Category HOMESTEADING SPACE

Several books could be—and have been—written to summarize all of the scientific experiments performed on Skylab. Almost one hundred different pieces of experiment equipment were manifested for the original launch. Thousands of hours were spent on science. Tens of thousands of Earth obser­vation images were taken as well as over a hundred thousand solar astron­omy images.

The two fields that were Skylab’s greatest scientific legacy, as well as the ones requiring the largest time investments from its crews, were solar astronomy and life sciences in weightlessness. Research performed on Sky­lab would revolutionize both of these fields and would lay the groundwork for all that would come later.

Life Sciences

The Prologue: Early Spaceflight

Skylab was medicine’s first, best chance to unravel the mysteries of weight­lessness. Man’s ability to fly into space and to withstand the effects of being weightless had been matters of controversy since the very beginning of NASA. Opinions were all over the map. Some believed the experience would be pleasant and of no medical significance; the original astronauts were in this group. Others speculated that disruption would occur in many body sys­tems. Balance would go haywire without gravity to guide the inner ear; the heart would weaken; the passage of food “down” the digestive tract would suffer; urination might be impossible; and the isolation would induce a state of sensory deprivation, the “ breakoff phenomenon.” A lot of these hypothe­ses were published in medical journals, promoting the impression that space was dangerous and unknown.

The U. S. Air Force had begun to prepare itself to manage America’s manned space efforts, and this preparation included medical support. It was the unquestioned leader in the field of aerospace medicine with three

times the personnel and four times the budget of its closest competitor, the Navy. A distinguished German physician and physiologist, Hubertus Strug – hold, established in 1950 the first department of Space Medicine, at the U. S. Air Force School of Aviation Medicine. Other German scientists also did research for the Air Force.

NASA’s predecessor organization, the National Advisory Committee for Aeronautics, or naca, had no medical staff or expertise; all of its origi­nal experts were borrowed from the military. To provide medical support to Project Mercury, the Air Force contributed William Douglas, Stanley White, and Charles Berry; the Army, William Augerson; and the Navy, Robert Voas. These men brought with them the military method of qual­ifying humans for the stresses of flight. As aircraft flew faster and higher, pilot tolerance to and protection from acceleration, hypoxia, and disorien­tation had become major problems. The approach to solving them empha­sized testing and monitoring both in laboratories and in flight, an incre­mental increase in human exposure with healthy skilled test pilots, and very close liaison between medicine and engineering.

The academic community’s advice was quite different. It emphasized peer – reviewed scientific experiments by National Institutes of Health or univer­sity scientists and a great deal of animal research before exposing humans. The rationale was that the effects of spaceflight must be characterized and proven safe before people flew. Throughout the 1960s a continuous stream of criticism was heaped upon NASA by scientists: its programs were too ambi­tious, too rushed, not safe. One group insisted that NASA fly forty animals into space before committing to human flight.

Animals were the first to be sent into space. In December 1958 a squir­rel monkey named Old Reliable was launched in the nose cone of a Jupiter missile to an apogee of three hundred miles; it survived the launch, but the nose cone was lost upon reentry. In May 1959 a rhesus and a squirrel mon­key, Able and Baker, made the same trip and survived. Two chimpanzees, Ham and Enos, became the first animals to ride in Project Mercury cap­sules — Ham on a suborbital flight and Enos for two orbits. Both did fine. Mercury’s medical support group believed that these flights, plus the reports from the Soviet Union of a successful six-day Soviet flight of the dog Laika on Sputnik 2 in 1958 (though recent information indicates that Laika’s flight was far less successful that early reports would have had the world believe), showed that weightlessness was survivable, at least for short periods.

But biological scientists wanted still more. Led by Ames Research Cen­ter, they achieved NASA approval and funding for the Biosatellite project, which would launch and study various life forms on dedicated satellites. The first Biosatellite mission failed on launch. The second successfully flew plants and insects into space in September 1967. The third was to fly a ful­ly instrumented monkey, Bonnie, on a thirty-day mission to pave the way for the Skylab program.

Biosatellite 3 launched on 29 June 1969. The spacecraft was built by Gener­al Electric Reentry Systems Division at Philadelphia, weighed 1,550 pounds, and was launched on a Delta into a 240 nautical-mile circular orbit. Reen­try was commanded on the ninth day of the flight, on 7 July (just nine days before Apollo 11 launched to the moon). Bonnie was recovered but died less than half a day later.

Here is a letter on University of California, Los Angeles letterhead, to the editor of Science magazine, dated 14 August 1969. It’s a copy of a copy of the original. At top left someone has written, “This has been submitted to SCI­ENCE for publication although NASA objected to certain portions thereof.” And on the right the person wrote “slayton.”

It’s a lengthy letter. Here are a few excerpts:

The recent flight of Biosatellite iii with a male macaque monkey (Macaca nem – estrina) was the culmination of more than five years’ intense collaborative sci­entific effort. . . . The flight lasted only 8y ofa planned 30 days. . . . The phys­iologic deterioration of the monkey. . . is mainly attributed to the effects of weightlessness. . . .

The monkey was in excellent physical condition at the time oflaunch…. All physiological sensors functioned perfectly throughout the flight and after recov­ery. There were 33 channels of physiological information…. The range of these measurements in different body systems and their detailed character are with­out parallel in any single previous experiment on Earth or in space.

The last sentence had been underlined, and in Deke’s unmistakable hand was the comment, “That’s what killed him.” (Garriott joked that if the surgical preparations the monkey underwent, among the least violative of which included incisor tooth extraction and tail amputation, had been required for potential Skylab astronauts, NASA would have lost nine out of nine crewmembers.)

The letter goes on to describe the monkey’s gradual loss of responsiveness to tests; the drop in body temperature, heart rate, and blood pressure; the emergency reentry, and the death in Hawaii from a sudden heart arrhyth­mia after hours of emergency treatment. Now the investigators sum up:

The well-documented sequence of events leading to collapse in this monkey sug­gest the need for a guarded approach to design of missions for man that might involve extreme effort after a considerable exposure to weightlessness. . . the important findings listed above characterize this mission as highly successful. They also indicate the great value of carefully designed animal experiments… especially where the physiological sensors and required experimental control are difficult or impossible to secure in mannedflight. Sincerely, five scientists.

In the q&a session at a press conference, held 22 October 1969, Dr. W. Ross Adey, the principal investigator, was asked, “Why believe one bad result in a monkey instead of seventeen good ones in astronauts?” He replied that the astronauts didn’t do all that well, really—Dick Gordon never did get the tether attached (on Gemini 11), and he sweated profusely. Then the fol­lowing exchange occurred.

Question: To follow up Bill Hines’s question: might your experiments with this monkey indicate that monkeys are less adapted to spaceflight than men are?

Adey: Well, I think the question of individual susceptibility cannot be ruled out. After all, this is one monkey, and there are seventeen men. And here I would like to take off my hat as an experimenter and put on anoth­er one, as a member of the President’s Science Advisory Committee, which has had a medical group looking into the question of the biomedical foun­dations of manned spaceflight. And their advisory document to the Presi­dent has been released and is in the course of being published. And I would submit that the best considered opinion is that we do not now have the bio­medical basis for going ahead with the very elaborate programs proposed in the way of space platforms and space stations which involve major new engineering developments, and that the biomedical competence—or rather, the body of knowledge, as the report says—and I think I quote it correctly; it says that the necessary biomedical basis does not exist in NASA nor in the scientific community generally, and that it is not realistic to go ahead with the planning of major new space systems and exclude from almost any con­sideration the question of the biomedical capability of man to not merely

survive in space, which has been his requirement to this point, in essence, but to perform at a high level on a continuing basis.”

Kerwin recalled, “Well. That truly threw down the gauntlet to us Skylab types. None of us were thrilled to hear that the Apollo 11 mission had dem­onstrated mere survival. But clearly it was up to us to show that we could perform at a high level—on a continuing basis—while floating around. That we could brush our teeth, go to the bathroom, take spacewalks, yes, even (gasp) do science—just like Bonnie had.

“Chuck Berry’s response to the Biosatellite business was courageous and correct. He publicly and accurately identified the differences between the monkey’s circumstances and ours and judged Skylab to be safe. Given a lot of bedside hovering, of course. He’d put himself on the spot, and when things didn’t go perfectly early on in our mission, some medical pessimism returned.”

Meanwhile, those seventeen astronauts had flown into space for dura­tions that ranged from four and a half hours to fourteen days, and they’d all performed well and recovered quickly from any effects of the flights. There had been changes. There was weight loss, ranging upwards of ten pounds. There was loss of appetite and in some cases motion sickness. There was some muscle weakness after flight. Blood volume decreased, and a few astro­nauts had a tendency to be light-headed immediately after recovery. On one flight (Apollo 15, well after Biosatellite) there were disturbing heartbeat patterns in two crew members. Calcium excretion increased, and there was just a hint that bones might be losing structural strength. These gave rise to questions about the feasibility of long-duration spaceflight. Skylab was the place to answer them.

On Skylab, for the very first time, life sciences were not just along for the ride—they were going to have top priority as a mission goal. And the NASA life sciences people—despite their organizational fragmentation, differenc­es of opinion, and constant criticism from outside—responded to the chal­lenge with a well-planned, ambitious set of experiments.

One group would test the cardiovascular system, studying heart function during exercise and simulated gravity (using lower body negative pressure). Another would be a very careful metabolic balance experiment with exact

measurement of all intake and output combined with pre-and postflight mea­surement of bone loss using gamma ray densitometry, more accurate than the x-rays used in Gemini. Yet another would measure the body’s respons­es to the stress of flight by measuring hormone levels in blood samples col­lected and frozen in flight—and observe whether the trend to a reduction in blood volume and red blood cell mass was continuing. And one would intensively evaluate the vestibular balance system in the inner ear, suspect­ed to be the culprit in space motion sickness. There were cleverly designed “scales” capable of measuring the “weight” (the mass actually) of the astro­nauts, of any food and drink they were supposed to eat but didn’t, and of their feces. There was even a special cap to measure and record brain waves during sleep, looking at duration and depth. The scientist members of the crews got to wear that one.

All these experiments would be carried out during flight, not just before and after, thanks to the ample size and weight of Skylab. But designing them to be carried out successfully was still an enormous challenge. The food sys­tem would have to accommodate the metabolic balance experiment. Feeding the crews was a pretty big part of getting ready for Skylab. Astronauts have to eat, and on this mission they’d have to eat for a long time. So there were a lot of requirements and considerations jostling each other for priority:

1. Learning how to package foods to be consumed in zero gravity.

2. Launching all the food for all three missions aboard the Skylab workshop because the Apollo spacecraft used as the crew’s taxicab wasn’t big enough to hold it. That meant selecting food treated and packaged to have a year-long shelf life in space—not the best setup for tasty meals.

3. Giving the crews food they’d like—making mealtime a positive experience on these long and isolated missions.

4. Keeping them well nourished, which is not the same thing as giving them food they’d like.

5. And last but definitely not least, discovering what happens to nutri­tional needs during long periods in weightless spaceflight. This would be one of the most important medical experiments.

Storage on orbit for up to a year at “pantry” temperatures was the most severe environment yet for space food. It ruled out fresh food, food that required refrigeration—any food you’d throw away at home if it hadn’t been eaten after a month or two. Both weight and spoilage considerations dictat­ed that the food should not be stowed mixed with water. If soup was want­ed, dried soup was stowed, and the water was added just before eating. So a lot of rehydratable food, from orange juice to spaghetti, was on the menu. Adding water doesn’t work for certain foods—for example, bread. The solu­tion here was to irradiate it for preservation, then vacuum-pack it. Unfor­tunately, vacuum-packing sucks most of the air out of bread, making it an unpalatable paste. Bread was not a hit. But the sugar cookies—food system specialist Rita Rapp’s own recipe—were delicious.

Foods that were to be served hot were packed in plastic bags, and the bags packed snugly in little flat round cans. The routine was as follows: open the can, add water to the food through a nozzle, smush it around to mix

the food and water, put it back in the can, put the can in a fitted receptacle in an airline-style tray, and turn on the electric strip heater. An hour or so later, the item would be hot. This system worked well. It was a little time­consuming; one crewman would usually prepare three meals an hour or so ahead of time. And it did generate a lot of trash. Hot coffee was achieved a different way; the crew just added hot water to the instant coffee and shook instead of smushing.

Once the Skylab food system, or galley, was developed, the big question was, how many different kinds of food would be provided, and how much of each? And that’s where the scientists came in. Their working hypothesis was that flying in space was like resting in bed, immobilized by illness or perhaps multiple fractures. You were in “negative metabolic balance.” You lost appetite and lost weight, and muscles not used began to atrophy. It was intuitively obvious that in space many muscles weren’t used much (those used for climbing stairs, for example). The energy needed for normal body activity must therefore decrease, and the need for food would decrease in proportion.

Along came Dr. G. Donald Whedon, an experienced and prestigious researcher, with a diet plan for Skylab. He proposed that all Skylab crewmen consume a diet of 2,400 calories per day, below their Earth-bound needs. The diet would contain precise amounts of calcium, phosphorus, and other electrolytes and specified amounts of protein and fat with very little variance allowed. Some additional carbohydrates—’’empty calories” such as lemon drops—were allowed if the men were still hungry. Menus would be made up with enough variety to provide a six-day cycle, which would then repeat.

The crews would eat this diet for eighteen days both before and after flight. And—here’s the key— both before, during, and after flight, every gram of matter that entered or left their bodies would be weighed and ana­lyzed. Thus, whether the men were gaining or losing calcium from the bones or nitrogen from the muscles would be known with precision. It was a love­ly experiment. But it gave rise to some practical problems.

First was standardizing the diet. The crew violently objected to the assump­tion that all of them would have to consume the same amount of food. Alan Bean weighed 150 pounds and had consumed less than 2,000 calories daily on his Apollo 12 flight. Jack Lousma weighed a fit 195 pounds and ate more than 3,000 calories a day on Earth. There was no way they could both be constrained to 2,400. The second problem was that the 2,400 number had been calculated based on the assumption that during spaceflight metabol­ic demands decreased and so did calorie consumption. This might hap­pen, the crew argued, but it was unproven; and even if it did happen, it was wrong to put the men on the in-flight diet for nearly three weeks before and after flight.

On і March 1971 Deke Slayton wrote a memo stating in part, “We are not raising goose livers, and it is unreasonable and unrealistic to force-feed astro­nauts.” Finally, the investigators agreed to tailor each crewman’s diet to his usual intake. A week-long test using prototype flight food was organized, and the results used to construct the in-flight diets. Instead of merging all nine men into one data set, each one would serve as his own control. Feed­ing the flight diet before launch was retained, however. Sure enough, eight of the nine crewmen lost weight during the eighteen days before launch.

Another problem was, how do you weigh things in weightlessness? It’s true; Justice’s scales are useless in space. The little weights would just float away. But objects in space still have mass—they just don’t have gravity pull­ing that mass against the scales. So Dr. Bill Thornton invented an ingenious device to measure the mass without using gravity. His theory was this: if you attach an object to the free end of a strip of spring steel, clamp the other end, and give the object a push, the steel will oscillate back and forth. And the heavier the object—or rather, the greater its mass—the more slowly will it oscillate. So you have only to attach whatever you want to measure, start it oscillating, and measure the time it takes to complete three back-and-forth movements—the “period” of the spring and mass. Skylab adopted Bill’s principle, and the Air Force built one large device for measuring the mass of the astronauts, and two small ones, for measuring food residue, feces, and other small amounts of substances and small items. Given the oppor­tunity, Dr. Whedon’s team wanted to measure the mass of everything to the greatest accuracy possible:

1. The bags used to capture feces came secured with green tape; the crews were instructed to “weigh” the tape, separately, each time they used a bag.

2. They were then asked to mass measure each used fecal bag “wet” before putting it into a vacuum oven, where it was dried for return to Earth.

3. Both large and small masses were requested to be “weighed” to six significant figures—less than a hundredth of a pound for people, and a thousandth of a gram for food residue. That called for averag­ing many repeated weighings.

Whedon’s team explored several methods for sampling sweat, but final­ly gave it up as impractical. They knew there would be considerable sweat­ing but estimated that only a small percentage of the controlled minerals would be lost by this route. “The problem with these procedures was that we’d be spending an inordinate amount of time in flight doing them,” Ker – win recalled. “With only three people aloft, eighty experiments to conduct, and a hotel to run, we needed everything streamlined and every nonessen­tial task deleted. We compromised. The investigators would use the aver­age weight of the green tape. We agreed to the many repetitions necessary to calibrate the mass-measurement devices in-flight to maximum accuracy, and they agreed not to require that accuracy in daily use.

“We also made another promise to ourselves. The rule was, if you didn’t eat all of a food item, you had to weigh the residue to keep accurate track of your intake. We vowed that if we started a food item, we’d finish it, and avoid having to weigh it.”

Many people in the medical field were involved in these issues, but the crew’s principal point of contact for the experiment was Dr. Paul C. Ram – baut, who functioned as the principal investigator’s principal coordinating scientist. Crewmembers argued, agreed, and compromised with Rambaut for several years. In January 1970 he wrote, “The proposed in-flight proce­dures do indeed involve excessive and unproductive use of crew time for manual manipulation of food, water and waste. This situation is unfortu­nate and its correction has so far eluded the most vigorous protests of the Medical Directorate.”

What Rambaut meant was that the Medical Directorate had fought hard for fully automated systems for collection and measurement of food and waste but had been spurned by the program manager because it would take too long, cost too much, and no one knew how to do it. The Medical Directorate was willing to make things as easy as possible for the crews. But they were absolutely not willing to compromise the validity of their exper­iments. In Apollo they had had to stand aside for operations. Skylab was their mission.

Progress was made during 1970. While the engineers were figuring out how to package soup in peel-top cans, NASA’s nutritionists were working on the menu. By August a list of seventy-two items was given to the crew for evaluation, and shortly thereafter their deletions and additions were tak­en into account. Out went the strawberry wafers, the lobster bisque, and the cheese soup; in went the German potato salad, peanut butter, and—in a move that would prove lucky later on—the Carnation Instant Breakfast. There were five soups, ten drinks, twenty-seven meat-and-fish items includ­ing chili with no beans, eight veggies, seventeen desserts and snacks, and five breakfast foods. The contract was issued (to Whirlpool, a washing machine manufacturer!) and food production planning began.

One of the new items accepted was frozen prime rib. Frozen? Yes! The program office had agreed to provide food freezers with enough capacity for about four hundred of the little food cans—almost enough to provide one frozen item per crewman per day. (The freezer, though, did not include a refrigerator, so fresh foods that would have to be kept cool were still not an option.) Besides prime rib the choices included filet mignon, buttered rolls, and coffee cake. The investigator objected to ice cream at first, fearing that its high fat content would make it too difficult to fit into the straitjacket of his dietary requirements. But the nutritionists showed that they could do the job, and ice cream was added to the list. This decision and these items were major contributors to crew satisfaction with the food, and the mission.

And then there was item number ten on the beverage list: “Wine (rose or sherry).” As the crewmembers discussed palatability and variety with the experimenters and attempted to make the diet as pleasant as practicable giv­en the constraints, someone said, “Wine is empty calories too! Let’s have some on the menu.” Surely, wine is empty calories by the standards of the experiment—it contains little or no protein or controlled electrolytes. But getting it by the doctors wasn’t so easy. Early in 1971 Deke Slayton wrote a memo requesting several changes to the food system. One of them was the addition of wine. This suggestion was indignantly rejected by the experi­menters. The reply stated, “We disagree with the assertion that the provi­sion of wine is mandatory to make the Skylab Food System flyable. Wine is not a necessary component of any nutritional regimen in any environment to which human beings are exposed. . . . The principal investigators of the MO71 and mho series of experiments are adamantly opposed to its use.”

The formal objection by the investigators’ representative, Dr. Leo Lutwak, stated, “Alcohol has effect on renal function via inhibition of anti-diuretic hormone. This introduces an additional variable even if consumed in the same amount daily by each man. Possible changes in retention and excre­tion of fluids and of hormones in flight (changes in kidney function with respect to water balance) are an important concern. . . .” But crew represen­tatives argued that if it were backed off to once a week, any effects would be transitory and self-correcting, and the investigators reluctantly concurred. This is how they put it:

Recomm endatio n:

1. Delete all alcoholic beverages from menu.

2. Will accept: a) No wine first two weeks in flight or in first 48 hours post flight. b) 4 oz. ofsherry (or equivalent stability wine) once per week thereafter. ”

The crew accepted this compromise philosophically. The nose of the cam­el was under the tent. Now they had only to select the wine. There were a few requirements. Dr. Lutwak was right; they needed to pick a sherry or other fortified wine that could tolerate storage in plastic for a year or more. Ordinary table wine, red or white, was likely to go bad. The other require­ment was to select an American wine.

A wine-tasting party was set up at Dr. Kerwin’s house on 20 November 1971. Wives were invited but didn’t get to vote. Kerwin had had the pleasure of narrowing down the list to six wines from Taylor, Paul Masson, Ingle – brook, Wente Brothers, Almaden, and Louis Martini. The evaluation sheet outlined the rating code (a modification of the Cooper-Harper scale used by military test pilots to describe the flying qualities of fighter planes) and added these comments:

There are six entries, three dry and three sweet. All are domestic. A couple of import­ed sherries are at the end ofthe table if you care to taste them for reference.

Recommend about У2 ounce for tasting purposes, as medical science cannot cure a wine hangover.

Plastic cups are provided to simulate flight hardware. It is permissible (though not mandatory) to re-use your cup. Rinsing facilities are not available—wipe with napkin or shirtsleeve if desired.

To help you fill out the "comment” line a list of adjectives follows: unpreten­tious, robust, dulcet, uncompromising, reminiscent, ethereal, insouciant, devil – may-care, cynical, Earthy. A more complete list is being compiled for the flight checklist.

The Taylor cream sherry was selected in a close contest, and Rita Rapp set about her packaging duties. But frustration lay ahead.

All of the crewmembers worked in a few public appearances during train­ing. One crewmember (“We won’t tell on you, Jerry,” Kerwin jokes) gave a talk in a southern state in which he mentioned that wine would be served on Skylab in the interest of gracious living and crew morale. Several of the listeners took umbrage at this, and letters began to arrive at NASA and con­gressional offices objecting to government-funded alcohol in space. NASA chose not to argue. Wine was quietly withdrawn from the menu, and the crews’ kidneys were spared.

Despite this setback, the food system came together nicely as launch day neared. Procedures were devised for stowing most of the food in large over­cans in the ring lockers in the upper workshop, each can carefully labeled with crewman, day, and meal. These would be brought down to the ward­room about a week’s worth at a time and arranged, ready for each meal. There was “overage” also stored—extra food in case of spills, substitutions (discouraged), or mission extensions. Much of the overage was devoted to items that wouldn’t affect mineral balance—lemon drops, butter cookies, black coffee. It was a little complicated in the days before bar codes, but everyone tried hard to make it work.

Also on the topic of mineral balance, there were the pills. It was very important to the investigators that the intake of protein, calcium, phos­phorus, and magnesium be held constant. Protein consumption had to be imbedded in the food items themselves, but the minerals could be consumed as supplements. So the following routine was devised: all items not eaten by each crewman were logged and reported to Houston during an evening sta­tus report. If an item was partially eaten, the residue was “weighed” and the weight reported. Overnight, the medical team calculated how much of these minerals had not been consumed, and in the morning a teleprinter message told each man how many calcium, phosphorus, or magnesium pills to take. Munching the morning pills quickly became routine.

As a final gesture of solidarity, the dieticians managed to squeeze a num­ber of fresh items into the crews’ diets during the pre-and postflight quar­antine periods. It was really nice to have a fresh salad with dinner amidst the cans and bags. The meals were pleasant and memorable and contribut­ed to a team spirit that made the hard work of experiment compliance in flight manageable.

The other major intersection between research and operations was exer­cise. It was a design challenge and battleground between the crews, the researchers and, often, the managers. When the Mercury astronauts were selected, there was an enormous emphasis on physical conditioning and toughness based on a complete ignorance of the effects of weightlessness on humans. So the Original Seven, having been exposed to every stress the doctors could think up, concluded that staying in shape was their respon­sibility, and nobody was going to tell them how to do it.

As Mercury and Gemini flights took place during the years 1961 through 1966, all in small capsules with little or no opportunity for exercise and for durations extending to Gemini 7’s fourteen days, a pattern began to emerge. Astronauts had eaten less during flight and returned having lost weight and (subjectively) some strength. There was evidence of a decrease in blood vol­ume and a suspicion that bone density might be decreasing. Normal bodi­ly functions were accomplished with no trouble, and the astronauts did not suffer psychologically — quite the reverse. They loved the weightlessness of space and declared their readiness to go to the moon.

More of the same was seen during Project Apollo. The crews accomplished their lunar surface excursions with enthusiasm and success, but they defi­nitely paid a price, coming home tired and needing several days to recover their preflight weight and strength. Space motion sickness, first reported in the Soviet space program, began to occur in the larger Apollo spacecraft; and there was a bit of a scare on Apollo 15 when the two lunar surface crew­men developed cardiac arrhythmias during the return flight. This was attrib­uted to a loss of fluid and electrolytes, especially potassium, during their extensive lunar surface activities. “No big deal,” said the astronauts, and the missions continued with potassium added to the orange juice. But a case could be made that their strength and endurance, and thus their ability to perform challenging physical tasks such as spacewalks, would be compro­mised on very long flights.

The doctors tried their best to organize an exercise program during Apol­lo. These efforts were rejected. Here is a quotation from a memo from Deke Slayton to Chuck Berry, dated 27 March 1968:

Your recent offer to assist in development of an in-flight exercise program for Apollo is appreciated. . . . I believe it is clearly understood that crew physical conditioning is the responsibility of this Directorate. . . . Our intention is to provide each crew with the means and protocol to maintain a reasonable level ofphysical well-being. We have no intention of complicating the procedure by keying to station passes, data collection points, or dictated work levels. You will be provided the crew’s best qualitative evaluation of their exercise program in the post-flight report.

That was the background for Skylab, which was to be the first opportu­nity for medical researchers to gain extensive in-flight data on human phys­iology in weightlessness. One of the centerpiece medical experiments was to be an exercise tolerance test. The astronauts would exercise on a bicycle ergometer to 75 percent of their maximum preflight capacity, while extensive measurements were made of heart rate, blood pressure, a twelve-lead elec­trocardiogram, oxygen consumption, and carbon dioxide production. The tests would be repeated every four days. The ergometer, without the mea­surements, would be available for exercise on the other days. It maintained good cardio-respiratory conditioning, but did little for strength.

Nobody raised any objection to the test. But there were several problems associated with the use of the ergometer for crew exercise. These ranged from whether and how a bicycle could be ridden in zero-G, and whether the data from zero-G would be comparable to that from pre-and postflight runs, to the question of how much daily exercise was the right amount, and wheth­er the ergometer alone was enough equipment. There was another device onboard, the Exergym—a small rope-and-capstan device that allowed a certain amount of “isokinetic” exercise—leg and arm pulling and push­ing at a constant velocity against a load. It was difficult to use and was used very little.

At the heart of the daily exercise debate was a fundamental issue. In order to understand the effects of long-duration spaceflight on humans, was it best to prescribe and constrain exercise or to let it vary freely and mea­sure and observe what happened? The research community was in favor of prescription. They argued that unless all possible variables could be con­trolled, the changes observed would be difficult, maybe impossible, to inter­pret. They had the science of statistical significance behind them.

The operations community (astronauts and most flight surgeons) was in favor of “measure and observe.” They argued that there was insufficient knowledge to write a good prescription; that there were too many variables whose control would have to be attempted—especially individual varia­tions in exercise tolerance and preflight conditioning; and that more would be learned by allowing the nine crewmembers to react to the environment. Having a spread of in-flight exercise intensity was good, they said; it would provide a chance to see whether a dose-response curve existed. And of course, the crew still had that strong distaste for being regimented.

The Skylab I crew worked out a compromise agreement. They would devise and document both a preflight and an in-flight exercise plan and would care­fully record all in-flight exercise. About six months before launch, the first crew performed their baseline exercise runs on the training version of the ergometer. The ergometer was a good aerobic device; it had been designed to accommodate loads of up to 300 watts for thirty minutes. But Bill Thornton had ridden the training version at 300 watts for nearly an hour and destroyed the motor; henceforth, it was “de-rated” to 250 watts. That turned out to be enough for the Skylab astronauts.

The baselines determined were the watts at which three minutes of ped­aling would stress each crewman to 25 percent, 50 percent and 75 percent of the maximum heart rate of which he was capable; that would be the in-flight protocol. Conrad’s baseline was 50, 80, and 120 watts; Kerwin’s, 50, 100, and 150 watts; Weitz’s, 100, 150, and 175. That’s when Conrad decided it was time to get in shape. He exercised his command authority to require a session of paddleball daily with one or the other of his crewmates. All three improved their conditioning noticeably. But the researchers decided it was too late to change the baseline; the crew ought to have an easy time of it on orbit.

How did it all turn out? All nine astronauts returned to Earth safely, and all but one are alive and well, over three decades later. The exception is Pete Conrad, who was healthy and vigorous until his tragic death in a motorcy­cle accident in 1999. But did the Skylab team accomplish their goals? Did they measure the right things and measure them accurately? Were they able to draw conclusions? And did they discover what’s needed to keep people well and effective in space?

First, all the equipment worked. Food was consumed, uneaten items logged, supplement pills taken. Urine was sampled and frozen; feces were proper­ly processed and dried; both were correctly returned. Exercise was accom­plished once it was learned how; oxygen consumption and vital signs were duly recorded. Lower body negative pressure and rotating chair devices did not fail. Nine men were measured as never before. And it’s a good thing they were because NASA remained conservative and skeptical till the end. Dur­ing the final flight, the NASA administrator required a weekly report—on Wednesdays, and in writing—that the crew was in good condition and cer­tified to go another week.

In spaceflight, the first symptom to show up is usually space motion sick­ness. The term was bowdlerized to “space adaptation syndrome” by some thoughtful researchers, but some irreverent crewmen called it dreaded space motion sickness, or “dsms” for short. It’s a lot like seasickness, and a severe case can make you miserable. A problem with treating motion sickness is that if you are already sick and take a pill, you’re likely just to throw it up. Shuttle crewmembers who get spacesick are now given injections to con­trol their symptoms. The drug, promethazine, is quite effective but makes you sleepy.

The odd thing is that a person’s susceptibility to motion sickness on Earth has no predictive value in space. You can be quite sensitive in boats or cars and never have a quiver while weightless, or the reverse. But repeated flights tend to diminish the severity of the illness. And after it goes away, usually in three or four days, zero-G is a lot of fun.

The Skylab I crew had no space adaptation syndrome during flight. Ker – win got seasick after splashdown and threw up in sickbay on the carrier, but seasickness was not unusual for him. The most surprising finding was that the rotating chair experiment showed that the crew was immune to motion sickness in flight once they had adapted. Kerwin said, “I think life on a rotating spacecraft will be easier than I thought.”

Once they learned how to ride the bicycle ergometer in zero-G, their per­formance matched their preflight levels. In between medical runs, Conrad exercised the most, Kerwin the least. In contrast with exercise, the lower body negative pressure experiment was much more stressful right from the

first run. Heart rates were higher, blood pressures dropped, and several runs were terminated early to make sure the subject didn’t pass out. Kerwin was the most susceptible. This was a concern early in the flight, but subsequent runs showed no further deterioration in performance.

Those three experiments were the main source of in-flight data on adap­tation — or deterioration—and the overall picture looked good. Also the crew ate well, slept well, and felt well. The physical work involved in their spacewalks gave them no trouble. Twenty-eight days in space seemed quite feasible. How would they react to gravity after landing?

Here are the basic findings. The crew had lost an average of 7.5 pounds of weight. They were unsteady and walked with feet wide apart. They were most comfortable lying down. Standing heart rate was 30 percent high­er than preflight. Ability to exercise on the treadmill was correspondingly lower; each of those heartbeats was moving less blood through their arter­ies. Treadmill performance on landing day did correlate with in-flight exer­cise; Conrad did best, while Kerwin was too tired to use the ergometer at all until the next morning. Response to the first lower body negative pres­sure test was just about the same as to the last in-flight test — worse than preflight. Blood tests showed that blood volume was down, and the num­ber of circulating red cells was smaller by 14 percent—the bone marrow was not producing them at all. Finally, postflight strength measurements on the arm and leg muscles showed big decrements.

Return to normal was relatively rapid. The crewmen ate and drank vig­orously after their first good night’s sleep, and much of the weight loss had been restored by the fifth day back. Performance on the lbnp and ergom­eter was close to normal preflight limits in a week, and completely normal in three weeks. Full leg strength returned more slowly, depending on what exercise the men chose to perform.

Some questions remained. Their bone marrow didn’t start to produce red cells again until about three weeks after landing. Imaging wasn’t sensi­tive enough to show visible bone loss, but examination of the returned urine and feces showed that they were losing calcium steadily with no sign of lev­eling off. The in-flight cardiovascular data from lbnp could be interpret­ed as “not yet steady state.” And the large losses in arm and especially leg strength were a sign that the crew hadn’t exercised enough. The next crew was strongly urged to do more.

Skylab 11, unlike their predecessors, faced space adaptation syndrome on Mission Day i. Lousma was most affected and vomited that evening. Bean and Garriott felt nausea; all three took Scop-Dex capsules on Day 2 to sup­press the symptoms, and Garriott and Lousma continued this medication on Day 3. Garriott and Bean tried making head movements to hasten their adaptation but decided they were not helpful. All were well enough for full duty by Day 4.

Initial adaptation issues aside, this crew’s in-flight experience was similar to that of the first crew. The big change was that they performed more exer­cise and did not allow exercise time to be preempted by other tasks as the first crew sometimes had. They launched with two additional exercise devic­es. After seeing the first crew’s strength losses, Bill Thornton got permission from Deke Slayton to add capability, with strict weight and volume limi­tations. (Exercise was still an operational responsibility.) Bill looked every­where for candidates, and found the Mini-Gym in John Rummel’s back room. He rebuilt it with help from center engineering and flight-qualified it. It was designed to produce “isotonic” loads on the back and legs, and was used faithfully by the crew during longer daily exercise periods. The other device was an “expander” from Sears, consisting of up to four springs with handles that could be used in various combinations. (The Russians cop­ied this device and used it in their Soyuz program for many years.) These devices largely solved the upper-body problem. The second crew also had a device to measure blood hemoglobin levels, to reassure the doctors that loss of red cells was not continuing.

Skylab II returned to Earth on 25 September 1973 at nineteen past one in the afternoon, and the Command Module was picked up by the uss New Orleans forty-four minutes later. Here’s some conversation between the crew­members and the crew Flight Surgeon, Dr. Paul Buchanan, as they pre­pared to egress:

Bean: “We’re going to have to be careful; as I said, I was dizzy. Better stick with me. But I feel like if I could move around, just sit up, and maybe the dizziness would go away.”

Garriott (who had already left his couch and taken the pulse of his crewmates): “I don’t think it will, Al. You ought to watch for it to increase slightly. It’s likely to increase, I think.”

Buchanan (to Garriott): “Are you doing all right standing?”

Garriott: “I’m doing fine, but I can tell that any sort of motion induces the sensation of pitching or rolling, a little dizziness.”

Bean: “That’s what I thought when I just leaned up. I thought that I didn’t feel like I was going to pass out, but I did feel like—that I would be unsta­ble. . . . Let’s not leave these guys standing out here too long.”

Bean (ten minutes later, in the medical lab): “I didn’t think we’d get back feeling this good.”

They did feel good, and they recovered rapidly from the effects of their flight—Garriott fastest. Their weight losses had been for Bean, 8.6 lbs. (5.5 percent); Garriott, 7.7 lbs. (5.7 percent); and Lousma, 9.25 lbs. (4.75 percent). By “r+5,” the fifth day after landing, their lower body negative pressure and exercise tolerance tests were “within normal limits”—that is, back with­in two standard deviations of their preflight results. That’s not 100 percent recovery, but it’s impressive. After R+9, Garriott and Lousma were returned to flight status in the T-38. Bean had strained his back on r+i (showing that muscles were a little more susceptible to injury after a long flight) and didn’t get back to flying for another week or so.

Loss of strength and endurance in the legs was virtually the same for this crew as for the first crew. That was a very encouraging finding and a worth­while payoff for the additional time this crew spent on exercise (about an hour a day each). But the decrements were still on the order of 20 percent, and Bean’s crew recommended to Carr’s that they increase exercise even more on their flight, then being extended to eighty-four days.

Although legs showed a decrement with their diminished use in weight­lessness, the arms were different. They were not only used for translation around the workshop, but there were two useful exercise machines available for heavy exercise. Jack was a consistent user of this hardware and his early postflight data show an average 15 percent increase in arm strength, while his two crewmates showed little change.

And that is when Dr. Bill Thornton, who was making the strength mea­surements, invented his “Thornton treadmill.” Faced with even more strin­gent limitations on what could be launched in the Command Module, Bill Thornton and engineering built the poor man’s treadmill from a strip of slippery Teflon, which could be fastened to the Skylab floor with fasten­ers already on board. The crew placed the Teflon near a side wall with a handrail to hold on to. Wearing cotton socks and the previously discarded

ergometer waist restraint, fastened to the floor with 180 pound-force bun­gees, they canted their bodies about thirty degrees forward and “ran,” feet slipping on the Teflon surface. It was much harder work than running, but it did the trick.

The Skylab ill crew lived longer in space than anyone had before—a lot longer—and spent more time and concentration thinking about the lack of gravity and its effect on their body and their performance. For the first month they felt rushed and behind and didn’t get enough sleep. After that they settled into a productive routine. How did they feel about it? Here is what they shared during the medical debrief:

Question: “When did you think you were in control of things and every­thing was ok?”

Ed: “Somewhere between four and six weeks. At four weeks we were over the hill and I think had started to settle down and by six weeks I felt locked in solid.”

Jerry: “If you drew a graph from launch day, you would have a fully steep slope and the graph would bottom out the day the three of us bombed out on M092 (for Jerry, that was on Mission Day 16, i December). And from then on, you can chart a gradual increase with a fairly reasonable slope until prob­ably Day 45, and then you could throw a gentle knee into it. Again there’s a positive slope, and we were on the increase all the way to the end.”

How stressful was the lower body negative pressure experiment? All three men came near to fainting on tests run during the tenth to sixteenth flight day. For these tests another astronaut was always assigned as an observer, able to watch the subject’s signs and terminate the tests if warranted. The test involved subjecting the subject’s lower body to a partial vacuum. There were three steps of increasing vacuum: minus thirty, forty, and fifty milli­meters of mercury, the latter estimated to pull blood into the legs about as much as standing quietly upright in normal gravity. These tests were ter­minated early, before the end of the minus fifty exposure—probably mak­ing both crew and experimenters a little doubtful that they’d go the whole three months. But things got better from there. Gibson had only one more test stopped, on Day 71; Carr and Pogue had none. Here are some of their comments:

Ed: “I would say that thirty up there was like fifty down here. . . the amount of sleep, amount of water intake and amount of salt intake were significant [variables] for me. If I felt dehydrated or overtired, I knew I would have a problem with lbnp. . . . I’ve always felt a craving for salt on this diet.”

Bill: “And related to that, perhaps equivalent, was the time of day. . . ear­lier in the day, you felt better.”

These men could feel the fluids shift within their bodies. During lbnp they would feel less fullness in the head as their legs became engorged—and sometimes that would be followed by cold sweat and faintness. Exercise also shifted fluid into muscles, but it felt much better. So did eva.

Jerry: “But the times when I could feel the fluid shifts the most were dur­ing exercise. As soon as you got on the bike and started pedaling, your head immediately began to clear up. And by the time you finished pedaling and the blood had shifted to your muscles, you felt great. Your nose was clear, the pressure was off your sinuses, and you felt good; tired from the work, but you felt clear.

Ed: “I recall that on the first eva it felt good to get outside and do some physical work for a long period of time. It was comfortable to have a heart rate above nominal for the duration of the eva.”

In contrast, they felt periods of dullness or sleepiness during times of less activity:

Jerry: “I think that during a period of adjustment my stamina, reserve, or whatever you want to call it, was gone. I found myself essentially living from meal to meal, what we call a lowering of blood sugar, when you’re get­ting really hungry and you start feeling fatigued and tired and dull. I don’t know what it is. I call it a lowering of the blood sugar. That’s what we felt up there, but as soon as we got a meal in us we would feel much better. You feel a little drowsy after the meal, but shortly after that you feel better. But then it only takes about two to three hours for you to become tired again. The old reserve and the stamina is gone and by 3:30 in the afternoon we were hungry again, feeling bad.”

Voice: “Did all three of you feel that?”

Bill: “I feel that way, but I would have liked to snack all the time I was up there; candy bars to eat periodically. I could have used those through­out the mission.”

Jerry: “I wish I could tell you where the calories go when you’re up there.”

Ed: “I felt the same effect as Jerry mentioned. I would have liked snacks. I would have liked three meals and then snacks in between, some high-ener­gy food like Bill mentioned.”

Question: “Listening to you, I get the impression that one might suggest shorter days or naps, recharging in that manner as well as eating.”

Ed: “A siesta right about noon time would have been great.”

Question: “Could you appreciate that your legs had diminished in size?

Ed: “You could see it and I think I could feel it in my calves, after I had worked the Thornton device, for example. That really was an excellent device. I’m glad we had it along. When did we start using it, around two weeks into the mission?”

Jerry: “Yes, somewhere between Day Ten and Fourteen is when we final­ly got time to set it up and start using it.”

Ed: “And from then on, we started to turn around.”

Jerry: “I felt pre-flight that the lbnp could be used. . . to maintain con­dition. I always hoped that you would take one of us as a control and put us in it every day as part of exercise. . . use it as an exercise tool and not require. . . all the instrumentation. Just get in it every day for five or ten minutes then see what you ended up with, compared to the other two guys.”

Question: “Which of you would have volunteered to be the no-exercise, no-LBNP control?”

Jerry: “Oh, I didn’t say no exercise (laughter). We had already decided that there would be no volunteers for no exercise.”

To summarize the crew’s opinion, the lbnp didn’t do much for them, but exercise was essential. And the postflight findings certainly bore them out.

They all adapted well to the topsy-turvy world ofweightlessness. As Carr related: “The first two-thirds of the mission, my dreams were one – G dreams, and I shifted to zero-G dreams about the last third. It really surprised me that I had some zero-G dreams.” They struggled a little bit to describe the feeling of carrying one’s personal “up” and “down” around in space:

Jerry: “Looking out the window at the Earth, sometimes the horizon would be upside-down. It was convenient just to flip (my own body) upside

down and look out the window. . . [but then] every once in a while you’d look inside at one of the other guys ‘upside-down with his feet locked in the ceiling’ and he looked funny that way. And the table was upside down. It was very strange.”

Jerry: “The normal mode of moving was just to go head first, whistling right down through the dome hatch all the way to the trash airlock. [But] if I ever decided to go through the other way, feet first, I had a very distinc­tive impression that I was very high and sure didn’t want to fall and hurt myself. It’s just because I had my feet out in front of me and all of a sudden there was a reference that connoted high.”

The following table compares data from the three Skylab crews.

Those averages hide some sizeable individual variations. On Skylab I Con­rad exercised almost twice as much as Kerwin and munched many more cal­ories per kilogram than either of his crewmates. On Skylab II Lousma was a tiger for exercise, but Garriott ate the most. And on the final mission Carr set a record by losing essentially no weight (only two tenths of a pound) in nearly three months aloft. He was only the second astronaut ever not to lose weight in space. The first was Alan Shepard, not on his fifteen-minute Mer­cury flight but on his Apollo 14 journey to the moon.

But the averages do tell the story. The story is, “Feed them, exercise them hard, and they’ll do well in space.” Or, to quote Dr. Bill Thornton: “The conclusion is that muscle in space is no different from muscle on Earth; if it is properly nourished and exercised at reasonable load levels, it will main­tain its function.”

Based on the Skylab findings, here’s a combined narrative of what you could expect to happen to your body if you took a big “grand tour” flight to Mars.

When the rattle of the booster stops and you’re in orbit, that strange feel­ing of floating will occupy your attention fully. Your head feels full, as if you had a cold. You’ve been briefed to be very slow and careful with head and body movements. You will take this good advice and feel ok—but the per­son in the next seat will suddenly feel nauseated and reach for the sick bag. The flight attendant (all are trained nurses, as in the early days of commer­cial aviation) will give your neighbor an injection, and he’ll feel a little bet­ter in the morning and be back to normal in three days or so.

Your vestibular system adapts slowly to the absence of “down” — that constant acceleration of gravity. The same absence causes body fluids to migrate from the lower extremities up into your chest and abdomen; the body responds by decreasing thirst and effectively losing fluid. Your blood becomes a little more concentrated, with a higher red cell count. Your bone marrow notices this and stops producing new red cells.

You won’t get space motion sickness, but your appetite won’t be very good for the first several days, and learning to move, eat, go to the bath­room, and sleep while floating may seem hard. On the morning of day eight you’ll wake up thinking, “Wow! I feel great today!” But you’ll have lost six pounds since the day before launch. Your legs look ridiculously skinny. The chief flight attendant now puts you on a strict exercise program for the dura­tion of the flight.

Unused muscles atrophy; exercise is needed to keep them fit, and you have to keep doing it faithfully. A treadmill keeps your heart and lungs in order and provides some leg exercise; other devices simulate weight lift­ing and tone the other big muscle groups. The compression also helps your bone retain calcium, slowing the gradual thinning of bone structure that is another feature of zero-G.

Your flight goes on for several months. Your workload is light. The novelty of looking out the window at the stars slowly wears off; you become bored. Small habits and mannerisms of one of your fellow passengers, “Herb,” begin to irritate you. Psychological stress — “cabin fever”—is definitely a risk of long spaceflights as it is of any long isolation with a small group of people. Skylab didn’t experience much of that, because the crews had been so care­fully selected and extensively trained. We hope that your Mars flight has a compatible crew and good leadership. Talk to the flight surgeon about your problems with “Herb.”

You make it through the flight with flying colors. As reentry day gets clos­er, everyone becomes excited and upbeat. You and “Herb” exchange e-mail addresses. You’ve almost forgotten what gravity feels like. Now you are about to be reminded! You survive the parachute landing at the Space Recovery Field and are helped out of the spacecraft. You don’t feel very good. Every time you move your head the world moves too, a severe vertigo. You feel as if you weigh three hundred pounds, and you walk unsteadily, with feet wide apart. Your pulse races. You feel dizzy, tired, light-headed, and thirsty.

First your vestibular system needs to readapt to the long-absent gravity vector. Your weight is only a few pounds less than when you left, but you are low on body fluids and red cells in the blood—almost as though you had bled a pint or two from a wound. And your muscles, despite the exercise (did you slack off a little the last few weeks?) are weak. A very light landing day and a very long night’s sleep start you on the road to recovery. Next morning you feel like someone getting up after a bout with the flu—a little light-headed still, but good. A period of rehabilitation, with careful, supervised exercis­es, will be prescribed for three weeks to get you back to normal.

The red cell count will be normal in a month or so. Most of the calci­um lost from your bones will eventually return. You’ll have been exposed to radiation during your trip, including cosmic rays; the amount will deter­mine whether any future threats to health exist. The lifetime limit is prob­ably one Mars trip per person.

The Skylab medical data set rigorously quantified all these changes and allowed the causes of many of them to be understood. It demonstrated the safety of three-month spaceflights sufficiently to allow NASA to plan and build the International Space Station—and incidentally to allow the Soviet Union to plan and build Mir. Both the United States and Russia have built on this data and now routinely fly for up to six months. But the strict quan­titative metabolic balance study Skylab accomplished has never been repeat­ed. It did the job. And repeating it would drive the astronauts nuts.

For solar observations it is essential to note that our atmosphere is opaque to portions of the sun’s radiation. Only the so-called visible wavelengths, from about 400 to 800 nanometers (4,000 to 8,000 Angstroms) can pass through

the atmosphere without significant absorption. It is presumably no coin­cidence that this just happens to be the wavelengths at which our eyes are sensitive to light; while it is presumably a coincidence that the sun’s major radiation band is passed through the atmosphere to warm our planet. But the sun also radiates substantially at even shorter wavelengths in the ultra­violet, extreme ultraviolet, and x-ray ranges. It is again fortunate that the atmosphere does absorb these rays as they would otherwise be lethal to all forms of life here on the Earth’s surface. Without the thick atmosphere (and the Earth’s magnetic field for protection against arriving charged particles) we might all be living in caves, underground, or in the water.

So the Skylab was equipped with eight large telescopes in a large canister called the Apollo Telescope Mount, most of which had to be above almost all of the atmosphere to function properly. Two of the telescopes looked at the sun at visible wavelengths called “hydrogen-alpha,” radiation coming from excited hydrogen atoms in the solar atmosphere. As this wavelength can be seen with ground-based telescopes, it provided a means of coordinat­ing observations with terrestrial observatories all around the globe to look at a particular feature and compare observations. Three more telescopes were sensitive to the extreme ultraviolet and two to the x-ray portion of the spec­trum. The sun looks quite different at each of these wavelengths, and solar astronomers use these differences to deduce many things about the sun. For example, each wavelength of emission is directly related to a different tem­perature of the emitting atom and therefore to a different altitude in the solar atmosphere, which permits a much better picture of the sun’s struc­ture to be constructed.

The eighth telescope was a White Light Coronagraph, which could have worked on the ground except for the fact that the sun’s disk is about one million times brighter than the faint corona. Light scattering in our atmo­sphere from the bright disk completely swamps the faint coronal light here on Earth. The one exception to this occurs at times of a total solar eclipse, when the moon passes directly in front of the sun and blocks out its bright light. So only for a few minutes every year or so, at some places in the world (usually remote, it seems), it is possible to see the solar corona. But on Skylab an occulting disk was placed in front of the telescope to replace the moon, and the crew could then see the corona continuously whenever they were not on the dark side of the orbit.

So the ground astronomers and the crew remained in close contact every day. The ground teams worked up plans for how the crews could best opti­mize their limited observation time. There could be at most periods of about fifty minutes of sunlight, coming about ten times each twenty-four hours. Although there were almost sixteen orbits each Earth day, the crew was sleep­ing or otherwise occupied on some of them. This still permitted substan­tially more observational time than in the original flight plan. The ground team noted what the likely interesting solar features might be, argued with­in their own ranks about which instruments should have priority on each occasion, then had to argue with other research disciplines when special cir­cumstances arose, sometimes taking their case all the way up to the flight director who controlled the whole mission for a decision. Then when their plan was sent up to the crew on a teleprinter, the crews would plan the orbit’s activity and usually follow the ground’s suggestions. But the final pointing of instruments always had to be done onboard, and whenever solar condi­tions changed or the crew saw evidence of even more interesting phenom­ena, they might well change the ground plan and proceed with an alterna­tive observational program.

With the extreme ultraviolet telescopes the view presented was of gases at tens of thousands of degrees Celsius, coming from the chromosphere above the photosphere, which is the part of the sun the naked eye sees. With the x-ray telescopes the crew was viewing gases at millions of degrees Celsius, where the emission comes from even higher in the corona. All of these fea­tures differ when the sun is very active as compared with a cooler and very quiet sun. The sun’s activity varies over a cycle of about eleven years. When Skylab was first planned, it was hoped to have a very active sun, which would be especially interesting to most of the solar astronomers. But flight delays of several years pushed the launch date out into the quiet portion of the cycle. Then nature came to the rescue. As it happened during the second mission, the sun became very active, at least on one side, and the sunspot number (a measure of the number of visible black dots and groups on the surface of the sun) varied all the way from io to over 150 at other times. So very good observations could be made from quiet to very active solar conditions.

The White Light Coronagraph stood apart from the other experiments in that it looked at the very faint light coming from far above the disk of the sun. Of particular interest were phenomena then called “coronal tran­sients,” but now called “coronal mass ejections,” or cmes. In these cases a long magnetic strand lifts off the lower atmosphere and expands into an enormous loop far out into the corona like a stretched rubber band. Occa­sionally, the band is stretched so far that it breaks apart and the confined gases escape into interplanetary space.

When this happens a coronal mass ejection occurs and if it is pointed in the correct general direction, it will eventually arrive in the vicinity of the Earth. This usually takes two to three days. When it gets here, it frequently produces not only the beautiful aurora but also not-so-desirable power line fluctuations or outages and sometimes damage to sensitive satellites in Earth orbit. Even though satellites in Earth orbit may be damaged, it could be far worse for space probes or manned spacecraft far outside the magnetic enve­lope (the magnetosphere) of the Earth. In this case very energetic solar pro­tons could be more dangerous to space probes and people, whereas within the magnetosphere, the magnetic field largely turns away the charged par­ticles streaming outward from the sun.

Garriott reported one of the most exciting observations of his mission was the day the first major cme was observed. “As I recall, the ground called us and alerted us to the possibility that one of the low magnetic loops appeared to be rising. When we first looked at the White Light Coronograph, indeed, the loop was already extended roughly a solar radius or half a million miles above the photosphere. So I promptly took a Polaroid picture of the screen while we also activated others of the telescopes to record relevant data as well. Then when we came back around the Earth in about an hour and a half, I took another Polaroid photo, and sure enough the loop had expand­ed by perhaps another two solar radii into the corona. A quick calculation told us that the outward velocity of the cme was at least 500 kilometers per second, a phenomenal speed it seemed to us! As far as I know, this was the first visual observation of a cme and the first real-time measurement of its minimum speed. When analyzed more carefully on the ground, the same number was calculated.

“Also of interest to us were small spots visible in the extreme ultraviolet, but not on the hydrogen-alpha visible images. For lack of better terminol­ogy, we called them ‘xuv bright points.’ We didn’t really know what they were or their relevance to other solar events. We hoped they might even be precursors to a solar flare, for which a full study was a very high priority. They didn’t seem to live too long, maybe thirty minutes, then faded away. We spent quite a lot of time studying them in space, and subsequent analysis on the ground revealed that they are the source of much of the solar magne­tism. In addition we felt that they could be the location of new solar flares, so we watched them carefully. Indeed, Ed used this clue to provide imag­es of the very early stages of a flare by following the development of one of the ‘bright points.’”

Another feature studied at considerable length was coronal holes, which are areas of very low emission. They can be discerned all across the spec­trum, but especially in hydrogen-alpha emission and at xuv wavelengths. Both the ground and the space crew could see them, permitting close coop­eration in selecting targets and timing. What was less expected was to see the close association between areas on the sun’s face where there was very little emission (the “holes”) and the solar wind, which permeates all of interplan­etary space. It appears that the “holes” are areas where any local magnetic fields do not form loops, but instead are essentially open. For this reason, any hot gases from the sun, which would otherwise be trapped by the solar magnetic field, can now flow straight out into space.

While the results of Skylab solar observations seemed to exceed even the ground investigators’ expectations, one of its most valuable benefits was the instruction it provided to later experimenters who wanted even longer con­tinuous observations of particular features. The corona and cmes? Now the researchers knew roughly their frequency and speed. They knew to connect them to appearance of coronal holes visible on the ground. Bright points? Solar physicists have now been studying them for decades building from the pioneering work on Skylab. Much of the next phases of solar research have been done with automated satellites based on the results found on Skylab.

Designing and operating the manned solar observatory, the Apollo Tele­scope Mount, presented a challenge of epic proportions for the atm team composed of principal investigators who remained on the ground, the instru­ment designers, ground control personnel, and the nine Skylab crewmen who operated the observatory in flight. Like other such challenges, it proved to be highly demanding, rewarding, and just plain enjoyable, especially for those fortunate enough to operate the observatory in flight.

Skylab, and atm in particular, served as an illuminating milestone to both the test pilots and scientists in the astronaut corps: “Hey, even scientists have major contributions to make,” and “Even test pilots can actually learn sci­ence.” Enough lively kidding and chain pulling by both groups took place in training to field a cohesive, capable, and dedicated team of observers on each of the three missions.

Unlike most stellar observations, the detail visible on our nearest star demanded that crews be prepared to continuously make operational decisions with each instrument in space (instrument pointing), time (times of opera­tion and film exposures), and wavelength (use of different instrument oper­ational modes that covered the spectrum from visible light all the way down to x-rays). Our mother star is rich in a variety of features including granu­lation, supergranulation, sunspots, active regions, filaments, bright points, and coronal structure. Solar events also cover a wide range of the required time resolution from its eleven-year activity cycle down to flares, which are solar explosions that can rise within seconds. It was the challenge of the atm team to put instruments in orbit with cutting-edge observational capabili­ties and operate them in the way that maximized further understanding of known solar features and events and discoveries of new phenomena.

But just how does one meet this challenge? Basically, there were four essential components to the atm team’s approach:

Place in orbit state-of-the-art instruments with cutting-edge capabilities.

Provide the in-flight observers with real-time, appropriate feed­back on relevant features and events on the sun to enable them to make the best choices in space, time, and wavelength for observation.

Ensure each operator has the background and training to effectively operate the atm observatory.

Ensure the flight plan has the flexibility to accommodate optimum ground scheduling and observer real-time modifications.

i. State-of-the-Art Instruments

The principal investigators designed and had constructed instruments with cutting-edge capabilities. When designed, the instruments that made up the observatory had the highest feasible resolution in space, time, and wavelength and best combination of capabilities to meet the observing challenge.

In the design phase the potential observers, the astronauts assigned to work on the atm, had little impact on the design except in two important areas: the instrument controls and displays and real-time data fed back to

the observer. As the integration of the observer into the design matured, the mandate for an integrated, simultaneous operation of the individual instru­ments was manifested in the instrument control and display (c&d) design. Design engineers each wanted their own c&D real estate for their instru­ment to do with as they saw fit. “We, the crew, wanted to stress the func­tional similarities in the way each instrument was operated as well as the sequence of each control operation,” Ed Gibson explained. “After ‘spirited discussions’ and hard work on both sides, we arrived at a ‘functional (verti­cally aligned)—sequential (horizontal order of operations)’ layout. For both training and in-flight operation, this layout proved to be highly effective.”

With today’s computer capabilities it is hard to imagine that many of the operational modes and exposure times for the instruments had to be frozen into the design many years before launch and could not be changed as knowl­edge increased before and during flight. However, the Pis did an exceptional job of incorporating a wide range of possibilities into their design.

Despite the thought, sophistication, and expense that went into the obser­vatory, the crew still managed to demonstrate the adage, “When the going

gets tough, the tough use duct tape.” Crib sheets, Polaroid cameras, and food containers were among the many items that were accommodated at the c&D panel by the astronauts’ universal tool—duct tape. However, when it was taken outside on an eva, the glue on the tape was either frozen solid by the cold blackness of night or turned to soup by the heat of direct sun.

“The flight crewmen were provided an exceptional array of highly useful data,” Gibson explained. “We had displays in white light and at a wavelength called hydrogen-alpha, both very useful and also visible on the ground. We were provided individual displays of the sun in extreme ultraviolet and x-rays as well as a display of the corona. Lastly we had a highly versatile display in the ultraviolet that allowed us to read the intensity of radiation across the ultraviolet spectrum at a point or over a region of the sun at a sin­gle wavelength.”

Although all Pis firmly supported the central role of the in-flight observ­er in the data acquisition, the astronauts had an insatiable appetite for dis­play of far more real-time data than the instrument designers could afford or provide without degrading reliability. In the design phase a classic chick – en-and-egg controversy ensued: “Why do you astronauts need to see the atmosphere of the sun in real-time? We’ve never seen any rapid changes from down here!” versus “But we don’t know for sure what the sun’s atmosphere is doing unless we look at it. If we only take data at preprogrammed times, we’re likely to miss some very important observations.” Over many months the spirited discussions oscillated between lofty observational philosophy and detailed nut-and-bolts design. Fortunately, the instrument designers were able to make a few accommodations, which, knowing what we know now, produced some very important real-time understanding of the sun for both ground and in-flight observers and the capture of data on events that otherwise would have been missed.

Given the exceptional instrument array and real-time feedback on solar struc­ture and events, it was then up to the flight crew to respond in ways that max­imized the new and important information in the returned data. Thus, the task before flight was to provide the observers with the best possible train­ing. But the training program had a few challenges: the time available was

limited by the approaching launch dates and demands of other mandatory training and by the backgrounds of the observers ranging from test pilots with little science expertise to scientists who had a good understanding of physics and some of solar physics. In the end each crewman had to possess a working knowledge of solar physics and an expertise in performing the atm tasks. The first challenge was a given, and all that could be done was done to carve out as much time as humanly possible. In meeting the sec­ond challenge, each and every potential observer demonstrated the nature and mental disposition to maximize their learning. Some understood that they would be expected to operate the instruments with negligible errors as a highly skilled technician. Others understood that they would be required to be not only highly skilled technicians but to also alter the in-flight oper­ations in real time as their scientific judgment dictated. All nine crewmen who flew responded to the very best of their individual abilities.

Along with the excellent procedures trainer that was provided, a major amount of solar physics classroom instruction was accomplished. “Our class­room trainer was a godsend: Dr. Frank Orrall, a practicing solar physicist and observer, a highly dedicated instructor, and a man of exceptional humor and patience,” Gibson recalled. “His knowledge and enthusiasm left their marks on every one of us. Upon the conclusion of his instruction, he was presented a picture signed by each of the crewmen he instructed. The photo was one of the whole sun that clearly displayed its supergranulation, the large, nearly circular cells that crowd together on the surface. Some of the crewmen who had previously made lunar flights labeled a few of the cells with the names of craters they had studied on the moon—a way to pull Frank’s chain about how much they had learned about the sun. He loved it.”

At the beginning of every orbit, the crews had a planned set of observa­tions but also the freedom to deviate if they saw a more information-bear­ing feature or event on the sun’s surface; that is, they approached the obser­vatory operations with an open mind but not an empty one. The planned observations, which were usually sent up from the ground on a teleprinter pad, were organized into Joint Observing Programs that defined how each instrument was to be operated as a particular feature was observed, such as a solar filament, bright point, or active region. They also had a jop to cover the occurrence of a flare, a very time critical and film-consuming set of joint observations. Very useful background data on the solar state was also provided from noaa (National Oceanic and Atmospheric Administra­tion) and the Pis. Periodically they also had voice conferences with the Pis, which turned out to be useful but rather stiff because of the many restric­tions on communication with the crew. Fortunately these restrictions have softened since then, and Shuttle crews are now able to discuss joint exper­iment concerns and procedures with ground-bound observers in a less for­mal and restraining way.

The rapid rearrangement of magnetic field structures on the sun often leads to large explosive flares that are accompanied by large coronal mass ejections. Large masses of gas are hurled high into the solar atmosphere some­times with enough energy to escape the sun entirely. Occasionally some of that mass in the form of high-energy particles enters the solar wind and sub­sequently rains down on Earth, causing the northern and southern lights (the aurorae) and major disturbances in electrical distribution grids. The ejection of these masses upward through the corona was dynamic, majestic, and very rewarding if captured in the data from beginning to end. On the third Skylab manned mission, a major cme was recorded from its inception because of a real-time tip from an observatory in Hawaii that saw a large prominence start to lift off. Later in the mission, the largest such event was observed by Skylab. “This liftoff of a major arch of gas, which covered one – eighth of the solar circumference, has become an icon of the Skylab solar observations,” Gibson explained. “Much to our embarrassment, it was all recorded by the ground’s remote operation of our instruments as we float­ed in our sleep.”

The grand prize for any Skylab observer was to record the birth and life of a flare. All the clues on how and why a flare occurs are revealed by the details of its inception. “Our flare warning systems told us when a flare was occurring, but not when and where one was about to occur,” Gibson said. “Also, since the jop for a flare demanded a high burn rate of the limited film housed in most instruments, a shotgun approach was unacceptable; we had to find a way to pick off one with a rifle. The answer lay in patience and close inspection of the most energetic active region as seen in x-rays and the xuv. As the magnetic field structure of an active region became more unstable, one or more bright points would surge and pulsate in intensity. It gave one the impression of a pot of water just starting to boil. The trick was to pick the right bright point, then the right time to call a surge in brightness the early eruption of a flare. This technique practiced on the third mission rewarded us with the capture of a flare rise just as were about to conclude our obser­vations and come back home. It was rewarding yet frustrating—why didn’t we fully develop this technique earlier?”

Though certainly not designed for it, the atm took advantage of a real target of opportunity: Comet Kohoutek. The comet was much fainter than anticipated and certainly very much fainter than the bright solar features that the atm was designed to observe. “Nonetheless, we did get some inter­esting yet faint pictures, some with the coronagraph as we pointed at the center of the sun and some as we pointed the whole Skylab cluster at the comet before and after it swept around the sun,” Gibson said. “These later maneuvers were cumbersome (twenty keystrokes were required for a single maneuver) yet a testimony to the ingenuity of the ground control team that we could make any off-sun observations with the atm at all!

“In addition to what we could capture on film, we recorded on paper what our most sensitive and versatile optical instruments onboard could detect—the human eye,” Gibson continued. “The comet came out from behind the sun on the day we had scheduled a spacewalk to replace the atm film. Even with the strong filtering of our space helmet visors, the spike of brightness that pointed at the sun and away from the tail was evident. Over the next week we monitored Kohoutek, especially its sunward spike, and made sketches of what we saw, which are now on display in the Smithso­nian in Washington DC.”

Ed Gibson said, “The operation of the atm observatory was complex, exhilarating, frustrating, rewarding, tiring, and totally absorbing. All refer­ence to where the space station was over the ground would be lost; only the time remaining in daylight was of importance. The c&D panel was com­plex, demanded one’s full attention, and invited errors—even after all the effort that went into its design. I sometimes forgot some of its nomenclature, even though I was central in the design process. Some of the readouts were in decimal (base ten) and some were in octal (base eight), which could also cause confusion. The combined procedures were sometimes very complex or required alerts and timers to remind the observer of actions to take or inter­locks to make sure the some actions were not taken. During design we all tried our best to put these alerts, timers, and interlocks in place, but we fell short of optimum. Also the more an observer knew about solar physics, the larger the dilemma he faced: ‘Do I use some of our valuable time in daylight to search the sun for potentially more rewarding targets than sent up from the ground, or do I just punch the buttons on cue as requested?’ The com­promises made were often followed by many could-of’s and should-of’s.

“And yet, as the weeks went by a simplicity of operations emerged for me: If one fully understood the capabilities of each instrument, the physics of the sun’s surface, and the needs of each pi, the jops could be pushed into the background. The task really became one of matching the state of the sun’s surface with the capabilities and needs of each instrument; that is, the sheet music (jops) were put away and the atm played by ear (full utilization of one’s knowledge and intellect). Of course, I never took this extreme lat­itude on those days that the atm was scheduled to be operated. However, on Sundays, our day off, I chose to give the Pis some bonus data and operate the observatory in this way. I felt somewhat like a piano player in the silent movie theater; the instrument was played to match the visible action. After six to seven continuous orbits of observation, I felt exhilarated yet drained, rewarded yet frustrated by what was left undone.

“Of course, each of us could have performed better with more in-flight time, more training, additional displays and interlocks, and more direct com­munication with the ground scientists. Even so, the atm observatory oper­ations were a milestone that far surpassed the contributions that a scientif­ic operator in orbit had so far demonstrated and set the bar high for future human utilization on space missions.”

Despite the extraordinary effort, sizeable investment, and success of the atm solar observatory, the question remains: For future solar observatories in Earth orbit, should not the observers and instrument operators remain on the ground? After all, several unmanned solar observatories have flown since the atm and made exceptional scientific contributions. Gibson believes the answer depends on the nature of the flight opportunity, the seriousness with which a manned solar observatory mission is approached, and sever­al other factors.

Certainly electronic data collection capabilities and air-ground teleme­try rates have seen explosive growth in the past few decades. Also, except for repair and instrument upgrades, such as utilized on the Hubble Space

Telescope, the expense, extra complexity, use of less-than-fulltime and best – qualified solar physicists as observers, and other restrictions of manned mis­sions argue in favor of the observer remaining on the ground. However, if a manned mission will be in orbit and solar observations can be accommo­dated, the lessons of atm are applicable. The International Space Station might present this type of opportunity — if it can be continuously manned by six to eight crewpersons in total with at least three of them full-time, best-qualified solar physicists who are devoted 99 percent to observations. This situation will not likely become a reality unless cheap, frequent, and dependable transportation to and from iss becomes a reality.

The extrapolation of the lessons of atm suggests the inclusion of:

A routine observations program with a prioritized shopping list of targets of opportunity and the freedom to modify operations as judged best by the operator.

A dedicated observatory with round-the-clock operations and stable solar pointing on the day side of the orbit.

Full-time dedicated observers who are best qualified to operate the observatory whether in flight or on the ground.

Dedicated continuous communication loops with ground scientists for two-way, free exchange of data and commands.

Stability, instrument resolution, and display resolution that match­es the best available capability (currently approaching 0.1 arc second).

Instruments that synergistically cover the visible down to the x-ray range of wavelengths.

At least one instrument that observes the sun’s magnetic field, which drives all solar phenomena in and above its surface.

At least one instrument that observes the Doppler shift of several wavelengths to detect line-of-sight velocities at various heights in the solar atmosphere.

Onboard quick-look capability for most data sent to the ground.

“Unfortunately, considering our current manned spaceflight programs and proficiency, it is not likely that the opportunities and capabilities for a manned solar observatory are likely to materialize in the near future,” Gib­son said. “Thus, the atm mode of operation should be viewed as a rare mile­stone that will not be soon duplicated or surpassed.

“However, two general conclusions can be drawn from the atm experi­ence. First, mental challenges of the type offered by the atm operations are essential on long-duration flights if for no other reason than for intelligent and motivated crewmembers to retain their mental sharpness and positive outlook. Second, there is no good reason that Nobel Prize-quality science, utilizing the space environment, cannot be accomplished in an orbiting lab­oratory just as we realize in our best laboratories here on Earth.”

Garriott would prefer a more modest (and perhaps realistic) goal for the scientifically trained crewmember. From his perspective, and thinking in terms of the next fifty years or so, spaceflight is still expected to be a mar­velous, but seldom encountered, personal opportunity. It seems more like­ly to him that scientifically trained people will be most valued as general­ists and not specialists in one (or even two) disciplines. They will be needed as observers working in close cooperation with the best researchers around the world, helping them in conducting their specialized activity. This is not unlike the roles of the Skylab science pilots but extended as hardware capa­bilities and knowledge expands. While Nobel-competent astronauts are not to be excluded, he believes their “Ah-ha” insights leading to new scientific discoveries and even a Nobel nomination are more likely to arrive in quiet contemplation near their home office or in team meetings with their fellow specialists in interdisciplinary discussions on the ground.