This blog covers the day to day progress of water rocket development by the Air Command Water Rockets team. It is also a facility for people to provide feedback and ask questions.

Wednesday, November 11, 2009

So far so good ....

During the week we made up four new spliced-pairs of 2L bottles. Each has a capacity of around 3.15L. The splicing and reinforcing technique seems to be working well so far. The Sikaflex is doing its job sealing the splices.

Today they were all pressure tested to 140psi without any leaks, and the bottles and tape showed no stress marks. We are very happy about that. Having a good yield rate means we can produce more of these with less bottles.

Now they will all be assembled into a Polaron type rocket. The initial target launch pressure will be 130psi with a 15mm nozzle. While we are building this rocket we will continue to make up more spliced pairs for the rest of Acceleron. Some of these will also be converted into boosters.

I think I have an approach too now for the pressure switch, so I'll be doing some prototype work on that soon.


Anonymous said...

hey george will this polaron rocket get boosters and have a higher volume in liters ??

George Katz said...

Anon: The first test flight of these will most likely be a single stage rocket. The total capacity will be around 12.5L. So comparable to the other Polaron rockets. The plan is to use these particular spliced pairs in the Acceleron V rocket, so they won't see a lot of flying time in the Polaron rocket.

Eventually the plan is to build new Polaron rockets with these types, including the boosters.

Matt K said...

Hi George,

first time visitor so apologies if you have answered this elsewhere, but it seems to be quite a bit of work joining the bottles together and I had a question:

Given that you're gluing plastics anyway so creating pressure-proof seals is not an issue for you, other than that the transparent look is very cool, is there any particular reason you don't use a piece of plastic drainpipe for the main body and perhaps also for the boosters?


George Katz said...

Hi Matt,

It's actually a good question. One of the main reasons is that PET is a very strong and light plastic. Its strength to weight ratio is significantly higher than PVC which most drain pipes are made of. PET also does not shatter the same way as PVC does when it fails.

PET bottles already have a nice neck and throat which makes them easy to use directly. We would have to machine something similar for the drain pipe to withstand the pressure and easily connect nozzles.

People have made water rockets from PVC pipes, but because of the weight the rockets usually tend to under-perform when compared to PET bottle based rockets.