14.11.2021

April 14, 1981. The orbiter Columbia rested on a runway at Edwards Air Force Base, California, having completed the first-ever Space Shuttle mission. Now a daunting task lay ahead. Something that had never been attempted before would now have to become reality.

Columbia would have to be turned around for a second mission. No longer would a U.S. crewed spacecraft be used only once.

Ferried back across the country, Columbia arrived at the Kennedy Space Center on April 28, where teams removed her from the back of the Shuttle Carrier Aircraft, a heavily modified Boeing 747, and returned her to the Orbiter Processing Facility (OPF) for turnaround operations — much of which involved detailed inspections as well as repairs to several of her systems that were damaged during STS-1.

Most notable of these were the damage imparted to the body flap during the overpressure event at Solid Rocket Booster (SRB) ignition and the Thermal Protection System (TPS) tile damage.

After studying the SRB overpressure issue after Columbia’s first liftoff, NASA increased the sound suppression system for STS-2 to deaden the sound as much as possible given the lesson learned with STS-1 — efforts that ultimately proved successful.

For the tiles, more than 1,300 TPS tiles had to be replaced in the OFP during the turnaround flow for STS-2.

Columbia’s replaced TPS tiles ahead of STS-2. Via L2 Historical

Also changing with STS-2 was the countdown for the Space Shuttle program, which for the first mission saw auto-sequence start and handoff to Columbia’s onboard computers at the T-27 second mark, with main engine ignition at T-3.3 seconds and liftoff at T+3.3 seconds — at which point the Mission Elapsed Timer reverted to zero.

To streamline this, the countdown was adjusted so that auto-sequence start would occur at T-31 seconds, with main engine ignition at T-6.6 seconds and liftoff at T0. This sequence would remain in place until the end of the program.

Also tweaked from a ground support equipment side for STS-2 was the retraction time of the gaseous oxygen vent arm, which during STS-1 was removed during the T-9 minute hold. For STS-2 onward, the retraction sequence would initiate at T-2 minutes 55 seconds, the same time the liquid oxygen tank of the External Tank began pressurization for flight.

Aside from Columbia herself, the External Tank for STS-2 arrived at the Kennedy Space Center on April 22, 1981, where it was lifted into a check-out cell in one of the High Bays of the Vehicle Assembly Building (VAB) for post-shipment inspections and pre-mate configurations.

STS-2’s White External Tank in the VAB, via NASA

By early June, assembly of the twin Solid Rocket Boosters was complete inside the VAB, and the External Tank was mated to the SRBs on June 30.

Inside the Orbiter Processing Facility, technicians installed the Spacelab pallet with the five experiments of the OSTA-1 (Office of Space and Terrestrial Applications-1) payload into Columbia’s payload bay during June. It was also during this month that Columbia became the first orbiter to receive her Canadian-built remote manipulator system (RMS — more colloquially known as Canadarm).

The RMS was installed in Columbia on June 29.

The installation of the RMS on Columbia for STS-2, via L2 Historical

By July 29, engineers and technicians inside the OPF completed an intensive, two-day orbiter integrated test that verified that Columbia’s hardware and software were once again ready for a flight.

By this time, the launch of Columbia on STS-2 was targeted for September 30, with a planned mission duration of five days six hours. “We’re going to be ready when the bird’s ready,” said STS-2 commander Joe Engle in an August 3 pre-flight press conference.

“Our mission rules are very conservative. If we have a failure and our mission rules cause us to come home early, we will do that. I would still call it a successful flight,” he added — words that would ultimately prove prophetic.

On August 10, after 99 days in the OPF, Columbia rolled to the VAB for mating to her External Tank. Unlike the latter half of the program where the orbiters were moved on a dedicated transporter called the Orbiter Transport System (OTS), Columbia was towed to the VAB on her landing gear.

STS-2 Rollover to the VAB, via NASA

Once in the transfer aisle, Columbia was attached to the hoisting/mating sling — itself attached to two overhead cranes, and then lifted slightly off the ground at which point teams retracted her landing gear for flight.

Columbia was then raised vertically. At this point, the aft attach sling was removed before Columbia was rolled 45° and then lifted up and over the transom and into the High Bay for connection to her External Tank.

After electrical connections were made, engineers undertook a 9-day Shuttle Interface Test, which verified all of the mechanical and electrical connections between the stack as well as the functionality of Columbia’s flight systems.

Concurrently, the prime and backup crews conducted simulated countdowns and launches that used two launch profiles – the normal one that could be expected as well as Return To launch Site abort profile. Entry and landing simulations were also undertaken.

However, the effort of turning around a crewed spacecraft for the first time for a second flight in space was, as expected, causing certain events to take longer than planned. As a result, NASA managers slipped Columbia’s second launch to October 2 on August 26.

Just before 5 AM local time on August 31, technicians began rolling Columbia out to pad 39A. The entire journey took just more than seven hours to complete. At this time, a countdown demonstration test was scheduled for mid-September and the launch was once again moved to October 9.

STS-2 Columbia rolls to the launch pad, via L2 Historical

The STS-2 backup crew of Ken Mattingly and Henry Hartsfield undertook emergency egress training where they learned how to use the slide wire escape system as well as how to drive the armored personnel carrier if they would need to evacuate the launch pad.

The countdown demonstration test successfully took place on September 9 with a simulated countdown that saw the prime crew of Engle and Truly walkthrough launch day procedures with the team, including testing of their launch pressure suits as well as entry into Columbia and simulated main engine ignition.

This general practice would evolve throughout the program to become known as the terminal countdown demonstration test.

Joe Engle and Richard Truly ahead of STS-2, via NASA

Following the countdown practice with the crew, a fueling test of Columbia occurred on September 15 to continue gathering data on how the External Tank’s spray-on foam insulation reacted to the cryogenic fueling process and to test improvements to the foam following STS-1.

With a successful series of tests behind her, Columbia was looking good for a launch in mid-October… until three gallons of highly corrosive hypergolic nitrogen tetroxide oxidizer was spilled over the orbiter’s starboard side during fueling of the Forward Reaction Control System on September 22.

The oxidizer made its way between numerous TPS tiles on the forward portion of the vehicle, and subsequent inspections revealed that the nitrogen tetroxide had melted the glue that held the tiles in place, resulting in the need to re-apply roughly 370 tiles – many of which fell off on their own after their adhesive melted.

Columbia on 39A ahead of STS-2, via L2 Historical

The time-consuming nature of the work resulted in a further slip of the mission to November 4.

Countdown preparations began on October 23, with the count itself commenting on October 31 for a planned 7:30 am EST launch on November 4. Engle and Truly flew to the space center on November 2 for launch.

The count proceeded relatively smoothly, with Columbia fully fueled in the early morning hours. Engle and Truly suited up and boarded Columbia with all — expect marginal weather — looking good for liftoff.

Until the T-9 minute hold.

During this time, launch personnel noticed indications of lower than acceptable pressures within the oxygen tank of the External Tank. While working on the issue, the hold at T-9 minutes was extended even though engineers were able to quickly resolve the issue.

Countdown then resumed before halting at the T-31 second mark when the ground launch sequencer (GLS) refused to hand over control of the count to Columbia’s onboard flight computers, initiating a hold in the terminal sequence.

The issue was traced to Auxiliary Power Units (APUs) 1 and 2, which showed lube oil outlet pressures of 100 and 112 psi.

Facing uncertain technical issues as well as deteriorating weather, the launch attempt was scrubbed and the launch was reset for November 12 to allow teams time to properly understand the issues that had presented during the final moments of the count.

Unfortunately for Columbia, the fuel cell issue a T-31 seconds would be yet another prophetic moment.

On November 12, the launch was delayed two hours 40 minutes after one of Columbia’s Multiplexer-Demultiplexer units failed and a replacement was rushed across the country from Challenger, still under construction in California.

An additional 10-minute delay occurred as launch teams met to review confidence in systems status for liftoff.

On November 12 at 10:10 AM EST, coincidentally seven months to the day after she launched on STS-1 and 214 days after she returned from her first mission, Columbia took the skies over Florida once more and became the first crewed spacecraft to make a return journey to space.

Columbia reached her initial engine cutoff trajectory at T+8 minutes 33.8 seconds, with the three Space Shuttle Main Engines (engines 2007, 2006, and 2005 in the 1, 2, and 3 positions, respectively) shutting down. These engines were the same three that had powered Columbia to orbit on STS-1.

External Tank separation occurred at T+8 minutes 57.2 seconds. This was quickly followed by the 77-second OMS-1 burn at T+10 minutes 33.9 seconds.

The 69.2-second OMS-2 burn at T+41 minutes 41.7 seconds circularized and raised Columbia’s orbit into a stable configuration while the External Tank reentered the atmosphere and broke up at an altitude of 66 km at T+50 minutes 28 seconds.

However, shortly after attaining her nominal orbit of 222 x 231 km, Engle’s pre-flight words about conservative flight rules and the fuel cell omen of November 4 came to the fore.

At T+4 hours 45 minutes, Fuel Cell #1 failed. Failure of a single Fuel Cell on any Shuttle flight mandated a minimum success mission, cutting Columbia’s planned five-day flight to just two days.

Nevertheless, STS-2 was a test flight, and NASA was prepared for such an occurrence having front-loaded the majority of and the most necessary objectives and activities to the first two days of the flight already.

Despite the shortened mission, Engle and Truly completed more than 80% of the mission’s objectives, including the vital element of testing the Canadarm — which proved the arm’s operational capabilities and that its movements were not noticed by the crew nor translated through Columbia’s structure.

The OSTA-1 payload meanwhile confirmed that Earth observation sensors could be flown effectively in large groups on the Shuttle, enabling more efficient monitoring and evaluation of Earth resources.

Columbia’s STS-2 payloads, via L2 Historical

However, the fuel cell failure was not the most important issue of STS-2. Another significant In-Flight Anomaly, that would ultimately be a harbinger of the next years, was the hot gas leak path identified in a right-hand SRB field joint where a primary O-ring was found to have suffered erosion.

Notable charing and burn throughs of O-rings would be seen again on STS-8 and STS-51D, as well as other missions. The issue would culminate on January 28, 1986, when a complete burn-through of a portion of the aft field joint of the right-hand SRB caused the structural failure of the External Tank and the in-flight break up the Challenger and the loss of the seven-member STS-51L crew.

For STS-2, however, with the minimum objectives completed, Engle and Truly closed Columbia’s payload bay doors and prepared for the return to Earth.

On November 14, Columbia re-entered the atmosphere over the Pacific Ocean, heading for Edwards Air Force Base in California. While STS-1 sought to verify the Orbiter’s performance during reentry, STS-2 would be stressing the vehicles to understand its operational environment during this phase of flight.

Columbia ahead of landing, as seen from a chase plane, via L2 Historical

Columbia performed flawlessly in this regard.

For STS-2, the ground track in relation to the landing field resulted in a relatively small cross range of just 129 km, though Columbia still performed the Shuttle’s distinctive S-curve maneuvers to properly manage energy as she glided through the atmosphere for thousands of kilometers en route to the landing site.

Columbia touched down on Edwards runway 23 — a dry, lakebed runway — at 16:23:12 PM EST, completing a 1.5 million kilometer mission with a 50-second rollout covering 2.3 km.

The total mission duration for STS-2 was two days six hours 13 minutes 12 seconds, while the flight brought Columbia’s cumulative time in space to four days 12 hours 35 minutes 05 seconds.

Above all, the flight of STS-2 proved a fundamental thing about spaceflight: the ship could be reused. Gone were the days that new capsules were necessary for every spaceflight.

Mission complete. Columbia heads back to KSC for STS-3, via L2 Historical

And while true that the Shuttle program never lived up to the rapid flight expectations that were promised and expected while Columbia was on orbit on this flight 40 years ago today, it did pave the way for the technology and the drive that has led to the reusability surge in the current spaceflight era.

Quelle: NS