Archive for July, 2008

 

Launch Day 1

Launch Day: 1
Date: 13/07/08 Afternoon
Location: Rofe Park
Rockets: SRT

Our first launch was with the whole family, one rocket, one launcher and much excitement. Rofe Park is pretty big and even though there were a few peopel around they were well out of the way. We setup our launcher to the funny looks of a few people and filled the rocket.

launch Day 1

launch Day 1

We filled about 1/3 full put it on  the launcher and pumped up to 40psi, that was about as far as we wanted to go to start with, not knowing how much this type of bottle would take.

5 4 3 2 1 .. launch .. Mark pulled the release and up up the rocket went …  to the cheer of all there .. big smiles all around. We were pretty happy and feeling good …

We decided to take it easy and went up by 10psi to 50psi … filled it 1/3 full with water on the launcher .. everyone back then pumped it up to 50pis .. 45 .. 50 .. BANG !!! The nosecone which was tapped on was 3/4 blown off but still hanging on .. the bolts were on the ground (see bad idea … lucky everyone was well back .. safety first) …

We inspected the damage … the end of the bottle had blown out. see pic below

Ruptured at 50psi

Ruptured at 50psi

This wasnt something we could fix in the field so we packed up the rocket, had a bit of a play at the park with the soccer ball (good backup) then went home

Things we learned:

  • We need some re-enforcement on the end of the bottle
  • Always do the safety checks before filling
  • Dont put bolts in for nosecone weight

Posted by on July 13th, 2008 Comments Off

SRT

Name:                       SRT – (Super RockeT)
Build Date:                10/07/2008
Capacity:                   1.5L
Nozzle Size:               9mm
Fill Volume:               ~ 400ml
Launch Pressure:       40psi
Dry Weight:               ?
Recovery:                  none
Status:                      Blown up

Notes:
One good launch at 40psi. Blew up at 50 on the pad

Pics:

First Water Rocket SRT

First Water Rocket SRT

Posted by on July 12th, 2008 Comments Off

First Water Rocket

During the term 2 holidays my son and I were looking for something fun to build and as I am a space enthusiast and my son loves anything to do with space so we decided on building a water rocket.

We did a bit of research on the Internet and decided built one with the bottles we had lying around. These happened to be 1.5L Lipton Lemon Ice Tea bottles. While these are probably not ideal its a good place to start.

The Rocket

Our first rocket is named SRT, I think its an acronym for (S)uper (R)ocke(T)

First Water Rocket SRT
First Water Rocket SRT

It was built out of two bottles

  • one bottle for the pressure vessel
  • another one cut up – the top section used as the nosecone and the midsection used as a mount for the fins.

We used 3L milk carton (dairy farmers etc) to cut out the fins and some broken skewers taped to the fin attachment to provide additional fin stability.

For the nozzle we used a standard plastic gardena 9mm nozzle and some styrafoam for a washer between the bottle and the cap. For this first rocket we actually glued the nozzle in place as there was a bit of leakage around the hole in the bottle cap due to the not so even hole in the cap.

We used duct tape that has the material/threads running through it to tape everything on and taped the pressure bottle to give it a bit more strength.

We were not sure how much weight needed to be in the nosecone to bring forward the centre of Gravity (CG) so we put a few bolts into the nosecone and screwed it shut (ok this wasnt on reflection a good idea !)

The rocket took us about a day .. not bad, my fun had fun flying it around the lounge room that evening .. no air/water in it, just holding it running around the place and throwing it to make sure it would fly.

The Launcher

First Attempt at Launcher
First Attempt at Launcher

Well the rocket was pretty easy but the launcher took a bit more research and work to get right, its not the grandest of launchers but it works and has room for improvement. Its basically 3 pieces of wood I had lying around bolted together and a square piece of metal cannibalized from an old frame that used to keep the sun off the sandpit (its headed for the landfill as we speak) but I kept the metal.

The attachment is a metal gardena female adapter and we had a foot pump available as the air source. I also had some 13mm black plastic pipe from the old garden water system (sydneysiders will know these systems were outlawed from being connected to the mains water …. however I digress) we purchased a 10m air hose from the hardware store and a couple of 10mm connectors .. then the fun started.

The hose from the foot pump has an internal diameter of 6mm, the 10m blue air hose is closer to 8, the black hose from the gardena is about 12mm. I foolishly thought I could heat up the hose and get it to slide over the 9mm though connectors I had .. ahh no .. didn’t matter how many times I heated it up, it just wouldn’t do it, then if I did get one side attached the other different size one wouldn’t fit. I needed some though connectors that converted from one size to the other.  I had real trouble finding adapters to connect them altogether, but I ended up at a rural water supply/fittings shop who had most of the size adapters I needed. I used metal clamps (the screw type) to clamp the hoses to the adapters to get an airtight seal.

metal clamps
metal clamps

Once the air hose was connected and tested it was cable tied to the metal upright(which was in turn bolted to the base. I think I was lucky  that the metal upright I was using had a molded piece that was used to connect other uprights , once these were removed it provided a easy spot to push a bolt though for the release string to move through to change the direction from vertical to horizontal(see pic)

The string is just 10m of 4mm nylon type string from Kmart I think :) .. about $2-3. This was clamped around the movable section of the female gardena connector so that when the string is pulled it pulls down the gardena connector and releases the rocket.

Last but not least I used a wooden stake to bang into the ground to steady the launcher.

We did a few pressure tests before heading to the park to give our rocket  launch

Posted by on July 12th, 2008 1 Comment