by Jay Chladek
Pruning Sheers, Parasol, and a Sunshade
When the problems were more fully understood, a plan of action began to take shape all across the NASA centers, while investigators tried to find out what caused the micrometeoroid shield to be torn away. Investigations would later determine that the shield had been poorly designed. While the lab was ascending through the atmosphere, a trapped air pocket began to expand; the resulting gap, in combination with aeropressure loads from the rocket’s flight, caused the shield to tear away. When the shield went, it took one of the solar wings completely with it, and twisted metal jammed the other one shut. If the stuck wing could be freed, it would give Skylab 50 percent more electrical power generation than it had with just the ATM solar arrays.
Parallel efforts took place at the NASA centers to deal with both the solar array and the heating problem. Skylab backup mission commander Rusty Schweickart (a veteran of Apollo 9) and Joe Kerwin both took turns in Marshall’s NBT to test procedures and equipment for freeing the trapped solar array. The plan was easier said than done, because while Skylab had been designed with EVA handholds around the ATM for the retrieval of film canisters, no such provisions were found around the rear of the workshop since there were no plans to conduct EVAs there. The closest EVA handholds were quite far from the site of the damage, so an astronaut would have extreme difficulty getting in position to cut any metal that might be holding the array in place.
It was also considered too dangerous to make any cuts with an astronaut close by, as the potential stored energy in a strap or attachment bracket could turn it into a projectile once it was cut. If an astronaut got hit, it could be a very bad day. Finally, engineers settled on a variation of a set of pruning sheers mounted on a telescoping pole, similar to the type used by workers to safely cut small branches on tall trees or electrical lines. A worker used a rope-and-pulley system to actuate the jaws of the cutter. The telescoping handle for the cutter was broken down into segments small enough to store inside the CSM cabin. The full-length pole would then be stacked together during the EVA.
For the thermal problems, engineers at both Marshall and JSC came up with solutions. The JSC team devised a folding parasol, or what essentially is a giant umbrella, much like what is used to keep picnic tables cool during outdoor gatherings. The parasol would be deployed through the scientific airlock on top of the station, as the airlock’s opening was in the area exposed by the missing shield. Unfurling the parasol would be akin to threading a folded umbrella through the tiny opening of a car’s sunroof and popping it open. The airlock and parasol deployment mechanisms were designed in such a way as to keep the interior of the station pressurized, while the shade itself was deployed from a modified scientific airlock experiment canister. The whole thing looked like a Rube Goldberg contraption, but if it worked, it would help save Skylab. The only minor problem is that experiments intended for deployment from the scientific airlock could not be used, as the airlock would be out of commission for the remainder of Skylab’s service life. Some of those experiments would eventually be placed outside the lab in racks and later retrieved during EVAs to service the ATM’s film canisters.
Marshall came up with a twin-pole sunshade design. It resembled a giant awning. Plans for deployment called for it to be erected from two telescoping poles that were joined by a base plate to form a giant V shape. The baseplate was mounted on the truss structure used to support the ATM. Two reefing lines on the edges of the cover would pull the sides of the shade nice and taught over the exposed side of the OWS. These reefing lines would then be passed through parts of the docking module’s support structure; the free ends were secured to the left and right sides of the ATM itself. The sunshade was capable of covering more of the lab’s structure than the parasol but required a space walk to deploy it.
18. Astronauts Kerwin, Conrad, and Weitz (left to right) made up Skylab’s first crew. Courtesy NASA.
The decision was made to fly both the parasol and the sunshade, along with the cutter. The parasol would be used first, and the sunshade would be deployed later, after the stuck array was addressed. Work on the shades and the cutter took place almost around the clock. The final piece for the parasol was delivered by a NASA jet to KSC only a few hours before the launch. The crew of the first Skylab manned mission had nearly every resource of NASA at their disposal to save the laboratory. Long hours were put in by engineers, astronauts, and contractors, and everyone worked together toward a common goal. The stakes were very high.
“We Fix Anything!”
On 25 May 1973, almost two weeks after the crippled Skylab entered orbit, the program’s first manned crew was ready for launch aboard Skylab 2. At 07:00 Houston time, the first manned Saturn IB to launch from pad 39B roared off its milk stool. A few seconds after liftoff as the rocket cleared the launch tower, Pete Conrad proclaimed, “[Clear] tower and Houston, Skylab TWO! We fix anything! We’ve got a pitch and a roll program.” And the rocket began its preprogrammed arc to achieve orbit. A few seconds later, Conrad proclaimed, “Boy, is that a smooth ride!” It was rather cloudy at KSC, and some low rain clouds began to move in over the viewing areas right before launch. So it didn’t take long for the rocket to disappear into a cloud layer. Thankfully—unlike Conrad’s last trip into space, on Apollo 12—no lightning strikes were reported that day.
Rendezvous took place almost on schedule; as the CSM closed with the lab, the crew conducted a fly-around inspection and were able to survey the damage for themselves. As predicted, the micrometeoroid shield was completely gone, and so was the left-side solar array. The right array was jammed shut and held in place by a one-centimeter-wide retaining strap that was firmly stuck to the rivets around it. Television pictures transmitted to the ground gave mission controllers their first look at the damage. A first attempt at trying to free the jammed solar array was made with Paul Weitz conducting a standup EVA outside the CSM while Joe Kerwin held his legs. From the pilot’s seat of the CSM, Conrad tried to station keep with the lab while Paul tried to free the stuck array. It ended up becoming an exercise in frustration, though, as the only thing the astronauts really succeeded in doing was adding multiple four-letter obscenities to the flight-communications loop. The decision was made to abandon the task after a couple of tries.
Docking didn’t go well, either, as the CSM’s docking probe did not properly mate with the drogue assembly on the station. Backup procedures were tried, but to no avail. The last procedure that the crew tried before calling it quits was to climb back into their EVA suits, depressurize the cabin, open the docking tunnel, and remove the back plate from the probe mechanism to bypass some electrical connections that were causing the problem. Then, after the probe and drogue were aligned with one another visually, the CSM’s thrusters were used to try to engage the docking latches. It worked, and the CSM was firmly docked with Skylab. The crew retired for a good night’s sleep in the CSM at the end of a twenty-two-hour day.
The next day, the crew took air samples from Skylab to see if it was safe and entered the workshop. Their first order of business was to deploy the parasol, which they did. While it didn’t quite cover all the affected area, the internal temperature began to come down over the next three days before finally stabilizing at a slightly high yet still-comfortable 26 degrees Celsius (78.8 degrees Fahrenheit). Initially, the crew would spend much of their time in the CSM or the airlock module, where it was cooler. But as the temperature came down, normal Skylab operations began, and the crew settled in.
19. Skylab’s missing micrometeoroid shield and jammed solar wing are visible in this photo. Courtesy NASA.
Eventually, though, the jammed solar array had to be unfurled, as degraded battery performance from heat exposure and the station’s power requirements meant that Skylab’s power-generation capability was running on the ragged edge. In the NBT at Marshall, Rusty Schweickart had been running simulations on ways to cut the strap on the jammed solar array, and a procedure was devised where one crewmember would
attach a set of lines to part of the solar array’s housing. These lines would be used to pull the erection boom free once the strap was cut. The second astronaut would anchor himself to the lab halfway up the side of the OWS and cut the strap with the pole device. The strap would still be about eight meters away from the astronaut with the pole, so it would require a bit of work for the cutter operator to anchor his position and manipulate the pole without coming off the lab. If the task did not succeed, although the first Skylab crew could still complete its mission with the power available, there was doubt that the second and third crews would be able to do so. Success or failure of this repair would determine Skylab’s future.
For the job, Conrad anchored the pulling lines while Kerwin operated the cutter. After a few tries, Kerwin was unable to get in a stable stance to cut the strap as he used one arm to hold onto an antenna on the lab and the second one to manipulate the pole. Conrad had trouble anchoring the lines also, as the holes in the erection beam’s structure were a bit smaller than the ones used in the NBT simulations. Finally, Kerwin shortened his tether line by looping it around the antenna’s bracket, almost like what a repelling climber does on a mountain; the resulting support from a taught tether line gave him a three-point stance that freed both of his arms for use in operating the cutter. Kerwin cut the strap, but the erection beam still didn’t move. Conrad managed to wedge his body under the beam, and he pushed with all his might while Kerwin pulled on the lines as best as he could. It worked. The beam unfolded, and both men went tumbling off the surface of the OWS, with only their safety tethers and air lines keeping them from drifting away. The beam snapped into place, and the solar panels unfurled just as they were designed to.
After that, things settled down rather nicely as the mission returned to an almost-normal routine. The crew conducted their normal experiments and solar observations. Conrad and Weitz conducted one more EVA to perform a regularly scheduled changing of the ATM film. Undocking was uneventful, and a final fly-around inspection of the lab revealed that everything seemed okay for the next crew to occupy the station. The parasol had performed well and was still doing its job, so there was no need to erect the twin-pole sunshade on the first mission. It would fall to the second crew to do that. At the end of a twenty-eight-day mission, the crew of Skylab 2 returned home successfully.
20. Skylab as it appeared after deployment of the parasol and freeing of the trapped solar wing. Courtesy NASA.
21. Skylab’s second crew of Garriott, Lousma, and Bean pose next to the ATM control panel inside a training mock-up. Courtesy NASA.
The Second Crew
The second crew rocketed into orbit on 28 July 1973, a little over a month after the first crew returned to Earth. Rendezvous and docking for the second crew didn’t go quite as planned, though, as one of the CSM’s reaction control thruster quads went off-line due to a fuel leak. The craft still had three more thruster quads, so docking could still take place. But with a loss of one-fourth of the ship’s braking-thruster capability, it took a little more finesse to finish the rendezvous and docking maneuvers. Still, Alan Bean managed to execute a nearly perfect docking, and the Skylab 3 crew set up shop in the station.
A few days after docking, a second thruster on the CSM began to show signs of a fuel leak. Two sets of the CSM’s four thruster quads were enough to keep the spacecraft under control when returning home. But if a third one went out, the spacecraft would be unable to maneuver as effectively in orbit for either the undocking or the deorbit burn. So launch preparations were accelerated on the final Skylab mission’s Saturn IB booster and the rescue CSM, in case it was needed. The fuel problem eventually stabilized with only two reaction control system quads having to be isolated from the spacecraft’s fuel supply. The rescue craft was ultimately not needed.
The second crew opened up shop and began normal operations. The one major event that they had to accomplish early on was erection of the twin-pole sunshade. This was done on the first space walk. Bean’s crew had practiced the procedure in the NBT, so it pretty much went off without any major problems. Additional EVAs were carried out for normal ATM maintenance along with the placement and retrieval of some scientific experiments designed by astronaut Don Lind originally intended for the scientific airlock.
Alan Bean’s crew managed to double the endurance record set by Pete Conrad’s crew while also doubling the scientific output. Upon return to Earth, the Skylab 3 crew had spent fifty-nine days in Earth orbit. Healthwise, they seemed to be in pretty good shape thanks to the exercise regime. However, none of the crew’s bodies made any red blood cells during the flight, and this worried the doctors a little. Some extra time was spent readapting to Earth gravity after the flight, since nobody had been in space that long before. Owen Garriott also did a little extracurricular “adapting” of his own, as he made arrangements to have a milkshake delivered to him on the recovery ship to give him brief relief from the mission’s diet.
The Final Crew
The third manned crew was given a go-ahead to try to set a new three-month endurance record. But there was a minor problem with supplies. While Skylab still had plenty of oxygen and water to support a third crew, food was an issue, as the original provisions only called for a slightly larger supply of food than what the second crew had. Even with rationing, it could not be extended to over eighty days. To help with this, Skylab 4 was sent into orbit with some energy bars, similar to the type used by campers and outdoorsmen. The bars would be cycled in as part of the normal food-plan schedule, with them being eaten every third day; they were included as part of the pre-mission diet as well. The bars did the job, keeping up with the crew’s vitamin, nutrition, and calorie intake requirements, but they didn’t do much for the taste buds.
Skylab 4 launched into Earth orbit on 16 November 1973. Unlike the two previous launches, which had been under cloudy conditions, the Saturn IB carrying the Skylab 4 crew lifted off into a clear-blue Florida sky and was visible for miles. The mission was off to a great start. Docking occurred without a hitch at the end of the day, and the crew was greeted by three “occupants,” as Al Bean’s crew had played a prank on the newcomers. Before leaving, Bean’s crew had stuffed three sets of Skylab clothing with bags to make three human-shaped dummies and strapped these “crewmembers” to the station’s exercise and medical equipment. So Skylab now had six human-sized occupants. Gerald Carr’s crew took the joke in stride as they got to work.
The flight surgeons on the ground scolded the crew for one minor breach of procedure early on. One of the astronauts experienced a bout of nausea, and the other crewmembers tried to keep it hidden by flushing the vomit-filled bag down Skylab’s trash receptacle. The crew made mention of it in the tape relay instead of during an on-air transmission in the hope it wouldn’t be discovered, but it was. Normal procedure called for the bag of vomit to be returned to Earth with the rest of the bodily waste at the end of the mission.
This incident paled in comparison to what came next. Due to the combined workloads that the first and second crews were able to accomplish by the end of their missions, flight controllers and researchers packed the mission plan for the third crew with more experiments and tasks than ever before, believing that they should have no trouble getting up to speed with previous experience to draw on. But there were problems almost immediately. The crew fell behind on the time line, and attempts to catch up did not work out too well. Mission control backed off the pace somewhat, but after a few days, the problems began to crop up again. Finally, the crew said enough to the whole situation and took an unscheduled day off, followed by a slow ramping up of their experiments step-by-step.
22. Skylab’s final crew of Carr, Gibson, and Pogue pose for their portrait. The display model behind them reflects the success of the previous on-orbit repair jobs. Courtesy NASA.
While the incident did result in a few bruised egos on the ground, the lessons learned were good ones. But the press had a field day with the incident by declaring it a “mut
iny,” while mission managers downplayed the whole thing. Skylab was NASA’s first experience with long-duration space operations, and the learning went both ways with the astronauts on orbit and the flight controllers on the ground. While hardware testing tends to take priority, sometimes how man interacts with it is not as clearly understood, especially by people who have never flown in space. Ground controllers realized they should have backed off much more when problems began to crop up early on. Everybody involved was trying to get back on schedule and working too hard at it. But trying harder led to more mistakes being made. So the crew kept falling behind, until a breaking point was reached.
After the incident, the work schedule was a bit more relaxed as the astronauts did their assigned tasks at their own pace. By the end of the mission, the astronauts were getting more work done on a daily basis than the previous crews, and the third mission delivered a mountain of scientific data. The lessons learned by the end of the mission were valuable ones. Another bit of good news for the medical people was that the crew’s bodies began making fresh red blood cells in orbit. Without that, future long-duration space missions might not have been possible.