China launches 'pollution-free' rocket China used its latest green rocket design to carry 20 micro-satellites into space on Sunday. Xinhua news agency reports the Long March–6 was successfully launched from the Taiyuan Satellite Launch Centre in north China’s Shanxi Province. While it won’t earn a Greenpeace sticker, the Long March–6 is about as environmentally …
If that's a current long march the luminous flame means hydrocarbons not being burned efficiently if they were the flame would be blue with shock diamonds. . LOX & RP-1 have been propellants since the early days of rocketry and was used on the Saturn 5. Kerosine or JP fuels tend to sludge up rocket engines. When the fireball is burning nicely this'll burn to CO/CO2/H20 probably with some remaining unburned hydrocarbons as it'll run slightly rich to keep the temperatures down. And some NOX.
Best propellant combo are liquid hydrogen and LOX but the thought of all that seriously cryogenic LH2 sloshing about puts the rocketeers off.
A Big Bang as that's what you get if these things spontaneously self-disassemble.
Liquid rocket engines tend to be run fuel rich for a number of reasons. Performance is one of them - you get better efficiency by not burning cleanly, since the efficiency is inversely proportional to the molecular weight of the exhaust products. Lots of CO and H2 in the exhaust of a hydrocarbon burning rocket by design.
you get better efficiency by not burning cleanly,
Bowing down before the rocket scientists, could I humbly ask why efficiency improves? I follow the logic about keeping combustion temps down, but surely the less efficient the burn, the more fuel & structure weight you're having to lift. Is it really more efficient to lift fuel and then hose a proportion of it out the back end unburnt?
There are two measures with a rocket engine.
Firstly there is thrust.
Then there is fuel consumption.
With conventional rocket engines one is inversely proportional to the other. Thrust means you cannot achieve fuel consumption efficiency as the exhaust velocity is relatively low.
You want a lot of thrust when you launch from Earth as you have to push your entire rocket up against gravity, and quickly enough that it doesn't topple over when you lift off the pad; consequently you want to shove as much propellant mass out of the nozzle as possible, even if you don't clean burn the entirety of your propellant. Rocket nozzles are optimized for certain flight regimes and the first stage is usually burning most efficiently not that far from the pad.
This is where the kerosene/RP1 comes in for big lifting because it is vastly denser than that other major rocket fuel, hydrogen.
Fuel consumption kicks in when you are at altitude and moving fast. You use your second and subsequent stages to burn much lighter propellant, such as liquid hydrogen.
The critical value here is exhaust velocity. The hydrogen, being as light a molecule as you can get, is kicked out at a much higher velocity and so is much more efficient as a fuel - the efficiency is measured as the log of the exhaust velocity.
The downside is the thrust is small compared to the Kerosene/RP1 propellant and your LHyd/LOx rocket may not even have enough thrust to get off the ground, so is useless as as first stage.
One way round the thrust/efficiency conundrum is to go nuclear. You can shove the hydrogen fuel out the reactor nozzle at ludicrous velocities, hundreds of times more efficiently as a chemical rocket and get big thrust as well.
The problem is that as soon as you mention nuclear some people start frothing at the brain and automatically hitting the downvote button.
Ah! I remember some more about this from reading Sutton & Biblarz!
The efficiency of a rocket engine is known as the Specific Impulse or Isp. It's related to how much exhaust can be ejected, and how fast. If a rocket generates lots of smaller molecules in its exhaust (CO is smaller than CO2, H2 is smaller than H2O), then any heat energy can be better used to make those smaller molecules move faster. The equation for kinetic energy is 0.5*m*v^2, so for the same amount of energy and a lower mass of molecule, you get a much larger velocity. More exhaust velocity == more Isp = VROOOM!
Of course you have to burn some fuel and oxidiser to get the heat in the first place, so you can't get even more thrust by just ejecting cold H2 gas (thought it is surprisingly effective).
I think the "clean" bit is because it's not using carcinogenic hydrazine-based fuels N2H4 / UDMH and N2O4. A lot of China's rocket tech is soviet based, and the Russians rockets often used these, at least in the past, because they were storable (not-cryogenic) and so better for use in ICBMs :(
Oops. That should read "You can shove the hydrogen propellant out the reactor nozzle at ludicrous velocities, hundreds of times more efficiently as a chemical rocket and get big thrust as well."
With a nuclear engine the fuel is whatever material you are burning in the reactor (uranium/plutonium etc.)
Clark's excellent "Ignition" goes into all this in detail, a quick google will get you a PDF. A must read, a basic grasp of maths and chemistry is handy but not vital. There are quite a few amusing moments too.
Plenty epic fail on YouNyancat. Rocketry fails provides the best Guy Fawkes fireworks!
Explosion - due to a tank of HTP and one rat.
You always want to light the rich burn mixture first and then slowly trim O2 to the right ratio or the damn thing goes "POP" like the torch, only a lot louder and with far more dire consequences.
As said elsewhere, the right final flame color is blue with shock lines in it. We don't typically see that here on Earth launches because we often use solid fuel boosters to get the bird off the ground. Since they burn ammonium perchlorate and latex rubber with carbon black in them, they smoke like a volcano and obscure the LOx/H2 flames.
China has already landed a rover on the Moon,
What, the Roadkill Rabbit, or whatever, that promptly keeled over? I understand the pain and loss of the Chinese proletariat - I've had Chinese made stuff that only lasted that long.
Although I suppose they're still doing better than Beagle 2.
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