Tuesday, October 14, 2008

Poor Mans Metrology

Many months ago we hydro tested our Sphere (370lbs) , Yesterday we tested our Backup vehicle sphere (385lbs) ,today I tested our new catalyst tank (475lbs) . These pressure tests set the upper limit (with some safety factor ) of what pressure we can operate the tanks at. In a traditional aerospace company everything involved would be “calibrated” and traceable to NIST. We can’t afford that so we do the next best thing we calibrate the pressure transducers used on the vehicle against the beat up old pressure gage on our hydro tester.

So I pumped up the transducers while hooked up to the vehicle electronics and compared what the telemetry said against what the gage said. I’m happy to report that they match exactly.  

The new Cat tank is installed, the repositioned catalyst injectors on the motor are done and the valves and vehicle all check out. My son is on the way back with a Swageloc fitting we needed to hook up the last new line to the new cat tank.  We are still on track to leave tonight and we will try a short translational flight under tether and then a long 90 second hover under tether at daybreak Wednesday morning.


Timothy J. Massey said...

Go Breeds Go!

We're pulling for you.

James Bauer said...

Good luck!

Rocket Dude said...

I've found that my Omega pressure transducers agree exactly with a $9 welders gauge from the hardware store... until you drop the gauge that is.

John Carmack said...

Did you hydrotest the catalyst tank that leaked? I would be interested in hearing if it failed at a lower pressure after exposure to the catalyst.

Stevo Harrington said...

To prevent a leaky catalyst tank, it might make sense to passivate the stainless tank. This process reduces the chance that the permanganate can attack the stainless at the weld where spots of pure iron or other metals can form and then rust.

Paul Breed said...

We patched all the pinholes then hydro tested the cat tank that leaked. it went to 75% of the theretical value for that thickness of stainless.
I did not go higher because I have a lower pressure gauge on my hydro tester for better resolution.
In doing this we created more pinholes (that we patched) and we continued the process until we had not pinholes and it still did not fail. Its pretty clear that the catalyst was atting specific impurities in the welds.