Packing airgel with uranium could give us the space engine we’ve been looking for: ScienceAlert

New propulsion ideas for moving through space seem to be a dozen recently. In addition to the typical argument between solar sails and chemical propulsion, there is a potential third avenue – a nuclear rocket engine.

While we’ve discussed them here at Universe Today before, NASA’s Institute for Advanced Concepts awarded a grant to a company called Positron Dynamics to develop a new type of nuclear fission fragment (FFRE) rocket engine. It could strike a balance between the power of chemical engines and the longevity of solar sails.

FFREs are not a new concept per se, but many have huge technical hurdles to overcome before they are considered useful. Its advantages, such as high specific impulse and extremely high power density, are outweighed by its disadvantages, such as requiring a complicated form of plasma levitation.

Positron Dynamics hopes to balance this balance by utilizing two separate advances derived from other areas of research. The first innovative approach would be to place the fissile material in an ultralight airgel. The second would be to implement a superconducting magnet to contain these fission particles.

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FFREs utilize essentially the same nuclear process that powers nuclear power plants on Earth. However, instead of just generating electricity, they also generate thrust and a very high amount of thrust.

However, it is not practical to send an entire rod of uranium fuel, as used in fission reactors here on Earth, into space.

Incorporating the fuel itself into one of the lightest known human substances solves this problem.

Aerogels are extraordinarily airy materials that appear ethereal when someone holds them, as in the key image above. Incorporating fuel particles for the fission reaction into them would be a convenient way to hold the fuel together while still allowing the overall structure to be light enough to be launched into orbit.

However, the structure of the aerogels themselves wouldn’t do much to contain the fission fragments as they break apart. To do that would require a massive external force, which is where the superconducting magnet comes in.

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Superconducting magnets are typically used in experimental fusion power plants, where they are used to contain the plasma needed to heat the fusion fuel, but which would otherwise destroy any normal material. Given all the interest in fusion research lately, high power magnets have also received extra research attention.

Adding one to one FFRE would allow engineers to funnel the fission fragments all in the same direction, effectively turning them into a thrust vector. It has the added benefit of not allowing the fragments to destroy other parts of the engine as well.

So far this is all very theoretical as there are still many hurdles to overcome. But that’s exactly what the NIAC is for – funding early-stage projects and trying to de-risk them.

Maybe someday FFREs will be able to hit that sweet spot of speed and fuel efficiency that so many rocket scientists dream of.

This article was originally published by Universe Today. Read the original article.

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