engineering

LI-900

LI-900 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 LI-900 rather than just read about it. In short: LI-900 is a type of reusable surface insulation tile developed and manufactured by Lockheed Missiles and Space Company. It was designed for use on the Space Shuttle orbiter as part of its thermal protection system to minimize thermal conductivity while providing maximum thermal shock resistance.

Key takeaways

LI-900 belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect LI-900 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of LI-900 from memory before moving on to harder problems.

Reference excerpt

LI-900 is a type of reusable surface insulation tile developed and manufactured by Lockheed Missiles and Space Company. It was designed for use on the Space Shuttle orbiter as part of its thermal protection system to minimize thermal conductivity while providing maximum thermal shock resistance.

Statistics LI-900 has a bulk density of 144.2 kg/m3, or 9 lb/ft3. Due to this material’s density being 9 lb/ft3 it was called the LI-900. It is made from 99.9% pure silica glass fibres, and is 94% air by volume. An LI-900 tile can be heated to 1,204 °C (1,477 K; 2,199 °F) and then immediately plunged into cold water and suffer no damage. Black and white tiles were used on the Space Shuttle to control the temperature of the vehicle while in orbit.

White tiles (known as low temperature reusable surface insulation or LRSI) were used mainly on the upper surface and have higher thermal reflectivity. These are therefore pointed towards the sun in order to minimize solar gain. Black tiles (known as high temperature reusable surface insulation or HRSI) are optimized for maximum emissivity, which means they lose heat faster than white tiles. This property is required in order to maximise heat rejection during re-entry. There are typically 20,000 HRSI LI-900 tiles on a Space Shuttle, and 725 LRSI LI-900 tiles.

Problems

Strength As a result of optimizing its thermal properties, overall strength was reduced. The tile was therefore not suitable to be used in high-stress areas such as around the landing gear doors and windows. To solve this, a higher strength version of the LI-900 material was produced, with a bulk density of 352.4 kg/m3 (22 lb/ft3), which was called the LI-2200. This tile provided the strength and insulating properties, but with a considerable weight penalty.

See also Space Shuttle thermal protection system Atmospheric reentry

References

Sources NASA facts on the Orbiter Thermal Protection System Research and technology report on shuttle materials resistant to MMOD

Illustrations

Worked examples

Example 1 — a first encounter with LI-900

Start with the simplest possible case. Write down what LI-900 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 LI-900 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 LI-900 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 LI-900

In research: LI-900 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 LI-900 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: LI-900 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Lockheed Corporation, Space Shuttle program, Thermal protection, so understanding it makes those chapters shorter.
In everyday life: Look for LI-900 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 LI-900 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what LI-900 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 LI-900 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is LI-900 in simple terms?

Why does LI-900 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 LI-900?

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 LI-900.