Here are some hydrocarbons that have been considered
as RG-1 improvements - list and molecules appended. Many have drawbacks, but they belong to rocketry fantasy, help comparisons and show general trends.
has flown, on Soyouz three decades ago, is abandoned allegedly because of cost (synthesis on Wiki), but permitted one cosmonaut more per flight. In the existing tanks and pumps, it replaced RG-1 at identical volume. Notice that four hydrogen atoms less lose 5s over plain cyclopropane, the big cost of a safer liquid.Soctane
seems abandoned, but the easier Boctane
Some mixed "trimer" would improve the flash point. One could also dissolve cyclobutane and cubane if meaningful. Worry: I've suggested here cyclic amines that outperform it
, and some must be easier to synthesize.
we approach the performance of simple cyclic amines - nitrogen brings so much. It just remains to mass-produce... If lucky, the laser pulses or the metal vapour I described there will help:http://www.chemicalforums.com/index.php?topic=77307.msg283262#msg283262http://www.chemicalforums.com/index.php?topic=72951.0
, is made with a carboxylic end by a bacterium, so Wiki's article about ladderanes raised big hopeshttp://en.wikipedia.org/wiki/Ladderane
but the unstrained tail botches the advantage. Consider it only if its cost or liquid range are magic, or if a cheap method isolates the strained part.
The volatile Housane
(Bicyclo[2,1,0]pentane) and its civilized "dimer" are difficult to synthesize, and easier molecules outperform them.Quadricyclane
has a decent synthesis pathhttp://www.orgsyn.org/demo.aspx?prep=cv6p0962
so sizeable amounts were characterized for rocketry:
"Chemical, Physical and Hazards Properties of Quadricyclane"www.dtic.mil/dtic/tr/fulltext/u2/a345589.pdf
but a cyclopropyl-aza variant would be less flammable and keep the performancehttp://www.chemicalforums.com/index.php?topic=79658.0Methane
is often considered the successor of RG-1 because it's cheap and its hydrogen gains 9s. Several adapted engines tested it with success. It leaves the engines cleaner, important if they're reused in the future. Though, it's very flammable and needs bigger tanks and pumps, so no designer has chosen it up to now. I claim that cyclopropane and spiropentane are better
: more efficient, denser, easy to produce. The density would even allow a better chamber pressure not included in the comparison. More importantly, di-spiropentyl (and di-bicyclopentyl) bring methane's performance without the flammability.Bicyclo[1,1,1]pentane
is nicely stable and would have some synthesis paths, often through propellanehttp://www.orgsyn.org/demo.aspx?prep=v75p0098
so it has been considered as a propellanthttp://www.dtic.mil/dtic/tr/fulltext/u2/a267508.pdf
as well as its seducing "dimer", to blend with the "trimer" as needed. With a good process, it's useable.Cyclopropane
is a mass product, with only advantages over methane. Its dimer is volatile, ts trimer is Syntin.Tricyclo[18.104.22.168(2,4)]hexane
is more difficult to synthesize; maybe my laser pulses or metal vapour help.Spiropentane
is made since the 19th century just from pentaerythritol, bromine and zinc or sodiumhttp://de.wikipedia.org/wiki/Spiropentan
(German or Polish as you prefer)
where bromine and the metal could be recycled on the site. Spiropentane is liquid at room temperature, rather dense, nicely stable, and it outperforms methane. Its "dimer", helped by some trimer, is not easily flammable, and equals methane through the gained pressure. Could a pentahalo-neopentane reacted with metal make the dimer directly?
gains 2s more if a designer accepts to cool the engine's walls with oxygen, which isn't trivial. But heavier alkenes are bad, even tetravinylmethane, alkynes too unstable, allenes probably too.cubane
is still a fantasy, stable and so efficient. For solid engines, or dissolved, or tuned to be liquid.
Nitrogen would ease some syntheses: azacubane, ladderanes, housane, diasteranes and more exotic oneshttp://saposjoint.net/Forum/viewtopic.php?f=66&t=2372&start=20
(take with mistrust)
but the toxicity of aziridine versus azetidine suggests that nitrogen shouldn't be too strained, and the harmlessness of new candidates be tested early. Cyclopropanone might helphttp://www.chemicalforums.com/index.php?topic=78226.0
Marc Schaefer, aka Enthalpy