In that book, the interstellar starship Magellan can reach a large fraction of lightspeed, thanks to its "quantum drive," but, at those speeds, interstellar gas and dust becomes a real problem that could damage the ship. The ship, therefore, has an ablative shield on its nose, made of ice. (This shield has to be replaced, which is why the Magellan stops off at the mostly-water world Thalassa en route to its final destination.) The shield is built of giant hexagonal tiles of ice, which contain seaweed as a strengthener; the resulting mixture is dubbed "icecrete" by some of the engineers. Clarke may have been alluding to pykrete here; I assume he'd have known about it.
Basically, their snow is dirty enough that there's still a 12 foot pile of the stuff.
Sorry for the tangent, but posting to HN seems a rather passive-aggressive way to show someone something. The submitter could have just linked it to the discussion they were having. Instead it's like OP is desperate for attention.
Or at least that's how it works on Imgur.
1. In that HN thread,
2. As its own item on HN, and
3. With a link between the two.
Your "passive-aggressive" and "desperate for attention" comments are out of line. There are more than a few differences between HN and Imgur.
OP posted what they thought was an interesting link. Enough other people agreed to vote it onto the front page. Nothing nefarious going on.
I did find it interesting though.
With concrete canoes, wonder if they ever experimented with Roman seawater concrete, which generates heat when it reacts with water. Heated hulls supposedly exhibit less friction which may give a slight edge in a race.
A heated hull riding on a bed of steam sounds like an interesting [and very high energy cost] engineering challenge though!
*http://www.bloomberg.com/bw/articles/2013-06-14/ancient-roma... ... reaction reportedly reaches temperature approaching 900C.
Pykrete, however, appears to be repairable with seawater, a refrigeration unit, and a hose.
"Next, he fired at the pykrete to give an idea of the resistance of that kind of ice to projectiles. The bullet ricocheted off the block, grazing the trouser leg of Admiral Ernest King and ending up in the wall."