One of the experiments proposed for suborbital spaceflights is the collection and return of particles from the near-space environment, some of which might contain the building blocks of life.  In 1935, scientists performed a similar experiment to collect spores in the upper atmosphere.  The 1935 experiment had no exobiology goals; rather, it was to determine if living spores, fungi, or bacteria were present in the stratosphere.

The experiment was carried aboard the US Army Air Corps/National Geographic Society Explorer II balloon flight.  Explorer II took off from the Stratobowl, near Rapid City, South Dakota, on November 11, 1935.  The Stratobowl was a large natural depression that provided protection from surface winds during balloon inflation and the early part of the flight.

The National Geographic Society and the US Army Air Corps sponsored a pair of high altitude balloon flights in 1934 and 1935, Explorer I and Explorer II, respectively.  Explorer I flew on July 28, 1934.  Major William Kepner and Captains Orvil Anderson and Albert Stevens reached an altitude of 60,613 feet when their balloon failed.  The trio barely jumped away from the plummeting gondola in time before it smashed into the ground.

In February 1935, the Army and National Geographic Society announced there would be a second Explorer flight.  Since the original Explorer capsule was destroyed, a new one had to be built. Explorer II was much roomier than its predecessor; it was nine feet in diameter.  Contributing to the sense of spaciousness, Explorer II had a crew of only two — Captains Anderson and Stevens.

The Explorer II balloon was truly gigantic, with a volume of 3.7 million cubic feet.  The Goodyear Zeppelin Corporation built the balloon from fabric procured from the Wellington Sears Company of New   York, an experienced supplier of fabric for airplanes.  The balloon weighed 6,500 pounds, comprised nearly 3 acres of fabric and took 1,685 cylinders of helium to inflate.

Lift off occurred at 7:01 a.m., Mountain Standard Time, on November 11, 1935.  Hundreds of people gathered around the top of the Stratobowl to watch the ascent.  The capsule had just cleared the walls of the bowl when the balloon was caught in a strong down draft.  Fearing a crash, Anderson and Stevens dropped 750 pounds of lead shot ballast.  Lighter, Explorer II ascended over the South Dakota Badlands.  The pilots clambered outside the capsule, amongst the rigging.  When they reached 16,000 feet, they climbed into the sphere and sealed the hatch.  Testing the capsule for leaks, they pressurized the cabin to the equivalent of 13,000 feet.  They maintained this pressure throughout the flight.

Three hours and 29 minutes after launch, Explorer II reached 65,000 feet.  The balloon was inflated to its full 192-foot diameter.  Anderson dropped ballast, gently coaxing the balloon higher.  At 11:40 a.m., Explorer II settled out at 72,395 feet.  From such a great height, the aeronauts saw mostly patches of green or brown on the ground.  Railroads were the only recognizable features, and then only by an occasional cut or fill.  Large farms could be picked out by their rectangular patterns.  The sky above them was a darker blue than on the American flag that hung from the rigging.

Around noon, they began their descent.  Once Stevens was sure they were on the way down, he dropped a device that would collect airborne spores down to an altitude of 36,000 feet.  At first, the parachute did not open, but it must have, because the device was recovered intact and returned to the U. S. Department of Agriculture.  Subsequent analysis revealed ten types of spores, bacteria, and fungi had been collected.  This was considered important because this was the first time that living spores had been found above 36,000 feet in the atmosphere.

The apparatus comprised a 4-inch diameter glass tube contained in a tubular aluminum casing.  Air flowing through the casing passed through the glass tube.  The inside surface of the glass tube was coated with 60% glycerine, which retained its sticky consistency at the low temperatures found in the stratosphere.  Wads of cotton at each end protected the tube from contamination.  Cotton-covered aluminum dampers closed the ends of the casing.  The dampers were attached to an arm and were held open by springs.  A barometric bellows assembly held the dampers open above an altitude of 36,000 feet.  As atmospheric pressure increased during descent the bellows contracted and released the dampers.  A parachute attached to the housing held the collector in an upright position during descent so air would pass through the tube.

The apparatus and its main parachute were enclosed in a bag made from two layers of flannel attached to a second parachute.  Metal clips sealed the flannel bag.  When the parachute inflated, it released the clips and pulled away the cotton wads.  The entire device in its flannel bag was mounted in a canvas bag that could be opened from inside the gondola.  Before the flight, the entire apparatus, including the canvas outer bag, was sterilized in an autoclave for 1 hour at a temperature of 120o C.

Stevens and Anderson opened the canvas bag at an altitude of 71,395 feet, after the balloon was already descending.  This was done to minimize the chance that the collector might be accidently contaminated by spores or bacteria carried by the balloon.

The pilots also collected samples of the “rarefied air” for later analysis.  More than 15,000 photographs were taken during the flight.  Scientific results of the flight added to the world’s understanding of cosmic rays, the solar spectrum, and conditions in the upper atmosphere.

Throughout the flight, Stevens talked with engineers from the National Broadcasting System (NBC) who were on the ground at Rapid City.  He even talked, via an NBC relay, with the pilot of the Pan American China Clipper over the Pacific.  These transmissions were broadcast live over the NBC system.  The banter continued until the balloon reached 16,000 feet, where Anderson and Stevens opened the capsule’s hatches.  They dumped their remaining liquid oxygen and liquid nitrogen, then dropped batteries (on parachutes) and ballast to control the final descent.  In preparation for landing, the pilots donned leather football helmets loaned to them by the Rapid City High School team.

Anderson and Stevens saw a large open field and agreed it would be a good landing area.  Anderson called to Stevens “Make ready for landing!”  Glancing through the porthole in the bottom of the capsule, Stevens saw they were only a foot or two off the ground.  They pulled the rip cable that opened the top of the balloon.  The capsule touched down and rolled over on its side.  Stevens and Anderson climbed out to the cheers and congratulations of the crowd that had gathered.  Their flight had lasted 8 hours, 13 minutes, and they landed near White Lake, South Dakota, about 225 miles east of the Stratobowl.

The spore collection experiment was found shortly after landing – directions for its return to the US Department of Agriculture were attached to the casing.  From the glycerine, researchers developed five colonies of bacteria and five colonies of mold.  The species of bacteria were not identified, but were found to be aerobic spore-forming rods of five distinct varieties.  As for the molds, the types found comprised Rhizopus; Aspergillus niger; Aspergillus fumigatus; Penicillium cyclopium, and Macrosporium tenuis.

Written by Greg Kennedy on November 10th, 2013 , Space History

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