Tripropellant Rocket Using Existing Resources

[Zosma Procyon]

In the real world, tripropellant rockets are the only real avenue left for advancement in chemical fueled rocket technology; the technology and science thereof reached its pinnacle over 50 years ago with the Saturn V and N-1 rockets. Tripropellant rockets, as the name suggests, burn three chemicals rather than the usual two. Rocketdyne built one back in the 60's that burned molten lithium, fluorine, and hydrogen; and produce insane performance. I don't see any reason why a tripropellant motor could be added to the stock game, using existing in-game resources. Ore could stand in for the lithium, liquid fuel for hydrogen, and oxidizer or monopropellant for the fluorine. I'd probably go with monopropellant standing in for fluorine to make things more interesting. Imagine build SSTO rockets that burn ore, monopropellant, and liquid fuel. If I knew how to code, I'd make the flames and smoke different colored.

 

[steuben]

54 minutes ago, Zosma Procyon said:

Rocketdyne built one back in the 60's that burned molten lithium, fluorine, and hydrogen; and produce insane performance.

Yes... it did. Except the exhaust products had a very small drawback. In environment that did not have a negative humidity one of the products would react with any water a produce an acid that would literally dissolve you from the inside out.  And that one of the tanks would have to be held a roughly 200 degrees C above ambient temperature.  

[Zosma Procyon]

2 minutes ago, steuben said:

Yes... it did. Except the exhaust products had a very small drawback. In environment that did not have a negative humidity one of the products would react with any water a produce an acid that would literally dissolve you from the inside out.  And that one of the tanks would have to be held a roughly 200 degrees C above ambient temperature.  

Toxic exhaust is another reason why tripropellant rockets would be in the game. As far as the real world, the environment is already f*cked beyond all hope, so we might as well use them.

Edited January 15, 2019 by Zosma Procyon

[steve_v]

Have you been reading Ignition!, @Zosma Procyon?

Edited January 15, 2019 by steve_v

[Gapone]

LFOMP (liquid fuel, oxidizer, monopropellant) engines?

[Zosma Procyon]

35 minutes ago, steve_v said:

Have you been reading Ignition!, @Zosma Procyon?

Never heard of such a publication. I am a real aerospace engineer, though.

[steve_v]

2 minutes ago, Zosma Procyon said:

Never heard of such a publication.

It's an interesting (and amusing) read, freely available.

3 minutes ago, Zosma Procyon said:

I am a real aerospace engineer

That explains it then. Sounds fun.

[Kerbart]

1 hour ago, steuben said:

Yes... it did. Except the exhaust products had a very small drawback. (...) 

But worth it. Imagine the fun it is to handle a rocket loaded with fluorine. That stuff makes red fuming nitric acid look as benign as gasoline.

[septemberWaves]

Do you happen to know what kind of chemical reaction was involved in the lithium/fluorine/hydrogen rocket? It would be horribly impractical to use something like that in reality, but I am curious about the chemistry; I have little detailed knowledge about how chemical reactions work with more than two unique reagents.

[StrandedonEarth]

3 hours ago, septemberWaves said:

Do you happen to know what kind of chemical reaction was involved in the lithium/fluorine/hydrogen rocket? It would be horribly impractical to use something like that in reality, but I am curious about the chemistry; I have little detailed knowledge about how chemical reactions work with more than two unique reagents.

It was really just burning the lithium with fluorine. The hydrogen was added to boost the ISP to the neighborhood of ~550s, as the key to high ISP is light exhaust products (maximizing exhaust below)

I second the recommendation to read Ignition!, as that’s where I learned about that engine. An interesting and informative read, although some of the chemistry can get a little dry

Edited January 16, 2019 by StrandedonEarth

[Starman4308]

The Li-F-H tripropellant motor is an insane product of 1950s-1960s propellant chemists wondering how far they could push chemical propulsion. Fluorine (and the hydrogen fluoride in the exhaust) is hideously toxic and a potent oxidizing agent (requiring relatively exotic materials to handle). Lithium needs to be at 180C to remain liquid... and likes to react quite vigorously with water. Hydrogen is a very low-density fire risk, but at least we've dealt with it before. Between the safety risks, heavy tank insulation and lithium heating elements, and overall complexity, it's just not worth developing.

Even if we ignore the rise of reusability, there's just no economic reason to develop Li-F-H. Commercial applications, largely bound to GSO or lower-energy orbits, don't need freakishly high specific impulses: the cost of a modestly larger rocket is much less than the cost of developing a nightmare engine. Unmanned scientific applications aren't a big enough market to develop a nightmare rocket, and can largely get by on a combination of hydrolox, solid kick stages, and miniaturized probes. Current manned scientific applications are just LEO taxis. Hypothetical manned scientific applications are likely to either just use a really big hydrolox vehicle, or bite the bullet and go for nuclear-thermal propulsion.

In terms of specific impulse, Li-F-H is only modestly better than hydrolox, and significantly inferior to nuclear-thermal and electric propulsion... neither of which involves having lithium, fluorine, and hydrogen all in the same rocket stage.

With the rise of reusability, well, the cost of handling nightmare fuels becomes an even bigger issue.

 

The tripropellant combinations that actually make sense are kerosene-LH2-LOX or methane-LH2-LOX. Again, marginal improvement, and most agencies have decided to cut development cost by not trying for a relatively complex tripropellant system.

 

In terms of little green people flying rockets over toy-sized solar systems, I don't see why an Li-F-H analogue creates a meaningful game mechanic, other than slightly increasing the difficulty of ISRU operations. I could see a hydrolox analogue (trading lower thrust and much lower fuel density for better specific impulse), and possibly something a liquid fuel-oxidizer-quasihydrogen tripropellant, but an Li-F-H just doesn't seem like it'd help things.

Plus, KSP already has nuclear-thermal rockets, which fit the bill for "really good specific impulse".

[Orc]

Greetings

Generally speaking in the Real World any time someone is speaking about any application for Florine it is time to leave the room (and probably the neighborhood, and perhaps even the city). Florine is horribly dangerous stuff, so reactive that it is found almost nowhere in the Natural Universe (the same place where hideously reactive stuff like hydrogen manages to exist in quantities that defy the common human imagination). 

Even  hydrogen fluoride (hydrofluoric acid) is freaking dangerous. Even in a highly diluted state it will dissolve glass, the usual 'safe' goto for storing acids. At high concentrations it will literally eat your skin, lungs and corneas away faster than your nerves can transmit the pain signals to your brain.

Only a human who is insanely insane Nutjob, or truly ignorant will voluntarily go anywhere near Florine or even concentrated HF. 

When triprop rocketry was discussed of sci.space.tech in the 90s several  real rocket engineers all volunteered their opinion of what other obnoxious oxidizer they'd rather work with. Professionals who worked on the Apollo and Shuttle Program all felt that 99% hydrogen peroxide, fuming red nitric acid, and even the radioactive exhaust of a gas core nuclear engine (https://en.wikipedia.org/wiki/Gas_core_reactor_rocket) were a better option. 

So for the Kerbal-verse handling the stuff is probably a mandatory requirement. But even then only really stupid Kerbals will be happy about the job, and only if encouraged with the promise of lots of snacks. 

 

But seriously from a Game Play point of view what would the benefit be? Someone mentioned up-thread of adding LH-LO engines as a trade-off in performance versus the current LFO engines. Triprops add another fuel tank to the stack, and should for 'realism' purposes result in major damage to the launch pad (and possibly Crawler way) even when the launch goes well. 

Anyway, take care.

 

Regards

Orc

[Tweeker]

I actually did a mod for this a while back,

It was fairly easy to implement, However it did not ever get any real traction, so I stopped work on it.

the parts were just palette swapped and stretched  or squashed regular engines,

I did add a new resource, "florine", But everyone just kept thinking I had misspelled it.

I changed the fuel consumption to  about 2/3rds of the stock ratio, and added about 2/3 of another fuel,  

stock is 9/11,   in the tri-propellant I made it burned 6/6.6/7.3  

It worked fairly well, the new fuel was in tanks that matched with certain stock fuel tanks, so when you built a tri-propellant rock you simply

picked added an extra tank,

here is a screen shot of it in action.  

 

[JadeOfMaar]

I'd rather a stock tri-propellant engine not happen. There are many other means to high thrust with high Isp propulsion that Squad ought to release to us, if anything, all while using bi-propellant or single + EC combinations. Let's discuss the viability of the SSME with a bell extension for vacuum optimization-- that kind of power with any Isp boost, however small, and its small bulkhead size (unlike the Rhino) will speak very loudly to the playerbase. Related, there aren't enough resources in stock to play with: LiquidFuel being abstract and serving in place of Kerosene, Hydrogen, Methane and possibly more; Oxidizer serving as any known, usable oxidating agent, whether actual LOX, or non-cryogenic compounds containing Oxygen.

Using Ore as a propellant is just silly and not in any funny sense. Ore is defined in KSP as top soil, dirt, crust, with everything in it that you extract out of it via ISRU. Therefore, the inherent "impurity" of Ore makes it a horrible choice for use as a propellant.

Edited March 18, 2019 by JadeOfMaar

[Tyko]

On 1/15/2019 at 11:29 AM, Zosma Procyon said:

As far as the real world, the environment is already f*cked beyond all hope, so we might as well use them.

 

On 1/15/2019 at 12:17 PM, Zosma Procyon said:

Never heard of such a publication. I am a real aerospace engineer, though.

It makes me really nervous that a "real aerospace engineer" has such a cavalier attitude about our atmosphere...If you were to break your ankle would you ask the doctor to just chop your leg off since it's beyond all hope?   

On 1/15/2019 at 2:13 PM, septemberWaves said:

Do you happen to know what kind of chemical reaction was involved in the lithium/fluorine/hydrogen rocket? It would be horribly impractical to use something like that in reality, but I am curious about the chemistry; I have little detailed knowledge about how chemical reactions work with more than two unique reagents.

Read Ignition by John Drury Clark - the chemistry is well past my educational level sometimes, but it's written well and even a chemistry novice like me could follow the concepts.

https://www.amazon.com/Ignition-Informal-Propellants-University-Classics/dp/0813595835/ref=sr_1_1?keywords=ignition+book&qid=1553282099&s=gateway&sr=8-1