SWPOTD (Silly Web Page Of ...)
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From: Peter Langston <psl>
Date: Mon, 16 Sep 96 09:56:26 -0700
Subject: SWPOTD (Silly Web Page Of ...)
[References to URLs [in brackets] are listed at the end. The following text
is from ... -psl]
Launching Stuff With Liquid Nitrogen
Warning! The stuff described here is a little outside of our ordinary
experience. The experiments described on this page were conducted by
grown-ups. Kids: Don't do this at home. Just because we did it, doesn't mean
it is safe. If you do this kind of thing and get hurt, maimed, killed, or
disenchanted, you did it on your own. We had nothing to do with it.
For reasons few of us remember, talk at the lunch table one day turned
toward the problem of launching a block of _SPAM(tm)_ luncheon meat over
a distance. Immediately many engineers had visions of _a surgical tubing
slingshot_, or a catapult, or a potato cannon variant. Paul Wade (of
Digital's Networks Business Unit) suggested using liquid nitrogen. At the
time the approach seemed infeasible. But then a few of us noticed Mark
Feather's web page describing a _Liquid Nitrogen Powered Rocket_.
That cinched it for the team of Dan Jackson, Matt Reilly and Tad Truex. They
were bound and determined to build a food product launching system that used
liquid nitrogen as its power source. Dan did some calculations that
indicated impressive energy could be liberated from a small quantity of
liquid nitrogen. Tad and Matt giggled a lot.
The three collaborators spent a lunch hour at the local Home Quarters buying
plumbing supplies. This is what they built one evening in the Graphics and
[image showing a piece of pipe with one end on a tripod goes here... -psl]
Tad is on the left, Matt is on the right. Dan is out of view, behind a video
After lots of chasing around for the appropriate equipment, Dan and Matt
bought some liquid nitrogen at a local welding supply house. Tad bought some
vegetables. (_SPAM(tm)_ has gotten so expensive since its rise in
popularity among harried two income couples, that we judged it more
economical to use vegetables and fruits for the test sessions. Besides,
potatoes are round, (_SPAM(tm)_ is not, and so it is more difficult to
fit in the launch apparatus.)
The first launch (of a peach) was not a spectacular success, resulting in
a distance of less than 12cm. It was, however, a proof of concept.
After some re-examination of the loading and trigger apparatus, the
collaborators changed the design a little, and were pleasantly surprised. We
proceeded to launch several potatoes, some onions, and another peach or two.
In this image, you can see a peach flying over the overflow parking lot at
Digital Semiconductor's HLO facility: (For a larger view look _here._)
[A picture of sky (mostly) goes here... -psl]
Here's a picture of the water spout leaving the barrel of the nitrogen launcher:
[Yup, the water spout is clearly visible... -psl]
David Sarrazin is in the background, shielding his eyes from the blast.
Thanks to Samantha Truex for the photographs. They were taken with a
disposable camera. Didn't they turn out nicely?
Digital Semiconductor (a part of _Digital Equipment Corporation_)
developed a really cool _video codec chip_. Last fall a few of the
developers produced MPEG video files from video of the launches using an
early prototype of the 21230. (These files have been edited to shorten them
up a bit. They were encoded in real time (at 30 frames per second) from an
8mm video tape. This is really cool.)
* A _close look_ at a launch of a potato. (The file is 1.45MB long.) Dan
Jackson is at the control valve. Tad Truex loads the nitrogen. Matt Reilly
screws on the specially designed pressure relief cap. David Sarrazin is
holding the camera.
* A _wider view_ of a launch of a potato. (The file is 1.14MB long.)
Same cast, with a few bystanders. Notice how the smart ones back off just
before the valve is turned. (And check out the little cloud of dust raised
as the potato hits the ground.)
Watch this space for compressed (mpeg) video of a NEW version of the
Food Transport System! Compressed air! Greater distances! SPAM!(tm)
© 1996 Peter Langston