Composite Construction Under Consideration For Human
Spaceflight
A NASA team looking into design concepts for future space
capsules has successfully demonstrated that an all-composite
structure is a feasible alternative to traditional metal capsules
for carrying astronauts into space and returning them safely to
Earth, the agency announced Monday.
The composite materials that make up the structure are basically
the same as the tough, lightweight laminates used today for race
cars, business jets and high-end sports equipment.
In combination with new space-age fabrication techniques, these
advanced composite materials promise potential benefits over
traditional metal structures. Among them is that they can easily be
formed into complex shapes that may be more structurally efficient
-- a desirable trait for future generations of spacecraft.
A team led by the NASA Engineering and Safety Center (NESC)
developed and tested the capsule - called a crew module - in a
series of full scale structural tests at NASA's Langley Research
Center, Hampton, VA, over a several month period. The full-scale
crew module was pressurized to design limits while critical
interfaces - like the landing system main parachute fitting -- were
pulled to simulate the combined loads a future crew module might
see during launch and return to Earth. No trouble spots were
detected.
Composite Crew Module
After passing those and other combined tests, follow-on tests
checked for damage tolerance, a question of critical importance for
composite structures. The crew module was subjected to measured
impacts in multiple locations to simulate the kind of damage that
might take place in the life of the structure - specifically, the
equivalent of tool drops and routine handling damage. The module
was then stressed to simulate the expected life cycle of a
space-going composite structure. At points along the way, the
damaged sites were inspected by non-destructive means, using both
infrared thermography and ultrasonic techniques, to characterize
subsurface damage and damage progression.
"Our tests showed that a composite module can 'achieve the
mission' with damage that is likely to occur but could go
undetected," said Mike Kirsch, manager of the Composite Crew Module
(CCM) project. "The test article withstood twice the design
internal pressures with known damage and then was subjected to
cyclic testing to four times the design life with no detrimental
damage growth," he added.
A follow-on round of impact assessments is planned to study the
effects of higher impact energies. "We are very pleased with the
entire test series. Throughout testing, there were no anomalies and
performance aligned amazingly well with analytical predictions,"
Kirsch said.