Encyclopedia Astronautica
1973.05.26 - Second manned day of the Skylab mission.


The second manned day of the Skylab mission was focused on entry into the OWS and deployment of the Skylab parasol.

The crew removed and inspected the docking probe and drogue. They then entered the MDA to activate the airlock module and MDA systems.

The crew entered the OWS at 3:30 p.m. EDT. The atmosphere, although hot, was habitable, and the crew was able to work in the environment for 10- to 15-minute intervals. At 5:00 p.m. the crew began deployment of the parasol; the task was completed at 7:30 p.m. The parasol provided thermal shielding for the area of the Workshop exposed to the Sun because of the missing meteoroid shield. The parasol concept, design, development, construction, and delivery to KSC was completed in seven days by JSC.

Two other thermal protection devices were also devised and delivered during this same time period. One was a sail, produced by JSC and designed to be deployed by an extravehicular crewman standing in the command module hatch while the spacecraft was being flown in close to the OWS. The other, called a twin-boom sunshade and produced by MSFC, was designed to be deployed by extravehicular crewmen from the ATM station. The parasol provided a thermal protective device which was simple, and deployment could be accomplished from within the OWS in a shirt-sleeve environment. The system was capable of being jettisoned.

The parasol concept made use of a spare experiment T027 (ATM contamination measurement) canister which was designed to interface with the solar scientific airlock. The seal design used in the back plate of the experiment canister was incorporated into a new back plate required for the parasol. This allowed the use of deployment rods which were of the same type used for experiment deployment, and also allowed use of the experiment T027 photometer ejection rod, if jettisoning became necessary.

Major components of the parasol, other than the modified canister, were a 6.7 by 7.3-m aluminized Mylar/nylon laminate canopy that was partially opaque to solar thermal energy, a canopy mast, a mast hub with deployment springs, four telescoping deployment rods, seven extension rods, and the experiment T027 canister support tripod.

Deployment was accomplished through the solar scientific airlock by attaching the extension rods to the mast and pushing the rod assembly outward. As the mast hub was extended to 4.9 m above the opening of the airlock, the telescoping deployment rods became fully extended and locked and the tip retainers for the telescoping rods were released. The mast hub was then extended to 6.4 m above the outer surface of the OWS, allowing the rod tips to swing free of the solar scientific airlock opening and deploy the canopy. The parasol was then retracted to its final position a few centimeters above the OWS outer surface

During the retraction process, the long extension rods were removed, and the short extension rod was left in place. OWS temperatures started dropping immediately upon parasol deployment. The initial temperature drop for the outer wall exceeded 36 K (65°F) per hour. Temperatures within the OWS, though dropping at a much slower rate, were below 311 K (100°F) within a day of deployment. The inside temperature continued a steady decline until stabilization was reached somewhat below 297 K (75°F). At the end of the first visit, the temperatures increased because of the increase of daytime exposure for the orbital plane at that time of the year.

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