SYSTEMS ANALYSIS OF MANNED ORBITING LABORATORY FEEDING SYSTEM

 

NORMAN G. ROTH

 

Whirlpool Corporation

[43] The purpose of my discussion is to present the systems-analysis approach which Whirlpool Corp. is using to attempt to improve the overall feeding system for the Manned Orbiting Laboratory (MOL) program. It is my hope that this discussion will facilitate understanding of the problem of feeding man in a spacecraft in light of a total spacecraft system rather than by a shotgun approach of developing individual improved food items or hardware components. In my opinion, which is based on years of experience as a contractor on both the Gemini and Apollo feeding programs, a shotgun approach will do little to advance the overall state of the art.

As mentioned in other papers, the MOL baseline system emerged in the contract as an exact replica of the late Gemini feeding system, insofar as packaging and food items were concerned. The MOL system allocated a total storage volume per day for each astronaut's food of approximately 195 cu in. for a baseline menu of 2900-Kcal. The average volume of the dehydrated food in this 2900-Kcal menu was only 88 cu in. However, because of packaging and food-shape inefficiencies in this baseline system, this 88 cu in. of food, when oriented as efficiently as possible, completely filled the allocated available volume of 195 cu in.

Some of the packaging inefficiencies were related to shapes of foods used in the menu and others, to the nature of valves and other irregular components used in the package. The 195 cu in. of storage volume allocated per man day of food in MOL was in a theoretically very efficient "shoe box" shape of 3.7 by 6. 3 by 8.3 in. However, with the baseline system, this storage space could not be efficiently utilized.

Figure 1 shows the dimensions of the current Apollo bite-size foods. These fairly regular foods form no regular pattern when attempts are made to package them together. The rehydratable foods presented an even more difficult problem to the systems integrator. First, the package incorporated a hard poppit-type water entrance valve and a hard waste-stabilization tablet which defied all attempts at efficient stowage and tended to crush bite-size foods in intimate contact. Second, the shapes and sizes of the rehydratable foods were purely arbitrary. The rehydratable foods acquired their current dimensions from the original development work, which was carried out by using Spam cans as molds for freezing experimental products prior to drying. These cans were inexpensive and handy for producing experimental samples. However, the arbitrary dimensions did not relate to any specific requirement of the feeding system. In general, a bar, the size of a Spam can and 1 in. thick, was not a satisfactory serving portion, nor was it dimensionally an integral factor of any available storage volume. The dimensions used in the baseline system were of no value from either the engineering or nutritional standpoint; they were merely a carryover from early development work.

The baseline MOL foods were acceptable from both the nutritional and organoleptic standpoint if properly used, but under actual previous system application they left something to be desired. Considerable data presented by previous speakers attest to the fundamental acceptability of the foods. Our task at Whirlpool was to perform a systems analysis which could lead to an overall acceptable feeding system under actual spacecraft conditions. The remainder of this paper will be concerned with the nature of this systems analysis and the basic conclusions.

[45] First, let us look at the interface charts (figs. 2 and 3) so that we can understand all that is involved in the system. At the center of the chart is a typical rehydratable food package. The broken lines are not within the scope of the feeding-system contract, but they are shown because they serve to describe the total system. After this look at the overall system, the analysis was undertaken.

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[47] Overall goals, in brief, from the food standpoint were to:

(1) Optimize baseline foods to provide satisfactory serving or portion sizes.

(2) Provide nutritional modularization, so that a serving of a given class of food would provide about the same nutritional content as any other serving of another food of the same class. (For example, all meat items should be nutritionally interchangeable. )

Overall goals, in brief, from the packaging standpoint were to:

(1) Make all food packages modular, the size being based on the fixed dimensions of the spacecraft compartment. In order to do this, and still to allow for the nutritional modularity, packages and contained food should have strictly fixed dimensions in two dimensions, with the third dimension variable to allow for weight adjustments of individual food items.

(2) Eliminate inefficient protuberances such as hard valves and disinfectant tablets.

(3) Allow for normal and efficient spoon-and-bowl-type eating.

(4) Provide efficient modularization of all types of foods, including rehydratables, bites, and beverages, with maximum interchangeability.

These were the basic goals. However, many other constraints were imposed by the system. These included:

(1) System integrity, i. e., minimization of loss of food to the atmosphere

(2) Identification of all foods and meals

(3) Accessibility of all foods

(4) Efficient food-waste handling

(5) Ability to open and close a package easily

(6) Ability to add water to rehydratable foods easily and reliably

(7) Containment in a ration pack

(8) Compatibility with all normal and emergency spacecraft environments

(9) Overall safety

(10) Overall noncomplexity

(11) Anthropometric compatibility The foregoing criteria are illustrative, but certainly not all inclusive.

The study began with an analysis of the nutritional and dietetic aspects. The initial objective was to modify food portions to reflect normal portion sizes. This was done by using standard military and institutional food-portion recommendations as a guide. Generally, this modification resulted in increasing the portion size of "main dish" food items and decreasing the portion sizes of dessert items. It also resulted in a decrease in total number of food packages required per man day from an average of 22 to a maximum of 16.

Table I shows a comparison of portion sizes in the current menus with those in the recommended modified menus; the values are based on use of normal portion sizes. Generally, it can be noted that the portion size of meat- and soup-type foods increases and that of dessert-type foods decreases. This in itself should help to eliminate some of the valid complaints of too many sweets in the menu.

[49] After analysis of the food modularization, the next step was to perform a dimensional modularization, to determine optimum utilization of the available stowage space. The nutritional study indicated that a maximum of 16 packages per day, distributed as shown in table n, could meet the MOL requirements. Volume requirements for this distribution were determined to be as shown in table III.

The first engineering task was to determine the optimum modular shape for the food packages. Spacecraft interface constraints dictated that the ration (defined as food for 1 man for 1 day) fit within the dimensions shown in figure 4. There are obviously many possible dimensions for 16 packages within this overall dimensional limit. The first tradeoff study was performed to select the best dimension for individual food packages within this system.

Figure 5 shows a few of the possible configurations studied. (In these sketches, the first number indicates width and the second indicates height; e. g., 2 by 1 is 2 packages wide by 1 package high. ) All configurations from 1 by 1 through 10 by 1 were examined; configurations over 11 were considered not feasible.

Tradeoff factors used in the study were:

(1) Package access

(2) Availability of space for mounting rehydration aperture

[50] (3) Compatibility with hot-water-probe enclosure

(4) Anthropometric compatibility

(5) Maximum package depth

(6) Bite cross section

(7) Number of bites per modular face

(8) Minimum acceptable bite volume

(9) Maximum acceptable bite volume

(10 ) Flexibility of bite serving volume

(11) Permissible serving sizes as function of thickness

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All factors were assigned numerical ratings in the tradeoff study. In addition, go-no-go numbers were assigned, and any single no-go configuration eliminated a particular dimension. I cannot go into the total mathematics, but I would like to present one example. Figure 6 illustrates a fixed spacecraft system constraint, the hot-water-probe cavity dimensions. Any package dimension which does not permit access to the hot-water probe for rehydration obviously would be discarded from further consideration.

After a thorough systems analysis, which can only be mentioned here, the 5 by 1 dimension was selected as optimum for modularization of the MOL food packages. This resulted in a package dimension for all foods, bites, rehydratables, and beverages, as shown in figure 7. In order to make the system work most efficiently, a loose fill of rehydratable foods, rather than use of formed bars, was most desirable. With a variable length dimension, loose fill would allow for nutritional modularity between foods and for ease in adjusting portion sizes of a given menu for individual men of different body sizes and, therefore, different calorie intake requirements.

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[53] Table IV shows, with samples of Apollo foods, that loose-fill foods (after vacuum packaging) require no more volume than formed bars. The modular packaging requirement also dictated a change in shape of the bites from shapes previously shown to wafers about - ln. thick by slightly over 1 in. square. Fortunately, this shape is in general agreement with Air Force dental research results on optimum size of bites.

After selection of dimensions of the modular packages, similar systems tradeoff studies were performed to establish the basis for package designs. In the case of the rehydratable package, separate tradeoff studies were first performed by selecting the rehydration aperture and package closure concepts. The rehydration aperture concepts included:

(1) Maximum diameter

(2) Maximum length

(3) Requirement for adapter to mate with water probes

(4) Self-closing feature

(5) Reliability

(6) Potential for leakage around probes

(7) Potential for leakage during kneading

[54] (8) Feasibility

(9) Valve-food interference

(10) Material requirements

(11 ) Tooling requirements

The package-closure concepts included:

(1) Compatibility with package face

(2) Capability to be folded over end of package

(3) Cross section of opening

(4) Tendency to be soiled by food removal

(5) Simplicity of operation

(6) Capability to be opened with one hand (on console)

(7) Capability to be opened with one hand (hand held)

The selected concepts were then used in developing the overall rehydratable package concept.

Beverage and bite-size package studies were performed in a similar manner.

The tradeoff factors utilized in selecting the most feasible rehydratable food package concepts were functional factors, system factors, and program factors. The functional factors were

(1) Manipulation

(a) Insertion of water probes

(b) Rehydration

(c) Opening and reclosure

(2) Temperature maintenance

(3) Rehydration aperture

(4) Access to food

(5) Compatibility with unpressurized gloves

(6) Total operation time requirements

The system factors were:

(1) Weight

(2) Volume

(3) Reliability

The program factors were:

(1) Schedule (time to qualification)

(2) Unit cost

(3) Tooling cost

The tradeoff factors utilized in selecting the most feasible beverage package concepts were the same three factors. The functional factors were:

(1) Manipulation

(a) Initial seal opening

(b) Insertion and removal of clamp (if any)

(c) Insertion and removal of straw (if any)

[55] (2 ) Rehydration aperture

(3) Terminal seal

(4) Safety (protruding tabs )

(5) Ease of microbiological stabilization.

 

The system factors were:

 

(1) Weight

(2) Volume

(3) Reliability

The program factors were:

(1) Schedule (time to qualification)

(2) Unit cost

(3) Tooling cost

The same tradeoff factors were utilized in selecting the most feasible bite package concepts.

The functional factors were:

(1) Manipulation

(a) Insertion of accessory devices (if any)

(b) Opening and reclosure

(2) Cube retention

(3) Crumb retention.

The system factors were:

(1) Weight

(2) Volume

(3) Reliability

The program factors were:

(1) Schedule (time to qualification)

(2) Unit cost

(3) Tooling cost

As I hope you can gather from the foregoing discussion, a thorough systems analysis and tradeoff study has been performed on the MOL feeding system. Preliminary design concepts have been evolved for a new baseline feeding system. These design concepts have been thoroughly integrated with the total spacecraft requirements and have met the basic goals of the study. Packaging efficiency of the ration has been improved, and flexibility of food portions usable within the ration has been greatly increased. Design concepts for packaging rehydratable foods, beverages, and bite-size foods have been developed. These design concepts are completely modular and provide for eating in a manner much as one does on Earth. Rehydratable foods are consumed with a spoon; beverages, through a straw. Design concepts for the foods provide for greater flexibility and improved anthropometric compatibility.

During the progress of the systems analysis, no attempt was made to establish detail design of the packages or radical changes in food production techniques. The systems engineers have set the ground rules. On the basis of the systems analysis, the designers and food technologists can now start the specific developments leading to provision of all the components as a complete integrated system.

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