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What Real Fuels would you Expect the Stock Engines run on?


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I've been playing a lot of RSS/RO lately and I just hopped over from that save to my stock one and got to wondering what each engine likely burns. The game only uses the default Liquid Fuel and Oxidizer mix but we can assume to some extent that this can mean anything from Kerosene and Oxygen (also know as RP-1 or Kerolox), Hydrogen and Oxygen (or Hydrolox), or even more unique combinations. The same goes for the RCS engines and vernors. We can make some speculations based on how the engine behaves, it's statistics and it's plume (stock and RealPlume).

Sadly this is much of a Real Fuels discussion, but if you have something to add, then please do! :D

I'll add a graph with all the engines and make it clear what is what later once the discussion goes.

So what do you think? I might be mistaken in some parts, so please correct me if I'm wrong.

Personally, just starting off, I'd say that the Mainsail burns Kerolox because it's very much the same as real life large scale engines, the LV-30 and 45s would also burn Kerolox. The Mammoth and the large 5m engines along with the skipper would all burn Hydrolox as the real basis for the Mammoth and J-2 rocket engines in real life (so I believe) burn the mix. The LV-909 would burn the same mixture as the real life Lunar Module Descent engine. The Spark would burn UDMH and NTO and the Ant engine would burn Aerozine (pressurized). I get the odd feeling the Poodle engine would be Kerolox even though it might use some other mixture. The space shuttle main engine and the aerospike would both also be Hydrolox. The Thud radial booster would likely be Kerolox(?), that one I am uncertain about and will have to leave up to discussion. The Puff radial monopropellant engine would likely burn a monopropellant (of course) such as Hydrazine, HTP, MMH+NTO (etc). All the aircraft engines would burn Kerosene as do real aircraft. The Twin Boar engine would likely be a Kerolox mixture. The Xenon engine would obviously use Xenon. All of the solid rocket engines would burn PSPC as do most real life solid rocket boosters. Lastly the RAPIER engine would be a mix of Kerosene for the airbreathing stage and Hydrolox for the second stage like the aerospace. The LV-N engine would be a mix of some radioactive material and some hydrogen I'm guessing.

These are just my thoughts.

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They all run on Aerozine50 and N2O4, with hydrazine for the RCS.  The isps and hsp of the fuels match up.  The nuclear engine and the jet engines are the odd balls but KSP is too simple for that to be otherwise.

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1 hour ago, regex said:

They all run on Aerozine50 and N2O4, with hydrazine for the RCS.  The isps and hsp of the fuels match up.  The nuclear engine and the jet engines are the odd balls but KSP is too simple for that to be otherwise.

Well outside of the ISPs, they're plumes are too unique to be a single propellant. 

Granted it's a good point for some.

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If the RAPIER is based of on Skylon's SABRE engines, then it would burn Hydrogen in airbreathing mode(by adding atmosphere intake air as oxidiser)...and in rocket mode it just adds the Oxidizer from onboard. A bit oversimplified, but yes, it uses Hydrogen like other aircraft uses Kerosene, that's awesome!

The Lunar Decent Stage, did it use a Hypergolic mixture, or was that only for the Ascent stage? I know they stressed about the reliability of an engine on/around the Moon. It is the only ticket back home.

LV-N engines use LH2 (liquid hydrogen) if the NERVA engine is anything to go by. I don't think the reactor core loses radioactive material, but if the core has a short half life, it might need to be replaced after some time

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8 hours ago, Blaarkies said:

If the RAPIER is based of on Skylon's SABRE engines, then it would burn Hydrogen in airbreathing mode(by adding atmosphere intake air as oxidiser)...and in rocket mode it just adds the Oxidizer from onboard. A bit oversimplified, but yes, it uses Hydrogen like other aircraft uses Kerosene, that's awesome!

The Lunar Decent Stage, did it use a Hypergolic mixture, or was that only for the Ascent stage? I know they stressed about the reliability of an engine on/around the Moon. It is the only ticket back home.

LV-N engines use LH2 (liquid hydrogen) if the NERVA engine is anything to go by. I don't think the reactor core loses radioactive material, but if the core has a short half life, it might need to be replaced after some time

I am familiar with the SABRE engine.

The LV-N likely does burn LH2 considering it's based on the real life engine.

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10 hours ago, regex said:

They all run on Aerozine50 and N2O4, with hydrazine for the RCS.  The isps and hsp of the fuels match up.  The nuclear engine and the jet engines are the odd balls but KSP is too simple for that to be otherwise.

This. The important numbers match up (aside from the slightly magical nuke and jets).

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9 minutes ago, Red Iron Crown said:

This. The important numbers match up (aside from the slightly magical nuke and jets).

Then what explains the varible plumes? Cool the numbers back it, but I'm after a better answer. 

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5 minutes ago, ZooNamedGames said:

Then what explains the varible plumes?

It's explained by the original VFX makers not knowing a ton about real rockets, if I'm brutally honest. Just look at how the plumes stay underexpanded in vacuum.

5 minutes ago, ZooNamedGames said:

Cool the numbers back it, but I'm after a better answer. 

Numbers *are* the best answer. Cosmetics are just that, cosmetics; it's performance that is important IMO.

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28 minutes ago, Red Iron Crown said:

This. The important numbers match up (aside from the slightly magical nuke and jets).

What is magical about the nuke? At least measured to RO's nuclear engines the numbers seem fine. Aside of course from the LF.

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1 minute ago, Temeter said:

What is magical about the nuke? At least measured to RO's nuclear engines the numbers seem fine. Aside of course from the LF.

The nuke's stats are clearly for a hydrogen NTR but the fuel, when used in every other engine, behaves like Aerozine 50. Magic. :)

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16 minutes ago, Red Iron Crown said:

The nuke's stats are clearly for a hydrogen NTR but the fuel, when used in every other engine, behaves like Aerozine 50. Magic. :)

All the fuel behaves magic. No ullage at all. :wink:

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12 minutes ago, Red Iron Crown said:

The tanks are so heavy because they're all pressurized bladder tanks, of course. *puts fingers in ears* :D

My 6.000 ton pressurized bladder might want to have a word with u. :3

Also, my other bladder wants me to go to the next toilet.

Edited by Temeter
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57 minutes ago, Red Iron Crown said:

The nuke's stats are clearly for a hydrogen NTR but the fuel, when used in every other engine, behaves like Aerozine 50. Magic. :)

That's why I use conventional rocket tanks drained of Oxidizer for powering my LV-N's.  To my mind, the additional empty volume would be where the less-dense Hydrogen volume would need to occupy for an NTR-powered ship.  As @Rune puts it, I "self-impose challenges" on myself. :P

I have no idea if the actual volumes would be accurate (probably not), I don't care to get that in-depth into the real-life comparisons.

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Something silly like osmium+ozone, which might explain the commonality of rapid unplanned disassemblies. I expect Kerbals are immune to a lot of toxic effects and economic considerations, and just pack the most volatile stuff they can find into their next rocket.

What would happen if you shot xenon+oxidiser out of a regular rocket engine? Would be interesting if there were a mod that let you combine any fuels in any engine and enjoy the (probably underwhelming) results.

Edited by Guest
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1 hour ago, String Witch said:

Something silly like osmium+ozone, which might explain the commonality of rapid unplanned disassemblies. I expect Kerbals are immune to a lot of toxic effects and economic considerations, and just pack the most volatile stuff they can find into their next rocket.

What would happen if you shot xenon+oxidiser out of a regular rocket engine? Would be interesting if there were a mod that let you combine any fuels in any engine and enjoy the (probably underwhelming) results.

That's a good point-

Aerozine50 and N204 sounds like a hyperbolic mixture, how would that explain the explosions seen in KSP? 

2czhCAB.jpg

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22 minutes ago, ZooNamedGames said:

Aerozine50 and N204 sounds like a hyperbolic mixture, how would that explain the explosions seen in KSP? 

How wouldn't it?  Hypergolics violently react when they come in contact.  Ever seen a Протон explode?  Look it up.

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6 minutes ago, regex said:

How wouldn't it?  Hypergolics violently react when they come in contact.  Ever seen a Протон explode?  Look it up.

However when released from their containers they have no reason to explode except in small groups where they do collide but such explosions would push the materials away from each other making the explosions less likely.

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27 minutes ago, ZooNamedGames said:

That's a good point-

Aerozine50 and N204 sounds like a hyperbolic mixture, how would that explain the explosions seen in KSP?

As regex said, the main characteristic of hypergolic fuels is that they ignite when put together. Plus side: you don't need fancy ignition mechanisms (some cryogenic engines are actually ignited by small amounts of hypergolics), other side: easy booms.

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3 minutes ago, ZooNamedGames said:

However when released from their containers they have no reason to explode except in small groups where they do collide but such explosions would push the materials away from each other making the explosions less likely.

Yeah, that's totally what's happening in this video...  :rolleyes:

Протон is 693 tons of UDMH/N2O4 fueled heavy lifting.  Aerozine50 is basically a hydrazine/UDMH mix, so what you're seeing in the video is typical of KSP rockets.

Edited by regex
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3 minutes ago, regex said:

Yeah, that's totally what's happening in this video...  :rolleyes:

 

The fuel tanks themselves remained intact throughout until impact which forced the hyperglolic materials into a small area which is more likely to explode, I'm referring to in flight explosions which is less likely unless it's a self oxidizing propellant or a liquid propellant.

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Just now, ZooNamedGames said:

The fuel tanks themselves remained intact throughout until impact which forced the hyperglolic materials into a small area which is more likely to explode, I'm referring to in flight explosions which is less likely unless it's a self oxidizing propellant or a liquid propellant.

Oh, we're talking in-flight explosions?  The picture you posted was a ground impact.  How often do you get in-flight explosions?  Are they fuel-related or something else, like reentry heat-related?

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