Skylab's Fiery Fall

With varying degrees of fear, anger and fascination, but mostly with a detached kind of bemusement, the world this week awaits an unprecedented event: the fiery fall of the largest machine man has ever hurled into space. The American Sky lab vehicle, nine stories tall and weighing 77.5 tons, is expected to slip into the earth's upper atmosphere, then disintegrate into a celestial shower of flaming metal as spectacular as any of last week's Fourth of July fireworks displays. Somewhere, probably at sea, ten fragments, each weighing 1,000 Ibs. or more, will crash to earth at speeds of up to 270 m.p.h. with the force of a dying meteor. Thus will be observed, after a series of miscalculations, the tenth anniversary of man's proudest achievement in space, the walk on the moon.

Despite all their wondrous tracking stations, bristling with huge radar antennas and feeding the most advanced electronic computers, America's top military and civilian space scientists could not predict even roughly where Skylab would fall. Until the final hours, they could narrow the area of eventual impact only to a vast global band between 50DEG north latitude and 50DEG south latitude--a sweep of about 109 million sq. mi., or nearly 56% of the earth's area. Conceded Hal Sierra, one of the technicians monitoring Skylab's death throes from the Lyndon B. Johnson Space Center near Houston: "We're balancing on a knife edge--but we're not sure where the knife is."

Officials of the National Aeronautics and Space Administration, which conceived and launched Skylab six years ago, took comfort in the mathematics of probabilities. Some 500 fragments of the huge space workshop will be dispersed over an area 4,000 miles long and 100 miles wide, a scattering that the scientists call, with anthropomorphic archness, Skylab's "footprint." Moreover, on each of Skylab's 90-minute orbits of the earth, nearly 67 minutes, or 75%, is spent over water. What all that means, contend NASA'S statisticians, is that the chance of any remnant striking a human being is only 1 in 152; the probability of any specific person being struck is 1 in 600 billion--far less than the chance of being hit by a bolt of lightning or winning a lottery.

NASA, however, was not taking the potential danger at all lightly. One of the heaviest pieces of Skylab, a two-ton lead-lined vault used for film storage, is capable of digging a hole 5 ft. wide and 100 ft. deep. And within the band of Skylab's orbital paths lie some of the world's most populous areas, including all of the U.S., much of Europe, India and China. Indeed, the chance of debris falling in some city of at least 100,000 inhabitants is a sobering 1 in 7. Only 10% of the earth's inhabitants can be considered totally free of any risk from Skylab's metallic fallout.

Despite the perils, many Americans seemed to take a perverse pleasure in spoofing the unwelcome visitor from space. Skylab stimulated a lot of harmless hucksterism, revived some old promotional gimmicks, even became an excuse to throw parties. Inevitably, Chicken Little emerged as a dominant theme, now crying, "The Skylab is falling! The Skylab is falling!" The analogy was not quite apt, but feathers and beaks were the dress of the day for Skylab watch parties from Minneapolis to Manhattan. Guests at the "first and last annual greater New Orleans Skylab observation party" were asked to bring binoculars, telescopes and crash helmets. Jay Schatz, owner of a luxury high-rise apartment building on Chicago's Near North Side, scheduled a sub-basement party for tenants that would begin two hours before Skylab was expected to break up. Radio stations eagerly joined the hoopla. Ohio's WNCI-FM in Columbus offered $98,000 to the first Ohioan bringing in a locally found piece of the Skylab wreckage within 98 hours of impact. In Atlanta, callers could win yellow T shirts bearing a bull's-eye and the words I'M AN OFFICIAL WQXI-AM 79 SKYLAB TARGET.

An old-fashioned newspaper promotion battle broke out over Skylab in San Francisco. The Examiner got the jump on its rival by offering $10,000 for any Skylab relic, and even before the reentry, readers were bringing in hunks of metal scrap. The Chronicle responded with a black-bordered frontpage notice that any of its subscribers could collect up to $200,000 for personal and property damage from the space station. Chicago Insurance Expert Robert Schultz belittled such offers by advising that anyone who holds a standard homeowner's policy is already covered against Skylab.

There were many variations on the theme. New Hampshire Attorney John Ahlgren advertised "free legal services for people hit by falling pieces of Skylab" outside his Portsmouth office. But he saw a serious side to the event too. "People feel at the mercy of forces they cannot control," he explained. "Concern is mild, but it's there." An ad hoc Spokane, Wash., group called the Skylab Self-Defense Society hung a 15-ft. bull's-eye on the side of a downtown office building and suggested, "Make Spokane the target for Skylab's landing. If you give the Government a target to shoot at, it's bound to miss. That is our greatest protection." Throughout the U.S., Skylab "survival kits," usually including plastic helmets and targets, were selling well. There were also numerous office lotteries based on when or where Skylab would fall. At the White House, Presidential Press Secretary Jody Powell was said to have $2 riding on his best impact guess: the Arabian Sea.

At an increasingly busy public information switchboard at the Johnson Space Center, one of the most frequent questions from callers was whether pieces of Skylab would remain Government property and must be surrendered by their finders. "No," replied NASA'S Terry White. "We slammed the hatch on Skylab in 1974. Anyone can keep the pieces and put them on their coffee tables."

Other questioners asked why the U.S. could not fire a nuclear missile that would blast Skylab to smithereens. The official answer: this is prohibited by international treaty. Refusing to accept that, some enthusiasts tried anti-Skylab measures of their own. Buryl Payne, director of Massachusetts' Institute for Psychic Energetics, used a Fort Lauderdale, Fla., radio station to tie in with 150 other stations and reach some 40 million listeners in seeking a mass psychic push to nudge Skylab into a higher orbit. In the broadcast, listeners were instructed to "relax, visualize yourselves as being in contact with Skylab and then visualize Skylab as moving out into space." Despite such positive thinking, Skylab kept slipping closer to earth.

More practically, the watching world would have to depend on the men who put Skylab into space to find the best means of bringing it back to earth with minimal risk to human life. The first priority was to track Skylab's decaying orbit as precisely as possible. That is the job of the North American Air Defense Command, whose joint U.S.-Canadian computers deep within a pink granite mountain near Colorado Springs, Colo., continuously monitor the movements of 4,506 hunks of space garbage now orbiting the earth.

The worldwide array of NORAD'S space-tracking stations, using infra-red detection devices as well as radar, is so discerning that it can track an object even smaller than a basketball at a range of 20,000 miles. Even an astronaut's glove is being tracked. Beyond Skylab, the heaviest object aloft is now Salyut 6, the Soviets' manned spacecraft. Every month about 40 man-made objects re-enter the atmosphere, but only a fourth survive to strike the earth. There has never been a reported injury, although the fall of Cosmos 954 over northern Canada in January 1978 led to fears of radioactive contamination from its nuclear power packs (there is no radioactive material aboard Skylab).

The NORAD calculations are being transmitted by phone to a windowless room at the Johnson Space Center, where four five-member teams take turns watching monitor screens round the clock. On one wall hangs a lO-ft.-high chart detailing the altitude of the falling lab, day by day. The room, No. 314, is far plainer than the control center from which the Apollo moon missions were directed. The watch teams receive fresh telemetric data from Skylab whenever it gets within radio range of one of five NASA tracking stations (in Santiago, Chile; Bermuda; Ascension Island; Madrid; and Goldstone, Calif). On these "passes," controllers can still make small adjustments in the space vehicle's position relative to earth. This is possible for only four minutes out of every 90. Says Don McDonald, one team member: "It's 1 1/2 hours of boredom, then four minutes of terror."

The crucial final countdown will begin when Skylab drops to about 120 miles above earth, roughly 48 hours before its re-entry into the atmosphere. At that point, a higher-level interagency team of experts, including NASA Administrator Robert A. Frosch, will take up positions in the Skylab Coordination Center on the sixth floor of NASA headquarters in Washington. Getting his information and recommendations from the Houston center, NORAD and the Marshall Space Flight "enter at Huntsville, Ala., Frosch will make the final decisions on what, if anything, should be done to try to influence Skylab's final fall.

The options are limited. On June 20, NASA's team members used up precious bursts of the spacecraft's dwindling propellant to turn its nose horizontally by 90DEG and into a sideways position, which exerts increased drag against its forward movement. That change gave NASA its best chance of some final control. Explained Cindy Major, 27, one of the Houston monitors: "There is more pressure now because the attitude of the spacecraft is more sensitive. There is no room for error."

The key decision is to be made when Skylab falls to a height of about 90 miles above earth, some twelve hours before estimated reentry. At that point the controllers could use some of the 6,000 remaining pounds of fuel to rotate the craft into various nose-forward, "low drag" positions, in the hope that this would prolong Skylab's life by anywhere from one to five more orbits. By contrast, a second option would be to send the vehicle into an early tumble, which would cut from one to three orbits from its natural, uncontrolled reentry. A third option would be to do nothing and let gravity take its course.

The choices were to be made on the basis of a complicated "hazard index," a computer calculation used to determine the final orbital paths that would take the spacecraft over the least densely populated areas. Frosch has already made one firm rule about reaching those last critical decisions: Skylab will not be sent into an orbit posing a high hazard in hopes of later reaching an orbit of lesser risk. That is because NASA is simply not certain that its efforts to select the precise final orbit will work. To do nothing in such a situation is preferable to taking a high-risk gamble and failing. Amid all those uncertainties, the engineers think the best final orbit would take the craft over the southern part of South America, across southern Africa, the Indian Ocean and India, then over China and the Pacific.

Even with all the planning, the margin of possible error is uncomfortably large. At about six hours before reentry, NASA'S projected impact points for Skylab's disintegrating parts occur somewhere along a path of 40,000 miles--nearly twice the circumference of the globe. At two hours, the final anticipated flight track still extends over a 13,000mile path. Testing its prediction on a falling Soviet Cosmos booster stage on April 29, NORAD made an estimate two hours before re-entry-- and missed the actual impact points in the Pacific by 4,000 miles.

If the Skylab debris strikes a populated area, the U.S. Government will hear about it in a hurry. The State Department last month designated one member in each of its overseas missions as a Skylab officer to brief foreign governments on the facts of the spacecraft's fall and what the U.S. was prepared to do in case of serious damage. In India, the U.S. specialist, Thomas Vrebalovich, went to unusual lengths to pacify critics of the American space venture. He told journalists that if NASA faced the choice of steering Skylab toward either India or America, it would most certainly select the spacecraft's homeland. India's 83-year-old Prime Minister Morarji Desai joined in trying to calm his people's fears. Said he: "Don't get nervous and worried before it happens. It's no use dying before death comes."

The U.S. has assembled "go teams" consisting of NASA experts, Defense Department engineers, Red Cross aides, State Department diplomats and Justice Department lawyers--all on alert to be flown by the Air Force to any nation seeking help. China has already agreed to receive such a team if Skylab wreaks havoc there. The Russians, on the other hand, have rejected the offer. "We are responsible at law; there is no question about that," concedes one NASA lawyer.

Here too the American capacity for joking about Skylab flourished. Columnist Russell Baker proposed a series of letters for NASA to send, depending on where Skylab fell. Example: "Dear Greece: It's a crying shame about the Parthenon, but as American daddies used to tell their sons back in the days when the Model T finally broke down, nothing man makes will last forever."

In case of a serious Skylab crash in the U.S., Washington expects local fire, police and medical authorities to provide any needed emergency service. A team from NASA would go to the area to give technical advice and help document claims, while the Federal Emergency Management Agency would coordinate aid on a regional basis. Actually, few localities, if any, have made advance plans for such an unpredictable accident.

People seeking advice from NASA on how to minimize their own risks from Skylab got little help. The agency suggested that one might be a shade safer underground than on the surface, but it warned that the very act of, say, taking a car to get to an underground shelter might increase the danger--because the chance of getting hurt in a car accident is greater than the risk from Skylab. As a general rule, space experts suggested, "Do nothing."

Both in the U.S. and abroad, some editorialists asked a bit testily how NASA ever got in the awkward position of permitting tons of metal fragments to endanger wholly innocent earthlings. Some of the agency's sympathizers blamed the "bean counters" in the Federal Government's budget bureaucracy during the Nixon Administration for forcing NASA to build its Skylab "on the cheap," mainly with leftover hardware from the successful Gemini and Apollo manned spacecraft programs. Astronomer Mark Chartrand III, chairman of New York City's American Museum-Hayden Planetarium, claimed Congress was at fault in its financial shortsightedness. Said he: "Hell, if I had my way, I'd target Skylab to fall on Congress while it is in session."

Originally, NASA had proposed in 1968 the $2.6 billion orbiting laboratory program. At that time extra rockets capable of keeping Skylab in space almost indefinitely were considered. The craft's ability to stay in orbit would be reinforced, if necessary, by astronauts transported up to it in a convenient space shuttle, then also on the NASA drawing boards. But under budgetary pressures both vehicles were simplified--and both developed unanticipated technical problems. So when Skylab's orbit began to slip, there was no shuttle to come to its rescue.

In fact, Skylab's history of glitches demonstrated both the futility of taking technological shortcuts and the agility of men working in space to remedy unexpected ailments. When Skylab was launched by a Saturn 5 booster rocket on May 14, 1973, a large section of its meteoroid and heat shield ripped away, taking one of its prematurely extended solar-energy wings with it. A second wing jammed in a retracted position. The craft both overheated in orbit and was dangerously underpowered. But in the space age's first salvage mission, on May 25, 1973, Astronauts Charles ("Pete") Conrad Jr. and Joseph Kerwin entered the overheated space lab and rigged a makeshift umbrella to shade the vehicle's bald spot, then spent a harrowing four hours outside the stricken craft freeing the stuck wing. During a second manned mission, on July 28,1973, the lab's thrusters sprang leaks--and a crash program to prepare a vehicle to rescue the three astronauts was undertaken. The astronauts shut off the leaking system, and the rescue mission proved unnecessary. On the third and final mission, on Nov. 16, 1973, Astronauts William Pogue and Edward Gibson struggled for three hours outside Skylab in getting a vital radar antenna adjusted and repaired.

In the course of its troubled flights, Skylab crews established an endurance record of 84 days in space--a mark since surpassed by Soviet cosmonauts. More than 50 scientific, technical and medical experiments were conducted. Some 183,000 unprecedented pictures of the sun were snapped through Skylab's telescope.

Ironically, despite NASA'S concentration on solar research with Skylab, the agency's failure to anticipate the extent of sunspot activity during the vehicle's years in orbit contributed substantially to the craft's death. Russian scientists as well as America's own National Oceanic and Atmospheric Administration had predicted considerable solar disturbances, including great magnetic storms and solar flares. When they erupted in 1977 and 1978, they warmed the gases in the earth's outer atmosphere, increasing the drag on Skylab. Never fully powered because of its lost solar wing and failing batteries, the craft began to slip ever closer to earth.

One by one, methods of rescuing Skylab were considered by NASA and then discarded as impractical. There was talk of a joint Soviet-American mission, using the Soviet Soyuz system, but it had to be abandoned because the Russian craft's docking hardware was incompatible with Skylab's. Soyuz also lacked sufficient propellant to maneuver with the ailing U.S. vehicle and then give it a powerful boost into higher orbit. Declared NASA'S Frosch: "The obstacles involved were insurmountable, in the time remaining." Russian scientists, in effect, agree, although they note that if plans for a cooperative effort had been started two years ago, a rescue might have been possible. Roald Sagdoyev, director of the Institute of Space Research of the Soviet Academy of Sciences, told TIME: "All the operations needed to give Skylab an additional impulse could have been made within the limits of existing rocket and space technology--either American or Soviet." The U.S., he said, could have helped modify the docking locks of Soyuz so it could link up with Skylab.

The NASA engineers studied a plan to send a McDonnell Douglas F-15, America's hottest jet fighter, into a computer-guided supersonic climb to about 80,000 feet and then blast Skylab out of the sky with a non-nuclear rocket. This idea was dropped when the scientists concluded that Skylab would merely be blown into more pieces scattered over a wider area, increasing rather than reducing the danger of damage on earth.

While most Americans neither mourned nor feared Skylab's menacing death, some saw in it yet another in a series of examples of technology outracing man's means of control. A sequence of human and mechanical failures never envisioned by its builders had nearly caused the meltdown of a nuclear reactor at Pennsylvania's Three Mile Island. The mysterious cracks emerging in engine mountings of the DC-10 jumbo jets had led to the grounding of the fleet and America's most tragic air disaster. Now a giant spacecraft, crippled at birth six years ago, is plunging toward a premature end which its creators have no way to prevent. qed

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