Category HOMESTEADING SPACE

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.

You lost a crewman? How could you lose a crewman inside a spacecraft?

Skylab III Mission Announcement

The third manned Skylab mission is scheduled for launch November io
at 11:40 a. m. EST for a mission duration of 60 days or more,

William Schneider, Skylab Program Director, announced.

The mission will be planned as a 60-day open-ended mission
with consumables aboard to provide for as many as 85 days.

Mission extensions would be considered on the 56th, 63rd, 70th and 77th days of the
flight based on the medical well being of the crew,
consumables and work load. The extension of the mission to
85 days would substantially increase the scientific return.

NASA—Press Release, 26 October 19/3

Skylab ill was to break new ground in mission duration and accomplish­ments. And it would do it with an all-rookie crew. When they launched, the three crewmembers did not have a single day of spaceflight experience amongst them. But when they returned, each would have spent more con­tinuous time in space than any other human being.

For the mission’s commander, Jerry Carr, and its pilot, Bill Pogue, the Skylab assignment started off as practically a consolation prize. “I was ten­tatively scheduled to fly on Apollo 19,” Carr recalled. “Our crew was to be Fred Haise, the commander; Bill Pogue, the Command Module pilot; and

me, the Lunar Module pilot. We got started on that assignment and began our training program. Then if my memory serves me correctly, it was around 1970, early 1970 or so, when it was decided that Apollos 18, 19, and 20 would be canceled. So that was a bad day at Black Rock for the three of us. We had lost our opportunity to go to the moon.

“We moped around for quite a few weeks,” he said. “Then Tom Stafford called me into his office and informed me that I was to be the command­er of the third Skylab mission and asked, ‘Do you think you can work with Bill Pogue and Ed Gibson?’ And I said, ‘Of course I can.’ At that time they took us off our roles as the backup crew for Apollo 16 and put another crew in there, and we began focusing on the Skylab mission.

“I was delighted to get a seat, and I was absolutely floored that they would select me to be a commander because there hadn’t been a rookie command­er at NASA since, what was it? I guess it was probably Armstrong on Gemi­ni 8. And so I was really flabbergasted to be selected and very happy to do it. What delighted me the most was that I was going to be working with Al Bean, Pete Conrad, and people like that again, which was really a won­derful thing.”

Ed Gibson recalled: “When assigned to the mission, I knew I was in fast company. Bill Pogue initially appeared to be just an average mild-mannered mathematician, who he had been; but he was also once grounded for flying too low behind enemy lines, was an Air Force test pilot, and flew with the Thunderbirds. He is a sharp, aggressive guy. Jerry Carr had a good educa­tion in aeronautics and was a Marine aviator, which pretty much said it all. The all-rookie crew aspect didn’t faze me. I was just happy to get a seat, and flying with guys I really respected. In retrospect, I lucked out. I got to do great science, be fully immersed in all aspects of astronaut activities, and fly high-performance aircraft. It just couldn’t get any better than that!”

While the three rookie astronauts were excited to be getting their chance to fly, they had little idea that before Skylab ill even launched, it already had two major strikes against it—the past and the future. The strike in the future was the next great thing looming over the horizon—the Space Shut­tle program. Early development of the Shuttle was already underway by the time of Skylab, and the orbiter contract had been signed the month before the sl-i launch with a critical design review scheduled for 1975. However, the program still faced opposition in Congress. A major part of the system was a one-shot pilot-controlled landing from orbit with no go-around capability. There were those who felt that landing would be too large a challenge, par­ticularly if the pilot were suffering from space sickness. The Skylab ill crew had been made aware of how important it was that they not give the orbit – er’s enemies ammunition against the program in that respect.

The past affected them in the form of the two Skylab missions that flew before them. Both Skylab I and II had been behind their timeline early in flight. In both cases there were obvious factors that contributed to these slow starts. The Skylab I crew had to deal with the high temperatures and power shortages on a crippled spacecraft. The Skylab II crew was slowed by motion sickness. Those obvious factors, though, obscured the fact that the major cause was simply that people had to get considerable on-the-job training to efficiently perform tasks in weightlessness—especially when large habitable volumes are involved. With repetition the second crew in particular became extremely efficient and was accomplishing more than their scheduled sci­ence work by the end of their mission. While the actual factors involved in the slow starts of the first two crews would become a major issue once the third crew was in orbit, the efficiency the second crew developed over the course of the mission had an impact on the third crew while Carr and his colleagues were still on the ground.

Upon learning of the 150 percent return of the Bean crew, scientists and mission planners saw an opportunity. Clearly, they had not sent enough work for the second crew to do—and they began making sure the third crew was going to have plenty of work to accomplish. “We got to Skylab ill, which was going to be the last mission in the program,” flight director Neil Hutchinson recalled in a NASA oral history interview. “The train was leav­ing the station, and all kinds of experiments and experimenters were run­ning for a seat.”

In addition NASA decided to use the third crew’s flight to capitalize on another opportunity. In late December 1973 and early January 1974 the Com­et Kohoutek would be passing through the inner solar system. Tasking the third crew with observing Kohoutek from Skylab would let the agen­cy show off the potential of orbital astronomy by performing an unprece­dented feat—no comet had been observed from space before. “Some other training we got at the last minute included that on Comet Kohoutek,” Pogue recalled. “Early in the year it was discovered at the Hamburg Observatory in West Germany that this comet was headed toward the sun and was going to reach its perihelion about Christmas Day of 1973. There was a lot of talk about the period of the comet being about two thousand years, which led to speculation that it was actually the Christmas comet, the one cited in Bib­lical stories of the new star. At any rate, we did some studying and training for that experiment as well.”

Press releases from the time illustrate the situation that confronted the third crew.

nasa-jsc Release No.: 73-107

nasa today announced tentative plans to observe the Comet Kohoutek during the Skylab iii mission which is planned for launch on or about November у from the Kennedy Space Center. The November date is the original planned launch date for Skylab iii. The Comet Kohoutek was identified earlier this year and will be clearly visible from Earth. It is expected to be the brightest object in the night sky except for the Moon in late December and early January. Skylab’s Apollo Telescope Mount instruments, designed to obtain data on the Sun, will observe Kohoutek during its nearest proximity to the Sun late in December.

The first two major priorities of Skylab were space medicine and solar phys­ics. The third was habitability. How was a space station to be designed so that humans could live and work in it effectively?

Engineers had been designing spacecraft for human operability since the Mercury program, but they hadn’t yet made a methodical study of the sub­ject. Skylab was their opportunity because of its generous weight and vol­ume available and its long missions. The opportunity was recognized and taken.

Two experiments were submitted and approved. The first was M487, hab­itability/ crew quarters, the purpose of which was “to measure, evaluate and report habitability features of the crew quarters and work areas of Skylab in engineering terms useful to the design of future manned spacecraft.” Its lit­tle brother was M516, crew activities/maintenance study, designed “to eval­uate Skylab man-machine relationships by gathering data concerning the

crew’s capability to perform work in the zero-g environment on long dura­* * 3?

tion missions.

Plans for gathering data were made, prominently including crew voice reports and questionnaires, film and video, and measurements of how long tasks took to accomplish. Tools were provided to measure light, sound, air movement, temperatures, and forces. Procedures were tested during the smeat simulation and improved. The engineering approach suited the crews, who recognized the importance of the effort and were glad to furnish their evaluations and opinions. The experiment was continued into design. Many different types of restraints, handholds, equipment tethers, and even door openings were provided, so that the crews could show and tell which worked and which didn’t.

It’s been said by some observers that the astronauts were constantly com­plaining about Skylab systems and accommodations. Actually, they were doing their jobs. They thought it more important to describe inefficiencies and suggest solutions than to praise successes, although there was plenty of the latter, especially postflight. And the human-factors engineers behind the experiments, ably led by Bob Bond, knew how quickly memories fade and wanted the evaluations during the missions, not after. So there was a lot of air-to-ground communication on how things worked and how to make them work better.

The results, gathered over the ensuing two years into “Skylab Experience Bulletins,” filled seventeen volumes.

Two very important, unanticipated observations were made about the crews’ bodies: first, they became taller by one to two inches; second, they adopt­ed a characteristic “zero-G posture,” flexed at knees, hips, and neck. These two facts greatly affected the way the people fit into space suits and at work­stations of all sorts and led to some important recommendations for future spacecraft. One was “No Chairs!” The body doesn’t want to flex into a chair; it’s uncomfortable and unnecessary. (On the space shuttle, chairs are used for launch and entry and stowed in orbit.) Don’t make an individual crouch at a workstation by putting key instruments below his or her eye level; it’s not feasible to slump. Without gravity to help, bending over to tie your shoes is harder. And size the space suits and clothing with some extra length. Future engineers would look with interest and amusement at the photo of the fifth percentile girl beside the ninety-fifth percentile guy, and spend some extra time designing one workstation that will fit either.

If chairs are no good, how can you restrain a person to do a task? Foot restraints are the answer, and the best ones give a firm purchase that allows both hands to be occupied with the task. More casual restraints were ok for one-handed tasks.

There was quite a bit of debate before flight about whether people would feel more comfortable in a work space that looked like an Earthly room with floors and ceilings and all the signs oriented the same way, or whether in zero-G they could operate nicely on walls and ceilings, allowing space to be more effectively utilized. The answer to both questions was “yes.” The report says: “The Skylab crewmen were able to operate equipment easily from any orientation. They quickly established their own coordinate sys­tem in which the location of their feet signified ‘down.’” But the one-grav­ity architecture of the ows crew compartment was preferred to the put-it – anywhere radial arrangement in the mda. The latter was a bit disorienting when you entered it; it was ok once you’d reached your workstation. With­in a workstation everything had to be oriented to the same “up.”

Improvements were suggested in the overall layout of Skylab too. “Don’t ever put the airlock in the middle again,” was a good example. Having the airlock right on the main pathway between the systems center in the mda and the work and living center in the workshop meant that nothing could be stowed in the airlock lest it impede traffic. It also meant that if the air­lock hatch wouldn’t close after a spacewalk, the workshop became unin­habitable and the mission was over.

This work, combined with systems evaluation, resulted in a very thor­ough set of design criteria for future spacecraft, especially permanent space stations. It had some impact on Shuttle design, although Shuttle was already well into its design process when the Skylab results were promulgated in 1975. It had considerable impact on the European Spacelab module in whose development several Skylab astronauts participated. And it significantly assisted the Russians in the design of Mir, although no Americans were invited to take part directly in that space station’s initial design. Later, of course, NASA astronauts would live and work with their Russian counter­parts aboard Mir.

In the eighties the Skylab human-factors lessons and several other sources

were combined into one massive habitability design book, NASA Standard 3000. It was used in the design of Space Station Freedom and its successor, iss. What other lessons from Skylab were not learned by the designers of iss is material for another book.