[31] The design specifications placed upon the feeding systems of space vehicles were numerous and restrictive. Many of the specifications taken independently were not difficult to attain; however, the effect of specification interactions created binding limitations. Consequently, the food developed for space missions and the associated packaging and other components and factors which made up the ultimate feeding systems were not completely verified. The USAF School of Aerospace Medicine at Brooks Air Force Base was assigned by the Manned Orbiting Laboratory (MOL) Systems Office the task of evaluating the MOL Baseline Feeding System to be used in meeting its 30-day night requirements. This effort was jointly supported by NASA.

The objectives of this evaluation were to identify any deficiencies in the expanded Gemini/ Apollo systems, to perform a functional verification for 30 days, and to develop new criteria for future space feeding systems. The evaluation was divided into four areas: (1) life-support evaluation, which included studies of the nutritional value afforded by the food; (2) food acceptance and preference evaluation, which included the rating of individual foods, measurement of food consumption, and the psychological benefits provided; (3) systems interface, which included study of efficient use of weight and volume allowances, the reliability of systems components, the timeline production of metabolic, food, and packaging waste, and the potential for environmental contamination; and (4) human factors, which included simplicity, ease of handling, and safety.

The procedures used in this evaluation are described in published articles (refs. 1 and 2) which are too detailed to cover entirely here. Briefly, this research was accomplished in a low-pressure chamber (shown in fig. 1). The environment of this chamber was approximately that planned for the MOL vehicle, as follows:

(1) Chamber pressure: 27, 000 ft or 258 to 260 mm Hg

(2) Temperature range: 23° to 25° C

(3) Humidity range: 30 to 60 percent

(4) Partial pressure of the constituent atmospheric gases:

(a) Water vapor pressure: Approximately 10 mm ± 3

(b) Oxygen partial pressure: 182 mm or 70 percent

(c) Helium partial pressure 76 mm or 18 to 20 percent

(d) Carbon dioxide: < 1.6 percent or < 5 mm Hg

[33] Volunteer airmen from the USAF Air Training Command were selected as subjects; selection criteria used were medical records, results from aptitude examinations, and personal interviews concerning motivation. Three studies were accomplished to evaluate the MOL Baseline Feeding Systems. Each study used four subjects who lived in the low-pressure environment for 32 days. The subjects were required to rate each food item after consumption. In addition, they were required to inspect the food packaging for air leaks and other failures, measure the size of food bites and main-meal entrees, observe evidence of crumbling in bite-size foods, note rehydration characteristics of powdered and main-meal entrees, subjectively measure the hardness of bite-size food, note changes in color of the foods, measure time required for rehydration of main-meal entrees, and measure temperatures of the food following rehydration. In addition, each subject was required to keep a log of his impressions of the foods day by day throughout the entire study.

The subjects were provided a menu designed to meet their individual nutritional requirements based on lean body weight measurements (ref. 3). The subjects were also required to consume all foods which were to be tested for a period of 12 days prior to the start of the study. Their individual likes and dislikes were then formulated into the study menus with the use of a computer (ref. 4). Metabolic balances were performed every 4 days of the study for 8 nutrients. Prior to and immediately following the 32-day study the subjects were given an extensive physical and psychological examination to detect any changes associated with the study.

The digestibility of the major nutrients is shown in table I. These data demonstrate that these foods are exceptionally well utilized. The values are approximately 5 to 10 percent higher than those reported for standard rations served in military dining halls. Body weight changes for all subjects were maintained within 1 kg throughout the entire 32-day period. Changes in body composition, however, were noted which were attributed to the level of activity in the chamber. Positive balances for calcium, nitrogen, and phosphorus were maintained. Balances for potassium and magnesium were variable and frequently in the negative range; this was attributed to the marginal levels of these elements in the food. Balances for sodium and chloride were highly variable; this was attributed to the inactivity of certain subjects. Overall, it must be concluded that these foods are capable of providing adequate life support.

[34] The food acceptance and preference studies must be analyzed with extensive considerations. All food ratings were above 6 on the 9-point hedonic scale. However, it must be pointed out that none of the subjects were trained in rating foods, and each subject was afforded the opportunity to eliminate unliked food from his menu. Previous research in this area has shown that food acceptance and consumption are not directly equatable. If allowed freedom of choice and rejection, certain foods rated 9 on a hedonic scale will not be consumed at the 100-percent level, whereas some foods rated lower than 9 are routinely consumed at the 100-percent level. In these studies with only freedom of choice permitted, all subjects had no problem in consuming 100-percent of their menu.

The subjects' logs and critique forms provided many comments concerning food texture, flavor, and color that are worthy of note. The rehydratable entrees were criticized for loss of texture when forced through the feeding port of the zero-G feeder. The subjects also felt that the color of foods was less than desirable before hydration, particularly the spaghetti and meat sauce and the salmon salad. Additional green vegetables would provide more color.

Many subjects noted a change in flavor and taste on their return to ground level. They indicated that the food had more flavor when eaten at 1 atmosphere of pressure. Such flavor changes have been noted for precooked frozen foods also. It may be associated with odors concentrated in the chamber, or there may be some physiological change associated with taste in the low-pressure, altered gaseous environment.

In the study of systems interfaces, serious incompatibilities were revealed. In the second study, flight-qualified packaging was used, and 14.4 percent of the zero-G feeders failed. The failures were of three types: (1) Delamination with subsequent rupture of sealing layer, (2) leakage around the rehydration valve, and (3) valve failure due to improper tolerance on O-ring groove. The delamination was the result of poor adhesive in a lot of packaging material. All the deficiencies were corrected and the failure rate was less than 1 percent during the third study. The delamination was avoided by the use of a new lot of packaging material which was produced just prior to use. It was later shown in our laboratories that the adhesives used in the film laminate are moisture sensitive. Even the moisture in room air was sufficient to render the adhesives ineffective over a 60-day period. The leakage around the rehydration valve was corrected by the use of shrinkable Teflon to secure the valve in the package.

In evaluation of the utilization of weight and volume, it was shown that packaging constituted 35 percent of total weight. The individual packages of food were of a shape which prohibited efficient use of the allowable volume.

The timeline analysis of food preparation, food consumption, and waste management reveals excessive expenditure of time for these functions. The individual mealtime ranged from 18 to 42 minutes. Procedures for rehydration and consumption of foods are especially complicated and difficult to perform. During periods of intense activity, the tendency to avoid foods requiring rehydration is great. Frequently, subjects reported that they would start eating bite-size foods while waiting for the main meal entrees to rehydrate. This procedure would decrease their appetite because many of the bites were sweet dessert items.

[35] Another problem associated with the feeding system design is the transfer of heat in rehydratable foods. Temperatures measured on hot foods were routinely lower than 100° F while cold foods were frequently above 55° F. The extent of heat exchange was attributed to both the lack of insulation afforded by the package and the time required for rehydration and consumption of the food.

The package material used for the food was found to have substantial resilience. This material provided excellent protection for the food but created problems with stowage. In addition, this resilience and the design of the zero-G feeder contributed to a high residual food level (food which could not be squeezed out of the zero-G feeder). The subjects made every effort to remove all the food; however, from 5 to 10 percent of the main-meal entrees was left in the zero-G feeders. The quantity of residual food is important since this necessitated the use of an antimicrobial agent which would not be needed if all food could be removed from the package.

Another important area of consideration under the topic of systems interfaces is the production of metabolic waste. Voiding in zero G is difficult, and the equipment used for storing and treating the waste is crude. The pilots have confided frequently that they would rather exist on insufficient nutrient intake than face frequent defecations. They will not eat any foods they suspect will promote frequent defecations. The foods presently used for space feeding provide excellent results in gastrointestinal bowel control. The data in table II show that both the number of defecations and the amount of fecal matter produced were reduced. In comparing this with data collected during the consumption of regular food, there is a 50-percent reduction in both the number of specimens voided and the quantity of materials used. Subjective measurements of flatus during these studies revealed that the amount was small enough to preclude discomfort from bowel extrusion.

In considering the human factors area, the present baseline system was found to be highly reliable but complicated. The time required for manipulation during preparation and eating was discussed above. In addition, the treatment of residual food to prevent degradation upon storage was found to be both time consuming and difficult. The antimicrobic agent used to treat the residual [36] food is sealed in a separate area of the primary package in the form of a tablet. The removal of the tablet and its insertion into the used bag has a high fumble potential. Once it was in the bag, the subjects found the tablet difficult to break into pieces to assure even distribution in the bag.

The design of the zero-G feeder also presented minor safety hazards. Cut material around the mouthpiece caused occasional cuts on subjects' lips and fingers. It was also a constant threat to the eyes; however, no injury of the eyes occurred in these studies.

Another area of consideration is the size and shape of bite-size foods. There are several different sizes of food bites: 1.1-cm (11/16-in. ) cubes; 0. 6- by 2. 5- by 2. 5-cm (1/4- by 1- by 1-in. ) bacon squares; 0. 9-by 2.1- by 2. 8-cm (3/8- by 7/8- by 1 1/8-in. ) cinnamon toast; 3.2 cm by 2.5 cm by 1.6 cm (1 1/4 by 1 by 5/8-in. ) sandwich bites. The subjects had difficulty in placing the larger bites in the mouth and chewing. The initial crushing of the bite was difficult if the depth of the bite was greater than 0.5 in.

The volume of food in the mouth was also important. These foods are dry and require saliva to rehydrate. A maximum volume of 0.40 cu in. was considered ideal. Some bites such as the fruitcakes were criticized for being too hard. Using a punch 1 cm in diameter closing at the rate of 10 cm/min, the optimum hardness for bite-size foods is approximately 25 kg/ sq cm.

At the conclusion of these studies, the feeding system was functionally verified. As a result of these studies, the following changes in the feeding system were made: (1) The rehydration container was redesigned in the following manner: A valve was installed with shrinkable Teflon to hold the valve to the package, the size of the beverage bags was increased, the quality of materials was improved, mouthpieces were widened to provide more convenient removal of the food, and the antimicrobic tablet was relocated and made smaller; (2) foods were improved by reducing rehydration times and making the texture more defined and natural; (3) bite sizes of foods were changed in shape and size and the integrity and hardness improved; and (4) the nutritional composition of these foods was defined and methods for planning a balanced and acceptable menu by using a computer program were established.

1. Vanderveen, J. E.; and Allen, T. H.: Evaluation of Feeding Systems for Manned Orbital Flight. Res. and Technol. Briefs AFSCRP 80-1, Mar. 1968.

2. Vanderveen, J. E.: Evaluation of Foods for Space Flights. Proc. of the Xll Plenary Meeting of COSPAR (Prague, Czechoslovakia), May 1969.

3. Allen, T. H.: Measurement of Human Body Fat: A Quantitative Method Suited for Use by Aviation Medical Officers. Aerospace Med., vol. 34, 1963, p. 907.

4. Chapin, R. E.; Anway, M.D.; Lozano, P. A. ;and Vanderveen, J. E.: Computer Programming of Aerospace Rations. SAM-TR-68-115, Nov. 1968.

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