steam rocket

[ernie wrenn]

Chris..

Think pointed helmet and a stick in the ass. Instant Bottom Rocket.

Kinda like the 3 rocket engines with 1 second delay. Up...delay... 90 degree left turn... delay ....90 degree left turn.. Lawn Dart.

ernie

[mator]

I have made de Laval nozzle for my steam rocket. That was first developed by Swedish inventor))) I learned it when studied up for liquid and gas mechanics exam. Before I thought that he was French)))

[Johansson]

Nice! One thing you could do is to fit a steel pickup tube inside the bottle so the nozzle always is fed from the bottom of the bottle where there is no steam.

In the video you posted you can tell that lots of steam was reaching the nozzle from the way the jet plume behaved, with only water reaching the nozzle there is a strong, constant jet plume for a couple of seconds and then it stops instead of smoking and spluttering for halv a minute.

Another way of getting this effect is to slightly tilt the bottle.

[mator]

But what about your tests with horisontal placing bottle?
www.youtube.com/watch?v=1qaJmlAhkD4

[Johansson]

The bottle is slightly tilted backwards but you can see and hear clearly after a couple of seconds that the water level has dropped below the nozzle inlet.

The jet plume becomes much wider and it takes forever before it runs out of steam, you can see the difference between this video and the one where we ride it on the lake. Then it runs hard for 5-6 seconds and then just quits.

[mator]

Ok. Now I have some things to experiment with.
I dont see any differences between first seconds of run and after about 10seconds. But I hear. It is for static test.
And for run on a lake I only can say that it is working less time. Is it really working less time?

So you say that into throat must be water, not steam? Is it writen so in a book of steam rockets? So personally I felt that there should be steam, because it is coercible gas and liquid water is incopmressible. Or water transform into steam because of decreasing pressure (by Bernoulli's principle in place where speed is growing pressure decreasing)?

[racket]

Hi Mator

Steam weighs less than water , .......................thrust is MASS times velocity , we need the greatest mass flow per second , so water is preferable to steam .

Cheers
John

[mator]

Hi Racket!!!!

But if steam weighs less than water, so with same pressure in bottle it, (steam) will exhaust from nozzle with faster velosity.

[Johansson]

Nope. Even if it does you would still get just a fraction of the thrust you would get with water since the mass is so much greater.

It is against the laws of physics to get high thrust from steam ejection, if you release the steam from the bottle the pressure will drop instantly and the water cannot boil off fast enough to produce the amounts of steam needed to both hold the tank pressure and produce any useful thrust.

[mator]

Convincing. I think that it is nearly the same words that I want to hear.
So where in this way (bottle vertical, nozzle down) water transforming into steam? In what part of rocket? In throat or before or after throat?

[Johansson]

The water starts to evapourate after the throat in the divergent section of the nozzle and continues to do so after it has left the nozzle as well, you can tell by the way the steam plume continues to expand for several meters after it has left the nozzle.

[mator]

Ok... It is not so easy as I think before))))
But what about book? You promised me to take photos of it.

[Johansson]

Damnit! I forgot, will get right to it!

Edit: You´ve got mail.

[mator]

And maybe it will be usefull for some people, if you upload it in this theme in this forum (post here link where to download).

[mator]

Very very, very big thanks for a book!!!!!!!!! I am sure that I will read it all, even despite little problems with english)))