Sunday, February 11, 2007

Saturdays Testing(updated II)

From the lunar lander project perspective everything on Saturday went perfectly. The systems all worked as designed, we had no frozen vales, instrumentation or computer problems all of that was flawless.

The real story is we were testing an older engine design that used a pyrotechnic igniter and we and that failed to get it lit. So some time in the next 24 hours I'll post a very boring video of Lox and alcohol coming out of a motor in unburned form.

If we had more Lox we would have tested again, but we were using the left over Lox that had been delivered for a different project. By the time they were done there was less left than expected. My son was very disappointed we did a lot of work and got no flames, booms or other intersting pyrotechnics. I was happy with the result because the components of the test that apply to the XPC project all worked flawlessly.

Here is the test video, kind of boring, I've also uploaded an unrelated video of other rocket things...

6 Comments:

Blogger John Carmack said...

I know that you already know this, but "lox and alcohol coming out of a motor in unburned form" meant that you were a hair's bredth from having a big explosion and wrecking a lot of stuff.

It is tempting to try and get something going without ignition detection and automated shutdowns, but it isn't a good idea...

John Carmack

4:36 PM  
Blogger Paul Breed said...

Agreed completely.
We were under cover in the block house. While out at the site the Garvey group ran a 5000 lb motor.
The ran it twice, first time it was perfect for 5 seconds or so.
(What a glorious sound)

2nd Time they hard started it and it went boom in a most spectacular fashion they found shattered bits of the injector plate more than 300 yards away.

7:37 PM  
Blogger Carl Tedesco said...

Sounds like a good reson to get your torch igniter developed.

The pyro-ignition can be made to work, but redundant igniters is a good idea. Ken Mason uses pyro igniters with a K-type thermocouple to verify ignition. It's buried in the pyro-grain so you sense a temperature rise about a second or two after ignition. Also, pyro ignitions are notoriously "dirty"... lot's of fuel-rich soot and contaminants can go back into injector holes. A purge is a good idea.

Well, at least you've got your processes and test protocol down.

--- Carl

6:40 AM  
Blogger Carl Tedesco said...

Paul, maybe Paul Jr. can make some candy igniters so you can test detecting ignition using a thermocouple. We have some signal conditioners at Flo that can turn a K-type t/c into a 0-10VDC signal.

9:16 AM  
Anonymous James Jarvis said...

Otherwise you can use the quick and dirty MAX6675. K thermocouple to digital converter with SPI interface. $10 single quantity. Omega has printed circuit board mount thermocouple connectors.

2:35 PM  
Blogger Jon Goff said...

Paul,
I have to echo John's advice. We only figured it out after the fact, but that time we punted the chamber was due to a delayed ignition. I was doing some detonation analysis back when we were up in Santa Clara, trying to get permission to test at a potentially closer site than our old test site. LOX/alcohol if thoroughly mixed can be 2x as powerful as TNT by unit weight. And it's shock sensitive.

Be careful.

~Jon

3:23 PM  

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