CAPE CANAVERAL, Fla. (AP) --
Next time you grumble about your late airline flight, consider the space
shuttle: It launches on time 40 percent of the time.
Not so great when stacked
against the airline industry, which had a 73 percent on-time arrival record for
the first six months of this year.
But let's be fair. The
shuttle is the world's most complicated aeronautical machine, so 40 percent may
not be so bad.
The latest delayed shuttle flight is this
week's mission. Endeavour, originally set for a Tuesday launch, is now
scheduled to lift off on Wednesday.
A database analysis by The
Associated Press showed that 47 of the 118 previous space shuttle missions
have taken off on their originally scheduled day. Technical glitches account
for more than half the delays. (Endeavour was held back because of a leaky
valve in the crew cabin.)
Bad weather at Kennedy
Space Center is to blame for about a third.
"To me as a
statistician, a 40 percent success rate for the space shuttle sounds pretty
good,'' said Michael Orkin, author of "What are the Odds? Chance in
Everyday Life." He is also business, math and sciences dean at Laney
College in Oakland, Calif.
NASA launch director
Michael Leinbach said that since the 2003 Columbia accident that
killed seven astronauts, "we have more rules to pay attention to.''
Since NASA's post-Columbia return to flight in 2005, NASA
has had 10 launch delays and only five liftoffs, a 33 percent success rate. In
its most successful years, 1997 and 1998, NASA launched 13 times with only
three delays, an 81 percent on-time rate.
The good news for NASA is
that over time, technical delays are becoming far less frequent as engineers
better understand the complicated vehicle, said Paul Fischbeck of Carnegie
Mellon University. The engineering professor analyzed the database of delays.
From 1981-85, 73 percent of
all delays were technical glitches, but that was down to just 38 percent from
2000-06, he found.
The bad news: Weather
delays are soaring. The reason is probably because the shuttle's only mission
these days is to go to the International Space Station. Because of the orbital
mechanics required to hook up with the orbiting outpost, that means NASA has
only five minutes at set times of day to launch.
In years past, delays have
been caused by five hurricanes, a tropical storm, woodpeckers that hammered
away at the fuel tank, and two hailstorms. Strangely, there have been more
weather delays in winter than during summer storm season. Launches in December
and January had weather delays two-thirds of the time, compared to 40 percent
of the time from June through September.
And there have been a
multitude of technical problems, from main engine difficulties to fueling
troubles to wiring kinks.
"If you look at all of
the things that have to work in order to launch, including the weather ... you
would conclude it's crazy to even try,'' former astronaut Steve Hawley said
recently.
Hawley should know. His
five flights experienced 13 delays.
And despite logic, NASA's
luck with second, third and fourth tries isn't much better. Fischbeck found
second tries only succeed about half the time.
"A lot of it is just
random,'' said Fischbeck, who has consulted for NASA.
More than a quarter of
shuttle delays have occurred within the three-day launch countdown period,
often with astronauts strapped into their shuttle seats. But some hint a
postponement isn't all that bad.
"Those last couple of
months are very, very intensive, very busy,'' said Dominic Gorie, a veteran of
three flights. "So when you get a launch delay in the last week, the crew
really gets an opportunity to relax.''
Endeavour's commander,
Scott Kelly, says astronauts take it in stride. "You can't get frustrated
over something you have no control over.''
In 2010, the space shuttles
will be retired. One of NASA's priorities for its new
Orion spaceship, which is being built for moon flights, is to make its
launches more timely. NASA exploration chief Scott Horowitz says the design of
the new ship may improve its on-time rate to almost 100 percent.
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