OT: What can be so problematic about fuel sensors?

Cryogenics has its own set of anomalous behavior for electronics immersed in extremely cold baths. Then, there's that "gas tight" thing to keep things like explosions from being caused by such sensors or the wires that feed and or exit them.

Maybe they should just put a big sight glass down the side of the tank and view it externally! :-]

On a sunny day (Sun, 09 Dec 2007 11:32:31 -0800) it happened ChairmanOfTheBored wrote in :

Actually that is a cool idea. I was sort of looking forward to watching it launch on NASA TV, always impressive so much power. I was thinking myself: 'air bubbles', not electronics. Such a glass would make a check easy. Else a small video camera next to the sensors with a white LED ?

There ya go. Make a series of holes down the tank side, and put pen cameras in each hole. No more internal sensors.

There is a very interesting video of the redstone rocket days (1960s) where they were very concerned about how efficiently a tank empties while in use. They actually had cameras mounted inside the tanks for a long time during those years. Some of the videos are pretty cool .

cold and vibration ?

They failed on the launch pad. Where was the vibration?

They trip up to the pad at 1 MPH so don't even go there.

ChairmanOfTheBored snipped-for-privacy@crackasmile.org posted to sci.electronics.design:

Cryogenic temperatures. Think about it some more.

Jamie jamie_ka1lpa_not_valid_after_ka1lpa snipped-for-privacy@charter.net posted to sci.electronics.design:

Actually i would go on a different tack. In some aircraft they use a fiber optic "sword" and monitor the end reflectivity with a largish linear sensor. With clean fuels it may never need cleaning and dodges much of the cryogenic temperature induced issues.

On a sunny day (Mon, 10 Dec 2007 05:11:26 -0800) it happened JosephKK wrote in :

Yes, fiber optics, and even using fiber optics with a camera to monitor existing sensors, seems a cool idea that avoids thermal and electrical problems.

It seems to me, that after they replaced everything several times, sensors, wiring, and boxes, one SHOULD look for the obvious *it is somewhere else*. But the days of Von Braun are long past, they fired all Apollo engineers, so perhaps the shuttle was designed by politicians. LOL

One cryogenic level sensor I'm familiary with (I designed the rather straightforward electronics to operate it) depends on superconductivity to function. ;-)

Best regards, Spehro Pefhany

On a sunny day (Mon, 10 Dec 2007 10:20:23 -0500) it happened Spehro Pefhany wrote in :

Interesting idea, goes zero Ohm when it sees cold fluid? Some current and a 4 wire system?

Yup.

Best regards, Spehro Pefhany

Point sensor or the vertical-wire level sensing thing?

John

Hey, here's one:

I designed this for Jefferson Labs in Newport News, a superconductive-cavity electron accelerator.

I didn't realize that this antique was still up on our web site.

John

The latter- Nb wire. N2 point sensors can use ordinary Si diodes, IIRC, but they make assumptions about the vapor temperature.

Best regards, Spehro Pefhany

Well... a series of fibers with polished ends, spaced a couple inches apart, all the way up a rod in the tank center would be a nice idea, but I wonder if the refractivity of the LO2 or LH would be able to be sensed accurately enough to please them.

Nope. Their would have been many more catastrophic mission failures if the boobs we have had in office for the last three decades had anything to do with any of the systems.

Hell, look at the catastrophic national economic mission failure that their tenure in office has caused.

Two inches of glass by two inches wide by however many feet long, expansion mounted with Conap polyurethane epoxy.

YOU think about it some more. Hell, we grow quarts now that is very pure. Wouldn't be that hard to grow a bar of that long enough.

Or even a large, round glass rod where the exposed line of sight is only about 5 degrees or so of the rod circumference, and the rest is in the tank. You could even grind notches in the inner side of it to cause notable refractions between the liquid and rod as it passed over the notches. "Notches... we need stinking notches!" :-]

The "exposed "part would "see" very little "thermal attack" or expansion issues in such a case.

In a big stationary tank setting, this might cause a problem, but in the shuttle, which gets topped off just before launch, and empties at a very fast rate, I doubt it would be an issue at all.

On a sunny day (Mon, 10 Dec 2007 18:39:44 -0800) it happened ChairmanOfTheBored wrote in : It seems to me, that after they replaced everything several times, sensors,

LOL

Na, one of them could have tech as a hobby perhaps. :-)

Jan Panteltje snipped-for-privacy@yahoo.com posted to sci.electronics.design:

Way too many important decisions were made by bean counters instead of engineers. They had to reverse some when Challenger was destroyed, just not all of them.