Science Dimension volume 14 issue 1 1982
Across the turning basin where NASA barges unload material too large for trains or airplanes, the U.S. Space Transportation System huddles: the orbiter Columbia, her two solid-fuel boosters, and her external fuel tank. There is a lot of energy in those four containers. The external tank houses millions of litres of "cryogenics", hydrogen and oxygen under such cold and pressure that they liquefy. This will feed the orbiter's three main engines, which can be throttled up or back, turned off, and re-started. Not so the boosters, which once ignited cannot be doused. They are simply linear bombs.
|A proud Canadian achievement (Aili Kurtis Studios)|
The countdown is at two minutes and proceeding smoothly. Eight days ago, it got as far as thirty-one seconds before the Flight Director scrubbed the launch. If today's event can make it past that point, the refurbished Columbia will fly for the second time: the last few minutes of the count are automatic, and no one can prevent liftoff once the 30-second mark is past. Ninety seconds. Five kilometres away, Columbia and her add-ons are clearly visible in the bright Florida sunshine. She looks impossibly majestic, and you have to remind yourself that, like all endeavor, Columbia is still the work of women and men. That humanity emerges in her details. Encasing her external tank is a layer of plastic insulation resembling that on many a basement wall. Columbia owes even her ethereal whiteness to sprayed-on latex paint, the kind you use to cover up the children's crayons. Her miraculous heatshield tiles are waterproofed with humble Scotchguard; and - best of all - woodpeckers from the surrounding bird sanctuary like to nest in her external-tank insulation and must be chased away. Dogs, fruit flies, chimpanzees, and people have gone into space. One of these days Uncle Sam's going to orbit a woodpecker as well.
Thirty seconds! A cheer rises. The launch complex comes to sudden life as immense amounts of water flow underneath five rocket nozzles which will soon spew fire. The waterspray should damp the shock wave that would otherwise rebound and ring Columbia like a bell. That happened on the first mission, was discovered after subsequent data analysis, and has been rectified only recently. At least, one hopes it has been rectified. For Columbia is not ferrying just herself into space this morning. Thanks to a Canadian industrial team coordinated by the National Research Council, she will also take with her one of the world's most sophisticated robots - her "arm in space."
Ten seconds; five seconds. T. Launch Complex KSC-39A is awash in pale gold flame.
A liftoff seen on television, cine film, or still picture is a thing of beauty. But in the flesh, it overwhelms all senses, not just sight. This beauty walks with power. As flame meets waterspray, steam hides the pad. By the time her main engines are up to thrust, Columbia's nose has swayed more than a metre, for she is still tethered by thick steel restraints. Then she swings back to vertical, and the solid boosters kick in. The restraints explode away. Columbia is free. Suddenly, the snout of her external tank rises clear of the tower with careless ease; and she appears, mounting on a sheet of fire. Th e noise is incredible. Suddenly, 5 km seems uncomfortably close. I cannot think; I could not shout. Much nearer the launch complex and this "white noise" would literally tear me apart.
Up in the sky, Columbia and her propellant cluster roll over one-half a turn. It is a move of ponderous grace, like the broaching of a whale. She will stay this way, upside-down with earth above her, till she prepares to land.
Loudspeakers at the viewing site chant height, speed, and downrange distance. At two minutes, travelling about 10 000 km/h, Columbia has dwindled to a bright speck. "SRB separation," say the loudspeakers. I see a white puff as her spent solid rocket boosters are blown away, riding parachutes down to their recovery ships. Columbia is 100 km above the Atlantic Ocean. She will burn her main engines for six minutes longer, jettison her external tank - now scorched, no longer unstained - and fire her secondary propulsion system to achieve her intended orbit. She will then become the world's first spacecraft to have done so more than once. God help the woodpeckers.
As the white column disappears high into the morning sky, there is time to consider the background of this unique craft , and the significance of the remote manipulator arm securely clipped inside her cargo bay. Columbia, though clothed in the most advanced materials, is, after all, basically an idea: a boxcar with wings. The Space Transportation System, as the name implies, means that travel beyond the earth has progressed from exploration to exploitation: NASA soon will treat the void above our atmosphere as a commercial resource. The Space Shuttle is thus not just a bigger, better rocket, but something wholly new - the first true spaceship. Only its external tank gets tossed, tumbling down to break up in the Indian Ocean. The solid-fuel boosters parachute to earth for repeated service, while the orbiter herself is re-usable up to a hundred times.
Initially Columbia and her three sister orbiters will ferry up satellites pre-built by NASA's clients, placing them in precise orbits for a lower sum per kilogram than NASA has yet been able to charge. By the turn of the century, the Shuttle fleet may be constructing solar-power stations several kilometres to a side, or assembling manned Space Operations Centers from thousands of components orbited one load at a time. Each orbiter is the size of a DC-9 and is engineered to haul 30 t of cargo into low earth orbit again and again.
Long-distance haulage, however, is not the same as stevedoring. A boxcar Columbia may be; but once in space, she also needs to handle her 30 t of cargo. This is the task of the Shuttle Remote Manipulator System, which the National Research Council has christened Canadarm. When her engines switch off and the Shuttle coasts into orbit, her men and women astronauts won't be suiting up to take spacewalks in order to stow satellites in, or unstow them from, the cargo bay. Instead, the astronauts and mission specialists will turn to a control station at the rear of the orbiter's cabin. Their commands will open the doors of the cargo bay to a harsh space environment, and then the astronauts will grasp hand controls and put Canadarm to use. Still in the shirtsleeve environment of their cabin, spacemen will become workmen - all thanks to the Canadian arm.
Canadarm will release the satellites it removes in exact position in space, imparting little spin or nudge when it lets go. The arm will also reach out to grapple existing satellites with which the orbiter has achieved rendezvous, bringing them inside the cargo bay for return to earth. In place of a hand, Canadarm has an "end effector", a wire-snare device designed to fit over a special target/grapple fixture on the satellite. As soon as this capture occurs, the end effector pulls the fixture and the satellite attached to it snug against the end effector's rim. Ultimately, other armtips may be used to give Canadarm more precision than the human hand: not simply an arm in space, but also dexterous fingers.
Such work, however, is still in the future. STS-2, the second launch of Columbia, is still a flight test. In it, astronauts Dick Truly and Joe Engle are to use the manipulator in as many ways as possible, proving its efficacy for the more strenuous tasks ahead. Canadian and NASA engineers mated the arm with the orbiter in June of last year, two months after Columbia's maiden flight. This is the first time Canadarm has been into space.
The instant Columbia cleared her gantry, six seconds into her flight, control over her passed from Cape Canaveral, Florida, to Houston, Texas. Thus Columbia's departure is the signal for the Canadian delegation to leave as well. We turn from squinting at the skies, and hurry to board the connecting flight to Houston. The engineers are both confident and apprehensive, like a father at a birth. They have worked flat out for seven years checking each detail times beyond counting. They know no reason why Canadarm should not work perfectly. But the fact remains: this is a test. The outcome cannot be known with utter certainty. Nature always has the final say.
Above Texas, between Orlando and Houston: Through the airplane's window I can see, miles below, a landscape as foreign to Canada as the surface of Mars. Houston lies no farther from Ottawa than Calgary does. Yet here are running water and strong sunshine; leaves on trees; strings of barges, etching white wakes on the twisting streams. On its approach to Houston Intercontinental, the DC-8 buzzes red-soiled scrubland, made for pavement. Golf courses are yellow with drought; only asphalt tennis courts glow green.
At Clear Lake City, a town halfway between Houston and Galveston, is the Lyndon B. Johnson Space Center, the actual "Houston" of the famous radio transmissions: "Houston, this is Tranquility Base." Here are astronaut training facilities, briefing rooms, and Mission Control for all manned spaceflight outside the Soviet Union. Although to a Canadian this climate says June, the sun still sets at five-thirty. I arrive to a press room whose lights blaze into a close night full of moths. What's the news?
|At work, Canadarm will retrieve satellites or place them in orbit. The arm can also be used to inspect the Shuttle while in orbit (NASA)|
The news is that one of the three fuel cells providing electricity to the orbiter appears to have developed a pinpoint leak. Rather than risk complications, Mission Control has instructed the astronauts to shut the fuel cell down. That leaves Columbia with two cells: and although she might easily fulfil her mission on a single cell, the failure awakes a primal NASA fear - ideally, everything should be triply redundant. The rumor now is that the mission will be shortened to two-and-a-quarter days: the 54-hour contingency timeline. It is the same wise conservatism that led to last week's scrub.
But it still cuts the mission in half. If Mission Control does shorten things that much, three distinct test periods for Canadarm will be telescoped into only one: tomorrow, Friday the thirteenth. So this is it. The world is watching. Will Canadarm fluff its lines?
"MOCR," 13 November, 8 a.m. CST: MOCR, pronounced to rhyme with "poker," stands for Mission Operations Control Room. Here sits CapCom (Capsule communicator) Sally Ride, her title a reminder of the time when spacecraft were capsules the size of a home freezer. Flanking CapCom are dozens of support specialists, each named for the subsystem he or she represents. Each monitors a display screen - Canadarm's representative is called RMS. On his display is an aluminum model of Canadarm with crossed Canadian-American flags. At 8:00 a.m., it's official. CapCom has just radioed up to Dick Truly that he and Engle "are going to be coming home early." "That's not so good," Truly replies. His disappointment is understandable. After all, he's been waiting for this mission 15 years.
From the chatter I overhear on the link between the spacecraft and the MOCR, I gather that the first of Canadarm's flight test objectives are being met. We have as yet no visual signal: There is no ground station over the Pacific to send signals from TV cameras mounted in Columbia's cargo bay and on the wrist and elbow of the arm. The large screens at the front of MOCR show the orbit's position against a Mercator map of the world, plus times to next signal loss or acquisition. Truly must now be standing at the Shuttle cabin's aft control station. He has apparently rolled Canadarm to its outboard work position from the storage position it occupies during launch, and has released its retention latches. Up there, 200 km above the earth, Canadarm is at last free in the environment for which it has been so carefully designed.
"Okay," says CapCom. "Establish television feed if you can."
"Established," Engle says after a brief pause. "Transmitting. You people seeing anything down there yet?"
"That's a negative," says CapCom. But then the screen flickers. Ground stations on the west coast are beginning to pick up the television signals.
"Okay! Be advised we're looking at an excellent picture."
And there it is. The end of it all. The payoff for a hundred million dollars,
seven years' work. Spontaneously, the Canadian delegation breaks into applause.
Lit from below and silhouetted against a sector of a blue and cloud-streaked earth, Canadarm swings serenely, its shoulder segment pointing away from the orbiter and its forearm segment pointing sharply down to her again. Twenty metres from baseplate to end effector, the size of two telephone poles laid end-to-end yet less than one-tenth their mass, the Canadian manipulator rests in its "poise" position as the earth slips continuously away above it at 8 km per second. Truly exercises Canadarm in its automatic mode, and it performs flawlessly. It is a sight, a day, an hour, few of the watching Canadians will ever forget.
For the rest of the day (four hours in all), Truly and Engle put Canadarm through its hoops, and the Canadian engineers begin to show their satisfaction; they are witnessing the success of many years work. The astronauts test the arm in all five of its control modes, and "fly" the end effector near a target "grapple fixture" in the cargo bay. The TV cameras atop Canadarm relay spectacular views of the Shuttle: the whole forward cabin from space; a whimsical shot of Truly holding up a sign to the aft window; the great globe floating overhead. Engle and Truly cooperate at the aft station, Truly on the arm controls and Engle firing the reaction-control thrusters - a technique that will become commonplace as Columbia handles larger loads.
There are two, and only two, anomalies. On one of its five control modes, in one of its three joints, in one of its six degrees of freedom, the arm will not respond to one command; the shoulder has a touch of bursitis (a broken wire prevented the execution of the command). And towards the end of the test sequence, the arm's TV cameras stop transmitting (a short circuit in the elbow camera caused the circuit breaker to "pop"). That's all the bad news - negligible beside the good. Engineers have already rectified these minor hitches and Canadarm will fly again on STS-3, now scheduled for March 1982. In the meantime, Canadarm has done everything of the first priority, and much of what it would have been expected to accomplish even in the full five-day timeline.
Truly cannot praise it highly enough. He radios from space that Canadarm is smoother than the earthbound simulators he has practised on in Houston and Toronto. The tests conclude with passive measurements of Canadarm's temperature-control system. Then the arm, once more stretched out and resting in its cradles, is latched, rolled inboard to the cargo bay, and powered down. That night the astronauts go to sleep content, high above a contingent of Canadian aerospace engineers yet more content than they.
In the morning, Saturday, 14 November, Joe Engle and Dick Truly close Columbia's bay doors and burn from orbit. At 3 PM CST, the Shuttle strikes the upper atmosphere. The intense heat of re-entry wraps it in plasma, the "fourth state of matter" which conducts electricity as efficiently as copper and shields the spacecraft from all radio links. Signal is reacquired over the Eastern Pacific; Columbia has come through this reentry as handily as she did her last. She falls unpowered, her glide path that of an aerodynamic brick. But in the denser, lower atmosphere, she regains her grace. Engle swerves her 80 degrees to port, then oscillates her body flap, a combination flame shield and rear control surface, until Columbia noses up and down like a dolphin. Her wingtips leave a strange, intermittent vapor trail. "Digital," murmurs NRC's deputy project head. Indeed, it does appear like Morse-code skywriting on a stratospheric slate.
A headwind combined with a delicate touch on the controls allows Engle to glide the orbiter to a perfect landing, just like that of John Young five months earlier in the Mojave. Her nose wheel sinks like a feather: few commercial airline touchdowns are as smooth. The craft slows, rolling in a cloud of dust to a dead stop, exactly straddling her aim strip. The second flight of Columbia, abbreviated but still triumphant, is over. Canadarm has graduated summa cum laude.
Reprinted courtesy of the National Research Council Canada