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Odp: [gizmodo.com] This Is The Woman Who Replaced Skylab's Destroyed Sunshield
« Odpowiedź #15 dnia: Lipiec 11, 2019, 08:20 »
'Stronger Than Required': Remembering Skylab's End, 40 Years On
By Ben Evans, on June 23rd, 2019 [AS]


One of the final views of Skylab in orbit, as seen directly by human eyes, during the departure of the third crew in February 1974. The station, which began its slow descent back to Earth 40 years ago, this summer, was the largest single object ever launched into space. Photo Credit: NASA

Forty years ago, this summer, America’s first space station, Skylab, breathed its last and commenced a slow descent back to Earth, eventually to burn up in the atmosphere. The vast complex—a converted Saturn V S-IVB third stage, which remains the largest and most massive single object ever launched into orbit on a single booster—had been launched in May 1973, but had endured near-calamity from the start: a troubled ascent had seen its micrometeoroid shield torn away, one solar array ripped off and another clogged with debris.

Once in space, the sterling efforts of three astronaut crews over the next nine months had brought Skylab back to life, repaired it and achieved spectacular scientific results. Hundreds of hours of solar and astronomical observations were made, together with dozens of Earth resources studies and a vast corpus of biomedical data aided our understanding of how the human body functions in space over long periods of time.



Launched in May 1973 atop the final Saturn V, the mission of Skylab almost ended before it had even begun. Photo Credit: NASA

But in the five years after the last crew departed Skylab in February 1974 and the old station’s eventual demise in July 1979, it was virtually abandoned. Its atmosphere was remotely vented, most of its systems were shut down and it was established in a gravity-gradient stabilized attitude, still capable of responding to telemetry commands, but with a troublesome control moment gyroscope and erratic coolant loops there seemed little likelihood that Skylab would again be occupied.

As the decade wore on, the sole chance of saving the station was with the shuttle, which was targeted to undertake its maiden voyage in 1979. Solar activity and its effect upon the upper atmosphere assured many NASA managers that Skylab could endure until the early 1980s and plans were set in motion for a potential shuttle reboost. In September 1977, the space agency initiated a two-year program to build hardware and Martin Marietta was contracted to study the feasibility of fabricating a boxy Teleoperater Retrieval System (TRS), to be deployed by an early shuttle crew to remotely dock and either reboost Skylab or cause the station to deorbit safely over an uninhabited stretch of ocean. Delivery of the $26 million TRS was slated for August 1979, with launch targeted for September, on a mission which included veteran astronauts Fred Haise and Jack Lousma.

Years later, Lousma recalled what would have been a five-day flight. He and Haise would have maintained a position about 1,000 feet (300 meters) from Skylab, after which Lousma would have deployed the TRS with the shuttle’s robotic arm and maneuvered it “like a radio-controlled airplane” to dock at the station. “The mission had never been planned to begin with, so the shuttles didn’t have rendezvous radar,” he told the NASA oral historian. “Fred got busy and started getting that implemented and also developing rendezvous procedures. I worked with Martin Marietta [as] the lead on the development [of the TRS].” In many minds, however, the mission was a waste of time and money, with even then-NASA Administrator Robert Frosch considering the chances of pulling it off as only 50/50.



In March 1978, a “pool” of crew members were announced for the first four Orbital Flight Tests (OFTs) of the shuttle. Among them were Jack Lousma (third from left) and Fred Haise (fourth from left), who might in an alternate history have flown the salvage mission to Skylab. Photo Credit: NASA

What really spelled doom for Skylab in the summer of 1979 was a marked increase in solar activity and its effect upon Earth’s atmosphere. Early calculations predicted that increased atmospheric density would make the station’s orbit susceptible to drag, dropping by around 18 miles (30 km) in altitude by 1980, and faster in the years thereafter, before finally burning up around March 1983. However, as the next solar maximum period neared, NASA was cautioned that the Sun was more active than anticipated, with particularly intense sunspot activity.

Even if the mission to save Skylab did go ahead, it was a risky endeavor. “We knew that Skylab wasn’t just sitting there motionless, waiting to be docked with, but it was actually augering through the sky with a motion that made the nose of it wobble in a circle,” Lousma reflected later. “When we designed the [TRS] booster package, it had to be capable of being flown so it could match that wobble of the docking port around a centerline. I had to fly that booster over there and match the circular motion and have enough power in the control system to make sure that could be done. We simulated [the] known wobble of the Skylab and made sure we could get to that, then we added to it and made a bigger wobble, so we could size the control system. That was part of the development.”



Two years later than planned, the Space Shuttle program got underway in April 1981. It was sadly too late, however, to salvage Skylab. Photo Credit: NASA

In the meantime, in February 1978, NASA made an initial contact with Skylab via the Bermuda tracking station and gradually, system by system, the aging hulk was brought back to life. However, with the shuttle’s maiden voyage planned for no sooner than late 1979, the chances of saving Skylab became increasingly remote. In December 1978, two separate test-stand failures of the Space Shuttle Main Engines (SSMEs) hammered the final nail into the coffin, delaying the first flight of the reusable orbiter until at least 1980. At about the same time, the North American Aerial Defense Command (NORAD) predicted the Skylab would deorbit in July or August 1979.

On 19 December, it was announced that NASA would henceforth focus its energies upon ensuring that Skylab could execute a controlled re-entry, without causing injuries or damage on the ground. Population density maps made this a troublesome effort, with a one-in-152 chance that someone might be hit by falling debris. The loss of the Soviet Union’s nuclear-powered Cosmos 954 satellite over Canada in January 1978 had upped the political stakes to avoid a disastrous re-entry and in January 1979 Skylab was placed into a solar-inertial, high-drag attitude.


<a href="http://www.youtube.com/watch?v=r6HXRHD4K5k" target="_blank">http://www.youtube.com/watch?v=r6HXRHD4K5k</a>
https://www.youtube.com/watch?v=r6HXRHD4K5k
British ITN News coverage of Skylab’s final descent. Video Credit: ITN/YouTube

During re-entry, and particularly during the so-called “terminal phase of decay”, at an altitude of around 77 miles (125 km), its stabilizing control moment gyros would be switched off. This would cause Skylab to tumble and the known lower drag effects associated with a tumbling configuration would result in a more predictable re-entry location and impact footprint. Other minor adjustments could also be made to its attitude to slightly increase or decrease atmospheric drag effects and thus lengthen or shorten the re-entry, but independent studies predicted that several large pieces of Skylab would probably survive the passage through the atmosphere.

The impact date, which was steadily refined by mid-June 1979 to sometime between 7-25 July, was expected to create a debris footprint 4,000 miles (6,400 km) long and 100 miles (160 km) wide. Finally, as July dawned, it was decided that the station would indeed be placed into an end-over-end tumbling motion during re-entry, thereby offering a more accurate prediction of its impact point. NORAD anticipated impact on the 12th and as controllers watched and listened, Skylab’s six years in orbit finally came to an end.



Artist’s concept of the shuttle rendezvous with Skylab and the engines of the Teleoperator Retrieval System (TRS) either reboosting the old station or enabling it to deorbit safely. As circumstances transpired, the Sun and the expansion of Earth’s atmosphere, together with delays to the shuttle program, solved the problem. Image Credit: NASA

In the official Skylab Reactivation Mission Report—published by NASA in March 1980—the majority of the break-up occurred between the altitudes of 37-60 miles (60-95 km): in sequence, the sole remaining solar panel was torn away by steadily increasing aerodynamic forces, after which the Apollo Telescope Mount (ATM) and the main part of Skylab were separated and the solar observatory’s windmill of arrays came apart. Final disintegration most likely occurred some 37 miles (60 km) above Earth. One of the earliest visual sightings was from an airline pilot, flying along Australia’s west coast, who reported an intense fireworks show, as multiple streaks of debris snaked across the sky.

“The actual vehicle was stronger than the specs required,” wrote David Hitt, Owen Garriott and Joe Kerwin in their seminal work on Skylab, Homesteading Space. “It held together longer than was calculated, breaking up over the Indian Ocean. Most of the debris fell harmlessly into the water, but some chunks fell in Western Australia, along a line from south to northeast of Perth.” It was a sad end for a program which had for a few years in the early-mid 1970s placed the United States ahead of the Soviet Union in terms of long-duration spaceflight; with its three crews having logged 28 days, 59 days and 84 days in orbit.


Source: https://www.americaspace.com/2019/06/23/stronger-than-required-remembering-skylabs-end-40-years-on/

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Odp: [gizmodo.com] This Is The Woman Who Replaced Skylab's Destroyed Sunshield
« Odpowiedź #16 dnia: Lipiec 11, 2019, 23:27 »
The Day Skylab Crashed to Earth: Facts About the First U.S. Space Station’s Re-Entry
The world celebrated, feared and commercialized the spectacular return of America's first space station.
JUL 11, 2012  ELIZABETH HANES [history.com]

1. Skylab was made to go up but not to come back down.

The space station known as Skylab was designed as an orbiting workshop for research on scientific matters, such as the effects of prolonged weightlessness on the human body. Because the project represented the next step toward wider space exploration, NASA threw itself into successfully putting Skylab in orbit. Unfortunately, the agency spent far less time and energy planning how to gracefully bring the space station back to Earth at the end of its mission. Even though Skylab was devised for just a nine-year lifespan, NASA failed to build in any control or navigation mechanisms to return the orbiter to terra firma. Doing so would have “cost too much,” administrator Robert Frosch said at the time. This lack of preparation presented a problem in late 1978, when NASA engineers discovered the station’s orbit was decaying rapidly. Skylab had become a 77-ton loose cannon. As word spread of the impending uncontrolled crash of the space station, Congress and the public demanded to know how NASA intended to avoid human casualties from the potential disaster. NASA responded with a plan to rehabilitate the laboratory-in-the-sky. The agency would use a new tool in development—the space shuttle—to boost Skylab into a higher orbit, thereby extending the lab’s operational life by about five years. After that, the station would simply continue to orbit as a shell, like the millions of tons of floating detritus now known as space junk. Funding and other snafus delayed the shuttle project, however, so NASA had to come up with a new plan. On July 11, 1979, with Skylab rapidly descending from orbit, engineers fired the station’s booster rockets, sending it into a tumble they hoped would bring it down in the Indian Ocean. They were close. While large chunks did go into the ocean, parts of the space station also littered populated areas of western Australia. Fortunately, no one was injured.

2. In June 1979, as the crash approached, Skylab-inspired parties and products were all the rage in the United States.

The imminent crash of Skylab midway through 1979 coincided with Americans’ declining confidence in their government. The stagnant economy and a second oil crisis dropped Congress’ approval rating to just 19 percent that year. Perhaps it’s no surprise, then, that many people took an irreverent view of the demise of Skylab, a government project. The Associated Press reported several instances of “Skylab parties” occurring across the United States. In St. Louis, Missouri, the “Skylab Watchers and Gourmet Diners Society” announced plans to view Skylab’s last orbit during a garden gathering at which “hard hats or similar protective headgear” were required. The Charlotte, North Carolina, News-Observer reported that a local hotel designated itself an “official Skylab crash zone (complete with painted target)” and was holding a poolside disco party. Mocking NASA’s inability to say precisely where Skylab would land, entrepreneurs across the country sold T-shirts emblazoned with large bullseyes. Another enterprising individual took a different tack and sold cans of “Skylab repellent.”

3. In Europe and Asia, fear of Skylab’s re-entry prompted unusual safety measures.

While Americans used Skylab’s looming demise as an excuse to party in June 1979, people in other countries didn’t take things quite so lightly. Initially, NASA could not specify when or where Skylab would come down, though the agency mapped out a potential debris field that spanned about 7,400 kilometers across the Indian Ocean and Australia. Even those who lived outside the projected debris footprint were nervous, however. The unexpected fiery crash in January 1978 of a Soviet satellite in northern Canada had scattered enriched uranium across a wide swath of grassland, and people around the globe feared a similar outcome from the Skylab impact—even though the space station contained no radioactive components. Few people felt reassured by NASA’s statement that the risk of human injury from the event was just “one in 152.” After NASA pinpointed the re-entry date as July 11, Scotland’s Glasgow Herald reported, “Worried holidaymakers in Devon [England] are taking no chances—they plan to sit out the morning in an old smuggler’s cave.” In Brussels, authorities planned to sound as many as 1,250 air raid-type sirens in the event that Skylab rained wreckage across the bucolic Belgian countryside.

4. An Australian youth profited handsomely from the Skylab crash, thanks to an American newspaper.

Beginning in June of 1979, as Skylab’s re-entry approached, many American newspapers jokingly proposed “Skylab insurance,” which would pay subscribers for death or injury caused by flying orbiter fragments. The San Francisco Examiner went one step further, offering a $10,000 prize to the first person to deliver a piece of Skylab debris to its office within 72 hours of the crash. Knowing the orbiter wasn’t coming down anywhere near the continental United States, the newspaper felt it was making a safe bet. It didn’t count on news of the bounty traveling all the way to Australia. There, 17-year-old Stan Thornton of tiny Esperance awoke to the commotion when Skylab broke apart in the atmosphere and pelted his house with space station fragments. Thinking quickly, he grabbed a few charred bits of material from his yard, hopped on a plane without so much as a passport or suitcase and made it to the Examiner’s office before the deadline. The newspaper good-naturedly paid out the award.

5. You won’t find the biggest and best pieces of Skylab wreckage in the United States. For that, head to the outback.

Those who remember the Space Shuttle Challenger tragedy of 1986 recall how diligently NASA searched for pieces of the vehicle and tried to ensure none were taken as “souvenirs.” More recently, when a notebook containing the handwritten calculations of Apollo 13’s James Lovell went up for auction, NASA stepped in to assert ownership of the item before reversing its decision and allowing Lovell to sell it. So it may seem odd that very few large pieces of Skylab debris reside in museums in the United States. Instead, space memorabilia enthusiasts must travel to the far-flung reaches of southwestern Australia, where several museums contain pieces of the orbiting space laboratory. The Balladonia museum houses a pair of large pieces of sheet metal from the orbiter. One is emblazoned with “SKYLAB” in red letters, while the other piece is labeled “Airlock/Danger.” The Esperance, Australia, museum features two chunks of a Skylab oxygen tank; the smaller one was dug up by a rancher in 1990.

6. It’s possible to own a piece of Skylab debris today.

Although today NASA claims any fragment of Skylab is the property of the United States, the agency didn’t enforce ownership at the time the space station crash-landed. In fact, NASA officials at Marshall Space Flight Center examined a number of specimens provided by the Australians who discovered them, mounted the items on plaques attesting to their authenticity and returned them to their finders. Newspaper accounts of the day noted that the United States could, under international treaties, claim the debris, but chose to adopt a finders-keepers approach instead. Many Australian prospectors who uncovered Skylab artifacts never reported the finds to authorities after tales of confiscated booty made the rounds. Because the orbiter almost completely burned up on re-entry, the majority of its remnants consist of very small shards. A popular method of capitalizing commercially on the crash at the time seems to have been encasing these items in Lucite for preservation and then selling them. These and other items, such as purported Skylab toothpaste and canned meals, can be purchased at various online auction sites.

Source: https://www.history.com/news/the-day-skylab-crashed-to-earth-facts-about-the-first-u-s-space-stations-re-entry

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Odp: [gizmodo.com] This Is The Woman Who Replaced Skylab's Destroyed Sunshield
« Odpowiedź #17 dnia: Lipiec 11, 2019, 23:27 »
The Day Skylab Crashed to Earth
Dave| Jul 7th, 2017 [davidreneke.com]


Skylab floats above Earth in February 1974. (NASA)

The space station known as Skylab was designed as an orbiting workshop for research on scientific matters, such as the effects of prolonged weightlessness on the human body. It was successful.

Because the project represented the next step toward wider space exploration, NASA threw itself into successfully putting Skylab in orbit. Unfortunately, the agency spent far less time and energy planning how to gracefully bring the space station back to Earth at the end of its mission.  This week marks 38 years since Skylab fell, on 11 July 1979. Here’s how it all unfolded…

Skylab was launched by NASA in 1973, and was manned by teams of astronauts as it orbited the earth. It collected vast amounts of data and images before being abandoned in space in 1974.

In 1979, NASA realised that Skylab was starting to break up and would re-enter the earth atmosphere, but they were unable to control Skylab’s path, nor could they predict exactly where the pieces might land.



The majority of the spacecraft burnt up in the atmosphere but parts of it fell in Western Australia, like this one picked up by a local resident.

The imminent crash of Skylab midway through 1979 coincided with Americans’ declining confidence in their government. The stagnant economy and a second oil crisis dropped Congress’ approval rating to just 19 percent that year. Perhaps it’s no surprise, then, that many people took an irreverent view of the demise of Skylab, a government project. The Associated Press reported several instances of “Skylab parties” occurring across the United States.

1. In St. Louis, Missouri, the “Skylab Watchers and Gourmet Diners Society” announced plans to view Skylab’s last orbit during a garden gathering at which “hard hats or similar protective headgear” were required. The Charlotte, North Carolina, News-Observer reported that a local hotel designated itself an “official Skylab crash zone (complete with painted target)” and was holding a poolside disco party. Mocking NASA’s inability to say precisely where Skylab would land, entrepreneurs across the country sold T-shirts emblazoned with large bullseyes. Another enterprising individual took a different tack and sold cans of “Skylab repellent.”

2. In Europe and Asia, fear of Skylab’s re-entry prompted unusual safety measures.
While Americans used Skylab’s looming demise as an excuse to party in June 1979, people in other countries didn’t take things quite so lightly. Initially, NASA could not specify when or where Skylab would come down, though the agency mapped out a potential debris field that spanned about 7,400 kilometers across the Indian Ocean and Australia. Even those who lived outside the projected debris footprint were nervous, however.

The unexpected fiery crash in January 1978 of a Soviet satellite in northern Canada had scattered enriched uranium across a wide swath of grassland, and people around the globe feared a similar outcome from the Skylab impact—even though the space station contained no radioactive components. Few people felt reassured by NASA’s statement that the risk of human injury from the event was just “one in 152.” After NASA pinpointed the re-entry date as July 11, Scotland’s Glasgow Herald reported, “Worried holidaymakers in Devon [England] are taking no chances—they plan to sit out the morning in an old smuggler’s cave.” In Brussels, authorities planned to sound as many as 1,250 air raid-type sirens in the event that Skylab rained wreckage across the bucolic Belgian countryside.

3. An Australian youth profited handsomely from the Skylab crash, thanks to an American newspaper.
Beginning in June of 1979, as Skylab’s re-entry approached, many American newspapers jokingly proposed “Skylab insurance,” which would pay subscribers for death or injury caused by flying orbiter fragments. The San Francisco Examiner went one step further, offering a $10,000 prize to the first person to deliver a piece of Skylab debris to its office within 72 hours of the crash. Knowing the orbiter wasn’t coming down anywhere near the continental United States, the newspaper felt it was making a safe bet.

It didn’t count on news of the bounty traveling all the way to Australia. There, 17-year-old Stan Thornton of tiny Esperance awoke to the commotion when Skylab broke apart in the atmosphere and pelted his house with space station fragments. Thinking quickly, he grabbed a few charred bits of material from his yard, hopped on a plane without so much as a passport or suitcase and made it to the Examiner’s office before the deadline. The newspaper good-naturedly paid out the award.

4. You won’t find the biggest and best pieces of Skylab wreckage in the United States. For that, head to the outback.
Those who remember the Space Shuttle Challenger tragedy of 1986 recall how diligently NASA searched for pieces of the vehicle and tried to ensure none were taken as “souvenirs.” More recently, when a notebook containing the handwritten calculations of Apollo 13′s James Lovell went up for auction, NASA stepped in to assert ownership of the item before reversing its decision and allowing Lovell to sell it. So it may seem odd that very few large pieces of Skylab debris reside in museums in the United States.

Instead, space memorabilia enthusiasts must travel to the far-flung reaches of southwestern Australia, where several museums contain pieces of the orbiting space laboratory. The Balladonia museum houses a pair of large pieces of sheet metal from the orbiter. One is emblazoned with “SKYLAB” in red letters, while the other piece is labeled “Airlock/Danger.” The Esperance, Australia, museum features two chunks of a Skylab oxygen tank; the smaller one was dug up by a rancher in 1990.

5. It’s possible to own a piece of Skylab debris today.
Although today NASA claims any fragment of Skylab is the property of the United States, the agency didn’t enforce ownership at the time the space station crash-landed. In fact, NASA officials at Marshall Space Flight Center examined a number of specimens provided by the Australians who discovered them, mounted the items on plaques attesting to their authenticity and returned them to their finders. Newspaper accounts of the day noted that the United States could, under international treaties, claim the debris, but chose to adopt a finders-keepers approach instead.

Many Australian prospectors who uncovered Skylab artifacts never reported the finds to authorities after tales of confiscated booty made the rounds. Because the orbiter almost completely burned up on re-entry, the majority of its remnants consist of very small shards. A popular method of capitalizing commercially on the crash at the time seems to have been encasing these items in Lucite for preservation and then selling them. These and other items, such as purported Skylab toothpaste and canned meals, can be purchased at various online auction sites.
 

Source: History
Source: https://www.davidreneke.com/the-day-skylab-crashed-to-earth/

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Odp: [gizmodo.com] This Is The Woman Who Replaced Skylab's Destroyed Sunshield
« Odpowiedź #18 dnia: Lipiec 11, 2019, 23:59 »
Skylab Debris Hits Australian Desert; No Harm Reported

President Sends a Note of Apology--Craft Was Shifted for Re-entry
By RICHARD D. LYONS [movies2.nytimes.com]

Special to THE NEW YORK TIMES


Image Provided by UMI

Washington, July 11--The Skylab space station, at 77 tons the largest object ever orbited, flashed through the atmosphere and disintegrated in a blaze of fireworks over the Indian Ocean today, showering tons of debris across the Great Australian Desert, one of the world's most remote places.

Officials of the National Aeronautics and Space Administration estimated tonight that the area of re-entry into the earth's atmosphere began over the north Atlantic and that disintegration began over Ascension Island in the south Atlantic.

Many accounts of sighting of debris have filtered from the sparsely populated desert region, but there have been no reports of either injury or property damage. Should either occur, the United States is bound by treaty to indemnify those hurt.


Carter Sends Apology

President Carter sent the Australians a message of apology and proferred assistance, saying:

"I was concerned to learn that fragments of Skylab may have landed in Australia. I am relieved to hear your Government's preliminary assessment that no injuries have resulted. Nevertheless, I have instructed the Department of State to be in touch with your Government immediately and to offer any assistance that you may need."

The threat that the disintegrating space station could rain havoc over a wide area had captured attention around the world in recent weeks as space agency controllers tried to predict and control when and where it would fall.

In making its 34,981st and final orbit of the earth, Skylab provided some anxious moments for space officials who had sought to steer it away from populous areas.


Debris Showered on Desert

Skylab re-entered the atmosphere several thousand miles farther down its orbital track than had been expected, and sent flaming debris onto the barren desert of Western Australia and, presumably, into the sea off southwestern Australia. Earlier, it had been expected to land in the ocean.

A decision to maneuver the craft as it moved closer to re-entry enabled it to fly safely over southern Canada and Maine, but may have been responsible for its Australia landing.

"We had a tougher bird than expected," said the Skylab project director, Richard G. Smith, several hours after re-entry had occurred at 12:37 P.M. Eastern daylight time. "We're glad it's down, but we would have liked to have seen it never sighted over Australia."

The decision on re-entry may be questioned in the days ahead. It involved a command to the spacecraft six hours before re-entry that put it into a sort of wobble, which was designed to extend its re-entry track by about 5,000 miles and 30 minutes.

The maneuver virtually assured that no debris would land on Canada and the northern United States, as had been feared late last night, but re-entry was prolonged so that chunks did shower down near Australia.

On the final pass shortly before noon, Skylab sped eastward over Portland, Ore., flew in an arc across the continent, descended over Maine and Nova Scotia, re-entered the atmosphere at 11:44 A.M., went farther down its track over the south Atlantic, and then started breaking up over Ascension Island at 12:11 A.M.


F.A.A. Closes Airspace

While Skylab was on this final pass, the Federal Aviation Administration closed a 150- mile-wide path of airspace east of Kennebunkport, Me., to minimize the possibility that debris might hit an aircraft. It later proved that the precautionary measure was unnecessary.

"We're in the last hour of the descent of Skylab," said the flight director, Charles Harlan, at the Johnson Space Center in Houston, just before disintegration.

First evidence that friction was heating up the satellite's surface--temperatures eventually reached several thousand degrees--came from the South Atlantic when the Ascension tracking station reported that telemetry data from the spacecraft were "becoming garbled and intermittent."

"The solar panels folded like a little duck's wings," said Bob Kapustka, a Skylab engineer at NASA's Marshall Space Flight Center in Huntsville, Ala.


Uneasiness at Headquarters

As the satellite headed beyond Ascension Island, around the Cape of Good Hope and into the Indian Ocean, a general uneasiness settled over the Skylab situation room at NASA headquarters across from the National Air and Space Museum along Independence Avenue in Washington.

Though not articulated, the fear was that through some gross miscalculation the spacecraft would continue to fly past Australia, over the Pacific and then re-enter somewhere near Vancouver Island in the Pacific Northwest.

To complicate the problem, while flying over the western regions of the Indian Ocean, Skylab was out of reach of civilian tracking stations, although as it neared Australia it was picked up by the radars of the secret spy satellite ground station at Pine Gap near the center of the country.

Then at 12:42 P.M., Eastern daylight time, officials of NASA announced that the easternmost edge of the debris footprint had landed at about 43 degrees south latitude and 106 east longitude, about 750 miles southwest of Perth on the west coast of Australia.


Estimate of Re-entry Point

Almost six hours later NASA officials set the final break-up point more than 1,000 miles farther east, about 31.8 degrees south latitude and 124.4 degrees east longitude.

"Entering debris believed to have been the heavier pieces of Skylab was sighted over the area of Western Australia," said a NASA announcement late this afternoon, adding: "No reports of accident or injury have been received.

If true, the larger pieces of the expected 26 tons of debris would then have fallen in the desert, an outback area largely inhabited by aborigines.

According to previous calculations by the space agency, the pieces, of which at least 500 would have weighed at least a pound, would land along a "footprint" about 4,000 miles long and 100 miles wide.


Predictions on Disintegration

But according to prior estimate, the largest pieces would land first on the easternmost end of the landing site because they had the greatest weight and thus the greatest momentum, at about 260 miles per hour. By contrast, the smaller pieces had been calculated to enter at a speed of perhaps 30 miles per hour.

The later calculations would have a footprint extending hundreds, perhaps even thousands of miles over the Australian continent.

Injury or property damage, in the event that it did happen, also would open to question the early-morning decision to wobble the spacecraft deliberately.

Mr. Smith said the decision was made about 3 A.M. after consultations with a group of experts, including Dr. Robert A. Frosch, the administrator of NASA.

"We made the decision on the basis of all the information we had, the best analysis we had, and I'd make that same decision again based on absolutely the same information," Mr. Smith said.

Noting that, "apparently, there has been some debris overfly of Australia," Mr. Smith conceded that a margin of error had crept into the calculations because of too little information being fed into the forecast computers at the start of the final orbit.

"We have been saying for weeks that we have an uncertainty around the point of predicted re-entry that is fairly large and this illustrates the point," Mr. Smith said. "The best information we had, the best information NORAD, everybody had predicted that it would come down before Australia." NORAD is the North American Air Defense Command, which supervises the tracking.

But for the wobble or tumble maneuver being made, Mr. Smith told newsmen later, there was a possibility that some debris might have struck North America.


'Worst-Case Situation'

"It was a worst-case situation," he said. "We were trying to prevent the creation of a worse condition than we started with."

For many weeks, NASA scientists had conducted a series of intricate calculations aimed at providing Skylab controllers with estimates of the numbers of people living beneath any given track of the vehicle. The final orbit was one of the best, since it was almost totally over ocean.

The final plunge thus ends the $2.6-billion Skylab project that began over a decade ago. The huge cylindrical space station was placed in orbit in 1973, and was visited by three parties of astronauts who carried out long scientific and medical experiments. The longest of the three-man groups stayed aloft for 84 days.

At present, NASA has no firm plans for the development of another space station like Skylab. Operations will center, starting next year, on the space shuttle, which blasts into orbit like a spacecraft and lands like an airplane.


Copyright 2010 The New York Times Company

Source: http://movies2.nytimes.com/learning/general/onthisday/big/0711.html#article

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« Odpowiedź #19 dnia: Lipiec 12, 2019, 07:51 »
40 Years Ago: Skylab Reenters Earth’s Atmosphere
July 11, 2019 [NASA]

                                                   
                                                   Skylab Program patch

                         
                         Composite of the three three-person crews who completed long-duration missions aboard the space station

Skylab was America’s first space station and first crewed research laboratory in space. The complex consisted of four major components: the Orbital Workshop (OWS), the Airlock Module (AM), the Multiple Docking Adapter (MDA), and the Apollo Telescope Mount (ATM). The Apollo Command and Service Module transported crews to and from Skylab and remained attached to the station throughout a crew’s occupancy. The OWS, converted from the upper stage of a Saturn rocket, served as the main working, living and sleeping compartment for the crews, and contained exercise equipment, a galley, and many of the scientific experiments, in particular for the life sciences studies. The AM enabled astronauts to conduct spacewalks, while the MDA included a prime and backup docking port for the Apollo spacecraft and housed the Earth Resources Experiment Package. The ATM contained telescopes for solar observations and four solar arrays for additional power. Once in orbit, the complex weighed 170,000 pounds, by far the heaviest spacecraft to date. An unprecedented research laboratory in space, Skylab contained scientific equipment to conduct research in a variety of disciplines. Astronauts aboard the station conducted 270 experiments in biomedical and life sciences, Earth observations, solar astronomy and materials processing. Among the most important were investigations on the astronauts’ physiological responses to long-duration space flight.


Illustration of the Skylab space station and its components as it would have appeared without the damage incurred at launch

On May 14, 1973, the final Saturn V rocket thundered off Launch Pad 39A at Kennedy Space Center to lift the Skylab space station into orbit. About 63 seconds into the mission, telemetry indicated premature deployment of the micrometeoroid shield, designed to protect the station from debris and also act as a thermal blanket. Debris from the torn shield jammed one of the station’s large solar arrays and aerodynamic forces tore the other panel completely off. Skylab made it to orbit, but it was underpowered and rapidly overheating.  Mission managers delayed the launch of the first crew by 10 days as engineers devised ways to save the station. Once on orbit, the Skylab-2 crew deployed a sunshade to cool the station and eventually free the stuck solar panel, saving the program. 


Launch of the Skylab space station on May 14, 1973. It was the final launch of a Saturn V rocket.

In all, three successive three-person crews spent 28, 59 and 84 days, respectively, aboard the space station, and as a platform for conducting scientific research Skylab proved its value.  The biomedical investigations carried out by the nine Skylab crewmembers provided our first glimpse into the effects of long-duration spaceflight on the human body and how to prevent some of the more deleterious effects. The ATM solar telescopes took more than 170,000 images for astronomers, while Earth scientists received 46,000 photographs. In nearly every science discipline, the astronauts exceeded the planned number of investigations. Of significant importance, having humans available for unplanned situations proved highly valuable, from the repair of the space station after its damage at launch, to being able to respond to unexpected events to increase the science return from the mission including observing new solar flares and a comet making a rare passage through the inner solar system. Managers, flight planners, and engineers used the Skylab experience to learn about how to live aboard and operate a long-duration crewed platform in space, passing on lessons learned to later programs like Shuttle-Mir and the International Space Station.


Skylab as it appeared to the final crew upon its departure.

Before leaving the station on Feb. 8, 1974, the Skylab-4 crew boosted it into a higher 269-by-283-mile orbit, in the hope that Skylab would remain in space until 1983. By then, the Space Shuttle would be flying and NASA hoped that astronauts could attach a rocket to the station to either boost it to a higher orbit or safely deorbit it over the Pacific Ocean. But delays in the Shuttle program and higher than expected solar activity resulting in increased atmospheric drag on the station ultimately thwarted those plans. It became apparent that Skylab would reenter in mid-1979, forcing NASA to devise plans to control its entry point as much as possible by adjusting the station’s attitude to adjust atmospheric drag.


Illustration of a proposed Skylab boost mission by the Space Shuttle.


Ground track of Skylab of its final orbits and the debris footprint in southwest Australia.

On July 11, 1979, during its 34,981st orbit around the Earth, engineers in Mission Control at the Johnson Space Center in Houston sent the final command to Skylab to turn off its control moment gyros, sending it into a slow tumble. This was the best that flight controllers could do to ensure that Skylab would not reenter over a populated area such as North America. They expected that it would begin its breakup over the southern tip of Africa and fall into the Indian Ocean. As it happened, the breakup occurred slightly later and while the majority of the debris that survived reentry did fall into the Indian Ocean, some pieces fell over sparsely populated areas of southern Western Australia. A museum in Esperance houses some of the recovered debris. Skylab Flight Director Charles S. Harlan said in a news conference after the event, “The surprise is over. No more suspense. Skylab is on the planet Earth.”


Mission Control in Houston during the Skylab reentry.


Managers and flight controllers monitor Skylab’s reentry.

The backup Skylab OWS is displayed at the Smithsonian’s National Air and Space Museum in Washington, DC, while the Skylab training module is displayed at Space Center Houston.


The backup Skylab workshop on display at the Smithsonian’s National Air and Space Museum.


View inside the Skylab trainer on display at Space Center Houston. Credits: SCH, NASM.

John Uri
NASA Johnson Space Center

Source: https://www.nasa.gov/feature/40-years-ago-skylab-reenters-earth-s-atmosphere

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« Odpowiedź #20 dnia: Lipiec 12, 2019, 08:33 »
A space station crash landed over Esperance 40 years ago, setting in motion unusual events
ABC Esperance By Tom Joyner and Isabel Moussalli, Updated about an hour ago


The oxygen tank of the Skylab space station that fell over WA in 1979. PHOTO: The oxygen tank Pauline and Geoff Grewar found in 1993 hundreds of kilometres from Esperance. (Supplied: Geoff Grewar)

One morning in 1993, Geoff Grewar and his wife Pauline were flying a small aircraft over their farm property in Western Australia when they spotted a gleaming object in the scrub below.

At first, it looked like someone had parked their car among the bushes, but on closer inspection it resembled something more of an enormous capsule big enough for their grandkids to fit inside.

Puzzled, the former MP immediately called local authorities who said they wanted it collected with some urgency.

Mr Grewar did not realise it at the time, but the object — an oxygen tank from the unmanned space station Skylab — had until that point remained undisturbed for some 14 years.

The pair had stumbled upon what would be the single largest piece of NASA's ill-fated project that crashed to Earth one winter's night in 1979.

"It was so eerie," Mrs Grewar said.


"To find this oxygen tank that had come out of the sky, in the middle of vast open paddocks."


NASA's Skylab space station as seen from space. PHOTO: NASA's Skylab appeared in a "fiery apparition" over Esperance in the early hours of July 12, 1979. (Supplied: NASA)

'A fiery apparition'

Skylab, a bulky mass of metal and glass, had been launched in 1973 with the aim of providing an intimate view of the universe, and a platform for scientific research and experimentation in space.

But after six years in orbit, it slid off course and began a rapid and somewhat unpredictable descent back to Earth, gaining international media attention along the way.

In the weeks leading up to the crash, American newspapers speculated on where and when it might land.

A NASA official reportedly testified to US Congress there was a one in 152 chance of the plummeting spacecraft injuring someone.

So when it finally disintegrated in a fiery explosion over Esperance in the early hours of July 12, 1979, it caught locals off guard.

"We were just sipping the last of our coffee and we were startled by some sonic booms," said Brendan Freeman, a retired farmer who that night rushed onto his verandah and turned to the sky.



Retired farmer Brendan Freeman with his wife Fran at their home in Esperance, WA. PHOTO: Retired farmer Brendan Freeman had a clear view of Skylab's descent, which he likened to fireworks. (ABC Goldfields: Tom Joyner)

Mr Freeman and a group of others had gathered in anticipation of Skylab's re-entry, while others in Esperance flocked to Wireless Hill, a convenient lookout point in town.

"We watched this fiery apparition rocketing through the sky," he said.


"It was the best fireworks display you would ever see."

An international media storm

Local radio broadcasts had reported that re-entry was expected much earlier in the evening, around 10:30pm, and so most had turned in by the time the burning Skylab did appear in the night sky.

"Nearly half past midnight, bang, bang, bang — six fantastic sonic booms," said Merv Andre, who was the Esperance Shire president at the time.


"The doors rattled, and the wardrobe doors, and the windows."

What came next was a media storm.

In the days following, a party of NASA officials arrived in Western Australia to assess the situation and deal with the fallout.

In a press conference packed with Australian journalists, they fielded questions about what they had known of Skylab's path of descent.

In California, the San Francisco Examiner ran a competition to award $10,000 to the first person to bring a piece of Skylab back to their offices.



Astronaut Edward Gibson performs a space walk on Skylab space station. PHOTO: Astronaut Edward Gibson performs a space walk on the Skylab space station. (Supplied: NASA)

The competition prompted a frenzy among locals to find pieces of debris around the region.

It was ultimately won by an Esperance teenager called Stan Thornton, who made the journey to San Francisco with the financial help of a Perth radio station and Qantas.

There was barely enough time to get him a passport and visa for the trip, the Examiner reported the following day, nor did he have time to pack any clothes.


Littering fine issued to NASA

Before long it seemed that without warning, the small coastal community had been thrust onto the world stage.

An American TV station reportedly interviewed Qantas executives who told them the Skylab saga had done one good thing — it had reminded the world that Australia exists.

A makeshift workshop was set up for locals to bring in small pieces of Skylab for the officials to check for radiation with a Geiger counter.

One of the Shire's rangers at one point handed the NASA team a $400 fine for littering, meant as a tongue-in-cheek gesture.

The agency never paid it.



Two astronauts perform final checks before the first manned Skylab mission. PHOTO: Skylab remained in orbit around Earth for approximately six years in the 1970s. (Supplied: NASA)

Instead, three decades later, a radio broadcaster called Scott Barley from Barstow, California crowdfunded the outstanding penalty among his listeners and hand-delivered a novelty cheque to the Esperance Shire.

Today, the story has entered local folklore.

An enormous sign hangs from the exterior of the local museum in honour of the tale.


'We have used it shamelessly for publicity'

Few who were around four decades ago have ever forgotten the strange events of July 12, 1979, and many have their own story of where they were when it happened.

Some credit a boost to local tourism that has been sustained over the years since to the Skylab incident.

The Esperance Museum holds one of the world's largest collections of Skylab debris, which is on permanent display year-round.



Former Esperance Shire president Merv Andre gives a presentation on Skylab. PHOTO: Merv Andre was president of the Esperance Shire the night Skylab fell out of the sky. (ABC Goldfields: Tom Joyner)

Among its collection is the oxygen tank that Geoff and Pauline Grewar found in 1993, as well as a nitrogen tank and other assorted pieces of insulation and metal.

According to Mr Andre, the most miraculous part of the whole thing was that no one was injured — Skylab veered close to disaster but narrowly avoided it.

"Not a piece hit buildings or animals or people, nothing," Mr Andre said.


"One piece that ripped off the tank came down in the back lawn of a house, and it landed safely on the ground."

A competition run by the Esperance Shire this year saw the winner — a nine-year-old girl called Konii — interview via Skype Edward Gibson, a NASA astronaut who worked on Skylab.

Part of Skylab's legacy is an ongoing fascination with what happened, and why.

This year alone, it has inspired an art installation, a documentary film and a novel.

Most valuably though, said Lynda Horn of the Esperance Museum, Skylab's haphazard descent over WA later contributed to the success of the International Space Station.

"Skylab did put Esperance on the map," she said.


"It's great to have people coming to visit."

Mr Andre agreed.

"We have used it shamelessly for publicity," he said.


"It was a pretty wonderful thing to happen."

Source: https://www.abc.net.au/news/2019-07-12/four-decades-on-from-skylabs-descent-from-space/11249626

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« Odpowiedź #21 dnia: Lipiec 13, 2019, 06:26 »
Cloudbusting: The End of Skylab, 40 Years Later
by Emily Carney | Jun 29, 2019 [space.nss]



This Space Available
By Emily Carney

“It’s better to burn out than to fade away.” – Neil Young, “Hey Hey, My My (Into The Black)”

According to a previous blog post by This Space Available, when a proposed reboost mission carried out via Space Shuttle was ruled out as a possibility, NASA began to prepare for the inevitability that Skylab, in orbit since May 14, 1973, was coming down in mid-1979. Skylab’s operations during this period were dependent on the space station’s Apollo Telescope Mount Digital Computer (ATMDC), which was re-activated in March 1978, over four years after its last three-person crew had vacated. The computer system’s role now was to help control the station during its final months in orbit.

The NASA History book Living and Working in Space: The NASA History of Skylab stated that before the final crew had left in February 1974, they had boosted the station’s orbit: “Before undocking from Skylab, [mission commander] Gerald Carr had fired Apollo’s attitude-control thrusters for three minutes, nudging the cluster 11 kilometers higher, into an orbit of 433 by 455 kilometers [269 by 283 miles].” Following this boost, the ground further ensured Skylab was stably hibernating: “After the crew had returned to earth and the end-of-mission engineering tests were finished, flight controllers vented the atmosphere from the workshop, oriented the cluster in a gravity-gradient-stabilized attitude with the docking adapter pointed away from the earth, and shut down most of its systems.”

Skylab spent over four years in this mode, until it became clear that aerodynamic drag on the station needed to be minimized if it was going to “stay up” much longer. By early 1978, as the Solar Maximum year of 1980 approached, Skylab was predicted as coming down sooner than expected thanks to increased solar activity. Ironically, the very object of Skylab’s studies – the Sun – was aiding in its demise.

Enter the long-dormant ATMDC. The 1987 NASA publication Computers in Spaceflight: The NASA Experience related, “The original Skylab mission lasted 272 days with long unmanned periods. The reactivation mission, flown entirely under computer control, lasted 393 days.” During its human-helmed missions Skylab had flown mostly in solar inertial (SI) mode to ensure the best outcome for its battery of solar experiments, and as previously stated, had hibernated mostly in gravity-gradient mode. However, as Computers in Spaceflight explained, “…Engineers devised two new modes, end-on-velocity-vector (EOVV) and torque equilibrium altitude (TEA). EOVV pointed the narrow end of the lab in the direction of flight, minimizing aerodynamic drag on the vehicle. TEA could control the reentry, using the gravity gradient and gyroscopic torques to counterbalance the aerodynamic torque.”



Skylab 4’s Dr. Ed Gibson shortly after it was announced Skylab had reentered, July 11, 1979. Gibson was observing the reentry from the JSC control center in Houston. Screenshot used with permission from the film Searching For Skylab.

The book Homesteading Space establishes a timeline from the day it was apparent there was a problem (March 20, 1978) to the time Skylab entered EOVV (June 11, 1978), thanks to IBM who were responsible for the equations that reprogrammed the ATMDC. It was hoped that this mode could keep Skylab aloft through 1980. For a short time, the EOVV mode helped to minimize the space station’s downward trend, but in early 1979, Skylab would fall under NORAD’s scrutiny.

According to the Honeysuckle Creek website, “Toward the end of April, NASA Headquarters issued its first forecast of a reentry date calculated from NORAD’s model. On the 25th, when the workshop had fallen to about 320 kilometers [approximately 198 miles in altitude], NORAD estimated a probability of 50% that Skylab would come down by 19 June; there was a 90% chance that it would reenter between 13 June and 1 July. This format was used consistently for the rest of the waiting period, because it was impossible to give a more precise estimate until reentry had virtually begun. NASA and NORAD did exchange information and determined the different ways the two computer models treated data. NORAD made a fairly straightforward extrapolation based on recent observations, while NASA continuously took account of changing atmospheric density and the spacecraft’s drag profile as it came down.”

The website continued that the three-day “Death Watch” for Skylab began on Sunday, July 8, as Charles Harlan’s team in Houston kept a close eye on the station during its last days. With Skylab in TEA mode, it was decided to issue the “tumbling command” when the station was at an altitude of under 80 miles, with hopes it would avoid most landmasses. However, Homesteading Space underscored that the station “held together longer that was calculated, breaking up over the Indian Ocean.”

…And parts of Australia. The Honeysuckle Creek website painted a vivid portrait of the indignities the cluster underwent during its final moments, reporting, “[News bulletins] began 111 kilometers over Ascension Island in the Atlantic when the radar station there spotted the big solar panels begin to tear off as the lifeless hulk spun and twisted out of control. ‘It’s now out of range of all our tracking stations,’ said NASA, ‘The crash line is from Esperance in Western Australia to Cape York in Queensland. The chances of anybody coming to harm are minimal, but people are advised to stay indoors.’” The day was July 11, 1979, with NORAD calculating the impact time as 12:37 p.m. EDT.

Living and Working in Space paints another slightly chaotic scene: “Shortly before 1 p.m., the Washington control center received word that the area southeast of Perth, Australia, had indeed been showered with pieces. Spectacular visual effects were reported and many residents heard sonic booms and whirring noises as the chunks passed overhead in the early morning darkness. Officials waited anxiously for news of injury or property damage, but none came. Skylab was finally down and NASA had managed it without hurting anyone.” To this day, those curious enough to search can probably still find bits of Skylab lodged in parts of Western Australia.

One former Skylab resident observed its final moments with mixed emotions. As Skylab came down after making 34,981 revolutions, many with his presence aboard, Dr. Ed Gibson watched stoically in Houston’s control center. “Oh gosh!” he exclaimed. “I was unhappy we didn’t boost it [via Shuttle] further so we could use it again…I was unhappy about that. But I was happy I could be in the control room and actually watch it reenter.” Despite his feelings, he was careful to emphasize, “I was very proud of our program’s achievements.” Gibson would retire from his post at NASA in 1981, and the next long-duration American space station increment wouldn’t take place until 1995.

Featured image credit: A sign commemorates Skylab’s final orbit from the control center at Houston, Texas’ Johnson Space Center. Screenshot used with permission from the film Searching For Skylab (streaming information located in link).


*****
Emily Carney is a writer, space enthusiast, and creator of the This Space Available space blog, published since 2010. In January 2019, Emily’s This Space Available blog was incorporated into the National Space Society’s blog. The content of Emily’s blog can be accessed via the This Space Available blog category.

Note: The views expressed in This Space Available are those of the author and should not be considered as representing the positions or views of the National Space Society.

Source: https://space.nss.org/cloudbusting-the-end-of-skylab-40-years-later/