The Skylab Medical Plan

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

44- Weitz assists Kerwin with a blood-pressure cuff.

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.