Slightly off topic - fuel flow and hose diameters

[boscoe99]

Some of you like your "pressure" and "less pressure" "not vacuum" theory.
How do you pump fuel in space, i.e. in the absence of air pressure? Is it possible?
Think about what happens with the simple child's bubble making machines. What makes the bubble?

I am a "no vacuum" guy. Vacuum is just a misnomer for less pressure.

In space, in the absence of air pressure, some other type of pressure is used to pump fuel. Could be a mechanical pump, could be an electrical pump or could be a cylinder of high pressure gas.

[zenoahphobic]

I am a "no vacuum" guy. Vacuum is just a misnomer for less pressure.

In space, in the absence of air pressure, some other type of pressure is used to pump fuel. Could be a mechanical pump, could be an electrical pump or could be a cylinder of high pressure gas.

Vacuum is not necessarily a misnomer for less pressure. It is a word (just a word in the English language) that can also be used to describe the phenomenon I alluded to previously; bonding between atoms and molecules.

Consider a boat portable tank full of fuel attached the usual way by hose and pump bulb to an outboard in outer space (no atmosphere, no gravity).
What happens when I compress the bulb with the vent shut? The same as on earth the bulb cannot move fuel forward.
What happens if I did the same, now with the tank vent open? You would agree that, unlike on earth, I still cannot move any fuel. You would say because there is no atmosphere, the less pressure in the bulb has not been met with greater pressure on the fuel in the tank to push it out.

However if I removed the tank, the fuel will remain as a bubble and connect (place) the fuel line into the fuel and squeezed the bulb the fuel will pump!! Most, if not all pumps will work this way!!

Why? because the bonding forces within the fuel makes it happen. The fuel sticks to the bulb walls etc. and moves with it and gets pushed past a valve and stays there. There is no resistance or pushing of this fuel from external forces. It merely gets pulled and pushed by the bulb.

So if this is true, why could I not pump with the fuel in the tank with the vent open? Simply because the tank had a larger area in contact with the fuel pulling it back. Now if we made a tank that has less sticking ability than the pump surface the fuel can be pumped, even with the vent closed (unlike on earth).

The "vacuum" here is the force trying to pull apart the bond between molecules.