When crew members of the space shuttle Challenger were killed in Tuesday`s sudden explosion, they were absolute hostages to their equipment, locked in the cabin with no way to escape or to safely abort the mission.
During the first 127 seconds of flight, the shuttle can detach itself from its fuel stack in case of an emergency but cannot roll into a glide that would allow it to land safely on the runway at Kennedy Space Center. The stack consists of two booster rockets with solid fuel and a huge aluminum tank containing liquid hydrogen and liquid oxygen.
The craft has the altitude and stability to maneuver back to Earth only after the booster rockets have consumed all of their fuel and are finally cut loose. For shuttle crew members, this adds up to a 127-second gamble with death that accompanies every mission.
That gamble was built into the shuttle by design, as part of the process of compromise that was needed to get the shuttle built in the first place.
At many stages of the shuttle`s development, safety considerations took a back seat to other considerations, including cost and the payload capacity of a craft that at some point was expected to pay for itself.
Given the suddenness and the extent of the explosion that ended the mission and stunned the nation, experts agreed that the Challenger crew members probably were doomed under any circumstances. Evidence uncovered Saturday suggested that no attempt was made to ditch the flight, which lasted only 74 seconds, indicating the crew had no inkling that anything was amiss.
But even a less-catastrophic failure, such as the shutdown of an engine, would have put the lives of the occupants in mortal danger if it occurred before the boosters were detached.
If the shuttle is separated from its stack during the first 127 seconds of a mission, it will plunge powerlessly toward Earth. The crew`s best chance for survival is to ditch the craft into the ocean–and NASA officials agree that this isn`t much of a chance at all.
This means certain loss of the ship even if it floats long enough for the crew members to climb out, and if they are able to do so.
”There is no cabin escape system,” said Jim Kukowski, a NASA spokesman in Houston. ”You`re trapped until the solid rocket boosters kick off. You can`t stop the solids, you can`t throttle down.”
The aluminum fuel tank is not detached from the shuttle until 1/2 minutes into a flight, but by itself it presents no impediment to a safe abort.
Solid rocket boosters are essentially giant inverted Roman candles that provide powerful ribbons of fire to drive the shuttle skyward. NASA released new photographs Saturday that apparently show an unusual plume of flame in the lower part of the right booster, which could have been the cause of the explosion.
Some built-in vulnerabilities such as that are inevitable in any spacecraft, but they may be even more so in the shuttle, which from the very first has been a compromise among competing interests and plagued by underfunding.
The decision about a decade ago to build a craft that is a hybrid between a rocket and an airplane virtually guaranteed that there would be this period at the outset of a flight when occupants must trust their fate to the performance of their ship`s many complex systems.
When a reusable space vehicle was first proposed, one suggestion was for a self-contained rocket ship with an internal fuel supply that could take off and land like an airplane. Such a craft–if it could have been developed
–should have been less unwieldy and safer than the existing shuttle. But this idea was dismissed as being far too expensive.
What finally was built was a shuttle with three external fuel components attached to the spaceship–the two boosters filled with solid fuel and the huge aluminum tank that carries liquid hydrogen and liquid oxygen, two of the most volatile subtances known to man.
The shuttle`s initial test flight illustrates the compromises NASA has had to make to get the program off the ground.
In an interview on the eve of the shuttle Columbia`s first launch in 1981, Max Faget, director of engineering and development at NASA`s Johnson Space Center in Houston, acknowledged that a shortage of money had forced some safety shortcuts.
John Young and Robert Crippen were to fly the Columbia`s maiden voyage, the first time an American spacecraft wouldn`t be tested in unmanned flights before taking humans into space.
”It`s obviously more hazardous for the crew,” Faget said. ”There`s no hazard at all if the crew stays on the ground, but there is another consideration. The safety of the vehicle. Being very cold-blooded about it, the orbiter costs in the neighborhood of $1 billion, a big chunk of money.
”So one can say one is willing to risk, to put the crew to a certain amount of hazard, to protect our investment in that vehicle.”
One member of the original committee that designed the shuttle, Hans Mark, a former NASA deputy administrator and now the chancellor of the University of Texas system, said Friday that he doubts any design flaws played a role in the Challenger explosion.
”Those people never had a chance,” Mark said. ”I don`t think this is a design problem. It can happen because there is a flaw, a leak . . . God knows. The design is sound. I think something wasn`t put together right or tightened down or some electrical system malfunctioned.”
Mark acknowledged that funding shortages did have an effect on the shuttle`s design.
”Obviously if you spend more money, you can always make things better,” he said. ”Within the alloted funds we had, it is the best spaceship we could make. It is the best in the world.”
Some safety items, such as escape rockets for occupants of the shuttle to use in case of trouble during liftoff, were scrapped for financial reasons and to save on weight when the craft was designed.
The capacity of 65,000 pounds designed for the shuttle also was a compromise. Several engineers favored a smaller, reusable craft, one that could carry about 50,000 pounds into space and take off and land from regular airports.
Capacity was increased and has been boosted since the first Columbia flight at the insistence of the military, which wants to put bigger payloads into space. It was only after Air Force officials persuaded Congress and former President Jimmy Carter to beef up NASA`s shuttle budget because of military aspects that the agency got enough money to complete the craft`s development.
”Every program contains certain tradeoffs,” said James Mizell, a NASA spokesman and former launch operations engineer. ”Just like when we traded off with the Air Force on destruct system versus no destruct system on the orbiter. They were willing to trade off.”
In that trade, it was agreed that the booster rockets and external fuel tank would be equipped with explosives that could be detonated by ground control in the event that they threatened to crash into a populated area. Because crewmen are locked into the shuttle, it was designed so that the commander could ditch the craft by ejecting from the boosters at any time.
”Ditching . . . is not practiced,” Mizell said. ”It`s not in the rulebook. Astronauts don`t talk about it much, but that`s where you break loose from the stack (of boosters and fuel tank) as fast as you can and try to land, regardless of your speed or anything else.
”Basically, what you`re trying to do is get away from the stack.”
In a ditching situation, the shuttle commander knows that his stack is out of control and will soon explode itself or be detonated by ground control, Mizell said. Flying the shuttle under those conditions is extremely difficult. ”It doesn`t fly very well,” Mizell said. ”It flies like a rock. But nevertheless, he could have flown to a water landing or possibly a beach landing . . . even if he dropped almost straight down and just flared at the last minute.”
