In-bore measurements using an optical data link

Previous efforts to obtain information from onboard sensors involved writin g the data to an EPROM located in the launch package, performing a "soft" c atch of the projectile, and recovering the chip in order to download the da ta. This method requires soft catch capability and has been limited to velo cities of less than 1 km/s, We have developed a method to measure in-bore q uantities on board a railgun launch package and transmit the information ou t of the barrel in real time using an optical data link The onboard transmi tter, which is mounted on the front end of the launch package, is either a repackaged laser diode or a high intensity LED, During launch, light pulses are transmitted down the bore, reflected off a mirror just outside the muz zle, and received with a telescope and attached photomultiplier tube. Succe ssful operation has been achieved for accelerations up to 105 kgees and vel ocities up to 2.0 km/s. An analog encoded version of the system has been bu ilt and used to perform an armature voltage measurement.