# Fuel gauge? Why? **URL:** \ **Category:** Factual Questions\ **Created:** [July 14, 2005, 9:37pm UTC](https://boards.straightdope.com/t/fuel-gauge-why/312580 "2005-07-14T21:37:55Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Hilarity\_N.Suze](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hilarity_n.suze/32/6223_2.png) [@Hilarity\_N.Suze](https://boards.straightdope.com/u/Hilarity_N.Suze)\ **Post date:** [July 14, 2005, 9:37pm UTC](https://boards.straightdope.com/t/fuel-gauge-why/312580/1 "2005-07-14T21:37:55Z")
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] ---
**Author:** ![Hilarity\_N.Suze](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hilarity_n.suze/32/6223_2.png) [@Hilarity\_N.Suze](https://boards.straightdope.com/u/Hilarity_N.Suze)\ **Post date:** [July 14, 2005, 9:44pm UTC](https://boards.straightdope.com/t/fuel-gauge-why/312580/2 "2005-07-14T21:44:48Z")
Oh. [Oops!](http://boards.straightdope.com/sdmb/showthread.php?t=325524) :smack: ---
**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\ **Post date:** [July 14, 2005, 9:58pm UTC](https://boards.straightdope.com/t/fuel-gauge-why/312580/3 "2005-07-14T21:58:10Z")
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] ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [July 14, 2005, 10:23pm UTC](https://boards.straightdope.com/t/fuel-gauge-why/312580/4 "2005-07-14T22:23:48Z")
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. ---
**Author:** ![Skipper\_Too](https://avatars.discourse-cdn.com/v4/letter/s/6de8d8/32.png) [@Skipper\_Too](https://boards.straightdope.com/u/Skipper_Too)\ **Post date:** [July 14, 2005, 11:00pm UTC](https://boards.straightdope.com/t/fuel-gauge-why/312580/5 "2005-07-14T23:00:39Z")
My understanding is that when the tank gets close to empty the pressure in the tank needs to adjusted to maintain proper output. From [MSNBC](http://www.msnbc.msn.com/id/8569277/page/2/) > [@](#): > > Why the sensors are important > The low-level sensors are supposed to signal the fuel system to get ready for shutting down the shuttle’s main engines if propellant levels get too low. For that reason, they’re also known as engine-cutoff sensors or ECO sensors. > > If the sensor system fails, the shuttle’s propulsion system might not be able to adjust the fuel system correctly during its ascent to orbit. A false “dry” reading could lead the system to shut down the engines too soon, leaving the shuttle too low to reach orbit. A false “wet” reading could keep the engines running at a high rate when they should be in shutdown mode. Tests in the early days of the shuttle program indicated that such a condition could result in “serious, uncontained damage” to the propulsion system, Hale said. > > “It’s a good thing to shut your engines down in a controlled manner before they actually run dry,” Hale said.