STS External Tank. External Tank The Space Transportation System’s External Tank is one of the four major components that NASA contracted for development.

STS External TankSTS External Tank

External TankExternal Tank

The Space Transportation System’s External Tank is The Space Transportation System’s External Tank is one of the four major components that NASA one of the four major components that NASA contracted for development in 1972contracted for development in 1972

Lockheed-Martin won the ET contract and moved its fabrication Lockheed-Martin won the ET contract and moved its fabrication plant to the NASA facilities in Machoud, Louisianaplant to the NASA facilities in Machoud, Louisiana

The Machoud plant’s location on the Gulf of Mexico allowed The Machoud plant’s location on the Gulf of Mexico allowed shipping the completed External Tanks to the Kennedy Space shipping the completed External Tanks to the Kennedy Space Center by bargeCenter by barge The ET is the largest component on the STS, and could not be The ET is the largest component on the STS, and could not be

shipped by rail or by cargo aircraftshipped by rail or by cargo aircraft

The Machoud plant will be turned over to Boeing for The Machoud plant will be turned over to Boeing for conversion into the upper-stage Ares I fabrication facility as conversion into the upper-stage Ares I fabrication facility as the STS project comes to an endthe STS project comes to an end

External Tank Primary ComponentsExternal Tank Primary Components

Oxygen tankOxygen tank IntertankIntertank Hydrogen tankHydrogen tank

External Tank Primary ComponentsExternal Tank Primary Components

Oxygen tankOxygen tank IntertankIntertank Hydrogen tankHydrogen tank


ET SLWT specs (super lightweight tank = ET SLWT specs (super lightweight tank = SLWT)SLWT)

Length - 46.9 m (153.8 ft)Length - 46.9 m (153.8 ft)

Diameter - 8.4 m (27.6 ft)Diameter - 8.4 m (27.6 ft)

Empty weight - 26,559 kg (58,500 lb)Empty weight - 26,559 kg (58,500 lb)

Gross liftoff weight - 762,136 kg (1.680 million lb)Gross liftoff weight - 762,136 kg (1.680 million lb)

3% empty/gross weight ratio3% empty/gross weight ratio


To minimize weight, the External Tank is constructed To minimize weight, the External Tank is constructed as a pressurized, thin-walled, dual tank assemblyas a pressurized, thin-walled, dual tank assembly

A rigid, light-weight cylindrical shell connects both A rigid, light-weight cylindrical shell connects both liquid oxygen (top) and liquid hydrogen (bottom) liquid oxygen (top) and liquid hydrogen (bottom) tankstanks

The Orbiter's top attach point and the SRB's top The Orbiter's top attach point and the SRB's top attach points are both located on the rigid intertank attach points are both located on the rigid intertank sectionsection SRB Attach points are connected on the intertank through a SRB Attach points are connected on the intertank through a

crossbracecrossbrace The intertank is subjected to some of the highest loads on The intertank is subjected to some of the highest loads on

the STS during the ascent phasethe STS during the ascent phase


Flight dynamics of the ET required the high-density Flight dynamics of the ET required the high-density liquid oxygen be placed above the low-density liquid liquid oxygen be placed above the low-density liquid hydrogen tankhydrogen tank

After separation of the SRBs, the thrust line of the After separation of the SRBs, the thrust line of the main engines runs through the center of mass of the main engines runs through the center of mass of the Orbiter and the ET, which would be much lower if the Orbiter and the ET, which would be much lower if the oxygen tank was below the fuel tankoxygen tank was below the fuel tank The result would be a large rotation moment and a much The result would be a large rotation moment and a much

larger thrust vector correctionlarger thrust vector correction

The arrangement also Improves rotational stability of The arrangement also Improves rotational stability of the ET-Orbiter if one or two of the SSMEs were to fail the ET-Orbiter if one or two of the SSMEs were to fail or shut down prematurelyor shut down prematurely


Other ET components includeOther ET components include Fuel and oxidizer transfer lines to the OrbiterFuel and oxidizer transfer lines to the Orbiter Fuel and oxidizer pressurization lines to the tanksFuel and oxidizer pressurization lines to the tanks Tank ventsTank vents Service ports and linesService ports and lines Tank depletion sensorsTank depletion sensors Thermal insulationThermal insulation Structural attachment points for the Orbiter and Structural attachment points for the Orbiter and

SRBsSRBs Electronic power and control subsystemsElectronic power and control subsystems


The first External Tanks, designated Standard The first External Tanks, designated Standard Tanks (STs), were constructed with an Tanks (STs), were constructed with an empty weight of 35,045 kg (77,100 lb) and a empty weight of 35,045 kg (77,100 lb) and a capacity of:capacity of: LH2 - 395,582 gallonsLH2 - 395,582 gallons LOX - 146,181 gallonsLOX - 146,181 gallons

The first two External Tanks were painted The first two External Tanks were painted whitewhite STS-1STS-1 STS-2STS-2

Four more STs were launched unpainted which Four more STs were launched unpainted which had a weight savings of approximately 2,727 had a weight savings of approximately 2,727 kg (6,000 lb)kg (6,000 lb)


Lightweight Tanks (LWT) were introduced on the STS-6 Lightweight Tanks (LWT) were introduced on the STS-6 missionmission

Included lighter framed and thinner metal sectionsIncluded lighter framed and thinner metal sections Same aluminum alloys as the standard weight tankSame aluminum alloys as the standard weight tank Primarily Al 2219Primarily Al 2219

Lightweight ET tanks were flown on the majority of the Lightweight ET tanks were flown on the majority of the STS missionsSTS missions The ill-fated Columbia STS-107 mission which was the The ill-fated Columbia STS-107 mission which was the

last to use this tanklast to use this tank

As of 2007, a total of 86 lightweight ET tanks were flownAs of 2007, a total of 86 lightweight ET tanks were flown Each had a dry weight of 29,894 kg (65,767 lb)Each had a dry weight of 29,894 kg (65,767 lb)


Super Lightweight Tanks (SLWT) were Super Lightweight Tanks (SLWT) were introduced on the STS-91 mission in introduced on the STS-91 mission in 19891989

SLWT have been used on STS missions SLWT have been used on STS missions since 1989 with the exception of STS-99 since 1989 with the exception of STS-99 and STS-107and STS-107

Design structure of the super Design structure of the super lightweight tank is the same as the lightweight tank is the same as the lightweight tanklightweight tank

Includes lighter aluminum-lithium alloys Includes lighter aluminum-lithium alloys for some of the elementsfor some of the elements

Super Lightweight ET is the lightest but Super Lightweight ET is the lightest but most expensive tank most expensive tank Dry weight of 26,509 kg (58,319 lb)Dry weight of 26,509 kg (58,319 lb)

ET PlumbingET Plumbing

Propellant feed lines for the SSME transfer the Propellant feed lines for the SSME transfer the fuel from the bottom of both tanks to the fuel from the bottom of both tanks to the Orbiter umbilical lines at the bottom Orbiter-Orbiter umbilical lines at the bottom Orbiter-ET attach pointsET attach points

Propellant feed is a simple gravity feed since the Propellant feed is a simple gravity feed since the tanks and fuel are exposed to a minimum of 1-g from tanks and fuel are exposed to a minimum of 1-g from launch to main engine cutoff (MECO)launch to main engine cutoff (MECO)

Tank pressurization is still necessary because the Tank pressurization is still necessary because the turbopumps continually pull propellants from the turbopumps continually pull propellants from the tanks to feed the SSMEstanks to feed the SSMEs


Without positive pressure on the liquid Without positive pressure on the liquid propellants, the tanks would be pulled to a propellants, the tanks would be pulled to a vacuum by the SSME turbopumps resulting vacuum by the SSME turbopumps resulting in gas in the propellant lines which could in gas in the propellant lines which could damage or destroy the SSMEsdamage or destroy the SSMEs Hence, a small part of the fuel and oxidizer pre-Hence, a small part of the fuel and oxidizer pre-

injection gas is isolated, regulated, and then sent injection gas is isolated, regulated, and then sent to the propellant tanks for positive pressurization to the propellant tanks for positive pressurization

A second line to the liquid hydrogen (LH2) tank is A second line to the liquid hydrogen (LH2) tank is used to return excess liquid hydrogen to the LH2 used to return excess liquid hydrogen to the LH2 tank since not all of the LH2 is consumed in the tank since not all of the LH2 is consumed in the fuel feed loop to the SSMEsfuel feed loop to the SSMEs


ET LOX TankET LOX Tank

The LOX tank is an aluminum-lithium alloy The LOX tank is an aluminum-lithium alloy monocoque structure (the skin serves part of the monocoque structure (the skin serves part of the structure)structure) Capacity of 619,090 kg (1,362,000 lb) liquid oxygen at liftoffCapacity of 619,090 kg (1,362,000 lb) liquid oxygen at liftoff Equivalent to 542,639 l (143,350 gal)Equivalent to 542,639 l (143,350 gal)

This is only one-third the volume of the hydrogen This is only one-third the volume of the hydrogen tank, but a propellant weight six times that of the tank, but a propellant weight six times that of the liquid hydrogenliquid hydrogen

Tank pressurization is generated from oxygen gas Tank pressurization is generated from oxygen gas warmed by the SSME's turbopump preburnerwarmed by the SSME's turbopump preburner

The LOX feed line extends on the outside of the tank The LOX feed line extends on the outside of the tank from the LOX tank bottom to the Orbiter umbilical from the LOX tank bottom to the Orbiter umbilical disconnect at the aft attach pointdisconnect at the aft attach point

ET FeedET Feed

Feed line into the SSME Feed line into the SSME manifold abuts the lower manifold abuts the lower Orbiter support, with the Orbiter support, with the hydrogen feed line is hydrogen feed line is located at the opposite aft located at the opposite aft attach pointattach point

Feed-through from the ET Feed-through from the ET tank line to the Orbiter is tank line to the Orbiter is accomplished with a 430 accomplished with a 430 mm (17") inner diameter mm (17") inner diameter quick-disconnect on the quick-disconnect on the Orbiter's umbilical doorOrbiter's umbilical door

ET FeedET Feed

Ball and socket joint Ball and socket joint (lower left)(lower left)

17” quick 17” quick disconnect feed line disconnect feed line (lower right)(lower right)

ET – Socket JointET – Socket Joint


During pad operations, During pad operations, tank venting is made tank venting is made via a top vent valve that via a top vent valve that extends through the extends through the metal tip of the ETmetal tip of the ET

The metal tip also The metal tip also provides an provides an aerodynamic transition aerodynamic transition for the tank top, and for the tank top, and serves as a conductor serves as a conductor for electric field for electric field dissipation to reduce dissipation to reduce lightning strike hazards lightning strike hazards during ascentduring ascent


Tumble valve installed on the upper tank shelf of Tumble valve installed on the upper tank shelf of earlier ETs in order to spin the tank end-over-end earlier ETs in order to spin the tank end-over-end was thought to offer a more reliable reentry was thought to offer a more reliable reentry trajectorytrajectory

Later removed because of the potential hazard of a Later removed because of the potential hazard of a rotating ET striking the Orbiter after separationrotating ET striking the Orbiter after separation


The ET LOX The ET LOX tank includes tank includes internal internal baffles to baffles to reduce reduce sloshing, fluid sloshing, fluid rotation, and rotation, and vortex motionvortex motion


High-density LOX and an elongated tank that is not High-density LOX and an elongated tank that is not perfectly rigid can and does generate low-frequency perfectly rigid can and does generate low-frequency oscillations during launch accelerationoscillations during launch acceleration

These oscillations induce pulsations at the low-pressure These oscillations induce pulsations at the low-pressure oxidizer turbopump input called pogo oscillations which oxidizer turbopump input called pogo oscillations which can damage the SSME turbo machinerycan damage the SSME turbo machinery

The pogo effect that first appeared on the Atlas ICBM The pogo effect that first appeared on the Atlas ICBM

Reduced on the STS with the addition of fluid expansion Reduced on the STS with the addition of fluid expansion chambers (accumulators) in the LOX feed linechambers (accumulators) in the LOX feed line


LOX/LO2 tank specsLOX/LO2 tank specs

Composition:Composition: Aluminum-lithium alloyAluminum-lithium alloy

Length:Length: 16.6 m (54.6 ft)16.6 m (54.6 ft)

Outer diameter:Outer diameter: 8.41 m (27.6')8.41 m (27.6')

Volume:Volume: 560.7 m560.7 m33 (19,786 ft3) (19,786 ft3)

LOX temp:LOX temp: -183-183ooC (-297C (-297ooF)F)

Weight (empty):Weight (empty): 5,455 kg (12,000 lb) 5,455 kg (12,000 lb)

Flow rate (max):Flow rate (max): 1,267 kg/s (2,787 lb/s, 17,597 gal/min) 1,267 kg/s (2,787 lb/s, 17,597 gal/min)

Tank pressurization: 20-22 psiTank pressurization: 20-22 psi

ET IntertankET Intertank

ET intertank is an ET intertank is an unpressurized, unpressurized, rigid, cylindrical rigid, cylindrical structure used to structure used to connect the connect the oxygen tank to oxygen tank to the hydrogen tankthe hydrogen tank

Aluminum-lithium Aluminum-lithium alloy semi alloy semi monocoque skin-monocoque skin-stringer structurestringer structure

Approx. 12,000 lb Approx. 12,000 lb in weightin weight


Used to attach the upper Orbiter and the upper SRBs Used to attach the upper Orbiter and the upper SRBs to the ETto the ET

Intertank also houses the electronics and Intertank also houses the electronics and instrumentation for the ETinstrumentation for the ET

Transfers power and signals from the Orbiter to the Transfers power and signals from the Orbiter to the attached SRBsattached SRBs

The design utility of the intertank allows separate The design utility of the intertank allows separate bulkheads for the fuel and oxidizer tanksbulkheads for the fuel and oxidizer tanks Makes a simpler structure with fewer operational constraintsMakes a simpler structure with fewer operational constraints

Unpressurized cylindrical piece has attach points and Unpressurized cylindrical piece has attach points and reinforced thrust panels to transfer launch and flight reinforced thrust panels to transfer launch and flight loads between the SRBs and the Orbiterloads between the SRBs and the Orbiter


Tank fill and hydrogen vent access, ports and lines Tank fill and hydrogen vent access, ports and lines run from an umbilical plate on the intertank to the run from an umbilical plate on the intertank to the two propellant tankstwo propellant tanks

GH2 vent and LO2 and LH2 fill lines on launch pad GH2 vent and LO2 and LH2 fill lines on launch pad are connected to the umbilical panelare connected to the umbilical panel

Quick disconnects for release as the umbilical arm Quick disconnects for release as the umbilical arm is retracted at liftoffis retracted at liftoff


Intertank specsIntertank specs

Length:Length: 6.86 m (22.5')6.86 m (22.5')

Diameter:Diameter: 8.40 m (27.6')8.40 m (27.6')

Weight:Weight: 5,455 kg (12,000 lb)5,455 kg (12,000 lb)

ET Hydrogen TankET Hydrogen Tank

LH2 tank is the largest of the ET tanksLH2 tank is the largest of the ET tanks

Fusion-welded lightweight aluminum and aluminum-Fusion-welded lightweight aluminum and aluminum-lithium alloy used fpr semi monocoque structurelithium alloy used fpr semi monocoque structure

Interior contains anti-vortex and anti-slosh baffles to Interior contains anti-vortex and anti-slosh baffles to keep gas from entering the liquid feed to the engineskeep gas from entering the liquid feed to the engines

29,000 lb tank has nearly 3 times the volume of the 29,000 lb tank has nearly 3 times the volume of the LO2 tank LO2 tank


To prevent complete fuel depletion and serious To prevent complete fuel depletion and serious damage to the SSMEs, four depletion sensors are damage to the SSMEs, four depletion sensors are placed near the bottom of the LH2placed near the bottom of the LH2

Sensors can initiate the command a shutdown on all Sensors can initiate the command a shutdown on all thee SSMEs if main engine cutoff was not reached thee SSMEs if main engine cutoff was not reached before either the fuel or the oxidizer was exhaustedbefore either the fuel or the oxidizer was exhausted

For safety and SSME protection, 1,100 lb extra fuel is For safety and SSME protection, 1,100 lb extra fuel is included in the LH2 tank to assure a rich mixture at included in the LH2 tank to assure a rich mixture at MECOMECO




LH2 tank specsLH2 tank specs

Composition:Composition: Aluminum-lithium alloyAluminum-lithium alloy

Length:Length: 46.9 m (153.8')46.9 m (153.8')

Outer diameter:Outer diameter: 8.41 m (27.6')8.41 m (27.6')

Volume:Volume: 1,498 m1,498 m33 (52,882 ft (52,882 ft33))

LH2 temp:LH2 temp: -253-253ooC (-423C (-423ooF)F)

Weight (empty):Weight (empty): 5,455 kg (12,000 lb)5,455 kg (12,000 lb)

Flow rate (max):Flow rate (max): 1,267 kg/s (2,787 lb/s, 17,597 gal/min)1,267 kg/s (2,787 lb/s, 17,597 gal/min)

Tank pressurization:Tank pressurization: 32-34 psi32-34 psi

Early assembly of ET with the hydrogen tank on the left and Early assembly of ET with the hydrogen tank on the left and the oxygen tank on the rightthe oxygen tank on the right

ET Thermal ProtectionET Thermal Protection

Thermal protection (TP) is needed on the ET to Thermal protection (TP) is needed on the ET to protect the loaded cryogenic fluids from protect the loaded cryogenic fluids from heating on the launch pad and during ascentheating on the launch pad and during ascent

TP coatings consists of seven types of ablation and insulation TP coatings consists of seven types of ablation and insulation foam layersfoam layers

Light-weight ablation materials are molded, hand formed or Light-weight ablation materials are molded, hand formed or sprayed on several areas on the outer surfaces of the ET to sprayed on several areas on the outer surfaces of the ET to reduce heat flow during high-speed atmospheric ascentreduce heat flow during high-speed atmospheric ascent Outer ablation layers reduce heating from aerodynamic drag Outer ablation layers reduce heating from aerodynamic drag

during ascentduring ascent

Other foams such as polyurethane are injected, poured, Other foams such as polyurethane are injected, poured, sprayed, or molded for specific applications that require sprayed, or molded for specific applications that require durability and efficient thermal insulation properitiesdurability and efficient thermal insulation properities


Compliance with Federal environmental regulations Compliance with Federal environmental regulations required that several of the chlorofluorocarbons be required that several of the chlorofluorocarbons be replaced with hydrochlorofluorocarbons beginning replaced with hydrochlorofluorocarbons beginning with STS-79 and in increasing amounts sincewith STS-79 and in increasing amounts since

Phenolic thermal isolators are placed between the Phenolic thermal isolators are placed between the extremely low-temperature LH2 tank, the tank extremely low-temperature LH2 tank, the tank attachments, and tank supports in order to reduce attachments, and tank supports in order to reduce heat inflow as well as condensation and ice heat inflow as well as condensation and ice formation on the outer ET shellformation on the outer ET shell

Total weight of the ET thermal protection materials is Total weight of the ET thermal protection materials is 2,188 kg (4,823 lb)2,188 kg (4,823 lb)



NASA has had difficulty preventing fragments of foam NASA has had difficulty preventing fragments of foam from detaching during flight for the entire history of from detaching during flight for the entire history of the programthe program

STS-1STS-1, 1981 - Crew reports white material streaming past , 1981 - Crew reports white material streaming past windows during Orbiter-External Tank flight segment. Crew windows during Orbiter-External Tank flight segment. Crew estimated size of debris from 1/4-inch to fist-sized. Post-estimated size of debris from 1/4-inch to fist-sized. Post-landing report describes probable foam loss of unknown landing report describes probable foam loss of unknown location, and 300 Orbiter thermal tiles needing outright location, and 300 Orbiter thermal tiles needing outright replacement due to various causes.replacement due to various causes.

STS-4STS-4, 1984 - Protuberance Air Load (PAL) ramp lost , 1984 - Protuberance Air Load (PAL) ramp lost Additional 40 Orbiter tiles require replacementAdditional 40 Orbiter tiles require replacement

STS-5STS-5, 1982 - Continued high rate of tile loss, 1982 - Continued high rate of tile loss


STS-7STS-7, 1983 - 50x30 cm bipod ramp loss , 1983 - 50x30 cm bipod ramp loss photographed, dozens of spot lossesphotographed, dozens of spot losses

STS-27STS-27, 1988 - One large loss of uncertain origin, , 1988 - One large loss of uncertain origin, causing one total tile loss and hundreds of small causing one total tile loss and hundreds of small losseslosses

STS-32STS-32, 1990 - Bipod ramp loss photographed; five , 1990 - Bipod ramp loss photographed; five spot losses up to 70 cm in diameter, plus tile spot losses up to 70 cm in diameter, plus tile damagesdamages


STS-50STS-50, 1992 - Bipod ramp loss. 20x10x1 cm , 1992 - Bipod ramp loss. 20x10x1 cm tile damagetile damage

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

STS-62STS-62, 1994 - Portion of bipod ramp lost, 1994 - Portion of bipod ramp lost


STS-107STS-107, 2003 – Foam insulation detached from one of the , 2003 – Foam insulation detached from one of the tank's bipod ramps and struck the leading edge of Space tank's bipod ramps and struck the leading edge of Space Shuttle Columbia's wing at several hundred miles per hour. The Shuttle Columbia's wing at several hundred miles per hour. The impact is believed to have damaged several reinforced carbon-impact is believed to have damaged several reinforced carbon-carbon thermal tiles on the leading edge of the wing, which carbon thermal tiles on the leading edge of the wing, which allowed super-heated gas to enter the wing superstructure allowed super-heated gas to enter the wing superstructure several days later during re-entry. This resulted in the several days later during re-entry. This resulted in the destruction of Columbia and the loss of its crew.destruction of Columbia and the loss of its crew.

STS-114STS-114, 2004 - Cameras mounted on the tank recorded a piece , 2004 - Cameras mounted on the tank recorded a piece of foam separated from one of its PAL ramps, which are of foam separated from one of its PAL ramps, which are designed to prevent unsteady air flow underneath the tank’s designed to prevent unsteady air flow underneath the tank’s cable trays and pressurization lines during ascent. The PAL cable trays and pressurization lines during ascent. The PAL ramps consist of manually sprayed layers of foam, and are ramps consist of manually sprayed layers of foam, and are more likely become a source of debris. That piece of foam did more likely become a source of debris. That piece of foam did not impact the Orbiter.not impact the Orbiter.


STS-115STS-115, STS-116, and STS-121 experienced , STS-116, and STS-121 experienced “acceptable" levels of foam loss“acceptable" levels of foam loss

STS-118STS-118, 2007 - A piece of foam and/or ice approx. , 2007 - A piece of foam and/or ice approx. 10 cm in diameter separated from a feedline 10 cm in diameter separated from a feedline attachment bracket on the tank, ricocheted off one of attachment bracket on the tank, ricocheted off one of the aft struts and struck the underside of the wing, the aft struts and struck the underside of the wing, damaging two tiles. The damage was not considered damaging two tiles. The damage was not considered dangerous.dangerous.

ET Prepared forET Prepared forAssemblyAssembly

Completed andCompleted andMounted ETMounted ET

ET Range Safety SystemET Range Safety System

Earlier External Tanks incorporated a pyrotechnic range safety Earlier External Tanks incorporated a pyrotechnic range safety system to split the tanks and disperse the propellants if system to split the tanks and disperse the propellants if necessarynecessary

ET Range safety device included a receiver/decoder, an ET Range safety device included a receiver/decoder, an independent battery power source, antennas, and ordnanceindependent battery power source, antennas, and ordnance

Beginning with STS-79, this system was no longer usedBeginning with STS-79, this system was no longer used Range safety assembly was completely removed for STS-88 and Range safety assembly was completely removed for STS-88 and

has not been present on any tank sincehas not been present on any tank since

Range safety destruct is placed in both SRBs to split the Range safety destruct is placed in both SRBs to split the casing and halt forward thrust in case of errant trajectory that casing and halt forward thrust in case of errant trajectory that could jeopardize life or propertycould jeopardize life or property

ET TransportationET Transportation

Fabricated External Tanks are placed Fabricated External Tanks are placed on a barge at the Michoud, Louisiana on a barge at the Michoud, Louisiana plant and towed to the Kennedy plant and towed to the Kennedy Space Center by tugSpace Center by tug

ET TransportationET Transportation

After delivery at KSC, After delivery at KSC, the ET is placed on a the ET is placed on a carrier and towed into carrier and towed into the Vehicle Assembly the Vehicle Assembly Building for Building for inspection and inspection and storagestorage

ET Flight ProfileET Flight Profile

Approximately 8 1/2 Approximately 8 1/2 minutes after launch, the minutes after launch, the Orbiter is separated from Orbiter is separated from the ET with a delay of 10 the ET with a delay of 10 seconds after MECOseconds after MECO

ET separation procedure ET separation procedure is initiated by a pyro is initiated by a pyro explosion of the three explosion of the three attachment nuts, each of attachment nuts, each of which hold the ET strut to which hold the ET strut to the Orbiterthe Orbiter

Three bolts held by the Three bolts held by the frangible nuts retract into frangible nuts retract into the Orbiter by spring the Orbiter by spring loadingloading


At separation, the ET and Orbiter are traveling at the At separation, the ET and Orbiter are traveling at the same speed and direction but are physically same speed and direction but are physically disconnected, including the umbilical linesdisconnected, including the umbilical lines

RCS jets on the Orbiter then fire in the -Z direction to RCS jets on the Orbiter then fire in the -Z direction to pull the Orbiter away from the ET graduallypull the Orbiter away from the ET gradually

Hydraulic actuators then close the two umbilical Hydraulic actuators then close the two umbilical doors tightly to seal the thermal tile-covered doors doors tightly to seal the thermal tile-covered doors to the Orbiter's bottomto the Orbiter's bottom


After ET - Orbiter separation, the OMS engines are After ET - Orbiter separation, the OMS engines are fired to boost the Orbiter to its planned orbitfired to boost the Orbiter to its planned orbit

Without the OMS burn, the Orbiter would soon Without the OMS burn, the Orbiter would soon descend into the atmosphere just as the ET doesdescend into the atmosphere just as the ET does

The tank continues to arc upward after separation The tank continues to arc upward after separation and reaches an altitude of approximately 111 km (69 and reaches an altitude of approximately 111 km (69 sm, 60 nm) post-separationsm, 60 nm) post-separation

Downrange trajectory brings it down approximately Downrange trajectory brings it down approximately 1,296 km (700 nm) where any remains after the fiery 1,296 km (700 nm) where any remains after the fiery reentry splash down in a predetermined spot in the reentry splash down in a predetermined spot in the Pacific or Indian Oceans, depending on launch orbit Pacific or Indian Oceans, depending on launch orbit inclinationinclination



ET – The FutureET – The Future

NASA Ares I and Ares V vehicles will employ similar NASA Ares I and Ares V vehicles will employ similar tanks to the ET LH2-LOX structuretanks to the ET LH2-LOX structure

Ares I is the crew launcher consisting of a 5-segment SRB, with Ares I is the crew launcher consisting of a 5-segment SRB, with an upper liquid fuel booster an upper liquid fuel booster Same ET LH2 & LOX propellantsSame ET LH2 & LOX propellants Approximately 1/5 the volume of the STS ETApproximately 1/5 the volume of the STS ET Uses only spray-on insulation since crew vehicle rides on top of the Uses only spray-on insulation since crew vehicle rides on top of the

boosterbooster No insulation shedding hazardNo insulation shedding hazard

Ares V uses two 5-segment SRB boosters with a second-stage Ares V uses two 5-segment SRB boosters with a second-stage that has five RS-68 engines that has five RS-68 engines RS-68 are also used on the Delta IVRS-68 are also used on the Delta IV

Second-stage uses the same ET structure concept with separate Second-stage uses the same ET structure concept with separate LH2 and LOX tanks separated with an intertank structureLH2 and LOX tanks separated with an intertank structure

Launchers – Past, Present, and FutureLaunchers – Past, Present, and Future

The EndThe End

STS External Tank. External Tank The Space Transportation System’s External Tank is one of the four major components that NASA contracted for development.

Documents

standard tanks sts

lightweight et tanks

sts project

completed external tanks

dry weight

ftempty weight

weight savings

bargethe et