Space Shuttle program

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Space Shuttle program
Shuttle Patch.svg
CountryUnited States
Organization NASA
PurposeCrewed orbital flight
Program history
CostUS$196 billion (2011)
First flight
  • ALT-12
  • August 12, 1977 (1977-08-12)
First crewed flight
  • STS-1
  • April 12, 1981 (1981-04-12)
Last flight
  • STS-135
  • July 21, 2011 (2011-07-21)
Failures1 (STS-51-L)
Partial failures1 (STS-107)
Launch site(s)
Vehicle information
Crewed vehicle(s) Space Shuttle orbiter
Launch vehicle(s) Space Shuttle

The Space Shuttle program was the fourth human spaceflight program carried out by the National Aeronautics and Space Administration (NASA), which accomplished routine transportation for Earth-to-orbit crew and cargo from 1981 to 2011. Its official name, Space Transportation System (STS), was taken from a 1969 plan for a system of reusable spacecraft of which it was the only item funded for development. [1]


The Space Shuttle—composed of an orbiter launched with two reusable solid rocket boosters and a disposable external fuel tank—carried up to eight astronauts and up to 50,000 lb (23,000 kg) of payload into low Earth orbit (LEO). When its mission was complete, the orbiter would reenter the Earth's atmosphere and land like a glider at either the Kennedy Space Center or Edwards Air Force Base.

The Shuttle is the only winged crewed spacecraft to have achieved orbit and landing, and the only reusable crewed space vehicle that has ever made multiple flights into orbit. [lower-alpha 1] Its missions involved carrying large payloads to various orbits including the International Space Station (ISS), providing crew rotation for the space station, and performing service missions on the Hubble Space Telescope. 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. Original selling points on the shuttles were over 150 launches over a 15-year operational span with a 'launch per month' expected at the peak of the program, but extensive delays in the development of the International Space Station [2] never created such a peak demand for frequent flights.


Various shuttle concepts had been explored since the late 1960s. The program formally commenced in 1972, becoming the sole focus of NASA's human spaceflight operations after the Apollo, Skylab, and Apollo-Soyuz programs in 1975. 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. The stalled plans for a U.S. space station evolved into the International Space Station and were formally initiated in 1983 by President Ronald Reagan, but the ISS suffered from long delays, design changes and cost over-runs [2] and forced the service life of the Space Shuttle to be extended several times until 2011 when it was finally retired—serving twice as long than it was originally designed to do. In 2004, according to 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, only five years after the Shuttle program was formally initiated; 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. [3]

Conception and development

Early U.S. space shuttle concepts Space Shuttle concepts.jpg
Early U.S. space shuttle concepts

Before the Apollo 11 Moon landing in 1969, NASA began studies of Space Shuttle designs as early as October 1968. The early studies were denoted "Phase A", and in June 1970, "Phase B", which were more detailed and specific. The primary intended use of the Space Shuttle was supporting the future space station, ferrying a minimum crew of four and about 20,000 pounds (9,100 kg) of cargo, and able to be rapidly turned around for future flights.

Two designs emerged as front-runners. One was designed by engineers at the Manned Spaceflight Center, and championed especially by George Mueller. This was a two-stage system with delta-winged spacecraft, and generally complex. An attempt to re-simplify was made in the form of the DC-3, designed by Maxime Faget, who had designed the Mercury capsule among other vehicles. Numerous offerings from a variety of commercial companies were also offered, but generally fell by the wayside as each NASA lab pushed for its own version.

All of this was taking place in the midst of other NASA teams proposing a wide variety of post-Apollo missions, a number of which would cost as much as Apollo or more[ citation needed ]. As each of these projects fought for funding, the NASA budget was at the same time being severely constrained. Three were eventually presented to Vice President Agnew in 1969. The shuttle project rose to the top, largely due to tireless campaigning by its supporters[ citation needed ]. By 1970 the shuttle had been selected as the one major project for the short-term post-Apollo time frame.

When funding for the program came into question, there were concerns that the project might be cancelled. This led to an effort to interest the US Air Force in using the shuttle for their missions as well. The Air Force was mildly interested, but demanded a much larger vehicle, far larger than the original concepts. To lower the development costs of the resulting designs, boosters were added, a throw-away fuel tank was adopted, and many other changes made that greatly lowered the reusability and greatly added to vehicle and operational costs. With the Air Force's assistance, the system emerged in its operational form.

Program history

President Nixon (right) with NASA Administrator Fletcher in January 1972, three months before Congress approved funding for the Shuttle program President Nixon and James Fletcher Discuss the Space Shuttle - GPN-2002-000109.jpg
President Nixon (right) with NASA Administrator Fletcher in January 1972, three months before Congress approved funding for the Shuttle program
Shuttle approach and landing test crews, 1976 Space Shuttle Approach and Landing Tests crews.jpg
Shuttle approach and landing test crews, 1976

All Space Shuttle missions were launched from the Kennedy Space Center (KSC) in Florida. Some civilian and military circumpolar space shuttle missions were planned for Vandenberg AFB in California. However, the use of Vandenberg AFB for space shuttle missions was canceled after the Challenger disaster in 1986. The weather criteria used for launch included, but were not limited to: precipitation, temperatures, cloud cover, lightning forecast, wind, and humidity. [4] 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 accidents led to national level inquiries and detailed analysis of why the accidents occurred. [5] There was a significant pause where changes were made before the Shuttles returned to flight. [5] The Columbia disaster occurred in 2003, but STS took more than a year off before returning to flight in June 2005 with the STS-114 mission. [5] The previously mentioned break was between January 1986 (when the Challenger disaster occurred) and 32 months later when STS-26 was launched on September 29, 1988. [6]

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.

Since the Shuttle's retirement in 2011, many of its original duties are performed by an assortment of government and private vessels. The European ATV Automated Transfer Vehicle supplied the ISS between 2008 and 2015. Classified military missions are being flown by the US Air Force's uncrewed space plane, the X-37B.[ citation needed ] By 2012, cargo to the International Space Station was already being delivered commercially under NASA's Commercial Resupply Services by SpaceX's partially reusable Dragon spacecraft, followed by Orbital Sciences' Cygnus spacecraft in late 2013. Crew service to the ISS is currently provided by the Russian Soyuz while work on the Commercial Crew Development program proceeds; the first crewed flight of this was on May 30, 2020, on the SpaceX Falcon 9 with Dragon 2 crew capsule. [7] For missions beyond low Earth orbit, NASA is building the Space Launch System and the Orion spacecraft, part of the Artemis program.

NASA Administrator address the crowd at the Spacelab arrival ceremony in February 1982. On the podium with him is then-Vice President George Bush, the director general of European Space Agency (ESA), Eric Quistgaard, and director of Kennedy Space Center Richard G. Smith Spacelab Arrival Ceremony at Kennedy Space Center - GPN-2002-000088.jpg
NASA Administrator address the crowd at the Spacelab arrival ceremony in February 1982. On the podium with him is then-Vice President George Bush, the director general of European Space Agency (ESA), Eric Quistgaard, and director of Kennedy Space Center Richard G. Smith
"President Ronald Reagan chats with NASA astronauts Henry Hartsfield and Thomas Mattingly on the runway as first lady Nancy Reagan scans the nose of Space Shuttle Columbia following its Independence Day landing at Edwards Air Force Base on July 4, 1982." Ronald and Nancy Reagan NASA 1982.jpg
"President Ronald Reagan chats with NASA astronauts Henry Hartsfield and Thomas Mattingly on the runway as first lady Nancy Reagan scans the nose of Space Shuttle Columbia following its Independence Day landing at Edwards Air Force Base on July 4, 1982."
STS-3 lands in March 1982 STS-3 landing.jpg
STS-3 lands in March 1982


Galileo floating free in space after release from Space Shuttle Atlantis, 1989 1989 s34 Galileo Deploy 5.jpg
Galileo floating free in space after release from Space Shuttle Atlantis, 1989
Space Shuttle Endeavour docked with the International Space Station (ISS), 2011 Endeavour docked to ISS.jpg
Space Shuttle Endeavour docked with the International Space Station (ISS), 2011

Space Shuttle missions have included:


Space Shuttle Atlantis takes flight on the STS-27 mission on December 2, 1988. The Shuttle took about 8.5 minutes to accelerate to a speed of over 27,000 km/h (17000 mph) and achieve orbit. Atlantis taking off on STS-27.jpg
Space Shuttle Atlantis takes flight on the STS-27 mission on December 2, 1988. The Shuttle took about 8.5 minutes to accelerate to a speed of over 27,000 km/h (17000 mph) and achieve orbit.
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. 950318 STS67 Endeavour landing.jpg
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/lb or $1,400/kg 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] A more realistic projection of 12 flights per year for the 15-year service life combined with the initial development costs would have resulted in a total cost projection for the program of roughly $54 billion (in 2011 dollars).

The total cost of the actual 30-year service life of the Shuttle program through 2011, adjusted for inflation, was $196 billion. [13] 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. [14]

NASA's budget for 2005 allocated 30%, or $5 billion, to space shuttle operations; [15] this was decreased in 2006 to a request of $4.3 billion. [16] 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, [17] 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 135 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 Shuttle program. [18] A 2017 study found that carrying one kilogram of cargo to the ISS on the Shuttle cost $272,000 in 2017 dollars, twice the cost of Cygnus and three times that of Dragon. [19]

NASA used a management philosophy known as success-oriented management during the Space Shuttle program which was described by historian Alex Roland in the aftermath of the Columbia disaster as "hoping for the best". [20] Success-oriented management has since been studied by several analysts in the area. [21] [22] [23]


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

There was also one abort-to-orbit and some fatal accidents on the ground during launch preparations.

STS-51-L (Challenger, 1986)

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

Close-up video footage of Challenger during its final launch on January 28, 1986 clearly shows that the problems 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 Space 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 accidents did not just affect the technical design of the orbiter, but also NASA. [6] Quoting some recommendations made by the post-Challenger Rogers commission: [6]

Recommendation I – The faulty Solid Rocket Motor joint and seal must be changed. This could be a new design eliminating the joint or a redesign of the current joint and seal. ... the Administrator of NASA should request the National Research Council to form an independent Solid Rocket Motor design oversight committee to implement the Commission's design recommendations and oversee the design effort.
Recommendation II – The Shuttle Program Structure should be reviewed. ... NASA should encourage the transition of qualified astronauts into agency management Positions.
Recommendation III – NASA and the primary shuttle contractors should review all Criticality 1, 1R, 2, and 2R items and hazard analyses.
Recommendation IV – NASA should establish an Office of Safety, Reliability and Quality Assurance to be headed by an Associate Administrator, reporting directly to the NASA Administrator.
Recommendation VI – NASA must take actions to improve landing safety. The tire, brake and nosewheel system must be improved.
Recommendation VII – Make all efforts to provide a crew escape system for use during controlled gliding flight.
Recommendation VIII – The nation's reliance on the shuttle as its principal space launch capability created a relentless pressure on NASA to increase the flight rate ... NASA must establish a flight rate that is consistent with its resources.

STS-107 (Columbia, 2003)

Video of Columbia's final moments, filmed by the crew.
Space Shuttle Discovery as it approaches the International Space Station during STS-114 on July 28, 2005. This was the Shuttle's "return to flight" mission after the Columbia disaster Thermal protection system inspections from ISS - Shuttle nose.jpg
Space Shuttle Discovery as it approaches the International Space Station during STS-114 on July 28, 2005. This was the Shuttle's "return to flight" mission after the Columbia disaster

The Shuttle program operated accident-free for seventeen years after the Challenger disaster, until Columbia broke up on reentry, killing all seven crew members, on February 1, 2003. The ultimate cause of the accident was a piece of foam separating from the external tank moments after liftoff and striking 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 reentry. As Columbia reentered the atmosphere at the end of an otherwise normal mission, hot gas penetrated the wing and destroyed it from the inside out, causing the orbiter to lose control and disintegrate.

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. [24] 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 reentry. 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 Space 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.

One impact of Columbia was that future crewed launch vehicles, namely the Ares I, had a special emphasis on crew safety compared to other considerations. [25]

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


Atlantis after its, and the program's, final landing Atlantis welcome home ceremony outside the OPF July 22.png
Atlantis after its, and the program’s, final landing

The Space Shuttle retirement was announced in January 2004. [26] :III-347 President George W. Bush announced his Vision for Space Exploration, which called for the retirement of the Space Shuttle once it completed construction of the ISS. [27] [28] To ensure the ISS was properly assembled, the contributing partners determined the need for 16 remaining assembly missions in March 2006. [26] :III-349 One additional Hubble Space Telescope servicing mission was approved in October 2006. [26] :III-352 Originally, STS-134 was to be the final Space Shuttle mission. However, the Columbia disaster resulted in additional orbiters being prepared for launch on need in the event of a rescue mission. As Atlantis was prepared for the final launch-on-need mission, the decision was made in September 2010 that it would fly as STS-135 with a four-person crew that could remain at the ISS in the event of an emergency. [26] :III-355 STS-135 launched on July 8, 2011, and landed at the KSC on July 21, 2011, at 5:57 a.m. EDT (09:57 UTC). [26] :III-398 From then until the launch of Crew Dragon Demo-2 on May 30, 2020, the US launched its astronauts aboard Russian Soyuz spacecraft. [29]

Following each orbiter's final flight, it was processed to make it safe for display. The OMS and RCS systems used presented the primary dangers due to their toxic hypergolic propellant, and most of their components were permanently removed to prevent any dangerous outgassing. [26] :III-443Atlantis is on display at the Kennedy Space Center Visitor Complex, [26] :III-456Discovery is at the Udvar-Hazy Center, [26] :III-451Endeavour is on display at the California Science Center, [26] :III-457 and Enterprise is displayed at the Intrepid Sea-Air-Space Museum. [26] :III-464 Components from the orbiters were transferred to the US Air Force, ISS program, and Russian and Canadian governments. The engines were removed to be used on the Space Launch System, and spare RS-25 nozzles were attached for display purposes. [26] :III-445


Space Shuttle Discovery at the Udvar Hazy museum Space Shuttle Discovery @ Udvar Hazy.png
Space Shuttle Discovery at the Udvar Hazy museum

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. [30]

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, along with the last flight-qualified external tank (ET-94), is currently on display at the California Science Center's Samuel Oschin Pavilion (in a horizontal orientation) until the completion of the Samuel Oschin Air and Space Center (a planned addition to the California Science Center). Once moved, it will be permanently displayed in launch configuration, complete with genuine solid rocket boosters and external tank. [31]

Passenger modules

External image
Searchtool.svg Rockwell 74 Passenger Module
© Rockwell— host
Spacehab module Spacehab S107e05359.jpg
Spacehab module
Ten people inside Spacelab Module in the Shuttle bay in June 1995, celebrating the docking of the Space Shuttle and Mir. Crewmembers of STS-71, Mir-18 and Mir-19 Pose for Inflight Picture - GPN-2002-000061 rotated.jpg
Ten people inside Spacelab Module in the Shuttle bay in June 1995, celebrating the docking of the Space Shuttle and Mir.

One area of Space Shuttle applications is an expanded crew. [32] Crews of up to eight have been flown in the Orbiter, but it could have held at least a crew of ten. [32] Various proposals for filling the payload bay with additional passengers were also made as early as 1979. [33] One proposal by Rockwell provided seating for 74 passengers in the Orbiter payload bay, with support for three days in Earth orbit. [33] With a smaller 64 seat orbiter, costs for the late 1980s would be around US$1.5 million per seat per launch. [34] The Rockwell passenger module had two decks, four seats across on top and two on the bottom, including a 25-inch (63.5 cm) wide aisle and extra storage space. [34]

Another design was Space Habitation Design Associates 1983 proposal for 72 passengers in the Space Shuttle Payload bay. [34] 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. [34] 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. [34]

There were some efforts to analyze commercial operation of STS. [35] Using the NASA figure for average cost to launch a Space Shuttle as of 2011 at about $450 million per mission, [14] a cost per seat for a 74 [36] [37] seat module envisioned by Rockwell came to less than $6 million, not including the regular crew. Some passenger modules used hardware similar to existing equipment, such as the tunnel, [37] which was also needed for Spacehab and Spacelab


During the three decades of operation, various follow-on and replacements for the STS Space Shuttle were partially developed but not finished. [38]

Examples of possible future space vehicles to supplement or supplant STS: [38]

One effort in the direction of space transportation was the Reusable Launch Vehicle (RLV) program, initiated in 1994 by NASA. [40] This led to work on the X-33 and X-34 vehicles. [40] NASA spent about US$1 billion on developing the X-33 hoping for it be in operation by 2005. [40] Another program around the turn of the millennium was the Space Launch Initiative, which was a next generation launch initiative. [41]

The Space Launch Initiative program was started in 2001, and in late 2002 it was evolved into two programs, the Orbital Space Plane Program and the Next Generation Launch Technology program. [41] OSP was oriented towards provided access to the International Space Station. [41]

Other vehicles that would have taken over some of the Shuttles responsibilities were the HL-20 Personnel Launch System or the NASA X-38 of the Crew Return Vehicle program, which were primarily for getting people down from ISS. The X-38 was cancelled in 2002, [42] and the HL-20 was cancelled in 1993. [43] Several other programs in this existed such as the Station Crew Return Alternative Module (SCRAM) and Assured Crew Return Vehicle (ACRV) [44]

According to the 2004 Vision for Space Exploration, the next human NASA program was to be Constellation program 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 uncrewed cargo vehicles to service the ISS. [45] The first of these vehicles, SpaceX Dragon, became operational in 2012, and the second, Orbital Sciences's Cygnus did so in 2014. [46]

The Commercial Crew Development (CCDev) program was initiated in 2010 with the purpose of creating commercially operated crewed spacecraft capable of delivering at least four crew members to the ISS, staying docked for 180 days and then returning them back to Earth. [47] These spacecraft, like SpaceX's Dragon 2 and Boeing CST-100 Starliner were expected to become operational around 2020. [48] On the Crew Dragon Demo-2 mission, SpaceX's Dragon 2 sent astronauts to the ISS, restoring America's human launch capability. The first operational SpaceX mission launched on November 15, 2020 at 7:27:17p.m. ET, carrying four astronauts to the ISS.

Although the Constellation program was canceled, it has been replaced with a very similar Artemis 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. [49] Exploration Flight Test-1 (EFT-1), an uncrewed test flight of the Orion spacecraft, launched on December 5, 2014 on a Delta IV Heavy rocket. [50]

Artemis 1 is planned to be the first flight of the SLS and will be launched as a test of the completed Orion and SLS system. [51] During the mission, an uncrewed Orion capsule will spend 10 days in a 60,000-kilometer (32,000-nautical-mile) distant retrograde orbit around the Moon before returning to Earth. [52] Artemis 2, the first crewed mission of the program, will launch four astronauts in 2022 [53] on a free-return flyby of the Moon at a distance of 8,900 kilometers (4,800 nautical miles). [54] [55] [56] After Artemis 2, the Power and Propulsion Element of the Lunar Gateway and three components of an expendable lunar lander are planned to be delivered on multiple launches from commercial launch service providers. [57] Artemis 3 is planned to launch in 2024 aboard a SLS Block 1B rocket and will use the minimalist Gateway and expendable lander to achieve the first crewed lunar landing of the program. The flight is planned to touch down on the lunar south pole region, with two astronauts staying there for about one week. [57] [58] [59] [60] [61]

Assets and transition plan

Atlantis about 30 minutes after final touchdown STS-135 30 mins after touchdown2.png
Atlantis about 30 minutes after final touchdown

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, [62] although these programs have since been canceled.

In the 2010s, two major programs for human spaceflight are Commercial Crew Program and the Artemis program. Kennedy Space Center Launch Complex 39A is, for example, used to launch a Falcon Heavy rocket.


The partial reusability of the Space Shuttle was one of the primary design requirements during its initial development. [63] :164 The technical decisions that dictated the orbiter's return and reuse reduced the per-launch payload capabilities with the intention of lowering the per-launch costs and resulting in a high-launch rate. The actual costs of a Space Shuttle launch were higher than initially predicted, and the Space Shuttle did not fly the intended 24 missions per year as initially predicted by NASA. [64] [26] :III–489–490 The Space Shuttle was originally intended as a launch vehicle to deploy satellites, which it was primarily used for on the missions prior to the Challenger disaster. NASA's pricing, which was below cost, was lower than expendable launch vehicles; the intention was that the high volume of Space Shuttle missions would compensate for early financial losses. The improvement of expendable launch vehicles and the transition away from commercial payload on the Space Shuttle resulted in expendable launch vehicles becoming the primary deployment option for satellites. [26] :III–109–112

The fatal Challenger and Columbia disasters demonstrated the safety risks of the Space Shuttle that could result in the loss of the crew. The spaceplane design of the orbiter limited the abort options, as the abort scenarios required the controlled flight of the orbiter to a runway or to allow the crew to egress individually, rather than the abort escape options on the Apollo and Soyuz space capsules. [65] Early safety analyses advertised by NASA engineers and management predicted the chance of a catastrophic failure resulting in the death of the crew as ranging from 1 in 100 launches to as rare as 1 in 100,000. [66] [67] Following the loss of two Space Shuttle missions, the risks for the initial missions were reevaluated, and the chance of a catastrophic loss of the vehicle and crew was found to be as high as 1 in 9. [68] NASA management was criticized afterwards for accepting increased risk to the crew in exchange for higher mission rates. Both the Challenger and Columbia reports explained that NASA culture had failed to keep the crew safe by not objectively evaluating the potential risks of the missions. [67] [69] :195–203

Support vehicles

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

Crawler-transporter No.2 ("Franz") in a December 2004 road test after track shoe replacement Crawler-Transporter.jpg
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. Shuttle mate demate facility.jpg
Atlantis being prepared to be mated to the Shuttle Carrier Aircraft using the Mate-Demate Device following STS-44.
MV Freedom Star was a NASA recovery ship for the Space Shuttle Solid Rocket Boosters Freedom Star with SRB.JPG
MV Freedom Star was a NASA recovery ship for the Space Shuttle Solid Rocket Boosters

See also

Related Research Articles

Space Shuttle Partially reusable launch system and spacecraft

The Space Shuttle was a partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program name was Space Transportation System (STS), taken from a 1969 plan for a system of reusable spacecraft where it was the only item funded for development. The first of four orbital test flights occurred in 1981, leading to operational flights beginning in 1982. Five complete Space Shuttle orbiter vehicles were built and flown on a total of 135 missions from 1981 to 2011, launched from the Kennedy Space Center (KSC) in Florida. Operational missions launched numerous satellites, Interplanetary probes, and the Hubble Space Telescope (HST); conducted science experiments in orbit; participated in the Shuttle-Mir program with Russia; and participated in construction and servicing of the International Space Station (ISS). The Space Shuttle fleet's total mission time was 1322 days, 19 hours, 21 minutes and 23 seconds.

Space Shuttle <i>Challenger</i> Space shuttle orbiter

Space Shuttle Challenger was the second orbiter of NASA's Space Shuttle program to be put into service, after Columbia. Challenger was built by Rockwell International's Space Transportation Systems Division, in Downey, California. Its maiden flight, STS-6, began on April 4, 1983. The orbiter was launched and landed nine times before disintegrating 73 seconds into its tenth mission, STS-51-L, on January 28, 1986, resulting in the deaths of all seven crew members including a civilian school teacher.

Space Shuttle <i>Columbia</i> Space shuttle orbiter

The Space Shuttle Columbia was the first space-rated orbiter in NASA's Space Shuttle fleet. It launched for the first time on mission STS-1 on April 12, 1981, the first flight of the Space Shuttle program. Serving for over 22 years, it completed 27 missions before disintegrating during re-entry near the end of its 28th mission, STS-107 on February 1, 2003, resulting in the deaths of all seven crew members.

Space Shuttle <i>Discovery</i> Space shuttle orbiter

Space Shuttle Discovery is one of the orbiters from NASA's Space Shuttle program and the third of five fully operational orbiters to be built. Its first mission, STS-41-D, flew from August 30 to September 5, 1984. Over 27 years of service it launched and landed 39 times, aggregating more spaceflights than any other spacecraft to date. The Space Shuttle launch vehicle has three main components: the Space Shuttle orbiter, a single-use central fuel tank, and two reusable solid rocket boosters. Nearly 25,000 heat-resistant tiles cover the orbiter to protect it from high temperatures on re-entry.

Space Shuttle <i>Atlantis</i> Space Shuttle orbiter

Space Shuttle Atlantis is a Space Shuttle orbiter vehicle belonging to the National Aeronautics and Space Administration (NASA), the spaceflight and space exploration agency of the United States. Manufactured by the Rockwell International company in Southern California and delivered to the Kennedy Space Center in Eastern Florida in April 1985, Atlantis is the fourth operational and the second-to-last Space Shuttle built. Its maiden flight was STS-51-J from 3 to 7 October 1985.

Space Shuttle <i>Endeavour</i> Space Shuttle orbiter

Space Shuttle Endeavour is a retired orbiter from NASA's Space Shuttle program and the fifth and final operational Shuttle built. It embarked on its first mission, STS-49, in May 1992 and its 25th and final mission, STS-134, in May 2011. STS-134 was expected to be the final mission of the Space Shuttle program, but with the authorization of STS-135, Atlantis became the last shuttle to fly.

Marshall Space Flight Center Rocketry and spacecraft propulsion research center

The George C. Marshall Space Flight Center (MSFC), located in Huntsville, Alabama, is the U.S. government's civilian rocketry and spacecraft propulsion research center. As the largest NASA center, MSFC's first mission was developing the Saturn launch vehicles for the Apollo program. Marshall has been the lead center for the Space Shuttle main propulsion and external tank; payloads and related crew training; International Space Station (ISS) design and assembly; computers, networks, and information management; and the Space Launch System (SLS). Located on the Redstone Arsenal near Huntsville, MSFC is named in honor of General of the Army George Marshall.

John Young (astronaut) American astronaut, naval officer, test pilot and aeronautical engineer

John Watts Young was an American astronaut, naval officer and aviator, test pilot, and aeronautical engineer. He became the ninth person to walk on the Moon as commander of the Apollo 16 mission in 1972. He flew on four different classes of spacecraft: Gemini, the Apollo command and service module, the Apollo Lunar Module, and the Space Shuttle.

Constellation program Cancelled 2005–2010 United States human spaceflight program, aimed at crewed exploration of the Moon, Mars, and minor planets

The Constellation Program is a cancelled crewed spaceflight program developed by NASA, the space agency of the United States, from 2005 to 2009. The major goals of the program were "completion of the International Space Station" and a "return to the Moon no later than 2020" with a crewed flight to the planet Mars as the ultimate goal. The program's logo reflected the three stages of the program: the Earth (ISS), the Moon, and finally Mars—while the Mars goal also found expression in the name given to the program's booster rockets: Ares. The technological aims of the program included the regaining of significant astronaut experience beyond low Earth orbit and the development of technologies necessary to enable sustained human presence on other planetary bodies.

STS-95 Space Shuttle mission

STS-95 was a Space Shuttle mission launched from Kennedy Space Center, Florida on 29 October 1998, using the orbiter Discovery. It was the 25th flight of Discovery and the 92nd mission flown since the start of the Space Shuttle program in April 1981. It was a highly publicized mission due to former Project Mercury astronaut and United States Senator John H. Glenn Jr.'s return to space for his second space flight. At age 77, Glenn became the oldest person, to date, to go into space. This mission is also noted for inaugurating ATSC HDTV broadcasting in the U.S., with live coast-to-coast coverage of the launch. In another first, Pedro Duque became the first Spaniard in space.

Space Shuttle missions designated STS-3xx were rescue missions which would have been mounted to rescue the crew of a Space Shuttle if their vehicle was damaged and deemed unable to make a successful reentry. Such a mission would have been flown if Mission Control determined that the heat shielding tiles and reinforced carbon-carbon panels of a currently flying orbiter were damaged beyond the repair capabilities of the available on-orbit repair methods. These missions were also referred to as Launch on Demand (LOD) and Contingency Shuttle Crew Support. The program was initiated following loss of Space Shuttle Columbia in 2003. No mission of this type was launched during the Space Shuttle program.

Exploration Systems Architecture Study

The Exploration Systems Architecture Study (ESAS) is the official title of a large-scale, system level study released by the National Aeronautics and Space Administration (NASA) in November 2005 in response to American president George W. Bush's announcement on January 14, 2004 of his goal of returning astronauts to the Moon and eventually Mars — known as the Vision for Space Exploration. The Constellation Program was cancelled in 2010 by the Obama Administration and replaced with the Artemis Program in 2017 under the Trump Administration.

Flight controller Person who aids in spaceflight activities

Flight controllers are personnel who aid space flight by working in such Mission Control Centers as NASA's Mission Control Center or ESA's European Space Operations Centre. Flight controllers work at computer consoles and use telemetry to monitor various technical aspects of a space mission in real time. Each controller is an expert in a specific area and constantly communicates with additional experts in the "back room". The flight director, who leads the flight controllers, monitors the activities of a team of flight controllers, and has overall responsibility for success and safety.

Criticism of the Space Shuttle program stemmed from claims that NASA's Shuttle program failed to achieve its promised cost and utility goals, as well as design, cost, management, and safety issues. Fundamentally, it failed in the goal of reducing the cost of space access. Space Shuttle incremental per-pound launch costs ultimately turned out to be considerably higher than those of expendable launchers. 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, the comparable Proton launch vehicle is said to cost as little as $110 million, or around $5,000 per kilogram to LEO, despite not being reusable.

NASA Independent space agency of the United States federal government

The National Aeronautics and Space Administration is an independent agency of the U.S. federal government responsible for the civilian space program, as well as aeronautics and space research.

Space Shuttle retirement End of NASAs Space Shuttle spacecraft system in 2011

The retirement of NASA's Space Shuttle fleet took place from March to July 2011. Discovery was the first of the three active Space Shuttles to be retired, completing its final mission on March 9, 2011; Endeavour did so on June 1. The final shuttle mission was completed with the landing of Atlantis on July 21, 2011, closing the 30-year Space Shuttle program.

Space tug Used to transfer cargo from one orbit to another

A space tug is a type of spacecraft used to transfer spaceborne cargo from one orbit to another orbit with different energy characteristics. An example would be moving a spacecraft from a low Earth orbit (LEO) to a higher-energy orbit like a geostationary transfer orbit, a lunar transfer, or an escape trajectory.

Artemis program Current U.S. spaceflight program aimed at crewed exploration of the lunar surface

The Artemis program is a U.S. government-funded international human spaceflight program that has the goal of landing "the first woman and the next man" on the Moon, specifically at the lunar south pole region by 2024. The program is carried out predominantly by NASA, U.S. commercial spaceflight companies contracted by NASA, and international partners including the European Space Agency (ESA), the Japan Aerospace Exploration Agency (JAXA), Canadian Space Agency (CSA), the Italian Space Agency (ASI) the Australian Space Agency (ASA), the UK Space Agency (UKSA), the United Arab Emirates Space Agency (UAESA) the State Space Agency of Ukraine, and the Brazilian Space Agency. NASA is leading the program, but expects international partnerships to play a key role in advancing Artemis as the next step towards the long-term goal of establishing a sustainable presence on the Moon, laying the foundation for private companies to build a lunar economy, and eventually sending humans to Mars.



  1. The Soviet shuttle Buran was very similar and was designed to have the same capabilities but made only one uncrewed spaceflight before it was cancelled.

CitationsPD-icon.svg This article incorporates  public domain material from websites or documents ofthe National Aeronautics and Space Administration .

  1. Launius, Roger D. "Space Task Group Report, 1969".
  2. 1 2 "International Space Station Historical Timeline".
  3. "Breaking News | Shannon to review options for deep space exploration". Spaceflight Now. August 29, 2011. Retrieved May 17, 2012.
  4. "Space Shuttle Weather Launch Commit Criteria and KSC End of Mission Weather Landing Criteria". KSC Release No. 39-99. NASA Kennedy Space Center. Archived from the original on June 26, 2009. Retrieved July 6, 2009.
  5. 1 2 3 "Columbia's White External Fuel Tanks".
  6. 1 2 3 Logsdon, John A. "Return to Flight...Challenger Accident".
  7. "NASA, Partners Update Commercial Crew Launch Dates". NASA Commercial Crew Program Blog.
  8. Administrator, NASA (March 6, 2016). "Independence Day at NASA Dryden – 30 Years Ago".
  9. 1 2 3 4 5 "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 Archived August 12, 2006, at the Wayback Machine
  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. Borenstein, Seth (July 5, 2011). "AP Science Writer". Boston Globe. Associated Press. Retrieved July 5, 2011.
  14. 1 2 NASA (2011). "How much does it cost to launch a Space Shuttle?". NASA. Retrieved June 28, 2011.
  15. David, Leonard (February 11, 2005). "Total Tally of Shuttle Fleet Costs Exceed Initial Estimates". . Retrieved August 6, 2006.
  16. Berger, Brian (February 7, 2006). "NASA 2006 Budget Presented: Hubble, Nuclear Initiative Suffer". . Retrieved August 6, 2006.
  17. "NASA Budget Information".
  18. Pielke Jr., Roger; Radford Byerly (April 7, 2011). "Shuttle programme lifetime cost". Nature . 472 (7341): 38. Bibcode:2011Natur.472...38P. doi: 10.1038/472038d . PMID   21475182.
  19. Foust, Jeff (November 20, 2017). "Review: The Space Shuttle Program: Technologies and Accomplishments". The Space Review.
  20. "Roland Statement". NASA. Retrieved June 18, 2018.
  21. Weinrich, Heinz (2013). Management: A Global, Innovative, and Entrepreneurial Perspective. p. 126.
  22. Klikauer, Thomas (2016). Management Education: Fragments of an Emancipatory Theory. p. 220.
  23. Keuper, Franz (2013). Finance Bundling and Finance Transformation: Shared Services Next Level. p. i.
  24. Chien, Philip (June 27, 2006) "NASA wants shuttle to fly despite safety misgivings." The Washington Times
  25. "Dumping NASA's New Ares I Rocket Would Cost Billions".
  26. 1 2 3 4 5 6 7 8 9 10 11 12 13 Jenkins, Dennis R. (2016). Space Shuttle: Developing an Icon – 1972–2013. Specialty Press. ISBN   978-1-58007-249-6.
  27. "The Vision for Space Exploration" (PDF). NASA. February 2004. Retrieved July 6, 2020.
  28. Bush, George (January 14, 2004). "President Bush Announces New Vision for Space Exploration Program". NASA. Retrieved July 6, 2020.
  29. Chang, Kenneth (May 30, 2020). "SpaceX Lifts NASA Astronauts to Orbit, Launching New Era of Spaceflight". The New York Times. Retrieved July 5, 2020.
  30. "Space Shuttle Atlantis Exhibit Opens with Support from Souvenirs".
  31. "Space Shuttle Endeavour homepage".
  32. 1 2 "Human Space Flight (HSF) – Space Shuttle".
  33. 1 2 (, Peter Wainwright. "Space Future – The Future of Space Tourism".
  34. 1 2 3 4 5 (, Peter Wainwright. "Space Future – The Space Tourist".
  35. 1 2
  36. 1 2 "Politics played a big role in why NASA doesn't already have a new spacecraft to replace the retiring space shuttles. Funding and technical challenges put a stop to any attempts to build the ' Space Shuttle 2.'".
  38. 1 2 3 "Reusable Launch Vehicle".
  39. 1 2 3
  40. "X-38 project's cancellation irks NASA, partners".
  41. x0av6 (August 4, 2016). "HL-20 – Lifting Body Spaceplane for Personnel Launch System".
  42. "NASA ACRV".
  43. "NASA Selects Crew and Cargo Transportation to Orbit Partners" (Press release). NASA. August 18, 2006. Retrieved November 21, 2006.
  44. Bergin, Chris (October 6, 2011). "ISS partners prepare to welcome SpaceX and Orbital in a busy 2012". (Not affiliated with NASA). Retrieved December 13, 2011.
  45. Berger, Brian (February 1, 2011). "Biggest CCDev Award Goes to Sierra Nevada". Imaginova Corp. Retrieved December 13, 2011.
  46. "NASA Commercial Crew Program Mission in Sight for 2018". NASA. January 4, 2018. Retrieved April 14, 2018.
  47. "NASA Announces Design for New Deep Space Exploration System". NASA. September 14, 2011. Retrieved April 28, 2012.
  48. Bergin, Chris (February 23, 2012). "Acronyms to Ascent – SLS managers create development milestone roadmap". NASA. Retrieved April 29, 2012.
  49. Foust 2019 , "Artemis 1, or EM-1, will be an uncrewed test flight of Orion and SLS and is scheduled to launch in June of 2020."
  50. Hill 2018 , Page 2, "The first uncrewed, integrated flight test of NASA's Orion spacecraft [...] Enter Distant Retrograde Orbit for next 6–10 days [...] 37,000 miles from the surface of the Moon [...] Mission duration: 25.5 days"
  51. "NASA: Moon to Mars". NASA. Retrieved May 19, 2019.
  52. Hambleton, Kathryn (August 27, 2018). "First Flight With Crew Important Step on Long-Term Return to Moon". NASA. Retrieved May 28, 2019.
  53. Hambleton, Kathryn (May 23, 2019). "NASA's First Flight With Crew Important Step on Long-term Return to the Moon, Missions to Mars". NASA. Retrieved July 10, 2019.
  54. Hill 2018 , Page 3, "Crewed Hybrid Free Return Trajectory, demonstrating crewed flight and spacecraft systems performance beyond Low Earth orbit (LEO) [...] lunar fly-by 4,800 nmi [...] 4 astronauts [...] Mission duration: 9 days"
  55. 1 2 Foust 2019 , "And before NASA sends astronauts to the moon in 2024, the agency will first have to launch five aspects of the lunar Gateway, all of which will be commercial vehicles that launch separately and join each other in lunar orbit. First, a power and propulsion element will launch in 2022. Then, the crew module will launch (without a crew) in 2023. In 2024, during the months leading up to the crewed landing, NASA will launch the last critical components: a transfer vehicle that will ferry landers from the Gateway to a lower lunar orbit, a descent module that will bring the astronauts to the lunar surface, and an ascent module that will bring them back up to the transfer vehicle, which will then return them to the Gateway."
  56. Bridenstine & Grush 2019 , "Now, for Artemis 3 that carries our crew to the Gateway, we need to have the crew have access to a lander. So, that means that at Gateway we're going to have the Power and Propulsion Element, which will be launched commercially, the Utilization Module, which will be launched commercially, and then we'll have a lander there.
  57. Bridenstine & Grush 2019 , "The direction that we have right now is that the next man and the first woman will be Americans, and that we will land on the south pole of the Moon in 2024."
  58. Chang, Kenneth (May 25, 2019). "For Artemis Mission to Moon, NASA Seeks to Add Billions to Budget" . The New York Times . Archived from the original on May 25, 2019. Retrieved May 25, 2019. Under the NASA plan, a mission to land on the moon would take place during the third launch of the Space Launch System. Astronauts, including the first woman to walk on the moon, Mr. Bridenstine said, would first stop at the orbiting lunar outpost. They would then take a lander to the surface near its south pole, where frozen water exists within the craters.
  59. "NASA outlines plans for lunar lander development through commercial partnerships". July 21, 2019.
  60. Olson, John; Joel Kearns (August 2008). "NASA Transition Management Plan" (PDF). JICB-001. National Aeronautics and Space Administration.
  61. Williamson, Ray (1999). "Developing the Space Shuttle" (PDF). Exploring the Unknown: Selected Documents in the History of the U.S. Civil Space Program, Volume IV: Accessing Space. Washington, D.C.: NASA.
  62. Griffin, Michael D. (March 14, 2007). "Human Space Exploration: The Next 50 Years". Aviation Week. Retrieved June 15, 2020.
  63. Klesius, Mike (March 31, 2010). "Spaceflight Safety: Shuttle vs. Soyuz vs. Falcon 9". Air & Space . Retrieved June 15, 2020.
  64. Bell, Trudy; Esch, Karl (January 28, 2016). "The Challenger Disaster: A Case of Subjective Engineering". IEEE Spectrum. IEEE . Retrieved June 18, 2020.
  65. 1 2 Feynman, Richard (June 6, 1986). "Appendix F – Personal observations on the reliability of the Shuttle". Report of the Presidential Commission on the Space Shuttle Challenger Accident. NASA. Retrieved June 18, 2020.
  66. Flatow, Ira; Hamlin, Teri; Canga, Mike (March 4, 2011). "Earlier Space Shuttle Flights Riskier Than Estimated". Talk of the Nation. NPR . Retrieved June 18, 2020.
  67. "Columbia Accident Investigation Board" (PDF). NASA. August 2003. Retrieved June 18, 2020.
  68. Jenkins, Dennis R. (2016). Space Shuttle: Developing an Icon − 1972−2013. Specialty Press. ISBN   978-1-58007-249-6.
  69. "NASA Railroad rides into sunset". Florida Today.

Further reading