AirCore^® System Miniaturization, Validation, and Verification, 16-R8166

Principal Investigators
Thomas H. Jaeckle
Kristin A. Favela

Inclusive Dates:  07/01/10 – 07/01/11

Background - AirCore^® is a copyrighted term that refers to a coil of stainless steel tubing used for collecting air samples for the purpose of measuring greenhouse gases (GHG). This sampling technique was developed by scientists at the National Oceanic and Atmospheric Administration Climate Monitoring Division and is a breakthrough in the sampling of GHG in the upper atmosphere. The AirCore is carried aloft on either an aircraft or a balloon, self-evacuates on ascent, and provides a sample of the air through which it passes as it descends. NOAA has demonstrated that the GHG do not rapidly mix within the tube. Hence, the location of the GHG within the tube provides a means of determining concentration of these gases as a function of altitude. However, the current AirCore coil is heavy and requires special coordination with the Federal Aviation Administration when carried aloft by a balloon. This limits where the AirCore can be used, and because the AirCore descends on a parachute, makes determining where it will land problematic. SwRI has developed an autonomous stratospheric glider system called Skywisp^® that can be launched without FAA coordination and reliably returns to a designated landing zone. However, the Skywisp glider cannot carry the AirCore coil in its present embodiment. This project will investigate reducing the current AirCore to a size and weight that can be flown on the Skywisp without sacrificing the ability of the coil to provide GHG concentration data as a function of altitude. It will also greatly increase the probability of timely recovery of the sample and improve the safety of operations.

Approach - Gas chromatograph capillary tubing will replace the stainless steel coil used in the current AirCore. This tubing, which is made from fused silica, is both lighter in weight and smaller in diameter. The length and inner diameter of the capillary tubing will be selected to produce similar gas-flow characteristics as the steel AirCore tubing. Computer simulation will be used to determine the necessary combination, and laboratory measurements will be conducted to confirm these dimensions. Once a combination of length and diameter are determined and verified to preserve the integrity of the sample, further testing will be conducted to determine how accurately and precisely the molal fractions of the GHG of interest can be measured. Because the volume of the capillary tube will be much smaller that the steel AirCore, different types of mass spectrometers will be evaluated to determine which instrument can provide the required accuracy with the smaller sample size. The miniature coil will then be integrated on a Skywisp glider, and necessary changes to the airframe and control algorithms for the aircraft will be implemented. The Skywisp glider is limited to a gross weight of six pounds in order to be launched under Section 101 of the Federal Aviation Regulations as a weather balloon payload. The silica tubing has a minimum bend radius, and the airframe may require modifications to accommodate the coil. The project will include a flight to the stratosphere to collect the GHG of interest. Because modifications to the airframe will require modifications to the control algorithms, the airframe will be tested after the coil has been installed. Once completed, the smaller coil will be carried aloft on the Skywisp glider to collect a sample of GHG in the stratosphere for analysis, validation and verification.

Accomplishments - This project was awarded on July 1, 2010, and is in the early stages. Computer simulation has commenced and long-lead-time items have been ordered.

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