Redesigned Human Metabolic Simulator

Tag : Testing Sieve
The improved HMS (see figure) would include a computer that wouldexert overall control. The computer would calculate the requiredamounts of oxygen removal, carbon dioxide addition, water addition,and heat addition by use of empirical equations for metabolicprofiles of respiration and heat.
A blower would circulate air between the HMS and a chambercontaining a life-support system to be tested. With the help offeedback from a mass flowmeter, the blower speed would be adjustedto regulate the rate of flow according to the number of persons tobe simulated and to a temperatureregulation requirement (the airtemperature would indirectly depend on the rate of flow, amongother parameters).
Oxygen would be removed from the circulating air by means of acommercially available molecular sieve configured as an oxygenconcentrator. Oxygen, argon, and trace amounts of nitrogen wouldpass through a bed in the molecular sieve while carbon dioxide, themajority of nitrogen, and other trace gases would be trapped by thebed and subsequently returned to the chamber. If, as recommended,the oxygen concentrator were of a rotating twelve-bed design, thenvariations in the product stream could be made very small.
Carbon dioxide would be added directly to the circulating air bysimple injection from a supply tank. The rate of injection would bemaintained at the required rate by use of a massflowmeter/controller. In the same way, nitrogen would be added tomake up for the small amount of nitrogen lost through the oxygenconcentrator.
Water vapor would be added to the circulating air by heating thecorresponding required flow of water to steam in a heat exchanger.More heat, required to complete the simulation of the thermaleffect of respiration, would be added through another heatexchanger. Heat would be supplied to both heat exchangers via ahot-oil loop.
This work was done by Bruce Duffield, Frank Jeng, and Kevin Langeof Lockheed Martin Corp. for Johnson Space Center.
This invention is owned by NASA, and a patent application has beenfiled. Inquiries concerning nonexclusive or exclusive license forits commercial development should be addressed to the PatentCounsel, Johnson Space Center, (281) 483-0837. Refer to MSC-23846.