The retirement of the space shuttle may turn out to be a larger turning point in the history of human spaceflight than appears on the surface. The problem is not that the shuttle was so bad, but rather that it was so good.
When the shuttle first flew in 1982, it was a technological marvel, the most sophisticated and capable launch vehicle ever built. It overcame much of the waste of conventional, expendable rockets, which shed their lower stages as they ascended through the atmosphere. The shuttle’s orbiter could return to Earth, land like an airplane and fly again.
It also had an innovative heat shield; the most powerful and efficient engine ever built; a network of integrated computers capable of flying the shuttle from liftoff to touchdown; and the ability to deliver, retrieve and maintain the component parts of a space station.
But the shuttle failed to provide safe, reliable, economical access to low-earth orbit. If this technological tour de force could not open up the potential of space, you have to wonder what can?
The shuttle is still the envy of space-faring nations around the world. But as former NASA administrator Michael Griffin has observed, the shuttle was also “an inherently flawed vehicle.” Its design was constrained by budget limitations and by Air Force insistence that it accommodate the largest of spy satellites and the mission profiles to support them. It was only partially reusable, jettisoning its main fuel tank and rocket boosters on its way to orbit. The wear and tear of flying in and out of the atmosphere drove refurbishing costs to budget-busting levels.
Far from reducing launch costs by an order of magnitude, as it was designed to do, the shuttle actually cost more to fly than the Saturn launch vehicle it replaced. On average, each of shuttle’s 135 flights cost the taxpayer $1.5 billion.
Cost remains the bane of chemical-fueled launch vehicles. The Russians probably have the best record, using “big dumb boosters” of simple but reliable design; their real costs for human launches, however, appear not to have achieved NASA’s criterion of reducing launch costs by 90 percent.
Two physical realities constrain progress on this front. First, manned spacecraft are heavy. Humans venturing into space must take food, water, other consumables, life-support equipment, medical and safety equipment, and fuel and hardware to return them to Earth. Also, any launch vehicle carrying people into space has to be subjected to quality controls far higher than those imposed on unmanned spacecraft, further driving up costs.
The second constraint is the fuel ratio. When the shuttle lifts off the launch pad, 94 percent of its weight is fuel, tankage and solid-fueled rocket boosters. Another 5 percent is the empty shuttle orbiter. Only 1 percent is payload. This is the Achilles heel of all chemical-fueled launch vehicles. Instead of costing $600 (in 2010 dollars) to put a pound of payload in orbit, as NASA promised in 1971, the shuttle cost is $30,000 a pound.
After more than 50 years of manned spaceflight, with no significant initiatives on the horizon, a new paradigm appears to be in order.
One commercial company flies its prototype manned spacecraft aloft before igniting its rockets at high altitude. Other alternatives abound, ranging from slingshots and ski jumps to space elevators.
The shuttle, said Griffin, was a “mistake.” If NASA is to learn from that mistake, it will need to do some real, original, daring research and planning, not just recycle the chemical-fueled rockets of the last 60 years.
Alex Roland is a professor of history emeritus at Duke University and a former NASA historian.
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