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Nuclear Rockets [WIP]

Kommitz

By Kommitz
in KSP1 Mod Development

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Gaius

Gaius

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These work like the stock LV-N engine, using the regular LFO mixture for fuel. That's wrong, but until Squad makes the game actually do NTRs right, it's probably best to just stay compatible with stock...

What I don't understand is, why didn't Squad just make the LV-N use liquid fuel alone? Using the same fuel as a jet engine isn't realistic either, but it's less unrealistic than requiring that same liquid fuel and an oxidizer on an engine that doesn't actually "burn" its fuel.

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Kommitz

Kommitz

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I had a simple explanatory diagram on spaceport for my old release:

guidesheet.jpg

They have a nuclear reactor in place of the oxidiser.

Chemical rockets extract energy from their propellant by oxidising(burning) it quite vigorously. Basically this makes everything really hot/energetic and causes everything to expand out the back at great velocities.

Nuclear rockets, instead of oxidising the propellant to generate the heat, run it straight through a high power nuclear reactor. Basically this makes the propellant really hot and expand vigorously out the back. So they don't need the oxidiser.

(Nuclear reactors are usually not spherical, and technically the ones in my engines aren't but I think spheres look spacey so eh.)

Not as wrong as you think. Looks like Squad just did a little research and found an NTR that uses both hydrogen and oxygen:

http://www.projectrho.com/public_html/rocket/enginelist.php#lantr

That's a bit different though, it's supposed to be a tradeoff between efficiency and thrust whereas the LV-N just runs at an improbably high Isp (for the propellants used) in one mode.

I like it too. Does it still works as RTG? It would save even more weight :)

Eh, no. I might make it do that if I can find a plugin to switch between engine/power generation mode.

Edited by Kommitz
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Starwaster

Starwaster

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Not as wrong as you think. Looks like Squad just did a little research and found an NTR that uses both hydrogen and oxygen:

http://www.projectrho.com/public_html/rocket/enginelist.php#lantr

LANTR LO2 mode is optional. Like high and low gears. Meant to be used when thrust is more important than Isp.

The LVN is NOT a LANTR. It runs that way all the time and its Isp is way too high to be a LANTR running in LO2 mode. (a value of about 647 would be a lot closer for a LANTR running on O2 which it actually injects into the propellent stream as it passes into the nozzle)

The truth is that they didn't want to make a new fuel tank. They say as much in a comment found in the part.cfg file for the LVN


	// Yes, I know this is wrong. NTRs don't actually burn fuel and oxidizer, but we don't want to jump into making separate tanks for the two yet.

Its stats also are closer to the old Pewee NTRs test fired back in the 60s.

Edited by Starwaster
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Gaius

Gaius

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Right. They don't need an oxidizer because they don't actually "burn" their fuel, they just heat it and expell it. It's not really "fuel" at all, it's reaction mass. That said, hydrogen is commonly used for this, and it's also commonly used as liquid fuel in many bipropellant rockets, so the case could be made for simply using liquid fuel tanks for the nuclear engines in-game. But they didn't do that. This is nice, in that we can use all the game's normal tanks this way, but a better solution would be to use the right "fuel" for the engine, and make tanks configurable -- you pick what you want to put in the tank in the VAB. Haven't you ever wanted a big orange tank full of monopropellant? No? Well, anyway, that'd be the ideal solution. Maybe we'll get that someday down the road...

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sojourner

sojourner

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LANTR LO2 mode is optional. Like high and low gears. Meant to be used when thrust is more important than Isp.

The LVN is NOT a LANTR. It runs that way all the time and its Isp is way too high to be a LANTR running in LO2 mode. (a value of about 647 would be a lot closer for a LANTR running on O2 which it actually injects into the propellent stream as it passes into the nozzle)

The truth is that they didn't want to make a new fuel tank. They say as much in a comment found in the part.cfg file for the LVN


	// Yes, I know this is wrong. NTRs don't actually burn fuel and oxidizer, but we don't want to jump into making separate tanks for the two yet.

Its stats also are closer to the old Pewee NTRs test fired back in the 60s.

Yep, I knew all that. Regardless, if you need to justify how the current game works you can just picture the current LV-N's as LANTR.

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Kommitz

Kommitz

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Any plans to make a 3.75M Version of your engines?? After your done with the current ones of course....

Maybe...

Working on the FTmN 100 now. Or maybe 160, or some other number inbetween.

Going with a slightly different style for variety and to suggest a wee bit of technological progression. FTmN pack should soon contain this, the tiny radioisotope engine and the two that are currently in it.

7eSMU6k.jpg

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regex

regex

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FTmN pack should soon contain this, the tiny radioisotope engine and the two that are currently in it.

Awesome, I can't wait. You've got some fantastic artistic ability and I have greatly enjoyed using your engines.

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Kommitz

Kommitz

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Fixing up the emissives on current parts, testing things out for new parts in the process. I've also considered adding in some lights (in unity) so your rocket exhaust can illuminate things but decided that might detract from the already limited light allowance.

ABktKLL.png

SuXTYWG.png

Slowly unwrapping the FTmN 160. Will probably be another week or two.

I've also been working on my large hydrogen tanks and things, and CFG conversions for my nuclear engines to use them, along with another unrelated set of parts for a particular historical project that'll see the light of day eventually. Someone can try to guess it if they want, here's the first stage engine shroud:

x8Y5A4y.jpg

Edited by Kommitz
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longhornchris

longhornchris

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Right. They don't need an oxidizer because they don't actually "burn" their fuel, they just heat it and expell it. It's not really "fuel" at all, it's reaction mass. That said, hydrogen is commonly used for this, and it's also commonly used as liquid fuel in many bipropellant rockets, so the case could be made for simply using liquid fuel tanks for the nuclear engines in-game. But they didn't do that. This is nice, in that we can use all the game's normal tanks this way, but a better solution would be to use the right "fuel" for the engine, and make tanks configurable -- you pick what you want to put in the tank in the VAB. Haven't you ever wanted a big orange tank full of monopropellant? No? Well, anyway, that'd be the ideal solution. Maybe we'll get that someday down the road...

Yeah, except monopropellant on real spacecraft is typically a variant of hydrazine which can be used as both a monoprop or a hypergolic biprop using nitrogen tetroxide as an oxidizer. As a monoprop, a catalyst is used to cause the hyrdrazine to decompose energetically. This is not what you want as reaction mass for a nuclear engine.

Hydrogen is nice because it provides the best thermal ISP being a light molecule thus the most kinetic energy for a given thermal energy. That said, H2 is tough to store and causes hydrogen embrittlement so there may be other options. Using an oxidizer would just be bad though as the reactor core in the NERVA design has lots of graphite as a moderator.

I think, given that there is now Fuel (Jet), Fuel/Ox, Monoprop, and Xe (and that's just stock) I think its time to add in Nuke fuel... force people to make harder design decisions.

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Kommitz

Kommitz

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WoooOOOooOOOOoo ghOSt tHReaD comes back to haunt you all

Could you possibly do a tri or quad Nuclear engine? I'd think that'd look cool.

x97T22E.png

I'm making a stockalike 4-nuke-cluster now that we've got 3.75m stock parts, you're in luck! Very late luck.

Briefly faced down the dilemma of whether I should just make a bigger engine and decided that symmetrical clusters look cool and suit the game.

What I really wanted to post was this, which I'm fixing up for the chaka monkey mod conglomeration thing:

57nGpd4.jpg7QS2wk0.jpg

Based on dimensioned NERVA II design illustrations. It's huge. That means it has huge thrust.

Most of the height is in the massive exhaust nozzle which puts it at about the same height as an orange tank, and believe it or not it's been scaled down (0.64x) to Kerbal size. I'll probably release a real-scale version too because I know there are nutters out there that like playing with such things.

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Yilmas

Yilmas

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http://i.imgur.com/x97T22E.png

I'm making a stockalike 4-nuke-cluster now that we've got 3.75m stock parts, you're in luck! Very late luck.

Briefly faced down the dilemma of whether I should just make a bigger engine and decided that symmetrical clusters look cool and suit the game.

I would love to see these in action. I've been hunting down a 3.75m and 5m nuclear engine for a long time. Finally somebody shows sign of one.

Especially like the symmetrical style you have going there.

Need it to power my mothership/carrier.

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LameLefty

LameLefty

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WoooOOOooOOOOoo ghOSt tHReaD comes back to haunt you all

Oh dear $DEITY, thank you! The FTmN-280 is my favorite engine in the game period, stock or mod. But I need a better "fit" for 3.75m parts and larger spacecraft. That quad-cluster awesome, as does the NERVA II. I'm looking forward to seeing the final versions!

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