Nuclear engines could be reality.

[WindShieIds]

Tubes of uranium and plutonium can produce extreme amounts of heat, heat can be used as a source of propulsion.

#NorthKoreanScience

[Kerbart]

Well at the late sixties the NERVA nuclear rocket engine was developed on which the LVN in KSP is based. So it's not a matter of "could", it's a proven concept.

[Kommitz]

This thread is pretty much spam, but... nuclear thermal propulsion is a very real technology that was developed by the Soviets and the USA. Varying reactor prototypes were ground tested during the 60s and 70s.

[cantab]

Yeah, there's no scientific or technological reason we can't have nuclear-powered spacecraft. The barriers are in politics and popular opinion: few people are keen on nuclear reactors on the ground, never mind launching one on a space rocket.

[Rickenbacker]

Nuclear engines are real, have been tested and work very well. Unfortunately, all work on them ceased in the 70's due to political pressure.

[Red Iron Crown]

We've had nuclear engines since the 50s, and nuclear rocket engines since the 60s. It's not exactly news that nuclear energy can be used for propulsion.

[magnemoe]

Yeah, there's no scientific or technological reason we can't have nuclear-powered spacecraft. The barriers are in politics and popular opinion: few people are keen on nuclear reactors on the ground, never mind launching one on a space rocket.

Barrier is mostly economical and practical, as long as you only send probes weighting some hundred kilos nerva is overkill.

Same is true in KSP, unless you payload is heavier than a ton the 48-7S is better. In real world you will also face the problem of storing hydrogen until you want to do your braking burn.

Economical as the concept is tested, not long burns, multiple re-ignitions after a year in space and other practical issues in short you need more development time to verify that it work.

This long term testing has environmental issues who increases costs.

RTG is common in space and they are also reactors the same way as nerva for the uninformed so political it would not be an huge issue to use it.

[Red Iron Crown]

Barrier is mostly economical and practical, as long as you only send probes weighting some hundred kilos nerva is overkill.

Same is true in KSP, unless you payload is heavier than a ton the 48-7S is better. In real world you will also face the problem of storing hydrogen until you want to do your braking burn.

Great thing about NTRs is that they can use just about any fluid for propellant. LH₂ offers the best I_sp, but other, more easily stored fuels are possible and might be desirable for some missions.

Economical as the concept is tested, not long burns, multiple re-ignitions after a year in space and other practical issues in short you need more development time to verify that it work.

This long term testing has environmental issues who increases costs.

Yeah, it's not really tested well enough to put directly into production. A shame it wasn't developed more fully when the political climate was more friendly to nuclear power.

RTG is common in space and they are also reactors the same way as nerva for the uninformed so political it would not be an huge issue to use it.

There were protests over launching New Horizons and Cassini because of the RTGs. I can only imagine what would happen with an NTR.

[magnemoe]

Great thing about NTRs is that they can use just about any fluid for propellant. LH₂ offers the best I_sp, but other, more easily stored fuels are possible and might be desirable for some missions.

Yeah, it's not really tested well enough to put directly into production. A shame it wasn't developed more fully when the political climate was more friendly to nuclear power.

Did not think about alternate fuels, can you do dual use as in do the burn out from LEO with H2 and drop the tanks then switch to say CO2 for the braking burn?

There were protests over launching New Horizons and Cassini because of the RTGs. I can only imagine what would happen with an NTR.

Nothing at all showed up outside of US, in short somebody always protests and media love to show it on slow news days.

The testing might give more reactions than the actual launch, it will also have serious legal issues. Still don't stop Russia or China from developing it and it might be an export article.

[Nibb31]

I'm confused as to what the purpose of this thread is.

[Brotoro]

RTGs are not nuclear reactors. RTGs use the heat from radioactive decay of an isotope, and they use thermocouples to generate electricity from that heat.

[Red Iron Crown]

Did not think about alternate fuels, can you do dual use as in do the burn out from LEO with H2 and drop the tanks then switch to say CO2 for the braking burn?

I would imagine so, though CO₂ has a high molecular weight which reduces I_sp. Nitrogen would be better, helium better still, but I don't know if the storage requirements for those are that much better than hydrogen.

You're right about the protesters, I think. It seems silly to me that there can be fleets of nuclear powered ships, but suggest putting a nuclear powerplant in space and suddenly it's the most dangerous thing ever.

[cantab]

I would imagine so, though CO₂ has a high molecular weight which reduces I_sp. Nitrogen would be better, helium better still, but I don't know if the storage requirements for those are that much better than hydrogen.

Water's cheap, easy to handle, and stores quite densely. It has a relatively low molecular mass, though I don't know what the ISP would be.

You're right about the protesters, I think. It seems silly to me that there can be fleets of nuclear powered ships, but suggest putting a nuclear powerplant in space and suddenly it's the most dangerous thing ever.

Clearly the American people need convincing that nuclear spaceships are an essential weapon to combat China and Russia and remain a global superpower.

On second thoughts, maybe getting the military involved is not such a good idea.

[magnemoe]

I would imagine so, though CO₂ has a high molecular weight which reduces I_sp. Nitrogen would be better, helium better still, but I don't know if the storage requirements for those are that much better than hydrogen.

You're right about the protesters, I think. It seems silly to me that there can be fleets of nuclear powered ships, but suggest putting a nuclear powerplant in space and suddenly it's the most dangerous thing ever.

Nitrogen has fewer problems than hydrogen, my guess is that it should be possible to store liquid nitrogen in space without out-gassing, boiling point is -180, helium is too expensive and also have storage problems.

[Canopus]

I'm confused as to what the purpose of this thread is.

Yesterdays future, presented to you by WindShieIds.

[mdatspace]

And?

This technology existed in the 70s. NERVA ring a bell?

[Red Iron Crown]

On second thoughts, maybe getting the military involved is not such a good idea.

You, sir, have a fine talent for understatement.

As for which propellant is best, I guess it all depends on the mission parameters. Water is nice because it is dense enough to use for radiation shielding and is a consumable that needs to be brought along on manned missions anyway. It's also a good candidate for ISRU on many bodies. Nitrogen has a better Isp while still being easier to store than liquid helium or hydrogen.

It is cool that a NTR gives us those options.

[Northstar1989]

As for which propellant is best, I guess it all depends on the mission parameters. Water is nice because it is dense enough to use for radiation shielding and is a consumable that needs to be brought along on manned missions anyway. It's also a good candidate for ISRU on many bodies. Nitrogen has a better Isp while still being easier to store than liquid helium or hydrogen.

It is cool that a NTR gives us those options.

Don't forget that, with a NTR, lower ISP means higher thrust...

You can also store a greater mass of denser gasses, such as Nitrogen (N2) or Carbon Dioxide, in the same tank volume under the same pressure- which reduces the Dry Mass of your rocket...

Now if only I could convince FractalUK (the KSP-Interstewllar mod creator) to go an include CO2 and N2 as harvestable/storable resources, and allow their use in KSP-I's NTR's... (go bug him to do so for me, if you want to help me out- more voices have a better chance of being heard than just one...)

Regards,

Northstar

Edited May 15, 2014 by Northstar1989

[Northstar1989]

Also, could somebody explain outgassing to me? I still don't understand it...

How can you have loss of a propellent from a sealed fuel tank? Even if a stored liquid turns into a gas, in a closed container, that gas should just stay in place, and accumulate until the increased partial pressure of that liquid prevents further evaporation... How are you losing mass from a sealed container, without any reactions occurring inside? Doesn't that violate the laws of physics?

I guess the containers must not be so tightly sealed- but in that case, isn't the solution just to create an airtight seal on the tanks, and make sure the tank walls can withstand the pressure of the vapors at thermodynamic equilibrium?

Regards,

Northstar

Edited May 15, 2014 by Northstar1989

[Nuke]

i think north korean spies would have trouble recovering the materials from the faked lunar landing to produce the required propaganda space program, since no one in north korea knows how to pull off a fake moon mission.

warning: this post is satire. i know if i dont say it one of you nuts will take it seriously.

[Nibb31]

At the molecular level, everything is porous. H2 is the smallest molecule you can get, so it's very hard to prevent it from passing through another material as the gas expands.

The only way to prevent it from expanding is to keep it liquid, which requires cryogenic cooling, which itself requires quite a lot power and cooling equipment. The other option is to use storable propellants such as RP-1 and hydrazine, but those have less Isp.

Edited May 15, 2014 by Nibb31

[lajoswinkler]

I'm confused as to what the purpose of this thread is.

[Northstar1989]

At the molecular level, everything is porous. H2 is the smallest molecule you can get, so it's very hard to prevent it from passing through another material as the gas expands.

The only way to prevent it from expanding is to keep it liquid, which requires cryogenic cooling, which itself requires quite a lot power and cooling equipment. The other option is to use storable propellants such as RP-1 and hydrazine, but those have less Isp.

We seem to have no trouble preventing Hydrogen from passing through solid aluminum cans on Earth; or O2 supplies from outgassing from the ISS. Why would fuel storage in space space be any different?

For the matter of using propellants with lower vapor pressures (don't forget that even RP-1 undergoes limited evaporation at STP), we're going to have to move to them eventually anyways. It's only a matter of time before to get anything truly useful done in space (such as setting up robotic ISRU infrastructure on the Moon and Mars), we're going to have to rely at least in part on orbital fuel depots to move our heavier payloads...

We should be focusing more on technologies and design solutions for orbital fuel storage, ISRU, and propulsion technologies in the present- rather than sending robotic probes for Planetary Sciences. It's only so long that you can analyze a planet with sensors and rovers before you start running out of useful things to learn with unmanned missions...

Eventually, we're going to have to start paving the way for manned interplanetary exploration, investigation, and colonization... (with a particular focus on ISRU, reusable launch systems, and colony self-sufficiency to bring down long-term costs...)

Regards,

Northstar

[Othuyeg]

It has been done in the fifties.

Project pluto.

[Red Iron Crown]

We seem to have no trouble preventing Hydrogen from passing through solid aluminum cans on Earth; or O2 supplies from outgassing from the ISS. Why would fuel storage in space space be any different?

Because it's hydrogen. O2 and the CO2 in soda cans are both much larger molecules and are thus more easily contained and pressurized. Hydrogen's molecule is the smallest possible, it leaks through any container.