[Johan Kristensen]

Hi!
After reading a Bloomberg article (read more here) about "Firefly" company, which is working on a new engine for small rockets. So the questions are - which fuel is used in modern engines and is it possible to make them eco-friendly?

Sorry if I posted this into a wrong topic. If moderator can- would you be so kind to put it into the correct thread.

Thank you

[chenbeier]

Liquid hydrogen and oxygen, mainly.

Instead oh hydrogen also other liquids, like methane, airfuel, alcohol etc. Instead of oxygen, nitric acid, chlorinetrifluorid,etc.

https://en.m.wikipedia.org/wiki/Liquid-propellant_rocket

[billnotgatez]

@OP
you might want to use the search feature on this forum
I used
rocket fuel
and got many links of discussions on this forum

[Johan Kristensen]

Liquid hydrogen and oxygen, mainly.

Instead oh hydrogen also other liquids, like methane, airfuel, alcohol etc. Instead of oxygen, nitric acid, chlorinetrifluorid,etc.

https://en.m.wikipedia.org/wiki/Liquid-propellant_rocket

Thank you)

[Johan Kristensen]

@OP
you might want to use the search feature on this forum
I used
rocket fuel
and got many links of discussions on this forum

But still you have replied to my comment =)
Thank you anyway

[Enthalpy]

The extreme variety of the 1950s has boiled down to very few propellant combinations.

Solids still serve. Only ammonium perchlorate + aluminium + polybutadiene is in use. Research is being done on other oxidisers. Improvements come from processing mixes with a bigger proportion of perchlorate, and from graphite fibre casings.

Storable liquids are phased out as much as possible because they're dangerous. Satellites use electric propulsion increasingly so they don't need hydrazines any more. Some old launchers still use nitrogen tetroxide with hydrazines (hydrazines, MMH, UDMH and their mixes). Solid launchers need some additional engines for roll control and precise orbit injection, the usual choice is then storable liquids, alas.

Some research is done on less dangerous storable liquids, but satellites don't want them any more and new launchers not really. Maybe the additional engines for solid launchers?

For performance, liquid oxygen is the standard choice. It's combined with hydrogen, so-called kerosene (a special fuel for rockets that resembles more Diesel oil, very purified), and now methane.

All other oxidisers are completely abandoned for being too dangerous or impractical. From time to time, someone pops up with hydrogen peroxide because he ignores the risks or wants to store it for months in orbit.

Other fuels, either amines or hydrocarbons, could combine with liquid oxygen. All bring performance very similar to "kerosene" and methane, a miracle is impossible there. But they can be more easily available, or safer, or stay liquid at colder temperature, or be slightly more efficient than kerosene but liquid under standard conditions, and so on. I've put much time in that (most thoughts and results are on Chemicalforums) and believe to have considered nearly all reasonable possibilities.
http://www.chemicalforums.com/index.php?topic=79637.0
http://www.chemicalforums.com/index.php?topic=79637.msg337420#msg337420 visual comparison
http://www.chemicalforums.com/index.php?topic=86972.0
http://www.chemicalforums.com/index.php?topic=91735.0
http://www.chemicalforums.com/index.php?topic=56069.0
and some more.