the guidelines that they must be
lightweight, fit inside the cabin of
the command module for transportation and were fairly straightforward to deploy. These options were
ultimately winnowed down into
three finalists: (1) the extension of a
sunshade across the exposed hull
of the workshop, erected by means
of a long pole affixed to the ATM,
(2) a sunshade deployed from the
command module’s hatch whilst
station-keeping or (3) a sunshade
deployed through Skylab’s solarfacing scientific airlock.
Of these, Option 2 was the least
technically complex, although its
key obstacle was that Conrad, at
the command module’s controls,
would be forced to hold position
alongside the workshop, whilst his
colleagues opened the hatch to
put the sunshade in position.
The first option to erect such a
shield would require additional EVA
training. The third option would require the development of a shade
which was capable of passing
through a 20 cm3 opening and then
unfurling to cover an area of 7 m2.
It also meant that the scientific airlock would have to be sacrificed.
Conrad’s crew had already
done extensive EVA training on the
ATM and felt that with the availability of suitable hand-holds and foot
restraints, they could complete Option 1. Similarly, Option 3 was also
‘doable’, because they could at
least work from within the pressurised – but very hot – confines of
the workshop itself. At length, since
no one knew if the scientific airlocks
were cluttered with debris, Option
3 was ranked last. Johnson Space
Center set to work on Option 2, and
the Marshall Space Flight Center
explored Option 1.
The Houston group envisaged
a scenario in which an astronaut
(probably Weitz) would perform a
stand-up EVA (SEVA) in the open
hatch of the command module
and attach the sunshade in two
places to the aft section of Skylab.
Conrad would then manoeuvre his
spacecraft to the forward end of
the station, deploying the shade in
the process and finally Weitz would
www.RocketSTEM.org
make a third attachment at the
ATM. This sunshade very quickly
gained the moniker of ‘SEVA sail’
and its development was conducted under the auspices of Caldwell
Johnson. For ten days, his staff
worked on the shade, seamstresses
stitched the orange material, parachute packers folded it for deployment, engineers attended to its
various fasteners…and a steady
stream of public tours gawped
from a mezzanine gallery at what
was going on.
Meanwhile, in Huntsville, the plan
was to perform an EVA from the ATM
itself. Their sunshade resembled a
window blind and its design was
completed on the evening of 15
May. Kerwin and the backup commander, Rusty Schweickart, flew to
the Marshall Space Flight Center to
participate in underwater EVA tests
of both sunshades.
“One by one,” recalled Schweickart of the exhaustive two-hourplus session, “we eliminated things
and by about midnight…we basically had the outlines of what we
were going to do.”
The Huntsville sunshade needed
further work and the design which
steadily evolved was a configuration of two 14 m long poles, which
would be ‘cantilevered’ from the
ATM. The poles would be assembled from a dozen smaller sections,
allowing them to fit inside the command module, and a rope would
run along their length, through a series of eyelets. The 7 x 6 m sunshade
would be unfurled by tugging on
the rope in a similar fashion to hoisting a ship’s sail. This design came to
be known as the ‘twin-pole’ sail.
An underwater test by Schweickart and Kerwin on 18 May showed
that it would work, but also indicated that its pole sections might separate under stress. A locking nut was
modified, the shade’s weight was
reduced and Teflon inserts were
placed into the eyelets to reduce
friction. Thereafter, the remainder
of the work ran without a hitch.
Meanwhile, the option to deploy
a sunshade from the scientific airlock had been revived and was
steadily gaining momentum, with
Skylab:
The Flown and
Unflown Missions
Skylab 1
The Skylab space station itself was
launched into orbit on 14 May
1973. During ascent, one of the
solar arrays was torn off, together
with the micrometeoroid shield,
and the second array was left
jammed with debris. The launch
of the first crew was delayed as
NASA explored its options.
Skylab 2
The first crew to the space
station consisted of Pete Conrad
(Commander),
Joe
Kerwin
(Science Pilot) and Paul Weitz
(Pilot). They were launched
into orbit on 25 May 1973 and
spent 28 days at Skylab. During
their mission, they performed a
dangerous spacewalk to install
a new sunshade and open the
jammed solar array.
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