Consequently, independent aerospace experts -- who expect the shuttle fleet to fly at least another 20 years -- are urging NASA to develop an advanced crew escape system that will safeguard astronauts in a wider range of deadly launch failure scenarios.

"The time is past due for the implementation of a more capable crew escape system," the Aerospace Safety Advisory Panel said in an annual report released earlier this year.

Chartered by Congress after the 1967 Apollo 1 launch pad fire, the watchdog group said such a system "will provide the largest potential improvement in crew safety" during what is expected to be two more decades of shuttle fleet operations.

Senior shuttle program officials, meanwhile, fully recognize the inadequacy of the current system and are in the midst of reviewing alternatives.

The bailout pole "would not be effective under all failure scenarios -- not even most failure scenarios," NASA shuttle program development manager Elric McHenry told SPACE.com.

"So we have been seriously looking into what it would take to improve our ability to get the crew out in case we had another catastrophic situation."

Added to NASAs $8 billion fleet after the 1986 Challenger disaster, the current system hinges on a shuttle commanders ability to gain full control of the ship in the event of an engine failure, a loss of cabin pressure or any other major malfunction in flight.

Heres how the situation would unfold inside the ship:

First, an astronaut on the shuttles mid deck would open a crew cabin vent once the orbiter was flying stably at 40,000 feet (12,133 meters), a move meant to equalize internal air pressure with the atmosphere outside the ship.

With both the shuttle's boosters and external fuel tank jettisoned, a commander then would slow the ship to 225 miles (360 kilometers) per hour before putting the orbiter on autopilot.

The skipper and other astronauts on the ships flight deck then would climb down a ladder to the shuttle's mid deck. There, the shuttle's side hatch -- which is equipped with explosive bolts -- would be blown away from the ship, opening up an escape route for the astronauts.

Next, an 8.75-foot (2.65-meter) telescoping pole -- which normally is mounted on the mid-deck ceiling -- would be extended through the open hatch. And then, one by one, the astronauts would hook a parachute harness to the 248-pound (546-kilogram) pole and jump out of the ship and toward the ocean.

The escape pole plays a critical role: Without it, an astronaut would slam into the shuttle's left wing or hump-like pods that house orbital maneuvering engines on the tail end of the ship

Theoretically, the bailout would begin at an altitude of about 20,000 feet (6,607 meters) so that all of the astronauts would be out of the ship in time for their parachutes to open up for an ocean splashdown.

Assuming the astronauts all got out of the ship, they likely would hit the water about a mile (1.6 kilometers) apart from each other, bobbing along a line that followed the shuttles flight path.

The $2 billion spaceship, meanwhile, almost certainly would be destroyed, crashing into the Atlantic at a speed in excess of 200 miles (320 kilometers) per hour. At the same time, helicopters carrying specially trained Air Force troops would fly out to sea on a search-and-rescue mission.

As for the astronauts, their survival at that point largely would depend on partial pressure suits routinely worn during launch and landing.