Wednesday, September 3, 2008

Mark II Menticulator Cola Deployment Device Tests

Please go down two posts for the original report on our first experiment -- thanks!

As mentioned in the post reporting the results of our initial microgravity tests, the Mark II Menticulator will require a more sophisticated method of deploying a nicely sized sphere of soda. My initial thought was to use a water balloon, but an afternoon of sweaty testing on the back porch lead to the discovery of several serious problems with this approach.

The first is that when the balloon ruptures, friction between the skin of the balloon and the water results in significant spray, some of which is clearly fast enough to overcome the surface tension of the water (and remember, the soda will have a lower surface tension because of the sweetener and other ingredients). If some of this spray coats the camera port, we may not be able to see the reaction. I did multiple tests with different balloon sizes and tensions, and even coated the inside of the balloon with oil, in an attempt to reduce the spray, with no real change in the results.

But an even more serious problem is that unless the balloon is under a significant amount of tension, it will either not puncture at all, or the puncture will not propagate! If this happens in flight, we will experience a total menticulation failure and the entire experiment will be ruined.

So it was back to the drawing board (I have an ACME drawing board, the same brand Wile E. Coyote uses). I had to come up with a method of simply and smoothly deploying the soda. When I'm faced with a problem like this, I like to sit in the workshop and idly play with the various parts and tools that I have available. What I'm looking for is relationships between things that will spark a connection. After a while, this idea came to me.

The initial idea was to use a balloon inside the soda bottle to force the soda out of the bottle and up a tube into the apparatus. I already had the tube -- the Geysertube that Steve Spangler sent to me earlier in the year. I drilled out a hole in it so I could insert some plastic tubing, inserted a bit of copper tubing into the end of the tubing to stiffen it, ziptied a balloon onto the end, and stuck the other end into a hiking bota-bag, which acts as the bellows. A little hot-glue and tape sealed everything up.

Squeeze the bag, the balloon inflates, and liquid is forced up the tube in a reasonably controlled manner (this test had a leak, thus the bubbles).

Okay, so now I've got a basic method of deploying the soda sphere. The next thing to work on is, once I have the sphere deployed, how do I test the convection hypothesis in a manner that leaves no room for doubt about the results, and is as simple and foolproof (always a plus when I'm involved) as possible.

I'm also looking for a more precise method of pumping up the balloon than the bota bag (which was just the cheapest thing I could find that would work reasonably well). Something like a really, really big industrial syringe (500-1000ml!) would be perfect, but I haven't been able to find one yet -- if you know of something that might work, in particular something that's effectively self-locking, so after I get the bubble to the right size, I can just let go and the balloon will stay its current size, let me know!

Subsequent to these experiments, the blog got slashdotted, and I started getting lots of suggestions. One that I'm definitely going to follow up on in the near future is a modification of Ger's suggestion about a box of cola; my current thinking is to build a thin enclosure that will confine the convective flow pretty much to two dimensions.


Mark Mellors said...

Some ideas I've had for your pump:
~caulk gun:
easy to meter small amounts
fixes in place once dispensed can't be used to suck
~bike pump: needs modding to stay fixed in place, maybe just use small progressive pumps?

Other ideas for dispensing a sphere of cola:
~partly frozen balls of cola, melted with a radiant heater (does freezing reduce the CO2 content?)
~squeeze from ziplock bags/sachets
~use tubes with caps on both ends. remove caps, cola should slide out when you move the tube.
~pass it through a fine hydrophobic mesh (polyester fabric?) on the way out of a regular bottle should allow more controlled flow and droplet size.

Can you inflate/pressurize your main bag rather than use a rigid box? (you can plastic weld/fuse some clear plastic sheeting, this could allow you to have a larger enclosure that's still practical to carry around.)

good luck and have fun!

PONZ said...

Hello Mad Overlord!

I am an Artist and teacher about to take flight on a Zero-G flight on December 7th! Needless to say, I am psyched. Bye the way, I love your blog page. Our Physics teacher also posts his "Mad Scientist" type stuff online. I am forwarding him this address after I enter this note.

If you are interested, check out my blog page

I hope to film some color and ink interaction, but I do not have a special camera. Any suggestions?
Thanks and Cheers, PONZ

MadOverlord said...

PONZ, good luck on your flight; I emailed you some suggestions based on my experience, hope you got them and found them useful. said...

I love your posts. I have a casio ex-f1 and I am trying to develop a reomte trigger release for the MOVIE camera. The remote that comes with camera only controls the still camera. It would be great to add a TTL trigger. I just don't know where to begin or who I can send the camera to for the modification.
Any thoughts?

MadOverlord said...

I don't think it's possible, short of either (a) physically hacking the camera or (b) adding a motorized device to press the button (say, using a servo).

Note that either approach will still have a delay before the recording starts.

It might just be simpler to set the camera recording and then review the results later to see if what you wanted was caught. A 4G memory card holds about 30 minutes of high-speed.