Space shuttle 'diary' yields spicy tidbits for NASA engineers
Space shuttle Columbia kept a "diary" during its historic flight April 12-14. And engineers now are pouring over it like they would over a good mystery. The difference is that everyone knows how the story ends: Columbia, the first reusable spacecraft, glides to a letter-perfect landing, and the United States embarks on a new era of manned space travel.
But the absence of a surprise finish has not dampened enthusiasm for the shuttle diary. It is expected to be an historic document -- a marker alongside other aviation milestone such as the invention of the airplane in 1903, the development of the first liquid-fuel rocket in 1926, and the first supersonic flight in 1947.
The data recorded on board the Columbia during the mission -- and now being studied along with debriefing information from crew members John Young and Robert Crippen -- detail how the shuttle performed during its initial test flight. And planners at the National Aeronautics and Space Administration (NASA) want to apply any lessons learned to future flight planning as soon as possible.
In a broad sense, the shuttle flight broke new ground that will provide the basis for new aviation engineering knowledge. By flying at a maximum speed of roughly four times that ever achieved previously by a winged vehicle in the atmosphere, the Columbia put to test theories about how the laws of aerodynamics operate at that velocity.
A number of new technologies were tested on the flight. But the ability to maneuver Colombia at unprecedented speeds through the reentry phase to a pinpoint landing may be the feat that has the most long-term significance, analyst agree.
Dr. Richard Hallion, aviation historian at the University of Maryland, describes the shuttle flight this way: "It does not represent a basic scientific discovery because we knew what we were up against flying at those speeds. But there was question about whether we could meet the challenge technologically, and we have proven we can."
While the spinoff value of the shuttle flight is difficult to determine, Dr. Hallion says that clearly "it is relevant to any future designs" of spacecraft that will follow the shuttle.
Further, the ability to exercise navigational and guidance control over a vehicle the size of the shuttle while traveling at speeds up to 18,500 miles per hour before reentry is bound to have benefits for conventional aircraft. Particularly impressive to engineers was the ability to maneuver the shuttle during reentry both as a space vehicle with the use of thrusters and as an airplane with the use of its wings and rudder.
"This knowledge is new and unique," says Robert Thompson, shuttle program manager at the Lyndon B. Johnson Space Center here. While the aerodynamics of air travel at conventional speeds are well understood, Mr. thompson expects information from the shuttle to be valuable over the next 50 years as commercial and military aircraft are pushed to fly at greater speeds.
One of the most valuable roles of the shuttle flight data will be as a check against the accuracy of all the Earth-based testng procedures used for the shuttle, as well as for those used for other kinds of aircraft.
"We have very sophisticated wind tunnels, but they can't come close to the reality of flying," notes Thompson. With actual performance data. NASA engineers can evaluate how good the wind tunnel and numerous other tests were in predicting the shuttle's responses in flight.
Thompson says a full assessment of the shuttle data will not be complete for two or three months. But he says a preliminary evaluation "gives us lots of confidence that the design of the shuttle is good." Overall, he says the shuttle was pushed to only 80 or 90 percent of its designs limit on the first flight.
On reentry, for example, there was considerable preflight debate among engineers about when the air around the vehicle would change from a smooth laminar flow to one of greater turbulence. The timing of this change determines the buildup of heat on the shuttle. This was a critical factor because the vehicle was protected by untested heatshielding tiles.
"It looks like the heat pulse may have been on the lower side of what we expected," reports Thompson.He credits this to good design of the shuttle in the first place so air flowed around it smoothly and did not become turbulent too early during reentry.
In one respect, the real utility of the shuttle will be tested in the next several months as NASA crews refurbish the Colombia for its next flight, now scheduled for August. The speed with which it can be made ready for flight will shed some light on how much it will cost to operate the vehicle in the years ahead. Thompson says Columbia is in such good shape that the time necessary for refurbishing "should be no restraint at all on when it flies again." Still, he does not expect the next mission until September. The extra time, he says, is needed to outfit the shuttle with some new equipment for its second test flight.