flights have been saved since 1993. If we assume that half of these would have gone
to the South Pole (6-hour round-trip) and half to Christchurch (16-hour round-trip),
more than 1340 flight-hours have been saved. An accepted cost for the Hercules
(including fuel) is 00 per hour, which results in a cost savings to date of more
than million.
LIMITS TO LIFE EXPECTANCY
Being located on a glacier, the Pegasus runway is moving. The current movement
is at a rate of about 1 to 2 ft per year northward. This is a favorable direction from the
standpoint of the glaciological conditions at the site. The ice shelf edge is currently
located about 2 miles north of the north end of the runway. It is virtually assured that
the ice shelf will calve in this area at some time in the future, but when this will
happen, and how far into the shelf the break will occur is completely
unknown. We speculate that other factors will cause deterioration of the site before
the runway calves and heads out to sea.
It is also unlikely that crevasses or other cracks will invade the runway site. Since
the site is located "downstream" and some distance from constrictions on the ice
mass, there is no source of deviatoric stress to produce large cracks.
Mineral particles from nearby exposed rock sources (e.g., Black Island), blown
onto the runway by storms, may provide the biggest threat to the longevity of the
runway. Over the past four years, strong winds have on a number of occasions de-
posited bands of small mineral particles throughout the region of the runway. How-
ever, in only one case has there been mineral contamination blown onto the runway
itself.
Contaminants from equipment and personnel on the site must also be consid-
ered. Fuel, oil, or coolant leaks and spills could be difficult to clean and could be
devastating to a portion of the runway or support areas.
If an exceptionally warm summer were to occur, the techniques we have estab-
lished are likely to the fully protect the runway from melt problems. However, free
water occurring in the vicinity of the runway might be expected to flow on the ice
surface and could infiltrate the runway.
Construction and maintenance activities at the site have altered the topography
of the snow surface. This could result in a change in the natural balance of accumu-
lation/ablation, which will undoubtedly increase the amount of work required to
maintain the runway. Substantial berms are now present along both sides of the
runway. To avoid serious snowdrifting problems, the berms must be significantly
reduced in size during the next summer season. Ultimately, snowdrifting could still
threaten the life of the runway over the long term.
The Pegasus site was deliberately chosen on the fringe of a large established abla-
tion region. If a climate change occurs (e.g., a series of abnormally warm summers or
an increase in solar intensity due to depleted ozone), the edges of the ablation region
may move outward, thus threatening the runway's integrity.
Further experience with the Pegasus runway, and continued research into the
natural dynamics of the site will result in means to cope with each of these threats.
From our current experience at this site, we believe that the runway could be made
to operate successfully for at least 10 years unless a calving event occurs and threat-
ens the runway.
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