Re: Napkin drawing

[JHByrne]

In a message dated 10/31/2002 4:35:11 AM Alaskan Standard Time, [EMAIL PROTECTED] writes:

This is my vision of a bigger scale model;

http://www.cs.umu.se/~fys98mrn/napkin_design2.bmp

Gail, Dennis, we need to get Marcus' drawing into a rough sketch file somewhere, along with Joe's preliminary drawing.

It pumps water from behind it through an internal pipe stuffed with
heating elements and a turbine, and then then the water is ejected out the
front through a directional "nozzle".

My idea for a nozzle is a sphere with a hole through it. By rotating
the sphere, the jet changes direction.

How do you rotate the sphere, or otherwise change the nozzel?  Sure, a showerhead nozzel would work, but how do we change the facing of the nozzel?
Is it necessary to have the nose nozzel move, or is it enough to simply have it blow water out?

Another possible design is using something like modern jets use to direct
their exhausts, but I think that design is even more vulnerable.

Yes.  We have to figure that 1)  a terrestial glacial model must contend with rocks and gravel embedded in the ice, and 2)  an actual Europa model would have similar problems with meteor chunks and sulphur/salt deposits, etc.
So, we need to have as few moving parts as possible.

It's Teflon coated both on the outside skin and on the skin of the
internal pipe. Does the skin need heating for the tests? Won't the warm
water flowing around it be sufficient?

And where should the turbine be placed? In the front or in the rear? Or
perhaps there should be two smaller turbines (improved safety?)

How do we keep these turbines from clogging?  An internal conduit... wouldn't that clog with mud and sludge?
We have to remember, that the actual 'ice' won't be pristine, either on a terrestial glacier or on Europa.  Europa, remember, is continually flying through clouds of Io's sulphur, and peppered with asteroids and chondrites.
So, if we're going to use something like a turbine, a major priority MUST be keeping them from clogging.

I placed the batteries as far to the front as possible, since they'll
probably be quite heavy, and the CM should be as far to the front as
possible? Could motorcycle batteries be used for the model?

I hope so... snowmachine batteries might also work.

I've been considering the pro's and con's of this design, and these are
the ones I've thought of;

Pro's
* Water flowing all around it, preventing it from freezing.
* Lots of space in internal pipe to add turbines and heating elements.
* Wide internal pipe gives slow flow, giving more time for heating
  elements to work. The narrowing on the pipe before the "nozzle"
  increases speed of water, making water jet more effective.

Those heating elements are going to have to be covered, so as to not be exposed to potential clogging.  As currently drawn, the heating elements could be snags for rocks and silt.

* Single nozzle, no fuzz.
* ...add your own comments here...


Con's
* Turbines are vulnerable to debris (perhaps simpler propellers will be
  sufficient?

Maybe a hot-tub (sauna) propeller.  The Jacuzzi brothers developed the spa turbine from airplane propellers.  That company would likely know a thing or two about how to keep a turbine functioning in somewhat dirty water, ie, perhaps we can contact a spa company, for pointers on building a turbine.

* A bit complex to build.
* Turbines will have to be shut down in order to release any transponders.
  Otherwise there´s a high risk of having transponders being sucked down
  the pipe and into the turbines. Shutdown periods should be kept to a minimum
  to minimize risk of freezing.

You drew the transponders as rear launched missiles.  That's exactly what I was also trying to transmit in the original concept plan.  If they're simple animal transponders with a model rocket engine fastened to them, then we can drop them into little holes in the rear of the model, like bullets in a revolver, just as you have drawn.
An advantage here is simplicity:  one little electric current is all it takes to launch a transponder, that is, press a button on your control device, and shoot the transponder.
To prevent the transponder rockets from getting jammed with dirt while still in the probe itself, simply seal them under a little plastic wrap.  A model rocket engine will just rip through the plastic wrap seal, and have enough force to shoot the transponder into the ice slush at the rear of the model, where it will quickly refreeze, holding the transponder in place.

* Nozzle design is a bit vulnerable to debris getting in on its sides and
  jamming it. Will the water jets be able to keep it clean? Will there be
  eddies that trap debris around the nozzle, increasing the risk of
  jamming it?
* The model needs water all around it to function, thus it need some help
  getting down into the ice before it can work properly. This might
  envolve drilling, dropping down the model into the hole and then filling up the
  hole with antifreeze.
* ...add your own comments here...

I see nothing wrong with launching it at an angle from a small scaffold.  An actual Europa probe would similarly be launched from the lander.
If the probe can't bore into the ice directly from the scaffold, it's not too much of a 'cheat' to dig a small hole for it to allow it to get moving forward.

-- John Harlow Byrne

/Marcus

Ps.
I´m a university student at Umeċ, Sweden, so I guess I won´t be able to do
any hands on work on the models.

I know that there is a model submarine builder of great skill in your immediate neighborhood.  I'll see if I can track him down, and put you two in contact with one another.
Keep posting, Marcus!

-- JHB