ADAPTATION OF 25-NODE HUMAN THERMAL MODEL FOR USE IN SIERRA NEVADA CORPORATION'S DREAM CHASER ® SYSTEM-LEVEL THERMAL DESKTOP MODEL

Sierra Nevada Corporation (SNC) is currently working with NASA's Commercial Crew Program to develop and configure the Dream Chaser® spacecraft for transportation services to low-Earth orbit destinations. Part of this effort is a system-level thermal model of the vehicle to predict its thermal response during the various phases of flight, and to help with the design of active and passive thermal control systems. Since the Dream Chaser is capable of piloted or autonomous flight, the thermal response is important to the overall thermal design, especially in the crew configuration. NASA and its contractors have developed various human thermal models since the 1960's. Two models of note include the early 25-node human thermal model 1 and its successor, the 41-node METMAN model 2 . The model divides the human body into 6 or 10 compartments. Both models use 4 nodes to model the core, muscle, fat, and skin of each compartment. The final node is to model the blood flow. Heat losses due to convection, radiation, perspiration, and respiration are modeled. The major differences between these two models are that the 41-node model distinguishes between left and right arms and legs, and also has the ability to work with humans of various sizes. However, both of these models are executed in FORTRAN programs, and have not been adapted for public use in a system-level thermal model. This paper describes how SNC and ATA Engineering, Inc. (ATA) converted the 25-node thermal model for use in the Thermal Desktop system-level thermal model, and added features from the METMAN model to model humans of different size and anthropomorphic constituency. The models consist of a combination of SINDA nodes and conduction, along with control logic to compute the metabolic heat loads based on environmental conditions and human activity. The models can be connected to a cabin air node or to a liquid cooled garment (LCG) loop node. The model also allows for the ability to compute human CO2 and water vapor production for cabin air environment modeling.