Non-Intrusive Gas Temperature Measurement for Stratospheric Applications,
15-R8262
Principal Investigator
Michael L. Fortenberry
Inclusive Dates: 10/01/12 – Current
Background — Finding a non-intrusive technique for determining gas temperature in the stratosphere is of particular interest to the stratospheric lighter-than-air and the meteorological communities. Air is of obvious interest for meteorological interests, and helium is of interest for lighter-than-air (LTA) applications such as balloons and airships. The low-pressure environment of the stratosphere makes it difficult to measure gas temperature accurately, whether the gas is atmospheric air or an internal lifting gas (i.e. helium) for lighter-than-air (LTA) craft. This is due mainly to changes in the relative contribution of convection, radiation and conduction to the thermal balance of objects or gases as altitude increases and atmospheric pressure decreases. At the low pressures found in the stratospheric environment, radiation and conduction play a much more significant role in the thermal balance than they do at higher pressures. For the stratospheric LTA community, determining the internal gas temperature of helium in a balloon or airship (especially if the gas envelope is pressurized) is critical to accurate balloon analysis and in-flight projections for long missions. While obtaining localized (i.e., point) measurements of helium temperature is useful, the ability to obtain average gas temperature measurements over large distances provides a better global picture because of the overall size of the vehicles ranging from a volume of 250,000 cubic feet up to 40,000,000 cubic feet.
Approach — The approach used in this project is to characterize a non-intrusive gas temperature measurement technique suitable for stratospheric LTA applications. The two techniques to be investigated, thermistor array and acoustic, are drastically different in operational principle and each technique could be useful in an operational environment if they provide accurate measurements.
Accomplishments — This is an on-going project that should be complete early in 2013. An acoustic methodology is undergoing test currently. Testing and analysis of data should be finalized by early 2013.
