Why do you need to know how much fuel is in the tank? Are you going to use less if you’re running out? I doubt it! And you can’t exactly refuel during flight. What am I missing?
If you’re about to run out of fuel, you’ve got to know so that you can shut off the engine. An engine running with no fuel will tear itself apart, likely taking the back half of the orbiter with it.
Sure it’s operative with an engine out! Not enough to get to orbit, but enough to get to a landing site. “Out” meaning “shut down” though, not just running dry. You have to shut them down.
Well, I still maintain this is a good argument for having less sensors. *This* sensor may be necessary (though I read they have four and only need two to work), but in general, adding unnecessary or quasi-necessary sensors is a poor plan.
Gavinsays
Back in the 1970s… when the Shuttle was designed… they figured that redundancy was awesome and the way to go to get a superreliable vehicle. Everyone believed that then, not just NASA.
In the 1980s the US Navy was looking at their failure rate for their redundant-systems nuclear reactors… and found they weren’t as reliable as believed. Turns out if you have 3 of the same thing, and if they were all made or installed at the same time, if one has a flaw they may all have the same flaw.
A common cause failure.
Now that we’re smarter (at least, we like to think so), so if any of our critical sensors are failing before a launch we want to make sure it’s not something that may cause the other sensors to fail during launch. Which might happen if its common cause.
The thing to do is figure out a way to solve the problem without having a sensor. Sensors are non-trivial, and cause much hassle both in design & operation. Even a yes/no indicator is preferable to a sensor. Anyway, I don’t know the details about this case, and y’all obviously do, so presumabley *this* sensor was necessary. But if one was say designing a new vehicle, this is a good example of one of the myriad of problems sensors can cause.
Bad sensor. Boo.
wahhhhhhhhh! this sucks!
A good argument against unnecessary sensors. (Not that this one was necessarily unnecessary.)
Well, the sensor is fairly necessary. Measures how much fuel is in the tank, therefore preventing blowing up the engines…
Why do you need to know how much fuel is in the tank? Are you going to use less if you’re running out? I doubt it! And you can’t exactly refuel during flight. What am I missing?
If you’re about to run out of fuel, you’ve got to know so that you can shut off the engine. An engine running with no fuel will tear itself apart, likely taking the back half of the orbiter with it.
So the shuttle is operative with an engine out?
Sure it’s operative with an engine out! Not enough to get to orbit, but enough to get to a landing site. “Out” meaning “shut down” though, not just running dry. You have to shut them down.
Well, I still maintain this is a good argument for having less sensors. *This* sensor may be necessary (though I read they have four and only need two to work), but in general, adding unnecessary or quasi-necessary sensors is a poor plan.
Back in the 1970s… when the Shuttle was designed… they figured that redundancy was awesome and the way to go to get a superreliable vehicle. Everyone believed that then, not just NASA.
In the 1980s the US Navy was looking at their failure rate for their redundant-systems nuclear reactors… and found they weren’t as reliable as believed. Turns out if you have 3 of the same thing, and if they were all made or installed at the same time, if one has a flaw they may all have the same flaw.
A common cause failure.
Now that we’re smarter (at least, we like to think so), so if any of our critical sensors are failing before a launch we want to make sure it’s not something that may cause the other sensors to fail during launch. Which might happen if its common cause.
The thing to do is figure out a way to solve the problem without having a sensor. Sensors are non-trivial, and cause much hassle both in design & operation. Even a yes/no indicator is preferable to a sensor. Anyway, I don’t know the details about this case, and y’all obviously do, so presumabley *this* sensor was necessary. But if one was say designing a new vehicle, this is a good example of one of the myriad of problems sensors can cause.