Estes Little Joe II crash

My Little Joe II suffered total damage when it hit the ground under power after going unstable shortly after lift off. Fortunately Estes’ great customer service sent me a new Little Joe II. Not to self don’t use a BP E motor in this rocket. I have modified the engine mount on the new one. I left out the engine hook and engine block and it will be strictly flown on AP E and F motors.

What BP motor did you use?

You are fortunate they sent you a new kit.
The kit box I have says "Requires composite motor only - E30-4" ………. even with that it says 800 feet.

This is a great build thread with tips for those building the Estes LJ II.

https://www.rocketryforum.com/threa...-joe-ii-tips-tricks-and-modifications.131767/

Like Maxq says, you’re lucky. I’ve only flown mine on the recommended E30-4 composite motor.

I have seen that happen before with black powder motors. I think "reading is fundamental" but I keep it to myself.

MaxQ said:

What BP motor did you use?

You are fortunate they sent you a new kit.
The kit box I have says "Requires composite motor only - E30-4" ………. even with that it says 800 feet.

This is a great build thread with tips for those building the Estes LJ II.

https://www.rocketryforum.com/threa...-joe-ii-tips-tricks-and-modifications.131767/

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I used an E12-4. My Saturn V flies great on them and it is much larger and heavier than the little joe II. I assumed that the Little Joe would do well on an E12.

I usually avoid AP motors because for one they are expensive and two none of my local hobby stores sell them so I would have to pay a hefty hazmat fee just to get one motor. So take that $20 motor and make it $40 or $50. Just for one launch. Forget it. I can understand if it was a high power motor but for a little E motor that’s outrageous.

E30 motors retail for around $35/3 pack and are not hazmat.

burkefj said:

E30 motors retail for around $35/3 pack and are not hazmat.

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Oh. I’ve always seen them in single packs for $20.

https://www.erockets.biz/aerotech-2...1pk-53004vr1-parcel-select-shipping-required/
https://www.csrocketry.com/rocket-m...erotech-e30-4t-blue-thunder-rocket-motor.html
https://www.siriusrocketry.biz/ishop/aerotech-e30-4t-24mm-single-use-motor-3pk-1279.html
All non Hazmat with parcel post.
There are more factors than just weight involved in stable flight. The Saturn V is a longer design, it will come up to a stable speed off the launch rod faster (i.e. lower velocity) than a short, stubby design like the LJ II. It needs a high thrust motor to quickly come up to minimum stable flight off the launch rod. This is where a sim program like Open Rocket or Rocksim is invaluable. It will show you what motors work and don't work in this model. In lieu of that, stick with the manufacturer's recommended motors. E30s may be more expensive than black powder E12s, but less expensive than crashing a pricey model on the first flight. Consider yourself lucky that they sent you a new one for something that wasn't their fault.

Sirius Rocketry charges a $35 hazmat fee. I don’t know about e rockets because it isn’t specified. CS Rocketry looks like my best bet.

rocketman300 said:

Sirius Rocketry charges a $35 hazmat fee. I don’t know about e rockets because it isn’t specified. CS Rocketry looks like my best bet.

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Read the description on the Sirius page again. The Hazmat fee is only if you want to ship via Fedex. No Hazmat if you ship via Parcel post.

Here’s a good source too:
https://www.buyrocketmotors.com/aerotech-e30-blue-thunder-24-mm-single-use-3-pack/

It would be a cold day in hell before I authorized a new kit for you pard.

Motor selection is a skill that gets better with practice, at least for me . I've read that the Little Joe II can be a tricky bugger to balance because of it's shape and mass distribution. I think the thrust curve for the E12 can help explain the flight behavior.

The E12 hits it's peak within the first .4 seconds after which thrust drops to 10 newtons for about 2 seconds. So your rocket went unstable about a half second into the flight because of the combination of motor characteristics and the unique shape and weight distribution of your rocket.

The E30 delivers a little higher thrust but I think the most important difference is that the thrust doesn't drop that much for the duration of the burn. That makes the difference between stable flight and squirrelly flight in some models as you discovered.

It should be noted that if the Estes LJII is built lightly, per the instructions, it flies great on a D12-3.

James

James Duffy said:

It should be noted that if the Estes LJII is built lightly, per the instructions, it flies great on a D12-3.

James

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Thanks. BTW I saw your videos on YouTube about the LJI and LJII. I took you advice one the fin needing to be black on one side on the LJI.