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05.19.99 diary entry



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AIAA Abstract
Monday, 02.23.04


Quote of the Day:
�The difficulty, you see, isn't so much getting power as holding on to it.�
The Foundling by Lloyd Alexander


Here is the abstract for the paper I am going to submit for AIAA student conference. The actual paper hasn�t been written yet, but the abstract was due today so my advisor and I drew this up from previously published material. Many thanks to Indy and Caesar, my predecessors on this research project, whose words I paraphrased in order to write this abstract.

Over the years, safety concerns in rocket propulsion systems have led to the practice of conducting leak tests with an inert gas and to try to infer the fuel leak rate from the inert gas data. The so-called Helium Signature Test (HST) has been used in this sense to estimate leakage of fuel from high pressure hydrogen tanks. The present experimental study sought to extend a prior study by our group on the validity of the HST to much higher pressures and lower temperatures. Simulated leak sources were fabricated by micromachining holes of prescribed shapes and cross-sectional areas in silicon wafers, utilizing the processes of photolithography and deep reactive ion etching. Dual thermal conductivity detectors were used to evaluate helium and hydrogen leak rates. While prior studies compared actual hydrogen leak rates at moderate pressures and room temperature with those predicted from helium measurements at low pressures and room temperature, the focus of the present study is on estimating hydrogen leak rates at very high pressures and room as well as low temperatures from helium leak rates at both room and low temperatures. Based on this quantification, the standard HST procedure was found to underpredict hydrogen leak rates, in some cases by as much as 45%, if the corresponding helium tests are conducted at much lower pressures than those at which hydrogen leak rates are sought.

-Lauren Gleason