Skylab 3 began at 7:11 AM EDT on Saturday, July 28, 1973. One of the major objectives of the flight, which was crewed by Alan L. Bean, Owen K. Garriott, and Jack R. Lousma, was to double the duration of the previous mission. The flight nearly came to an early end, however. During the maneuvers to link up with the orbiting station, Bean reported seeing “some sort of sparklers” out of his window. At the same time, Mission Control noticed a pressure drop in one of the assemblies of maneuvering rockets on the Service Module. Flight controllers quickly decided the rocket assembly was leaking propellant and told the astronauts to shut it down. Skylab 3 continued and successfully docked using the remaining maneuvering rockets.

Six days later, another thruster began leaking and had to be shut down. This posed a serious problem, because the thrusters were needed to properly orient the Apollo Command and Service Module (CSM) for retrofire and return from orbit. Mission controllers feared the leaks indicated a major failure of CSM systems that could leave the astronauts unable to return home.

Engineers on the ground studied the problem while others prepared another Apollo to rescue the astronauts who were potentially stranded in space. The latter preparations included modifying the Command Module to accommodate five rather than three crew couches. If needed, the rescue craft would be launched with a crew of two, who could dock with Skylab then bring everyone home. These preparations proved unnecessary — the two leaks were unrelated, and did not indicate a general system failure as first feared. A stuck valve caused one of the leaks; the second was due to loose fittings. The remaining thrusters checked out perfectly and the mission proceeded normally.

The parasol erected by the first crew had deteriorated from micrometeoroids and the harsh, unfiltered solar radiation, so the second team of astronauts had to deploy a second shield. Garriott and Lousma deployed a “twin pole” sun shade above the parasol during a six and a half hour EVA on August 6. While outside the station, the astronauts also loaded film canisters in the Apollo Telescope Mount (ATM), installed panels to catch micrometeoroids, and inspected the troublesome maneuvering rockets on the Service Module.

Skylab 3 proved to be a bonanza for science. During the course of their 56-day flight, the astronauts collected nearly 16,000 pictures of the earth and about 18 miles of magnetic tape recordings of additional data. They made 39 successful earth observation passes, rather than the planned 26. Each required changing Skylab’s usual sun-oriented position so the earth observing instruments were pointing straight down. Bean, Garriott and Lousma obtained 77,600 telescopic images of the sun. In all, they spent more than 300 hours on solar astronomy, which was 100 hours more than expected.

The Skylab 3 astronauts discovered that solar flares — massive outbursts of matter from the Sun’s surface — sometimes arch back to a different area of the sun and trigger new flares. Scientists on earth had long suspected this, but had never observed it. They also observed the life history of sunspots, which are relatively cool, dark areas on the Sun.

Project Skylab included opportunities for high school students to fly experiments in space.  Two of the student experiments flown on Skylab 3 attracted a great deal of public attention. The crew carried two common cross spiders into space and allowed them to construct webs to see how weightlessness affected them. The first to build a web was named Arabella. Arabella’s first web was very irregular, which led to the conclusion that she was disoriented by weightlessness. After a few days, Arabella began spinning webs that closely resembled those made on Earth. Garriott commented: “It seems she learned very rapidly in zero-g without the benefit of any previous experience.” The second spider, named Anita, was allowed to spin webs later in the flight, after she’d had time to adapt to zero-g. Anita’s webs looked normal almost immediately. Another student experiment involved Mummichug minnows. Minnows hatched on Earth, then launched into orbit, swam tail up in tight loops. A second batch that was hatched in space swam normally. Scientists were unable to explain the difference in the two groups’ behaviors.

With an eye towards future space operations, NASA had the astronauts test several maneuvering units inside the Orbital Workshop. Johnson Space Center sponsored the “Astronaut Maneuvering Unit,” experiment M509. This experiment actually comprised two separate maneuvering units. The first, and most elaborate, was a backpack with controls on the ends of arm rests and nitrogen jets on the unit’s corners. The left handle controlled translation; the right one rotation. Crewmembers who tried the M509 back pack found they could maneuver very precisely, and could even maintain a constant distance from the curved inner wall of the workshop as they flew around its circumference. Even those who had not trained to fly the unit before launch quickly mastered its controls. During the Skylab flights, five astronauts accumulated a total of 14 hours operating the maneuvering unit.

M509 included a hand held maneuvering unit (HHMU) similar to ones used during Project Gemini. During Mike Collins’ EVA on Gemini 10, there were indications the HHMU introduced unwanted rotational movement when its gas jets were fired, but the results were inconclusive. Proponents of the hand held device pointed to its simplicity and were sure weightless astronauts could easily learn to fly with it. Gemini astronauts practiced with the device on an air bearing table, which provided a two-dimensional analog for weightlessness. Skylab provided an opportunity to test the HHMU under controlled circumstances in three dimensions. The HHMU proved less than satisfactory — it induced a tumbling or rotational motion as hinted by the Gemini flight experience.

Langley Research Center provided the third maneuvering device tested on Skylab, the T020 “Foot Controlled Maneuvering Unit,” or FCMU. The concept behind the FCMU was relatively simple, and was based on an assumption of “inherent stability” on the part of human beings. Langley engineer John D. Bird studied the Hiller Flying Platform, a ducted fan that the pilot steered by leaning in the desired direction of travel. Bird felt the Flying Platform “demonstrated man’s inherent ability to control a thrust vector pushing against the soles of his feet.” If a person could steer the Flying Platform by leaning in the desired direction, he reasoned, why couldn’t the same idea work in space? Why not attach maneuvering jets to an astronaut’s shoes to leave his hands free? By simply leaning in the direction he wanted to go, the space man could maneuver easily and precisely.

When first envisioned, the FCMU comprised a single nozzle that would be attached to an astronaut’s boot. Later versions of T020 resembled the frame from a set of roller skates with rocket nozzles facing fore and aft at the toes and heels. By the time it flew, the T020 FCMU evolved into a more complex device that resembled a unicycle. The astronaut sat on a saddle and placed his feet in holders that contained switches. By raising or lowering his toes, the pilot selected the thrusters to be fired. Most of the astronauts who flew the FCMU felt it was cumbersome and more trouble than it was worth.

Skylab 3 splashed down in the Pacific Ocean on September 25, 1973. Bean, Garriott and Lousma set a flight endurance record of 59 days, 11 hours, and 9 minutes. Post flight medical examination showed they’d adapted well to weightlessness, and NASA managers seriously considered an even longer flight for the final Skylab mission.

Written by Greg Kennedy on July 23rd, 2013 , Space History

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