Webb: Using Sci-fi to build a better Hubble
Few could argue that Hubble is the ‘daddy’ of all space telescopes. In its twenty years of operation, it has pushed back the boundaries of astronomy and physics, sent back images that have captured the imagination of an entire planet and provided PC screen savers to a generation. But all good things come to an end and, although more powerful than ever, Hubble’s days are numbered and its successor is waiting in the wings.
Set for launch in three years, the James Webb Space Telescope will allow science to peer-deeper into space and look further back in time than ever before. Whereas Hubble looked like a telescope that found its way into space, Webb is a very different beast. Resembling more of an interstellar sailing ship than a telescope, Webb’s colossal light-collecting mirrors sit atop a Sun-shield the size of a tennis court and, once unfolded to their full 6.5m spread, the array of hexagonal mirrors will dwarf Hubble’s single 2.4m mirror.
Nor will Webb have access to the home comforts that Hubble has been enjoying in its Earth-hugging 570km-high orbit. Positioned some 1.5million km from Earth, not only will Webb be well beyond the sort of help saw Hubble, first fixed of a faulty mirror, then repeatedly upgraded, repaired and serviced, but, should anything go wrong craft, it will be well beyond any sort of help at all.
Webb’s extreme location raises other problems that have to be tackled by Nasa with some pretty extreme engineering solutions. At this distance from Earth, temperatures are lower than those at Pluto, substances that are gases on Earth are liquids and rubber behaves like glass. So Nasa has had a dig around the kit bag of science fiction to find a solution. The craft’s chassis – the metal frame to which all its components and experiments are attached – has been made of a material you might recognise from James Cameron’s blue-tinted fantasy, Avatar: ‘Unobtainium’.
‘Unobtainium’ is actually the name given to a material needed to fulfil a design that is too rare, too costly, or too impossible to build. The Nasa team needed a material that could withstand the super-cold temperatures (as low as -246°C) without expanding or contracting so much as fraction of a millimetre. Even such a tiny change in the chassis’ shape would throw all of the telescope’s experiments out of alignment.
In this case, the ‘Unobtainium’ is a carbon fiber/cyanate-ester resin system bonded together with combination of nickel-iron alloy fittings… let’s just stick with ‘Unobtainium’ shall we?
Anyway, the exotic chassis has just passed rigorous testing meaning that the James Webb Space Telescope is that little bit closer to following in Hubble’s mighty footsteps.