The Glass Lady (24 page)

At both ends of the flightdeck, the two crewmen cleared their ears by yawning and by swallowing as the cabin pressure bled down.

The cabin relief maneuver was essential to Enright's planned walk in space to attach the grapple fixture to LACE. The object of lowering cabin pressure by one-third was to protect Enright from the “bends” during his extravehicular activity, EVA, outside. Since the EVA suit would be pressurized with pure oxygen at only 4.3 pounds per square inch, nitrogen gas from the cabin air mixture would bubble out into Enright's blood if he went from sea level pressure into the low pressure of the EVA space suit which was stowed in the mid-deck airlock. Such a bloodstream bubble in Enright's brain or lungs would mean an agonizing and convulsing death in space. To avoid the normal Shuttle EVA preparation of pre-breathing pure oxygen for three hours before going outside, the lowering of the pressure in the cabin's oxygen-nitrogen mixture for several hours would remove most of the nitrogen from Enright's blood. Such was hoped. The Shuttle program had abandoned the cabin-pressure-reduction routine in 1982 as only marginally reliable. The program adopted the more reliable three hours of oxygen prebreathing before the EVA scheduled for Shuttle Five in November 1982. A whole day at the lower pressure was called for by the manual. That much time is required to wash most of the dissolved nitrogen from astronauts' blood. Now, Parker and Enright did not have time to wait and to do things by the numbers.

“Ten point two and holding,” the AC called as he tightly held his nose while blowing hard through sealed nostrils to clear his ears. He ordered Mother to hold that level of cabin pressure.

“Okay back here, Will. Ready for RMS routine.”

“Comin' back, Jack.”

Parker swam back to Enright's side where he plugged into his hoses and cables.

Two hours and twenty minutes out, Endeavor flew over the black sea toward Australia now six minutes and 2,000 miles away.

Jacob Enright at the port side of the rear flightdeck had the inch-thick checklists for the RMS arm lashed to the aft instrument consoles. The pilots prepared to bring the remote manipulator system to life in preparation for capturing LACE with the wire snare at the arm's far end.

Standing shoulder-to-shoulder and facing rearward, the fliers raced the clock to begin the manipulator tests before interruption by Mission Control in Colorado.

The RMS built by Spar Aerospace in Toronto is a 100-million-dollar gift to the American space program from Canada. The exquisitely complex manipulator arm is the single piece of equipment in the billion-dollar starship which cost the American taxpayers nothing.

Enright flexed his knees to reach Panel Aft-14 below his waist. He crouched to read the controls for an emergency jettison of the whole 50-foot-long arm into space.

“RMS jettison pyros, lever-locked safe; jettison command lever-locked safe; retention latches jettison forward, lever-locked safe; midships latch, lever-locked safe; and, aft latch jettison, lever-locked safe . . . She's not goin' anyplace, Skipper.”

“Let's do it then, Jack.”

“Roger,” Enright said over the voice-activated intercom behind his closed, laser-reflecting faceplate. The copilot worked the chest-high control panels: “At Panel-A8A2: Primary power on; command switch to deploy; RMS latches from latch to off to set release.”

Two black-and-white television screens beside Enright's right shoulder blinked “RMS released.” The 905-pound arm was free and resting upon its open triple-latch rests on the portside sill of the payload bay. “And heater switch to auto.”

Inside the 15-inch-thick arm, 26 automatic heaters and thermostats came to life to keep the motors in the arm's shoulder, elbow, and wrist joints no colder than 14 degrees Fahrenheit when Endeavor sped through nighttime's cold of 250 degrees Fahrenheit below zero.

Enright laid his ungloved left hand upon Panel A8A1 at chest level. On the console's lower left corner, a small, red and white maple-leaf Canadian flag flew 130 nautical miles over the southernmost reaches of the Indian Ocean.

“Safing to auto,” Enright called as he went down his thick checklist. “Brakes lever-locked off. Shoulder brace, lever-locked release.” The launch phase, support strut secured to the arm's shoulder joint detached from the RMS arm outside Enright's rear window. “End effector switch to auto; end effector barber-poled derigidize, open, and capture snare extend.”

Fifty feet away from the arm's shoulder joint, the arm's end effector is its electronic fingers, a tubular complex with three wire snares which close around the arm's target when a trigger is squeezed on the arm's pistol-grip rotational hand controller beside Enright's right hand. With the end effector unit's wire snare, the RMS can grab and deploy from the payload bay a 65,000-pound package. The same snare can retrieve from space and stow in the bay a 32,000-pound object.

“Parameter select to POSITION.”

Enright turned a round knob on the Canadian instrument console. He stopped the six-position knob at its POSITION mark. Above the knob, three glass windows with digital numbers blinked to life.

With the setting knob, the pilot of the RMS selects the information to be displayed in the three two-inch-long windows. The display shows one of three dimensions on each dial face. The meters can display the end effector's position in an X-Y-Z coordinate axis, or its attitude in degrees of pitch, roll, and yaw. Or, the knob can direct the three windows to display the angle of bend in the arm's shoulder, elbow, and wrist joints, or the speed of the end effector through space, or the rate of angular change of the moving joints, or the meters can be commanded to show three sets of arm temperatures.

“Okay, position select, Jack.”

The digital numerics on the console's three small meters flashed to life. The dials displayed the X-Y-Z axes of the end effector at the far end of the arm, about 55 feet away from Enright's rear window. The arm remained just touching its three open latches on the port sill of the bay illuminated in the darkness by the bay's six floodlights.

The X-Y-Z coordinate system is a means to identify a point on Shuttle or a place in space close to Shuttle. In the airless vacuum and zero-gravity, the concepts of up, down, left, and right have no meaning without some kind of benchmark for a fixed reference. For Shuttle aloft, that reference is the X-Y-Z coordinate system, a three-dimensional grid akin to the X-Y-Z system drawn on graph paper in high school geometry. The X-axis runs the length of Shuttle from nose to tail down the ship's long axis. Locations along the X-axis are either in front of or behind the zero point on the X-axis. The Y-axis is “horizontal” to Shuttle, passing from one wingtip through the ship to the other wingtip. It is perpendicular to the X-axis. The X- and Y-axis intersect to form a cross within the same flat plane. The Z-axis is vertical. Points along the Z-axis are “above” or “below” the point where the vertical Z-axis intersects the intersection of the X- and Y-axes.

To provide an immovable reference point, the three-way intersection of the X- Y-, and Z-axes must be fixed somewhere in space or in Shuttle. This Zero Point datum is fixed outside of the shuttle. It is located precisely 236 inches ahead of Endeavor's nose tip and 400 inches below the tip of the ship's nose. This is the location fixed in space and memorized within all of Shuttle's computers. From this Zero Point beyond Shuttle's nose, all points within and without Shuttle are measured. It is the permanent, fixed benchmark for labeling up, down, left, right, fore, and aft. From this Zero Point, all directions toward Shuttle along the lengthwise, X-axis are positive. To a crewperson standing on the flightdeck and looking forward, points left along the sideways, Y-axis are negative and points right are positive. And, along the Z-axis from the Zero Point ahead of and below the nose, the direction “upward” toward Shuttle is positive.

With the RMS parameter knob set in the POSITION mode, the end effector's position in space, and the locations of outside targets, are measured in inches from this Zero Point. These measurements in inches are shown in the three meters on the RMS console at the aft crew station.

The RMS is built to function like the human arm. Its shoulder joint and shoulder-joint motor are attached to Shuttle on the portside sill of the payload bay beneath the rear window. The shoulder joint is mounted on the bay sill at a point 679½ inches from the X-Y-Z axis Zero Point. This puts the shoulder joint 37 feet behind Endeavor's nose tip. The 251-inch-long “upper arm” is attached to the RMS shoulder joint. At the far end of the upper arm is the elbow joint, its motor, and the elbow television camera. The 278-inch-long “forearm” stretches aft from the elbow joint. Like the human arm, the shoulder joint flexes left and right, and up and down. The elbow joint flexes up and down. At the aft end of the forearm, the RMS “wrist” is 74 inches long and includes two joint motors. These two motors flex the lower arm up and down, left and right. At the far rear end of the wrist is the end effector unit with its three wire snares which are the arm's fingers for grabbing targets. Mounted atop the forward end of the forearm is the elbow's closed-circuit television camera. Another CCTV camera is mounted on the top of the aft end of the wrist, just on the near side of the end effector. These two cameras feed their black-and-white images to the two wall-mounted screens.

“Ready to run in auto, Skipper.”

“You got the con, Jack.”

“Okay.”

Enright switched on the arm-mounted television cameras and the two CCTV screens to his right.

“Auto one and run. Ready light is on.” A white light illuminated on the Canadian console.

The RMS arm has five different modes for steering the arm through space. In the automatic mode, Mother steers the arm by memory from her computers. Mother has memorized two dozen programs for guiding the end effector to pre-determined destinations outside. Four of these Programmed Automatic Sequences can be called up instantly by turning the RMS mode selector knob to position auto 1, auto 2, auto 3, or auto 4.

Enright chose automatic trajectory Number One. To ask Mother to fly the end effector on a memorized path other than these four routes, Enright must call up a coded, automatic sequence using his computer keyboard in the Command Automatic Sequence mode.

“Lights on,” Enright said as a white IN PROGRESS light illuminated with the arm's first movement out of its cradle.

Mother's computer spoke to the arm's two-joint power conditioners, one manipulator controller interface unit, six motor module/signal conditioners, and six servo power amplifiers. The whole arm rose at the shoulder joint until the arm was straight and rigid, with the end effector suspended two feet above the bay wall. The arm stopped at this position at an automatic, pre-programmed pause point. In Mother's memory are 100 automatic pause points where the arm stops until the pilot tells Mother to advance the RMS arm to the next memorized pause point.

Enright studied the three sets of numbers in the small meters by his chest. He glanced at the two televisions at his right shoulder. He saw the bird's-eye view of the lighted bay as seen from the cameras on the arm's elbow and wrist. Satisfied that the arm would not strike a shuttle structure en route to the next pause point, he pushed a spring-loaded toggle switch upon which he rested his left thumb. On its own, the switch would return to its center, neutral position.

“In motion,” Enright said as he pushed the proceed switch. The arm's joints flexed as the arm bent inward across the open bay. As the end effector moved silently at a programmed speed of two feet per second, the arm stopped at a pause point every few seconds so Enright could consult his televisions before he sent the next proceed command.

“Endeavor: Configure AOS Yarradee at 02 hours, 26 minutes. We have solid downlink from you and your temperatures look fine. We see you depressed to 10 point 2 in the cabin. How's the RMS shakedown going?”

“We're runnin' auto-1 now, Australia. Jack is about to his auto-1 point of resolution at keel Number Two.”

Mother was busy flexing all three of the arm's joints as she flew the end effector through the inside of the payload bay. Each time the joint motors in their “sating” mode brought the arm to a halt without using the mechanical brakes, Enright directed the arm onward. The end effector finally stopped with the far end of the arm in the rear half of the open bay. The end effector stopped two inches above the floor of the bay just to the side of the floor's centerline. Enright consulted his control console before calling the sleeping Australian continent.

“Okay, Flight. We're stopped at keel Two. Showing end effector parameters at X equals 902 inches, Y at minus 4, and Z at 410 inches . . . Right on. Mother flew it the whole way.”

“Good news, Endeavor. We'll be with you six minutes. Colorado will listen quietly as you run the RMS through its paces.”

“ 'Kay, Colorado. I'm takin' the arm up to keel Number One in mode manual-augmented now.”

“We're listening, Jack. And we're getting a super view down here through the arm's elbow camera.”

“Real fine, Australia. We're running manual-augmented, using orbiter-unloaded coordinates . . . Joint angle is up on the parameter display . . . And we've powered up the RHC and the THC.”

“Copy, Endeavor. Rotational hand controller and translational hand controller on in manual-augmented—orbiter dry.”

The remote arm's manual-augmented mode for flying the RMS is a semi-automatic routine. Although Mother flies the entire arm system in the automatic mode, Mother and the arm's pilot work together in manual-augmented.

In the manual-augmented mode, the arm pilot steers only the arm's far end, the end effector unit. The astronaut standing behind the command pilot's empty seat steers the end effector with a gearshift-style stick protruding from its box housing between the two aft windows facing into the payload bay. This is the translational hand controller, THC. The THC directs the end effector in motion through space. Pushing the THC's knobby handle forward toward the rear wall moves the end effector unit, EEU, toward Shuttle's tail. Pulling on the THC directs the EEU backward toward the flightdeck. Pushing the THC left or right, up or down, moves the EEU in the same direction. Where Enright stood at Parker's right, the copilot's right hand can squeeze the pistol grip of the rotational hand controller, RHC. Located in the port corner of the aft flightdeck station, the RHC beneath the two CCTV screens directs the rotation of the EEU about the arm's wrist joint. As the RHC handle is rocked, the end effector moves in the corresponding direction at its stationary position.