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Project Orion

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Re: Project Orion

#61

Post by walrus01 »

jerf wrote: post #26
perihelions wrote: post #19

Earlier quoted context omitted.

There's one more: the boring idea of combining a closed, electric-generating nuclear fission system with an (electric-powered) ion engine. Both components being flight tested and not crazy.

That doesn't sound like something that could get you off of the Earth. It's probably a great choice for once you're already in space, where being able to apply even very small thrusts nearly-continuously really adds up.

The Soviets literally launched reactors into space in the late 70s for very high RF power radar satellites (intended to track US navy, among other things). One deorbited over northern Canada.

https://www.google.com/search?client=firefox-b-d&q=soviet+ro...

Of course anything related to hall effect/ion thrusters isn't going to get you off the earth even with some of the theoretical/bench-tested-only 100kW (electrical load) thrusters under development. These are things with very low thrust at any instantaneous moment in time but very high specific impulse from 3800 to 6000 ISP or more. Meant to be used in vacuum only.

Re: Project Orion

#62

Post by panick21_ »

st_goliath wrote: post #6

An other quite interesting concept (also a little less "out there" and actually, successfully tested) is the NERVA engine, also linked at the bottom of the article[1]. It uses a nuclear reactor to heat up a single propellant (liquid hydrogen) which then rapidly expands as it goes out the nozzle at the end, resulting in quite high specific impulse and is more efficient than a chemical rocket. If we want to go really f…

And DoD and NASA are right now funding this research again.

Edit: NERVA style, not Salt water thing.

Re: Project Orion

#63

Post by gkoller »

marktangotango wrote: post #8

There was a classic science fiction story with a twist on this idea; a low tech species was about to be discovered by a more advanced species. And according to the rules of the more advanced species, any planet that wasn't capable of space travel would become a client or vassal, and a planet with space travel would be seen as a peer. The protagonist built a pusher style rocket using an explosive, and launched the lig…

Speaking of sci-fi, project orion/nuclear propulsion is also featured in Marko Kloos' Frontlines series (though not in the first book if I remember correctly)

https://www.markokloos.com/?page_id=1859

Re: Project Orion

#64

Post by Schroedingersat »

walrus01 wrote: post #61
jerf wrote: post #26

Earlier quoted context omitted.

That doesn't sound like something that could get you off of the Earth. It's probably a great choice for once you're already in space, where being able to apply even very small thrusts nearly-continuously really adds up.

The Soviets literally launched reactors into space in the late 70s for very high RF power radar satellites (intended to track US navy, among other things). One deorbited over northern Canada. https://www.google.com/search?client=firefox-b-d&q=soviet+ro... Of course anything related to hall effect/ion thrusters isn't going to get you off the earth even with some of the theoretical/bench-tested-only 100kW (electrical l…

Space based fission electric isn't very good though. Hence why they use PV now.

NASA are developing a system that aims to be 6.67We/kg https://en.wikipedia.org/wiki/Kilopower

Compare to 50We/kg for cheap consumer grade flexible PV designed to be kicked around for a decade including an inverter.

And that's with an atmosphere to use as a heatsink instead of radiators.

Re: Project Orion

#65

Post by soco »

atoav wrote: post #35
st_goliath wrote: post #6

An other quite interesting concept (also a little less "out there" and actually, successfully tested) is the NERVA engine, also linked at the bottom of the article[1]. It uses a nuclear reactor to heat up a single propellant (liquid hydrogen) which then rapidly expands as it goes out the nozzle at the end, resulting in quite high specific impulse and is more efficient than a chemical rocket. If we want to go really f…

The nuclear salt reactor one is the answer to the question: "How can we make rocket engine testing more dangerous."

We don't have to build/test them on Earth.

Re: Project Orion

#66

Post by katzenversteher »

marktangotango wrote: post #8

There was a classic science fiction story with a twist on this idea; a low tech species was about to be discovered by a more advanced species. And according to the rules of the more advanced species, any planet that wasn't capable of space travel would become a client or vassal, and a planet with space travel would be seen as a peer. The protagonist built a pusher style rocket using an explosive, and launched the lig…

The last book of the Remembrance of Earth's Past series (Death's End), also features a similar concept. They just send a brain into space though and use sails to capture the energy of the nuclear blasts.

Re: Project Orion

#69

Post by neets »

neets wrote: post #68

Ah this is the project that the show Ascension[1] was based on 1. https://m.imdb.com/title/tt3696720/

I sorta hope they literally did what they did in Ascension IRL, does anyone else?

Re: Project Orion

#70

Post by perihelions »

Schroedingersat wrote: post #55
perihelions wrote: post #19

Earlier quoted context omitted.

There's one more: the boring idea of combining a closed, electric-generating nuclear fission system with an (electric-powered) ion engine. Both components being flight tested and not crazy.

What is the specific power of a nuclear reactor + heat engine + crew shielding + radiators? Naval reactors are on the order of a few watts to tens of watts per kg and they have the benefit of unlimited cooling. Seems an order of magnitude short of PV.

Possibly north of 200 W(elec.)/kg [0]. (I can't assess this stuff personally, but it's some MIT person's PhD thesis, so I assume some baseline credibility). Key distinction: you're looking at a conservative kilowatt-scale proposal, one which isn't intended for propulsion. But propulsion-optimized designs are on the megawatt scale: and the mass/power scaling is sub-linear.

[0] https://dspace.mit.edu/handle/1721.1/67559

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