New Rocketeer in the Ashdown Forest

[Bibbleycheese]

Hello everyone. I've just found this forum after a bit of web searching.
I'm working on my 4th bottle rocket now.
I'm using regular 2L PET bottles with a Gardena release mechanism, which operates on a quick-release when a string is pulled.
I've been fooling around with a plain bottle with a bored cork launcher, which popped out at 20psi. After being inspired by the episode of Mythbusters on water rockets, I started searching the web for advice - and WOW!
I tested my first serious rocket in the front garden at just 30psi with a teeny bit of water inside. It whooshed over two rows of houses before landing in a neighbour's pond. They were really great about it, as they've seen me with all the neighbourhood kids out the front playing with the low pressure pop rocket. But that first test proved the system was going to work.
Now I found myself a good isolated launch site out on the Ashdown Forest.
I reckon I got up to about 100metres when I launched the other day.
Here's a video...
[youtube][/youtube]

[rockets-in-brighton]

Welcome to the forum. You're only 25 miles away!

That's an excellent result from a 2L bottle (maybe 60-70m though), interesting design... What's the nosecone made from, and how do you secure all the parts together?

Hello everyone. I've just found this forum after a bit of web searching.
I'm working on my 4th bottle rocket now.
I'm using regular 2L PET bottles with a Gardena release mechanism, which operates on a quick-release when a string is pulled.
I've been fooling around with a plain bottle with a bored cork launcher, which popped out at 20psi. After being inspired by the episode of Mythbusters on water rockets, I started searching the web for advice - and WOW!
I tested my first serious rocket in the front garden at just 30psi with a teeny bit of water inside. It whooshed over two rows of houses before landing in a neighbour's pond. They were really great about it, as they've seen me with all the neighbourhood kids out the front playing with the low pressure pop rocket. But that first test proved the system was going to work.
Now I found myself a good isolated launch site out on the Ashdown Forest.
I reckon I got up to about 100metres when I launched the other day.
Here's a video...
[youtube][/youtube]

[Bibbleycheese]

Here's my LS04 rocket on the launcher in the Ashdown Forest.

rocket 037b.jpg (137.8 KiB) Viewed 97 times

The nose is made from a yellow foam "rocket ball" which I picked up from Morrisons for a pound. This had a tube tail section, which pulled out easily. This left a hole through the centre of the ball which was just big enough to fit over the neck of the bottle on the upper chamber.

The ball makes the nose heavy, so the rocket does a nose-dive to the ground at terminal velocity every time. I tried the rocket without the nose a couple of times, but it didn't fly so straight on ascent, or go nearly so high. I need to experiment to see if this is because of the nice aerodynamic shape of the ball, or whatever.

All this lawn-dart landing has rather crumpled up the payload section, but I've just got myself a parachute to try out. I've got to work out how to release it, but I found some plans for a remote control release, so it's off to Maplin for components next.

Any good tips on working out altitude without a flight recorder? I do want to build some sort of recorder, but I've got to get the parachute system sorted first.

[rockets-in-brighton]

Here's my LS04 rocket on the launcher in the Ashdown Forest.
The ball makes the nose heavy, so the rocket does a nose-dive to the ground at terminal velocity every time. I tried the rocket without the nose a couple of times, but it didn't fly so straight on ascent, or go nearly so high. I need to experiment to see if this is because of the nice aerodynamic shape of the ball, or whatever.

You can calculate how much nose-weight you need to make your rocket stable, it depends mostly on your fin size and location. I use simplified Barrowman equations. Nice fins BTW - they look like foamboard. I like the way they conform to the bottle shape, that also helps to keep them nicely far back. Did you use a template to shape them, or trial and error?

All this lawn-dart landing has rather crumpled up the payload section, but I've just got myself a parachute to try out. I've got to work out how to release it, but I found some plans for a remote control release, so it's off to Maplin for components next.

Does remote release mean radio control? If you get good altitudes you'll need a proper R/C airplane rig to get the range.

Any good tips on working out altitude without a flight recorder? I do want to build some sort of recorder, but I've got to get the parachute system sorted first.

Try one of the simulators to get altitude estimates. Just remember that the sim will assume everything is optimal (rocket stable, nozzle straight, etc.)

[rockets-in-brighton]

You can calculate how much nose-weight you need to make your rocket stable, it depends mostly on your fin size and location. I use simplified Barrowman equations.

Here's my calculator, might be useful.

http://groups.google.co.uk/group/rocket ... calculator

No refunds.

[Tim Chen]

Hi Bibbleycheese! I wanted to say that your launcher diagram is really NICE! Did you make that diagram from your launcher???

[Bibbleycheese]

Nice fins BTW - they look like foamboard. I like the way they conform to the bottle shape, that also helps to keep them nicely far back. Did you use a template to shape them, or trial and error?

Thanks for the compliment
The fins are made from corriflute. I scrounged a sheet from a discarded sign. I tried using foam board, but it just went soggy.

I used a profile gauge to map the contours of the bottle I was using. I had to do this in 2 sections as the bottle was larger than my gauge. Then I transferred the profile to cereal box and made sure it was neat. I scanned the cereal-box template into my PC and used Inkscape to design the fins based on that template. The idea being that if I had it on the computer, then I wouldn't have to worry about losing the fiddly bit of cardboard. Now I can print out as many fin templates as I like and always know they'll fit to that type of bottle.

[Bibbleycheese]

Hi Bibbleycheese! I wanted to say that your launcher diagram is really NICE! Did you make that diagram from your launcher???

Hi Tim,
Yes I bodged the launcher together, and then drew the diagram using Inkscape. It would have been extra clever if I could do it the other way around (sigh). Still, the diagram shows the principle pretty clearly. Glad you like it. I've got some kids in school who were pestering me about how I did the launching, so I did the diagram for my googlesite.

Thanks to all for the very helpful advice. I've got loads of things to try out now, so I'll let you all know how things progress.

[RaZias]

There is a thing about your launcher...it hasn´t a abort valve, it should be between the quick-release and the non-return valve.

If there is no way to depressurise the rocket it will be dangerous for kids.
The abort valve will depressurise it if needed.

[U.S. Water Rockets1]

There is a thing about your launcher...it hasn´t a abort valve, it should be between the quick-release and the non-return valve.

If there is no way to depressurise the rocket it will be dangerous for kids.
The abort valve will depressurise it if needed.

Good point! You don't need to work very hard either.... get a plumbing valve from the hardware store and rig up a remote release so you don't have to get too close to open it and you're in business.

[castle-bravo]

nice man

[Bibbleycheese]

Here I am, back again after a long winter break.
I've rebuilt the launcher and included a pressure release - so we're safe now!
I spent some time today launching over the Ashdown Forest again - trying out a parachute and release mechanism I've been working on, as well as a 2-chamber setup with a Robinson coupling made of threaded lamp rod. The release uses an RC servo to pull out a pin and open a side flap.
The RC works well, and the door opens every time. Unfortunately I DIDN'T include a spring to force the parachute out, so it crashed and crumped.
Resorting to a lower-tech approach, I then wedged the parachute under a loose nose cone and tried again. This worked and showed the parachute off to the small crowd of spectators and their applause.
So... The launcher, the coupling and the parachute all work. Now to sort out the ejector. Back to the drawing board.
Here's my video.
[youtube][/youtube]

[Spaceman Spiff]

Thanks for posting the video. I have a few suggestions for the parachute. You may have thought of these already but I'll post here so others can take the ideas if they want to use them. One thing you can do is make a spring out of packing foam to push the parachute out. This works well because it has not hard edges to snag on. Another idea is to make a spring out of thin plastic that will recoil when bent. My last idea is used if you have a door with a spring opener like a rubber band that opens the door, in this situation you connect a hoop or ring of plastic to the door itself and rest the parachute inside the ring and close the door. When the door opens, the air flow blows the parachute out of the hoop and it deploys.

I miss getting outside and playing with my rockets! I can't wait until spring!

[Bibbleycheese]

Thanks for the suggestions. I'm going to try those out. I got so keen on the Release The Door mechanism, that I forgot the Push The Parachute Out bit. That'll teach me! Still, every launch is part of the learning process.
I like the idea of the door itself pulling out the parachute into the air stream. When playing around with ideas before I found that with spring tension behind the parachute pushing against the door flap, sometimes the pin got stuck and the servo didn't have enough force to pull it out. I haven't tried packing foam either. That squashes down quite well doesn't it? I'll give them a try in the rebuild.

[rockets-in-brighton]

Thanks for the suggestions. I'm going to try those out. I got so keen on the Release The Door mechanism, that I forgot the Push The Parachute Out bit. That'll teach me! Still, every launch is part of the learning process.
I like the idea of the door itself pulling out the parachute into the air stream. When playing around with ideas before I found that with spring tension behind the parachute pushing against the door flap, sometimes the pin got stuck and the servo didn't have enough force to pull it out. I haven't tried packing foam either. That squashes down quite well doesn't it? I'll give them a try in the rebuild.

Just a suggestion. You say the servo needs to pull a pin against resistance. Have you thought about swapping around the way it works so that force is not required? Tether the door closed by attaching a band from the door to the servo horn. When the servo rotates, the tether slips off the horn and releases the door. No resistance.