Space Suit Research Paper

Abstract

Human body temperature should be maintained at an approximate value of 37oC. Temperature regulation of human body becomes important in situations such as space ventures, firefighting, etc. Heat gains from external heat sources such as sun, heat gains from human metabolic activity, heat losses due to ventilation, heat gains from auxiliaries, etc. have to be considered in controlling of temperature inside a spacesuit. Therefore this paper focuses on heat transfer and temperature control of space suits.

1 Introduction

Space suit is something beyond general costumes; according to NASA it is much closer to a small spacecraft than a cloth. It serves as an artificial environment for the astronaut while providing him safety from foreign objects

Liquid cooling and ventilation kit has three layers. A bladder layer is placed over the liquid cooling and ventilation kit. The next layer help maintain the proper shape of the bladder. Then there is a ripstop liner and it saves the kit from tearing apart as it is tear resistant. The remaining nine layers are used as thermal insulation measures, and it help reduce temperature changes inside the kit depending on external conditions (Learn About Spacesuits, 2008).

3 Heat Sources and Sinks

In analysis of thermal regulation, identification of heat sources and sinks is essential. Heat sources can be divided into main areas namely heat sources and sinks inside the spacecraft, outside the space craft and inside the space suit.

3.1 Sun

Sun is one of the most prominent heat sources when astronaut is outside the spacecraft, because solar flux is around 10,000Btu per hour (Duncan, 2002). Solar radiation needs proper attention in space suit design as the astronaut is directly exposed to sun rays when carrying out extravehicular activities. When the sun rays are available, the astronaut will face extremely high temperatures of about 120oC, but when sun rays are not present the temperature will reach lower values such as -100oC (Freudenrich, How Space Suits Work). These temperature figures highlight the importance of thermal regulation inside the space

This ventilation effect is crucial as there is no natural air flow to carry away moisture the moisture created by sweating and exhaling.

In this suit, the heat transfer fluid carrying tubes are woven to the fabric. In some designs the heat transfer tubes are allowed to contact the astronaut’s skin directly while some other designs use a separating fabric layer between the heat transfer tubes and the skin. In the second instance the fabric adds an additional thermal resistance for heat transfer conduction, but it improves the user comfort by avoiding the contact of tubes with skin. Flexible plastics are used for fabrication of the heat transfer tubes; PVC and silicone are some common materials used for this (John C. Chato).

When considering the heat transfer characteristics, higher diameter pipes are preferred. Because they provide high heat transfer area and allow high refrigerant flow rates at low pumping heads. But usage of tubes with larger diameter increases the rigidity of the kit which is undesirable for convenient movement of the wearer. Therefore LCVGs uses smaller diameter tubes with low wall thickness. Desired heat transfer rates are achieved by controlling the flow rate and by increasing the number of tubes to increase the effective area of heat transfer (Cengel,