2019/9b.plaintext

   1 memo from docking manoeuvre office to as test flight space systems re as docking collar tests
   2 preliminary testing of the docking collar system has revealed a potentially serious flaw in the
   3 design which must be addressed before the system can be certified the issue concerns the emergency
   4 release system background the docking system performs the following functions impact energy
   5 absorption mechanical connection spacecraft alignment and retraction spacecraft hard mechanical
   6 connection and docking interface sealing spacecraft undocking and separation in order to achieve
   7 these functions the docking system consists of three principle parts the base a structural ring and
   8 the latching ring the docking system base is the main structural member to which the docking system
   9 assemblies are attached the structural ring carries the body latches which provide a hard pressure
  10 tight connection between the two spacecraft together with the capture latches which operate during
  11 the docking manoeuvre these perform the docking function they consist of eight active and eight
  12 passive hooks with an electrical drive installed on one of the latches and closed loop cables
  13 connecting them each active hook has a cam operated mechanism which performs its opening and
  14 tightening corresponding hooks of the passive docking system are captured by active hooks each
  15 passive hook has a stack of preloaded bellville springs providing a definite force for the docking
  16 interface preloading the docking interface seal will provide pressure integrity of the docking
  17 interfaces this consists of two concentric rubber ring seals on each system and a manhole cover is
  18 used to close the transfer tunnel of the spacecraft hatch locking and unlocking is manually
  19 performed by the crew it is sealed by a mechanism which has a further eight eccentric latches these
  20 being connected with each other by means of closed cable connection the docking system is equipped
  21 with alarm and meter system which provide telemetry to the ships and to ground control in standard
  22 operational mode undocking is performed by release of the active spacecraft capture latches and then
  23 by opening the structure latch hooks if necessary undocking can be performed by the passive
  24 spacecraft by releasing the body mounted latches and opening the structure latch passive hooks
  25 spacecraft separation is performed by spring thrusters symmetrically located on the structural rings
  26 of both systems after the latches release the principle difference between the russian and us
  27 docking system designs can be seen in the guide ring system unlike the russian electromechanical
  28 docking system apollo is equipped with an electric drive which uses cable connections to trigger the
  29 latches another essential difference is the russian emergency release system ers a backup provided
  30 by pyro bolts attached to each passive and active hook which operates in passive mode and provides
  31 practically instantaneous undocking in the event of a system malfunction or accident onboard one or
  32 both of the docked spacecraft situations in which the ers might be initiated include i uncontrolled
  33 fire or explosion onboard one of the spacecraft during docked operations ii failure of the docking
  34 control system preventing standard release operation iii attitude control failure of or unplanned
  35 firing on one or both spacecraft imposing high stresses on the docking mechanism while the ers
  36 provides an effective backup for emergency situations simulations and tests on the huntsville
  37 docking testbed show that the effectiveness of the pyrotechnic bolts is a critical issue too much
  38 explosive could cause critical damage to the pressure seals around the hatch while too little can
  39 leave the spacecraft attached with a damaged mechanism the ers was designed for operation on ussr
  40 missions and is therefore tuned to the structural constraints on the soviet platform since the
  41 latches are electromagnetic on that spacecraft they are less prone to damage under vibrational
  42 forces the motor and cable mechanism used on the apollo platform is more vulnerable to shock and
  43 under certain test conditions has been shown to fail following the triggering of the erson the
  44 soviet end of the docking mechanism shockwaves will not of course propagate through the vacuum of
  45 space but the forces can be transmitted through the tunnel to the apollo latches and if the bolts
  46 fire asymmetrically this places a torsion loading on the mechanism which can unseat the drive cables
  47 in five of the seven tests where this phenomenon was observed the engineers were able to reseat the
  48 cables by repeatedly operating the mechanism but in the remaining two cases the mechanism was beyond
  49 repair without manual intervention unfortunately in these two cases the safety interlock also
  50 prevented the hatch from being opened which could make it difficult for the astronauts to carryout a
  51 spacewalk to execute the required repair in this case it would normally be possible for the
  52 astronauts to manually operate the manhole latches by disassembling and subsequently assembling the
  53 hatch cover however if the latching mechanisms have been sufficiently damaged by the pyro bolts this
  54 might prove a risky option and it is even possible that the cover latches would fail to retract
  55 manually we have asked queens team to take a look at this and she assures me that they can sort it
  56 out she has worked on most of the apollo mission design teams so i am pretty confident that she can
  57 make sure everything is ok for this one