NASA Wants Green Rocket Fuel

It's not really about being "Green". Hydrazine is very toxic and extremely unstable. It's terribly dangerous to work with even when things are going right, and when a launch goes wrong you may end up dropping a hydrazine-filled satellite in an urban area. That's not good, so you have to considerably overengineer the tanks (adding weight, reducing payload) so they'll survive reentry and not poison people.

So why do we use this devil of a propellant?

Normal rocket juice is two parts - fuel (eg H2, kerosene) and oxidizer (eg O2, N20). You flow both into your combustion chamber, strike a spark, and away you go. That's great for long sessions of high-power lift. The problem is it's terrible for fine maneuvering. Maintaining the proper mixture gets harder with small flows, your spark plugs wear out with repeated firings, and generally the whole bipropellant setup is big, heavy, and complicated, and you want your satellite to be compact, light, and as simple as possible for reliability.

So that's where hydrazine comes in. It's the same property that makes it dangerously unstable that makes it an ideal fuel when you need very low impulse and very high reliability. You just open a small valve on the line from the pressurized tank tank to the engine - that's your only moving part. The hydrazine flows into the combustion chamber where there's a catalyst. It instantly and very exothermically decomposes into ammonia, nitrogen and hydrogen gas. The very high temperature rise makes the exhaust velocity really high, which is great for efficiency.

Et voila, you have a rocket engine where the only moving part is the flow control valve. Since you want to do complex maneuvers, you can sprinkle a bunch of these little, simple, lightweight engines all over your craft instead of having a couple big complex (fuel mixing) ones with vectoring (gimbals and actuators are just more things to fail, plus now you need flexible fuel lines), and you can do your maneuvers in tiny bursts that are too short to even get a bipropellant engine to light off.

Similarly, the very low parts count makes hydrazine turbine engines very useful where maximum reliability is required - for instance APUs for hydraulic power used for the space shuttle, and on military aircraft for emergency backups.

Finding a safe replacement would allow much safer handling, lighter safety systems, and allow monopropellant engines to be used in places that they're impractical now.

Source: http://rss.slashdot.org/~r/Slashdot/slashdotScience/~3/UONGrqB_08U/nasa-wants-green-rocket-fuel

lil kim martial law mike wallace mike wallace is jon bon jovi dead jon bon jovi jon bon jovi