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.
A second design series studied the replacement of the Shuttles SRBs with tripropellant based boosters, in which case the engine almost halved the overall weight of the designs.
Quote from: space_dreamer on 02/05/2009 02:28 pmI 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? Because the propellants are a royal PITA to handle.Fluorine is extremely toxic and corrosive. It reacts with just about everything so only a few metals are suitable for containing it. It is hypergolic with most fire-extinguishing agents. There is no effective way to put out a fluorine fire.Liquid lithium is hypergolic with air. Also horribly corrosive. There are no flexible materials (e.g. gaskets) that can survive liquid lithium; all joints must be welded.The lithium fluoride in the exhaust would cause environmental problems. It's worse than SRB exhaust.
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.
And of course, if you want to go completely crazy, there's liquid ozone 15...
And of course, if you want to go completely crazy, there's liquid ozone 15 and acetylene. But I'll let the co-author of that tongue-in-cheek proposal describe it himself:http://groups.google.com/group/sci.space.tech/msg/3199d5be7e770f44(The rest of the thread is worth reading, for tips on making the acetylene radioactive, etc...)
Is it possible that there is a propellant combo out there which hasn’t be discovered yet that would produce a Isp over 500 and be non toxic and relative easy to work with? Or has every combination been tried?
The MAKS concept looks ideal - but why would the Russian have been wasting time with Kliper then ACTS if MAKS was sitting there just waiting to be finished?
A hydrogen,kerosene, and oxygen rocket will likely produce the performance needed for a near SSTO for a lot less trouble.Burning kerosene during the early phase of the flight reduces the size and mass of the tanks needed.See MAKS http://www.buran.ru/htm/molniya6.htm
And yes, I wouldn't want to be with 100miles of someone dumb enough to be messing with Liquid Lithium and Florine in a rocket.~Jon
Quote from: Jorge on 02/06/2009 02:33 amAnd of course, if you want to go completely crazy, there's liquid ozone 15 and acetylene. But I'll let the co-author of that tongue-in-cheek proposal describe it himself:http://groups.google.com/group/sci.space.tech/msg/3199d5be7e770f44(The rest of the thread is worth reading, for tips on making the acetylene radioactive, etc...)In a similar vein you have chlorine trifluoride, which was at least somewhat seriously considered as a propellant.
Quote from: hop on 02/06/2009 05:54 amQuote from: Jorge on 02/06/2009 02:33 amAnd of course, if you want to go completely crazy, there's liquid ozone 15 and acetylene. But I'll let the co-author of that tongue-in-cheek proposal describe it himself:http://groups.google.com/group/sci.space.tech/msg/3199d5be7e770f44(The rest of the thread is worth reading, for tips on making the acetylene radioactive, etc...)In a similar vein you have chlorine trifluoride, which was at least somewhat seriously considered as a propellant.Thanks Jorge & hop...I had a good laugh from those. I really miss my chemistry 101. And from that last link, I loved this point (among others):"It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water-with which it reacts explosively"
Quote from: robertross on 02/11/2009 12:44 amQuote from: hop on 02/06/2009 05:54 amQuote from: Jorge on 02/06/2009 02:33 amAnd of course, if you want to go completely crazy, there's liquid ozone 15 and acetylene. But I'll let the co-author of that tongue-in-cheek proposal describe it himself:http://groups.google.com/group/sci.space.tech/msg/3199d5be7e770f44(The rest of the thread is worth reading, for tips on making the acetylene radioactive, etc...)In a similar vein you have chlorine trifluoride, which was at least somewhat seriously considered as a propellant.Thanks Jorge & hop...I had a good laugh from those. I really miss my chemistry 101. And from that last link, I loved this point (among others):"It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water-with which it reacts explosively"I still think that George Herbert's gag propellant HOOOCCH was the best. Poly-Acetyl Ozone.http://www.retro.com/hooocch/acezone.html~Jon
I still think that George Herbert's gag propellant HOOOCCH was the best. Poly-Acetyl Ozone.http://www.retro.com/hooocch/acezone.html~Jon
Quote from: space_dreamer on 02/06/2009 11:57 amThe MAKS concept looks ideal - but why would the Russian have been wasting time with Kliper then ACTS if MAKS was sitting there just waiting to be finished?There are other considerations than ISP
Lastly Kliper and ACTS were supposed to be able to go to the moon while MAKS is a pure LEO vehicle.Still I bet they kick themselves for not finishing MAKS since MAKS-M and MAKS-D approach STS in some capabilities and would have given them something to compete with companies like Spacex and Arianespace with on equal grounds.
what about boranes?
Is it possible to get the effect of a tri-propellant with gelled fuels. For example if hydrogen was gelled with methane but the percentage of methane was stratified in the fuel tank so that there was lots of methane early in the burn and less as the burn continued?And if we forget about fixating on maximum isp, is it possible to gell the hydrogen with alternate gelling agents that do not use up so much oxygen as methane. This would allow the fuel/oxidiser mixture ratio to vary less as the hydrogen/gellant mixture ratio changed. In an article I found online, the hydrogen/methane (gelled) : oxygen ratio was 4:1 whereas the pure hydrogen : oxygen it was 6:1. Would there be any advantage in using alternative gelling agents so that this ratio would vary less as the mixture changed during the burn?Perhaps, methanol, ammonia, nitromethane!!Similarly, if there is a substance with a similar energy density/liter as methane but is far denser, then would it make any sense to gell this with methane in a similar stratified fashion? If the engine is running fuel rich then the effective energy densities would be less than that 'written on the can' as there would be incomplete combustion in the form of unreacted h2 and carbon monoxide. Some type of alcohol perhaps?
http://www.wickmanspacecraft.com/loxmono.htmlCheck 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?
It isn't very different from a pebble bed nuclear reactor.
Quote from: mlorrey on 03/09/2009 11:34 pmhttp://www.wickmanspacecraft.com/loxmono.htmlCheck 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.
Quote from: space_dreamer on 02/05/2009 02:28 pmI 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.
Quote from: Jim on 02/05/2009 02:38 pmQuote from: space_dreamer on 02/05/2009 02:28 pmI 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
Quote from: cheesybagel on 02/06/2009 01:53 amIf 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.
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.
Quote from: Patchouli on 02/06/2009 02:12 amQuote from: cheesybagel on 02/06/2009 01:53 amIf 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
Quote from: Jim on 02/05/2009 02:38 pmQuote from: space_dreamer on 02/05/2009 02:28 pmI 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.
That pretty much sums up exactly why no one has built a vehicle to fly it.
I thought gelled props were meant to be more safe than equivalent systems, while giving better Isp than solids. Somehow thought they just never quite get over the line.
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.
The downside of heterogenous engine combinations is that all the engines not in use now add to your dry mass, eating away at the impulse gains of your added low-thrust-high-efficiency engines. If you are adding what is effectively an entire extra stage, it makes more sense to make it separable and discardable (or recoverable) rather than integrating it: you 'lose' the dry mass gains of a single enlarged oxidiser tank rather than two separate ones, but add on the dry mass benefits of discarding an entire additional propellant tanks and engines.TAN designs get to sidestep some of this by using existing mostly existing engine mass (outer bell requires some additional plumbing and possible reinforcement) rather than adding new engine mass, and can gain the sea level thrust and exhaust stability benefits without heterogenous fuels.
Most people think of a tri-propellant as a 2 fuel system but as SABRE demonstrates it can also be an 2 Oxydizer system as well.
Not really. It is only one, Oxygen, just different phases.
Quote from: Jim on 08/23/2022 02:21 pmNot really. It is only one, Oxygen, just different phases.Except one of those phases is also mixed with 80% N2.