Do motors such as Estes A8-0, B4-0, C6-0 kick backwards or not?

[Funkworks]

If I add this up right, it keeps you just below 125grams total propellant, and assuming you are below 1.5 kg total mass, you are still under the limit for High Power Cert requirement. But don’t put another E engine in there ...

Total weight is around 900 grams and the motor mount is for [1x 24mm ] + [4x 18mm]. That's well epoxied in:


I'm gambling that less recess (compensated for by weight bundle in 3rd stage), reflective aluminum tape, and matching paint, are sufficient to keep heat from the 18mm's away for 2 seconds. At this point, I can't see how to improve this model for launch and just want to see it smoke one way or another!

 

[T-Rex]

Have you considered using a D12-7 as your center motor? That with C6-0's will give you the original performance, while venting the center ejection harmlessly through an open tube. (or will act as a back up if the booster motors fail to separate the nose)

 

[Funkworks]

Have you considered using a D12-7 as your center motor? That with C6-0's will give you the original performance, while venting the center ejection harmlessly through an open tube. (or will act as a back up if the booster motors fail to separate the nose)

I weeded out anything-0 because they will likely eject the chutes at high speed. I wouldn't drill vent holes just so I can use C6-0. Having a coasting delay instead ensures that speed is sufficiently reduced before ejection.

At this point, the following 3 configurations have been confirmed with OpenRockets as having a deployment velocity < 5 m/s, which gives plenty of margin. I believe the actual safe limit is over 15 m/s, but there's no point in going there when I have better options. Chute ejectors are on the right:

- 1[E12-4] + 2[C6-5] + 2[B6-4] (382 ft, first launch)
- 1[E12-4] + 2[C6-7] + 2[C6-5] (499 ft, best altitude yet sim'd, but need to order C6-7)
- 1[D12-5] + 2[C6-5] + 2[B6-4] (278 ft, alternate first launch)

Other likely possibilities include (not yet simulated):

- 1[E12-4] + 2[C6-7] + 2[B6-4]
- 1[D12-5] + 2[C6-7] + 2[B6-4]
- 1[D12-5] + 2[C6-7] + 2[C6-5]
- 1[D12-7] + 2[C6-5] + 2[B6-4]
- 1[D12-7] + 2[C6-7] + 2[B6-4]
- 1[D12-7] + 2[C6-7] + 2[C6-5]

I'll avoid installing more than 2x the same motor, just to avoid the unnecessary risk of having too much charge going off at once.