Fuel gauge? Why?

I cannot figure out why the space shuttle would need a fuel gauge. So what is this thing really?

[chico] So we take off, and we getta bouta thirda the way to the moon–out of gas! So we go back, fill up. We take off again. This time we getta bout halfway to the moon–out of gas. Thatsa no good. So we go back and this time we really fill up, and we take off and get almost all the way to the moon . . . out of gas![/chico]

Oh. Oops! :smack:

I was going to ask how you get back from halfway to the moon when you run out of gas then I realized that when it’s in the sky the return trip is downhill.
[shrieking sponge monkey]WE LOVE DA MOON! WE LOVE DA MOON UP IN DA SKY![/SSM]

Very briefly (just because I hate running across threads that end in links)… The fuel gauge in the shuttle is to detect exceptional fuel circumstances, not just normal ones.

Folks mentioned that running the shuttle on “fumes” is bad for the engine. I’ll go ahead and add that if you’re in boost phase and your fuel pressure suddenly goes to zero, there are some decisions that need to be made in kind of a hurry… like abort to Gander, Canada or Shannon, Ireland or abort into a really crappy orbit.

My understanding is that when the tank gets close to empty the pressure in the tank needs to adjusted to maintain proper output.