Project Excelsior can you parachute to earth from space?


Note: these articles have been published in InfoChem, the supliment to Education in Chemistry produced by The Royal Society of Chemistry.

What's really amazing about Joe Kittinger's space flight (The Planets, BBC TV [1]) is not just that it's footage of the first manned trip into space but that you see him make the trip without a spacecraft!

In 1960, a year before the Soviet Yuri Gagarin made his historic single orbit around the Earth in a spacecraft, Joe Kittinger's US air force team were pioneered high altitude helium balloon ascents. Project Excelsior aimed to fly to 31 km (100,000 feet) in a balloon supported gondola. His only protection from the changes in atmosphere and harsh solar radiation was a very basic spacesuit. This suit also controlled his temperature and supplied him with air.

The earth's atmosphere consists of 78% nitrogen, 21% oxygen, 1% argon, 0.04% carbon dioxide and of course traces of other gases including large amounts of water. Although there is no sharp cut-off point, by 20km the atmosphere is so rarefied it is basically considered as space. Most of the atmosphere is near to the earth's surface: 75% of the mass of the atmosphere is contained within the first 11 km. The weight of the gas above us produces the atmospheric pressure. If you go up into the atmosphere there is less weight above you and so the pressure drops.

At an altitude of 15 km Kittinger's right hand spacesuit glove developed a hole and started to leak. The outside pressure at these altitudes is so low that the skin around the hole was therefore exposed to a vacuum. The water and blood in his hand would start to evaporate at such low pressures. Rather than abort the historic mission he simply plugged the hole with his other glove and continued on!

An hour and a half after lift-off he was at 31km (103,000 feet). Here the air is so thin that the characteristic scattering of sunlight by the atmosphere, which makes the sky appear blue, does not take place and so Kittinger found himself looking out into black space. At this altitude the ambient temperature is around -70 °C [2].

Once up at this altitude he spent just a few minuets making routine measurements and then set up his equipment for his descent. Then he simply stepped off the gondola to make a free-fall parachute jump back to earth. At first he felt no sensation of falling because the pressure / density of the atmosphere were too small to make an impact. Within a few minuets though he arrived back into what we would consider the main part of the earth's atmosphere and at 5.5 km he pulled his parachute cord and, completing this amazing trip, landed safely.

[1] The Planets, BBC TV, 1999 series, video or DVD, see episode 6 Atmosphere.
[2] Eyewitness Companions - Weather, DK & Met Office, HMSO 2008. ISBN 978 1 4053 3093 0

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THE CREATIVE SCIENCE CENTRE

Dr Jonathan Hare, The University of Sussex
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