1047. Weight Estimation of Manned Spacecraft Metabolic Requirements


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C K McBaine: 1047. Weight Estimation of Manned Spacecraft Metabolic Requirements. 1975.



One of the new problems confronting the weight engineer is the material and energy balance
of the human system loop in the manned spacecraft.
This paper presents methods of estimating weight of the crewman’s metabolic material
requirements for a balanced system. The methods are further clarified by an example problem
being carried through the analysis for a 50 percentile crewman with a certain daily activity
and diet composition.
The analysis begins with the problem description of the crewman metabolic material requirements
and material balance. Fundamental to the problem solution is the determination of the metabolic
energy requirements and the metabolic input/output materials to satisfy these requirements.
This paper presents methods for estimating the crewman’s metabolic energy based on his physical
characteristics and activity. Graphs are presented for the crewman’s weight and height while
equations are presented for the determination of body surface area which is fundamental to the
metabolic energy determination.
Food weight estimating equations are presented based on metabolic energy and food composition.
Independent chemical oxidation equations of the food constituent (protein, fat and carbohydrate)
are presented and used in the determination of oxygen requirement and carbon dioxide and metabolic
water production. Limits in the use of these equations, in regard to Basal Metabolic Rate (EMR)
and Respiratory Quotient (RQ) are given. The water balance is presented in weight equations as a
function of metabolic energy. The metabolic material weight determinations and system balance is
concluded with the determination of fecal waste.
Certain weight sensitivity parameters, such as food composition,percentile and metabolic energy and
their effect on the metabolic requirements and waste products, are discussed.
The discussion concludes with the presentation of a recently patented closed ecological system for
extended missions as justification of the importance of this analysis for future missions. Cursory
study indicating that completely closed ecological systems would be required for mission over
approximately 3-3/4 years, from a weight and economic standpoint.


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