The shuttle's external fuel tank foam and work to minimize debris shedding has been the central focus of NASA's post-Columbia safety upgrades. But a variety of other improvements have been made, including development of new main engine computer technology designed to detect potentially catastrophic vibrations before they develop into "major malfunctions."

The new Advanced Health Management System, or AHMS, flew on one engine in monitor-only mode during the most recent shuttle flight in December. For Atlantis' flight, AHMS will be fully active on one engine, able to automatically shut down the powerplant if problems develop. NASA plans to use AHMS on all three engines starting with the next shuttle flight in August.

Each of the shuttle's three hydrogen-fueled main engines is equipped with a controller that monitors engine performance 50 times per second. The new system, the sixth upgrade for engine controllers since shuttle flights began in 1981, uses new digital signal processors to monitor vibration levels in an engine's high pressure hydrogen and oxygen turbopumps.

Roughly the size of a beer keg, a main engine high pressure hydrogen pump operates at 34,000 rpm while the oxygen pump turns at 23,000 rpm. The new system analyzes data from accelerometers 20 times per second to detect vibrations "indicative of impending failure of rotating turbopump components such as blades, impellers, inducers and bearings," NASA said in a news release.

"If the magnitude of any vibration anomaly exceeds safe limits, the upgraded main engine controller would shut down the unhealthy engine immediately."

Depending on when a main engine shut down, a shuttle crew could be forced to make a risky return to Florida, an emergency landing in Europe or limp into a lower-than-planned orbit. But any of those options would be preferable to a catastrophic turbopump failure.

"The space shuttle main engine project has, for many years, pursued a reliable means to monitor high-pressure turbomachinery health in real time," Tim Kelley, deputy manager of the main engine project, said in a release. "AHMS provides that capability and significantly improves shuttle flight safety."

Not counting pad aborts and the Challenger disaster, which was triggered by a solid-fuel booster failure, only one shuttle main engine has ever shut down prematurely, triggering a dramatic abort to a lower-than-planned orbit in July 1985.

Like all shuttle pilots, Sturckow and Archambault are trained to handle a wide variety of possible aborts they hope will never happen.

DATE/EDT.......DD...HH...MM...EVENT

06/08/07
Fri 07:38 PM...00...00...00...STS-117 launch
Fri 08:16 PM...00...00...38...OMS-2 rocket firing
Fri 08:28 PM...00...00...50...Post-insertion timeline begins
Fri 10:08 PM...00...02...30...Portable computer, TV setup
Fri 10:18 PM...00...02...40...Robot arm (RMS) powerup
Fri 10:33 PM...00...02...55...RMS checkout
Fri 11:08 PM...00...03...30...SEE (emergency eyewash) setup
Fri 11:18 PM...00...03...40...RMS payload bay survey
Fri 11:38 PM...00...04...00...RMS powerdown
Fri 11:38 PM...00...04...00...External tank umbilical camera downlink
Fri 11:38 PM...00...04...00...Group B computer powerdown
Fri 11:58 PM...00...04...20...Wing leading edge sensor system setup
Fri 11:58 PM...00...04...20...ET handheld video downlink

06/09/07
Sat 12:23 AM...00...04...45...Thermal protection system imagery downlink
Sat 01:38 AM...00...06...00...Crew sleep begins

Data collected by the wing leading edge impact sensors also will be downlinked to Houston for detailed analysis. Located on each wing's forward spar behind every reinforced carbon carbon panel, the 132 accelerometers will provide data indicating whether anything struck the leading edges during launch.

On the second day of the mission, the astronauts will use Atlantis' robot arm and the 50-foot orbiter boom sensor system - OBSS - extension in a tedious but now routine inspection of the wing leading edge panels and the shuttle's reinforced carbon carbon nose cap.

A laser sensor on the end of the boom is capable of spotting any wing leading edge damage that could pose a threat to the shuttle. The astronauts will start with the starboard, or right-side, wing leading edge, making multiple passes up and down the wing to cover all the angles. After scanning the nose cap, they will move on to the port wing and repeat the procedure.

DATE/EDT.......DD...HH...MM...EVENT

06/09/07
Sat 09:38 AM...00...14...00...Crew wakeup
Sat 11:00 AM...00...15...22...NC-2 rendezvous rocket firing
Sat 11:38 AM...00...16...00...Portable computer setup (part 2)
Sat 12:38 PM...00...17...00...Spacesuit checkout preps
Sat 12:48 PM...00...17...10...RMS powerup
Sat 01:03 PM...00...17...25...OBSS unberth
Sat 01:08 PM...00...17...30...Spacesuit checkout
Sat 02:03 PM...00...18...25...OBSS surveys starboard wing
Sat 02:53 PM...00...19...15...Spacesuit transfer preps
Sat 03:33 PM...00...19...55...OBSS surveys nose cap
Sat 04:23 PM...00...20...45...Crew meals begin
Sat 05:23 PM...00...21...45...OBSS surveys port wing
Sat 06:53 PM...00...23...15...OBSS berthing
Sat 07:08 PM...00...23...30...Centerline docking camera installation
Sat 07:38 PM...01...00...00...Fuel cell monitoring system operations
Sat 07:38 PM...01...00...00...Orbiter docking system ring extension
Sat 08:03 PM...01...00...25...Ergometer setup
Sat 08:08 PM...01...00...30...Wing leading edge impact sensor downlink
Sat 08:18 PM...01...00...40...Rendezvous tools checkout
Sat 09:11 PM...01...01...33...NC-3 rendezvous rocket firing
Sat 09:18 PM...01...01...40...OBSS laser downlink
Sat 09:48 PM...01...02...10...Astronauts survey tiles on the shuttles OMS pods

06/10/07
Sun 01:08 AM...01...05...30...Crew sleep begins

The astronauts will need 75 to 90 minutes to complete the starboard leading edge scan, 50 minutes for the nosecap and another 90 minutes for the left wing. The new scanning procedure covers most of the crew cabin as well, eliminating the need for separate photo scans of the cabin. All in all, the flight day two thermal protection system inspections will only take about four hours instead of six.

One of the most effective ways to look for signs of damage occurs during final approach to the space station on flight day three. Sturckow will fly a standard rendezvous profile, approaching the lab complex from behind and below. The terminal phase of the rendezvous procedure begins about three hours before docking with the shuttle trailing the station by about 9.2 miles.

DATE/EDT.......DD...HH...MM...EVENT

06/10/07
Sun 09:08 AM...01...13...30...STS/ISS crew wakeup
Sun 10:28 AM...01...14...50...Group B computer powerup
Sun 10:43 AM...01...15...05...Rendezvous timeline begins
Sun 11:26 AM...01...15...48...NC-4 rendezvous rocket firing
Sun 12:33 PM...01...16...55...Middeck prepped for docking
Sun 12:48 PM...01...17...10...Spacesuit removal
Sun 12:59 PM...01...17...21...TI burn
Sun 02:03 PM...01...18...25...Orbit 29 sunrise (approximate)
Sun 02:18 PM...01...18...40...Approach timeline begins
Sun 02:38 PM...01...19...00...Rendezvous pitch maneuver
Sun 03:08 PM...01...19...30...Orbit 30 sunset (approximate)
Sun 03:33 PM...01...19...55...Orbit 30 sunrise (approximate)
Sun 03:38 PM...01...20...00...DOCKING
Sun 03:58 PM...01...20...20...Hard mate
Sun 03:58 PM...01...20...20...Leak checks; portable computer reconfig
Sun 04:28 PM...01...20...50...Group B computer powerdown
Sun 04:28 PM...01...20...50...Docking system prepped for entry
Sun 04:58 PM...01...21...20...Hatches open
Sun 05:13 PM...01...21...35...SRMS grapples S3/S4
Sun 05:28 PM...01...21...50...Welcome ceremony
Sun 05:33 PM...01...21...55...Safety briefing
Sun 05:58 PM...01...22...20...S3/S4 unberthing
Sun 06:18 PM...01...22...40...Anderson seat liner transfer
Sun 06:58 PM...01...23...20...REBA checkout
Sun 07:18 PM...01...23...40...S3/S4 handoff
Sun 07:23 PM...01...23...45...Equipment lock preps
Sun 08:38 PM...02...01...00...SRMS ungrapples S3/S4
Sun 08:58 PM...02...01...20...SRMS positioned for S3/S4 attach viewing
Sun 09:13 PM...02...01...35...EVA-1: Procedures review
Sun 11:23 PM...02...03...45...EVA-1: EV1/EV2 mask pre-breathe

06/11/07
Mon 12:18 AM...02...04...40...EVA-1: Crew lock depress to 10.2 psi
Mon 01:08 AM...02...05...30...STS crew sleep begins

"We'll basically fly up the R-bar and then we will look to stop our approach around 600 feet, and we'll do a full 360-degree pivot while the station crew takes photographs of the underside of the space shuttle Atlantis," Sturckow said in a NASA interview. "The job for us is to set the shuttle up so it's in a good position when we initiate that maneuver, and then we turn the flight controller power off and perform the pivot."

Kotov will snap 800-mm photos, Yurchikhin will handle the 400-mm lens and Williams will operate a video camera. The pictures and video will be downlinked later that day.

Good imagery, radar and impact sensor data are just part of NASA's post-Columbia approach to ascent damage to the shuttle from external tank foam or any other source. The other two components are the crew's ability to repair minor damage and, in a worst-case scenario, the capability of the space station to support a combined crew of 10 until a rescue flight could be mounted.

It would not be easy. The Russian Elektron oxygen generator has a history of malfunctions, there is only one toilet on board and supplies would be tight. Worse, the only way down in a major emergency would be a single three-seat Soyuz capsule.

But NASA and the Russians have pre-positioned additional supplies for just such a contingency, including food, water and lithium hydroxide to scrub carbon dioxide from the air. Going into the STS-117 launch campaign, the station has enough supplies and oxygen generation capability to support the combined 10-member crew for at least 68 days. NASA engineers say the shuttle Discovery could be ready for launch on a rescue flight in just 50 days, by July 28.

NASA managers are increasingly optimistic they will never have to invoke the "safe haven" option. Along with removing all large concentrations of foam on the external fuel tank, engineers have been working on techniques for repairing damage to a shuttle's heat shield tiles and even the critical wing leading edge panels.

Tests carried out during previous post-Columbia spacewalks show small cracks in the reinforced carbon carbon material are repairable with a material known as NOAX. Two repaired cracks subjected to arc jet tests showed the material held up well under actual re-entry level temperatures.

The repair techniques are not officially "certified" for use. But Reilly, who helped develop the procedures, says they would probably get a crippled shuttle safely back to Earth.

"When we first got that task and we were assigned to those jobs, I know for me personally I thought this was almost an insurmountable technical problem," he said. "But of course, we've got a lot of incredibly intelligent folks here working with us and we've got what now look to be some pretty good solutions that are well on their way to getting certified as a repair technique that will survive the re-entry environment. And as you know, the re-entry environment is a pretty dynamic place to be and one of the things that was a surprise to me was really how narrow the margins were on everything we do. So that made it really difficult for the guys working on the materials to come up with the solutions.

"But ... we have a lot of people looking at different options when we first got started on the problem and then took the most suitable options and carried them forward. And Danny and I have both been lucky enough to be involved in the testing and development, both of the materials as well as the techniques, the application techniques and how we would actually effect these repairs. So for either one of us, I would feel pretty confident ... that we would be able to bring it home safely."

Olivas agreed, saying "I would second that. I had the luck and good fortune to work alongside several, many of the engineers back right after Columbia happened when we first started looking at repair options for both tile and RCC repair. I happened to work with the folks working RCC repair and I'm here to tell you, I've got every bit of confidence in what they've done and the hardware they've produced."

One other event on flight day three is worthy of note: Anderson's custom Soyuz seat liner will be moved into the lab complex and his Sokol pressure suit will be tested. Once the seat liner is in place on the station, Anderson will be a member of the Expedition 15 crew, sleeping aboard the laboratory, while Williams will join the shuttle crew and sleeps aboard Atlantis.

Continue to Part 5 -->