science

Propulsive fluid accumulator

Propulsive fluid accumulator is a science 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 Propulsive fluid accumulator rather than just read about it. In short: A Propulsive Fluid Accumulator is an artificial Earth satellite which collects and stores oxygen and other atmospheric gases for in-situ refuelling of high-thrust rockets. This eliminates the need to lift oxidizer to orbit and therefore brings significant cost benefits.

Key takeaways

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

Reference excerpt

A Propulsive Fluid Accumulator is an artificial Earth satellite which collects and stores oxygen and other atmospheric gases for in-situ refuelling of high-thrust rockets. This eliminates the need to lift oxidizer to orbit and therefore brings significant cost benefits. A major portion of the total world payload sent into low Earth orbit each year is either liquid oxygen or water.

Propulsive Fluid Accumulator (PROFAC) In the period 1956 to 1963, S.T. Demetriades proposed methods of atmospheric gas accumulation by means of a satellite moving in low Earth orbit, at an altitude of around 120 km, or propellant accumulation by stations on the surface of a planet or by gathering and exploiting interstellar matter. In its simplest form, Demetriades' proposed satellite extracts air from the fringes of the atmosphere, compresses and cools it, and extracts liquid oxygen. The remaining nitrogen is, in part, used as propellant for a nuclear-powered magnetohydrodynamic electromagnetic plasma thruster, which maintains the orbit at about 120 km, or a solar powered thruster (and collection system) for altitudes above 150 km (as stated in the original 1959 JBIS article, p119) compensating for atmospheric drag. This system was called “PROFAC” (PROpulsive Fluid ACcumulator). Several systems were studied, e. g. PROFAC-S for Surface, PROFAC-C for Orbital, PROFAC-A for combination with aerospaceplane making one reusable stage to orbit possible, etc. Several inlets (e. g. conical as in AIEE 10 Aug 1960 San Diego meeting, or funnel) and cryopumps were studied for orbital air collection. The work slowed down in late 1961 although much progress was made in later years on such items as a solar-powered PROFAC. There are, however, safety concerns with placing a nuclear reactor in low Earth orbit.

Propellant harvesting of atmospheric resources in orbit (PHARO) Demetriades' proposal was further refined by Christopher Jones and others in 2010. In this proposal, multiple collection vehicles accumulate propellant gases at around 120 km altitude, later transferring them to a higher orbit. However, Jones' proposal does require a network of orbital power-beaming satellites, to avoid placing nuclear reactors in orbit.

Harvesting at about 200 kilometers altitude (LOX-LEO) Klinkman and Wilkes proposed, at the AIAA Space 2007 and Space 2009 conferences, that gases could be harvested at the very edge of the Earth's atmosphere by a high vacuum pump. An ion propulsion engine would consume a portion of the harvested gases and would restore the spacecraft's orbital momentum. Klinkman's proposal has a fairly low energy threshold for a small-scale harvesting operation, and air friction is far more forgiving at 200 km than at 100 km. Note that S. T. Demetriades pioneered in space propulsion, from the atomic oxygen ramjet (he proved it not feasible in the 1950s) to nuclear, ion, and plasma thrusters. He received the 2010 AIAA Award for Plasmadynamics and Lasers.

Propellant depots

Boeing has suggested a non-extractive propellant depot, or "space gas station," which accumulates material launched from the planet at low cost, allowing future lunar missions without the need for large launch vehicles like the Saturn V. MIT has recently proposed a similar plan which would store emergency fuel reserves left over from lunar missions.

See also Atmosphere-breathing electric propulsion

References

Worked examples

Example 1 — a first encounter with Propulsive fluid accumulator

Start with the simplest possible case. Write down what Propulsive fluid accumulator claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Propulsive fluid accumulator 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 Propulsive fluid accumulator 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 Propulsive fluid accumulator

In research: Propulsive fluid accumulator appears in science 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 Propulsive fluid accumulator 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: Propulsive fluid accumulator is common in secondary-school and first-year university syllabi. It links to neighbouring topics Space access, Spacecraft propulsion, Spaceflight concepts, so understanding it makes those chapters shorter.
In everyday life: Look for Propulsive fluid accumulator 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 Propulsive fluid accumulator in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Propulsive fluid accumulator 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.
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Frequently asked questions

What is Propulsive fluid accumulator in simple terms?

Why does Propulsive fluid accumulator matter?

Because it connects several science 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 Propulsive fluid accumulator?

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 Propulsive fluid accumulator.