Rocket Flight Computer Readout

barometric sensor head fake from extreme g's. There is a separate 2nd-integral calculated altitude that doe snot show this artifact

G-force spike just over 30'g to peak airspeed

Force in opposite direction blasting nose cone out the front. It is programmed to happen when the computer senses apogee (end of the rocket's climb - best time to deploy a chute)

The upward yank on the airframe of the parachute unfurling and finally filling with air... almost 6 seconds later. It was a brand new chute and I had not aired it out in advance, so it was still tightly packed.

another baro sensor head fake

Negative acceleration: visible effect of air drag in the "free fall".

Rocket Flight Computer Readout by jurvetson.

Here is the overlay graph, straight from the HCX flight computer on my rocket, which records 500 samples/second from various sensors.

• Red is Acceleration / G-forces (peaked over 30 G's)
• Green is Airspeed (from 0 to 315 MPH in 0.76 seconds!)
• Blue is Altitude (3,063 ft. peak)

This was the extended LOC Expediter on the J1520 short-burn motor.

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Comments

jitze says:

What was going on at 19 seconds? Not only did barometric altitude blip positive for a moment, but G forces took a wild swing both pos and neg. Was this the drogue/parachute deployment? If so - it looks like the parachute was connected to the fuselage with the mother of all bungee cords...
Posted 3 weeks ago. ( permalink )

jurvetson says:

Yes! The red spike is the upward yank on the airframe of the parachute unfurling and finally filling with air... almost 6 seconds later. It was a brand new chute and I had not aired it out in advance, so it was still tightly packed.

It can be a bit harsh up there. So I loop the kevlar shock cord and use painter's tape to soften it's unraveling. I also added a tennis ball in line for contact with the rim of the airframe (to prevent zippering if deployed at speed).

I added some mouse-over notes on the graph.
Posted 3 weeks ago. ( permalink )

skeptical thinker says:

Velocity curve looks strange: speed goes to zero
4 seconds before apogee and the curve disappears(!?).

Motor data can be read at thrustcurve and here.

What kind of nozzle was used in this flight?
Could you write the total rocket mass at launch pad?
Posted 3 weeks ago. ( permalink )

menlo says:

Reminds one of that chart Obama's economists put out to sell the stimulus. Unemployment is the rocket shooting well past the predicted bending of the curve.
Posted 3 weeks ago. ( permalink )

skeptical thinker says:

How was the apogee (therefore chute ejection) determined?
Usually it's done from the zero-crossing in velocity, but looking
at the figure, it seems like barometric sensing was used.
By the way, your tidbits in the mouse-over notes are really interesting.
Posted 3 weeks ago. ( permalink )

sbove says:

Would 30Gs kill a mouse-astronaut? Could you rig an ekg on one? ;-)
Posted 3 weeks ago. ( permalink )

skeptical thinker says:

@sbove: Before John Stapp experiments in 1947,
the aerospace conventional wisdom was a man
would suffer fatally around 18G.
Stapp was subjected (voluntarily) to 46.2G !
But the stress is not recommended ;)
Posted 3 weeks ago. ( permalink )

Mentifex says:

The "Notes" feature as used above is really neat. I wish I could learn to install such Notes inside an image of an AI MindGrid, so that Netizens could just wander around on the topology of the AI Mind and see explanations of central features pop up. But as an independent scholar in AI, I am much too busy learning 32/64-bit iForth for transferring my previous AI creations onto 64-bit Linux AI supercomputers As they said in ancient Greece, "he pumate men eos tas pollas ephthasen ascholias," which means, "The last dawn (of your life) comes before many of your desired accomplishments." Sigh.
Posted 3 weeks ago. ( permalink )

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Rocket Flight Computer Readout

Comments

jitze says:

jurvetson says:

skeptical thinker says:

menlo says:

skeptical thinker says:

sbove says:

skeptical thinker says:

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