40 years ago NASA launched first DOD Shuttle mission
It has been 40 years since NASA launched the first dedicated Department of Defense Space Shuttle mission, after which engineers spotted O-ring seal defficiencies that would doom Challenger a year later.
The five crew members launched on the three-day jaunt to space and back – aboard Space Shuttle Discovery – on January 24, 1985. The purpose of the classified mission was to deploy a satellite to geostationary orbit using an Inertial Upper Stage (IUS).
The mission was commanded by Apollo veteran Thomas “TK” Mattingly, who had been dropped from Apollo 13 due to exposure to German measles and later flew on Apollo 16. Mattingly also flew with Henry “Hank” Hartsfield on Space Shuttle Columbia for STS-4 in 1982.
Along with Mattingly, the crew comprised pilot Loren Shriver, mission specialists James Buchli and Ellison Onizuka, and payload specialist for the US Air Force Gary Payton.
The mission was shrouded in secrecy. The actual launch time was kept secret until the T minus nine-minute mark, and public coverage of the expedition soon ceased after the successful lift-off.
However, despite the mission’s classified nature, issues spotted following the launch gave some engineers pause for thought – it could easily have mirrored the Challenger disaster a year later. Managers had delayed the lift-off due to unseasonably cold weather, although the concerns were more about ice forming on the Space Shuttle’s external tank coming loose during the ascent and potentially damaging the orbiter.
However, when the Solid Rocket Boosters (SRBs) were retrieved for inspection, refurbishment, and reuse, engineers discovered problems with O-ring seals used to prevent hot gas escaping from the SRB joints, revealing “significant erosion and ‘blow-by’ between the primary and secondary O-rings.”
The erosion was the most significant observed by the Space Shuttle program up to that point and was attributed to freezing temperatures on the pad making the O-rings brittle and more susceptible to erosion. A year later, the Space Shuttle Challenger would launch under similar conditions and be lost.
Roger Boisjoly, an engineer at Morton Thiokol, which manufactured the Space Shuttle SRBs, later told a hearing into the Challenger accident: “SRM 15 [STS 51-C] actually increased [our] concern because that was the first time we had actually penetrated a primary O-ring on a field joint with hot gas, and we had a witness of that event because the grease between the O-rings was blackened just like coal.” ®
