February 1, 2016: One of the most tragic events in the history of space exploration is the loss of the space shuttle Columbia and all seven of its crew on February 1, 2003—a tragedy made worse because it didn't have to happen. But just as it is human nature to look to the future and wonder what might be, so too is it in our nature to look at the past and wonder, "what if?" Today, 13 years after the event, Ars is rerunning our detailed 2014 examination of the biggest Columbia "what if" of all—what if NASA had recognized the danger? Could NASA have done something to save the crew?

If we die, we want people to accept it. We are in a risky business, and we hope that if anything happens to us, it will not delay the program. The conquest of space is worth the risk of life.

—Astronaut Gus Grissom, 1965

It is important to note at the outset that Columbia broke up during a phase of flight that, given the current design of the Orbiter, offered no possibility of crew survival.

—Columbia Accident Investigation Board Report

At 10:39 Eastern Standard Time on January 16, 2003, space shuttle Columbia lifted off from pad 39A at the Kennedy Space Center in Florida. A mere 81.7 seconds later, a chunk of insulating foam tore free from the orange external tank and smashed into the leading edge of the orbiter's left wing at a relative velocity of at least 400 miles per hour (640 kph), but Columbia continued to climb toward orbit.

The foam strike was not observed live. Only after the shuttle was orbiting Earth did NASA's launch imagery review reveal that the wing had been hit. Foam strikes during launch were not uncommon events, and shuttle program managers elected not to take on-orbit images of Columbia to visually assess any potential damage. Instead, NASA's Debris Assessment Team mathematically modeled the foam strike but could not reach any definitive conclusions about the state of the shuttle's wing. The mission continued.

In reality, the impact shattered at least one of the crucial reinforced carbon-carbon heat shield panels that lined the edge of the wing, leaving a large hole in the brittle ceramic material. Sixteen days later, as Columbia re-entered the atmosphere, superheated plasma entered the orbiter's structure through the hole in the wing and the shuttle began to disintegrate.

At Mission Control in Houston, the flight controllers monitoring Columbia's descent began to notice erratic telemetry readings coming from the shuttle, and then all voice and data contact with the orbiter was lost. Controllers continued to hope that they were merely looking at instrumentation failures, even as evidence mounted that a catastrophic event had taken place. Finally, at 9:12 Eastern Time, re-entry Flight Director LeRoy Cain gave the terrible order that had only been uttered once before, 17 years earlier when Challenger broke apart at launch: "Lock the doors."

It was an acknowledgement that the worst had happened; the mission was now in "contingency" mode. Mission Control was sealed off, and each flight controller began carefully preserving his or her console's data.

Columbia was gone, and all seven of its crew had been killed. NASA refers to this most rare and catastrophic of events as an LOCV—"Loss of Crew and Vehicle."

Frozen

Columbia is lost. There are no survivors.

—President George W. Bush in a national address, 14:04 EST, February 1, 2003

The world of human space flight paused—first to mourn, then to discover what had happened. Congress laid that responsibility on the combined shoulders of the Columbia Accident Investigation Board (referred to, in typical NASA acronym-dependent style, as "the CAIB" or just "CAIB," which rhymes with "Gabe"). In the months after Columbia, the CAIB stretched its investigative fingers all through NASA and its supporting contractors.

My own memories of the time immediately following the accident are dominated by images of somber meetings and frantic work. I was a junior system administrator at Boeing in Houston, and because we supported the shuttle program, we had to locate and send cases and cases of backup tapes—containing everything that happened on every server in our data center during the mission—over to NASA for analysis.

In August 2003, the CAIB issued its final report. Behind the direct cause of the foam strike, the report leveled damning critiques at NASA's pre- and post-launch decision-making, painting a picture of an agency dominated by milestone-obsessed middle management. That focus on narrow, group-specific work and reporting, without a complementary focus on cross-department integration and communication, contributed at least as much to the loss of the shuttle as did the foam impact. Those accusations held a faint echo of familiarity—many of them had been raised 17 years earlier by the Rogers Commission investigating Challenger's destruction.

In the end, Columbia's loss ended not only lives but also careers at all levels of NASA. A number of prominent shuttle program managers were reassigned. It is likely that Columbia's destruction factored heavily into the resignation of NASA Administrator Sean O'Keefe. Many involved with the mission—including many still working at NASA—to this day struggle with post-traumatic stress and survivor's guilt. All pending shuttle missions were put on hold, and Columbia's three surviving companion ships—Discovery, Atlantis, and Endeavour—were grounded.

NASA looked inward, and we wondered if we'd fly again.

A path not taken

To put the decisions made during the flight of STS-107 into perspective, the Board asked NASA to determine if there were options for the safe return of the STS-107 crew.

—Columbia Accident Investigation Board Report

That's the way events actually unfolded. But imagine an alternate timeline for the Columbia mission in which NASA quickly realized just how devastating the foam strike had been. Could the Columbia astronauts have been safely retrieved from orbit?

During the writing of its report, the CAIB had the same question, so it asked NASA to develop a theoretical repair and rescue plan for Columbia "based on the premise that the wing damage events during launch were recognized early during the mission." The result was an absolutely remarkable set of documents, which appear at the end of the report as Appendix D.13. They carry the low-key title "STS-107 In-Flight Options Assessment," but the scenario they outline would have pushed NASA to its absolute limits as it mounted the most dramatic space mission of all time.

NASA planners did have one fortuitous ace in the hole that made the plan possible: while Columbia's STS-107 mission was in progress, Atlantis was already undergoing preparation for flight as STS-114, scheduled for launch on March 1. As Columbia thundered into orbit, the younger shuttle was staged in Orbital Processing Facility 1 (OPF-1) at the Kennedy Space Center. Its three main engines had already been installed, but it didn't yet have a payload or remote manipulator arm in its cargo bay. Two more weeks of refurbishment and prep work remained before it would be wheeled across the space center to the enormous Vehicle Assembly Building and hoisted up for attachment to an external tank and a pair of solid rocket boosters.

So an in-orbit rescue was at least feasible—but making a shuttle ready to fly is an incredibly complicated procedure involving millions of discrete steps. In order to pull Atlantis' launch forward, mission planners had to determine which steps if any in the procedure could be safely skipped without endangering the rescue crew.

The desperate race

The scenarios were to assume that a decision to repair or rescue the Columbia crew would be made quickly, with no regard to risk.

—Columbia Accident Investigation Board Report (Appendix D.13)

But even before those decisions could be made, NASA had to make another assessment—how long did it have to mount a rescue? In tallying Columbia's supplies, NASA mission planners realized that the most pressing supply issue for the astronauts wasn't running out of something like air or water but accumulating too much of something: carbon dioxide.

Weight is a precious commodity for spacecraft. Every gram of mass that must be boosted up into orbit must be paid for with fuel, and adding fuel adds weight that must also be paid for in more fuel (this spiral of mass-begets-fuel-begets-mass is often referred to as the tyranny of the rocket equation). Rather than carrying up spare "air," spacecraft launch with a mostly fixed volume of internal air, which they recycle by adding back component gasses. The space shuttle carries supplies of liquid oxygen and liquid nitrogen, which are turned into gas and cycled into the cabin's air to maintain a 78 percent nitrogen/21 percent oxygen mixture, similar to Earth's atmosphere. The crew exhales carbon dioxide, though, and that carbon dioxide must be removed from the air.

To do this, the shuttle's air is filtered through canisters filled with lithium hydroxide (LiOH), which attaches to carbon dioxide molecules to form lithium carbonate crystals (Li₂CO₃), thus sequestering the toxic carbon dioxide. These canisters are limited-use items, each containing a certain quantity of lithium hydroxide; Columbia was equipped with 69 of them.

How long those 69 canisters would last proved difficult to estimate, though, because there isn't a lot of hard data on how much carbon dioxide the human body can tolerate in microgravity. Standard mission operation rules dictate that the mission be aborted if CO₂ levels rise above a partial pressure of 15 mmHg (about two percent of the cabin air's volume), and mission planners believed they could stretch Columbia's LiOH canister supply to cover a total of 30 days of mission time without breaking that CO₂ threshold. However, doing so would require the crew to spend 12 hours of each day doing as little as possible—sleeping, resting, and doing everything they could to keep their metabolic rates low.

If the crew couldn't sustain that low rate of activity, NASA flight surgeons believed that allowing the CO₂ content to rise to a partial pressure of 26.6 mmHg (about 3.5 percent cabin air volume) "would not produce any long-term effects on the health of the crewmembers." This would enable the crew to function on a more "normal" 16-hour/8-hour wake/sleep cycle, but at the cost of potential physiological deficits; headaches, fatigue, and other problems related to the high CO₂ levels would have started to manifest very quickly.

After the carbon dioxide scrubbers, the next most limited consumable was oxygen. Columbia's liquid oxygen supplies were used not only to replenish breathing gas for the crew but also to generate power in the shuttle's fuel cells (which combined oxygen with hydrogen to produce both energy and potable water). The amount of liquid oxygen on board could be stretched past the CO₂ scrubbers' 30-day mark by drastically cutting down Columbia's power draw.

The remaining three consumable categories consisted of food, water, and propellant. Assuming that the crew would be moving minimally, food and water could stretch well beyond the 30-day limit imposed by the LiOH canisters. To preserve propellant, the orbiter would be placed into an attitude needing minimal fuel to maintain.

Exactly when the crew of Columbia would enact these power- and oxygen-saving measures depended on a short decision tree. In the scenario we're walking through, the assumption is that NASA determined on Flight Day 2 (January 17) that the foam strike had caused some damage, followed by at least another day to gather images of Columbia using "national assets" like ground-based telescopes and other space-based sources (i.e., spy satellites) under the control of USSTRATCOM.

If that imagery positively identified damage, Columbia would immediately enter power-down mode; if the images didn't show anything conclusive, the crew would conduct an EVA (extra-vehicular activity—a spacewalk) to visually assess the damage to the wing, then power things down.

In either case, Flight Day 3 would mark the start of many sleepless nights for many people.