Despite NASA's oft-stated position that no one was overly worried about potentially catastrophic damage to the shuttle Columbia's left wing after launch, engineers and even some flight controllers continued to debate worst-case "what if" scenarios as late as the afternoon before the orbiter's destruction, according to internal emails released today.

One scenario outlined by a Johnson Space Center engineer on Jan. 31, the day before the disaster, is a virtual blueprint for what actually happened as Columbia plunged back into the atmosphere above the Pacific Ocean and streaked across the southwestern United States.

The emails also show an initial request, presumably from Wayne Hale, a veteran flight director, to have powerful Air Force telescopes or other optical assets inspect Columbia for possible signs of tile damage before re-entry was shut down by senior management.

"The SSP (space shuttle program) did not want any data and in fact there was never a formal MOD (mission operations directorate) request made from the FDOs (flight dynamics officers) or the Flight Director," wrote one flight director, Steve Stich, to another, John Shannon.

While Columbia's crew could not have been saved even if NASA managers had known the full extent of the presumed damage to the ship's left wing, a photographic survey might have provided enough data to help accident investigators reconstruct what ultimately went wrong.

But shuttle program manager Ronald Dittemore said earlier that no such request was made because even big military telescopes probably would not have been able to resolve a relatively small area of damage. And because of a Boeing analysis that concluded Columbia could safely return despite significant tile damage.

Perhaps the most intriguing email in the latest batch released by NASA is one from Kevin McCluney, an engineer at the Johnson Space Center, who outlined a disaster scenario the day before entry that is almost photo realistic in its predictions.

"Let's surmise just what sort of signature we'd see if a limited stream of hot plasma did get into the (left wing landing gear wheel) well," he wrote in an email to a team of other controllers and engineers. He assumed a hot gas intrusion in Columbia's left wing from around the moment the shuttle first hit the discernible atmosphere 400,000 feet above the Pacific Ocean until the craft fell to a point roughly 200,000 feet up. For Columbia's entry, that would mark a point above central Texas.

"First would be a temperature rise for the tires, brakes, strut actuator and the uplock actuator return," he emailed. "The pressure ... would rise given enough time, and assuming the tire(s) doesn't get holed. Then the data would start dropping out as the electrical wiring is severed, both to the transducers and the wiring to the valves, etc. ... Data loss would include that for tire pressures and temperatures, brake pressures and temperatures, prox box indications and valve indications."

Here's what actually happened:

The orbiter entered the discernible atmosphere about 400,000 feet above the Pacific at 8:44:09 a.m. on Feb. 1. This is known as "entry interface," or EI. The shuttle entered the region of peak atmospheric heating at 8:50:53 a.m.

Engineers believe a breach in Columbia's left wing, possibly caused by impact with space debris in orbit or by foam or ice from the ship's external tank that fell off and hit the wing 81 seconds after liftoff Jan. 16, allowed a jet of superheated gas eat its way inside.

Telemetry radioed back to Earth from Columbia showed a series of left wing sensor failures and rising temperatures in the left main landing gear wheel well area. Engineers believe the breach was close to the wheel well and that plasma burned through nearby sensor cabling and elevated temperatures in the well itself.

The first telemetry indicating abnormal heating timed out at 8:52:17 a.m., just one minute and 24 seconds after Columbia entered the region of peak heating. Over the next eight minutes, sensor after sensor either failed or detected higher than normal temperatures in the left wing.

Jeff Kling, the mechanical systems officer - MMACS - in mission control that day, called entry flight director Leroy Cain at 8:54:24 a.m. to report the first sensor failures.

KLING: "FLIGHT, MMACS."

CAIN: "Go ahead, MMACS."

KLING: "FYI, I've just lost four separate temperature transducers on the left side of the vehicle, hydraulic return temperatures. Two of them on system one and one in each of systems two and three."

CAIN: "Four hyd return temps?"

KLING: "To the left outboard and left inboard elevon."

CAIN: "OK, is there anything common to them? DSC (discrete signal conditioner) or MDM (multiplexer-demultiplexer) or anything? I mean, you're telling me you lost them all at exactly the same time?"

KLING: "No, not exactly. They were within probably four or five seconds of each other."

CAIN: "OK, where are those, where is that instrumentation located?"

KLING: "All four of them are located in the aft part of the left wing, right in front of the elevons, elevon actuators. And there is no commonality."

While this discussion is going on, Columbia descended across California, Arizona and New Mexico, approaching northwest Texas as it streaked toward a landing in Florida. Throughout this period, telemetry beamed back to Houston showed multiple sensor failures or signs of heating in the wheel well area. But many of these readings were not displayed in realtime on consoles in mission control.

Then, at 8:59:15 a.m. - just 17 seconds before the last voice transmission from the shuttle's commander - Kling reported additional sensor anomalies.

KLING: "FLIGHT, MMACS."

CAIN: "Go."

KLING: "We just lost tire pressure on the left outboard and left inboard, both tires."

CAIN: "Copy. Is it instrumentation, MMACS? Gotta be..."

KLING: "FLIGHT, MMACS, those are also off-scale low."

Moments later, Columbia broke apart 207,000 feet above Texas just west of the Dallas-Fort Worth area. Still not realizing what was happening to Columbia and its crew, additional sensor failures were discussed in mission control.

CAIN: "MACCS, FLIGHT."

KLING: "FLIGHT, MMACS."

CAIN: "And there's no commonality between all these tire pressure instrumentations and the hydraulic return instrumentations?"

KLING: MCC-MMACS: "No sir, there's not. We've also lost the nose gear down talkback and the right main gear down talkback."

CAIN: "Nose gear and right main gear down talkbacks?"

KLING: "Yes sir."

McCluney's eerily prescient scenario, written the day before Columbia's re-entry, is the latest in a series of internal emails charting concern about Columbia's health and what might happen as a result of presumed wing damage.

During a teleconference in the days following the disaster, Cain and senior flight director Milt Heflin said such discussions among engineers and flight controllers are normal examples of "what-ifing" that are a routine part of the engineering world.

What makes them interesting, however, is they continued in depth even after NASA's mission management team collectively dismissed concerns about post-launch tile damage following an assessment by Boeing engineers that while the wing might be damaged during entry, it would not fail. The quality and thoroughness of that analysis has since been called into question and the Columbia Accident Investigation Board has promised a re-analysis to verify or overturn those initial results.

The Boeing assessment was approved on Jan. 28. That same day, Robert Daugherty, a landing gear expert at NASA's Langley Research Center in Virginia, wrote in an email: "Any more activity today on the tile damage or are people just relegated to crossing their fingers and hoping for the best?"

While management appears to have dismissed the issue, the engineering community continued discussions showing at least some level of concern about the potential for serious tile damage.

Responding to emailed concern about possible landing gear damage and what options should be exercised to safely land the heavy shuttle, Kling said "if there was hot plasma sneaking into the wheel wells, we would see increases in our landing gear temperatures and likely our tire pressures."

"If we actually saw our instrumentation in the wheel wells disappear during entry then I suspect that the gear will not deploy anyway because the wires that control the pyros and all the hydraulic valves would burn up too.

"Ultimately, our (MMACS) recommendation in that case is going to be to set up for a bailout (assuming the wing doesn't burn off before we can get the crew out).* The rest of the cases are great big what-ifs. We can manage the drag and from early gear deploy if it happens before Mach 1. Any burn-through damage would be discovered well before that." (* Editor's note: Kling's parentheses.)

Another engineer, William Anderson, however, downplayed concerns about a breach in the landing gear wheel well. While agreeing with Kling's assessment, he said he did not believe Columbia was in any danger.

"Why are we talking about this on the day before landing, and not the day after launch?" he wrote to Kling and others. "...if there were evidence on this flight that we were missing tiles/RCC (reinforced carbon carbon panels), I might be worried."