engineering

Space elevator construction

Space elevator construction 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 elevator construction rather than just read about it. In short: Three basic approaches for constructing a space elevator have been proposed: First, using in-space resources to manufacture the whole cable in space. Second, launching and deploying a first seed cable and successively reinforcing the seed cable by additional cables, transported by climbers.

Key takeaways

Space elevator construction 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 elevator construction to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Space elevator construction from memory before moving on to harder problems.

Reference excerpt

Three basic approaches for constructing a space elevator have been proposed: First, using in-space resources to manufacture the whole cable in space. Second, launching and deploying a first seed cable and successively reinforcing the seed cable by additional cables, transported by climbers. Third, spooling two cables down and then connecting the ends, forming a loop.

Early construction concepts There are two approaches to constructing a space elevator. Either the cable is manufactured in space or it is launched into space and gradually reinforced by additional cables, transported by climbers into space. Manufacturing the cable in space could be done in principle by using an asteroid or Near-Earth object. One early plan involved lifting the entire mass of the elevator into geostationary orbit, and lowering one cable downwards towards the Earth's surface while simultaneously another cable is deployed upwards directly away from the Earth's surface. Tidal forces (gravity and centrifugal force) would naturally pull the cables directly towards and directly away from the Earth and keep the elevator balanced around geostationary orbit. As the cable is deployed, Coriolis forces would pull the upper portion of the cable somewhat to the West and the lower portion of the cable somewhat to the East; this effect can be controlled by varying the deployment speed. However, this approach requires lifting hundreds or even thousands of tons on conventional rockets, an expensive proposition.

Cable seeding design Bradley C. Edwards, former Director of Research for the Institute for Scientific Research (ISR), based in Fairmont, West Virginia proposed that, if carbon nanotubes with sufficient strength could be made in bulk, a space elevator could be built in little more than a decade, rather than the far future. He proposed that a single hair-like 20-ton 'seed' cable be deployed in the traditional way, giving a very lightweight elevator with very little lifting capacity. Then, progressively heavier cables would be pulled up from the ground along it, repeatedly strengthening it until the elevator reaches the required mass and strength. This is much the same technique used to build suspension bridges. The length of this cable is 35,786 km or 35,786,000 m. A 20-ton cable would weigh about 1.12 grams per m.

Loop elevator design This is a less well developed design, but offers some other possibilities. If the cable provides a useful tensile strength to density of about 48.1 GPa/(kg/m3) or above, then a constant width cable can reach beyond geostationary orbit without breaking under its own weight. The far end can then be turned around and passed back down to the Earth forming a constant width loop, which would be kept spinning to avoid tangling. The two sides of the loop are naturally kept apart by coriolis forces due to the rotation of the Earth and the loop. By increasing the thickness of the cable from the ground a very quick (exponential) build-up of a new elevator may be performed (it helps that no active climbers are needed, and power is applied mechanically.) However, because the loop runs at constant speed, joining and leaving the loop may be somewhat challenging, and the carrying capacity of such a loop is lower than a conventional tapered design.

Current status Currently, the cable seeding design and the space manufacturing design are considered. The space manufacturing design would use a carbonaceous asteroid or near-Earth object for mining its material and producing a carbon nanotube cable. The cable would then be transported back to geostationary orbit and spooled down. Although this approach shifts the construction complexity away from the use of climbers in the cable seeding design, it increases the complexity of the required in-space infrastructure. The cable seeding design could be rendered infeasible in case the material strength is considerably lower than was projected by Brad Edwards. Current technological status of the cable seeding design:

a) It would take 5 days to reach a geostationary altitude of 36,000 km with this speed.

See also Elevator:2010 Lunar space elevator Non-rocket spacelaunch Space elevator economics Space elevators in fiction Space elevator safety

References

External links The Space Elevator Reference Audacious & Outrageous: Space Elevators

Worked examples

Example 1 — a first encounter with Space elevator construction

Start with the simplest possible case. Write down what Space elevator construction 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 elevator construction 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 elevator construction 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 elevator construction

In research: Space elevator construction 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 elevator construction 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 elevator construction is common in secondary-school and first-year university syllabi. It links to neighbouring topics Space elevator, Space manufacturing, Transportation engineering, so understanding it makes those chapters shorter.
In everyday life: Look for Space elevator construction 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 elevator construction in 20 minutes

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

Frequently asked questions

What is Space elevator construction in simple terms?

Why does Space elevator construction 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 elevator construction?

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 elevator construction.