Alternate propellant/remass

[SievertChaser]

So, in the grand tradition of leveraging the experience of other people, I wanted to wonder if someone has gotten good results with combinations other than the dev's stated dominant trifecta of methane, water and methane-fluorine combustion.

Thus far I've only been experimenting with HOOH rather than nitromethane for missiles.

[unwinged]

I use decane sometime for capital ships. But not much reasoning for it...
And Ethylen Oxide for misile, good exhaust velocity for monopropellant.

[Rocket Witch]

I haven't made any engines to use it yet but mercury is very much worth investigating due to its density (= potentially small ships). UHMWPE Hg tanks have mass ratios over 10k. Along the same line of thought, heavy water might be preferable to normal water.

Lithium is strangely missing from the fuel list, afaik it should be another good one if the dev adds it.

[unwinged]

Originally posted by String Witch:

I haven't made any engines to use it yet but mercury is very much worth investigating due to its density (= potentially small ships). UHMWPE Hg tanks have mass ratios over 10k. Along the same line of thought, heavy water might be preferable to normal water.

Lithium is strangely missing from the fuel list, afaik it should be another good one if the dev adds it.

How is mercury in terms of exhaust velocity? From my understaning thrust would be good, but with poor exhaust velocity and delta-V for given mass.

And I think that lithium is not available becouse it is solid and all engines in game use only fluid propellants. Teoretically you could make NTR with lithium propellant but delivering fuel into reactor would be nightmare...

[SievertChaser]

Originally posted by unwinged:

Originally posted by String Witch:

I haven't made any engines to use it yet but mercury is very much worth investigating due to its density (= potentially small ships). UHMWPE Hg tanks have mass ratios over 10k. Along the same line of thought, heavy water might be preferable to normal water.

Lithium is strangely missing from the fuel list, afaik it should be another good one if the dev adds it.

How is mercury in terms of exhaust velocity? From my understaning thrust would be good, but with poor exhaust velocity and delta-V for given mass.

And I think that lithium is not available becouse it is solid and all engines in game use only fluid propellants. Teoretically you could make NTR with lithium propellant but delivering fuel into reactor would be nightmare...

North American Rockwell (IIRC) managed to run a liquid lithium-liquid fluorine-gaseous hydrogen rocket engine long enough to measure the Isp of 542 sec.

And yeah, mercury rockets were considered. Isp would be rubbish, but thrust and dV could be ginormous thanks to the mass ratio.

[unwinged]

Quick look at Wikipedia and it looks like is true. But most of description is listing why it is bad idea.
Simple heating would make lithium liquid and there are cryogenics in game which require cooling, so no big problem here.

Maybe some day it will be added...

[Rocket Witch]

I think the main trouble with the lithium-hydrogen-fluorine tripropellant rocket is the vastly different storage conditions each propellant requires. Lithium needs to be heated, hydrogen needs to be cooled, and fluorine corrodes the tanks. This doesn't seem to be much if any issue in game though, hence the fluorine-methane meta. What's so good about methane, by the way?

Lithium is mainly useful to MPD thrusters; from nasa.gov:
"Lithium-fed MPD thrusters developed in Russia have operated at power levels of 100 kilowatts, with efficiencies of up to 45 percent and plasma exhaust velocities approaching 50,000 meters per second."

Also, I cycled through the propellants a while ago on a stock NTR just to look at all the pretty plumes, and noticed krypton produces blue-hot exhaust. Might work exponentially well in an NTR with a very hot (~3000K) reactor, but I'm not sure what magical substance the chamber would have to be made of.

Originally posted by dennis.danilov:

North American Rockwell (IIRC) managed to run a liquid lithium-liquid fluorine-gaseous hydrogen rocket engine long enough to measure the Isp of 542 sec.

Is there any picture or diagram of this engine or its machinery?

Originally posted by unwinged:

there are cryogenics in game which require cooling

They do? Was that added in a patch? I haven't played for a little over a week.

[unwinged]

Methane is good because of decent Isp and far better storage than hydrogen (no excesive cooling and far better density).

Cryogenics require cooling in real life, in game there is nothing about it.

[Rocket Witch]

So, I've found one of mercury's flaws as a propellant is its density. At least in thermal rockets (nuclear/resistojet) much of the increased thrust it offers is negated by the sheer mass of the rest of the stuff waiting in the tanks.

I've found semiheavy water to be a nice alternative to water, though I dunno if it really counts as much of an alternative, and it seems to perform a lot better (maybe for the same reason deuterium beats out protium). Compared to semiheavy, heavy water offers slightly more thrust and marginally smaller propellant tanks for a slight loss in exhaust velocity, but it's almost interchangeable in a single engine design.

http://steamcommunity.com/sharedfiles/filedetails/?id=785407983


I also made a sodium NTR, noting that the propellant and coolant are one and the same. Results are underwhelming, but I may be doing a great deal wrong.

http://steamcommunity.com/sharedfiles/filedetails/?id=785408061

[SievertChaser]

Apparently, a protium-deuterium (deuteride) molecule does lead to improved performance. Hence it's supposed to be reserved for top-tier NTRs.

[Direwo]

Methane/decane tanks are the sweetspot for ships that actually have a decent amount of armor.
Decent dV, decent g's. Not so large to to require an enormous mass budget for armor.

If you only flash protect ships over all with some extra nose cone protection then MPD's are decent if you can live with 60to80mg accel ratings. 30km/s dV + gigawatt lasers ! ( since you need a Giga reactor for the MPD's ).

[italian_leather_sofa]

Flourine/ammonia is way better than flourine/methane. The exhaust velocity is only about 5% lower, but the stoichiometric ratio for flourine/ammonia heavily favors flourine (6:1 ratio). That's really good for propellant density because flourine is about 3.5 times more dense than methane. Plus, ammonia is also denser than methane (about 50%).

If that wasn't enough, the adiabatic flame temperature of flourine/ammonia is about 3000 K cooler than flourine/methane.

[SievertChaser]

Ammonia just looks more and more attractive for everything... And I love the red exhaust from ammonia NTRs.

[Celestite]

i am still wandering there isnt chlorine trifloride engines

[SievertChaser]

Originally posted by celestite:

i am still wandering there isnt chlorine trifloride engines

Not enough white papers? Same as the Orion drive.