Archive for July, 2008

 

Launch Day 3

Launch Day: 3
Date: 27/07/08 Afternoon
Location: Berry Oval
Rockets: SRT II

The conditions were a bit windy and rain was forecast but we still managed to get in a few launches and try out a few changes we made.

The launcher had 4 holes drilled in the base and we used 25m metal tent pegs to secure the launcher to the ground. This was to provide better stability at launch and to stop the launcher tilting and the rocket going off at an angle.

We also used some cloth in the nosecone to see if this would provide some better protection on crash down (we havent got a parachute yet)

We got in about 7 launches at pressures from 50psi up to 68 psi. We pushed it up at 2psi increments.

The rain came in and we decide to try at 70psi when the end of the bottle let go again and the rcoket exploded on the launchpad. Again when we are pushign the limits of the bottle we were well back and ensured we were following saftey procedures having the area clear.

No pics of this launch day unfortunately

Things we learned:

  • The new stabillity system for the pad works well. We had quite oly 1 launch that went at an big angle
  • The cloth in the nosecone didnt really give better bounce on landing but did give it more structural stability than an empty nosecone
  • Watch out for ball chasing dogs at the park, they like chasing rockets too !
  • Remember the camera

Posted by on July 27th, 2008 Comments Off

Launch Day 2

Launch Day: 2
Date: 20/07/08 Afternoon
Location: Montview Oval
Rockets: SRT II

The goal of our second launch day was just to have fun and fly the rocket without blowing it up, which we successfully did. We did have a water leak in the nozzle and had to make a quick dash back home to repair it, although it didnt take long.

We were at the oval for about 2 hours and had about 15 successful launches. We also had some of marks soccer team friends come over and have a launch as well.

We decided to only launch at max 50psi as we didnt want to go beyond that and risk an explosion. Also there was no additional weight in the nosecone and it flew fine.

Below are a few pics from the day

SRTII on the pad

SRTII on the pad

Just the spray .. too slow the camera

Just the spray .. too slow on the camera

You can see from this pic that there is a small design flaw with my wooden stake pad stability :) When the release string is pulled too hard the pad tilts and the rocket takes off at an angle. This is something we will fix for the next launch day.

Here is a shot we got of takeoff, you can see the rocket going off at an angle and the spray going up from the launch tube.

SRT II Launch closeup

SRT II Launch closeup

This version of our launcher doesnt have a one way valve inline, so the water gets back in the line when not under pressure, but also the length of the launch tube is about 12m, so at launch you can see the pressure push up a column of water from the launcher.

We probably launched to about 30m, hard to say, the nosecone held up pretty well, the cap was cracked but nothing that cant be fixed.

A great afternoon of water rockets was had.

Things we learned:

  • Our reinforcement of the bottom held fine at 50psi
  • Styrofoam nozzle seals will leak .. better get some rubber ones
  • Need to have better stability of the launcher
  • Got to get quicker on the shutter of the camera :)
  • The cutouts on the fins worked well. Easy to access the nozzle with your fingers when placing the rocket on the pad
  • Take some more tools with us to the launch days

Posted by on July 20th, 2008 Comments Off

SRT II

Name:                       SRT II – (Super RockeT)
Build Date:                16/07/2008
Capacity:                   1.5L
Nozzle Size:               9mm
Fill Volume:               ~ 400ml
Launch Pressure:       70psi
Dry Weight:               ?
Recovery:                  none
Status:                      Blown up

Notes:
Reinforced bottle flew about 20 flights. Blew up at 70psi on the launcher

Pics:

SRT II - reinforcement in the base of the bottle

SRT II - reinforcement in the base of the bottle

Posted by on July 19th, 2008 Comments Off

Bottle Reinforcement

We learned from our first on pad explosion that our 1.5L Lipton Ice Tea bottles need some reinforcement. The bottom of the bottle as you can see in the pic below sinks in quite a bit, approx 10mm and this is the first section to expand when pressurized. As there are many (12 or so) crease lines in the plastic, when it expands it has many weak points, hence this is where it let go

Lipton Ice Tea Bottle (bottom)

Lipton Ice Tea Bottle (bottom)

You can also make out the panels in the side of the bottle, its not round. Not a perfect water rocket body, but its what we have available. We strapped the bottom of the bottle with plenty of duct tape that has material inlayed in it. Also the sides were strapped to provide further reinforcement.

Re-inforcement1

You can see the reinforcement yellow strapping through the nosecone

The tail section from SRT was a bit clumsy to get at the nossle, the solution to this was to just trim out the sections between the fins up higher to that it was easier to access the nossle. This still allowed the fins to be mounted further back for better stability.

The fins were also too long as the rockets weight would sit on the fins and bend them. So I just trimmed them up higher than the three bottom sections of the fin ring

Fin assembly showing the cut outs also shorter fins and section sfor the rocket to rest on

Fin assembly showing the cut outs also shorter fins and section sfor the rocket to rest on

You can see now the fins are above the bottom of the rocket and it can sit on the three sections of the fin ring to support its weight. The fin ring is secured by skewers to the main bottle.

So SRT II was ready to fly on our next outing

SRT II

SRT II

Posted by on July 18th, 2008 3 Comments