Launch Day 5

Launch Day: 5
Date: 30/09/08 Afternoon
Location: Berry Oval
Rockets: SRT III, H1

The conditions were overcast but with low winds so it was a nice afternoon for launching. We had two wrockets to launch for the first time.  SRTIII with the nosecone removed had a nice hemispherical top due to the type of bottle expanding at the bottom and we had the new H1 wrocket.

SFTIII enjoyed 4 flights with the highest pressure flight at 90psi, which is the highest for this rocket. It wasn’t using any nosecone so it did bounce quite a bit on landing. The last flight at 90psi took off at an angle from the launchpad and nearly flew out of the park. It landed a good 60m downrange. We decided that would be the last flight for the day for SFTIII.

SFTIII - no nosecone

SFTIII - no nosecone

H1 had 4 flights as well. The first flight we launched at 80psi and used 4 turns of the timer to have the parachute deploy at approx 3.5s – apogee hopefully. Unfortunately the chute didn’t deploy. This was a bit of a disappointment, but H1 flew very straight and quite high. From what we could make out the elastic band caught up on the timer mechanism and stopped the door from opening.

H1 on the launchpad

H1 on the launchpad

Damage Assessment

As a consequence of the first crash the following broke on the rocket

  • The weight on the timer broke off and without it the timer wouldn’t function.
  • The timer broke off the nosecone structure, it was just floating around inside the nosecone. It wasn’t something we could fix at the oval.
  • The table tennis ball in the PPNC also cracked but this was minor.

We decided to fly the rocket without the parachute for the next 3 launches, the nosecone was already damaged so we just straightened it out and flew it again. We increased the pressure to 90psi, then 100psi. Both flights were very straight and very high. It was flying that straight that at apogee it looked like it was backsliding for a while until it pointed nose down and headed for earth. I don’t have a video to confirm this though.

On one occasion we flew with a foam (bubble bath) mixture to see if we could get a good rocket trail, however against the overcast sky it was hard to see.

Here is a video  of the 100psi launch, we used virtuadub to go through it frame by frame to get the flight time, which was 8.867 seconds from launch to crash down. Running this through Cliffords simulator using the wrockets size, water fill, weight etc, we get about 90m (296ft). How high it actually flew I’m not sure but it went very high, much higher than SFTIII.

It was a bit of a heavy landing but the nosecone took most of the damage. The top bottle will probably need to be replaced but this is very easy to do with our modular approach.

We did have a bit of an audience. Two local kids came and joined us and loved it, they stayed until we had finished and had a launch as well. Also one family watched from the edge of the oval and even videotaped the launch :) I gave them some information to find our site so hopefully they might come and join us on a future launch :)

Things we learned

  • The new launcher worked very well, sturdy and the wrockets were nicely vertical on the launcher
  • There were no leaks at 100psi so the one way valve leak looks to be resolved
  • Being able to pull the launch cable from the same location we pump from was good.
  • The PPNC nosecone needs a redesigned as to the placement of the timer as well as using a single rubber band. The size of the door probably needs to be a little smaller as well as the vertical height of the nosecone support structure based on our parachute size.
  • The new corrugated removable fins worked very well. In one of the launches in slow motion, the rocket starts to tilt over but by the time its out of the frame it has straightened up again.

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