Interesting "High Pressure" Web Page

Water Rockets NSW

Moderator: Moderators

Tarpazium
Engineer
Engineer
Posts: 1178
Joined: Mon Apr 23, 2007 10:23 pm
Location: "Dark Side of the Moon", Brisbane. Australia

Interesting "High Pressure" Web Page

Postby Tarpazium » Thu Aug 30, 2007 7:29 am

Hi Guys

I just found an interest and informative web portal that relates to water rockets.

Image

So let "Fire and Smoke" give way to "Spray and Mist", grab a cup of coffee, sit down, settle back and have a good read.

(Click on link below to access "High Pressure" Portal)
http://www.sumrallworks.com/rockets/main.php3?area=links&link_type=rank

Talk to you all soon ......

Tarp

P.S.

After reading some of these pages, I am convinced, that the only reason why many more of us are not flying these rockets here is Queensland, is probably solely due to the current severe "water shortage" crisis :D .

You know however with all the recent floods in Gympie/Sunshine Coast area, I did hear a whisper of a rumour, that ~RR~ (Shane) who lives there, was working on this type of launch vehicle. I also heard that it would have the capability of parking a payload in low earth orbit due to the availability of local fuel. ...... but then again that still just a rumour :D :D .

Image
(Sunshine Coast Rocket Fuel Depot)

Tarp
“Measure what is measurable, and make measurable what is not so.”

[IMG]http://i103.photobucket.com/albums/m149/tarpazium/jz1afQl.gif[/IMG]

air.command
Astronaut
Astronaut
Posts: 1907
Joined: Mon May 14, 2007 11:18 am
Location: Sydney, Australia
Contact:

Postby air.command » Thu Aug 30, 2007 6:29 pm

Hi Tarp,

Yup, Tim has a good website there with lots and lots of great information. He is on a couple of the water rocket forums. I've corresponded with him a few times and he knows his stuff.

hee hee .... when was that photo taken of the big pinapple? Was that during the recent rainstorms?
Crop Circles: ... just a bunch of guys looking for their rockets ....

spacelaunch
Rocket Crew
Rocket Crew
Posts: 439
Joined: Sat Aug 11, 2007 10:07 am
Location: Queensland
Contact:

Postby spacelaunch » Sat Nov 15, 2008 12:16 pm

Ultimate high pressure project ..

I have been thinking about this for while and there is several issues in water rockets that could be addressed to significantly boost altitude.

1/ Pressurant gas - Air pressurant is the least effective, and requires around 50% or more of your water tank be used for air (ullage). This greatly reduces your water loading capacity, thus your effective impulse. This scheme of pressurization is same as what is called "blow down" when used in liquid fuel rockets, to deliver the propellants from the tanks to the motor.

Some possibilities to address this

a/ Use a constant pressure source - such as a small CO2 cart to constantly pressurise your tank during flight. You could mode a small bike tire inflater for this job.

b/ Use a compressible gas such as propane to pressurize the ullage, this would be loaded in as a liquid and expand to gas during operation. The end result would be almost constant pressure and thus thrust, and decent gas impulse at the end also. Hydrocarbon gases are excepted as environmentally friendly propellants so no issue there.
Space is only 100km straight up, see you there :)

air.command
Astronaut
Astronaut
Posts: 1907
Joined: Mon May 14, 2007 11:18 am
Location: Sydney, Australia
Contact:

Postby air.command » Sat Nov 15, 2008 1:31 pm

Hi Spacelaunch,

I know exactly where you are coming from. It would be nice to work on a really high pressure rocket. Something I'd like to eventually pursue, although dad is constantly warning me of the associated dangers. He has had almost 50 years commercial experience designing high pressure valves and regulators and is aware of the things that can go wrong. He builds all our launchers.

We already have a couple of carbon fiber tanks normally used in fire fighting breathing equipment. They will easily hold 450 bar and are very light. We are working on how best to utilise them in a rocket due to the freezing effects on valves in releasing all the pressure.

One big problem with water rockets is the weight of the pressure chamber. High pressure requires heavier construction which to some extent negates the higher pressure capacity.

An interesting variation I have heard discussed has been where the pressurant gas is stored in a high pressure chamber(and heavier), but the water chamber is a much lighter chamber made to only hold lower pressure. The gas is fed in regulated so as not to cause water chamber to rupture. This gives you the more constant pressure you are talking about.

Here is a video of how scuba tanks behave with their valves cut. There is a shot of a couple of CF tanks as well. Our CF tanks are slightly larger than shown here. You can see how well they go with gas alone, if only they had fins and a nosecone. :D

http://au.youtube.com/watch?v=tyINNUaXa8Q

We are still well away from building rockets based on these..... but one day somewhere in the outback..... :)

Utilising propane as a pressurant gas is certainly an interesting option. From memory I think propane's vapor pressure is only about 150-170psi at regular type temperatures which may or may not be enough for higher pressure rockets, but something that should be relatively easy to test.

Liquid CO2 would be better I think, but then you have the problems of it freezing everything so you need good insulation. But not out of the question.

A heavier gas like CO2 also gives you a little bit more efficiency in the air pulse phase because it has more mass.

So seriously though what do you think is the best way forward to building a high pressure rocket?
Crop Circles: ... just a bunch of guys looking for their rockets ....

spacelaunch
Rocket Crew
Rocket Crew
Posts: 439
Joined: Sat Aug 11, 2007 10:07 am
Location: Queensland
Contact:

Postby spacelaunch » Sat Nov 15, 2008 4:06 pm

Hi Spacelaunch,

I know exactly where you are coming from. It would be nice to work on a really high pressure rocket. Something I'd like to eventually pursue, although dad is constantly warning me of the associated dangers. He has had almost 50 years commercial experience designing high pressure valves and regulators and is aware of the things that can go wrong. He builds all our launchers.

## Yup you would want to insure you are well away from any experimental high pressure system, when charging it. Fragments of composite, plastics etc could enter the body if you had a failure. And would be difficult to find and remove - not pleasant.

## I am not totally convinced that extreme pressure is the answer here though. Looking at the water rocket calculator it seems many people are banking on very high thrust for around 0.5 sec or so. This not really optimal as most of the kinetic energy lost right near the pad. Not only this but the very light weight bodies people are building have little momentum left once boosted. If you check the calculator as with all rockets you will find there is an optimum weight at which you get the best performance and it is not the lightest weight possible. As most would assume.

We already have a couple of carbon fiber tanks normally used in fire fighting breathing equipment. They will easily hold 450 bar and are very light. We are working on how best to utilise them in a rocket due to the freezing effects on valves in releasing all the pressure.

## Dependant on which gas you are using here and the flow rate in question. Certainly NOX and CO2 would be an issue. I remember at one point seeing people load water rockets with dry ice maybe that would be a go.

One big problem with water rockets is the weight of the pressure chamber. High pressure requires heavier construction which to some extent negates the higher pressure capacity.

## See my above response this is not always a bad thing, especially if you have very high launch thrust.

An interesting variation I have heard discussed has been where the pressurant gas is stored in a high pressure chamber(and heavier), but the water chamber is a much lighter chamber made to only hold lower pressure. The gas is fed in regulated so as not to cause water chamber to rupture. This gives you the more constant pressure you are talking about.

Here is a video of how scuba tanks behave with their valves cut. There is a shot of a couple of CF tanks as well. Our CF tanks are slightly larger than shown here. You can see how well they go with gas alone, if only they had fins and a nosecone. :D

http://au.youtube.com/watch?v=tyINNUaXa8Q

We are still well away from building rockets based on these..... but one day somewhere in the outback..... :)

Utilising propane as a pressurant gas is certainly an interesting option. From memory I think propane's vapor pressure is only about 150-170psi at regular type temperatures which may or may not be enough for higher pressure rockets, but something that should be relatively easy to test.

## This one just crossed my mind recently as good candidate, as it is cheap and moderate in pressure. But has the advantage of being an expanding liquid with a good density. Raw propane is usually about 120psi at room temp. All you need to do is turn you bottle upside to extract liquid propane into your rocket.

Liquid CO2 would be better I think, but then you have the problems of it freezing everything so you need good insulation. But not out of the question.

A heavier gas like CO2 also gives you a little bit more efficiency in the air pulse phase because it has more mass.

So seriously though what do you think is the best way forward to building a high pressure rocket?

## A couple of options.

a/ Thin wall alloy tube would need to be seamless draw stuff
b/ High strength poly tube (polycarbonate) with carbon overwrap

## I still think the key is the pressurization though - I will do some math on using liquid propane in the ullage and let you know.

## Another possibility would be chemical pressurization - what just occurred to me is one could use low concentration peroxide (below 50%), and allow it to mix with catalyst at its top surface. Result would be warm steam that would force the liquid out.

## If it is extreme altitude you want maybe you could consider a boosted dart arrangement, these transfer the momentum of the propulsion into a much smaller more aerodynamic body that coast on to higher altitudes.
Space is only 100km straight up, see you there :)

Kryten
Astronaut
Astronaut
Posts: 1977
Joined: Wed Oct 24, 2007 11:06 am
Location: Sydney

Postby Kryten » Sun Nov 16, 2008 7:27 am

spacelaunch wrote:I remember at one point seeing people load water rockets with dry ice maybe that would be a go.

I'm thinking the same thing - but maybe the rate of gas generation isn't fast enough?
"Pub, ah yes. A meeting place where people attempt to achieve advanced states of mental incompetence by the repeated consumption of fermented vegetable drinks" (“Timeslides”)

air.command
Astronaut
Astronaut
Posts: 1907
Joined: Mon May 14, 2007 11:18 am
Location: Sydney, Australia
Contact:

Postby air.command » Sun Nov 16, 2008 8:45 am

Kryten wrote:
spacelaunch wrote:I remember at one point seeing people load water rockets with dry ice maybe that would be a go.

I'm thinking the same thing - but maybe the rate of gas generation isn't fast enough?


If it is a surface area issue that determines the rate of gas generation perhaps one could crush the dry ice into smaller pieces.
Crop Circles: ... just a bunch of guys looking for their rockets ....


Return to “Air Command Water Rockets”

Who is online

Users browsing this forum: No registered users and 1 guest