Shit into rocket fuel?

[Blind groper]

http://www.sciencedaily.com/releases/20 ... ce+News%29

A new meanng for the term "the Right Stuff!"

[klr]

Good article.

It makes good sense to me. Being able to produce significant amounts of potable water is a bonus, especially if you're on the Moon, or Mars. You need to recycle as much as possible within a closed system.

[JimC]

I get a bit like that after curried beans...

[mistermack]

I would think that one of the first jobs of a station on the Moon would be to mine water ice, and crack the water to produce a huge store of liquid hydrogen and liquid oxygen for use in the return vehicles.
Once you have a secure store on the Moon, you could be confident enough to not bother sending oxygen from Earth for the return trip.

I doubt if methane would be that much of an advantage, as you would need to produce enough oxygen to burn it, and when you do that, you automatically produce the right amount of hydrogen for it to burn anyway. So if you used the methane, you would just end up with surplus hydrogen.

You don't need a lot of energy to take off from the Moon, because of the low gravity.

If you compare the size of the rocket needed to get to the Moon, with the one for the return trip, there's no comparison. I think I read somewhere that an ordinary rifle can shoot a bullet from the Moons surface into a Moon orbit.

[Xamonas Chegwé]

The escape velocity at the Earth's surface is about 25,000mph (ie. that's how fast you would need to fire a bullet for it to escape the Earth's gravity altogether. On the surface of the Moon, the escape velocity is only about 5,400mph. A regular, high-velocity firearm shoots bullets at about 2,000-3,000mph but there are weapons which do exceed the Moon's EV.

NB. It is not necessary to reach the EV to escape a planet's gravity. That is the speed at which the projectile's momentum would overcome gravity without further propulsion. In practice, far lower speeds are used, as further propulsion is provided. Also, the further one travels from a body's surface, the lower the EV becomes.



In other news, NASA does not recommend that you shit into rocket fuel - it clogs the rocket jets, apparently.

[pErvinalia]

You can be damn sure Seth has a gun that fires faster than that!

[Xamonas Chegwé]

You can be damn sure Seth has a gun that fires faster than that!

Pesky moon tries to come on my land, I'll give it a dozen new craters!

[mistermack]

It might be that a rifle that shoots a bullet at 3,000 mph on Earth could shoot it at over 5,000 mph on the Moon, with no air in the barrel. It would be sure to be a bit faster, but how much faster you would need to measure it to find out.

They could build a takeoff ramp on the Moon, and accelerate the return craft with a linear electric motor on takeoff, to further reduce the required fuel.

[pErvinalia]

You wouldn't be able to fire a rifle on the moon without air. The explody thing which makes the bullet shoot out of the barrel would need air to fire.

[mistermack]

You wouldn't be able to fire a rifle on the moon without air. The explody thing which makes the bullet shoot out of the barrel would need air to fire.

I don't think so. The oxygen is contained chemically in the charge. I don't think there's any need for air.

What they could do is build a special big cannon, that fires containers of fuel into orbit, and the orbiting mother ship could collect them up and store them, for use with a return vehicle.

[Xamonas Chegwé]

It might be that a rifle that shoots a bullet at 3,000 mph on Earth could shoot it at over 5,000 mph on the Moon, with no air in the barrel. It would be sure to be a bit faster, but how much faster you would need to measure it to find out.

I doubt that air in the barrel would slow the bullet all that much. Certainly not by that margin. Air resistance comes into play much more after the bullet leaves the barrel. Remember that the air in the barrel is rapidly expanding (and hence heading in the same direction as the bullet) due to the heat of the propellant burning.

BTW, the de facto EV from the Earth's surface would be higher than I quoted in order to overcome air resistance - that figure comes from a formula that only allows for deceleration due to gravity

They could build a takeoff ramp on the Moon, and accelerate the return craft with a linear electric motor on takeoff, to further reduce the required fuel.

A railgun, you mean?

[Xamonas Chegwé]

You wouldn't be able to fire a rifle on the moon without air. The explody thing which makes the bullet shoot out of the barrel would need air to fire.

I don't think so. The oxygen is contained chemically in the charge. I don't think there's any need for air.

Guns fire perfectly well under water.

[mistermack]

A railgun, you mean?

Something like that. There are all sorts of possibilities on the Moon that wouldn't work on Earth, because of the air and high gravity.

They could run some rails up the side of a mountain, and launch it from that.
It would only be an assist, but it cuts down the amount of rocket fuel needed. You could use the energy from a giant flywheel, to accelerate it up the mountain, with the rockets taking over when it lifts off at the top.

Not in my lifetime though.

[Blind groper]

Railguns and hydrogen fuel from cracking water are really possibilities for the future. The first colony on the moon will need to think small. Anything that required a lot of material or sizeable plant will not be possible. Later maybe...

[mistermack]

Railguns and hydrogen fuel from cracking water are really possibilities for the future. The first colony on the moon will need to think small. Anything that required a lot of material or sizeable plant will not be possible. Later maybe...

Given the cost of moving stuff from Earth to the Moon, the top priority should be to begin a new field of science, of building up a manufacturing capability using raw materials found on the Moon.
There is unlimited potential of electrical power, from solar panels, so producing water from ice, and cracking it into hydrogen and oxygen would be fairly easy.
Producing metals might be feasible, but it would need to be done with miniaturised equipment till enough machining stuff could be made locally.
You would think that glass could be made fairly easily, if the raw materials were there, and it's surprising what you can make with glass. You would be using whatever you could, just to get going.
Even if it didn't compare in quality to Earth components, that wouldn't matter too much, it would be far more economical if you could make it up there.

It would be like the industrial revolution, all over again, with each new possibility building on what went before.