![External Tank](https://upload.wikimedia.org/wikipedia/commons/2/22/External_Tank.jpg)
The Space Shuttle external tank (ET) was the component of the
Space Shuttle
The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...
launch vehicle
A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...
that contained the
liquid hydrogen
Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.
To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully li ...
fuel
A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...
and
liquid oxygen
Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an applica ...
oxidizer
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...
. During lift-off and ascent it supplied the fuel and oxidizer under pressure to the three
RS-25
The Aerojet Rocketdyne RS-25, also known as the Space Shuttle Main Engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA's Space Shuttle and is currently used on the Space Launch System (SLS).
Designed and manufacture ...
main engines in the
orbiter
A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, pl ...
. The ET was jettisoned just over 10 seconds after main engine cut-off (MECO) and it re-entered the Earth's atmosphere. Unlike the
Solid Rocket Boosters
A solid rocket booster (SRB) is a large solid propellant motor used to provide thrust in spacecraft launches from initial launch through the first ascent. Many launch vehicles, including the Atlas V, SLS and space shuttle, have used SRBs to give ...
, external tanks were not re-used. They broke up before impact in the
Indian Ocean
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...
(or
Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
in the case of direct-insertion launch trajectories), away from
shipping lane
A sea lane, sea road or shipping lane is a regularly used navigable route for large water vessels (ships) on wide waterways such as oceans and large lakes, and is preferably safe, direct and economic. During the Age of Sail, they were determined b ...
s and were not recovered.
Overview
The ET was the largest element of the Space Shuttle, and when loaded, it was also the heaviest. It consisted of three major components:
* the forward liquid oxygen (LOX) tank
* an unpressurized intertank that contains most of the electrical components
* the aft liquid
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
(LH
2) tank; this was the largest part, but it was relatively light, due to liquid hydrogen's very low density.
The ET was the "backbone" of the shuttle during launch, providing structural support for attachment with the
Space Shuttle Solid Rocket Booster
The Space Shuttle Solid Rocket Booster (SRB) was the first solid-propellant rocket to be used for primary propulsion on a vehicle used for human spaceflight. A pair of these provided 85% of the Space Shuttle's thrust at liftoff and for the first ...
s (SRBs) and orbiter. The tank was connected to each SRB at one forward attachment point (using a crossbeam through the intertank) and one aft bracket, and it was connected to the orbiter at one forward attachment bipod and two aft bipods. In the aft attachment area, there were also
umbilicals that carried
fluid
In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...
s,
gas
Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma).
A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
es,
electric
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by ...
al signals and electrical power between the tank and the orbiter. Electrical signals and controls between the orbiter and the two solid rocket boosters were also routed through those umbilicals.
Although the external tanks were always discarded, it may have been possible to re-use them in orbit.
[ astronautix.com (NASA Report, ''Utilization of the external tanks of the space transportation system'']
Plans for re-use ranged from incorporation into a space station as extra living or research space, as rocket fuel tanks for interplanetary missions (e.g. Mars), to raw materials for orbiting factories.
[
Another concept was to use the ET as a cargo carrier for bulky payloads.][ One proposal was for the primary mirror of a 7-meter aperture telescope to be carried with the tank.][
] Another concept was the Aft Cargo Carrier (ACC).
Versions
Over the years, NASA worked to reduce the weight of the ET to increase overall efficiency. The weight reduced from the ET resulted in an almost equal increase of the cargo-carrying capability of the Space Shuttle.
Orange color
The external tank's orange color is from the sprayed foam insulation, no longer painted white, after the first two missions, saving six hundred pounds. The first two, used for STS-1 and STS-2
STS-2 was the second Space Shuttle mission conducted by NASA, and the second flight of the orbiter ''Columbia''. The mission, crewed by Joe H. Engle and Richard H. Truly, launched on November 12, 1981, and landed two days later on November 14, ...
, were painted white to protect the tanks from ultraviolet light
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
during the extended time that the shuttle spends on the launch pad prior to launch. Because this did not turn out to be a problem, Martin Marietta (now part of Lockheed Martin
The Lockheed Martin Corporation is an American aerospace, arms, defense, information security, and technology corporation with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It ...
) reduced weight by leaving the rust-colored spray-on insulation unpainted beginning with STS-3
STS-3 was NASA's third Space Shuttle mission, and was the third mission for the Space Shuttle ''Columbia''. It launched on March 22, 1982, and landed eight days later on March 30, 1982. The mission, crewed by Jack R. Lousma and C. Gordon Full ...
, saving approximately .[National Aeronautics and Space Administratio]
"NASA Takes Delivery of 100th Space Shuttle External Tank."
Press Release 99-193. August 16, 1999.
Standard Weight Tank
The original ET is informally known as the Standard Weight Tank (SWT) and was fabricated from 2219 aluminum alloy, a high-strength aluminum-copper alloy used for many aerospace applications.
After STS-4
STS-4 was the fourth NASA Space Shuttle mission, and also the fourth for Space Shuttle ''Columbia''. Crewed by Ken Mattingly and Henry Hartsfield, the mission launched on June 27, 1982, and landed a week later on July 4, 1982. Due to parachute ...
, several hundred pounds were eliminated by deleting the anti-geyser line. This line paralleled the oxygen feed line, providing a circulation path for liquid oxygen. This reduces accumulation of gas
Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma).
A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
eous oxygen in the feed line during prelaunch tanking (loading of the LOX). After propellant
A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...
loading data from ground tests and the first few Space Shuttle missions were assessed, the anti-geyser line was removed for subsequent missions. The total length and diameter of the ET remain unchanged. The last SWT, flown on STS-7
STS-7 was NASA's seventh Space Shuttle mission, and the second mission for the Space Shuttle ''Challenger''. During the mission, ''Challenger'' deployed several satellites into orbit. The shuttle launched from Kennedy Space Center on June 18, ...
, weighed approximately inert.
Lightweight Tank
Beginning with the STS-6
STS-6 was the sixth NASA Space Shuttle mission and the maiden flight of the . Launched from Kennedy Space Center on April 4, 1983, the mission deployed the first Tracking and Data Relay Satellite, TDRS-1, into orbit, before landing at Edwards A ...
mission, a lightweight ET (LWT), was introduced. This tank was used for the majority of the Shuttle flights, and was last used during the launch of the ill-fated STS-107
STS-107 was the 113th flight of the Space Shuttle program, and the 28th and final flight of Space Shuttle ''Columbia''. The mission launched from Kennedy Space Center in Florida on January 16, 2003, and during its 15 days, 22 hours, 20 minutes ...
mission. Although tanks vary slightly in weight, each weighed approximately inert.
The weight reduction from the SWT was accomplished by eliminating portions of stringers (structural stiffeners running the length of the hydrogen tank), using fewer stiffener rings and by modifying major frames in the hydrogen tank. Also, significant portions of the tank were mill
Mill may refer to:
Science and technology
*
* Mill (grinding)
* Milling (machining)
* Millwork
* Textile mill
* Steel mill, a factory for the manufacture of steel
* List of types of mill
* Mill, the arithmetic unit of the Analytical Engine early ...
ed differently so as to reduce thickness, and the weight of the ET's aft solid rocket booster
A solid rocket booster (SRB) is a large solid propellant motor used to provide thrust in spacecraft launches from initial launch through the first ascent. Many launch vehicles, including the Atlas V, SLS and space shuttle, have used SRBs to give ...
attachments was reduced by using a stronger, yet lighter and less expensive titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
alloy.
Super Lightweight Tank
The Super Lightweight Tank (SLWT) was first flown in 1998 on STS-91
STS-91 was the final Space Shuttle mission to the ''Mir'' space station. It was flown by Space Shuttle ''Discovery'', and launched from Kennedy Space Center, Florida, on 2 June 1998.
Crew
Mission highlights
STS-91 marked the final Shuttle/''M ...
and was used for all subsequent missions with two exceptions (STS-99
STS-99 was a Space Shuttle mission using ''Endeavour'', that launched on 11 February 2000 from Kennedy Space Center, Florida. The primary objective of the mission was the Shuttle Radar Topography Mission (SRTM) project. This was also the last s ...
and STS-107
STS-107 was the 113th flight of the Space Shuttle program, and the 28th and final flight of Space Shuttle ''Columbia''. The mission launched from Kennedy Space Center in Florida on January 16, 2003, and during its 15 days, 22 hours, 20 minutes ...
).
"FACT SHEET
SPACE SHUTTLE EXTERNAL TANK"
April 2007 Lockheed Martin
The Lockheed Martin Corporation is an American aerospace, arms, defense, information security, and technology corporation with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It ...
*http://www.nasa-klass.com/Curriculum/Get_Training%201/ET/RDG_ET-Additional/ETFactSheet.pdf
*https://www.nasa.gov/returntoflight/system/system_ET.html
The SLWT had basically the same design as the LWT except that it used an aluminium-lithium alloy ( Al 2195) for a large part of the tank structure. This alloy provided a significant reduction in tank weight (about ) over the LWT. Manufacture also included friction stir welding
Friction stir welding (FSW) is a solid-state joining process that uses a non-consumable tool to join two facing workpieces without melting the workpiece material. Heat is generated by friction between the rotating tool and the workpiece material ...
technology. Although all ETs produced after the introduction of the SLWT were of this configuration, one LWT remained in inventory to be used if requested until the end of the shuttle era. The SLWT provided 50% of the performance increase required for the shuttle to reach the International Space Station
The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ...
. The reduction in weight allowed the Orbiter to carry more payload to the highly inclined orbit of the ISS.
Technical specifications
SLWT specifications[
*Length:
*Diameter:
*Empty weight:
*Gross liftoff weight:
LOX tank
*Length:
*Diameter:
*Volume (at 22 ]psig
The pound per square inch or, more accurately, pound-force per square inch (symbol: lbf/in2; abbreviation: psi) is a unit of pressure or of stress based on avoirdupois units. It is the pressure resulting from a force of one pound-force applied to ...
):
*LOX mass (at 22 psig):
*Operation pressure: (absolute)
Intertank
*Length:
*Diameter:
LH2 tank
*Length:
*Diameter:
*Volume (at 29.3 psig):
*LH2 mass (at 29.3 psig):
*Operation pressure: (absolute)
*Operation temperature:
Contractor
The contractor for the external tank was Lockheed Martin
The Lockheed Martin Corporation is an American aerospace, arms, defense, information security, and technology corporation with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It ...
(previously Martin Marietta
The Martin Marietta Corporation was an American company founded in 1961 through the merger of Glenn L. Martin Company and American-Marietta Corporation. In 1995, it merged with Lockheed Corporation to form Lockheed Martin.
History
Martin Mari ...
), New Orleans, Louisiana. The tank was manufactured at the Michoud Assembly Facility
The Michoud Assembly Facility (MAF) is an manufacturing complex owned by NASA in New Orleans East, a district within New Orleans, Louisiana, in the United States. Organizationally it is part of NASA's Marshall Space Flight Center, and is currentl ...
, , and was transported to Kennedy Space Center
The John F. Kennedy Space Center (KSC, originally known as the NASA Launch Operations Center), located on Merritt Island, Florida, is one of the National Aeronautics and Space Administration's (NASA) ten field centers. Since December 1968 ...
by barge
Barge nowadays generally refers to a flat-bottomed inland waterway vessel which does not have its own means of mechanical propulsion. The first modern barges were pulled by tugs, but nowadays most are pushed by pusher boats, or other vessels ...
.
Components
The ET has three primary structures: an LOX tank, an intertank, and an LH2 tank. Both tanks are constructed of aluminium alloy skins with support or stability frames as required. The intertank aluminium structure utilizes skin stringers with stabilizing frames. The primary aluminium materials used for all three structures are 2195 and 2090 alloys. AL 2195 is an Al-Li alloy designed by Lockheed Martin and Reynolds for storage of cryogenics (and used for the SLW version of the ET - earlier versions used Al 2219[Super Lightweight External Tank]
NASA, retrieved December 12, 2013.). Al 2090
AL, Al, Ål or al may stand for:
Arts and entertainment Fictional characters
* Al (Aladdin), Al (''Aladdin'') or Aladdin, the main character in Disney's ''Aladdin'' media
* Al (EastEnders), Al (''EastEnders''), a minor character in the British ...
is a commercially available Al-Li alloy.
Liquid oxygen tank
The LOX tank is located at the top of the ET and has an ogive
An ogive ( ) is the roundly tapered end of a two-dimensional or three-dimensional object. Ogive curves and surfaces are used in engineering, architecture and woodworking.
Etymology
The earliest use of the word ''ogive'' is found in the 13th c ...
shape to reduce aerodynamic drag and aerothermodynamic heating. The ogive nose section is capped by a flat removable cover plate and a nose cone
A nose cone is the conically shaped forwardmost section of a rocket, guided missile or aircraft, designed to modulate oncoming airflow behaviors and minimize aerodynamic drag. Nose cones are also designed for submerged watercraft such a ...
. The nose cone consists of a removable conical assembly that serves as an aerodynamic fairing for the propulsion and electrical system components. The foremost element of the nose cone functions as a cast aluminium lightning rod. The LOX tank volume is at and (cryogenic
In physics, cryogenics is the production and behaviour of materials at very low temperatures.
The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...
).
The tank feeds into a diameter feed line that conveys the liquid oxygen through the intertank, then outside the ET to the aft right-hand ET/orbiter disconnect umbilical. The diameter feed line permits liquid oxygen to flow at approximately with the RS-25s operating at 104% or permits a maximum flow of .
All loads except aerodynamic loads are transferred from the LOX tank at a bolted, flange-joint interface with the intertank.
The LOX tank also includes an internal slosh baffle and a vortex baffle to dampen fluid slosh. The vortex baffle is mounted over the LOX feed outlet to reduce fluid swirl resulting from slosh and to prevent entrapment of gases in the delivered LOX.
Intertank
The intertank is the ET structural connection between the LOX and LH2 tanks. Its primary functions are to receive and distribute all thrust loads from the SRBs and transfer loads between the tanks.
The two SRB forward attach fittings are located 180° apart on the intertank structure. A beam is extended across the intertank structure and is mechanically fastened to the attach fittings. When the SRBs are firing, the beam will flex due to high stress loads. These loads will be transferred to the fittings.
Adjoining the SRB attach fittings is a major ring frame. The loads are transferred from the fittings to the major ring frame which then distributes the tangential loads to the intertank skin. Two panels of the intertank skin, called the thrust panels, distribute the concentrated axial SRB thrust loads to the LOX and LH2 tanks and to adjacent intertank skin panels. These adjacent panels are made up of six stringer-stiffened panels.
The intertank also functions as a protective compartment for housing the operational instrumentation.
Liquid hydrogen tank
The LH2 tank is the bottom portion of the ET. The tank is constructed of four cylindrical barrel sections, a forward dome, and an aft dome. The barrel sections are joined together by five major ring frames. These ring frames receive and distribute loads. The forward dome-to-barrel frame distributes the loads applied through the intertank structure and is also the flange for attaching the LH2 tank to the intertank. The aft major ring receives orbiter-induced loads from the aft orbiter support struts and SRB-induced loads from the aft SRB support struts. The remaining three ring frames distribute orbiter thrust loads and LOX feedline support loads. Loads from the frames are then distributed through the barrel skin panels. The LH2 tank has a volume of at and (cryogenic).
The forward and aft domes have the same modified ellipsoidal shape. For the forward dome, mounting provisions are incorporated for the LH2 vent valve, the LH2 pressurization line fitting, and the electrical feed-through fitting. The aft dome has a manhole fitting for access to the LH2 feedline screen and a support fitting for the LH2 feedline.
The LH2 tank also has a vortex baffle to reduce swirl resulting from slosh and to prevent entrapment of gases in the delivered LH2. The baffle is located at the siphon outlet just above the aft dome of the LH2 tank. This outlet transmits the liquid hydrogen from the tank through a line to the left aft umbilical. The liquid hydrogen feed line flow rate is with the main engines at 104% or a maximum flow of .
Thermal protection system
The ET thermal protection system consists primarily of spray-on foam
Foams are materials formed by trapping pockets of gas in a liquid or solid.
A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the reg ...
insulation
Insulation may refer to:
Thermal
* Thermal insulation, use of materials to reduce rates of heat transfer
** List of insulation materials
** Building insulation, thermal insulation added to buildings for comfort and energy efficiency
*** Insulated ...
(SOFI), plus preformed foam pieces and premolded ablator materials. The system also includes the use of phenolic
Phenolic is an adjective and a substantive (noun) that may apply to :
* Phenol (or carbolic acid), a colorless crystalline solid and aromatic compound
* Phenols, a class of chemical compounds that include phenol
* Phenolic content in wine
* Phenol ...
thermal insulators to preclude air liquefaction. Thermal isolators are required for liquid hydrogen tank attachments to preclude the liquefaction of air on exposed metal, and to reduce heat flow into the liquid hydrogen. While the warmer liquid oxygen results in fewer thermal requirements, the aluminum of the liquid oxygen tank forward areas require protection from aeroheating. Meanwhile, insulation on the aft surfaces prevents liquified air from pooling in the intertank. The middle cylinder of the oxygen tank, and the propellant lines, could withstand the expected depths of frost accumulation condensed from humidity, but the orbiter could not take the damage from ice breaking free. The thermal protection system weighs .
Development of the ETs thermal protection system was problematic. Anomalies in foam application were so frequent that they were treated as variances, not safety incidents. NASA had difficulty preventing fragments of foam from detaching during flight for the entire history of the program:
* STS-1 '' Columbia'', 1981: Crew reports white material streaming past windows during orbiter-external-tank flight. Crew estimated sizes from to fist-sized. Post-landing report describes probable foam loss of unknown location, and 300 tiles needing outright replacement due to various causes.
*STS-4
STS-4 was the fourth NASA Space Shuttle mission, and also the fourth for Space Shuttle ''Columbia''. Crewed by Ken Mattingly and Henry Hartsfield, the mission launched on June 27, 1982, and landed a week later on July 4, 1982. Due to parachute ...
''Columbia'', 1982: PAL ramp loss; 40 tiles require outright replacement.
*STS-5
STS-5 was the fifth NASA Space Shuttle mission and the fifth flight of the Space Shuttle Columbia, Space Shuttle ''Columbia''. It launched on November 11, 1982, and landed five days later on November 16, 1982. STS-5 was the first Space Shuttle ...
''Columbia'', 1982: Continued high rate of tile loss.
*STS-7
STS-7 was NASA's seventh Space Shuttle mission, and the second mission for the Space Shuttle ''Challenger''. During the mission, ''Challenger'' deployed several satellites into orbit. The shuttle launched from Kennedy Space Center on June 18, ...
''Challenger
Challenger, Challengers, or The Challengers may refer to:
Entertainment
Comics and manga
* Challenger (character), comic book character
* ''Challengers'' (manga), manga by Hinako Takanaga
Film and TV
* ''The Challengers'' (TV series), a 1979 ...
'', 1983: Bipod ramp loss photographed, dozens of spot losses.
*STS-27
STS-27 was the 27th NASA Space Shuttle mission, and the third flight of Space Shuttle ''Atlantis''. Launching on December 2, 1988, on a four-day mission, it was the second shuttle flight after the Space Shuttle ''Challenger'' disaster of Janu ...
''Atlantis
Atlantis ( grc, Ἀτλαντὶς νῆσος, , island of Atlas (mythology), Atlas) is a fictional island mentioned in an allegory on the hubris of nations in Plato's works ''Timaeus (dialogue), Timaeus'' and ''Critias (dialogue), Critias'' ...
'', 1988: One large loss of uncertain origin, causing one total tile loss. Hundreds of small losses.
*STS-32
STS-32 was the 33rd mission of NASA's Space Shuttle program, and the ninth launch of . Launched on January 9, 1990, it marked the first use of the Launch Complex 39A of Kennedy Space Center at since 1986; it also marked the first use of Mobil ...
''Columbia'', 1990: Bipod ramp loss photographed; five spot losses up to 70 cm in diameter, plus tile damages.[Insulation problems seen before](_blank)
*STS-50
STS-50 (U.S. Microgravity Laboratory-1) was a NASA Space Shuttle mission, the 12th mission of the '' Columbia'' orbiter. ''Columbia'' landed at Kennedy Space Center for the first time ever due to bad weather at Edwards Air Force Base caused b ...
''Columbia'', 1992: Bipod ramp loss. 20×10×1 cm tile damage.
*STS-52
STS-52 was a ''Space Transportation System'' ( NASA Space Shuttle) mission using Space Shuttle ''Columbia'', and was launched on October 22, 1992.
Crew
Backup crew
Mission highlights
Primary mission objectives were deployment of t ...
''Columbia'', 1992: Portion of bipod ramp, jackpad lost. 290 total tile marks, 16 greater than an inch.
*STS-62
STS-62 was a Space Shuttle program mission flown aboard . The primary payloads were the USMP-02 microgravity experiments package and the OAST-2 engineering and technology payload, both in the orbiter's cargo bay. The two-week mission also featu ...
''Columbia'', 1994: Portion of bipod ramp lost.
In 1995, chlorofluorocarbon-11 (CFC-11) began to be withdrawn from large-area, machine-sprayed foams in compliance with an Environmental Protection Agency
A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...
ban on CFCs under section 610 of the Clean Air Act. In its place, a hydrochlorofluorocarbon
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propan ...
known as HCFC-141b was certified for use and phased into the shuttle program. Remaining foams, particularly detail pieces sprayed by hand, continued to use CFC-11 through the end of the program. These areas include the problematic bipod and PAL ramps, as well as some fittings and interfaces. For the bipod ramp in particular, "the process of applying foam to that part of the tank had not changed since 1993."[Bridis, Ted. "Foam called a concern on flight before Columbia," Deseret News (Salt Lake City), March 22, 2003, pp. 1: http://findarticles.com/p/articles/mi_qn4188/is_20030322/ai_n11384413] The "new" foam containing HCFC 141b was first used on the aft dome portion of ET-82 during the flight of STS-79
STS-79 was the 17th flight of Space Shuttle ''Atlantis'', and the 79th mission of the Space Shuttle program. The flight saw ''Atlantis'' dock with the Russian space station Mir to deliver equipment, supplies and relief personnel. A variety of sc ...
in 1996. Use of HCFC 141b was expanded to the ETs area, or larger portions of the tank, starting with ET-88, which flew on STS-86
STS-86 was a Space Shuttle ''Atlantis'' mission to the Mir space station. This was the last ''Atlantis'' mission before it was taken out of service temporarily for maintenance and upgrades, including the glass cockpit.
Crew
Spacewalk
*'' Par ...
in 1997.
During the lift-off of STS-107
STS-107 was the 113th flight of the Space Shuttle program, and the 28th and final flight of Space Shuttle ''Columbia''. The mission launched from Kennedy Space Center in Florida on January 16, 2003, and during its 15 days, 22 hours, 20 minutes ...
on January 16, 2003, a piece of foam insulation detached from one of the tank's bipod ramps and struck the leading edge of 's wing at a few hundred miles per hour. The impact is believed to have damaged one comparatively large reinforced carbon-carbon panel on the leading edge of the left wing, believed to be about the size of a basketball which then allowed super-heated gas to enter the wing superstructure several days later during re-entry. This resulted in the destruction of ''Columbia'' and the loss of its crew. The report determined that the external fuel tank, ET-93, "had been constructed with BX-250", a closeout foam whose blowing agent was CFC-11 and not the newer HCFC 141b.[Columbia Accident Investigation Board Report, Volume 2, Appendix D](_blank)
Section 11.3 and figure 11-1, p222, Columbia Accident Investigation Board,
In 2005, the problem of foam shed had not been fully cured; on STS-114
STS-114 was the first "Return to Flight" Space Shuttle mission following the Space Shuttle Columbia disaster, Space Shuttle ''Columbia'' disaster. Space Shuttle Discovery, ''Discovery'' launched at 10:39 Eastern Time Zone, EDT (14:39 Coordinated ...
, additional cameras mounted on the tank recorded a piece of foam separated from one of its Protuberance Air Load (PAL) ramps, which are designed to prevent unsteady air flow underneath the tank's cable trays and pressurization lines during ascent. The PAL ramps consist of manually sprayed layers of foam, and are more likely to become a source of debris. That piece of foam did not impact the orbiter.
Reports published concurrent with the STS-114
STS-114 was the first "Return to Flight" Space Shuttle mission following the Space Shuttle Columbia disaster, Space Shuttle ''Columbia'' disaster. Space Shuttle Discovery, ''Discovery'' launched at 10:39 Eastern Time Zone, EDT (14:39 Coordinated ...
mission suggest that excessive handling of the ET during modification and upgrade may have contributed to the foam loss on ''Discovery'' Return to Flight mission. However, three shuttle missions (STS-121
STS-121 was a 2006 NASA Space Shuttle mission to the International Space Station (ISS) flown by . The main purposes of the mission were to test new safety and repair techniques introduced following the ''Columbia'' disaster of February 2003 as w ...
, STS-115
STS-115 was a Space Shuttle mission to the International Space Station (ISS) flown by . It was the first assembly mission to the ISS after the ''Columbia'' disaster, following the two successful ''Return to Flight'' missions, STS-114 and STS-1 ...
, and STS-116
STS-116 was a Space Shuttle mission to the International Space Station (ISS) flown by Space Shuttle '' Discovery''. ''Discovery'' lifted off on 9 December 2006 at 20:47:35 EST. A previous launch attempt on 7 December had been canceled due to cl ...
) were later conducted, all with "acceptable" levels of foam loss. However, on STS-118
STS-118 was a Space Shuttle mission to the International Space Station (ISS) flown by the orbiter '' Endeavour''. STS-118 lifted off on 8 August 2007 from launch pad 39A at Kennedy Space Center (KSC), Florida and landed at the Shuttle Landing Fac ...
a piece of foam (and/or ice) about in diameter separated from a feedline attachment bracket on the tank, ricocheted off one of the aft struts and struck the underside of the wing, damaging two tiles. The damage was not considered dangerous.
Hardware
The external hardware, ET–orbiter attachment fittings, umbilical fittings, and electrical and range safety system weigh .
Vents and relief valves
Each propellant tank has a vent and relief valve
A relief valve or pressure relief valve (PRV) is a type of safety valve used to control or limit the pressure in a system; pressure might otherwise build up and create a process upset, instrument or equipment failure, or fire. The pressure is re ...
at its forward end. This dual-function valve can be opened by ground support equipment for the vent function during prelaunch and can open during flight when the ullage
Ullage or headspace is the unfilled space in a container, particularly with a liquid.
Etymology
The word ''ullage'' comes from the Latin word ''oculus'', used by the Romans to refer to a barrel cork hole. This word was, in turn, taken in medieval ...
(empty space) pressure of the liquid hydrogen tank reaches or the ullage pressure of the liquid oxygen tank reaches .
On early flights, the liquid oxygen tank contained a separate, pyrotechnic
Pyrotechnics is the science and craft of creating such things as fireworks, safety matches, oxygen candles, explosive bolts and other fasteners, parts of automotive airbags, as well as gas-pressure blasting in mining, quarrying, and demolition. ...
ally operated, propulsive tumble vent valve at its forward end. At separation, the liquid oxygen tumble vent valve was opened, providing impulse to assist in the separation maneuver and more positive control of the entry aerodynamics of the ET. The last flight with the tumble valve active was STS-36.
Each of the two aft external tank umbilical plates mate with a corresponding plate on the orbiter. The plates help maintain alignment among the umbilicals. Physical strength at the umbilical plates is provided by bolting corresponding umbilical plates together. When the orbiter GPCs command external tank separation, the bolts are severed by pyrotechnic devices.
The ET has five propellant umbilical valves that interface with orbiter umbilicals: two for the liquid oxygen tank and three for the liquid hydrogen tank. One of the liquid oxygen tank umbilical valves is for liquid oxygen, the other for gaseous oxygen. The liquid hydrogen tank umbilical has two valves for liquid and one for gas. The intermediate-diameter liquid hydrogen umbilical is a recirculation umbilical used only during the liquid hydrogen chill-down sequence during prelaunch.
As the ET is filled, excess gaseous hydrogen is vented through umbilical connections over a large diameter pipe on an arm extended from the fixed service structure. The connection for this pipe between the ET and service structure is made at the ground umbilical carrier plate (GUCP). Sensors are also installed at the GUCP to measure hydrogen levels. Countdowns of STS-80
STS-80 was a Space Shuttle mission flown by Space Shuttle Columbia, Space Shuttle ''Columbia''. The launch was originally scheduled for 31 October 1996, but was delayed to 19 November for several reasons. Likewise, the landing, which was origina ...
, STS-119
STS-119 ( ISS assembly flight 15A) was a Space Shuttle mission to the International Space Station (ISS) which was flown by space shuttle Discovery during March 2009. It delivered and assembled the fourth starboard Integrated Truss Segment (S6), ...
, STS-127
STS-127 ( ISS assembly flight 2J/A) was a NASA Space Shuttle mission to the International Space Station (ISS). It was the twenty-third flight of . The primary purpose of the STS-127 mission was to deliver and install the final two components of t ...
and STS-133
STS-133 ( ISS assembly flight ULF5) was the 133rd mission in NASA's Space Shuttle program; during the mission, Space Shuttle ''Discovery'' docked with the International Space Station. It was ''Discoverys 39th and final mission. The mission l ...
have been halted and resulted in several week delays in the later cases due to hydrogen leaks at this connection. This requires complete draining of the tanks and removal of all hydrogen via helium gas purge, a 20-hour process, before technicians can inspect and repair problems.
A cap mounted to the swing-arm on the fixed service structure covers the oxygen tank vent on top of the ET during the countdown and is retracted about two minutes before lift-off. The cap siphons off oxygen vapor that threatens to form large ice accumulations on the ET, thus protecting the orbiter's thermal protection system during launch.
Sensors
There are eight propellant-depletion sensors, four each for fuel and oxidizer. The fuel-depletion sensors are located in the bottom of the fuel tank. The oxidizer sensors are mounted in the orbiter liquid oxygen feed line manifold downstream of the feed line disconnect. During RS-25 thrusting, the orbiter general-purpose computers constantly compute the instantaneous mass of the vehicle due to the usage of the propellants. Normally, main engine cutoff is based on a predetermined velocity; however, if any two of the fuel or oxidizer sensors sense a dry condition, the engines will be shut down.
The locations of the liquid oxygen sensors allow the maximum amount of oxidizer to be consumed in the engines, while allowing sufficient time to shut down the engines before the oxidizer pumps cavitate
Cavitation is a phenomenon in which the static pressure of a liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, cal ...
(run dry). In addition, of liquid hydrogen are loaded over and above that required by the 6:1 oxidizer–fuel engine mixture ratio. This assures that cutoff from the depletion sensors is fuel-rich; oxidizer-rich engine shutdowns can cause burning and severe erosion of engine components, potentially leading to loss of the vehicle and crew.
Unexplained, erroneous readings from fuel depletion sensors have delayed several shuttle launch attempts, most notably STS-122
STS-122 was a NASA Space Shuttle mission to the International Space Station (ISS), flown by the . STS-122 marked the 24th shuttle mission to the ISS, and the 121st Space Shuttle flight overall.
The mission was also referred to as ISS-1E by the ...
. On December 18, 2007, a tanking test determined the cause of the errors to be a fault in a wiring connector, rather than a failure of the sensors themselves.
Four pressure transducer
A pressure sensor is a device for pressure measurement of gases or liquids. Pressure is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area. A pressure sensor usually act ...
s located at the top of the liquid oxygen and liquid hydrogen tanks monitor the ullage pressures.
The ET also has two electrical umbilicals that carry electrical power from the orbiter to the tank and the two SRBs and provide information from the SRBs and ET to the orbiter.
The ET has external cameras mounted in the brackets attached to the shuttle along with transmitters that can continue to send video data long after the shuttle and the ET have separated.
Range safety system
Earlier tanks incorporated a range safety system to disperse tank propellants if necessary. It included a battery
Battery most often refers to:
* Electric battery, a device that provides electrical power
* Battery (crime), a crime involving unlawful physical contact
Battery may also refer to:
Energy source
*Automotive battery, a device to provide power t ...
power source, a receiver/decoder, antennas and ordnance
Ordnance may refer to:
Military and defense
*Materiel in military logistics, including weapons, ammunition, vehicles, and maintenance tools and equipment.
**The military branch responsible for supplying and developing these items, e.g., the Unit ...
. Starting with STS-79
STS-79 was the 17th flight of Space Shuttle ''Atlantis'', and the 79th mission of the Space Shuttle program. The flight saw ''Atlantis'' dock with the Russian space station Mir to deliver equipment, supplies and relief personnel. A variety of sc ...
this system was disabled, and was completely removed for STS-88
STS-88 was the first Space Shuttle mission to the International Space Station (ISS). It was flown by Space Shuttle ''Endeavour'', and took the first American module, the ''Unity'' node, to the station.
The seven-day mission was highlighted by ...
and all subsequent flights.
Notes
Future use
In 1990, it was suggested that the external tank be used as a lunar habitat
Lunar most commonly means "of or relating to the Moon".
Lunar may also refer to:
Arts and entertainment
* ''Lunar'' (series), a series of video games
* "Lunar" (song), by David Guetta
* "Lunar", a song by Priestess from the 2009 album ''Prior t ...
or as an orbital station. These proposals did not come to fruition.
As basis for Ares in Constellation
With the retirement of the Space Shuttle in 2011,[NASA launch schedule](_blank)
accessed 2009/09/23 NASA, with its canceled Constellation program
The Constellation program (abbreviated CxP) was a 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 " ...
, which featured the Orion spacecraft
Orion (officially Orion Multi-Purpose Crew Vehicle or Orion MPCV) is a Reusable spacecraft, partially reusable crewed spacecraft used in NASA's Artemis program. The spacecraft consists of a Crew Module (CM) space capsule designed by Lockheed ...
, would also have featured the debut of two Shuttle-derived launch vehicles, the human-rated
Human-rating certification, also known as man-rating or crew-rating, is the certification of a spacecraft or launch vehicle as capable of safely transporting humans. There is no one particular standard for human-rating a spacecraft or launch veh ...
Ares I
Ares I was the crew launch vehicle that was being developed by NASA as part of the Constellation program. The name "Ares" refers to the Greek deity Ares, who is identified with the Roman god Mars. Ares I was originally known as the "Crew Launch ...
crew-launch vehicle and the heavy-lift Ares V
The Ares V (formerly known as the Cargo Launch Vehicle or CaLV) was the planned cargo launch component of the cancelled NASA Constellation program, which was to have replaced the Space Shuttle after its retirement in 2011. Ares V was also plan ...
cargo-launch vehicle.
While both the Ares I and Ares V would have utilized a modified five-segment Solid Rocket Booster for its first stage, the ET would have served as a baseline technology for the first stage of the Ares V and the second stage of the Ares I; as a comparison, the Ares I second stage would have held approximately of LOX, versus the ET holding , more than 5 times that amount.
The Ares V first stage, which would have been fitted with five RS-68
The Aerojet Rocketdyne RS-68 (Rocket System 68) is a liquid-fuel rocket engine that uses liquid hydrogen (LH2) and liquid oxygen (LOX) as propellants in a gas-generator power cycle. It is the largest hydrogen-fueled rocket engine ever flown.
It ...
rocket engines (the same engine used on the Delta IV rocket
Delta IV is a group of five expendable launch systems in the Delta rocket family introduced in the early 2000s. Originally designed by Boeing's Defense, Space and Security division for the Evolved Expendable Launch Vehicle (EELV) program, the ...
), would be in diameter, as wide as the S-IC
The S-IC (pronounced S-one-C) was the first stage of the American Saturn V rocket. The S-IC stage was manufactured by the Boeing Company. Like the first stages of most rockets, most of its mass of more than at launch was propellant, in this case ...
and S-II
The S-II (pronounced "S-two") was the second stage of the Saturn V rocket. It was built by North American Aviation. Using liquid hydrogen (LH2) and liquid oxygen (LOX) it had five J-2 engines in a quincunx pattern. The second stage accelerated ...
stages on the Saturn V
Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, with multistage rocket, three stages, and powered with liquid-propellant r ...
rocket. It would have utilized the same internal ET configuration (separate LH2 and LOX tanks separated with an intertank structure), but would have been configured to directly accept LH2 and LOX fill and drain, along with LOX venting on a retractable arm like that used on the Shuttle for LH2.
The Ares I second stage, on the other hand, would have only used the spray-on insulation foam currently used on the current ET. Originally configured like that of the Ares V and the Shuttle ET, NASA, upon completing its design review in 2006, decided, in order to save weight and costs, to reconfigure the internal structure of the second stage by using a combined LH2/LOX tank with the propellants separated by a common bulkhead, a configuration successfully used on the S-II and S-IVB
The S-IVB (pronounced "S-four-B") was the third stage on the Saturn V and second stage on the Saturn IB launch vehicles. Built by the Douglas Aircraft Company, it had one J-2 (rocket engine), J-2 rocket engine. For lunar missions it was fired twi ...
stages of the Saturn V rocket. Unlike the Ares V, which would have used the same fill/drain/vent configuration used on the Shuttle, the Ares I system would have utilized a traditional fill/drain/vent system used on the Saturn IB and Saturn V rockets, but with quick-retracting arms due to the "leap frog" speed the Ares I would expect upon SRB ignition.
As originally envisioned, both the Ares I and Ares V would have used a modified "throw away" version of the RS-25
The Aerojet Rocketdyne RS-25, also known as the Space Shuttle Main Engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA's Space Shuttle and is currently used on the Space Launch System (SLS).
Designed and manufacture ...
engine, but in due course, because of the need to keep R&D costs down and to maintain a schedule set by NASA Administration Michael D. Griffin
Michael Douglas Griffin (born November 1, 1949) is an American physicist and aerospace engineer who served as the Under Secretary of Defense for Research and Engineering from 2018 to 2020. He previously served as Deputy of Technology for the Str ...
to launch the Ares and Orion by 2011, NASA decided (after the 2006 review) to switch to the cheaper RS-68
The Aerojet Rocketdyne RS-68 (Rocket System 68) is a liquid-fuel rocket engine that uses liquid hydrogen (LH2) and liquid oxygen (LOX) as propellants in a gas-generator power cycle. It is the largest hydrogen-fueled rocket engine ever flown.
It ...
engine for the Ares V and to an uprated J-2 engine for the Ares I. Because of the switch to the less efficient RS-68, the Ares V was widened from to accommodate the extra propellants, while the Ares I was reconfigured to incorporate a fifth solid-rocket segment with the J-2X upper stage, as the new engine has less thrust than the original RS-25. Because of the trade-off, NASA would save an estimated USD
The United States dollar (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...
$35 million by using simplified, higher thrust RS-68 engines (reconfigured to fire and perform like the SSME), while at the same time, eliminate the costly tests needed for an air-startable RS-25 for the Ares I.
Proposed for DIRECT
The DIRECT
Direct may refer to:
Mathematics
* Directed set, in order theory
* Direct limit of (pre), sheaves
* Direct sum of modules, a construction in abstract algebra which combines several vector spaces
Computing
* Direct access (disambiguation), a ...
project, a proposed alternative shuttle-derived vehicle, would have used a modified, standard diameter, external tank with three RS-25 engines, with two standard SRBM, as a Crew Launch Vehicle. The same vehicle, with one extra RS-25, and an EDS upper stage, would have served as the Cargo Launch Vehicle. It was planned to save $16 billion, eliminate NASA job losses, and reduce the post-shuttle, manned spaceflight gap from five plus years to two or less.
Core stage of Space Launch System
The Space Launch System
The Space Launch System (SLS) is an American super heavy-lift expendable launch vehicle developed by NASA. As of 2022, SLS has the highest payload capacity of any rocket in operational service, as well as the greatest liftoff thrust of any r ...
(SLS) is a US super heavy-lift expendable launch vehicle
An expendable launch system (or expendable launch vehicle/ELV) is a launch vehicle that can be launched only once, after which its components are either destroyed during reentry or discarded in space. ELVs typically consist of several rocket sta ...
, which is under construction for Artemis 1
Artemis 1, officially Artemis I and formerly Exploration Mission-1 (EM-1), was an uncrewed Moon-orbiting mission. As the first major spaceflight of NASA's Artemis program, Artemis 1 marked the return of the agency to lunar exploration original ...
as of 2020.
The core stage of the rocket is in diameter and mount a Main Propulsion System (MPS) incorporating four RS-25
The Aerojet Rocketdyne RS-25, also known as the Space Shuttle Main Engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA's Space Shuttle and is currently used on the Space Launch System (SLS).
Designed and manufacture ...
engines. The core stage is structurally similar to the Space Shuttle external tank, and initial flights will use modified RS-25D engines left over from the Space Shuttle program. Later flights will switch to a cheaper version of the engine not intended for reuse.
Unflown hardware
MPTA-ET
The Main Propulsion Test Article (MPTA-098) was built by Rockwell International as a testbed for the definitive propulsion and fuel delivery systems for the U.S. Space Shuttle Program.
Description
Never intended for actual spaceflight, the M ...
is on display with the Space Shuttle ''Pathfinder'' at the U.S. Space & Rocket Center in Huntsville, Alabama
Huntsville is a city in Madison County, Limestone County, and Morgan County, Alabama, United States. It is the county seat of Madison County. Located in the Appalachian region of northern Alabama, Huntsville is the most populous city in t ...
.
ET-94 (older version LWT) is in Los Angeles
Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world' ...
and in 2019 will be displayed with Space Shuttle ''Endeavour'' at the California Science Center
The California Science Center (sometimes spelled California ScienCenter) is a state agency and museum located in Exposition Park, Los Angeles, next to the Natural History Museum of Los Angeles County and the University of Southern California. B ...
when the Samuel Oschin Air and Space Center opens.
Three other external tanks were in preparation when the manufacturing stopped. ET-139 is at advanced stage of manufacturing; ET-140 and ET-141 are in early stages of manufacturing.
See also
* Space Launch System
The Space Launch System (SLS) is an American super heavy-lift expendable launch vehicle developed by NASA. As of 2022, SLS has the highest payload capacity of any rocket in operational service, as well as the greatest liftoff thrust of any r ...
(a super heavy-lift launch vehicle under construction)
* DIRECT
Direct may refer to:
Mathematics
* Directed set, in order theory
* Direct limit of (pre), sheaves
* Direct sum of modules, a construction in abstract algebra which combines several vector spaces
Computing
* Direct access (disambiguation), a ...
(a proposed heavy launch system)
* MPTA-ET
The Main Propulsion Test Article (MPTA-098) was built by Rockwell International as a testbed for the definitive propulsion and fuel delivery systems for the U.S. Space Shuttle Program.
Description
Never intended for actual spaceflight, the M ...
(external tank test for STS)
* List of reentering space debris
This is a list of artificial objects atmospheric entry, reentering Earth's atmosphere by mass (see space debris). Such objects are often completely destroyed by reentry heating, but large enough objects or components can survive. Most of the ob ...
* List of heaviest spacecraft
The heaviest artificial objects to reach space include space stations, various upper stages, and discarded Space Shuttle external tanks. Spacecraft may change mass over time such as by use of propellant.
During the Shuttle–Mi ...
References
Further reading
"External Tank Thermal Protection System"
NASA Facts ''Return to Flight Focus Area'', National Aeronautics and Space Administration, Marshall Space Flight Center, Huntsville, Alabama (Pub 8-40392, FS2005-4-10-MSFC, April 2005)
*National Aeronautics and Space Administration. ''Booster Systems Briefs''. Basic, Rev F, PCN 1. April 27, 2005.
*National Aeronautics and Space Administration. ''Shuttle Systems Design Criteria. Volume I: Shuttle Performance Assessment Databook''. NSTS 08209, Volume I, Revision B. March 16, 1999.
External links
*
Columbia Accident Investigation Board
Report, Volume 1, Chapter 3, "Accident Analysis," August 2003
*
Spherical panorama of the bottom of ET-122 in its scaffolding at Michoud Assembly Facility
Spherical panorama of the top of ET-122 in its scaffolding at Michoud Assembly Facility
Spherical panorama of the top of ET-138 in its scaffolding at Michoud Assembly Facility; this is the last tank scheduled to fly
Spherical panorama along the centerline of the bottom of ET-138 near the feedlines in its scaffolding at Michoud Assembly Facility; this is the last tank scheduled to fly
* "Space Shuttle External Tank Used as a Space Station - Study Project Perun" Award-winning student paper from 1979 about building a space station from the External Tank
*
*
{{DEFAULTSORT:Space Shuttle External Tank
External Tank
The Space Shuttle external tank (ET) was the component of the Space Shuttle launch vehicle that contained the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplied the fuel and oxidizer under pressure to the ...
Fuel containers
Historic American Engineering Record in Texas