orbiter acted as a re-entry vehicle and a glider, using its Reaction Control System (RCS) and flight control surfaces to maintain altitude until it made an unpowered landing at either Kennedy Space Center or Edwards Air Force Base.

The Shuttle is the only winged manned spacecraft to have achieved orbit and land, and the only reusable manned space vehicle that has ever made multiple flights into orbit (the Russian shuttle Buran was very similar and had the same capabilities but made only one unmanned spaceflight before it was cancelled). Its missions involved carrying large payloads to various orbits (including segments to be added to the International Space Station), providing crew rotation for the International Space Station, and performing service missions. The orbiter also recovered satellites and other payloads (e.g. from the ISS) from orbit and returned them to Earth, though its use in this capacity was rare. Each vehicle was designed with a projected lifespan of 100 launches, or 10 years' operational life, though original selling points on the shuttles were over 150 launches and over a 15 year operational span with a 'launch per month' expected at the peak of the program, but that never did happen.

The program formally commenced in 1972, although the concept had been explored since the late 1960s, and was the sole focus of NASA's manned operations after the final Apollo and Skylab flights in the mid-1970s. The Shuttle was originally conceived of and presented to the public in 1972 as a 'Space Truck' which would, among other things, be used to build a United States space station in low Earth orbit during the 1980s and then be replaced by a new vehicle by the early 1990s. When the concept of the U.S. space station evolved into that of the International Space Station, which suffered from long delays and design changes before it could be completed, the service life of the Space Shuttle was extended several times until 2011 when it was finally retired — serving at least 15 years longer than it was originally designed to do. In 2004, according to the President George W. Bush's Vision for Space Exploration, use of the Space Shuttle was to be focused almost exclusively on completing assembly of the ISS, which was far behind schedule at that point.

The first experimental orbiter "Enterprise" was a high-altitude glider, launched from the back of a specially modified Boeing 747, only for initial atmospheric landing tests (ALT). Enterprise's first test flight was on February 18, 1977; leading to the launch of the first space-worthy shuttle Columbia on April 12, 1981 on STS-1. The Space Shuttle program finished with its last mission, STS-135 flown by Atlantis, in July 2011, retiring the final Shuttle in the fleet. The Space Shuttle program formally ended on August 31, 2011.[1]

Retirement of the Shuttle ended the era in which all of America's varied space activities were performed by one craft -or even one organization. Functions performed by the Shuttle for 30 years will be done by not one but many different spacecraft currently flying or in advanced development. Secret military missions are being flown by the US Air Force's "highly successful" unmanned mini-space plane, the X-37B[citation needed]. By 2012, cargo supply to the International Space Station began to be flown by privately owned commercial craft under NASA's Commercial Resupply Services by SpaceX's successfully tested and partially reusable Dragon spacecraft, followed by Orbital Sciences' Cygnus spacecraft in late 2013. Crew service to the ISS will be flown exclusively by the Russian Soyuz while NASA works on the Commercial Crew Development program. For missions beyond low Earth orbit, NASA is building the Space Launch System and the Orion spacecraft.

Conception and development[edit]

Early U.S. space shuttle concepts

Before the Apollo 11 moon landing in 1969, NASA began early studies of space shuttle designs. In 1969 President Richard Nixon formed the Space Task Group, chaired by Vice President Spiro T. Agnew. This group evaluated the shuttle studies to date, and recommended a national space strategy including building a space shuttle.[2] The goal, as presented by NASA to Congress, was to provide a much less-expensive means of access to space that would be used by NASA, the Department of Defense, and other commercial and scientific users.[3]

During early shuttle development there was great debate about the optimal shuttle design that best balanced capability, development cost and operating cost. Ultimately the current design was chosen, using a reusable winged orbiter, reusable solid rocket boosters, and an expendable external fuel tank for the orbiter's main engines.[2]

The shuttle program was formally launched on January 5, 1972, when President Nixon announced that NASA would proceed with the development of a reusable space shuttle system.[2] The stated goals of "transforming the space frontier...into familiar territory, easily accessible for human endeavor"[4] was to be achieved by launching as many as 50 missions per year, with hopes of driving down per-mission costs.[5]

The prime contractor for the program was North American Rockwell (later Rockwell International, now Boeing), the same company responsible for building the Apollo Command/Service Module. The contractor for the Space Shuttle Solid Rocket Boosters was Morton Thiokol (now part of Alliant Techsystems), for the external tank, Martin Marietta (now Lockheed Martin), and for the Space Shuttle main engines, Rocketdyne (now Pratt & Whitney Rocketdyne, part of United Technologies).[2]

The first orbiter was originally planned to be named Constitution, but a massive write-in campaign from fans of the Star Trek television series convinced the White House to change the name to Enterprise.[6] Amid great fanfare, Enterprise (designated OV-101) was rolled out on September 17, 1976, and later conducted a successful series of glide-approach and landing tests in 1977 that were the first real validation of the design.

STS-1 at liftoff. The External Tank was painted white for the first two Space Shuttle launches. From STS-3 on, it was left unpainted.

Program history[edit]

All Space Shuttle missions were launched from the Kennedy Space Center (KSC).[7] The weather criteria used for launch included, but were not limited to: precipitation, temperatures, cloud cover, lightning forecast, wind, and humidity.[8] The Shuttle was not launched under conditions where it could have been struck by lightning.

The first fully functional orbiter was Columbia (designated OV-102), built in Palmdale, California. It was delivered to Kennedy Space Center (KSC) on March 25, 1979, and was first launched on April 12, 1981—the 20th anniversary of Yuri Gagarin's space flight—with a crew of two.

Challenger (OV-099) was delivered to KSC in July 1982, Discovery (OV-103) in November 1983, Atlantis (OV-104) in April 1985 and Endeavour in May 1991. Challenger was originally built and used as a Structural Test Article (STA-099), but was converted to a complete orbiter when this was found to be less expensive than converting Enterprise from its Approach and Landing Test configuration into a spaceworthy vehicle.

On April 24, 1990, Discovery carried the Hubble Space Telescope into space during STS-31.

In the course of 135 missions flown, two orbiters (Columbia and Challenger) suffered catastrophic accidents, with the loss of all crew members, totaling 14 astronauts.

The longest Shuttle mission was STS-80 lasting 17 days, 15 hours. The final flight of the Space Shuttle program was STS-135 on July 8, 2011.

Accomplishments[edit]

Space Shuttle Endeavour docked with the International Space Station (ISS)
Astronauts Thomas D. Akers and Kathryn C. Thornton install corrective optics on the Hubble Space Telescope during STS-61.

Space Shuttle missions have included:

Budget[edit]

A drag chute is deployed by Endeavour as it completes a mission of almost 17 days in space on Runway 22 at Edwards Air Force Base in southern California. Landing occurred at 1:46 pm (EST), March 18, 1995.

Early during development of the space shuttle, NASA had estimated that the program would cost $7.45 billion ($43 billion in 2011 dollars, adjusting for inflation) in development/non-recurring costs, and $9.3M ($54M in 2011 dollars) per flight.[10] Early estimates for the cost to deliver payload to low earth orbit were as low as $118 per pound ($260/kg) of payload ($635/pound in 2011 dollars), based on marginal or incremental launch costs, and assuming a 65,000 pound (30 000 kg) payload capacity and 50 launches per year.[11][12]

The actual total cost of the shuttle program through 2011, adjusted for inflation, is $196 billion.[5] The exact breakdown into non-recurring and recurring costs is not available, but, according to NASA, the average cost to launch a Space Shuttle as of 2011 was about $450 million per mission.[13]

NASA's budget for 2005 allocated 30%, or $5 billion, to space shuttle operations;[14] this was decreased in 2006 to a request of $4.3 billion.[15] Non-launch costs account for a significant part of the program budget: for example, during fiscal years 2004 to 2006, NASA spent around $13 billion on the space shuttle program,[16] even though the fleet was grounded in the aftermath of the Columbia disaster and there were a total of three launches during this period of time. In fiscal year 2009, NASA budget allocated $2.98 billion for 5 launches to the program, including $490 million for "program integration", $1.03 billion for "flight and ground operations", and $1.46 billion for "flight hardware" (which includes maintenance of orbiters, engines, and the external tank between flights.)

Per-launch costs can be measured by dividing the total cost over the life of the program (including buildings, facilities, training, salaries, etc.) by the number of launches. With 134 missions, and the total cost of US$192 billion (in 2010 dollars), this gives approximately $1.5 billion per launch over the life of the program.[17]

Accidents[edit]

In 1986, Challenger disintegrated one minute and 13 seconds after liftoff.

In the course of 135 missions flown, two orbiters were destroyed, with loss of crew totalling 14 astronauts:

  • Challenger – lost 73 seconds after liftoff, STS-51-L, January 28, 1986
  • Columbia – lost approximately 16 minutes before its expected landing, STS-107, February 1, 2003

Close-up video footage of Challenger during its final launch on January 28, 1986 clearly show it began due to an O-ring failure on the right solid rocket booster (SRB). The hot plume of gas leaking from the failed joint caused the collapse of the external tank, which then resulted in the orbiter's disintegration due to high aerodynamic stress. The accident resulted in the loss of all seven astronauts on board. Endeavour (OV-105) was built to replace Challenger (using structural spare parts originally intended for the other orbiters) and delivered in May 1991; it was first launched a year later.

After the loss of Challenger, NASA grounded the shuttle program for over two years, making numerous safety changes recommended by the Rogers Commission Report, which included a redesign of the SRB joint that failed in the Challenger accident. Other safety changes included a new escape system for use when the orbiter was in controlled flight, improved landing gear tires and brakes, and the reintroduction of pressure suits for shuttle astronauts (these had been discontinued after STS-4; astronauts wore only coveralls and oxygen helmets from that point on until the Challenger accident). The shuttle program continued in September 1988 with the launch of Discovery on STS-26.

The shuttle program operated accident-free for seventeen years after the Challenger disaster, until Columbia broke up on re-entry, killing all seven crew members, on February 1, 2003, and was not replaced. The accident began when a piece of foam shed from the external tank struck the leading edge of the orbiter's left wing, puncturing one of the reinforced carbon-carbon (RCC) panels that covered the wing edge and protected it during re-entry. As Columbia re-entered the atmosphere, hot gas penetrated the wing and destroyed it from the inside out, causing the orbiter to lose control and disintegrate.

NASA maintains warehoused extensive catalogs of recovered pieces from the two destroyed orbiters.

After the Columbia disaster, the International Space Station operated on a skeleton crew of two for more than two years and was serviced primarily by Russian spacecraft. While the "Return to Flight" mission STS-114 in 2005 was successful, a similar piece of foam from a different portion of the tank was shed. Although the debris did not strike Discovery, the program was grounded once again for this reason.

The second "Return to Flight" mission, STS-121 launched on July 4, 2006, at 14:37 (EDT). Two previous launches were scrubbed because of lingering thunderstorms and high winds around the launch pad, and the launch took place despite objections from its chief engineer and safety head. A five-inch (13 cm) crack in the foam insulation of the external tank gave cause for concern; however, the Mission Management Team gave the go for launch.[18] This mission increased the ISS crew to three. Discovery touched down successfully on July 17, 2006 at 09:14 (EDT) on Runway 15 at Kennedy Space Center.

Following the success of STS-121, all subsequent missions were completed without major foam problems, and the construction of ISS was completed (during the STS-118 mission in August 2007, the orbiter was again struck by a foam fragment on liftoff, but this damage was minimal compared to the damage sustained by Columbia).

The Columbia Accident Investigation Board, in its report, noted the reduced risk to the crew when a shuttle flew to the International Space Station (ISS), as the station could be used as a safe haven for the crew awaiting rescue in the event that damage to the orbiter on ascent made it unsafe for re-entry. The board recommended that for the remaining flights, the shuttle always orbit with the station. Prior to STS-114, NASA Administrator Sean O'Keefe declared that all future flights of the shuttle would go to the ISS, precluding the possibility of executing the final Hubble Space Telescope servicing mission which had been scheduled before the Columbia accident, despite the fact that millions of dollars worth of upgrade equipment for Hubble were ready and waiting in NASA warehouses. Many dissenters, including astronauts[who?], asked NASA management to reconsider allowing the mission, but initially the director stood firm. On October 31, 2006, NASA announced approval of the launch of Atlantis for the fifth and final shuttle servicing mission to the Hubble Space Telescope, scheduled for August 28, 2008. However SM4/STS-125 eventually launched in May 2009.

Retirement[edit]

Atlantis begins the last mission of the Space Shuttle program

The Space Shuttle program was extended several times beyond its originally envisioned 15-year life span because of the delays in building the United States space station in low Earth orbit — a project which eventually evolved into the International Space Station. It was formally scheduled for mandatory retirement in 2010 in accord with the directives President George W. Bush issued on January 14, 2004 in his Vision for Space Exploration.[19]

A $2.5 billion spending provision allowing NASA to fly the Space Shuttle beyond its then-scheduled retirement in 2010 passed the Congress in April 2009, although neither NASA nor the White House requested the one-year extension.[20]

The final Space Shuttle launch was that of Atlantis on July 8, 2011.

Final status[edit]

Out of the five fully functional shuttle orbiters built, three remain. Enterprise, which was used for atmospheric test flights but not for orbital flight, had many parts taken out for use on the other orbiters. It was later visually restored and was on display at the National Air and Space Museum's Steven F. Udvar-Hazy Center until April 19, 2012. Enterprise was moved to New York City in April 2012 to be displayed at the Intrepid Sea, Air & Space Museum, whose Space Shuttle Pavilion opened on July 19, 2012. Discovery replaced Enterprise at the National Air and Space Museum's Steven F. Udvar-Hazy Center. Atlantis formed part of the Space Shuttle Exhibit at the Kennedy Space Center visitor complex and has been on display there since June 29, 2013 following its refurbishment.[21]

On October 14, 2012, Endeavour completed an unprecedented 12 mi (19 km) drive on city streets from Los Angeles International Airport to the California Science Center, where it has been on display in a temporary hangar since late 2012. The transport from the airport took two days and required major street closures, the removal of over 400 city trees, and extensive work to raise power lines, level the street, and temporarily remove street signs, lamp posts, and other obstacles. Hundreds of volunteers, and fire and police personnel, helped with the transport. Large crowds of spectators waited on the streets to see the shuttle as it passed through the city. Endeavour will be displayed permanently beginning in 2017 at the Samuel Oschin Air and Space Center (an addition to the California Science Center currently under construction), where it will be mounted in the vertical position complete with solid rocket boosters and an external tank.[22]

Successors[edit]

The Dragon spacecraft, one of the Space Shuttle's several successors, is seen here on its way to deliver cargo to the ISS

According to the 2004 Vision for Space Exploration, the next manned NASA program was to be Project Constellation with its Ares I and Ares V launch vehicles and the Orion Spacecraft; however, the Constellation program was never fully funded, and in early 2010 the Obama administration asked Congress to instead endorse a plan with heavy reliance on the private sector for delivering cargo and crew to LEO.

The Commercial Orbital Transportation Services (COTS) program began in 2006 with the purpose of creating commercially operated unmanned cargo vehicles to service the ISS.[23] The first of these vehicles, SpaceX's Dragon, became operational in 2012, and the second, Orbital Sciences' Cygnus did so in 2014.[24]

The Commercial Crew Development (CCDev) program was initiated in 2010 with the purpose of creating commercially operated manned spacecraft capable of delivering at least four crew members to the ISS, staying docked for 180 days and then returning them back to Earth.[25] These spacecraft, like the SpaceX Dragon V2 Dragon (spacecraft)#Dragon V2 and Sierra Nevada Corporation's Dreamchaser Dream Chaser are expected to become operational around 2017.[26]

Although the Constellation program was canceled, it has been replaced with a very similar beyond low Earth orbit program. The Orion spacecraft has been left virtually unchanged from its previous design. The planned Ares V rocket has been replaced with the smaller Space Launch System (SLS), which is planned to launch both Orion and other necessary hardware.[27] Exploration Flight Test-1 (EFT-1), an unmanned test flight of the Orion spacecraft, is planned to be launched in 2014 on a Delta IV Heavy rocket.[28] Exploration Mission-1 (EM-1) is the unmanned initial launch of the SLS, which is planned for 2017.[28] Exploration Mission-2 (EM-2) is the first manned flight of Orion and SLS and is scheduled for 2019.[28] EM-2 is a 10-14-day mission planned to place a crew of four into Lunar orbit. As of September 2013, the destination for EM-3 and immediate destination focus for this new program is still in-flux.[29]

Assets and transition plan[edit]

The Space Shuttle program occupied over 654 facilities, used over 1.2 million line items of equipment, and employed over 5,000 people. The total value of equipment was over $12 billion. Shuttle-related facilities represented over a quarter of NASA's inventory. There were over 1,200 active suppliers to the program throughout the United States. NASA's transition plan had the program operating through 2010 with a transition and retirement phase lasting through 2015. During this time, the Ares I and Orion as well as the Altair Lunar Lander were to be under development,[30] although these programs have since been canceled.

Criticism[edit]

The Space Shuttle program has been criticized for failing to achieve its promised cost and utility goals, as well as design, cost, management, and safety issues.[31] Others have argued that the Shuttle program was a step backwards from the Apollo Program, which, while extremely dangerous, accomplished far more scientific and space exploration endeavors than the Shuttle ever could.

After both the Challenger disaster and the Columbia disaster, high profile boards convened to investigate the accidents with both committees returning praise and serious critiques to the program and NASA management. Some of the most famous of the criticisms, most of management, came from Nobel Prize winner Richard Feynman, in his report that followed his appointment to the commission responsible for investigating the Challenger disaster.[32]

Other STS program vehicles[edit]

Crawler-transporter No.2 ("Franz") in a December 2004 road test after track shoe replacement
Atlantis being prepared to be mated to the Shuttle Carrier Aircraft using the Mate-Demate Device following STS-44.

Many other vehicles were used in support of the Space Shuttle program, mainly terrestrial transportation vehicles.

  • The Crawler-Transporter carried the Mobile Launcher Platform and the space shuttle from the Vehicle Assembly Building (VAB) to Launch Complex 39.
  • The Shuttle Carrier Aircraft (SCA) were two modified Boeing 747s. Either could fly an orbiter from alternative landing sites back to the Kennedy Space Center.
  • A 36-wheeled transport trailer, the Orbiter Transfer System, originally built for the U.S. Air Force's launch facility at Vandenberg Air Force Base in California (since then converted for Delta IV rockets) would transport the orbiter from the landing facility to the launch pad, which allowed both "stacking" and launch without utilizing a separate VAB-style building and crawler-transporter roadway. Prior to the closing of the Vandenberg facility, orbiters were transported from the OPF to the VAB on their undercarriages, only to be raised when the orbiter was being lifted for attachment to the SRB/ET stack. The trailer allowed the transportation of the orbiter from the OPF to either the SCA "Mate-Demate" stand or the VAB without placing any additional stress on the undercarriage.
  • The Crew Transport Vehicle (CTV), a modified airport jet bridge, was used to assist astronauts to egress from the orbiter after landing. Upon entering the CTV, astronauts could take off their launch and re-entry suits then proceed to chairs and beds for medical checks before being transported back to the crew quarters in the Operations and Checkout Building.
  • The Astrovan was used to transport astronauts from the crew quarters in the Operations and Checkout Building to the launch pad on launch day. It was also used to transport astronauts back again from the Crew Transport Vehicle at the Shuttle Landing Facility.

See also[edit]

References[edit]

 This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.

  1. ^ "Breaking News | Shannon to review options for deep space exploration". Spaceflight Now. 2011-08-29. Retrieved 2012-05-17. 
  2. ^ a b c d Hepplewhite, T.A. The Space Shuttle Decision: NASA's Search for a Reusable Space Vehicle. Washington, DC: National Aeronautics and Space Administration, 1999.
  3. ^ General Accounting Office. Cost Benefit Analysis Used in Support of the Space Shuttle Program. Washington, DC: General Accounting Office, 1972.
  4. ^ Rebecca Onion (November 15, 2012). "I Say "Space Shuttle," You Say "Space Clipper"". Slate (magazine). The Slate Group. Retrieved November 25, 2012. 
  5. ^ a b Borenstein, Seth (July 5, 2011). "AP Science Writer". Boston Globe. Associated Press. Retrieved July 5, 2011. 
  6. ^ Brooks, Dawn The Names of the Space Shuttle Orbiters. Washington, DC: National Aeronautics and Space Administration. Retrieved July 26, 2006.
  7. ^ Civillian and military circumpolar space shuttle missions were planned for Vandenberg AFB in California. The use of Vandenberg AFB for space shuttle missions was cancelled after space shuttle Challenger exploded on January 28, 1986
  8. ^ "SPACE SHUTTLE WEATHER LAUNCH COMMIT CRITERIA AND KSC END OF MISSION WEATHER LANDING CRITERIA". KSC Release No. 39-99. NASA Kennedy Space Center. Retrieved July 6, 2009. 
  9. ^ a b c d e "Spacelab joined diverse scientists and disciplines on 28 Shuttle missions". NASA. March 15, 1999. Retrieved February 11, 2011. 
  10. ^ Bulletin of the Atomic Scientists. February 1973. p. 39. 
  11. ^ NASA (2003) Columbia Accident Investigation Board Public Hearing Transcript
  12. ^ Comptroller General (1972). "Report to the Congress: Cost-Benefit Analylsis Used in Support of the Space Shuttle Program" (PDF). United States General Accounting Office. Retrieved November 25, 2008. 
  13. ^ NASA (2011). "How much does it cost to launch a Space Shuttle?". NASA. Retrieved June 28, 2011. 
  14. ^ David, Leonard (February 11, 2005). "Total Tally of Shuttle Fleet Costs Exceed Initial Estimates". Space.com. Retrieved August 6, 2006. 
  15. ^ Berger, Brian (February 7, 2006). "NASA 2006 Budget Presented: Hubble, Nuclear Initiative Suffer". Space.com. Retrieved August 6, 2006. 
  16. ^ "NASA Budget Information". 
  17. ^ Pielke Jr., Roger; Radford Byerly (7 April 2011). Shuttle programme lifetime cost 472 (7341). Nature. Bibcode:2011Natur.472...38P. doi:10.1038/472038d. Retrieved July 14, 2011. 
  18. ^ Chien, Philip (June 27, 2006) "NASA wants shuttle to fly despite safety misgivings." The Washington Times
  19. ^ President George W. Bush (Attributed) (2004). "President Bush Offers New Vision For NASA". nasa.gov. Retrieved January 14, 2004. 
  20. ^ Mark, Roy "Mandatory Shuttle Retirement Temporarily Postponed" (April 30, 2009) Green IT, e-week.com
  21. ^ Space Shuttle Atlantis Exhibit Opens with Support from Souvenirs - Yahoo! News
  22. ^ "Space Shuttle Endeavour homepage". 
  23. ^ "NASA Selects Crew and Cargo Transportation to Orbit Partners" (Press release). NASA. 2006-08-18. Retrieved 2006-11-21. 
  24. ^ Bergin, Chris (2011-10-06). "ISS partners prepare to welcome SpaceX and Orbital in a busy 2012". NASASpaceFlight.com (Not affiliated with NASA). Retrieved 13 December 2011. 
  25. ^ Berger, Brian (2011-02-01). "Biggest CCDev Award Goes to Sierra Nevada". Imaginova Corp. Retrieved 13 December 2011. 
  26. ^ "Congress wary of fully funding commercial crew". Spaceflightnow. 2012-04-24. Retrieved 28 April 2012. 
  27. ^ "NASA Announces Design for New Deep Space Exploration System". NASA. 2011-09-14. Retrieved 28 April 2012. 
  28. ^ a b c Bergin, Chris (2012-02-23). "Acronyms to Ascent – SLS managers create development milestone roadmap". NASA. Retrieved 29 April 2012. 
  29. ^ Bergin, Chris (2012-03-26). "NASA Advisory Council: Select a Human Exploration Destination ASAP". NasaSpaceflight (not affiliated with NASA). Retrieved 28 April 2012. 
  30. ^ Olson, John; Joel Kearns (August 2008). "NASA Transition Management Plan". JICB-001. National Aeronautics and Space Administration. 
  31. ^ A Rocket to Nowhere, Maciej Cegłowski, Idle Words, March 8, 2005.
  32. ^ [1], additional text.

Further reading[edit]

External links[edit]