Hi All,

I am working with Steve Eves who last year launched a 36' tall scale Saturn V rocket and in so doing, set a record for the largest model rocket ever launched and safely recovered. Having accomplished that he has now set out to build a 1/10 scale Saturn 1b with two stages.  What he needs, and what I am researching is a method to determine whether the second stage is at or near a vertical attitude before the second stage engines are ignited. I have been palying with a Parallax Javelin board and a Sparkfun two axis rate gyro, but as you have probably already guessed, a rate gyro in this application is useless.  So, I am currently looking at the 9dof Razor IMU and would welcome input on the best way to go about accomplishing my task. We basically need a go or no go signal if the vehical is off of local vertical by more than 10 degrees or so. Any input would be appreciated. Remember that at first stage burn out, the vehical will be experiencing zero G flight. Thanks!!

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Kraig,
see these for more info:

Comment1

Comment2

Rocket post
Yes, NAR and TRA rules state no live animals.
Yes, you'd certainly want to test for that before depending on them, but I think the exhaust plume would be out of the thermopiles' field-of-view.
We had considered this and indeed will have a backup controller for aborting the second stage ignition. We would rather have an automated system to trigger the ignition.
Big time no :-)
How is this project going?
Well we have the 9dof Sparkfun IMU running the SF9DOF_AHRS_1_1 program with a slight modification to send a signal to a Arduino board when X Y tilt exceeds 10 degrees. The arduino is programmed to wait for a staging signal, delay 3 seconds to allow for seperation, then look for a second stage fin deploy signal and the vertical angle signal from the IMU before firing the second stage engine. It works fine at 1 g and usually works with the limited amount of testing we have done shaking, throwing, and otherwise trying to upset the IMU. We intend to send the package up in a single stage rocket with the telemetry downlinked via xbee so we can determine how it works in actual practice. I AM LEARNING A LOT! If nothing else the project has opened up a new world for me using the Arduino boards and learning the programming etc.
Good to hear. I look forward to seeing moreprogress and the launch.
What is the thrust to weight ratio of the 1/10th scale? Stage diameters? Sounds like a very cool project.

My Tripoli Level III cert flight was considerably smaller. Only 10ft tall 7.5 inches diameter and 52lbs at lift off. The motor producted 450lbs of thrust for 1.5 seconds and reach 4800'. Had an on
board camera and video transmitter and didn't notice any appreciable vibration in the video.

Ken
Hi Ken,

The diameter is roughly 29" for both stages with the CSM being slightly smaller (don't have exact sizes here at work. Thrust to weight has yet to be exactly determined because the all up weight is still in flux. T to W should be in the 8 to 1 area. Not to concerned about vibration but very concerned about g loads.

Test, test, test before you risk it all. The vibrations are your biggest problem. Send up whatever your avionics on a small rocket with higher g’s and a higher dynamic than the big scale model will achieve.

Check out 2 our weekends ago: http://www.garvspace.com/2011/P-18A_FT-1/P-18A_FT-1.htm

Kevin Baxter

President Friends of Amateur Rocketry, Inc.

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