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Online text: www.grc.nasa.gov/www/k-12/airplane/mach.html

Issued and hosted by NASA Glenn Research Center. The footer credits Nancy Hall as editor and NASA official; no individual author byline is established. Last updated 13 May 2021, an online revision date.

Cited passages: speed-ratio definition; gas and temperature dependence; flight regimes; disturbance propagation and wind-tunnel similarity.

Nancy Hall is an aerospace engineer whose NASA biography describes work on fluid mechanics in microgravity. She moved to the Fluid Physics Branch in 1994 and helped researchers use facilities such as a drop tower and reduced-gravity aircraft, as well as prepare proposed flight experiments.^[ref]

In such work, understanding the scientific question and the apparatus are closely connected. A microgravity environment changes the relative importance of gravity compared with other forces acting on a fluid; an experiment must specify the conditions it actually achieves. Her described role linked principal investigators with engineering teams and ground-based facilities, helping translate a proposed measurement into an experiment. The institutional biography provides a historical account of this work rather than a statement of her current assignment.^[ref]

Online text: www.grc.nasa.gov/WWW/K-12/airplane/tunvschlrn.html

Issued and hosted by NASA Glenn Research Center. The footer credits Nancy Hall as editor and NASA official; no individual author byline is established. Last updated 13 May 2021, an online revision date.

Cited passages: slit source, two concave mirrors, knife edge and recording device; density-gradient contrast; dimensional interpretation.