Aluminum Rocket!

[Coyote]

Discussed at MSNBC

Aluminum fuel could power future space trips
Environmentally-friendly fuel sent rocket screaming 1300 feet into the air

Steven Son / Purdue University
This test rocket soared 1300 feet into the air using seven inches of a new, environmentally friendly fuel made of nanoaluminum and ice.

updated 9:56 a.m. MT, Tues., Nov . 3, 2009
Aluminum and water is usually a boring combination, but light a mixture of nanoaluminum and ice and the results are explosive.

Scientists from Purdue University have created a new, environmentally friendly solid rocket fuel that recently sent a rocket screaming 1300 feet into the air using seven inches of nanoaluminum and ice. The new fuel could power missions to the moon or Mars while dramatically reducing the amount of on-board fuel.

"Theoretically you can get very high temperatures using aluminum and water, but the kinetics would be so slow and it would be so hard to ignite that it's very hard to actually make the rocket work," said Steven Son, a professor at Purdue University in Indiana who helped develop the new fuel.

Aluminum ice, or ALICE for short, can be compressed into a solid bar for safe and easy shipping. Nanoaluminum smaller than 80 nanometers can be created, but it doesn't allow enough oxidation to occur on the surface of each particle, which means not as much thrust. Eighty nanometers, say scientists, appears to provide the maximum amount of thrust.

During a recent field test, the Purdue team launched a nine-foot tall rocket more than 1300 feet into the air using a hollow rod of ALICE seven inches long and three inches across. In less than a second the rocket had accelerated to approximately 200 miles per hour.

Since ice exists on both Mars and the Moon, ALICE could be manufactured on site. Creating rocket fuel at either location means spacecraft wouldn't have to carry all the fuel for the return trip to Earth; they could simple create it when they arrived.

ALICE is also environmentally friendly. The existing solid rocket booster on the space shuttle produces about 230 tons of hydrochloric acid for every flight. ALICE fuel produces aluminum oxide, found in ceramics and precious stones like rubies, and hydrogen gas.

Excellent, but I wonder of the thrust-to-weight rations stay consistently impressive as the mass of the rocket increases?

[McC]

I was about to post a rant about how media outlets just don't get the scope of space travel, but at the very bottom (:eyeroll:), they do actually mention

Still, 1300 feet into the atmosphere is a far cry from the 238,857 miles to the moon.

That aside, I think this research is pretty cool stuff and hope they keep making headway with it.

[Coyote]

Oh, yeah, right now it's just a new version of a model rocket, which was whay I was wondering about the thrust keeping up with demand as it got bigger, etc.

Actually, I wonder if this would be a choice option for thrusters on a larger ship using, say, a nuclear-ion main engine...

[Starglider]

There's a good video covering these engines on YouTube. The theoretical max ISP is about 250 seconds, comparable to the SRBs on the space shuttle. Thus it's a viable choice for strap-on boosters and suborbital joyrides (presumably trading the need to chill the motor casing for a less toxic exhaust), but not as a primary propellant.

[PeZook]

And, of course, it's solid fuel, with all the problems it entails. That is: it's completely useless for thrusters and maneuver engines, which need to be restartable. The upshot is, of course, that it's very simple to make with a supply of alluminium and ice, which gives some interesting possibilities for lunar development et al.

[Coyote]

And, of course, it's solid fuel, with all the problems it entails. That is: it's completely useless for thrusters and maneuver engines, which need to be restartable. The upshot is, of course, that it's very simple to make with a supply of alluminium and ice, which gives some interesting possibilities for lunar development et al.

That's why I was wondering if it could be used in a thruster. Think of it as a binary munition; a tank of ALICE and a tank of ordinary water. A thruster burn ratio will already be pre-timed, so you just mix a couple teaspoons of each, as needed, and pack it in the thruster (obviously done mechanically, I don't mean mix with literal teaspoons! ). You don't have to insulate the feed pipe to the thrust outlet because the whole point is to freeze the water with the ALICE inside, and in null-gee the mixture should/could be evenly distrubuted (?).

Thruster fuel of ALICE and water could be in one storage area, and only pre-mixed and distributed as needed. You wouldn't need insulation (weight/mass) for the last part, and stored seperately they'd be safer than a liquid fuel mixture.

Or is it just too damn complex for little real gain?

[The Spartan]

That sounds too complex. Why would you want to try to store two different substances in two different containers, mix them in a third container hoping that they mix properly, freeze them and then ignite them for course changes, most of which don't require much more than a brief *poof* of propellant to be expelled?

[PeZook]

Thruster fuel of ALICE and water could be in one storage area, and only pre-mixed and distributed as needed. You wouldn't need insulation (weight/mass) for the last part, and stored seperately they'd be safer than a liquid fuel mixture.

Or is it just too damn complex for little real gain?

Dude, way too complex. The main selling point of ALICE is that you could make it on-site with low-tech, with only half of the necessary ingredients (the alluminium) being shipped to you, with ice found around your moonbase/mars colony.

If you have to carry both the ice and the alluminium onboard, it defeats that saving. Installing a complex mixing system only makes the thruster less reliable and slower to react, which can kill you. Compare this to the simple elegance of hypergolic fuels: two tanks, two feed pipes with simple valves. The propellant is delivered into the combustion chamber by pressure alone, and ignites when mixed. Combustion products are expelled by the pressure, producing thrust. Voila. That's all.

This simplicity was why the ascent stage of the apollo lunar module was powered by a hypergolic engine: it had no moving parts save for valves, so the odds of it failing to fire were miniscule (save for ridiculous things like a faulty switch: see Apollo 11)

Thruster are in many ways similar to the ascent engine, except their reliability is even more important, because they need to be used all the time, fired after long periods of inactivity, fired rapidly in bursts, fired at full bore or only marginal thrust, etc.

Even firing a main maneuvering engine on spacecraft like the S-IVB required ullage motors, which could doom the entire mission if they failed.

[Coyote]

Yeah, I thought after I posted that the mass & weight saved by the insulation would be negligable, and more than eaten up by the specialized pre-mixing machinery that would be needed.

Well, um... hmmm... how about, in an emergency, the stored water could be used to drink while the crashed astronauts build a new spaceship out of the ruins of the old one, and name it "Phoenix"!

Naw, you're right. It's easier to go with the current system. Damn, thought I was onto something there for a moment.

[Azazal]

pretty damn cool, hopefully this works as a viable new fuel source, and it's not like the ingredients are in short supply.

side note problem I see, and it has nothing to do with the actual use, but how long till the 9/11 troothers that love to go on about nano-thermite hear about this and latch onto it in some twisted fashion?

[Sky Captain]

So the chemical reaction is alike when dropping an ordinary alkali metal in water only aluminum is grind into very fine dust to increase reactivity. Right?

250 s specific impulse is pretty lousy, it could only be useful as a strap on boosters to H2 burning core stage or as a main engine to launch something from the Moon where escape velocity is lower and ingredients to make this fuel are present.