Authors: Douglas Savage
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 GN
2
accumulators. And GN
2
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.
“P-52 completed, Jack. We have our REFSMAT.”
“Okay. Crankin' reference stable member matrix into IMU Number Two. So, Skipper, which way is up?”
Will Parker raised a thumbs-up above the center console between their seats. He smiled and deep creases cracked around his eyes. “That way, Jack.”
“Pretty technical stuff,” Enright laughed 100 nautical miles above the black sea 48 minutes from home and 1,500 nautical miles west of Australia.
The crew's momentary respite from work ended abruptly when a square light labeled SM ALERT lighted with a warning tone beneath the left CRT screen above the center console.
“Systems management!” the AC called as he pushed the alert-light pushbutton to kill the audio alarm. Above the center television, on the 40-light annunciator unit, the rectangular warning light labeled FUEL CELL REAC glowed ominously red.
“Running it down,” Enright said as he tapped out a sequence of numbers on his small keyboard on the center console by his left thigh. A fuel cell malfunction checklist blinked onto the right CRT screen.
Endeavor carries three independent electrical systems, each fed by the super-cold liquid oxygen and liquid hydrogen tanks nestled beneath the floor of the still-closed, payload bay. Each fuel cell contains 64 stacks, or chambers, where preheated liquid oxygen and hydrogen meet to form electricity and waste water. The water overflow is filtered and decontaminated with iodine for crew drinking. Each fuel cell generates direct-current electricity for one of three DC circuits: Main A, Main B, and Main C. Each DC bus is routed to three inverters which convert the direct current power into alternating current used by Shuttle's systems. Fuel cell Number One feeds DC circuit Main A, which is converted to AC line AC-1. Fuel Cell Two feeds DC Main B and AC-2, while fuel cell Three powers DC Main C and AC-3.
“Looks like Main B, Skipper. Running it down. . .”
The electricity output meters and all electrical distribution controls are the domain of the copilot in the right seat. Enright followed the video checklist as he managed the bulky fuel cell by the switches and meters located in front of his face and next to his right arm on Panel Right-One on the cabin wall.
Enright first checked the temperatures in fuel cell Two's twin stacks of electricity-generating cells.
“A hundred ninety degrees and two hundred ten degrees. Stack temps okay.”
The copilot examined the three round meters above his right knee on the forward panel. He turned a large, round knob until it pointed to Cell Two.
“Two kilowatts at 31 point 5 volts DC; 60 amps. Looks okay, Will.”
Then Enright asked the green CRT about cell Two's water output.
“Damn. There it is, Skipper. Six pounds per hour water production. That's two pounds too high. Got room? She's barfin' water.”
“Let's see,” the Colonel drawled. “Plenty of room in potable water Tank B. Tune her down if you can and we can manage the damn thing later . . . I hope.”
Shuttle carries five potable water tanks for collecting water generated by the three fuel cells.
“Crankin' her down, Skip. Okay. Lights out.”
The red Caution and Warning light flickered and winked out.
“We'll let Mother in systems management mode keep an eye on that baby, Number One. Meanwhile, let's go on down the routine.”
As the crew interrogated the computers, Mother put her finger on the fuel cell Two vitals, like any mother laying her face against a feverish brow. Enright followed his bloated baby out loud.
“Power controller assembly, check . . . load controller assembly, check . . . mid-power controller, check . . . forward load controller, check . . . aft load controller, check. Looks stable, Skipper. Three essential bus linesâ1BC, 2CA, and 3ABâall look healthy. Strange glitch in there some'eres.”
“Fine, Jack. At least we won't have to light the candles. Don't want to repeat STS-2!”
Both fliers had thought of Shuttle Two in November 1981, which was brought home early after only half a mission when a whole fuel cell threw up and drowned in its own water.
The headphones crackled in the south sea night.
“Endeavor, Endeavor. Yarradee has downlink at fifty-one minutes. Be with you for six. We're looking at a fuel-cell saturation C-and-W.”
“Mornin', Australia. Rogo on the caution and warning,” the command pilot called to Australia's western coastline, which Shuttle would not cross this pass as she coasted heads-up past and under Australia's southern shore. “Number Two fuel cell burped up but Jack got a blue bag on her in time. Keepin' an eye on it. We've aligned the platforms and everything is right and tight. How do we look by PM downlink?”
“Real fine, Will. Telemetry is coming in crisp and clean. You are in plane and closing on your target now fifteen miles ahead of you and ten above you. R and R-dot are right on. You have a Go for closed loop rendezvous.”
“Roger, buddy. Understand we can run with on-board range and range-rate digitals. How's Brother Ivan?”
“Ah, we show Soyuz now in daylight just south of Norfolk Island, about 170 degrees east by 30 south. They're radio silent within two miles of the target. They should be braking very soon. No comm with them at all so far.”
“Copy, Yarradee. We're ready for Terminal Phase Initiate up here. Jack's called up our MCC-3 digitals which you should be lookin' at now.”
“We see it, Will. Mid-course correction three looks fine, well within your propellant budget. After you lose contact with Orrora, we want you to roll minus-Z well before sunrise which will be at seventy-six minutes, MET.”
“Got it, Flight.”
“Endeavor: Let's see PCMMU Number Two for a while, please. Your downlink data still looks a bit noisy.”
“You got it, Flight.”
Endeavor's Pulse Code Modulation Master Unit controls the flow of on-board operational instrumentation data from Shuttle's systems by way of 13 signal conditioners. The signal conditioners convert Shuttle's vital signs to computer talk which one of two PCMMU black boxes routes to a Frequency Division Multiplexer for telemetry broadcasting to the ground through the Network Signal Processor.
“And your TM data now looks real clean. Much better, Endeavor.”
“Fine, Flight,” the pilot in command radioed.
“Yeah, Will. We were afraid you had a quad glitch.”
Endeavor speaks to the ground over seven, S-band antennae: Four “quad” antennae surround the rear cockpit bulkhead; there is one “hemispheric” antenna in the cockpit ceiling and another on the underside of Shuttle's nose behind the nose wheel well; and, the seventh antenna is located on Endeavor's back just ahead of the closed payload bay doors. Mother chooses which antenna is the best for a direct shot to the ground stations. The crew can also pick the best antenna combination should the computers get lazy. In all, Shuttle carries 19 different antennae built by Watkins-Johnson in San Jose, California.
“Before you lose us by Yarradee, Endeavor, we'd like you to run a COAS shot as soon as you can. Let us know how it flies before you lose Orrora. Your S-band is breaking up at . . .”
“So long, Yarradee . . . Okay, Jack. I'll take a shot here with the COAS. We'll have Orrora contact in two minutes.”
“ 'Kay, Skipper.” Enright was busy fiddling with his electrical controls and meters.
As Endeavor skirted Australia's southern coastline, Parker reached overhead to instrument Panel Overhead-One, where he turned on the COAS power. To the left of a four-inch-square panel containing 25 white computer status lights above the AC's forehead, the eight-inch-long tubular sight of the space sextant, the Crew Optical Alignment Sight, came to life.