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More Balloon Astronomy.

Laura Fissel's "Science in the Stratosphere" (S&T: Feb. 2018, p. 14) brought to mind another noteworthy balloon flight. On May 6, 1958, astronomer Alfred Mikesell and Navy pilot Malcolm Ross ascended in an open gondola to measure he twinkling of stars to determine where in the atmosphere this phenomenon occurs. Mikesell thought it occurs at the tropopause rather than in the stratosphere. To prove this idea he brought a photoelectric photometer attached to a small telescope with an electronic recorder.

They began their flight from an open-pit iron mine near Brainerd, Minnesota. Launching below ground level let them avoid the strong afternoon winds while filling the balloon with helium. As an extra precaution, Ross overfilled the balloon to ensure a rapid vertical ascent out of the pit.

Unfortunately, two problems resulted. First, the vertical speed was well over 1,000 feet per minute, which took them to the target elevation of 40,000 feet in just 30 minutes, much too fast for making scintillation measurements at intermediate elevations. Second, the balloon rose in a spiral that twisted the support straps, which in turn caused the 2,500-pound gondola to revolve like a giant torsion pendulum throughout the entire 12-hour flight. It was impossible to aim the telescope at a star long enough to record data.

Even though the primary purpose of the mission failed, Mikesell made an important discovery that would later benefit the space program. He and Ross were wearing standard-issue Navy cold-weather clothing with lots of fabric layers. Previously they had worn this clothing in a test chamber down to temperatures of -77[degrees]C (-107[degrees]F), yet the instant they reached the stratosphere they felt cold far more intense than they had encountered in the test chamber. At that altitude, their suits couldn't adequately prevent the heat loss from their bodies. Researchers later discovered that a thin layer of aluminum covering the fabric significantly slows the loss of body heat. Thus we have the familiar shiny suits worn by today's astronauts.

Darryl Davis * Albany, Oregon

For more details about this flight, visit www.mikesell.info.

Caption: Sixty years ago, Navy pilot Malcolm Ross (pictured) and astronomer Alfred Mikesell flew a balloon into the stratosphere to study the scintillation of starlight.

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Title Annotation:FROM OUR READERS
Author:Davis, Darryl
Publication:Sky & Telescope
Article Type:Letter to the editor
Date:Nov 1, 2018
Words:375
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