Cat pack distribution plate

Erik Bengtsson
Mar 3, 2006, 3:33 AM

to Rocket_Belt

Hi Clive,
I see it like this:
The baffles are needed because silver swells more when heated than steel
does. If the screen fits tight towards the steel walls at start, it will
compress even more when heated up. When cooled down again there will be
small channel between the steel wall and the silver screen package as a
result, so next time you fire up the Rocketbelt there will be a leak flow in
this channel.- A short cut with a flow of un-decomposed liquid HP. The
baffles are preventing this leak/by-pass until the whole pack is hot, when
the baffles are not needed any more because the silver screen pack will than
swell and fit well towards the steel walls again.
This phenomena will re-appear at all following cold starts of the Belt.
This is why you need the baffles. If it was not for this difference in
swelling, there would be no need of baffles, because the screen pack is
working well as a mixer so it re-distributes the flow evenly over the cross
section area.

Erik
www.peroxidepropulsion.com

Erik Bengtsson
Mar 3, 2006, 5:16 AM

to Rocket_Belt

Ky,
I agree 100%! The best practise is to give the engine a couple of fuel
"spikes" so the cat pack heats up, before start. This way of pre-heating
does realy not consume much fuel. I believe it is overkilling to install a
separate system for it, but I see your point.

Jodi Michaelson
Mar 3, 2006, 5:42 AM

to Rocket_Belt

Eric
It would be easy to do with a quick disconnect, if you wanted to conserve
fuel
Eric if you ever come to the US. I hope we can meet. You will have the time
of your life at my place if you like rockets. please send me a email and I
will
send you a picture of what I am working on now.
Ky

Jodi Michaelson
Mar 3, 2006, 6:08 AM

to Rocket_Belt

Eric
My wife Jodi, and I are going to Norway next year to run a rocket powered
Kick Sled I built
for a customer over there, for some kind of Festable. Maybe we could touch
bases then,
or you could come to Norway. and meet my friends there, and see the Sled
run. I have been
on a diet to lose weight, so far I have lost thirty seven pounds. as soon as
I get another
30 lbs off, I will be ready to fly my belt, and some other things that I am
working on.

Juan Manuel Lozano
Fri, Mar 3, 2006, 7:33 AM

to Rocket_Belt

If I understand you correctly you are asking why you don't inject the
peroxide just at the inner circle of the catalyst pack to avoid the
antichannel rings right?

First if you use just part of the catalyst pack you will not have a
total decomposition because you need all the area and as Eric say the
reaction on the chamber cause the peroxide to find it's way on the
wall or the edge of the catalyst and this causes a channeling that
will make the peroxide to pass the catalyst rough.

The antichannel ring ARE A MUST if you want an efficient rocket
engine because the rate of expansion between the stainless and the
catalyst pack screens is different and when the screens expands when
hot they are tight but when they cools a little bit it is formed a
gap between the catalyst and the wall of the chamber, also if you
open a rocket chamber and you measure with a micrometer you will see
that it have a bow or belly right in the middle and this is caused
because the rocket was used at high temperature and high pressure and
this deforms a little bit the body of the chamber tending to blow it
and this is also a cause of channeling.

The antichannel rings are only used in the first 1/3 of the rocket
because it is right at the liquid, and the foaming section that you
need to redirect the path of the peroxide, after this you don't have
to redirect anything because it is already a gas.

In the rocket belt you don't need to preheat the catalyst with a shot
of peroxide because the valve leaks a very small amount of peroxide
that helps you to do this preheat, it is normal that the first time
you fires your rocket it will make a white cloud until the catalyst
pack is "baked" after this you will have perfectly clean starts.


Juan Manuel Lozano

andrew dapolito
Mar 4, 2006, 3:22 AM

to Rocket_Belt

If I may interject an idea here. Would it not be possible to build some kind of canal system on the sides of the engine to redirect any flow back into the engine? Or then again the baffles would do that anyway. Or How about something that would force the screens to preheat like some sort of eletrical system.Just ideas. A preheat before blastoff?

JetJanitor

Erik Bengtsson
Sun, Mar 5, 2006, 6:17 AM

to Rocket_Belt

Hi Clive,
These are my explanations:
A body expands equally much in all directions.. If the diameter increases
with for example 10%, the cross section area will increase 1.1 x 1.1 = 21 %
and the volume increases with 1.1 x 1.1 x 1.1 = 33 %.
This is valid for an incompressible body. A compressible body, like the
catalyst package, will instead maintain its diameter, if the expansion is
prevented by the steel wall.

What happens when it cools down, is depending on whether it is a plastic
body or an elastic body.
A plastic body, like the cat pack, will shrink when cooled down, but an
elastic body would keep its dimensions.

To Summarize: A silver screen catalyst package is a compressible and plastic
body. That's why one get this gap towards the steel walls after it cools
down.