Two stage HPR rocket fail example?

Looking for a video which I've seen before but can't find it again... I think it's been deleted.

Rocket launch with two stage large HPR motors - takes off, the first stage is underpowered and second stage ignites while it's falling and it powers into the crowd. Nobody was hurt as far as I know.

Need a good example for my club to explain why two stage is dangerous and second stage should only ignite when rocket is vertical. Can anyone help? PM me if you don't want to share video widely.

Found one example

[video=youtube_share;1VAkWgbCtA4]https://youtu.be/1VAkWgbCtA4[/video]

Any others?

Wow, is that too over stable or not enough lift that started that craziness?

Nick@JET said:

Wow, is that too over stable or not enough lift that started that craziness?

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Not enough thrust. Poor planning, or just a bad burn, in the end it's irrelevant.

Any Two stage HPR should have lock-outs that prevent it from igniting the second stage if the booster fails to preform optimally. Electronics to do this are common and widely available. Just slapping a timer on and hoping for the best.... leads to the above issue.

I'm still trying to understand why you need a video (???!!!) to explain why it's best to have the sustainer in a vertical position at ignition.

Sorry, but it sees like that's a given.

Nick@JET said:

Wow, is that too over stable or not enough lift that started that craziness?

Click to expand...

Looks completely unstable to me. CP way in front of CG. I guess the launcher didn't do his sims.

I was there. Rocket had flown before fine.
This time booster was underpowered.

Simply not enough thrust off the pad. Not enough velocity to be stable. Increase the booster thrust fifty percent and maybe a longer rail and this is likely not an issue.

While dangerous and glad that no one was hurt, that was cool!


TA

cherokeej said:

I'm still trying to understand why you need a video (???!!!) to explain why it's best to have the sustainer in a vertical position at ignition.

Sorry, but it sees like that's a given.

Click to expand...

Ok. I'll bite. Because it's illustrates the case for having a safety lockout in your electronics, rather than just a simple ignition timer.

If the electronics support second stage safety lockout and prevent airstart ignition if the rocket is going a) too slow and b) 3 axis accelerometer shows it is going up then that would have prevented this 'incident' from happening.

amell said:

If the electronics support second stage safety lockout and prevent airstart ignition if the rocket is going a) too slow and b) 3 axis accelerometer shows it is going up then that would have prevented this 'incident' from happening.

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What electronics available today does this?

jeff2space said:

What electronics available today does this?

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Eggtimer

Does the Eggtimer have the ablity to fire the ejection charge if the rocket has an electronic deploy for the parachute?

K'Tesh said:

Does the Eggtimer have the ablity to fire the ejection charge if the rocket has an electronic deploy for the parachute?

Click to expand...

Yup.

TA