[24] The 2-week duration of the mission and the need for the occupants to rely on their internal resources, rather than continually relate to the earth, determines many of the Human Factors requirements. This fact can be best illustrated by comparing this proposed circumlunar flight with the Mercury flights now contemplated. The Mercury capsule flight can be better compared to a high performance aircraft program in that computation and much of the control can be effected from the ground. The Mercury Astronaut is in nearly continuous touch with the ground stations and has need for only limited provisions for habitability because he need neither eat, sleep, eliminate waste, nor find relaxation during programed missions. In contrast to this, the lunar astronauts are more in the positions of men on a long voyage. They must have provisions for eating, sleeping, waste evacuation, recreation, care of their health, as well as a more complete work space since the ground rule of the maintaining command control aboard the vehicle has been established. Furthermore, the long period of relative isolation of the group will threaten mental disturbance unless some freedom of movement and relief from boredom can be arranged by the provision of a variety of tasks. The size and dimensions of the capsule dictate that the crewman will be living under unsatisfactory small group society rules. This fact will require very thorough study and provision within the capsule in order that the problems of crew relationship may be alleviated. The duration of flight and the fact that man must face weightlessness and isolation for many consecutive days raise the question of crew selection to assure compatibility.

Many of the above noted items are subject to solution through relatively straightforward mechanical and human engineering studies. One item, however, is not now considered to be in such good shape: that is the problem of radiation in space, particularly during solar flares.

Figure 1 lists the crew and environment guidelines. Briefly, these guidelines state that we should plan on having a "shirt sleeve" environment for a minimum crew of three men and that we must design the vehicle (and the mission) to provide adequate radiation protection for the crew.

The magnitude of the step proposed in the cislunar flight over that accomplished in Mercury and the demand for placing the control center of [25] the operation in the capsule under control of the astronaut require a rather extensive biological program to be accomplished prior to the time when the cislunar flight will be undertaken. These experiments should go along with the other developmental tests and data gathering flights which are planned as intermediate steps in the development program. This discussion will be confined to an outline of the types of experiments required within the life sciences area, assuming that there will be an equal number of experiments required in both the physical data gathering and the engineering test programs. The life sciences program can be divided into roughly four categories. They are as follows:

(a) Psychophysiological (Habitation). This area will include a study of the provisions for quarters and working area. This will include a study of the equipment that is placed onboard to assure that this equipment will allow for crew duties to be adequately performed. Also included will be the problem of crew association, namely that of small group sociological problems and the methods of the small group working together for such a venture. Here also, studies on the problems of sensory deprivation should be made. The problems of earth separation should be considered. A study of the methods of attacking boredom must be made. These studies should result in the determination of the magnitude of the problems in this area and should dictate the directions for solution such as the manner of work schedules, numbers of crew, relaxation, and entertainment provisions, and any other approaches to alleviate or ameliorate these as problem areas.

(b) Physiological. Since this flight is to be a large extension of any experience we have had to date, it will be necessary to have studies which are primarily in the field of weightlessness and its effect over chronic exposure studies. These will include such things as studies of the respiratory reflexes, cardiovascular reflexes, cardiovascular efficiency, muscle tone, maintenance of muscle tone, metabolic aberrations, radiation estimation and the adequacy of the protection provided, and the methods for gathering such data, and should include the new instrumentation required to do this in a more efficient and less burdensome manner.

(c) Human Engineering. This area will confine its experimentation to the actual crew performance for the job of successful flight. The study and experimentation on the analysis of the jobs to be done will be made. The crew layout, which naturally results from such an analysis, can then be better designed. The number of crew members who are required to work together in performing an operational task can be ascertained. The operational procedures, which must be established for successful flight, can be made and exercised through the development program, modified and retested to validate adequacy for leading toward successful flight. The final result of this area of study will be the [26] development of mechanisms and the training devices for training crews for such a cislunar vehicle flight.

(d) Medical support for the above areas. In this area, such studies as the natural development of micro organisms occurring within a group living within confined quarters for a 2 week period must be made. As has been well established in bacterial growth and their habits over earthbound existence, the natural incubation period for such bacteria falls within the 7 to 14 days planned for the maximum operation of this vehicle. This will mean, for example, that a healthy astronaut leaving on such a voyage could, by exposure to his crew members and the bacteria that each brings to the cabin, become quite ill during the flight time unless provisions are made within the environmental control system and through medications placed onboard to control such events. Another area that falls under the research program will include the establishment of the radiation tolerances, the devices for measuring the radiation occurring within the capsule during flight, and to ascertain any effects which may be detrimental to the flight during such exposure. Underlying this research program, of course' will be the desire to establish what can be handled by the crewman aboard and what must be provided, as far as basic equipment, to enable them to take care of themselves. In addition, the mechanisms for gathering such information aboard the vehicle when the problems present themselves during a flight must be established.

Many of these areas which have been listed under the research program will require both human and animal studies as a method for the establishment of validity to the answers of the questions that have been raised. The animals in this case will allow for multiple numbers of specimens to be exposed along with small crew groups in order that statistical numbers can be considered and data on tissues resulting from tests can be considered. The animal offers the opportunity to translate his effects to the human performance, while at the same time giving the bioscience advisors an opportunity to study pathologically some of the animals after flight. This permits the evaluation of the subtle changes seen in tissues if there are no changes in the crew anticipated or found during the flight, because it then establishes more firmly man's capability to withstand the rigors of such an advanced flight.

The crew accommodations must provide a safe and comfortable environment for the duration of this mission. Figure 2 lists the general areas which must be considered as environmental factors. Before going into a detailed discussion of these factors, certain basic considerations should be reviewed.

[27] The long duration of the flight precludes the continuous use of a full pressure suit; therefore, alternate methods for decompression protection must be devised to allow a "shirt sleeve" type environment for normal operation. The long confinement period in close quarters may require some accommodations for individual privacy, recreation and means of physical exercise. The cabin arrangement must be functional and still provide a satisfactory liveable space environment.

Let us now consider the areas listed in figure 2.

(a) Atmospheric control. The general requirements for atmospheric control are as follows:

Hermetically sealed cabin

Pressurization control

Breathing oxygen

Carbon dioxide removal

Temperature control

Humidity control

Control of toxic gases

Instrumentation

 

(1) Sealed cabin. The reentry vehicle and space laboratory cabins should be hermetically sealed with provisions for repair or self sealing of leaks. Each cabin must be considered as a selfcontained independent pressure vessel. Repairs to the pressure vessels should be made from the capsule interior and not require the occupants to leave the cabin.

(2) Breathing oxygen and pressurization. A system must be developed which can supply oxygen at a rate of 2.0 pounds/man/day and remove carbon dioxide produced at a rate of 2.5 pounds/man/day. These metabolic data should be confirmed under actual flight conditions as part of a general capsule habitability study. The oxygen partial pressure must be maintained at a minimum of 160 mm Hg to maintain normal blood saturation levels. To determine the total cabin pressure and gaseous composition, investigations into the physiological requirements, structural weight, and system weight and complexity must be made. From such a study, it can be determined if a two gas system, i.e., oxygen nitrogen, at 14.7 psi is feasible or required. The selection of oxygen sources must be a compromise between storability, reliability and weight. To achieve these objectives and to provide the required redundancy, two types of oxygen sources may be required. For example, a liquid-oxygen source could be used as the primary supply with a chemical superoxide system as the backup or emergency supply.

(3) [28] Carbon dioxide removal. The carbon dioxide partial pressure must be maintained below 4 mm Hg at all times. This control and removal of carbon dioxide may require the use of chemical absorption or the utilization of materials to collect carbon dioxide from the cabin environment and subsequently dump the CO₂ overboard. With the duration of this flight and the current state of technology, it does not appear that a regeneration system for breaking CO₂ into O₂ and carbon is feasible or required.

(4) Temperature control. The system must be capable of controlling and maintaining the cabin temperature between a selectable range of 65-75° F. This will require removal of the metabolic heat loads of 300 to 700 Btu/hr/man with peak rates as high as 1,400 Btu/hr/man. In addition, the electrical heat load must be removed by this system. The use of a refrigerant cycle or coolant liquid appears impracticable due to weight and power requirements. It therefore seems probable that a radiant type heat removal system will be required.

(5) Humidity control. A method must be devised for removing respiration and perspiration water vapors in the cabin. This removal system may be developed in conjunction with the temperature control system in which the vapors could be condensed and collected.

(6) Control of toxic gases and micro organisms. Provisions for removal of toxic materials such as carbon monoxide, methane, etc., must be made. Consideration must be given in the selection of capsule materials and in capsule operation to prevent inclusion of microorganisms which might have nurtured and multiplied in space flight to cause illness or systems interference.

(7) Instrumentation. Basic instrumentation must be provided to monitor the capsule environment. This must include temperature pressure measurements and partial pressures of oxygen and carbon dioxide. If possible, a measure of toxic materials such as hydrocarbons, CO, etc., should be made.

(b) Decompression protection. This space vehicle must have a highly reliable pressurized cabin and laboratory to preclude the use of a pressure suit in normal flight. There are several approaches to the problem of decompression protection. The first approach would be a quick donning pressure suit together with subdivision into two compartments with an air lock in between. Pressure suits would only be used in critical times such as launch or reentry. The second approach would be to provide a small rigid module for the crewmen in which they can be pressurized above the bends level and have emergency controls to effect reentry and landing. This approach, however, does have the disadvantage of not allowing the occupants to move from a pressurized compartment into a decompressed compartment in case of an emergency.

(c) [29] Acceleration and restraint. The resultant vector accelerations caused by linear, oscillatory and rotational motion and applied to the astronaut support couch or restraining harness during either normal or aborted missions shall not exceed accepted limits. Figure 3 summarizes the known data for sternumward forces for pure accelerations in directions perpendicular to the spine and for lateral loads and the resultant vector loads. From this plot, it can be seen that 20g in the perpendicular and 10g in the lateral are the presently accepted tolerance levels. Current studies at Wright Air Development Division (WADD) indicate that these levels may be exceeded without injury; however, data from these tests are not complete. Figure 4 summarizes the accelerations that human beings have endured for the time duration shown. Tolerances may be greater but these are the best data available at this time. The duration of sustained load is an important variable and only data having significant durations were plotted. The gaps from 0.01 to 0.04 second exist since this is in the region of impact type decelerations in which onset rates may affect tolerance. Another gap exists in the data from 1 1/2 to 8 seconds.

The accelerations applied must be limited to these values because tolerance data justifying larger accelerations are not available for vector directions other than parallel to the principal body axis. Furthermore, intelligent vehicle control efforts do not appear possible when the accelerations imposed exceed these values. If these limits are exceeded, additional tolerance and control studies must be conducted.

If tumbling, spinning, or rotation occurs during the mission, the rate should not exceed one revolution per second and the duration should not exceed 1 minute. These limits have been demonstrated as tolerable limits (Ref. Journal of Aviation Medicine, Feb. 1954, pp. 5-222).

The design of the restraint couch and harness system should place the occupant in a supine position during launch and reentry. This position provides maximum tolerance protection to linear accelerations.

Several approaches to couch design should be investigated for example, the net couch or a universal formed couch which utilizes particulate matter that becomes rigid when evacuated but remains pliable and readily contoured in the absence of a pressure differential. The couch must be designed to serve as a bed and, if possible, the couches should be designed to fold away to give maximum floor space in flight. The integration of decompression protection into the couch must also be investigated.

The restraint harness must be designed to restrain the crewman in all directions in which accelerations will be encountered. The harness must be easy to attach, simple to adjust and free of loose straps, etc. [30] to provide a clean harness installation. The use of an integrated restraint garment must be investigated to achieve these goals.

If emergency accelerations exceed the tolerance limits, attenuation devices must be provided as backups to the capsule landing attenuation system.

(d) Noise and vibration. me noise level within the capsule must not exceed those limits shown by figure 5. During normal flight the vehicle noise level should be maintained below 40 decibels. Vibrations during launch and reentry must be maintained below the "painful" level indicated by figure 6 and below the ''unpleasant" level during normal flight.

(e) Nutrition. A balanced diet of approximately 3,000 kilocalories/day/man must be provided. The foods must be palatable and provisions for warming the foods must be considered. If possible, lowresidue type foods should be provided to ease the waste handling problem. me types of food and the dispensing equipment must lend themselves to weightless operation.

(f) Waste disposal. With the relatively short duration of this mission, it does not seem practical to attempt to recycle and utilize the fecal wastes. Therefore, provisions for storing and decontaminating the fecal waste must be made.

The recycling of urine, however, appears to be worthy of investigation. Figure 7 indicates that 168 pounds of urine would be available for reclamation; this coupled with water from perspiration and respiration would greatly reduce the onboard water requirements provided a highly reliable purification system is developed.

(g) Interior arrangement and displays. Since the space available will be limited, every effort should be made to make what space there is usable for several purposes (use of fold away devices, etc.).

In general, provisions for privacy and a sleeping, general living and eating area apart from the laboratory would be desirable. Sleeping may best be accomplished in a zippered sleeping bag that would restrain the crewman and provide decompression protection.

Provisions for recreation, personal hygiene' and exercise must be made. The use of radio and reading materials should provide adequate outlets for the recreation requirement. Use of microfilms may prove useful in this problem area. Dry wash techniques for personal hygiene and the use of ultrasonic cleaners for maintaining clothing should be investigated. Some type of exercise equipment such as a treadmill or [31] rowing machine must be provided to maintain body tone. The exercise equipment may be developed to transform the mechanical energy into electrical energy to recharge onboard electrical supplies.

Figure 7 summarizes the metabolic requirements for this mission. This data is presented only as "ball park" data to give a feel for basic requirements.

(h) Bioinstrumentation. The amount and types of instrumentation in the three man capsule should not differ materially from the Mercury capsule instrumentation. Practically the same parameters will need to be measured and the increased size of the capsule will not need to increase the size of the instrumentation package to any extent. With less instrumentation per man and a division of responsibility among the crew members, the monitoring of the capsule should not require a large portion of the men's time. An automatic alarm and warning system for dangerous conditions and malfunctions should be provided so the men will not have to monitor continuously and be available for other useful functions.

The bulk of the instrumentation should be placed in the reentry vehicle so most of the control can be carried out in this portion and duplication in the laboratory portion will be unnecessary. In any case the control will be needed during launch and reentry in this portion.

The area of radiation and its measurement (also its protection) is probably one of the most controversial ones that exist in the entire system. The levels of radiation which the man will accept during routine operation should be kept, through design, to an absolute minimum. By this technique, the man will have every opportunity to use his total maximum dosage limit during the times of solar activity. The maximum allowable dosage permissible for an astronaut has been discussed with many experts within the United States, and the general concensus of opinion is that 25 REM is the upper limit. To demonstrate the problems of radiation effect, the best guesses of these experts and what they predict would occur in the astronaut when compared to the total exposure, can be seen in figure 8.

It seems obvious that the significance of the maximum dosage of 25 REM, as mentioned above, is that we are in an area, as predicted by the experts, where a rapid increase in both the chronic as well as the acute changes, is beginning to occur. It is probably of equal significance to note that this is a guess of percent of effect rather than tested data in this area. This, we believe, summarizes very well the problem and need of gathering hard figures which can be used for design and prediction of effect of radiation on the astronaut. For example, there is a small group in the United States which feels the dosage [32] techniques presently being used may not be really applicable to space exposure. If this is true, then the individuals receiving 25 REM in the present measurement technique would not receive the total dosage effects predicted. In addition to this, it should be noted that an individual receiving the 25 REM maximum dosage over small increments over a period of time would not get a completely additive result. For example, if the man received 10 REM on the way out through the radiation belts and 15 REM 2 weeks later coming back through the radiation belts, the total effect would not be 25 REM, but some increment less than this. The 25 REM dosage mentioned above is considered as the exposure of a man on a single dosage. The radiation exposure can be reduced through the proper utilization of trajectory planning and also through the use of acceleration planning to schedule shorter times of flight through the belts. The best estimates at this time would indicate that through the use of the equipment aboard the vehicle as shielding, the use of trajectory planning, and the use of time in radiation belt exposure as methods of protection, the crew will provide sufficient latitude for design and flight planning to permit the flight of such a cislunar vehicle within the state of the art today. In the event a solar flare occurs during the flight program of either the orbital or of later cislunar flight, serious consideration as to what dosage limits will be, under these conditions, should be made through experimental studies; and the techniques which would be advisable for the crew should be established. Presuming that the further studies in the radiation areas do not develop any additional new problems for our planning and designing people, there still remain to be solved several problem areas in the vehicle design. An actual establishment of a radiation dose should be made. This includes the validation of either the present measurement technique of dosage or the validation of the volumetric dose technique. After the dosage limits have been established, then the development and testing of the equipment which should be placed aboard the capsule for the measurement of the accumulating dosage for the crewman must be made. This instrumentation will have to reflect a capability of reading the accumulated dosage for the crewman as well as a warning system for the men when a certain level of tolerance has been exceeded. It should be such that the men can easily ascertain their day to day situation.

The number of astronauts required for the crew of a cislunar flight varies with the following factors:

(a) The number of crew jobs required for successful flight. These tasks must be further divided as to the relative priority of each task, the number of tasks which must be done concurrently, etc. As an example, the tasks can be divided into those of primary importance (vital to flight) and those of secondary importance (essential but of lesser [33] magnitude). For example, the tasks of pilot, communicator, navigator, engineer, and flight conductor may be considered as primary tasks. Such areas as health monitor (radiation count, medical care for injury, etc.), commissary supervisor, waste material supervisor may be considered secondary. It is possible for one man to be cross trained in more than one area. However, the desire to have one man primarily responsible for more than one area must be modified by such events as how many men will be required to perform simultaneously to make a successful flight (i.e., a midcourse guidance will require both pilot and navigator to operate simultaneously). In addition, the complexity of each of the primary tasks dictates that one man cannot be counted upon to do a reliable job in more than two of these areas. He can act as a backup on some of the other areas through cross training. Actually, the job areas are analogous to the present day B-47, B-52, and B-58. A man on the crew can do one task or make one decision at a time; therefore, more men are requested. The first study indicates a minimum crew size of three men to handle the total task area.

(b) The duration of the orbital and cislunar flight will cause the diminution of the capability of a given crewman to perform under an abnormal on duty off duty schedule. Man can have his normal 8 hour work cycle interrupted for a series of 2 or 3 days with a small but increasing loss in efficiency; even here, breaks must be provided. However, when this interruption is maintained for more than 2 to 3 days, a standard 8 hour shift system must be considered in the flight as maximum. This dictates more than one crewman will be needed to cover the flight duration of 2 weeks, if the desire to operate continuous surveillance and communication capability is met. Again, the minimum crew size will be three for a 24 hour period of operation with each working 8 hour primary shifts with extra short periods of specific help on problems.

(c) The level of alertness required by the crewman will cause further modification of the 8 hour work shift. If monitoring is the task, then shorter work cycles will be required. This will increase the need for multiple men. For example, a pure monitoring task such as surveillance of vehicle operation will set a 4 hour maximum single period performance without rest or severe loss of alertness.

(d) Redundancy of man's system to prevent abort of the flight due to injury or illness of a crewman must be considered. Presuming a second crewman can support the injured or ill astronaut, thus increased reliability of the flight can be obtained by multiple crew. This will simplify the problems of inadvertent recovery at unprepared sites. Serious consideration of flying the total mission rather than aborting should be made due to the complexity of recovery from an unscheduled earth impact.

(e) The utilization of this vehicle as an intermediate orbital laboratory dictates space and provision for carrying aloft experiments [34] and experimenters necessary to demonstrate man's capability to operate under these advanced flight precepts. In these tests) it would appear essential that personnel other than normal flight crewmen will be required to complete the tests with a minimum of flights. This becomes essential if the stated desire to reduce bioinstrumentation monitoring on the astronaut is held to' problem areas in astronaut provision and habitability is eliminated before the cislunar flight. The significance of this type of approach becomes apparent where the need for a reliable crew is considered as vital to the cislunar flight, and the automatic recovery aids are reduced or eliminated.

ATMOSPHERE CONTROL.

DECOMPRESSION PROTECTION.

ACCELERATION PROTECTION.

NOISE AND VIBRATION.

NUTRITION.

WASTE DISPOSAL.

INTERIOR ARRANGEMENT AND DISPLAYS.

BIOINSTRUMENTATION.

 

 

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[36] Figure 3. RELATION BETWEEN ALLOWABLE ACCELERATION IMPOSED ON OCCUPANT OF CAPSULE AND ANGLE OF ACCELERATION VECTOR WITH ROLL AXIS OF CAPSULE.