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?