Question

Could plastics be used for the exterior of spacecraft? What are polymer molecules like and what type of intermolecular force(s) hold them in the solid state? When high energy U.V. photons hit polymer chains what might happen (as opposed to shining on a metal)??

Answer 1

Most of spacecraft earlier use light weight alloys of titanium, aluminium and magnesium but combination of plastic and various hybrid material such as metal matrix which reduce weight of space craft can be used. Carbon fiber technology has replace spacecraft component, except for outer spacecraft bulkhead.

Plastic offer a number of advantages over metal and ceramics:

• Low specific gravity of plastic
• Some plastic are extremely tough which allow them to withstand impact without failure.
• Compared to metal, plastic is 50% better at shielding solar flares, 15% better for cosmic rays.

Fibre-reinforced polymer or fibre reinforced plastic are used in space craft. It is a composite material made of polymer matrix reinforced with fibres. The fibres are usually glass, carbon, or aramid, although other fibres such as paper or wood or asbestos have been sometimes used. The polymer is usually an epoxy, vinylester or polyester thermosetting plastic, and phenol formaldehyde resins. Vander waal forces hold them together in the solid state.

There is quite large gap between HOMO and LUMO in case of polymer. High energy is needed to overcome this gap. In case of metal, this gap is quite less.Less energy is needed to overcome this gap. they easily move to excited state when a photon hits the metal surface.