- This topic has 43 replies, 12 voices, and was last updated 14 years, 8 months ago by
Kyle Parsons.
Kyle Parsons.-
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Kyle Parsons
Hey everyone,
I have quite the engineering question that I need some ideas on. In my Engineering Projects class, we have started our final year project. I convinced my group to try to make a steam powered rocket motor. Here is the basic outline of the design and process we are trying to re-create.
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-The upper container will hold all water, in a perfect world no air.
-The upper container will be sealed and then heated to temperatures above boiling point
-The upper container will be pressurized using a water pump to a specified PSI
-Then on demand, we will open a valve at the bottom of the tank releasing the water as fast as possible into the nozzle
-When the water that was under pressure comes in contact with atmospheric pressure, the boiling point will go back to 212 degrees (When the water is in the upper container and pressurized, the boiling point will be much higher then normal) it will “flash” into steam, and expand dramatically
-The steam will move out of the nozzle and create thrustWe have come to a couple of problems in the design. First we can’t find a valve that can do three things. Withstand extremely high temperatures and pressures, and most importantly release the water quickly enough so the system doesn’t bleed out. Second we don’t know a way to heat the water once it is sealed in the upper container and raise it to roughly three hundred degrees.
Any thoughts? I have had sessions with many professors going over equations of thermodynamics and dynamics to find equations for this system. Even if we do find equations we don’t know how to actually build it physically.
Anonymous
I’m an engineer..to bad it’s on a fire engine.
Anyway. One of our old club memebers used to fly steam rockets and at one point he brought a steam powered go cart. I watched as heated up the water and remembering how he had a wet rag over the “on/off’ valve. It looked to be just a normal looking 1/4 turn gas valve. He had a piece if rope tied to it that ran up front of the go-cart. Once he pulled the cord he was off. IIRC it went pretty fast but was of short duration. You might do some googling ..his name is William Inman.
Tony
John A. Wilke
Three words: “Strap on boosters”. I say we weld some 98mm casings to that Bessie and really move things along.
No need to thank me – I’m glad to help 😀
Kyle Parsons
Thanks John that helped immensly
Adrian
Hey everyone,
I have quite the engineering question that I need some ideas on. In my Engineering Projects class, we have started our final year project. I convinced my group to try to make a steam powered rocket motor. Here is the basic outline of the design and process we are trying to re-create.
Uploaded with ImageShack.us
-The upper container will hold all water, in a perfect world no air.
-The upper container will be sealed and then heated to temperatures above boiling point
-The upper container will be pressurized using a water pump to a specified PSI
-Then on demand, we will open a valve at the bottom of the tank releasing the water as fast as possible into the nozzle
-When the water that was under pressure comes in contact with atmospheric pressure, the boiling point will go back to 212 degrees (When the water is in the upper container and pressurized, the boiling point will be much higher then normal) it will “flash” into steam, and expand dramatically
-The steam will move out of the nozzle and create thrustWe have come to a couple of problems in the design. First we can’t find a valve that can do three things. Withstand extremely high temperatures and pressures, and most importantly release the water quickly enough so the system doesn’t bleed out. Second we don’t know a way to heat the water once it is sealed in the upper container and raise it to roughly three hundred degrees.
Any thoughts? I have had sessions with many professors going over equations of thermodynamics and dynamics to find equations for this system. Even if we do find equations we don’t know how to actually build it physically.
I don’t know much about steam powered rockets, but this does remind me of when I was in high school, trying to sanitize a bike water bottle in the microwave. I filled it with water, heated it up nice and hot, and it was just sitting there. Then when I grabbed it, the nozzle opened and a stream of superheated water/steam came out and took the skin right off of a patch of my abdomen. If I remember correctly, it didn’t generate that much thrust because the water boiled off into steam after it left the bottle. I guess that’s what your 12″ section is for.
Also, there was a Mythbusters on this subject, where the three younger crew had a contest to see who could make the highest-flying steam-powered rocket. Turn out it was the one who built it the lightest.
For heat, you will definitely want something you can turn on and off remotely (very remotely). That probably means electric heat. Some resistive heating elements and insulation would probably do the trick. Also make sure to have some remote temperature sensing. I don’t have an answer for you on the valve. That’s the hardest part of any similar device. I was working on a compressed gas deployment system once and ran into a similar problem.
Dave Smith
I wouldn’t consider myself an engineer, but I like to day dream.
for the valve: how about a round ball resting against the bottom of the boiler tank as it sits on the pad. It would have to melt/flash at the particular temperature that the pressurized water is heated?
There must be some kind of concoction of Mother Nature or Mankind that provides the right combination.
How to heat it?
as a kid, the magnifying glass offered untold hundreds of episodes of spontaneous combustion.
crazy ideas but fun
Kyle Parsons
Adrian: Like most water rockets built as a kid, the “thrust” is mostly the water pushing agianst the ground pushing the bottle up. In this case the steam should expand and if the diameter is small enough actually create thrust. Thats the hope anyway.
For the valve, a couple of ideas have gone around. One is we make a break valve, where at a certain pressure or heat, it will break open. A other idea is a boiler valve, because they are used to withstand high pressures and temperatures.
Rocketwhiz
The kind of valve your describing is a boiler relief valve. Problem is they are heavy, and the smallest size they usually come in is 3/4″
Another possibility would be a pneumatic solenoid valve. They would handle the pressure but I’m not sure about the heat. They tend to be smaller, maybe too small
Using a heating element from a water heater would require external power until right before lift off. Plus a way to monitor pressure and temp.
The combination of Sch80 pipe, valve, heating element, pressure and temperature monitoring is going to make it pretty heavy. I say go with the 98’s
Kyle Parsons
Were not actually trying to put it in a vehicle and attempt a launch. We were going to make a test stand for it so we could get data off of it. We looked at solenoid valves, some of them can get up to 200-300 psi which is still to low, and cant hold the temperatures. On top of that there 250$ plus.
Warren B. Musselman
Firstly, I would consider a “burst disk” instead of a valve. They are available in precisely calibrated pressure ratings and were extensively used in Apollo and in other expendables for a wide variety of purposes.
A resistive heater would probably be the best option, but the electricity source for such a high current requirement should certainly be left on the ground. Think multiple car batteries and a detachable umbilical.
Kyle Parsons
Anonymous
John A. Wilke
Adrian
Dave Smith
Rocketwhiz
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