engineering

Space Shuttle external tank

Space Shuttle external tank is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Space Shuttle external tank rather than just read about it. In short: 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 three RS-25 main engines in the orbiter.

Key takeaways

Space Shuttle external tank belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Space Shuttle external tank to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Space Shuttle external tank from memory before moving on to harder problems.

Reference excerpt

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 three RS-25 main engines in the orbiter. 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, external tanks were not re-used. They broke up before impact in the Indian Ocean (or Pacific Ocean in the case of direct-insertion launch trajectories), away from shipping lanes 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 (LH2) 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 Boosters (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 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 were also routed through those umbilicals. Although the external tanks were always discarded, it may have been possible to re-use them in orbit. 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 the color of the spray-on foam insulation. The first two tanks, used for STS-1 and STS-2, were painted white to protect the tanks from ultraviolet light during the extended time that the shuttle spent on the launch pad prior to launch. NASA engineer Farouk Huneidi told the agency that the paint did not actually protect the foam. Martin Marietta (now part of Lockheed Martin) reduced weight by leaving the rust-colored spray-on insulation unpainted beginning with STS-3, saving approximately 272 kg (600 lb).

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, 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 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, weighed approximately 77,000 pounds (35,000 kg) inert.

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 during the launch of the ill-fated STS-107 mission. Although tanks vary slightly in weight, each weighed approximately 66,000 pounds (30,000 kg) 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 milled differently so as to reduce thickness, and the weight of the ET's aft solid rocket booster attachments was reduced by using a stronger, yet lighter and less expensive titanium alloy.

Super Lightweight Tank The Super Lightweight Tank (SLWT) was first flown in 1998 on STS-91 and was used for all subsequent missions with two exceptions (STS-99 and STS-107). 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 7,000 pounds or 3,175 kg) over the LWT. Manufacture also included friction stir welding 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 reduction in weight allowed the Orbiter to carry more payload to the highly inclined orbit of the ISS.

Technical specifications SLWT specifications

Length: 153.8 ft (46.9 m) Diameter: 27.6 ft (8.4 m) Empty weight: 58,500 lb (26,500 kg) Gross liftoff weight: 1,680,000 lb (760,000 kg) LOX tank

Length: 54.6 ft (16.6 m) Diameter: 27.6 ft (8.4 m) Volume (at 22 psig): 19,541.66 cu ft (146,181.8 US gal; 553,358 L) LOX mass (at 22 psig): 1,387,457 lb (629,340 kg) Operation pressure: 34.7–36.7 psi (239–253 kPa) (absolute) Intertank

Length: 22.6 ft (6.9 m) Diameter: 27.6 ft (8.4 m) LH2 tank

Length: 97.0 ft (29.6 m) Diameter: 27.6 ft (8.4 m) Volume (at 29.3 psig): 52,881.61 cu ft (395,581.9 US gal; 1,497,440 L) LH2 mass (at 29.3 psig): 234,265 lb (106,261 kg) Operation pressure: 32–34 psi (220–230 kPa) (absolute) Operation temperature: −423 °F (−253 °C)

Contractor The contractor for the external tank was Lockheed Martin (previously Martin Marietta), New Orleans, Louisiana. The tank was manufactured at the Michoud Assembly Facility, New Orleans, and was transported to Kennedy Space Center by barge.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Space Shuttle external tank

Start with the simplest possible case. Write down what Space Shuttle external tank claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Space Shuttle external tank before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Space Shuttle external tank ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Space Shuttle external tank

In research: Space Shuttle external tank appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Space Shuttle external tank in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Space Shuttle external tank is common in secondary-school and first-year university syllabi. It links to neighbouring topics Fuel containers, Historic American Engineering Record in Texas, Space Shuttle program, so understanding it makes those chapters shorter.
In everyday life: Look for Space Shuttle external tank outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Space Shuttle external tank in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Space Shuttle external tank means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Space Shuttle external tank out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Space Shuttle external tank in simple terms?

Why does Space Shuttle external tank matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Space Shuttle external tank?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Space Shuttle external tank.