466 The connectors of each pass through plug were embedded in a two- part shell capable of accommodating  the compliance necessary to ensure alignment of the assembly , such that the plug was fully seated and the  shell adequately aligned, in order  to seal in the ejection gas generated by the pyrotechnic charge. This plug  and jack pair constituted the demating interface for the ejection function of the connectors. Oversized holes  in the piston and piston seal accommodated alignment compliance between the installed pass through plug  assembly and piston assembly. A layer of compliant seal material (rubber sheet) , sandwiched between the  upper surface of the piston and the lower end of the payload,  provided a seal against leakage of the  expansion gas without requiring a tight fit between the pass through plugs and associated holes in the  piston and piston seals. Phono plug assemblies (the “floating plug”) installed in the dispenser breech plate,   in place of the squib electrical interface pins , constituted the mating interface for the magazine installation  function of the connectors ( Figure 16). Within the  dispenser, a compression spring at each connection  provided enough force to guarantee full insertion of the connections once the payloads were fully seated,  and allowed for flexure of the connectors to accommodate any misalignment ( Figure 17).  

Figure 17. Dispenser to payload pass through plug interface.  

The original intent was to limit the payload installation into the vehicle to a single cycle, but unanticipated  challenges with the software of the data recording and payload beacon activation forced an  extended test  campaign with numerous installation and removal cycles. The environmental test plan of vibration, thermal,  and ejection test s also required a larger number of payload installation and removal cycles than originally  envisioned. The repeatable  and simple nature of this connector concept proved both vital to testing, but  also problematic. The inherent nature of the coaxial plugs caused a variety of adverse connector pin  shorting conditions during insertion and removal that required development of detailed and rigorous  operational procedures to avoid damage to the payloads.  

Although initial data integrity testing appeared successful at the component level, early development tests  of data writing during vibration encountered anomalies with data integrity. Initial diagnostic efforts focused  on the apparent association with the vibration environment, but further testing revealed that intermittent  data writing failures exist ed when using the fully integrated system configuration in any environment. Si gnal  diagnostic testing uncovered that although data had been successfully transmitted and the combined  connection had excellent conductivity on all lines, when operating at the high frequency and low signal  strength of the USB 2.0 standard, the fully assembled data connection had a net impedance sufficient to  cause intermittent failure of the data signal. Upon comparison of the coaxial phono plug connector with  traditional USB connectors that have individual, parallel  signal paths, it was realized that the closely spaced  concentric geometry of the coaxial contacts in the phono plug created a capacitance between adjacent