My fourth and final flight at Plaster City's June '11 launch was my new 4" fiberglass Extreme DarkStar. I've sort of resisted the 75mm motor class for a decade but now I'm into it. I ran some calculations and the cost in $/N•s is identical between 75mm and 98mm reloads (~$0.06-0.10/N•s). This means the overall cost is lower with identical impulse per $. Big fan.
The wind was kicking up big time but I was confident that dual deploy combined with shear pins would bring the rocket down reasonably close. Unfortunately my keychain video camera died on the K740 flight below so I have no onboard or ground-based video. The pix are still good though. KO snapped this prep shot and I like it! (ignore my photo credit as that's an artifact of batch export):
Here's the pressure up:
And liftoff... note the excessive wind blowing the plume:
The ascent was arrow-straight but I lost site after apogee ejection because I was using CO2 deployment and a tiny drogue 'chute. This was also my first time using the Beeline GPS unit because the fiberglass structure doesn't attenuate the signal. Unfortunately I forgot to tape the unit down to the foam mount so I think it dropped to the bottom of the electronics bay on liftoff as my GPS altitude data was wonky. I did receive what appeared to be directional information, however, so I started walking NW. Then I heard a loud pop as the 4g main black powder charge blew at roughly 1200' as expected. I watched the rest of the descent and it landed only ~1/4 mile NW of the launch site (closer than most flights in low wind!). Luckily the dragging parachute caught on a bush so no damage was done by subsequent dragging. Stupid mass convection. Here's the Raven Altimeter data with a barometric peak altitude of 7,489':
And here's the ARTS2 altimeter data with a barometric peak altitude of 7,233' for an average of 7,361' (1.39 miles) at sub-Mach velocity:
I also ran the ARTS2 motor analysis and the report says it's an L680 (vs. the nominal L585).
Finally the ARTS2 coefficient of drag was roughly 0.5 at peak velocity.
I next plan to fly this rocket on the same propellant type but twice the motor size (M1230) so I expect roughly twice the altitude or ~14,000'. Fingers crossed for October 8th!