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Nov.
15, 2007: How do you bring a 200,000-pound rocket
booster back to Earth after it catapults its payload toward
the moon? Very carefully!
It's
something NASA has to learn to do. The agency is laying plans
to return to the moon in the next decade, and designs for
the new Ares moon rocket call for reusable boosters. These
massive side-rockets can't just crash back into the ocean
when they're out of fuel -- they've got to be lowered gently.
Today
NASA took an important step toward accomplishing this spectacular
feat when engineers successfully tested the colossal parachute
designed to bring the Ares I Crew Launch Vehicle's first stage
booster back down.1 The
150-foot diameter ribbon parachute passed with "flying
colors." Sporting broad, bright stripes of red and blue,
the parachute drifted to Earth from 16,500 feet above and
gently (relatively speaking) placed its huge passenger on
the Yuma, Arizona ground:
Above:
The Ares parachute in action. More images: #1,
#2.
"Everything
had to happen exactly according to plan for us to get a 42,000-pound
weighted tub out the back of a C-17 airplane and time the
free fall just right," says James Burnum of NASA's Marshall
Space Flight Center. "We had to deploy our parachute
according to the prescribed test conditions--and it worked
perfectly."
The
Nov. 15th test follows another successful drop on Sept. 25th.
In both cases, the payload was less than the full 200,000
pounds. Nevertheless, the tests gave engineers a chance to
measure the parachute's drag area2 and validate
its design.
NASA
already has plenty of experience with parachutes: A parachute
recovery system brings shuttle solid rocket boosters back
to Earth for refurbishment and reuse, and engineers are using
a similar design for the Ares booster recovery system. The
Ares booster is much heavier and will plummet Earthward faster
than do the shuttle solid rocket boosters, so stronger materials
have to be used.
"These
chutes are made of Kevlar, and shuttle chutes are made of
nylon," says Ron King, also of Marshall. "Kevlar
is stronger and lighter than nylon, so the chute can be bigger
but fit in the same size pack and weigh less. Still, the design
for this recovery system is much the same as the shuttle's."
This
proven design may be one reason for the successful tests,
but the full story of the parachute requires a trip into history:
Leonardo
Da Vinci dreamed up the idea of a parachute almost 500 years
ago. About 100 years later, Faust Vrancic built a rigid-framed
parachute based on Da Vinci's tattered old sketches. Vrancic
tested his rickety contraption by jumping from a tower in
Venice. He somehow landed safely on the ground below. [ref]
In
1793, Jean Pierre Blanchard used silk to make the first soft,
foldable parachute. Andrew Garnerin put Blanchard's design
to the test for the first time in 1797 by leaping from a hot
air balloon. [ref]
 Right:
Andrew Garnerin performs the first recorded parachute jump.
Gouache and watercolor painting by Etienne Chevalier de Lorimier.
[Larger image]
More
than a century later, in 1912, Albert Berry thrilled onlookers
with another first by jumping from an airplane to test a parachute.
The plane took off from somewhere near St. Louis with Berry
on board. He climbed down through the fuselage frame, stood
on the axel, and hopped off. He executed a perfect drop, although
he admitted to feeling "uneasy" since he fell nearly
500 feet before the chute opened.[ref]
Fast
forward to the present and listen to Ron King, who experienced
his own moment of uneasiness during NASA's first parachute
test.
"We
were a little apprehensive because of the size and weight
of our payload," says King. "We weren't sure how
something that size would behave, but we expected success
and we got it."
The
Ares I parachute system consists of three types of parachutes:
(1) a small pilot chute, which pulls out the drogue chute;
(2) a 68-foot diameter drogue chute, which maneuvers the booster
into a vertical position and slows its descent, and (3) three
main parachutes, which slow the booster more, carrying it
to splashdown.
Testing
of the parachute system is scheduled to continue through 2010.
"These
events were the first real live tests of flight development
hardware for the Ares vehicle – our ride back to the moon,"
says King. "They represent a first step."
They
bring to mind other first steps of centuries past--like the
first steps a few men took from great heights into thin air,
supported only by their own courage and a hope that an unproven
parachute strapped to their backs would work. So far so good.
Now, on to the moon!
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Author: Dauna Coulter | Production Editor:
Dr. Tony Phillips | Credit: Science@NASA
FOOTNOTES:
1.
United Space Alliance designed and manufactured the parachute
under subcontract to Alliant Techsystems, the Ares I First
Stage prime contractor. NASA’s Marshall Space Flight Center
is the project management organization for the Ares I First
Stage and leads the design and development of the solid rocket
booster recovery system. Other parties involved in the testing
were Pioneer Aerospace, which is part of Zodiac Aerosafety
Systems, Fox Parachute Services of West Virginia, the Yuma
Army Proving Grounds in Yuma, Arizona, and the Air Force C-17
flight crew from Washington State.
2.
According to Ron King, the drag area is the amount of surface
area (measured in square feet) that the parachute canopy provides
for resisting airflow. The drag area is used to calculate
the total load (drag area X Dynamic Pressure) of the parachute,
which is the resultant force acting upward to slow the descending
booster.
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