• Question: what is the toughest element and how fast can it move in the earths atmosphere before disintergrating or breaking up?

    Asked by mattheworgan to Arttu, Ceri, James_M, Monica, Philip on 13 Jun 2011.
    • Photo: James M Monk

      James M Monk answered on 13 Jun 2011:

      I would have to say carbon is the strongest, which is very strong indeed when it is in the form of a diamond (or even stronger when in some more exotic states like graphene). It wouldn’t be a very good material for travelling at very high speeds though because it can burn in oxygen quite well I believe (I have never seen a diamond burnt though).

      Tungsten may be a good choice for heat resistance. It is quite a dense material, and is what filament lightbulbs (that glow white hot) used to be made out of. Tungsten is too heavy to make an aeroplane or space craft from, however.

    • Photo: Philip Dolan

      Philip Dolan answered on 13 Jun 2011:

      As James said carbon, as diamond, is mechanically the toughest element. It is said to sublime at temperatures in excess of 3500 celcius. For comparison a space shuttle’s heat shield is good up to 1200 celcius and that copes with re-entry, which is about as quick as we can get anything to go in our atmosphere (jet fighters go up to Mach 3 or 4, the shuttle re-enters at Mach 25, or 18000 mph).

      It’s probably worth mentioning (before you guys go out and make a space shuttle with a diamond coated hull) that diamond is also by far the most thermally conducting element. This means that although it won’t melt, any metal that the rest of the shuttle is made of will be heated up too, and melt pretty quick. The heat shields that the shuttle uses are insulators, so they don’t transfer the heat to the rest of the hull.

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