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Launching Stuff With Liquid Nitrogen [by Matt Reilly]

- Now with MPEG Video!

- 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 [Defunct URL http://reality.sgi.com/employees/dbg/antics/] 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 [Defunct URL http://reality.sgi.com/employees/mark/alrocket/] 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 Multimedia lab.


Tad is on the left, Matt is on the right. Dan is out of view, behind a video camera.

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, ([Defunct URL: http://sp1.berkeley.edu/findthespam.html] 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.)


Here's a picture of the water spout leaving the barrel of the nitrogen launcher:


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 [Defunct URL http://www.digital.com/.i/info/semiconductor/dsc-21230.html] 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.)

- Watch this space for compressed (mpeg) video of a NEW version of the Food Transport System! Compressed air! Greater distances! SPAM!(tm)

- Return to Matt Reilly's Web Page.

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