“You betcha,” the Colonel smiled as he grasped the man’s forearm firmly for a long, quiet moment across the hatch sill.
Within 10 minutes the crew was strapped into their seats in Endeavor’s nose. Mission Commander Parker lay on his back in the left seat with Enright next to him in the right seat. The closeout engineers carefully recited their checklists as they connected air hoses, restraint harnesses, communications cables and aeromedical sensor cables. Before the technicians left the flightdeck with a firm pat upon each flier’s shoulder, the pilots were busy confirming switch positions from Ascent Book checklists. The cabin was warm in the brilliant sunshine pouring in through the six forward windows and the two overhead windows in the ceiling of the aft crew station five feet behind the pilots’ seats.
“Endeavor: Comm check.”
“With you five-by, Flight,” the pilot in command answered.
“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 GN2 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.”