Authors: Douglas Savage
“Copy, Endeavor. At T minus 70 minutes, we have hatch closed and sealed. We'll run the cabin pressure integrity tests by hardwire from here.”
“Okay, Flight. Thanks,” the Mission Commander drawled slowly.
Shuttle is pressurized with a normal air mixture of one part oxygen to four parts nitrogen. This mixture is maintained at sea level pressure of 14.7 pounds per square inch on the ground and in space. Cabin air is supplied by the ship's Atmosphere Revitalization System, the ARS.
Shuttle's environmental control system is a maze of plumbing, pipes, heat exchangers, and space radiators, all manufactured by Hamilton Standard.
The ARS is the lungs and the sweat glands of Shuttle. Like the hands which created her, Shuttle keeps her iron bowels cool by sweating water from her aluminum pores. Heat from Shuttle's vital organs and black boxes, and from the bodies and the breath of her crew, is absorbed by two water loops. Water circulates through each loop, picking up heat along the way. That heat is transferred to twin freon coolant loops. The freon refrigeration fluid carries the heat to tubular radiators attached to the inside of each of the two, 60-foot long doors of the payload bay. In space, when the doors are opened, the radiators in the shade of Shuttle's wings radiate the freon's heat into the cold of space, like a perspiring athlete spreading his wet arms wide to a cool breeze.
During launch and the fiery re-entry from orbit, heat is sweated out as steam by two flash evaporator units inside Shuttle's tail section. During the last minutes of re-entry and landing, two ammonia boilers sweat out the heat load from the freon loops.
“Endeavor: At T-51 minutes, we'll be aligning the IMU's at this time. And you can crank up the water boilers now.”
“Rogo, Flight,” Parker replied.
In Shuttle's nose, three Inertial Measurement Units, IMU's, were being fine-tuned to feel the ship's way into space. Each IMU is a complex array of motion and acceleration sensors which “feel” Shuttle's position and where she is going. Just as a child's spinning top wobbles as it winds down, so the IMU's wobble from precession and must be realigned to proper positions. The IMU alignment is a computer-generated order which tells the IMU gyroscopes where Shuttle sits at Pad 39 and where she is bound: A tiny needle's eye in space 800 miles to the east. “Where am I now?” the sealed black boxes in Endeavor's avionics bay demand. And the computers reply: “You stand with your tail feathers in the sand at Cape Canaveral, Florida, 28 degrees, 36½ minutes north latitude by 80 degrees, 36¼ minutes west longitude. When you leave the ground, you must twist your tail, which now points southeast, until it points northeast so you will cross the Equator half a world away at an angle of thirty-eight degrees.” And a world away, ninety minutes from lift-off, the IMU's must find their whirling target, LACE: Hitting a bullet with a bullet, each traveling at a velocity over the Earth of 25,460 feet per second.
“Okay, Flight,” Parker confirmed. “GPC and BFC have accepted the IMU alignment.”
Each of the three IMU's was aligned to a slightly different reference point so each unit could be cross-checked against the other two.
“We see it, Endeavor. Main computers One through Four have the state vectors. Your GPC Mode Five is stand-by. Execute Item 25. Then proceed with ARS routine.”
“Roger, Flight. Challenge and readback, Number One.”
Enright, flat on his back, consulted his thick Procedures Manual open in his lap. He recited the checklist.
“Cabin Atmosphere breakers closed, Main Bus B, Overhead Panel Fifteen, Row D: Cabin delta pressure and delta temp, nitrogen supply Number Two, oxygen-nitrogen controller Two, oxygen crossover valve Two, nitrogen regulator inlet Number Two, and, cabin relief A. All closed, Skipper.”
“Confirmed, Jack.”
“Atmosphere pressure control breakers, Main Bus A, Overhead Panel Fourteen, Row D: Nitrogen supply Number One, oxygen-nitrogen controller One, oxygen crossover Number One, nitrogen regulator inlet One, cabin vent and isolated cabin vent, all breakers closed, Skipper.”
“Okay, Number One. Confirm emergency oxygen and cabin relief valve Bravo breakers closed, Overhead Panel Sixteen, Main Bus Charlie.”
“Confirmed, Skipper.”
“And on my side, Jack: Flash evaporator feedline heater running alpha supply Number One and bravo supply Number Two, Panel Left-Two. On my Panel Left-One: Humidity separator alpha on, bravo off; cabin fans A and B on; water pump Loop One to GPC with Loop Two off; Loop One bypass to auto; water Loop Two to auto; and, flash evaporator controllers, Primary A and B to GPC.” The command pilot followed the checklist in his lap.
“Confirmed, Skipper.”
“Okay, Flight. ARS is powered up and full of Go.”
“Roger, left seat. We're Go at T-30 minutes. We are now updating the SRB guidance for winds aloft.”
The ground computers spoke to the black boxes within each of the two solid rocket boosters strapped to the sides of the external tank. Final steering commands told the SRB computers how best to cleave the high altitude, winds aloft encountered during the first 60 seconds of launch. So vicious were these winds during the launch of STS-5 in November 1982 that Mission Control nearly canceled the Veterans Day launch.
“Endeavor: We'll be pressurizing the OMS and RCS pods in a moment.”
“We'll watch it, Flight,” Enright called into the twin microphones inside his helmet.
In Endeavor's tail, gaseous nitrogen pressure increased in each of the two orbital maneuvering system pods.
One OMS pod, 22 feet long and 12 feet wide, protrudes from each side of Endeavor's vertical tail fin. The rocket engine, ignition system in each pod fires the single, large rocket at the back end of each OMS pod. Each of the two OMS engines drives Shuttle with 6,000 pounds of thrust after the three Shuttle main engines have finished their work during the launch. Gaseous nitrogen opens the pneumatic activation valves which send fuel and oxidizer to the thrust chambers of each OMS engine. Without 360 pounds of gas pressure in the ignition valves, the OMS engines cannot fire to give Shuttle its final push into orbit, to provide power for large maneuvers in space, and to slow Shuttle so she falls from orbit at journey's end.
“We see 2,500 pounds in the main GN
2
tanks, Flight,” Enright called from the copilot's right seat.
“We confirm, Jack.”
In the three reaction control system units, one in Endeavor's nose and one in each OMS pod, gaseous helium pressure increased in the two helium tanks carried within each RCS module. The helium pressurized each RCS unit's fuel tank topped with 930 pounds of monomethyl-hydrazine and one oxidizer tank filled with 1,488 pounds of nitrogen tetroxide.
“We have gas pressure in RCS forward and aft left and right, and in OMS left and OMS right, Flight.”
“Roger, Endeavor. At T-22 minutes, your primary avionics are on line.”
Throughout Endeavor, black boxes warmed to life. Navigation beacons prepared to steer Shuttle back to an emergency landing at Cape Canaveral's concrete, three-mile-long runway if a launch malfunction during the first 265 seconds of powered flight dictated a high-speed turnaround for a perilous Return To Launch Site abort, or RTLS. In the mission simulator, Parker and Enright had bent their metal and had gotten their feet wet more than once.
“Copy, Flight. Configured for RTLS steering . . . Let's hope not,” the AC sighed.
“Endeavor: At T-20 minutes, configure GPC to ascent OPS-1”
“This is the AC. We're running computer Operations Sequence One outbound. Cabin vents comin' closed now.”
“Roger, Aircraft Commander.”
Endeavor's four primary General Purpose Computers concentrated on the OPS-1 launch program for steering the powered launch phase. In the fifth back-up GPC, a separate ascent program ticked away, ready to fly Shuttle aloft if computers One through Four should fail. Trajectory graphs blinked upon the front instrument panel's three television screens on the flightdeck.
“Endeavor: You're Go at T-19 minutes and counting. Configure computer Error Logic to RESET position, and configure GPC to MM-101 and OPS-9.”
“Copy, Flight,” the AC called. “Major Mode 101 is running.” With Operations Sequence Nine, the on-board Shuttle computers were taking Endeavor's pulse as her own black boxes monitored the computerized, pre-launch checkout. Shuttle is America's first manned spacecraft designed to automatically launch itself with its own, onboard computers.
“Endeavor: You're Go at fifteen minutes and counting. We're now conducting the nitrogen purge of the SRB skirts. Configure OMS and RCS crossfeed valves for launch.”
“Okay, Flight,” Parker replied lazily. The command pilot was relaxed and ready to fly. With his legs elevated above his reclining body, the throbbing in his right leg ceased and he was comfortable.
“Okay, Number One. Panel Overhead Seven: Left, aft RCS pod, crossfeed lines One and Two configured GPC talk-back closed, and crossfeed lines Three, Four, and Five, configured GPC talk-back closed. Right, aft RCS crossover lines One and Two to GPC talk-back closed. Lines right Three, Four, and Five, to GPC talk-back closed. And, master RCS crossfeed locked off.”
“Okay, Flight. Our RCS crossfeed is ready to go.”
“Copy that, right seat. We're listening.”
“Ready for OMS, Skipper.”
“With you, Jack. Panel Overhead Eight: Left OMS crossfeed Loop A and Loop B to GPC talk-back closed. Left OMS engine, lever-locked armed, Panel Center Three. OMS right: Crossfeed Loops A and B to GPC talk-back closed. Right engine lever-locked armed, Panel Center Three . . . OMS primed and ready, Flight.”
“We copy, Endeavor. At ten minutes and counting, we see cabin vents are sealed.”
“Roger, Flight. Vents closed.”
Fifteen hundred miles to the north, an exhausted Admiral nodded his sagging face. A Colonel at his side spoke into a red telephone in a glass room where no sun ever shines. The haggard Colonel laid the phone down gently and he wiped his hands upon his thighs as if the instrument were unclean.
“Endeavor: You are Go at T-9 minutes. Start your event timers at this time. The Ground Launch Sequencer now has the con.”
“We see it here, Flight.”
The countdown was now fully automatic. The master launch computer could either let the count go to zero or could stop the countdown at any moment.
“And, Endeavor, we are now feeding you the new PTI-7 routine for re-entry.”
The two pilots flat on their backs glanced sideways at each other. Five on-board computers swallowed the Programmed Test Input Number Seven to be engaged during re-entry.
“Alright, Flight,” the Colonel shrugged high atop Pad 39-A. “We see lox tank in the ET topping off now.”
Inside the silo-size external tank bolted to Endeavor's belly, the liquid oxygen, or LOX, tank had been continuously venting out frigid vapors into the clear morning air. As the super-cold gas vaporized, the ET's supply of 140,000 gallons of liquid oxygen was steadily replenished through lines running from the launch tower. Now the replenishing and venting of oxygen stopped so the sealed tank could build up flight pressure.
Twenty-seven hundred miles away, over California, the killer satellite LACE crossed the American coastline at its ground speed of 300 miles per minute. The silent, slowly tumbling bird whirled eastward toward Florida. LACE would soar directly over Cape Canaveral at the instant Shuttle rode the fire into the sky.
“At seven minutes and counting, Endeavor, the access arm is in motion. You're on your own, guys.”
Outside, the catwalk from Pad 39-A jerked away from Endeavor's closed side hatch. The long arm would require one minute to swing back to its locked position next to the tall gantry well clear of Shuttle.
As the crew access arm left Shuttle's glass side, Endeavor at last stood naked and white in the dazzling daylight. Portions of her round nose and the forward parts of the two OMS pods showed slightly dark scorch marks from her past re-entries from orbit.
Along Cocoa Beach and the Kennedy Space Center's Merritt Island sands a thousand eyes squinted into the sun as hearts beat faster in time to the two hearts strapped within Endeavor's aluminum soul.
“Endeavor: At six and counting, confirm faceplate visors closed and locked. Configure APU for startup.”
“Roger, Flight,” the command pilot called as he and Enright pulled their clear faceplates down over their faces. As each pilot locked his faceplate into position on his helmet, the pilots' nostrils inhaled the spaceman's blend of bottled air laced with the smell of rubber hoses and sweat.
“Ready for APU checklist, Will,” Enright called through the flightdeck intercom. His voice was anxious.
When the three auxiliary power units were lit to supply pressurized hydraulic fluid to Shuttle's wings and tail and to the steering motors which swing the three space shuttle main engines, the ship would be committed to fly within five minutes. Failure to go would mean shutting down the APU's and returning to the T-20 minute point in the countdown to give the APU's time to cool. Enright was tense. Like a pilot's first solo flight from a long-ago grass field, like a body's first wet kiss, to practice for a lifetime cannot dilute the gut's tension at the event. Enright raised his right gloved hand to the instrument panel above his right elbow. He had done so a thousand times before, in the mission simulator and in his sleep. But this was the first time he did it with his hands sweating.
As his captain recited the checklist for the APU's, Enright's right hand waited for each command before his fingers threw the silver toggle switches.
“Okay, Number One, this one's a keeper. On Panel Right-Two: APU Numbers One, Two, and Three, controller power lever-locked on.”
Enright flipped three switches.
“Fuel tank valves One, Two, and Three lever-locked open.”
“And, APU's One, Two and Three barber-poled as ready, Skipper.”