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The clam-like structure of Beagle 2 not only has to support all the elements required to carry out the scientific mission on the surface of Mars but must also ensure they survive the final impact of landing. When Beagle 2 drops onto Mars out of its cocoon of gas-filled bags, the impact could be in any orientation with a contact area varying from a small, sharp rock to a large, flat surface. The design case is equivalent to pushing your PC off a chair (on Earth) onto a concrete floor and expecting it still to work. Unfortunately Beagle 2 does not have the full choice of materials available to your PC manufacturer because we have to be as light as possible to maximise the payload inside the lander and we have to keep the systems warm through the martian night when temperatures down to -70°C will be reached.
The solution chosen is to use an outer shell that provides energy absorption and also thermal insulation within a casing that must spread the impact loads and resist tearing. An inner shell comprising carbon-fibre skins on an aluminium honeycomb core makes up the primary structure. All materials have to be compatible with more than the usual space environment (vacuum and radiation exposure, low outgassing, low mass overall, low cost) in that they have to face the sterilisation process necessary for planetary protection requirements.
The two halves of the lander, lid and base are joined by
a cable driven hinge which irrespective of the orientation
which Beagle 2 finds itself on Mars will open the clam in
its correct position.
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