Those changes will be included as the direct result of the Columbia Accident Investigation Board's final report, released in August, which detailed 15 recommendations NASA must do before resuming shuttle flights. Another 14 must be adopted as soon as possible.

A recent analysis showed that the changes will cost NASA an additional $280 million.

Chief among those: incorporating the ability to detect damage to the shuttle's heat protection system of tiles and reinforced carbon-carbon (RCC) material and then repair that damage while still in space.

Another major task: redesigning the shuttle's external tank so large chunks of insulating foam won't fall and threaten the shuttle's heat shield in the manner that led to the Columbia tragedy in February.

A chunk of insulating foam fell from Columbia's external tank and struck the left wing during its Jan. 16 launch, breaking open a hole that allowed hot gases to enter the wing during re-entry on Feb. 1, triggering the disaster.

And while the CAIB report cited many cultural issues within NASA management as contributing to the tragedy, it's the technical fixes that will be more quickly introduced to the shuttle program.

"The Administrator's minced no words that we will respond to and meet every recommendation of the CAIB report," Herring said. "There is some flexibility there in how you meet them, but they will be met before we fly."

Expect these changes to the shuttle system when Atlantis or Discovery flies the STS-114 mission to the International Space Station in late 2004:

Leading Edge Sensors

Although not a requirement for return to flight, officials are planning to add some two dozen sensors to the area behind the shuttle's wing leading edges.

The sensors will be able to detect the force -- no matter how small or large -- of any object striking the wing during the mission and radio that information to Mission Control as it happens.

"That will provide basically near real-time data to tell us if anything has hit the orbiter," Herring said.

If a sensor picks up a hit of some kind then mission managers will be able to tell the astronauts where to look to survey any possible damage to the RCC composite material that protects the wing and the shuttle's nose from the hottest temperatures of re-entry.

Officials hope that the sensor system can be proven reliable enough that the need to do in-space inspections with cameras and lasers won't be required some day -- saving valuable time on the flight plan and weight for other cargo.

The sensors are not new technology, and similar devices have been flown in space before, but this would be the first time the instrumentation will be used in this location.

"That's all being developed and although it's not a requirement for return to flight, we really are optimistic it's going to be there," Herring said.

Rocketcam View

Mission managers wanting to see any damage inflicted on the shuttle's heat shield during launch will be aided by a set of rocketcams that will be bolted to the external tank and pointed at key areas of the spaceplane.

"Essentially they'll be able to show us a more close up and personal view of the orbiter from the outside that we ever had before," Herring said.

Rocketcams have become increasingly popular during the past couple of years, beaming down live views of a launch from the perspective of the rocket. More common on unmanned launchers, a single rocketcam was employed during an October 2002 shuttle mission.

A rear-facing camera on the tank of a shuttle Atlantis launch provided a dramatic and unprecedented view of the 18-story vehicle climbing toward space. The only hiccup came at solid rocket booster separation when the camera lens was obscured by exhaust from the motors that push the boosters away.

Officials plan to change the rocketcam locations to avoid repeating that problem, which has serendipitously provided a better view of the shuttle, Herring said.

Space Heater

Although still a small change, the replacement of insulating foam with heaters on the shuttle's external tank will provide a visual clue to the keenest of observers that something is different.

Known as the "bipod ramp" area, the original block of hand-shaved insulating foam meant to prevent ice buildup at that location will be replaced by electric heaters. It was a chunk of foam from this ramp that triggered the Columbia tragedy.

While the hardware design is approved, engineers have yet to fully study how the fix will change the aerodynamics of the tank during launch.

Officials say they don't have any worries, but have decided to take the time and effort of building a new scale model of the shuttle for conducting wind tunnel tests early next summer.

The same effort was done during the 1970s, and although the model used then was retrieved from storage and dusted off, engineers chose to construct a new model that more faithfully represented the current configuration.

"It was proven that that approach was very successful in modeling aerodynamic flows, thermal, all of the aspects of an ascent profile," Herring said.

Once finalized and completely approved, the design will be incorporated on all future tanks. Several tanks that now are in storage in the Vehicle Assembly Building eventually will be refurbished and modified with the same fix.

Boom Town

The ability to inspect in space almost every square inch of the shuttle will be made possible with the use of a 50-foot-long extension, or boom, to the shuttle's robot arm.

"It's two segments of a robot arm that are spares that are being connected together, and then a high-tech laser sensor package and camera will be located on the end to basically allow our visual reach to become twice what it is now with the shuttle's robot arm," Herring said.

Getting the boom and laser/camera package, along with the required software, to work together as a system has been something of a challenge. But tests have progressed far enough to prove the sensor package will be able to detect damage.

Herring said this is another example of taking proven technology and finding a new use for it, rather than having to develop or invent some new gadget that could be more costly or add time to the return to flight process.

Ace Repair

How ever the discovery of damage to a shuttle's heat shield is made -- by wing sensor, rocketcam or in-flight inspection -- astronauts on all future missions will be equipped with a repair kit that will allow them to take a spacewalk and solve the problem.

Officials so far have the repair of missing or damaged heat protection tiles fairly well in hand. The process of applying the material works well and has been proven in training runs on aircraft flights that create brief moments of weightlessness.

Herring said the materials have been selected and several companies could be selected as the source -- a decision that is expected to be made in January.

Tougher still is figuring out how to repair the RCC panels that make up the wing leading edge. The composite material is handcrafted, takes months to manufacture and must be shaped for the specific area of the wing it's being used on.

Several promising options are being looked at, and the expectation is that an RCC repair kit will soon be available, Herring said.

But it's not available yet.

The total time remaining before the shuttle flies again could wind up depending on when the RCC repair kit is available.