Skylab 2 Crew Observations and Summary

JOSEPH P. KERWIN

It is really nice to talk to the other crews and find out how consistent one’s descriptions of the signs and symptoms of weightlessness are. The environment is the same so it is just a matter of describing it in different words or different similes.

There are two major themes that run through my mind. Number one, of course, is that it really is extremely clear to an individual, when he is in weightlessness, that rather profound changes are rapidly taking place in his body. One feels this strange fullness in the head and this sensation of having a cold, and one sees the puffy look on the faces of his fellow crewmen and hears their nasal voices. He feels his body assume the strange posture that one has in weightlessness, with the shoulders hunched up, the hands out in the front and the knees bent. Sleeping in that posture is not comfortable initially but every time one relaxes, one’s body goes back to that posture. One can almost see the fluid draining out of the legs of his fellow crewmen making them look little and skinny like crows’ legs, and one knows that one’s physiology is changing. But that wasn’t the primary theme. The primary theme was one of pleasant surprise at all the things that didn’t change, at all the things that were pleasant and easy to do. As Crew Commander Pete Conrad pointed out, we lost a few bets up there because of our appetites. The very first system that gave us a pleasant surprise was the vestibular system. All of us keep talking about it because not only was it so different from what was expected but it remains, subjectively, one of the primary memories that one gets from this "Alice in Wonderland" world of weightlessness.

Our crew was fortunate enough not to run into the motion sickness problem in any clinical or full-blown form. Therefore, among our first pleasant or different impressions was the impression of a very changed relationship between ourselves and the outside world and, I would say there was no vestibular sense of the upright whatsoever. I certainly had no idea of where the Earth was at any time unless I happened to be looking at it. I had no idea of the relationship between one compartment of the spacecraft and another in terms of a feeling for "up or down"; this has some peculiar effects when one passes from one compartment into the other and walls turn into ceilings and ceilings turn into floors in a very arbitrary way. But all one had to do is rotate one’s body to the more familiar orientation and it all comes to right. What one thinks is up, is up. After a few days of getting used to this, one plays with it all the time; one just stands there and does a slow roll around his bellybutton. The feeling is that one could take the whole room and by pushing a button, just rotate it around so that the screens up here would be the floor. It’s a marvelous feeling of power over space—over the space around one. Closing one’s eyes made everything go away. And now one’s body is like a planet all to itself, and one really doesn’t know where the outside world is. The first time I tried it, my instinct was to grab hold of whatever was nearest and just hang on, lest I fall. It was the only time in the mission when I had anything like a sensation of falling. I was telling that to my wife, and she pointed out that that’s like the reflex that a baby has. When you begin to drop it, it just reaches out and clutches. And we thought, it would be nice to write a story about a sort of evolution of the human being in zero-g, because one certainly gets used to it in a hurry and it certainly is different. You will read in great detail in chapter 11 about the third and last effect of weightlessness, the effect on the vestibular system. Ed Gibson alluded to this effect in chapter 3 where he states that rotation and head movement in weightlessness do not elicit motion sickness. I don’t believe Dr. Graybiel will state it quite that strongly, but certainly we never reached the threshold. And that was most surprising.

Another very pleasant surprise was our ability to maintain physical fitness—our ability to maintain the same exercise level as we had been maintaining on the ground. I really don’t think that any of us expected that before the flight as we felt that the combination of reduced mechanical efficiency and muscular deterioration or atrophy was definitely going to reduce our ability to work on the bicycle. Well, we were wrong again. Once we had mastered the technique or the mechanics of how to ride a bicycle in a weightless condition, which took us about 10 days, we found that essentially we remained at the preflight baseline throughout the mission. I believe some of the crewmen on the subsequent flights increased their ability to do that particular task, simply through a training effect, and that was a very pleasant surprise.

To me, the most astonishing thing was our ability and desire to pack in the groceries, and there’s a long preflight history to that. We fought and scratched with the Principal Investigators on that diet for 4 or 5 years. We finally settled on an in-flight diet estimation, which kind of went like this: We had several 6-day periods of food intake measurement prior to the flight. These data were taken and were modified by certain standard height/weight/surface area tables, and so forth, to get a best estimate of our average caloric intake, and then we subtracted 300 kilocalories from that. Most of us were certain that even that amount of food was going to be too great. And lo and behold! We discovered that after a few days of decreased appetite in flight we were able to eat all our food. Indeed, as the missions progressed the amount of food the crew was allowed to eat increased and their exercise increased, they were essentially eating the same amount of food as they ate on the ground. That to me is a mystery. I still don’t understand how in an environment in which certainly muscular work is reduced, the caloric demand and the relationship between caloric intake and body weight remain just about the same as they do on the ground, I think that’s a very interesting problem that we haven’t yet been able to solve.

The first step in a rational description of the physiology of weightlessness is a medical history and physical examination. This we follow with laboratory findings and the clinical course of the—I hate to call it a disease because it’s not—but, of this change. Such a description has many uses, not the least of which will be to permit the diagnosis of disease in weightlessness, where the presenting signs, symptoms, and so-called normal laboratory values are going to be different. Now our sample population has been much too small to have experienced significant illness in orbit, and it’s been too small to allow us to predict changes in the incidence of diseases or the course of diseases due to the weightless environment. I think this is a matter of time and that these are the kind of things we need to know in order to fly frequently and to fly for long durations and to make space flight in the Shuttle era and beyond a routine event, because we do not want to place physical limitations on our crews and our visiting scientists. There are many examples that come to mind: for instance, when you fly older people, what is the rate at which they wash out nitrogen when they prebreath? Does it change merely as a function of age, or is it because physical fitness and obesity come into the picture, too? We don’t know. That’s a small data point that’s going to be operationally important to us when we begin to fly people in their 50’s and their 60’s. I think the first step is to use animal subjects to make the measurements necessary to clear up the picture, and to observe the response of animals to various challenges. I think the effect of hypoxia in weightlessness would be very interesting to observe. Certainly, I’d love to see whole generations of animals reared and exposed to weightlessness for their entire lifespan, to see how far this evolutionary process will really go. And I think eventually we will get to the point where we will dare to study disease states, first in animals and then in human beings. I think that by studying a disease in weightlessness, we will learn more about both the environment and the disease. There are many possibilities: from fundamental studies on coronary and pulmonary perfusions, to bone and soft tissue healing, to the effect of drugs, hypoxia, and radiation, to observations on the course of stasis ulcers and to how does edema in right heart failure behave in this environment. If we can make fundamental advances in any one of those subjects, we’ll pay the freight for the whole medical program. I feel that an imaginative approach to medical research will have an opportunity to be used in the 80’s.

As a human subject for this kind of research, I would like to conclude with a few observations. We had a super relationship with the medical team on Skylab. Each and every investigator was competent, efficient, and thoughtful of us, the subjects. Only en masse, were they ever a bit overwhelming, as when on recovery day everybody wanted that significant data—"right now." Medical research on Skylab has helped us to document that human beings can operate efficiently in space. It’s this fact, rather than medical research per se that will justify continuation of manned space programs. It appears that man’s potential efficiency in zero-g is as high as it is any place else. The degree to which this potential is realized is a function of the experience and training of the crew and of the degree to which their needs are met in-flight. Thus, the function of medicine is not only to discover those needs but to meet them. And the research program we design must hamper the crew’s efficiency as little as is possible and still get the data.

 

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