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Feb 04, 2011, 11:45 AM
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rockbus's Avatar
Adrian Where on your chart is the 468mph lap?
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Feb 04, 2011, 12:04 PM
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sll914's Avatar
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I don't think the 468 lap is on the logger. Perhaps we can correlate each lap to it's speed when Chris gets the video done and see... But, I'm sure some of what is on the logger is in the 400+ range. It seems like we were into the 380s by the 3rd lap!

Spencer
Feb 04, 2011, 12:08 PM
Rocket geek
Quote:
Originally Posted by OZPAF
Thanks Spencer and Adrian for posting and analysing the onboard data. It would be interesting to see what the G loadings were at 468mph.
Its also amazing that the electronics can with stand these loadings as well.
The old software with discrete components may have had trouble surviving. Just another advantage of surface mounted stuff.
John
Keeping the board small really helps, too. Last April I flew a Raven in a supersonic rocket of mine that came apart prematurely at 700 mph due to inadequate venting of the airframe. The chute ripped off, and so it all came down from 10,000 feet at about 160 ft/second, IIRC. The avionics bay buried itself in the ground 5", but the Raven stayed running the whole time. Based on the depth of the ground penetration and the initial speed, it survived an average of 900 Gs. The only damage was that the big capacitor on the board moved sideways and sheared off the buzzer. If I had glued the cap down, it probably wouldn't have even been damaged. I also have a version with a single-axis accelerometer that has a range of 250 Gs for flights with very fast-burn motors in light rockets. I've pushed it over 125 Gs, and a guy with a crazy scratch-built motor used it successfully on a 220 G flight.

Quote:
Originally Posted by sll914
Thanks for your analysis Adrian and for the pointers in using the FIP software. I guess it didn't really sink in just how precise this logger is and how high the sample rate is... Really is an impressive tool.
Thanks, Spencer, and congrats again on an amazing flight. I've been telling my friends at work about it, and nobody can believe it. I have a hard time picturing working up the nerve to pick up a plane with over 8' wingspan on a ridge blowing at 60+ mph, let alone chuck it and fly it at 468 mph. Awesome performance.

Quote:
Originally Posted by sll914
If you could incorporate airpspeed option up to 600mph-700mph in the airplane version, that would be a great feature to have.

Looking forward to another flight with a larger data set. I also wanted to try a vertical punchout at a known speed to take a stab at measuring the drag and confirming fuselage/interference drag estimates...
That should be do-able. I've used the Raven to measure the coefficient of drag of my rockets as a function of velocity. I've been looking into differential pressure sensors for pitot tubes.
Quote:
Originally Posted by wr_mizzard
Very cool data... very cool flight.

-James
Quote:
Originally Posted by spotterone
that is awesome! I love a good data set, and it's even better when someone analyses it! Amazing to think of the loads on our planes when DSing. Impressive.
Thanks, guys.

Quote:
Originally Posted by rockbus
Adrian Where on your chart is the 468mph lap?
Unfortunately, it's not on there, because it stopped recording prematurely. The Raven has a feature for rocketry that cuts off the data recording after landing, based on looking for constant barometric data. I think the laps at the same altitude spoofed the landing detection algorithm. Ironically, Spencer's record-breaking flight may have been the first time a Raven has taken data in a plane, since I haven't had the chance to do it with mine yet. I think I'll give Spencer's Raven a custom firmware load to disable that feature if he wants to try again.
Feb 04, 2011, 12:11 PM
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daboz's Avatar
Quote:
Originally Posted by sll914
I don't think the 468 lap is on the logger. Perhaps we can correlate each lap to it's speed when Chris gets the video done and see... But, I'm sure some of what is on the logger is in the 400+ range. It seems like we were into the 380s by the 3rd lap!

Spencer
Just finishing up the video now,,,

Chris


Feb 04, 2011, 12:14 PM
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sll914's Avatar
Thread OP
Quote:
Originally Posted by Adrian A
I think I'll give Spencer's Raven a custom firmware load to disable that feature if he wants to try again.
You Bet, I'll try it again!!!

Thanks Adrian! Exciting stuff...

Spencer
Feb 04, 2011, 12:21 PM
Registered User
did you manage to make a graph of airspeed over the plane(pitot) VS ground speed (GPS)
Feb 04, 2011, 12:31 PM
Rocket geek
Quote:
Originally Posted by JustinONE
did you manage to make a graph of airspeed over the plane(pitot) VS ground speed (GPS)
I'm working on a version that logs GPS and airspeed, but it will be awhile before one is ready for production.
Feb 04, 2011, 01:04 PM
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rockbus's Avatar
Thanks Adrian and congratuations Spencer on the new WR. Can't wait to see the video.

This data is very interesting. Is there enough accellerometer data to determine airspeed at all points of a lap. I recall you need a 3 axis accellerometer and you have to integrate over some dt to get the area under the curve and then some how throw in a probability density function.... but that was 30 years ago when I had more brain cells.
Feb 04, 2011, 01:11 PM
Rocket geek
Quote:
Originally Posted by rockbus
Thanks Adrian and congratuations Spencer on the new WR. Can't wait to see the video.

This data is very interesting. Is there enough accellerometer data to determine airspeed at all points of a lap. I recall you need a 3 axis accellerometer and you have to integrate over some dt to get the area under the curve and then some how throw in a probability density function.... but that was 30 years ago when I had more brain cells.
I think you would need a full-up 6-axis IMU, with 3 gyros. There has been a lot of progress on MEMs parts to do that just in the last few years, driven by the Wii and other games. It's still a big problem to deal with the gyro drift on those parts. The Wii uses an IR sensor stuck on top of the TV, and gravity, to keep the gyro estimates from drifting away.
Feb 04, 2011, 06:14 PM
Registered User
It would be really cool to get accurate info on airspeed and drag. I would definitely be interested in a data logger that could do that.
John
Feb 04, 2011, 09:44 PM
Pledged to Always Chase Wind
deputybuzz's Avatar
Thanks very much to Spencer and Adrian for sharing all this information. Very interesting stuff! Can't wait to see more.

Congrats on your amazing accomplishments. Keep on making history.

-Spencer Deputy-
Feb 05, 2011, 11:42 PM
Registered User
garyg4rc's Avatar
All I can say is WOW!!! Thanks again, Spencer for bringing the record back to my own back yard!!!

Gary


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