“Roger, IOS.”
“Your OMS-2 will be as planned at MET 00:40:51. At OMS shutdown, you’ll be twenty-three miles behind target and closing at an R-dot of 178 feet per second. We’ll lose you about one minute into the burn… Your temps are coming down nicely in the dark. You may inhibit Loop One and go to Loop Two on the freon for the night pass. LOS this station at forty-two minutes out, with AOS Australia at fifty-one minutes. As soon as you null the residuals after the OMS burn, we want you to roll upright to align the platforms with star trackers and COAS.”
“Okay, Flight. Yawing about now.”
The computers on command from the AC brought Shuttle’s tail around until the ship was flying upside down and nose first.
“Got you in Y-POP now, heads down in OMS-2 attitude, Endeavor. We’re watching your downlink. OI playback looks a bit noisy.”
“Understand. Operational instrumentation data dump noisy,” Enright replied. “Want us to switch quads?”
“Negative, Jack. Leave the antennas as they are. We may have you change signal processors later for the phase-modulated downlink. Backroom thinks you’re just breaking up a bit over the mountains. Should clear up when you’re over water momentarily.”
“ ’Kay.” Enright brought the second OMS firing numbers up on the right and center televisions called CRTs for cathode ray tubes. The center screen showed the OMS-2 checklists. “CRTs on-line with OPS-2 and Major Mode 205 running.”
“Copy, Jack. Operational Sequence Two. We’ll leave you alone with your burn prep. Configure data dump to high bit rate, please.”
“You’re looking at it, Flight.”
“Data real clean now, Jack. Thanks.”
As Endeavor coasted southeast over the nighttime shoreline of East Africa, the two fliers readied each of the two OMS pods in Shuttle’s tail for the upcoming rocket burn. The firing of the two engines for a minute and a half would change Shuttle’s lopsided orbit, 132 by 57 nautical miles, to a near circular orbit of 130 nautical miles all around, synchronized with LACE ahead.
The crewmen directed their attention in the cabin’s floodlights to Overhead Panel-Eight located on the flightdeck ceiling above Enright’s left shoulder. The AC read the preburn checklist printed on the center CRT as Enright touched each switch.
“Helium pressure, Loop A, left and right, talk-back open; Loop B, left and right, to GPC; propellant tank isolation, Loop A, left and right, talk-back open; Loop B, left and right, to GPC; left and right crossfeeds, Loops A and B, to GPC; engine valves, left and right, on, at Panels Overhead-14 and -16. And, engine arm, left and right, Panel Center-Three, lever-locked arm.”
“OMS ready, Will.”
“Okay, Flight. We’re cranked up and ready for OMS-2 in two minutes on my mark… MARK! Two minutes. We’re in inertial attitude mode with attitude deadband of 3 point 5 degrees, rate deadband of three-tenths degree per second, and discrete rate at two-tenths degree per second. DAP in automatic.”
“Copy, Endeavor. We’ll have a work-around for the RGA failure this afternoon. Expect sunrise over Samoa at seventy-four minutes MET. We remind you to keep a close watch on coolant loops when you hit daylight. We see you flying flight control channel Two.”
“Roger, Indian Ocean. Running FC channel Two. I have the con with CSS fly-by-wire in attitude hold in Roll-Yaw. Mother is steering the alpha angle and OMS TVC.”
“Copy, Will, as to control stick steering and GPC thrust vector control. You’re fifteen seconds to OMS ignition, 1 minute 12 seconds to loss of signal… 5, 4, 3, 2, 1…”
“Auto ignition, Flight! Fire in the hole, left and right. Good solid thump from the OMS.” The AC carefully studied the “eight ball,” the round attitude indicator above his knees in the center of the forward instrument panel at his station. He watched three orange course-deviation needles to make certain that Mother held her ground without wobbling during the OMS firing.
Although the slight acceleration of the OMS-1 burn 20 minutes earlier was barely perceptible after the 3-G load of launch, both pilots could feel their backs solidly contact their flight seats during this OMS burn. Their bodies were already oversensitive to gravity after a quarter hour of weightlessness.
“Go at thirty seconds into the burn, Flight.” Enright called. “Feels like we’re going flat out to Australia!”
“Roger, Endeavor. Pressures and chamber temps are all green. LOS in thirty seconds. Hang on, Jack.”
Far behind them, the two OMS engines, each 45 inches wide at their nozzles, burned furiously. Each engine’s nozzle swiveled slightly through seven degrees of freedom to steer the ship as the OMS rockets pushed Shuttle higher.
“Good burn at forty-five seconds, Flight. Mixture ratio at 1 point 65 left, and 1 point 63 right. Chamber pressure 124 left and 127 right. Fuel flow is 4 point 13 pounds per foot of Delta-V.”
“Copy, Endeavor. Losing you now. Configure LOS, see you over…”
“And it’s on to kangaroo land,” Enright said as the Indian Ocean tracking ship went over the Earth’s far western edge as Shuttle sped eastward at 5 miles per second.
“360 psi in the GN2 accumulators. And GN2 tanks at 2,400 psi. Sixty feet per second to go,” the AC called. In the cozy flightdeck, there was no sound nor vibration from the OMS engines. Only the cabin fans broke the stillness.
“Shutdown!” both fliers called as Mother automatically stopped each OMS engine when she felt that the proper speed had been reached. “Auto trim,” Parker called as Endeavor’s RCS jets in her nose and tail popped loudly to clean up the OMS burn’s residual guidance errors. Outside their windows, the loud 870-pound jets in Endeavor’s nose RCS unit lit the night with 30-foot plumes of yellow flame.
“Good burn. Residuals nulled,” Enright said over the intercom. “Major Mode 106 now running. Going to 10 degrees attitude deadband. DAP logic select to Mode A, and RCS to normal.”
Immediately, the command pilot punched the CSS/PITCH and the CSS/ROLL-YAW, lit pushbuttons on the panel glareshield in front of his face. With full manual control of his ship, the AC moved the control stick between his knees. As he commanded the RCS thrusters to roll Shuttle rightside up, the computers chose the best thruster combination to accomplish the wing-over. Neither pilot knew which of the thirty-eight primary RCS thrusters were selected for firing by Mother. All that mattered was Endeavor’s slow three-degrees-per-second roll which stopped after one minute with Shuttle coasting right-side up.
“Now we’re flyin’ right!” Enright smiled as he flew in space heads-up for the first time. He had utterly no sense of speed or of up and down.
Outside, the windows were full of black sky with the nighttime Earth’s black horizon obscuring half of the starlit sky. Due to the cabin’s harsh lighting, only the few brightest stars were visible outside.
“OMS safing,” the copilot said as he threw the switches to put the two OMS rockets to bed. As he worked the instrument panels above his head, the AC began the checklist for deploying the two small star-trackers tucked inside Shuttle’s nose. Parker looked up at Overhead Panel-Six directly above his helmeted face.
“Star tracker door controls, System One, to open. Power: Y-axis on; Z-axis on. And we got stars aplenty, Jack. Crank two in and see which way is up.”
In Endeavor’s broad, tiled nose beneath the windshield, two small doors opened without sound. The doors were just under the left window at the Colonel’s left shoulder. Inside the open ports, two telescopic sights, each weighing barely fifteen pounds, scanned the night sky over the dark, southern Indian Ocean 2,000 miles south of the Equator. Each of the shoebox-size trackers searched the black sky for stars chosen by Mother. The Y-axis tracker eyeballed a point of white light to the left of the rightside-up flightdeck. A single star directly overhead was locked in the five-element glass eye of the upward-scanning Z-axis tracker. Automatically, Mother read the angular separation between the two stars and compared that angle to the astronomical ephemeris stored in Endeavor’s mass memory units. Mother reduced the stellar sights to a reading of true local-vertical. Each spherical, attitude indicator in front of each pilot rolled slightly as the ship’s gyroscopes were fine-tuned by the computer conversions taking place at the speed of light among the computers and the two star-trackers built in Boulder, Colorado. The ship’s data processors directed the computer talk.