L1 in my future

Download RockSim file from Madcow web site and open it in RockSim or OpenRocket. Override stage mass to whatever your rocket's actual weight is. Load H123 and do flight simulation.

NAR safety code requires the rocket to achieve off-rod velocity that ensures a stable flight - that's 30 to 45 fps. In this respect, what matters is initial thrust of the motor and not the average. H123 produces 150Ns thrust at the beginning, and you'll be able to see in flight simulation whether this delivers enough "kick" to the rocket.

Good luck with L1

-Alex

Thanks Alex, I've already done that, and modified the file for the actual mass and distribution of my rocket (all that epoxy adds up).

The simulations are all green, I was just concerned that 11 m/s (around 36 ft/s) was a bit slow.

You are right of course on the initial thrust being important for initial velocity. I type ahead of myself sometimes..

Thanks,
- Matt

Bill - could you tell the length of HPR launch rods and rails we have?

I suspect there's more clearance than default 40" value in OR...


-Alex

I ran a few more simulations. The top launch button on the Super DX-3 is ~25" from aft, and I assumed the rocket was 5" up on the pad. That left 42" of effective rod length from the original 72" rod. Ran another one at 40" just to be safe.

Results:
42": 15 m/s when clearing the rod (49 fps).
40": 11.3 m/s (37 fps).

Good numbers.

Thanks for the tips and discussion.

- Matt