A Space Shuttle External Tank (ET) on its way to the Vehicle Assembly Building. (Image Credit: NASA/KSC)

A Space Shuttle External Tank (ET) is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplies the fuel and oxidizer under pressure to the three space shuttle main engines (SSME) in the orbiter. The ET is jettisoned just over 10 seconds after MECO (Main Engine Cut Off), where the SSMEs are shut down, and re-enters the Earth's atmosphere. Unlike the Solid Rocket Boosters, external tanks are not reusable. They break up before impact in the Indian Ocean (or Pacific Ocean in the case of direct-insertion launch trajectories, which are currently utilized) away from known shipping lanes. Image File history File links Externaltank. ... Image File history File links Externaltank. ... NASAs Space Shuttle, officially called Space Transportation System (STS), is the United States governments current manned launch vehicle. ... NASAs Space Shuttle, officially called Space Transportation System (STS), is the United States governments current manned launch vehicle. ... This article does not adequately cite its references or sources. ... This article does not cite any references or sources. ... Space Shuttle Main Engine cluster The Space Shuttle Main Engines (SSMEs) are the three main engines on the Space Shuttle orbiter. ... This article does not cite any references or sources. ... The Space Shuttle Solid Rocket Booster (SRB) is the rocket that provides 83% of liftoff thrust for the Space Shuttle. ...

Overview

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

The ET is the largest element of the space shuttle, and when loaded, it is also the heaviest. It consists of three major components: Image File history File links Download high resolution version (700x813, 126 KB) A launch of the NASA Space Shuttle Columbia on STS-1 in April 1981. ... Image File history File links Download high resolution version (700x813, 126 KB) A launch of the NASA Space Shuttle Columbia on STS-1 in April 1981. ...

• the forward liquid oxygen (LOX) tank
• an unpressurized intertank that contains most of the electrical components
• the aft liquid hydrogen (LH2) tank; this is the largest part, but it is relatively light.

The ET is the "backbone" of the shuttle during launch, providing structural support for attachment with the solid rocket boosters and orbiter. The tank is connected to each SRB at one forward attachment point (using a crossbeam through the intertank) and one aft bracket, and it is connected to the orbiter at one forward attachment bipod and two aft bipods. In the aft attachment area, there are also umbilicals that carry fluids, gases, electrical signals and electrical power between the tank and the orbiter. Electrical signals and controls between the orbiter and the two solid rocket boosters also are routed through those umbilicals. General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... A fluid is defined as a substance that continually deforms (flows) under an applied shear stress regardless of the magnitude of the applied stress. ... For other uses, see Gas (disambiguation). ... The article on electrical energy is located elsewhere. ...

Evolution of the ET

Standard Weight Tank

The original ET is informally known as the Standard Weight Tank (SWT). The first two, used in STS-1 and STS-2, were painted white. As a weight-saving measure, Lockheed Martin ceased painting the external tanks beginning with STS-3, leaving only the clear primer over the now-trademark rust-colored insulation, saving approximately 272 kg/600 pounds of weight.^[1] STS-1 is also an abbreviation for Synchronous Transport Signal (level)-1 in the SONET hierarchy. ... STS-2 was a space shuttle mission by NASA using the Space Shuttle Columbia, launched November 12, 1981. ... STS-3 was the third space shuttle mission, and was the third mission for the Space Shuttle Columbia. ...

After STS-4, 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 gaseous oxygen in the feed line during prelaunch tanking (loading of the LOX). After propellant loading data from ground tests and the first few space shuttle missions was assessed, the anti-geyser line was removed for subsequent missions. The total length and diameter of the ET remain unchanged. The last SWT tank, flown on STS-7, weighed approximately 35,000 kg/77,000 pounds inert. STS-4 was a space shuttle mission by NASA using the Space Shuttle Columbia, launched June 27, 1982. ... For other uses, see Gas (disambiguation). ... A propellant is a material that is used to move an object by applying a motive force. ... STS-7 was a space shuttle mission by NASA using the Space Shuttle Challenger, launched June 18, 1983. ...

Lightweight Tank

Beginning with the STS-6 mission, a lightweight ET (LWT), was introduced. This tank was used for the majority of the Shuttle flights, and was last used on the ill-fated STS-107 Space Shuttle Columbia flight. Although tanks vary slightly in weight, each weighed approximately 30,000 kg/66,000 pounds inert. STS-6 was a space shuttle mission by NASA using the Space Shuttle Challenger, launched April 4, 1983. ... The STS-107 crewmembers strike a ‘flying’ pose for their traditional in-flight crew portrait in the SPACEHAB aboard the Space Shuttle Columbia. ... Space Shuttle Columbia (NASA Orbiter Vehicle Designation: OV-102) was the first spaceworthy space shuttle in NASAs orbital fleet. ... The pound or pound-mass (abbreviations: lb, lbm, or sometimes in the United States, #) is a unit of mass (sometimes called weight in everyday parlance) in a number of different systems, including English units, Imperial units, and United States customary units. ...

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 milled differently to reduce thickness, and the weight of the ET's aft solid rocket booster attachments were reduced by using a stronger, yet lighter and less expensive titanium alloy. Endmills for a milling machine. ... The Space Shuttle Solid Rocket Booster (SRB) is the rocket that provides 83% of liftoff thrust for the Space Shuttle. ... General Name, symbol, number titanium, Ti, 22 Chemical series transition metals Group, period, block 4, 4, d Appearance silvery metallic Image:Ti, 22. ...

Super Lightweight Tank

The Super Lightweight Tank (SLWT) was first flown in 1998 on STS-91 and has been used since with only two exceptions (STS-99 and STS-107). The SLWT is basically the same design as the LWT except that it uses an Aluminum/Lithium alloy (Al 2195) for a large part of the tank structure. This alloy provides a significant reduction in tank weight (~3,175 kg/7,000 lb) over the LWT. The disadvantages of the SLWT are its increased cost (~$5 million) and production time (~4 months) when compared to the LWT. Although all ETs currently produced are of the SLWT configuration, one LWT remains in inventory and can be used if requested. This is a mission of the United States Space Shuttle // Crew Charles J. Precourt (4), Commander Dominic L. Pudwill Gorie (1), Pilot Wendy B. Lawrence (3), Mission Specialist Franklin R. Chang-Diaz (6), Mission Specialist Janet L. Kavandi (1), Mission Specialist Valery Victorovitch Ryumin (4), Mission Specialist - Russia Landed and... This is a mission of the United States Space Shuttle // Crew Kevin R. Kregel (4), Mission Commander Dominic L. Pudwill Gorie (2), Pilot Janet L. Kavandi (2), Mission Specialist Janice E. Voss (5), Mission Specialist Mamoru Mohri (2), Mission Specialist (NASDA) - Japan Gerhard P.J. Thiele (1), Mission Specialist - Germany... The STS-107 crewmembers strike a ‘flying’ pose for their traditional in-flight crew portrait in the SPACEHAB aboard the Space Shuttle Columbia. ... Al-Li alloys are a series of alloys of aluminium and lithium, often also including copper and zirconium. ...

The barge carrying ET-119 is towed to Port Canaveral.

Image File history File links Sts_et_barge. ... Image File history File links Sts_et_barge. ...

Technical data

SLWT Specifications

• Length: 153.8 ft (46.9 m)
• Diameter: 27.6 ft (8.4 m)
• Empty Weight: 58,500 lb (26,559 kg)
• Gross Liftoff Weight: 1.680 million lb (762,136 kg)

LOX tank

• Length: 54.6 ft (16.6 m)
• Diameter: 27.6 ft (8.4 m)
• Volume (at 22 psig): 19,541.66 cubic feet; 146,181 gallons (553,355 liters)
• LOX mass (at 22 psig): 1,387,457 lb (629,340 kg)
• Operation Pressure: 20-22 psig (138-152 kPa (gauge))

Intertank A pressure gauge reading in PSI (red scale) and kPa (black scale) The pound-force per square inch (symbol: lbf/in²) is a non-SI unit of pressure based on avoirdupois units. ...

• Length: 22.6 ft (6.9 m)
• Diameter: 27.6 ft (8.4 m)

LH2 tank

• Length: 97.0 ft (29.5 m)
• Diameter: 27.6 ft (8.4 m)
• Volume (at 29.3 psig): 52,881.61 cubic feet; 395,582 gallons (1,497,440 liters)
• LH2 mass (at 29.3 psig): 234,265 lb (106,261 kg)
• Operation Pressure: 32-34 psia (221-235 kPa (absolute))

Contractor

The contractor for the external tank is Lockheed Martin (previously Martin Marietta), New Orleans, Louisiana. The tank is manufactured at the Michoud Assembly Facility, New Orleans, and is transported to Kennedy Space Center by a barge. Lockheed/BAE/Northrop F-35 Lockheed Trident missile C-130 Hercules; in production since the 1950s, now as the C-130J Lockheed Martin (NYSE: LMT) is an aerospace manufacturer formed in 1995 by the merger of Lockheed Corporation with Martin Marietta. ... Martin Marietta Corporation was founded in 1961 through the merger of The Martin Company and American-Marietta Corporation. ... Michoud Assembly Facility in 1968 The Michoud Assembly Facility is an 832 acre (3. ... New Orleans is the largest city in the state of Louisiana, United States of America. ... Merritt Island and Kennedy Space Center (shown in white). ... Self propelled barge carrying bulk crushed stone A barge is a flat-bottomed boat, built mainly for river and canal transport of heavy goods. ...

Components

The ET has three primary structures: an LOX tank, an intertank, and an LH2 tank. Both tanks are constructed of aluminum alloy skins with support or stability frames as required. The intertank aluminum structure utilizes skin stringers with stabilizing frames. The primary aluminum 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. Al 2090 is a commercially available Al-Li alloy.

A cutaway diagram of External Tank.

Image File history File links Download high resolution version (1200x480, 110 KB) Summary A diagram of space shuttle external tank. ... Image File history File links Download high resolution version (1200x480, 110 KB) Summary A diagram of space shuttle external tank. ...

Liquid oxygen tank

The LOX tank is located at the top of the ET and has an ogive shape to reduce aerodynamic drag and aerothermodynamic heating. The ogive nose section is capped by a flat removable cover plate and a nose cone. The nose cone consists of a removable conical assembly that serves as an aerodynamic fairing for the propulsion and electrical system components. The forward most element of the nose cone functions as a cast aluminum lightning rod. The LOX tank volume is 19,744 cubic feet (559 cubic m) at 22 psig (2.5 bar absolute) and -297 °F (90 K, cryogenic). An ogive is a curved shape, figure, or feature. ... A nose cone that contained one of the Voyager spacecraft is seen here as it is mounted on top of a Titan III/Centaur launch vehicle. ... Cryogenics is the study of very low temperatures or the production of the same, and is often confused with cryobiology, the study of the effect of low temperatures on organisms, or the study of cryopreservation. ...

The tank feeds into a 17 inch (430 mm) 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 17 inch (430 mm) diameter feed line permits liquid oxygen to flow at approximately 2,787 lb/s (1264 kg/s) with the SSMEs operating at 104 % or permits a maximum flow of 17,592 gal/min (1.1099 m³/s).

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 which joins both 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 SRB two 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 comprised of six stringer-stiffened panels.

The intertank also functions as a protective compartment for housing the operational instrumentation.

Liquid hydrogen tank

The 70 foot (21 m)-long, 17-inch-diameter liquid oxygen feedline runs externally along the right side of the liquid hydrogen tank up and into the intertank. Two 5-inch-diameter re-pressurization lines run beside it. One supplies hydrogen gas to liquid hydrogen tank and the other supplies oxygen gas to liquid oxygen tank. They are used to maintain the ullage pressure in each tank during the launch.

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 53,488 cubic feet (1,514.6 cubic m) at 29.3 psig (3.02 bar absolute) and -423 °F (20.3 K, cryogenic). Image File history File links Sts_et1. ... Image File history File links Sts_et1. ... In rocketry, ullage is the space within a fuel tank but above the liquid fuel. ...

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 17 inch (430 mm) line to the left aft umbilical. The liquid hydrogen feed line flow rate is 465 lb/s (211 kg/s) with the SSMEs at 104 % or a maximum flow of 47,365 US gal/min (2.988 m³/s).

ET thermal protection system

On the rear part of liquid hydrogen tank, there are Orbiter Attachment Hardware, liquid hydrogen umbilical connection (left), and liquid oxygen umbilical connection (right).

The ET thermal protection system consists primarily of sprayed-on foam insulation, plus preformed foam pieces and premolded ablator materials. The system also includes the use of phenolic 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 4,823 lb (2,188 kg). Image File history File links Download high resolution version (2000x3008, 677 KB) Summary Space Shuttle External Tank ET-119 was lifted off in the Vehicle Assembly Building on mission STS-121. ... Image File history File links Download high resolution version (2000x3008, 677 KB) Summary Space Shuttle External Tank ET-119 was lifted off in the Vehicle Assembly Building on mission STS-121. ... Sea foam on the beach Foam on a cappuccino Fire-retardant, foamed plastic being used as a temporary dam for firestop mortar in a cable penetration in a pulp and paper mill on Vancouver Island, British Columbia, Canada. ... Thermal insulation on the Huygens probe The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer. ... Ablation is defined as the removal of material from the surface of an object by vaporization, chipping, or other erosive processes. ... Phenols, sometimes called phenolics, are a class of chemical compounds consisting of a hydroxyl functional group (-OH) attached to an aromatic hydrocarbon group. ... Example of a thermal column between the ground and a cumulus This article is about the atmospheric phenomenon. ... Aerodynamic heating is the heating of a solid body produced by passage of air or other gases over the body. ...

Development of the ETs thermal protection system has been problematic. Anomalies in foam application were so frequent that they were treated as variances, not safety incidents. NASA has had difficulty preventing fragments of foam from detaching during flight for the entire history of the program:

• STS-1, 1981: Crew reports white material streaming past windows during orbiter-external-tank flight. Crew estimated sizes from 1/4-inch 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, 1984: PAL ramp loss; 40 tiles require outright replacement.

• STS-5, 1982: Continued high rate of tile loss.

• STS-7, 1983: 50x30 cm Bipod ramp loss photographed, dozens of spot losses.^[2]

• STS-27, 1988: One large loss of uncertain origin, causing one total tile loss. Hundreds of small losses.

• STS-32, 1990: Bipod ramp loss photographed; five spot losses up to 70 cm in diameter, plus tile damages.^[3]

• STS-50, 1992: Bipod ramp loss. 20x10x1 cm tile damage.^[3]

• STS-52, 1992: Portion of bipod ramp, jackpad lost. 290 total tile marks, 16 greater than an inch.

• STS-62, 1994: Portion of bipod ramp lost.

In 1995, chlorofluorocarbon-14 (CFC-14) began to be withdrawn from large-area, machine-sprayed foams in compliance with an Environmental Protection Agency ban on CFCs under section 610 of the Clean Air Act. In its place, a hydrochlorofluorocarbon known as HCFC 141b was certified for use and phased into the shuttle program. Remaining foams, particularly detail pieces sprayed by hand, continue to use CFC-14 to this day. 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."^[4] The "new" foam containing HCFC 141b was first used on the aft dome portion of ET-82 during the flight of STS-79 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 in 1997. STS-1 is also an abbreviation for Synchronous Transport Signal (level)-1 in the SONET hierarchy. ... Year 1981 (MCMLXXXI) was a common year starting on Thursday (link displays the 1981 Gregorian calendar). ... STS-4 was a space shuttle mission by NASA using the Space Shuttle Columbia, launched June 27, 1982. ... This article is about the year. ... STS-5 was a space shuttle mission by NASA using the Space Shuttle Columbia, launched November 11, 1982. ... Year 1982 (MCMLXXXII) was a common year starting on Friday (link displays the 1982 Gregorian calendar). ... STS-7 was a space shuttle mission by NASA using the Space Shuttle Challenger, launched June 18, 1983. ... Year 1983 (MCMLXXXIII) was a common year starting on Saturday (link displays the 1983 Gregorian calendar). ... STS-27 was a space shuttle mission by NASA using the Space Shuttle Atlantis. ... Year 1988 (MCMLXXXVIII) was a leap year starting on Friday (link displays 1988 Gregorian calendar). ... STS-32 was the 33rd launch of the Space Shuttle and the 9th launch of Space Shuttle Columbia. ... Year 1990 (MCMXC) was a common year starting on Monday (link displays the 1990 Gregorian calendar). ... STS-50 (U.S. Microgravity Laboratory 1) was a United States Space Shuttle mission, the 12th mission of the Columbia orbiter. ... Year 1992 (MCMXCII) was a leap year starting on Wednesday (link will display full 1992 Gregorian calendar). ... // Crew James B. Wetherbee (2), Commander Michael A. Baker (2), Pilot Charles L. Veach (2), Mission Specialist 1 William M. Shepherd (3), Mission Specialist 2 Tamara E. Jernigan (2), Mission Specialist 3 Steven G. MacLean (1), Payload Specialist 1 - Canada Mission parameters Mass: Orbiter landing with payload: 97,201 kg... Year 1992 (MCMXCII) was a leap year starting on Wednesday (link will display full 1992 Gregorian calendar). ... STS-62 is a Space Shuttle program mission. ... Year 1994 (MCMXCIV) The year 1994 was designated as the International Year of the Family and the International Year of the Sport and the Olympic Ideal by the United Nations. ... For other uses, see CFC (disambiguation). ... EPA redirects here. ... This article or section does not adequately cite its references or sources. ... This article should be merged with Freon, Halon, CFC, and Hydrochlorofluorocarbon and added to Alkyl halide Hydrochlorofluorocarbons (HCFCs) is one of a class of fluorocarbon compounds that are used primarily as chlorofluorocarbon (CFC) substitutes. ... STS-79 is a Space Shuttle program mission. ... This is a mission of the United States Space Shuttle // Crew James D. Wetherbee (4), Commander Michael J. Bloomfield (1), Pilot Vladimir G. Titov (5), (RSA) Mission Specialist Scott E. Parazynski (2), Mission Specialist Jean-Loup Chrétien (3), (CNES) Mission Specialist Wendy B. Lawrence (2), Mission Specialist Launched and...

During the lift-off of STS-107, a piece of foam insulation detached from one of the tank's bipod ramps and struck the leading edge of Space Shuttle Columbia's wing at a few hundred miles per hour. The impact is believed to have damaged several reinforced carbon-carbon thermal tiles on the leading edge of the wing, which 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 STS-107 crewmembers strike a ‘flying’ pose for their traditional in-flight crew portrait in the SPACEHAB aboard the Space Shuttle Columbia. ... Space Shuttle Columbia (NASA Orbiter Vehicle Designation: OV-102) was the first spaceworthy space shuttle in NASAs orbital fleet. ... The Space Shuttle Columbia disaster occurred on February 1, 2003, when the Space Shuttle Columbia disintegrated over Texas during re-entry into the Earths atmosphere, shortly before concluding its 28th mission, STS-107. ...

In 2005, the problem of foam shed has not been fully cured; on STS-114, 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 become a source of debris. That piece of foam did not impact the orbiter. STS-114 was the first return to flight Space Shuttle mission following the Space Shuttle Columbia disaster. ...

Reports published concurrent with the STS-114 mission suggest that excessive handling of the ET during modification and upgrade may have contributed to the foam loss on Discovery's Return to Flight mission. However, three shuttle missions (STS-121,STS-115, and STS-116) have since been conducted, both with "acceptable" levels of foam loss. However on STS-118 a piece of foam (and/or ice) about 10 cm 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. STS-114 was the first return to flight Space Shuttle mission following the Space Shuttle Columbia disaster. ... This article is becoming very long. ... STS-115 was the first Space Shuttle assembly mission to the International Space Station after the Columbia disaster, following the two successful Return to Flight missions, STS-114 and STS-121. ... STS-116 was a flight of the Space Shuttle Discovery to the International Space Station (ISS). ... STS-118 was a Space Shuttle mission to the International Space Station (ISS) flown by Space Shuttle Endeavour. ...

ET hardware

The external hardware, ET / orbiter attachment fittings, umbilical fittings, electrical and range safety system weigh 9,100 pounds (4.1 t).

Each propellant tank has a vent and relief valve 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 (empty space) pressure of the liquid hydrogen tank reaches 38 psig (360 kPa absolute) or the ullage pressure of the liquid oxygen tank reaches 25 psig (270 kPa absolute). A vent can refer to: Look up Vent in Wiktionary, the free dictionary. ... Relief Valve A relief valve opens to release excess pressure when the pressure is too high to protect the vessel or other equipment from overpressurization. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

The liquid oxygen tank contains a separate, pyrotechnically operated, propulsive tumble vent valve at its forward end. At separation, the liquid oxygen tumble vent valve is opened, providing impulse to assist in the separation maneuver and more positive control of the entry aerodynamics of the ET. The word pyrotechnic (literally meaning fire technology) refers to any chemical explosive device, but especially fireworks. ...

The location of ECO sensors in the LH2 tank.

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 SSME 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. Image File history File links Sts_et_ecographic. ... Image File history File links Sts_et_ecographic. ...

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 (run dry). In addition, 1,100 pounds (500 kg) 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. Cavitating propeller model in a water tunnel experiment Cavitation is a general term used to describe the behavior of voids or bubbles in a liquid. ...

Four pressure transducers located at the top of the liquid oxygen and liquid hydrogen tanks monitor the ullage pressures. A pressure sensor measures the pressure, typically of fluids, at a point in a fluid network. ...

Space Shuttle Discovery moments before the scheduled launch of STS-116 in December 2006. Beneath Discovery's wings are the tail masts, which provide several umbilical connections to the orbiter, including a liquid-oxygen line through one and a liquid-hydrogen line through another. Seen above the golden external tank is the vent hood (known as the "beanie cap") at the end of the gaseous oxygen vent arm, extending from the fixed service structure. Vapors are created as the liquid oxygen in the external tank boil off. The hood vents the gaseous oxygen vapors away from the space shuttle vehicle.

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. Image File history File links Download high-resolution version (2000x3008, 405 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Space Shuttle external tank ... Image File history File links Download high-resolution version (2000x3008, 405 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Space Shuttle external tank ... STS-116 was a flight of the Space Shuttle Discovery to the International Space Station (ISS). ... A beanie is the name given to two distinct types of cap or hat. ...

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.

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.

A swing-arm-mounted cap to 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 on the ET, thus protecting the orbiter's thermal protection system during launch.

The ET has external cameras mounted in the brackets which attached to the shuttle along with transmitters that can continue to send video data long after the shuttle and the ET have separated.

ET range safety system

Earlier tanks incorporated a range safety system to disperse tank propellants if necessary. It included a battery power source, a receiver/decoder, antennas and ordnance. Starting with STS-79, this system was no longer used. The assembly was completely removed by the time STS-88 flew, and is not present on any tank since then. Subsequently, it is no longer possible to destroy the vehicle during second stage ascent. Symbols representing a single Cell (top) and Battery (bottom), used in circuit diagrams. ... Preparing C-4 explosive This article is concerned solely with chemical explosives. ... STS-79 is a Space Shuttle program mission. ... STS-88 was a United States Space Shuttle mission. ...

Variants

A cargo carrier addition was studied in 1984. This would consist of a cargo space mounted to the aft hydrogen dome, for cargoes greater than the payload bay diameter of 15 feet. It never flew. Wet Workshop was originally any idea of using a spent rocket booster as a makeshift space station. ...

Before the Challenger accident, west coast launches by the military into polar orbits suffered a disadvantage in lifting capacity compared to low-inclination orbits. A booster module, derived from a Titan II first stage, was proposed. In addition to increasing capacity, the presence of tankage and rocket exhaust would have relieved heating on the aft hydrogen dome. This also failed to fly. A satellite in a polar orbit passes above or nearly above both poles of the planet (or other celestial body) on each revolution. ... Titan II launch vehicle launching Gemini 11 (Sept. ...

Future use

Exploded view of the Ares V.

With the planned retirement of the Space Shuttle by 2010, NASA, with its planned Project Constellation, which features the Apollo-derived Orion spacecraft, will also feature the debut of two Shuttle-derived launch vehicles, the man-rated Ares I crew-launch vehicle and the heavy-lift Ares V cargo-launch vehicle. Image File history File links Ares_V_Exploded_View. ... Image File history File links Ares_V_Exploded_View. ... Project Constellation is NASAs current plan for space exploration. ... Project Apollo was a series of human spaceflight missions undertaken by the United States of America (NASA) using the Apollo spacecraft and Saturn launch vehicle, conducted during the years 1961 – 1975. ... Orion spacecraft in lunar orbit Orion spacecraft with docked LSAM lunar lander Orion spacecraft approaching the ISS Orion during a landing on Earth The Orion Spacecraft (formerly known as the Crew Exploration Vehicle or CEV) is a proposed series of American manned and unmanned spacecraft, intended to replace the Space... Human-rated or man-rated are terms used to describe the certification of a rocket or airplane as worthy of transporting humans. ... It has been suggested that Ares I-1 be merged into this article or section. ... The Ares V (formerly known at the Cargo Launch Vehicle or CaLV) is the cargo launch component of Project Constellation. ...

While both the Ares I and Ares V will utilize a modified five-segment Solid Rocket Booster for its first stage, the current ET will serve 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 will hold approximately 26,000 gallons of LOX, vs. the ET holding 146,000 gallons, more than 5 times that amount).

The Ares V first stage, which will be fitted with five RS-68 rocket engines (the same engine used on the Delta IV rocket), will be 33 feet (10 m) in diameter, as wide as the S-IC and S-II stages on the Saturn V rocket. It will utilize the same internal ET configuration (separate LH₂ and LOX tanks separated with an intertank structure), but will be 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 (as the "beanie cap" would be useless due to the in-line design of the three-stage vehicle). The RS-68 (Rocket System 68) is the largest existing liquid hydrogen / liquid oxygen engine, producing a thrust of 650,000 lbf (2. ... Delta EELV family of launch vehicles (US Govt) The Delta IV family of rockets are EELVs (evolved expendable launch vehicles) built by Boeing IDS. They come in five versions: medium, medium+ (4,2), medium+ (5,2), medium+ (5,4), and heavy. ... The S-IC was the first stage of the Saturn V rocket. ... The S-II was the second stage of the Saturn V rocket. ... For the moon designated Saturn V, see Rhea. ...

Comparison of the Saturn V, Space Shuttle, Ares I, Ares IV and Ares V.

The Ares I second stage, on the other hand, will only use 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 stages of the Saturn V rocket. Unlike the Ares V, which will use the same fill/drain/vent configuration used on the Shuttle, the Ares I system will utilize a traditional fill/drain/vent system used on the Saturn IB and Saturn V rockets, but with quick-retracing arms due to the "leap frog" speed the Ares I will expect upon SRB ignition. Image File history File links Size of this preview: 800 × 497 pixelsFull resolution (1160 × 720 pixel, file size: 283 KB, MIME type: image/png) I combined the two images, [1] and [2], for easier comparison, added names onto all of the rockets, and put in reference lines. ... Image File history File links Size of this preview: 800 × 497 pixelsFull resolution (1160 × 720 pixel, file size: 283 KB, MIME type: image/png) I combined the two images, [1] and [2], for easier comparison, added names onto all of the rockets, and put in reference lines. ... For the moon designated Saturn V, see Rhea. ... NASAs Space Shuttle, officially called Space Transportation System (STS), is the United States governments current manned launch vehicle. ... The Ares IV command module in orbit over Mars in 2032. ... The Ares V (formerly known at the Cargo Launch Vehicle or CaLV) is the cargo launch component of Project Constellation. ... The S-IVB (sometimes S4b) was built by the Douglas Aircraft Company and served as the third stage on the Saturn V and second stage on the Saturn IB. It had one J-2 engine. ...

As originally envisioned, both the Ares I and Ares V would have used a modified "throw away" version of the SSME, but in due course, because of the need to keep R&D costs down and to maintain a schedule set by NASA Administration Michael Griffin to launch the Ares and Orion by 2011, NASA decided to switch to the RS-68 engine for the Ares V and to an uprated J-2 engine for the Ares I. Because of the switch to the RS-68, the Ares V was widened from 28.6 feet (8.7 m) to 33 feet (10 m) to accommodate the extra propellants, while the Ares I was reconfigured to incorporate a fifth solid-rocket segment as the J-2X, as the rocket engine is known, has less thrust than the SSME. Because of the trade-off, NASA would save an estimated $35 million USD by using simplified, higher thrust RS-68 engines (by reconfigured to fire and perform like the SSME), while at the same time, eliminate the costly tests needed for an air-startable SSME for the Ares I (as the J-2X and its predecessor was designed to be started in both mid-air and in a near vacuum). Space Shuttle Main Engine cluster The Space Shuttle Main Engines (SSMEs) are the three main engines on the Space Shuttle orbiter. ... Michael Griffin can refer to: Michael A. W. Griffin, links to Griffin Genealogy pre Norman Conquest. ... J-2 Rocket Engine Specifications. ... The United States dollar is the official currency of the United States. ...

See also

• MPTA-ET

The Main Propulsion Test Article ET was built by NASA to be used in conjuction with MPTA-098 for structural tests of the Space Shuttle prior to construction of flyable craft. ...

References

• "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

• Space Shuttle Propulsion and External Tank Photo Gallery
• STS-115 Launch as seen from ET Camera Video
• Columbia Accident Investigation Board Report Vol. 1, Chp. 3, "Accident Analysis" August 2003

Notes

v • d • e Space Shuttle program
Main articles	Space Shuttle · Space Shuttle program
Components	Orbiter · Solid Rocket Booster · External Tank · Main Engines · Orbital Maneuvering System
Orbiters	Enterprise · Columbia · Challenger · Discovery · Atlantis · Endeavour
Launch sites	Kennedy Space Center LC-39 · Vandenberg Air Force Base · SLC-6
Developments	Shuttle-Derived Launch Vehicle · Shuttle-C · Ares I · Ares V
Testing	Pathfinder · MPTA · MPTA-ET
Other articles	Missions (cancelled) · Decision to build · Crews · Abort modes · Space shuttles in fiction · Crawler-transporter · Shuttle Carrier Aircraft · Space Shuttle America (motion simulator ride) · Shuttle Mockup Explorer