By William K. Douglas, M.D., Astronaut Flight Surgeon, NASA Manned Spacecraft Center.


This paper describes some of the operational aspects of the medical support of the two manned suborbital space flights, designated Mercury-Redstone 3 and Mercury-Redstone 4. The results of the medical investigative procedures are reported in paper 3 of the present volume and in reference 1. These operational aspects can be conveniently divided into three phases:

(a) The early preparation period beginning about 3 days before a launch and concluding about T -12 hours
(b) The immediate preflight preparation
(c) The debriefing period

Preparation of the Pilot

Part of the philosophy behind the decision to execute manned suborbital space flights was to provide experience and practice for subsequent orbital flights. In light of this philosophy, it was decided that during suborbital flights all preparations will be made for the orbital flight. This explains the reason for such things as the low residue diet and other seemingly inappropriate steps in the preparation and support of the pilot.

Three days before the planned launch day, the pilot and the backup pilot start taking all of their meals in a special feeding facility. Here, a special low residue diet is provided. Preparation of this diet is supervised by an accredited dietitian, and the actual preparation is performed by a cook whose sole duty during this period is to prepare these meals. One extra serving of each item is prepared for each meal. This sample meal is kept under refrigeration for 24 hours so that it will be available for study in the event that the pilot develops a gastrointestinal illness during this period or subsequently. An effort is also made to assure that several people eat each meal so that an epidemiological study can be facilitated if necessary. The menu for these meals was provided by Miss Beatrice Finklestein of the Aerospace Medical Laboratory, Aeronautical Systems Division, U.S. Air Force Systems Command. The diet is tasty and palatable as is shown in table 5-I which gives a typical day's menu. It has caused no gastrointestinal upsets and is well tolerated by all persons who have consumed it. In order to assure that it would be well tolerated, all of the Mercury astronauts consumed this diet for a 3-day period during one of their visits to Wright-Patterson Air Force Base in one of the early phases of their training program. The use of a separate feeding facility provides the ability to control strictly the sanitation of food preparation during this preflight period. Such control could not as easily be exercised if meals were taken in a community cafeteria.

During this 3-day period before the launch day, the pilot lives in the Crew Quarters of Hangar "S" which is located in the industrial complex of Cape Canaveral. Here he is provided with a comfortable bed, pleasant surroundings, television, radio, reading materials and, above all, privacy. In addition to protection from the curious-minded public, the establishment of the pilot and the backup pilot in the Crew Quarters also provides a modicum of isolation from carriers of infectious disease organisms. This isolation is by no means complete and it is not intended to be. An effort is made to provide isolation from new arrivals in the community, however. It is felt that a certain amount of natural immunity has been acquired by the pilots in their day-to-day contacts with their associates at the launch site. Contact with visitors from different sections of the country might, however, introduce a strain to which no immunity had been acquired. Consideration was given at one time to the use of strict isolation techniques during this preparation period, but this thought was abandoned because of its impractibility. The pilot plays a vital role in the preparations for his own flight. In order to be effective, a period of strict isolation would have to last for about 2 weeks; thus, the services of these important individuals would be unavailable for that period. Further, it was felt that a 2-week period of strict isolation would constitute a psychological burden which could not be justified by the results obtained. As mentioned previously, the pilot and his colleagues play a vital role in the preparation of the spacecraft and its launch vehicle for the flight. This period begins about 2 weeks prior to launch and continues up until the day before the launch. During this period of time, the pilot, on occasions, must don his full pressure suit and occupy the role of "capsule observer" during the course of certain checkout procedures. Advantage is taken of these exercises to perform launch rehearsals of varying degrees of sophistication. The most complete of these exercises occurs during the simulated flight which takes place 2 or 3 days prior to the launch. This dress rehearsal duplicates the launch countdown in event time and in elapsed time, but it occurs at a more convenient hour of the day. It not only enables those responsible for the readiness of the spacecraft and the launch vehicle to assure themselves of the status of these components, but it also allows those directly concerned with the preparation and insertion of the pilot to assure themselves of their own state of readiness. Finally, these exercises provide a certain degree of assurance and familiarity for the pilot himself.

On the evening before the flight, the pilot is encouraged to retire at an early hour, but he is not required to do so. The pilot of MR-3 spacecraft retired at 10:15 p.m. e.s.t., and the pilot of MR-4 spacecraft retired at 9:00 p.m. e.s.t. In both cases, the pliots fell asleep shortly after retiring without benefit of sedatives or drugs of any kind. Their sleep was sound, and insofar as they could remember, was dreamless. The medical countdown for MR-4 flight called for awakening the pilot at 1:10 a.m. e.s.t. (table 5-II). This time was 65 minutes later than the wake-up time called for in the MR-3 countdown. Time was saved here by allowing the pilot to shave and bathe before retiring instead of after awakening in the morning. Another 15 minutes was saved by performing the final operational briefing in the transfer van on the way to the launch pad, rather than after arrival as was done in MR-3 flight. When they were awakened on the morning of the launch, both pilots appeared to have been sleeping soundly. There was no startle reaction on awakening, and the immediate postwaking state was characterized by eager anticipation and curiosity as to the progress of the countdown. After awakening, the pilots performed their morning ablutions and consumed a high protein breakfast consisting of fruit, steak, eggs, juice, and milk. No coffee was permitted during the 24-hour period preceding the flight because of its tendency to inhibit sleep. No coffee was permitted for breakfast on launch morning because of its diuretic properties.

After breakfast, the pilots donned bathrobes and were taken into the physical examination room where the preflight physical was performed. This examination is distinct from that conducted for the purpose of collecting background scientific data, which was performed by several examiners 2 to 3 days prior to the flight. This early examination is reported in paper 3 of the present volume and in reference 1. The physical examination performed on the morning of the flight was designed to ascertain the pilot's fitness to perform his mission. It was designed to discover any acute illness or infirmity which might contraindicate the flight.

These examinations failed to reveal anything of significance. The physiological bradycardia (pulse rate 60 to 70) and normotensive (blood pressure 110/70) state both give some indication of the calm reserved air of confidence which typifies both of these pilots. It is important to emphasize at this point that no medication of any kind was consumed by either of these pilots during the several days preceding the launch. Following the preflight physical examination, each of the pilots was given a short battery of psychological tests. In the case of the MR-4 pilot, it was possible to provide a short interview by a psychiatrist. Both the testing and the interview were part of the medical investigative program and are reported in paper 3 of the present volume and in reference 1. Suffice it to say at this point that no abnormalities were detected.

The next step in the preparatory procedures was the application of the biological sensor harness (figs. 5-1 and 5-2). This harness is described in detail in reference 2. The only difference between the sensors used in MR-3 and MR-4 flights was an alteration of the respiration sensor housing for the MR-4 flight to accomodate the microphone of different configuration used in the later flight. The surface of the electrode next to the skin is prepared with an adhesive material identical to that found on conventional adhesive tape (elastoplast adhesive). This preparation must be done at least 15 minutes in advance since the solvent for the adhesive is irritating to the skin and must be given ample opportunity to evaporate before the sensor is applied. The dermal surface of this electrode is first filled with bentonite paste and the electrode is applied directly to the skin. The skin is first prepared by clipping the hair where necessary and by cleansing with surgical detergent (FSN 6505-116-1740). The sensor locations have been previously marked on all Mercury pilots by the use of a tiny (about 2 millimeters in diameter) tattooed dot at each of the four electrode sites. After the sensor is applied to the skin, the uppermost surface of the screen is covered with the bentonite paste and a small square of electrician's plastic tape is applied over the opening in the disk. The entire electrode is then covered with a square of moleskin adhesive tape. This assembly becomes, then, a floating electrode. The electrician's tape serves to retard somewhat the evaporation of water from the bentonite paste.

Typical Electrocardiograph Floating Electrode

Figure 5-1.   Three views of a typical electrocardiograph floating electrode as used in Project Mercury. The surface of the electrode applied to the skin (right) is first painted with adhesive and then filled with bentonite paste.

The deep body temperature probe (fig. 5-2) is simply a flexible rubber-covered thermistor. Since it is difficult, if not impossible, to sterilize this probe without causing deterioration of the device, each pilot is provided with his own personal sensor harness. This same harness is used in all practice exercises in which the individual participates. It is simply washed with surgical detergent after each use.

Respiration Sensor and Deep Body Temperature Probe

Figure 5-2.   Respiration sensor (left) and deep body temperature probe (right).

After the harness is applied, the integrity of the sensors is checked by the use of a modified Dallon Cardioscope (fig. 5-3). With this device, both electrocardiographic leads can be displayed on the oscilloscope, and the amplitude of the QRS (Q-wave, R-wave, S-wave) complex can be measured roughly by comparing it with a standard 1-millivolt current. The integrity of the respiration sensor can also be demonstrated by displaying the trace on the oscilloscope. No effort is made to calibrate the respiration sensor at this time. The temperature probe is also checked by use of a Wheatstone bridge.


Figure 5-3.   Cardioscope used to check out the biosensor harness. The lead into the suit is shown on the lower right, and the switching box to display respiration and temperature is shown on the lower left.

After the sensors have been applied, the pilot moves to the pressure-suit room where he dons his suit. Since the most uncomfortable period of the countdown is that time spent in the suit, a check is made with the blockhouse to determine the status of the count. If there has been a delay or if one is anticipated, the suit donning is held up at this point. At some convenient time during the day before the flight, the suit has been assembled and inflated to 5 psi, and a leak check is made. The "static" leak rate is determined at this time. These values were 190 cc/min and 140 cc/min for the MR-3 and MR-4 flights, respectively. After the pilot has donned his suit, he is placed in a couch in the pressure-suit room and the suit is again inflated to 5 psi. The ventilation flow is then turned off and a "dynamic" leak rate is obtained by reference to the flow of oxygen necessary to maintain this pressure. The dynamic leak rate for the MR-3 flight was 400 cc/min; for the MR-4, it was 175 cc/min. The term "leak rate" in this dynamic situation is used rather loosely since it encompasses not only the actual leak rate of the suit but also the metabolic use of oxygen. Exact measurement of this rate is further complicated by the presence of a breathing occupant of the suit; changes in the occupant's volume occasioned by respiratory movements are reflected as changes in the flow rate, but a rough estimation is possible even under these circumstances.

After the pilot is laced in the couch but before the dynamic leak rate is determined, the torso zipper of the suit is opened and the amplifier for the respiration sensor is delivered. With the visor closed, and with the microphone positioned as for flight, the amplifier is adjusted to provide a signal strong enough to be easily observed but not so strong as to overload the spacecraft telemetry equipment. Once the dynamic leak rate has been determined, the suit is not again disturbed except to open the helmet visor. No zippers are permitted to be loosened from that time on. Upon completion of the suit donning procedure, the pilot returns to the examination room where the biosensors are again checked on the oscilloscope. This would detect any disturbance created by the donning of the suit, and permit it to be corrected at this point rather than later.

If the medical count and the main countdown are still in agreement, a portable ventilating unit is attached to the suit and the pilot and insertion team proceed to the transfer van. Upon his arrival at the transfer van, the onboard ventilation system is attached. The integrity of the biosensors is again checked by use of a Model 350, 8-channel Sanborn recorder. The Sanborn recorder remains attached to the pilot from this point on, and a continuous recording of the measured biological functions is started. A sample record taken while the van was in motion is shown in figure 5-4.

Sample Record

Figure 5-4.   Sample record from Sanborn recorder taken in the transfer van. The van was in motion at the time this recording was made.

Upon arrival at the launch site, the two final strips of record are obtained from the Sanborn recorder and delivered to the medical monitors at the blockhouse and at the Mercury Control Center. Both of these records contain a 1-millivolt standardization pulse, and are utilized by the monitors o compare with their records as obtained from the spacecraft. When notified to do so by the blockhouse, the portable ventilating unit is reattached. The pilot, flight surgeon, pressure-suit technician, and a pilot observer (astronaut) leave the transfer van an proceed up the elevator to the level of the spacecraft.

At this point, the preparation of the pilot ceases and the actual insertion of the pilot into the spacecraft commences. After the pilot climbs into the spacecraft and positions himself in the couch, the pressure-suit technician attaches the ventilation hoses, the communication line, the biosensor leads, and the helmet visor seal hose, and finally, he attaches the restraint harness in position but only fastens it loosely. At this point, the suit and environmental control system is purged with 100-percent oxygen until such a time as analysis of the gas in the system shows that the oxygen concentration exceeds 95 percent. When the purge of the suit system is completed, the pressure-suit technician tightens the restraint harness; the flight surgeon makes a final inspection of the interior of the spacecraft and of the pilot, and the hatch installation commences. During the insertion procedures, it is the flight surgeon's duty to monitor the suit purge procedure and to stand by to assist the pressure-suit technician or the pilot in any way he can. The final inspection of the pilot by the flight surgeon gives some indication of the pilot's emotional state at the last possible opportunity. The flight surgeon during this period is in continuous communication with the blockhouse surgeon and is capable of taking certain steps to analyze the cause of biosensor malfunction, should it occur. No such malfunctions occured during the course of these two flights. After hatch installation is completed, the flight surgeon is released and proceeds to the forward medical station where he joins the point team of the land recovery forces.


After a successful launch, the flight surgeon leaves his position on the point team and proceeds immediately to the Mercury Control Center. Here he follows the progress of the recovery operations until it is clear where his services will be needed next. In the event the pilot is injured or is ill, the flight surgeon is taken by air to the aircraft carrier in the recovery area. If it is clear that the pilot is uninjured, as was true for MR-3 and MR-4 flights, the flight surgeon joins the debriefing team and is flown to the medical care and debriefing site at Grand Bahama Island, British West Indies. During this time, the pilot is undergoing a preliminary physical examination and debriefing aboard the carrier. In both of the flights under discussion, the debriefing team arrived at Grand Bahama Island about 30 minutes before the pilot who was flown there from the carrier. The debriefing site is a two-room prefabricated building with an adjacent heliport. The heliport is provided in the event it is more convenient, or is necessary by virtue of his physical status, to carry the pilot from the surface vessel to the debriefing site by helicopter.

Immediately upon their arrival at Grand Bahama Island, the pilots were taken to the debriefing building where the flight surgeon performed a careful physical examination. Here again, the purpose of this examination was not so much to collect scientific material as to assure that the pilot was uninjured and in good health. When this preliminary examination had been completed, the pilots were examined by a surgeon. No evidence of injury was found by this second examiner. Next, an internist examined the pilots. Laboratory specimens (blood and urine) were obtained and the pilots were examined by an ophthalmologist, a neurologist, and a psychiatrist. Chest X-rays (anteroposterior and right lateral) were taken. The results of all of these examinations were, in the main, negative and have been reported in paper 3 of the present volume and in reference 1. Upon completion of the physical examination, the pilots were turned over to the engineering debriefing team.

The original plan for the pilot's postrecovery activities permitted him to remain at Grand Bahama Island for 48 hours after his arrival. This period was believed to be necessary to permit full and adequate recovery from the effects of the flight. In the case of the MR-3 flight, it was possible for the pilot to remain for 72 hours. The last day of this period was devoted to complete rest and relaxation. The additional 24-hour period was occasioned by the scheduling of the postflight press conference and public welcome in Washington, D.C. It was quite apparent that the postflight rest period was beneficial to the pilot. There is no objective measurement of this, but the day-to-day observations of the pilot showed him to be benefited by this relative isolation. In the case of the MR-4 flight, the pilot seemed to be recovering rapidly from the fatiguing effects of his flight and the postflight water-survival experience. His fatigue was more evident when seen 12 hours after his arrival at Grand Bahama Island than that observed in the pilot of the MR-3 flight when seen at the same time. On the following day, however, the MR-4 pilot seemed to be at about the same level of recovery as had been observed in the MR-3 pilot. For this reason, it was decided to permit the pilot of the MR-4 flight to return to Cocoa Beach, Fla., for a press conference at a time some 18 to 20 hours before that called for in the original plan. No evident permanent effects of this early return can be described, and the pilot performed well in his public appearances; but his fatigue state was much longer in dissipating as he was seen in the days subsequent to the flight. Again, this slower recovery cannot be demonstrated with objective findings, and must be accepted only as a clinical observation of the writer.

Concluding Remarks

The flight surgeon's activities and duties in support of two manned suborbital flights have been described and certain observations of the flight surgeon have been recorded. In summary, it is important to point out three items.

(1) During the 12-hour period preceding the launch, it is vital that the preparation of the pilot follow the coutdown with clocklike precision. This precision becomes more urgent as the time approaches for insertion of the pilot into the spacecraft. In order to accomplish this precision, it is necessary to practice the preparation procedures time and time again. Time-motion studies are necessary. In the training program for the Mercury flights, each insertion of an astronaut into the centrifuge was performed just as if it were a real launch. At times during the checkout of the spacecraft, it was necessary to insert an astronaut into the spacecraft in an altitude chamber. Each of these events was conducted as for a launch. Even with these many opportunities to practise and perfect techniques, some changes were made after the MR-3 flight for the MR-4 flight. The fact that no delays were ocasioned by the preparation procedures attests to the value of these repeated practice sessions

(2) Very early in the planning for manned space flights, it was decided to train a backup man for each position in the medical support complex. A backup astronaut was always available; a backup flight surgeon was trained; and even a backup driver for the transfer van was available. These backup men not only provided substitutes of ready accessibility, but also permitted each person involved to get some rest on occasion. The primary individual was then capable of performing his task in an alert and conscientious manner on the actual day of the launch.

(3) In future manned flights, the planned 48-hour minimum debriefing period should be observed and even extended to include a 24-hour period of complete rest if indicated by the stresses experienced during the flight.


  1. Jackson, C. B., Douglas, William K., et al.: Results of Preflight and Postflight Medical Examinations. Proc. Conf. on Results of the First U.S. Manned Suborbital Space Flight, NASA, Nat. Inst. Health, and Nat. Acad. Sci., June 6, 1961, pp. 31-36.
  2. Henry, James P., and Wheelwright, Charles D.: Biomedical Instrumentation in MR-3 Flight. Proc. Conf. on Results of the First U.S. Manned Suborbital Space Flight, NASA, Nat. Inst. Health, and Nat. Acad. Sci., June 6, 1961, pp. 37-43.

Table 5-I.   Sample Low-Residue Menu

[Third day prior to space flight]

 Orange juice 4 ounces
 Cream of wheat 1/2 cup, cooked
 Cinnamon or nutmeg Few grains
 Scrambled eggs 2
 Crisp Canadian bacon 2 to 3 slices
 Toast (white bread) 1 to 2 slices
 Butter 1 teaspoon
 Strawberry jelly 1 tablespoon
 Coffee with sugar No limit
 Chicken and rice soup 1 cup
 Hamburger patty 3 to 4 ounces
 Baked potato (without skin) 1 medium
 Cottage cheese 2 rounded tablespoons
 Bread (white) 1 to 2 slices
 Butter 1 teaspoon
 Sliced peaches (canned) 1/2 cup
 Coffee or tea with sugar No limit
 Tomato juice 4 ounces
 Baked chicken (white meat) 4 ounces
 Steamed rice 1 cup
 Pureed peas 1/2 cup
 Melba toast 1 to 2 slices
 Butter 1 teaspoon
 Lemon sherbet 3/4 cup
 Sugar cookies 2 to 3
 Coffee or tea with sugar No limit

Table 5-II.   A Comparison of the Medical Countdown of MR-3 and MR-4 Flights

Event T – time
(MR-3 Flight)
(MR-3 Flight)
T – time
(MR-4 Flight)
(MR-4 Flight)
Physical examination
Sensor application
Suit donning
Pressure check
Enter transportation van
Arrival at launch pad
Ascend gantry
Begin insertion
1 Planned time during countdown according to the launch document
2 Actual time event occurred

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