Foamcore Payload Construction

by

Mike Manes, W5VSI SK
EOSS

1^st Ed: 5/24/93
2^nd Ed: 3/28/01

Note to 2^nd Ed: The 1^st Ed of this paper was published in Proceedings of the First National Small Balloon Symposium, EOSS, 06/1993.  This 2^nd Edition has been converted to a Word97 file, Fig. 1 has been embedded, sketches illustrating miter joints added, and some material has been updated.

ABSTRACT:  Foamcore sheet is a versatile and inexpensive material for use in fabricating custom balloon payload enclosures.  Salient properties, design and construction techniques and flight experience are described.

Life for a high-altitude balloon electronics package can be rough.  At birth, it’s crammed full of radios, electronic goodies and batteries, and its skin is perforated with connectors and antenna feedlines and emblazoned with ham graffiti.  Unnecessary appendages are chopped away to save weight.  It flops around a workbench for weeks while its guts are tweaked and twisted with accelerating fervor as launch day approaches. 

At the crack of dawn on the appointed day, it’s rustled up and jostled out to some desolate spot, where it gets a few more pokes and jabs for good measure before being bound and strung up like a horse thief. 

With a sudden jerk and a sigh of relief, it’s hoisted up and away from its earthly turmoil.  But soon it faces even more grueling insults.  As it ascends at over 10 mph, rushing air tugs at its supports, and wind shear tosses and twists it like a small boat on high seas.  Its internal gasses belch forth as it rises through ever thinning air.  Passing through the depths of the tropopause makes New Year’s Eve at the North Pole seem like a tropical beach party.  Rising into the stratosphere provides a welcome respite, as the nearly non-existent air becomes calm, and everything warms up in the intense, unfiltered sunlight blazing forth from the black sky. 

Just as life seems to getting a bit cozy, the support lines suddenly go limp, and our package finds itself plummeting helter-skelter down into the sky below.  Whatever vestige of warmth may have penetrated its skin is ripped away by 200 mph winds, and the frigid tropopausic air forces its way into every crack, chilling its viscera to the core.  After surviving another roller-coaster ride through the jet stream, the infiltrating air begins to warm, allowing it to carry quite a bit of water.  In fact, the welcome shade of a cloud can fill our package with fog which readily condenses all over its frigid guts. 

The ever-calming ride back to the planet ends with perhaps the most severe assault of all: a collision with the earth which would total a modern car.  If the surface wind has picked up since the launch, the parachute will keep on plugging, bouncing its dazed passenger across whatever the surface may be until something strong and stationary snatches the package and wins the tug of war. 

After what seems like an eternity in an even more desolate site, a swarm of fiercely-armed T-hunters converge on our voyager, attracted by plaintive cries for help driven by dying batteries though an antenna which may be buried up to its feedpoint.  After a primitive ritual, the victorious captors load their quarry once again into a vehicle, this time with much less ceremony, for a considerably longer jostle back to its spawning grounds. 

The next day, its creators commence their poking and jabbing again, scratching their heads in search of an explanation of how such a hastily crafted package could have survived its ordeal without dumping its contents all over the recovery site or even showing even moderate signs of wear. 

“Foamcore”, they finally proclaim, “It might have been the foamcore!”