From: yee@atlas.arc.nasa.gov (Peter Yee)
Subject: Countdown for STS-54 launch of Endeavour begins Sunday, Jan. 10 [Release 1-93/KSC] (Forwarded)
Apparently-To: sci-space-news@ames.arc.nasa.gov
Followup-To: sci.space
Originator: yee@atlas.arc.nasa.gov
Reply-To: yee@atlas.arc.nasa.gov (Peter Yee)
Organization: NASA Ames Research Center, Moffett Field, CA
Date: Thu, 7 Jan 1993 23:05:51 GMT

          George H. Diller                               January 8, 1993
          Kennedy Space Center
          407/867-2468


          KSC Release No. 01-93


          COUNTDOWN FOR STS-54 LAUNCH OF ENDEAVOUR BEGINS SUNDAY, JAN. 10


               The countdown clock for  the  STS-54  flight  of  the  Space
          Shuttle  Endeavour is scheduled to begin at 1 p.m.  (EST) Sunday,
          Jan.  10 at the T-43 hour mark.  The countdown includes 24  hours
          and 32 minutes of built-in hold time leading up to the opening of
          the launch window at 8:52 a.m. (EST) on Wednesday, Jan. 13.

               At  the  start  of the countdown,  the launch team in firing
          room 3 of the Launch Control Center verifies the Shuttle  vehicle
          is  powered  up  and  that  the data processing system and backup
          flight control system are operating.  Flight software  stored  in
          the  orbiter's twin memory banks will be reviewed,  computer con-
          trolled display systems will be activated,  and the backup flight
          system general purpose computer will be loaded.

               Preparations  also  start  at  the  liquid oxygen and liquid
          hydrogen storage farms for loading the external tank  with  super
          cold,  or  cryogenic,  propellants.  Orbiter  navigation aids are
          turned on and tested and the inertial measurement units  are  ac-
          tivated.

               In parallel with these activities,  the launch team prepares
          for loading Endeavour's onboard fuel cell storage tanks with liq-
          uid oxygen and liquid hydrogen reactants.  Also performed at  the
          start  of the countdown is the final stowage,  microbial sampling
          and water level adjustment of the crew waste management system.

               At T-27 hours,  the countdown will enter its first  built-in
          hold.    This is a 4-hour hold which extends from 5 to 9 a.m.  on
          Monday,  January 11.  When the countdown resumes,  the launch pad
          will  be  cleared of all personnel in preparation for loading the
          fuel cell storage tanks.

               Servicing of the liquid oxygen and liquid hydrogen fuel cell
          supply tanks is scheduled to start at the T-25 hour mark. Servic-
          ing activities take approximately five hours.

               When servicing of the fuel cell tanks  has  been  completed,
          the pad will be reopened for normal work,  and the countdown will
          enter the second planned hold.  During this four-hour hold at the
          T-19 hour mark,  the orbiter mid-body umbilical unit used to load
          the super cold fuel cell  reactants  into  the  orbiter  will  be
          demated.  This hold will extend from 5 to 9 p.m. on Monday.

               When the countdown resumes,  technicians will complete final
          vehicle and facility closeouts and begin activating the orbiter's
          communications systems and configuring  Endeavour's  cockpit  for
          flight.  The  main propulsion system and shuttle main engines are
          prepared for cryogenic loading.

               The orbiter's flight control system navigation aids and com-
          munications systems will be activated,  and switches in the cock-
          pit  will  be  configured  for loading of the external tank.  The
          stowable mission specialist seats will be installed in the flight
          and mid-decks.

               The countdown will enter the  next  built-in  hold  at  T-11
          hours  at  5  a.m.  on Tuesday.   During the hold,  time critical
          equipment will be installed in the orbiter's cockpit and the  in-
          ertial  measurement  units  will  be activated and warmed up.  At
          about 11 a.m.,  the rotating service structure will be moved away
          from the vehicle to the launch position.   This hold is scheduled
          to last 13 hours, 32 minutes, or until 6:32 p.m. on Tuesday.

               At T-9 hours, the onboard fuel cells will be activated,  and
          the  launch  team  will begin evacuating the blast danger area at
          T-8 hours,  or about 9:32 p.m.  Tuesday.  The final items  to  be
          placed  in  the crew module are now stowed aboard,  and the joint
          heaters on the solid rocket boosters are also turned on  at  this
          time.  At T-7 hours,  30 minutes, conditioned air that is flowing
          through the  orbiter's  payload  bay  and  other  areas  will  be
          switched  to  gaseous nitrogen in preparation for loading the ex-
          ternal tank with  super-cold  liquid  propellants.  The  inertial
          measurement  units  will transition from the warm up stage to the
          operate/attitude determination mode at T-6 hours and 45  minutes.
          At  T-6  hours a steering check of the orbital maneuvering system
          engines will be performed.

               The countdown will enter another planned  built-in  hold  at
          the  T-6  hour mark at approximately 11:32 p.m.  Tuesday.  During
          this one-hour hold,  final preparations for loading the  external
          tank will be completed and a pre-tanking weather briefing will be
          conducted.

               Chilldown  of the lines that carry the cryogenic propellants
          to the external tank will begin at  the  T-6  hour  and  counting
          mark,  at 12:32 a.m. Wednesday. Filling and topping of the exter-
          nal tank should be complete at the beginning of the planned  hold
          at T-3 hours which will start at 3:32 a.m. Wednesday.

               This  hold is two hours in duration.  During this time,  the
          ice inspection team will perform a survey of the tank's outer in-
          sulation,  and the closeout crew will begin configuring the  crew
          module  and  white  room  for the flight crew's arrival.   Liquid
          oxygen and liquid hydrogen will be in  a  stable  replenish  mode
          during this time to replace the propellant that "boils" off.

               The  astronauts  are  scheduled  to be awakened at 3:57 a.m.
          Wednesday and have breakfast.  Their breakfast  is  scheduled  at
          4:27 a.m.

               After eating, the crew will receive a briefing on world-wide
          weather conditions via satellite from Mission Control in Houston.

               The  flight  crew  will  suit  up  in their partial pressure
          suits,  then leave the Operations and Checkout Building at  about
          5:37 a.m.,  at T-3 hours.  They will arrive at the pad white room
          at about 6:07 a.m. where they will be assisted by white room per-
          sonnel in getting into the crew cabin.

               Just prior to the T-1 hour  mark,  the  test  team  and  the
          flight  crew will get another weather update,  including observa-
          tions from an astronaut flying in a Shuttle Training Aircraft  in
          the KSC area.

               The last two built-in holds will be 10 minutes in duration
          and will occur at the T-20 minute mark or at 8:12 a.m. and at the
          T-9 minute mark or at 8:33 a.m. During the final hold, the flight
          crew  and  ground team receive the NASA Launch Director's and the
          Mission Management Team's final "go" for launch.

               Milestones after the T-9 minute mark include  start  of  the
          ground launch sequencer;  retraction of the orbiter access arm at
          T-7 minutes,  30 seconds;  start of the orbiter's auxiliary power
          units at T-5 minutes; pressurization of the liquid oxygen tank at
          T-2  minutes,  55 seconds;  pressurization of the liquid hydrogen
          tank at T-1 minute,  57  seconds;  and  the  electronic  "go"  to
          Endeavour's   onboard  computers  to  start  their  own  terminal
          countdown sequence at T-31 seconds.  The orbiter's three main en-
          gines will start at T-6.6 seconds.


                                COUNTDOWN MILESTONES

                        Launch - 3 Days (Sunday, January 10)

               Perform the call-to-stations at T-43 hours.  Begin check out
          of the backup flight system and review flight software stored  in
          mass memory units and display systems.  Astronauts arrive.

               Load  backup flight system software into the orbiter's fifth
          general purpose computer.

               Begin  stowage  of  flight  crew  equipment.   Inspect   the
          orbiter's  mid and flight decks and remove crew module platforms.
          Start external tank loading preparations.


                        Launch - 2 Days (Monday, January 11)

               Enter first planned built-in hold at T-27 hours for a  dura-
          tion of 4 hours. Activate orbiter's navigation system.

               Resume countdown. Start preparations for servicing fuel cell
          storage  tanks and begin final vehicle and facility closeouts for
          launch.

               Clear launch pad of all personnel and load liquid oxygen and
          liquid hydrogen reactants into the orbiter's  fuel  cell  storage
          tanks.

               Enter  second  planned  built-in hold at T-19 hours for four
          hours.

                 After the loading operation, the pad will be reopened for
          normal work and orbiter and ground  support  equipment  closeouts
          will resume.

                Demate  orbiter  mid-body  umbilical  unit used during fuel
          cell loading. Resume countdown.   Activate orbiter communications
          systems  and  prepare Shuttle main engines for propellant tanking
          and flight.


                        Launch - 1 Day (Tuesday, January 12)

                Install mission specialist seats in crew  cabin.  The  tail
          service  masts on the mobile launcher platform will be closed out
          for launch.

               Enter planned hold at T-11 hours (5 a.m.) for a duration  of
          13 hours and 32 minutes.


               During  this hold,  the orbiter's inertial measurement units
          will be activated and kept in the "warm up" mode and film will be
          installed in the numerous cameras on the launch pad. In addition,
          safety personnel will conduct a debris walkdown and the pad sound
          suppression system water tank will be filled.

               The rotating service structure will be  moved  to  the  park
          position  during  this  hold  at  11 a.m.  Perform orbiter ascent
          switch list in crew cabin.

                Resume countdown at 6:32 p.m. Install time critical flight
          crew equipment and perform the  pre-ingress  switch  list.  Start
          fuel cell flow-through purge.

               Activate  orbiter  fuel  cells.  Configure communications at
          Mission Control in Houston for launch.  Clear  the  blast  danger
          area  of all non-essential personnel and switch orbiter purge air
          to gaseous nitrogen.

               Enter one-hour planned built-in hold  at  T-6  hours  (11:32
          p.m.).


                         Launch Day (Wednesday, January 13)

               Resume countdown.   Launch team verifies there are no viola-
          tions of launch commit criteria prior to cryogenic loading of the
          external tank.   Start loading the external tank  with  cryogenic
          propellants.

               Complete  filling  the external tank with its flight load of
          liquid hydrogen and liquid oxygen propellants.  Perform open loop
          test with range safety and conduct gimbal profile checks of orbi-
          tal maneuvering system engines.

               Perform  inertial measurement unit preflight calibration and
          align Merritt Island Launch Area (MILA) tracking antennas.


               Enter two hour hold at T-3 hours. Closeout crew and ice  in-
          spection team proceeds to launch pad.

               Resume  countdown at T-3 hours (5:32 a.m.) Complete closeout
          preparations in the white room and cockpit switch configurations.
          Crew departs astronaut quarters at Operations and Checkout Build-
          ing for the pad.

               Flight crew enters orbiter. Astronauts perform air-to-ground
          voice checks with Mission Control in Houston.  Close orbiter crew
          hatch.  Begin range safety final network open loop command check,
          perform hatch seal and cabin  leak  checks,  begin  the  inertial
          measurement unit preflight alignment and range safety closed loop
          test. The white room is closed out and the closeout crew moves to
          fallback area. Primary ascent guidance data is transferred to the
          backup flight system.

               Enter planned 10-minute hold at T-20 minutes.

               Resume  countdown.  Transition  orbiter onboard computers to
          launch configuration and start fuel  cell  thermal  conditioning.
          Close orbiter cabin vent valves. Backup flight system transitions
          to launch configuration.


               Enter planned 10 minute hold at T-9 minutes.


               Resume countdown.



          Start automatic ground launch sequencer (T-9 minutes).
          Retract orbiter crew access arm (T-7:30).
          Start mission recorders (T-5:30).
          Start APU's. Arm SRB and ET range safety safe/arm devices (T-5).
          Start liquid oxygen drainback (T-4:55).
          Start orbiter aerosurface profile test (T-3:55).
          Orbiter transfers to internal power (T-3:30).
          Start MPS gimbal profile test (T-3:30).
          Pressurize liquid oxygen (LO2) tank (T-2:55)
          Retract gaseous oxygen vent arm (T-2:55).
          Fuel cells to internal reactants (T-2:35).
          Pressurize liquid hydrogen (LH2) tank (T-1:57).
          Deactivate SRB joint heaters (T-1:00).
          LPS go for start of orbiter automatic sequence (T-0:31 seconds).
          Start SRB gimbal profile test (T-0:6.6).
          SRB ignition and liftoff (T-0).
Newsgroups: sci.space.news