  Experiments in long distance quantum key distribution have motivated the
development of ruggedised single photon sources, capable of producing useful
correlations even when removed from the warm, nurturing environment found in
most optics laboratories. As part of an ongoing pro- gramme to place such
devices into low earth orbit (LEO), we have developed and built a number of
rugged single photon sources based on spontaneous parametric downconversion. In
order to evalu- ate device reliability, we have subjected our design to various
thermal, mechanical and atmospheric stresses. Our results show that while such
a device may tolerate launch into orbit, operation in orbit and casual
mishandling by graduate students, it is probably unable to survive the forcible
disassembly of a launch vehicle at the top of a ball of rapidly expanding and
oxidising kerosene and liquid oxygen.
