Author Topic: tripropellant rockets  (Read 46920 times)

Offline C-300

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Offline GraphGuy

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Re: tripropellant rockets
« Reply #41 on: 03/24/2009 08:38 pm »
http://www.wickmanspacecraft.com/loxmono.html

Check this out, these guys are mixing LOX with kerosene at cryogenic temps to create a 'monopropellant'. Dont know how stable this mixture is, but it could save some tankage mass if you only need one tank, and making it pressure fed, eliminate turbopumping, you'd have the liquid equivalent of a solid rocket motor. Comments?

Wouldn't mixing fuel and oxidizer in this manner turn the liquid engine into a bomb waiting to explode, even worse than a solid motor?  This would greatly increase your LOC numbers.  Also you might have problems if the density of LOX and cryogenic RP vary as you may have some settling when accelerating at multiple Gs.  If the fuel or the oxidizer floats to the top then you are in serious trouble.

Offline mlorrey

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Re: tripropellant rockets
« Reply #42 on: 04/01/2009 09:56 pm »
http://www.wickmanspacecraft.com/loxmono.html

Check this out, these guys are mixing LOX with kerosene at cryogenic temps to create a 'monopropellant'. Dont know how stable this mixture is, but it could save some tankage mass if you only need one tank, and making it pressure fed, eliminate turbopumping, you'd have the liquid equivalent of a solid rocket motor. Comments?

Wouldn't mixing fuel and oxidizer in this manner turn the liquid engine into a bomb waiting to explode, even worse than a solid motor?  This would greatly increase your LOC numbers.  Also you might have problems if the density of LOX and cryogenic RP vary as you may have some settling when accelerating at multiple Gs.  If the fuel or the oxidizer floats to the top then you are in serious trouble.

Technically, oxidation can only happen with both fuel, oxidizer, and HEAT. Cryogenic mixing of fuel and oxidizer LIQUID is theoretically nonflammable without a heat source or other form of shock (shock wave, electric arc, etc). You need to turn liquids into vapors (i.e. add heat) before you can ignite them anyways. Rocket engine combustion chambers are just very very efficient at doing this very quickly.
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Offline mars sts-107

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Re: tripropellant rockets
« Reply #43 on: 06/06/2009 02:26 pm »
I have been reading about of Wikipedia.
( http://en.wikipedia.org/wiki/Tripropellant_rocket )

It says - A mixture of lithium, hydrogen, and fluorine produced a specific impulse of 546 seconds; the highest ever of any chemical rocket motor.

An Isp of 546 is high enough to design a signal stage to orbit vehicle SSTO. Does anybody know, why an engine for this combination of fuel not being developed?


The propellants and exhaust are extremely toxic.

monomethal hydrozine and nitrogen tettroxide are toxic too and they use them

Offline Jim

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Re: tripropellant rockets
« Reply #44 on: 06/06/2009 04:11 pm »
I have been reading about of Wikipedia.
( http://en.wikipedia.org/wiki/Tripropellant_rocket )

It says - A mixture of lithium, hydrogen, and fluorine produced a specific impulse of 546 seconds; the highest ever of any chemical rocket motor.

An Isp of 546 is high enough to design a signal stage to orbit vehicle SSTO. Does anybody know, why an engine for this combination of fuel not being developed?


The propellants and exhaust are extremely toxic.

monomethal hydrozine and nitrogen tettroxide are toxic too and they use them

Not as toxic or hard to handle as flourine.

Offline mboeller

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Re: tripropellant rockets
« Reply #45 on: 06/16/2009 09:01 am »
here is a nice german website with informations about exotic tripropellant fuels:

http://www.bernd-leitenberger.de/raktreib3.shtml

the given exhaust velocities are not 100% correct but calculated with the program FCEA2. A comparison between FCEA2 results and real exhaust velocities can be seen in table1 .

Kapitel 7 shows mixtures of fuel
Kapitel 8 shows mixtures of oxidators
Kapitel 9 shows tripropellant and even fourpropellant (2x oxidator, 2x fuel) mixtures.
« Last Edit: 06/16/2009 09:05 am by mboeller »

Offline neph

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Re: tripropellant rockets
« Reply #46 on: 01/31/2020 08:44 am »
Necroing this thread to bring up another type of tripropellant...

There has been a [lot of research](https://www.intechopen.com/books/hydrogen-energy-challenges-and-perspectives/use-of-hydrogen-methane-blends-in-internal-combustion-engines) in H2-CH4 mixtures recently, but it's all in internal combustion studies. I've been thinking about a premixed LH2-LCH4-LOX rocket engine.

I suspect the benefits compared to either pure methalox or hydrolox include the elimination of the already limited coking of methane combustion, Isp increases compared to pure methalox, better properties for regenerative cooling than methalox, lower boiloff than pure hydrolox, and clearly substantial density improvements over hydrolox. Of course, I'm sure there's plenty of issues, such as the fact that your mixed fuel is probably more of a slurry than a mixture at the cryogenic temperatures that such a solution would require. Nonetheless, I wonder if the advantages wouldn't make it worth it.

Has any research been put into such an propellant system? If not a premixed fuel, what about a proper tripropellent system with a three-fluid injector plate?

Offline Seamurda

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Re: tripropellant rockets
« Reply #47 on: 02/01/2020 06:33 pm »
I've seen very many references to Salkelds papers on Tri propellant engines.

Does anyone have any copies of any of them?

Offline tj

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Re: tripropellant rockets
« Reply #48 on: 02/01/2020 07:27 pm »
Lockheed Agena and Bell engine (second stage & space vehicle) experimented with liquid flourine engines with some testing at the Lockheed 4000 acre Bonny Dune, Santa Cruz, CA test facility.

Some info on the web..

"Bell liquid flourine engine


https://www.abbottaerospace.com/wp-content/uploads/2017/08/naca-rm-e53j20-Preliminary-Investigation-of-Performance-and-Starting-Characteristics-of-Liquid-Fluorine-Liquid-Oxygen-Mixtures-with-1-250x296.jpg

PART III : 1958-1959
10. Early High-Energy Upper Stages
Legacy of Suntan
https://history.nasa.gov/SP-4404/ch10-2.htm

ended up with hydrolox... to P&W then to GD (ended up with Centaur)


https://history.nasa.gov/SP-4404/ch10-2.htm
Lockheed was interested in hydrazine - flourine engine


paper
Handling Liquid Flourine in Rocket Applications
A. R. Kimball
Bell Aircraft Corporation

Kimball A.R. (1960) Handling Liquid Fluorine in Rocket Applications. In: Timmerhaus K.D. (eds) Advances in Cryogenic Engineering. Advances in Cryogenic Engineering, vol 5. Springer, Boston, MA
https://link.springer.com/chapter/10.1007/978-1-4757-0537-9_9

Offline Proponent

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Re: tripropellant rockets
« Reply #49 on: 02/01/2020 08:08 pm »
Fluorine, please, not flourine.

Sorry -- it's a pet peeve of mine.

Offline gin455res

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Re: tripropellant rockets
« Reply #50 on: 02/02/2020 09:36 pm »
I just did a 'back of the envelope' calculation that suggests a LOX ethanol/gasoline (E60) blend might have roughly the same Oxidiser/Fuel  ratio (by volume) as LOX/methane but it would be about 18% heavier.

I wonder if this or something similar like sub-cooled E60 but with propane or butane (not gasoline), might make an okay tri-propellant with methane and LOX?

Could a single gas-generator be used for both fuels during a launch?

How would it coke?

Would E60-ish make for a more or less economical gas-generator fuel?

If the industry is now comfortable with 37 engines on a booster, could one set of high thrust engines and another set high isp engines be employed together on a first-stage - (if the engine cannot switch fuels in flight)?


Or perhaps the E60-ish variant of the engine might be used on the booster and the methane variant on the upper-stage. Perhaps, giving a falcon 9 (or  Electron) equivalent but with less coking and better re-usability on the booster.

Offline Genial Precis

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Re: tripropellant rockets
« Reply #51 on: 02/05/2020 04:12 pm »
The thing is, methane is so hydrogen-rich that its Isp is substantially better than other hydrocarbons, burned with oxygen. Check out this 1986 survey of tripropellant concepts; it hasn't lost much relevance. Li and Be are too rare to be viable. Al and Si are the only thing competitive with H for burning with O. If you could densify methane or hydrogen by cheaply cramming them full of one of those, in a way that allowed such a good engine as Raptor to operate, preferably without complicating injection (unacceptably, I think) by turning them into gels, you could make a more compact (hence lighter, more payload) Starship/Superheavy.

Any substantial improvement from there basically involves a scramjet or nuclear thermal I think. And Starship has the potential to be so big and cheap that those are tough asks.

Offline edzieba

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Re: tripropellant rockets
« Reply #52 on: 02/06/2020 10:12 am »
For the "low-ISP-high-thrust fuel for takeoff only" tripropellant variant, it may make more sense to go the Thrust Augmented Nozzle route, rather than muck about trying to get an extra propellant injected into the main combustion chamber (or worse, try and massage it through the same propellant lines and turbomachinery).
« Last Edit: 02/06/2020 10:19 am by edzieba »

Offline Genial Precis

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Re: tripropellant rockets
« Reply #53 on: 02/06/2020 06:37 pm »
Al can't really be used as a separate propellant, to the best of my knowledge. You'd have to load it into the methane somehow. Which isn't exactly a tripropellant, but people have discussed mixtures here. And the point of using Al is that it's the only thing you can load into methane that doesn't reduce the Isp at all, and that works up to 67% by mass.

That said, I think it would increase the exhaust temperature, because Al2O3 isn't a gas and contributes nothing to thrust. To keep same Isp the other products need to move faster=hotter. Not sure if Raptor engines conceivably have room for that.

Offline gin455res

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Re: tripropellant rockets
« Reply #54 on: 03/11/2020 04:06 pm »
I think I read on here, that the cubed square law means that as rocket engines get larger they need less cooling.

Could tri-propellants take advantage of this once a certain size engine is reached by using only one fuel for both cooling and in the pump gas-generator?

For example, if the engine ran on LOX, kerosene and alcohol, could it reach a size where only the alcohol is needed for cooling (here the tri-propellant is purely used to improve re-usability by eliminating coking, not for density advantages)?

Offline Nilof

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Re: tripropellant rockets
« Reply #55 on: 03/19/2020 05:37 pm »
If you are going for hazardous rockets, my personal favorite is the pebble bed nuclear thermal rocket with LH2 as the ejection mass ala Project Timberwind. T/W ratio of 30 and 890 Isp at sea level. LN or CO2 as the ejection mass would increase thrust at cost of Isp. It isn't very different from a pebble bed nuclear reactor. Many countries have the technology required, including China.


That engine may be too dangerous for an LV but it would rock for a lunar shuttle no more launching a new EDS for every lunar mission just refuel the nuclear ferry.

Also with a T/W that high if it can throttle deeply and quickly it would make a good lunar lander engine too.

NTR for a lunar shuttle is not really a good idea either because the logistics are a PITA.

In vacuum, neutron radiation goes down as an inverse square law instead of exponentially with distance, and mostly unshielded multi-gigawatt nuclear reactors are REALLY neutron-bright during engine burns. Everyone in a lunar bases that it flies over or lands next to has to go into a radiation shelter.

On top of it, you only get an ISP advantage if all your reaction mass is hydrogen... which is the only thing which is in really short supply on the surface of the moon. If you have an oxygen source which is trivial for the moon, then hydrolox ISRU uses hydrogen from earth much more efficiently.

EDIT: holy necroposting
« Last Edit: 03/19/2020 05:38 pm by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Nilof

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Re: tripropellant rockets
« Reply #56 on: 03/19/2020 05:39 pm »
I think I read on here, that the cubed square law means that as rocket engines get larger they need less cooling.

Could tri-propellants take advantage of this once a certain size engine is reached by using only one fuel for both cooling and in the pump gas-generator?

For example, if the engine ran on LOX, kerosene and alcohol, could it reach a size where only the alcohol is needed for cooling (here the tri-propellant is purely used to improve re-usability by eliminating coking, not for density advantages)?

RD-701 used hydrogen and no RP-1 for cooling iirc, though someone might correct me.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Proponent

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Re: tripropellant rockets
« Reply #57 on: 03/19/2020 08:34 pm »
RD-701 used hydrogen and no RP-1 for cooling iirc, though someone might correct me.

I don't know, but on first principles, that might make sense.  The molar heat capacity of hydrogen may not be far off that or RP-1, meaning that the mass-specific heat capacity of hydrogen would be much higher.

Offline john smith 19

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Re: tripropellant rockets
« Reply #58 on: 03/21/2020 09:16 am »
I have been reading about of Wikipedia.
( http://en.wikipedia.org/wiki/Tripropellant_rocket )

It says - A mixture of lithium, hydrogen, and fluorine produced a specific impulse of 546 seconds; the highest ever of any chemical rocket motor.

An Isp of 546 is high enough to design a signal stage to orbit vehicle SSTO. Does anybody know, why an engine for this combination of fuel not being developed?


The propellants and exhaust are extremely toxic.
That pretty much sums up exactly why no one has built a vehicle to fly it.

You're also needing to handle both LH2 at -253c and Lithium at +180c before they start mixing together.  Burning it will give you HF which will react with any atmospheric water vapor to form hydroflouric acid which is used to etch glass.

Should you be interested in a viable tripropellant engine then later this year Reaction Engines Limited will start ground test of SABRE. As it runs on air/LH2/LOX it also is a tripropellant design but instead of switching fuels (the normal change) it switches oxidizers.

Air breathing Isp will be somewhere north of 3000 secs.
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Offline RanulfC

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Re: tripropellant rockets
« Reply #59 on: 06/05/2020 09:15 pm »
If you are going for hazardous rockets, my personal favorite is the pebble bed nuclear thermal rocket with LH2 as the ejection mass ala Project Timberwind. T/W ratio of 30 and 890 Isp at sea level. LN or CO2 as the ejection mass would increase thrust at cost of Isp. It isn't very different from a pebble bed nuclear reactor. Many countries have the technology required, including China.


That engine may be too dangerous for an LV but it would rock for a lunar shuttle no more launching a new EDS for every lunar mission just refuel the nuclear ferry.

Also with a T/W that high if it can throttle deeply and quickly it would make a good lunar lander engine too.

NTR for a lunar shuttle is not really a good idea either because the logistics are a PITA.

In vacuum, neutron radiation goes down as an inverse square law instead of exponentially with distance, and mostly unshielded multi-gigawatt nuclear reactors are REALLY neutron-bright during engine burns. Everyone in a lunar bases that it flies over or lands next to has to go into a radiation shelter.

On top of it, you only get an ISP advantage if all your reaction mass is hydrogen... which is the only thing which is in really short supply on the surface of the moon. If you have an oxygen source which is trivial for the moon, then hydrolox ISRU uses hydrogen from earth much more efficiently.

I think the 'ferry' is an orbit-to-orbit not a lander just FYI, I don't recall any suggestions, (serious ones anyway) for a lander. (Hence the "EDS" or "Earth Departure Stage" which in itself is "incorrect" since it would be E/LDS I suppose... :) )

Of course we now know that the pebble bed has worse internal drag than the NERVA and lower ISP than expected and they still had issues with uncontrolled hot-spots.. Eh we keep working on it :)

Quote
EDIT: holy necroposting

Ya, I actually started from the most recent and thought to review and WOW.. :)

Randy
[/quote]
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British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

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