"Crew escape capability is there for the eventuality that if you have a catastrophic situation, youd like to be able to get the crew out (of the shuttle) and give them as much chance of survival as you can," NASA shuttle program development manager Elric McHenry told SPACE.com.
"Whats much more important is to prevent that from happening."
A more robust booster rocket system could do just that.
NASA shuttles now rely on twin solid rocket boosters and three liquid-fueled main engines to provide the propulsive power needed to make a thundering climb into orbit.
But an engine shutdown, a loss of cabin pressure or any of a myriad of other potential systems failures could send a shuttle crew toward a risky and unprecedented emergency landing in Florida, Spain, North Africa or a host of other sites around the globe.
An advanced booster system, however, could provide enough extra power to rocket into orbit even if a major failure cropped up during an eight-and-a-half-minute launch toward space.
"We think that strategically, an additional capability in the boosters would allow us to avoid some (in-flight) abort modes," McHenry said.
"That would allow us to go to orbit when a main engine fails rather than having to turn around and fly back to (Kennedy Space Center) or even go across the Atlantic Ocean and land in Africa or Spain."
The chances of an emergency landing during any shuttle launch are great enough that NASA and the U.S. Department of Defense routinely have recovery crews on hand at Kennedy Space Center and at least three sites in Spain and North Africa.
A half dozen air bases along the U.S. eastern seaboard also are staffed with emergency landing crews during all shuttle launches.
A so-called Transatlantic Abort would call for an astronaut crew to fly to an altitude of 70,000 feet (21,233 meters) before jettisoning the shuttles 15-story external tank and heading for a runway in Spain or North Africa.
Much more difficult would be a so-called "Return To Launch Site" abort: An emergency landing back at Kennedy Space Center.
The so-called RTLS scenario would call for a mission commander to carry out a Mach 7 U-turn and a tricky pitch-up maneuver to avoid slamming into the external tank as it dropped away from the orbiter.
Former astronaut Curt Brown, a six-time shuttle flier, expressed his own reservations about pulling off such a landing during a 1999 interview with SPACE.com.
Brown said he was confident a crew could survive an emergency return to NASAs coastal Florida spaceport, but he said a $2 billion spaceship might be irreparably damaged in doing so.
"The orbiter may be hurt a little bit," said Brown, a former military test. "It may not be able to be reused for a few months, weeks or years. It may not be reusable at all. But I think well get back to the runway."
NASA now is studying three advanced rocket booster systems that could significantly reduce the possibility of an emergency-landing attempt. They include:
- A five-segment solid rocket booster.
Shuttle boosters now are outfitted with four fueled segments. Adding a fifth would provide the extra power needed to fly into orbit even after a major systems failure.
- An expendable liquid-fueled booster system.
Unlike solid-fueled rockets, which fire until all propellant is exhausted, liquid-fueled boosters can be automatically turned off in flight if computers detect a potentially explosive problem.
That safety feature would give crews a better chance of surviving a booster system failure, although an expendable rocket could not be recovered and refurbished for reuse.
The liquid boosters being studied by NASA, meanwhile, would provide enough power to fly into orbit if a main engine or other critical system failed during the ride toward orbit.
- A so-called "Liquid Fly-Back Booster."
Considered the most sophisticated of the alternative systems, this liquid-fueled booster would be capable of flying back and landing on NASAs shuttle runway here at Kennedy Space Center. The rockets then would be rolled into a nearby hangar where they could be refurbished and readied for another flight in about a week.
Such a system also could serve as the first stage of the type of heavy-lift launch vehicle that would be needed to send human expeditions to Mars.
Like a new crew-escape system, none of the advanced rocket booster systems would be cheap to design and develop. Either of the first two options would cost about $1 billion, and a Liquid Fly-Back Booster system could cost as much as $5 billion.
But any of them would go a long way toward eliminating the type of risky emergency landing scenarios that worry program managers during any shuttle launch.
"Id like the capability to go all the way to orbit," shuttle program manager Ron Dittemore told SPACE.com.
"Now that offers some distinct advantages. I dont have the risk of an RTLS. I dont have the risk associated with landing in Spain or Africa. And then once I get in orbit, I have time to talk about my situation and have a more controlled response and landing back at the Kennedy Space Center or alternate sites."
Such a system is something that NASA long has considered too expensive to pursue in light of an advertised 2012 retirement date for the shuttle fleet.
But with no heir apparent waiting in the wings, it is increasingly likely that NASAs four winged spaceships will be flying for another 20 years. And if thats the case, program officials believe a new booster rocket system could be the wisest safety improvement the agency could make.
"Its not the kind of thing we can do for a short term, but if the vehicles were going to fly until 2020 or 2030, that would be a significant consideration," McHenry said.
"If I had to decide by knowing what I know today, I would invest heavily in propulsion improvements," Dittemore added.
"Not only do you get the larger performance capability to avoid (emergency landing attempts), but you would invest in greater reliability of the machinery itself so you never have a chance to get into that contingency situation," he said.
"So thats where I would do my investing right now, and then (at the same time), I would be looking at the ways that I can improve my crew escape, and then Id buy that by the yard and see how much I could get."
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