Why did my main deploy at apogee?

[s201]

That is a nifty webpage for your data.

Thanks! I wrote a short Ruby program that reads the log file from the SD card on my flight computer and automatically generates an HTML file like that for quick analysis at the launch site.

Are you using an acelloromter to calculate altitude? Also is the sample rate on the graph 1/10 sec?

A barometer is used for altitude, but I'm using a 3-axis accelerometer in conjunction with the barometer for apogee detection. The sample rate is roughly 4 per second.

Perhaps the lids were reversed, or the wiring to them - the charges fired but the main came out at apogee.

Yup, always a possibility. I have a wiring diagram that I use when prepping the rocket and do a continuity check so I really hope I didn't make that mistake though.

---

There was a short break in the rainy weather we've been having this afternoon for me to get a quick ground test in. Everything went well except the main charge was slightly more energetic than I would have liked so I'll dial back the BP for that. But otherwise, it worked as intended so I think I'm going to fly it without the motor ejection charge and hope for the best.

 

[SpaceManMat]

Curious that your altitude increases after drouge deployment for up to a couple of seconds.

Can you please provide raw data for say 2 seconds before and 2 seconds after?

 

[s201]

Sure! https://pastebin.com/JzhbXLkQ

Each line is one data point. When the "phase" field changes from 2 to 3 is the point at the which the drogue charge is fired (also the "apogee_fired" field is set to 1 at this time too).

 

[SpaceManMat]

And the correct answer is...

Still going up quite fast approx. 20m/s hard to tell because each sample is not time stamped
Scale is everything so I suggest for future flights you log the exact time.

It looks like there was a single dodgy reading (sample 9) that fooled your altimeter into thinking it was descending.

 

[Nick@JET]

For what it's worth, I drill alignment and orientation indentions so I won't reverse. I also color code the main and apogee charges and female plugs on one and make on the other so it is not possible to wire backwards. Try to idiot proof as much as possible - especially if you wind up in a hurry at a launch.

I've even keyed my AV bay for extra insurance - overkill I know

 

[NateLowrie]

View attachment 303909
For what it's worth, I drill alignment and orientation indentions so I won't reverse. I also color code the main and apogee charges and female plugs on one and make on the other so it is not possible to wire backwards. Try to idiot proof as much as possible - especially if you wind up in a hurry at a launch.

I've even keyed my AV bay for extra insurance - overkill I know

View attachment 303910

Not overkill. It's poke yoke, or mistake proofing. You are mitigating risk due to human error. Very nicely done. With the Key you probably don't need the dedent marks but it doesn't hurt to have both.

 

[Onebadhawk]

Not overkill. It's poke yoke, or mistake proofing. You are mitigating risk due to human error. Very nicely done. With the Key you probably don't need the dedent marks but it doesn't hurt to have both.

Very cool Nate,,
I do the same but with a different method..
All drill holes won't line up if something is in wrong...
Nick,,
That "V" notch is a seriously cool idea...
You know what that means,,,
It's getting burglarized,,, lol...

Teddy

 

[Nick@JET]

Not overkill. It's poke yoke, or mistake proofing. You are mitigating risk due to human error. Very nicely done. With the Key you probably don't need the dedent marks but it doesn't hurt to have both.

Yes those indentions are redundant . I've always done that on all components of a DD rocket - so I already had the indents but decided to add the notch after reading Pokerjones putting his AV bay in backwards after a switch failed in his launch day and under stress things happen. Poker is pretty smart guy so I know this could happen easily when your trying to think of everything - then something goes wrong.

On my L2, I drilled half the switch home in the switch band and half in the booster for a one way installation - however should've done that on the rivet or fixed side so no edges for the harnesses to catch on.

Also not that I really think of selling a rocket, but if I sell or loan a rocket , I'd like to make it easy for someone else.

Teddy, steal away. Looking forward to seeing you at MWP

 

[OverTheTop]

I use a metal dowel pin, or a short piece of carbon fibre rod (from hobby shop) as the key, glued in place. Works very well. It really simplifies assembling the stack.

Here is my 8.25" Nike Smoke