A friend posted a link to this on a message board; where pretty much everyone is accepting its veracity. I can see the sawdust adding strength to the end product, but my instincts. as far as the sawdust preventing heat gain to a degree that it allows ships made with this stuff to last more then hours in the more northern or southern bodies of water. tell me its BS.
So, are the anti-melting capabilities of this stuff for real? I tried Snopes but no luck there, but then I’ve been known not to be overly skilled with the search engine.
Do a search. There was a pykrete thread about a year ago. (I remember one of the links in that thread mentioned how FDR got the surprise demonstration of the stuff. Your link says Churchill. Maybe it talked about FDR later, but I stopped reading. Gotta go.)
Presumably this is the MetaFilter thread on pykrete? A Google search on pykrete finds various accounts confirming this slow-melting property and the history of the prototype on Lake Patricia. The deal, apparently, is that when the outer layer thaws, the wood-pulp remains to insulate the frozen core.
It’s for real. There are a number of books and articles covering Pyke and his often strange role in scientific developments during WW2, and Pykrete, along with his proposal for building a massive aircraft carrier from the stuff, is one of the best-known of these. There was serious consideration given to the proposal, but in the end the practical difficulties of the project were too great.
Eccentric Lives And Peculiar Notions- Has a section on Pyke. He comes across as the typical absent minded proffesor. Though, his inventions do seem sound. Besides the chemical compostion, and engineered to keep cold, the ships would also have contained tubes for circulating coolant through the hull and walls.
I’m surprised that Pykrete has never found an application.
The problem with Pykrete is in how to make it. You can’t just mix water with sawdust and freeze. The stuff’s too insulating. It’s like styrofoam made of ice.
Pyke’s invention wasn’t just Pykrete, instead it was a concept: fill ice with air so it becomes a thermal insulator, but then CREATE the stuff by supercooling water inside a nozzle and then spray it onto a form. The water would be far below 0C, so it would freeze in moments, locking in the air in the sawdust. But then once hardened, it takes forever to get the heat into the stuff in order to melt it.
Also, adding sawdust to increase the hardness is a well known technique. Anything that halts the propagation of cracks in solid materials will make the material tougher. “Composite materials” such as polyester with embedded glass fibers is going to be far harder to shatter than just a block of pure glass or just a block of pure polyester plastic.
From reading metafilter: solidly packed snow takes forever to melt. THAT’S IT!!!
Remember, you can’t make “frozen styrofoam-ice” by sticking it in the freezer. The outer layers insulate the still-warm interior.
But you CAN make the stuff by taking some snow and hammering it down into a compressed block. Snow is full of air, so the resulting solid would be part air, part ice.
This means that it’s probably easy to make your own Pykrete by mixing wood-flour with snow and then pounding it with a hammer. Use a pipe and a hunk of aluminum as a cylinder and piston to make Pykrete blocks. No special cryo-equipped supercooling nozzles!
I was always put off by the need for liquid nitrogen, pumps, machine shop work, etc. Now I have something simple to try.
I imagine the sheer mass of the structures he’s talking about would make a big difference as well. For instance, the heat from the solidification of concrete in the hoover dam has still not escaped - the dam will not reach ambient temperature levels for another 100 years or so. The reason is that A) concrete is a decent insulator, and B) the thermal mass is gigantic.
So, if you make a huge floating barge out of a few thousand tons of pykrete, it’s going to stay cold on the inside for a long, long time.
Did the outer surface of pykrete forms start to get soft after a while? Would a Pykrete ship start to look all pock-marked as it aged?
The practical difficulties of devising a fuel efficient method for moving such an enormous mass are probably also a consideration, in that a pykrete ship is going to need to be much more massive than a steel ship of comparable capacity.
Also, IIRC, the story on Pyke in “Eccentric Lives” said that nuclear weapons reduced the strategic benefit of such monster ships: nuke one, and it’s a floating mass of fallout.
Couldn’t you use Pykrete to construct a perminant floating island though? Is seems like you could use the ocean as a heat sink for a heat pump to cool fluid for the cooling tubes mentioned earlier. Then you would just have to generate enough power to run the heat pump.
Such a structure could be huge, large enough to float a small city and more or less perminant.