|Just seconds before chaos ensues, Skylab's Saturn V climbs into the skies on May 14th, 1973. NASA photo.|
Myth #1: Mach 1, Not Max-Q
Shortly after these indicators flagged possible issues with the Skylab cluster, hell really broke loose. The mission reports bluntly indicated, “At about 63 seconds, numerous measurements indicated the apparent early deployment and loss of the MS. At this time, the vehicle was at about 28,600 feet altitude and at a velocity of about Mach 1 [emphasis provided by me].” But why did this happen, and what caused these cascading failures?
The book Growing Up With Spaceflight: Project Skylab/ASTP by author Wes Oleszewski also discussed Skylab’s early troubles at length. Oleszewski wrote:
At 62.807 seconds after liftoff, the launch vehicle began to react to an external, abnormal aerodynamic force… Max-Q was a full 10.63 seconds [after Mach 1] into the future and the meteoroid shield would be long gone by then. What really happened was that as the Mach 1 shock wave passed down the vehicle a reverse flow of air along the skin of the vehicle found its way up what was called the Auxiliary Tunnel (a conduit that ran the length of the workshop). Entering through two uncapped stringers at the base of the tunnel, the high pressure air moved up the tunnel and popped the rubber boot at the top. The airflow then got up under the shield structure and propagated a bulge that was just enough to lift the shield more than 2 inches into the slipstream, which was now at Mach 1.05.This aerodynamic excursion Oleszewski described is what took out the MS, and subsequently loosened both solar panels.
So what caused SAS-2 to shear off completely, and SAS-1 to be partially stuck, trickling electricity and resulting in a risky EVA by Skylab 2 commander Pete Conrad and science pilot Dr. Joe Kerwin? Remember, the MS detachment loosened the solar wings. Oleszewski wrote of SAS-2’s death knell:
At S-II shutdown...four solid fuel retro rockets mounted at 90 degree intervals around the S-IVB / S-II forward adapter skirt fired to aid in separation of the S-II from the upper stage. SAS wing number 2 was centered just 16.8 degrees off one of the retro rockets. The plume from that retro’s firing hit the already loose SAS wing and blew it “...completely off the bird” as Pete Conrad later observed.According to Oleszewski, SAS-1 remained attached to Skylab during this phase of the mission only because it was held down by the MS’ debris.
2. Steven-Boniecki, D. (Ed.). (2015). Skylab 1 & 2: The NASA Mission Reports. Burlington, Ontario: Apogee Books.
3. Ward, J. (2015). Countdown to a Moon Launch: Preparing Apollo for Its Historic Journey. Chichester, UK: Springer/Praxis.