Ice Cannon

I would suggest de-gassed water would be the best option and casting in a smooth-walled mold.

Would a little corn-starch as an additive be of any advantage?

They could always try pykrete in addition to normal ice, although this would probably require a mould.

Noticed your post, cyber. I suspect with pykrete the cannonball would scrape shavings out of the barrel, pile them up in front of it, and get stuck, leading to the whole barrel exploding. Perhaps a coating of regular ice on the inside ? (I have no idea how to do that)

*added*

Heck, thinking about it, no one has defined that the cannon needs to use gunpowder either. Why not use compressed air?

Well, originally I though of a "normal" cannon, meaning one using explosives - most probably powder - to propel the cannonball. And, of course, one made of ice, meaning no additives whatsoever. Maybe the degassing idea (haha, first I wrote "degaussing" ) is a great one, I guess that would make the glass barrel notioceably tougher.

bio

This strikes me as one of those rare ideas where MB could try all of the above, heck you could add 'spud-gun' to the potential designs here. (In fact that might make for a viable projectile for proof of concept shots).

Let me see, figure maybe one or two days of small-scale testing to figure out the best type of ice to use - which they can do in the shop. Another day to create several moulds, a day or two to freeze the water and two days for location testing...

That would net them a small armies worth of ice cannons they can test and fall within the week or so of filming time they have while leaving a couple of spare days if they have any significant problems - which *should* be long enough to allow them to re-cast the ice cannons and test them if things went REALLY wrong at some point.

The biggest problem would be transportation, although if they are filming in sub-zero temperatures refrigeration might be a minor issue.
Might be simplest for them to make each cannon no longer than three feet or so in length, which should give them something large enough to test and small and light enough to move around quickly. Maybe they could use ping-pong balls injected with foam or cement as ammunition - cheap, simple, expendable (which 'conventional' solid shot isn't), less likely to chip or damage the barrel while being loaded, could be produced in large amounts to allow for more firings than they are likely to have time for and would allow for a much thicker barrel in relation to the bore size (and hence a smaller and lighter cannon) than would be the case with anything else.

Would it be worth it to post a link to this site on the new boards in hopes that some of the researchers see it and maybe come and check out the Citadel? Or would that be bad?

Cybermortis: what about using tennis balls for ammo with the same foam filling? they would be somewhat larger with bright colors and more visual for filming. The fuzzy outside might also act as a sort of wadding for the bore.

Ping pong balls: need to find near seamless ones. A lot of ping pong balls have a thin seam around the circumference of the balls, where the two halves meet, which could effect propulsion out of the cannon if the seam rides along the inside of the barrel.

Tennis balls: the "fur" on the outside could act as batting create an airtight seal within the cannon. But, the "fur" could also create drag as it's exiting the cannon.

Perhaps creating a projectile would be best?

Oh, didn't know that.

All the better.

bio

MB have tested ice bullets twice, and on both occasions the bullet was steam by the time it reached the muzzle. No reason MB couldn't make ice-shot, but I don't think anyone would be all that surprised by the results and they may be of the opinion that such a thing is a case of 'been there, done that'.