Thursday, November 12, 2009

PB2k9: Em-Sem-Fity on M750 - 20,212 feet!

Frank and I conducted the successful M750 drag race just after 10AM on Saturday. Here's a video covering prep and flight:

Here's a liftoff photo verifying Frank Hermes' clear victory in this M750 drag race:
The flights were quick, impressive, and invisible after the smoke charges burned out. I should also note that frank topped 21,000' and, in a separate flight, Mark Clauson attained his level 3 AND topped 22,000' for a club record! Here's his video of the race:
Here's my Parrot2 Altimeter graph and summary:
Here's the way too simplistic summary from the G-Wiz LCX:
I'm likely to sell the LCX and buy the HCX at some point because that's just not enough data to bother! Note the lack of calibration 'cause this is the first time I'd used the device and failed to RTFM. Therefore the acceleration and velocity numbers are wrong. The barometric sensor does not require calibration so the altitude number should be correct. The average of 20,788' and 19,635' is 20,212'. Yay! President's Challenge mission accomplished.
I'd planned to use my GPS transmitter for this flight but realized the fragility of the antenna and the carbon fiber exterior of Em-Sem-Fity was guaranteed to insulate the device from satellites. In the end I used my trusty radio tracker system and walked right up to the rocket roughly 2+ miles north of the launch site. The rocket was entirely intact and dual deploy appeared to have worked perfectly:
While cleaning up the photo sequence of the drag race I noticed something interesting... my flame clearly appears weaker than Frank's. I normalized our two flights using Photoshop and added ruler lines for comparison:
In prepping my motor I heard rumor that I shouldn't use the disposable forward seal disc. I checked with Gary Rosenfield and Karl Baumann from Aerotech (conveniently in attendance at the launch) and Karl was surprised that I had a disposable seal disc. He asked for the lot number but now I only have my nozzle pack serial: 071007. Unfortunately I disposed of the four grain boxes. In any event Karl commented that this M750 reload must have been from an early production batch. As such I must assume that a) my reload was in the neighborhood of 2+ years old and b) there could be an aging effect on this motor that reduced its total impulse and/or average thrust. I'll follow up with Gary and request his input.
Frank challenged me to a rematch at Plaster Blaster 2010. If we do this I'm going to request two sequential serial number reloads built in the same recent lot. For now I'm elated that I exceeded 20,000 feet for a new personal altitude record.


Murdock said...

Congrats on the personal best and a great flight!

Frank Hermes said...

Greg - nice treatment on the spary shot of your rocket...

The lot numbers on my M750 grains:
Aft 07020711
Fwd 07020705

So, all over the board - if those are date codes, plus a 2-digit run number, then it looks like my aft and one forward grain were older and the other two fwd were any event, if the first 6 digits are date codes, they are indeed some old stock - Jack must have bought someone else's surplus, or bought a bunch of the initial that didn't sell - actually, they may be from stock that Andy bought!


Frank Hermes said...

Oops! "sparky" shot...

G Frickin' Muneh said...

That's a great point, Frank. I threw the four propellant grain boxes away so I only have the instruction sheet with nozzle pack serial number. In retrospect that's sure useful. Oh well it's not like I'm trying to get anything from Aerotech. I would simply like Gary's opinion of the difference if he'll offer one. Thanks for a great flight, Frank!