HCX Flight Computer Readings

• Green is airspeed in MPH
• Blue is Altitude (via barometric sensor)
• Red is acceleration / G-shock
X-axis: Seconds from launch

I wish the central I200W motor had lit (from the white pyro triangle) sending the Brighthawk skyward, ready for two chaser rockets to be captured by my videocam.

The oscillation on the return path is from the flat roll the rocket went into when the parachute failed to deploy. Both failures result from electric matches that failed to fully ignite. I am still debugging that, but I am suspecting two bad igniters as both see to have fired, but failed to ignite the pyrogen and black powder respectively.

At least it was not a ballistic lawn dart. I wonder if the strap-on camera helps induce the flat roll, as I have seen this spin before with this camera, but not on any of my other parachute deployment failures…

9 responses to “HCX Flight Computer Readings”

jurvetson

Apr 8, 2009 at 5:41 am

post-mortem… or post-success… and even when the computer is destroyed and sits in a field for a year, there are forensic recovery techniques (now underway for my supersonic lawn dart…

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Rocketman8911

Apr 8, 2009 at 6:00 am

That’s very odd to not have either electric match not to light. What brand of electric match were you using?

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jitze

Apr 8, 2009 at 7:41 am

I think your theory about the roll on return being caused by the strap-on camera is likely correct. Asymmetric drag induces yaw which kicks out the tail which induces counteractive force against the asymmetry which results in an oscillating wobble slightly off axis which gives a net vector with some torque. Wobble with axial torque = wobbly spin… (complete layman’s explanation)

Maybe next time strap a dummy camera on the other side to make it symmetric. Frankly I’m surprised the imbalance in drag didn’t throw it off kilter much earlier in the flight (what do I know…)

But I’m interested in your definition of "ballistic" – you say it didn’t return ballistic – I assume because it had some spin. But I thought "ballistic" meant no external power but purely under force of momentum and gravity? Or do you mean the spin caused some slow-down thus mitigating final impact and minimizing breakage?

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Vox Sciurorum

Apr 8, 2009 at 11:32 am

How accurate and quick to respond is the barometric sensor under flight conditions?

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jurvetson

Apr 8, 2009 at 11:42 am

I’ll have to check the default settings, but somewhere between 62 and 500 samples per second (per G-Wiz site).

jitze – I just mean ballistic as in nose down, picking up speed with minimal wind resistance.

Stanley – Wildman, yellow wire, about 2 years old.

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Todd Huffman

Apr 8, 2009 at 5:36 pm

I would have thought the sudden stop at the end would have been bigger than that first step… but apparently not from the acceleration…

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pegleg000

Apr 9, 2009 at 7:32 am

Is that a one-axis accelerometer? Velocity calculated by integrating the accelerometer output? Slick little unit.

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benjiman

Apr 9, 2009 at 8:19 pm

ballistic in the "GET THE F OUT OF THE WAY" sense methinks.

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HCX Flight Computer Readings

9 responses to “HCX Flight Computer Readings”

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