Andrew Yee[_1_]
March 26th 08, 04:16 AM
Robert Garner
Goddard Space Flight Center, Greenebelt, Md. March 13, 2008
301-286-5687
NASA Goddard Provides Environmental Testing for Hubble Components
Space is not a hospitable place, and when scientists and engineers design
and build new components for the Hubble Space Telescope, that fact is always
clearly in mind.
Hubble must endure harsh temperature swings of 215 F, micro-meteor impacts
and exposure to solar radiation. On top of that, before a spacecraft like
Hubble can operate in orbit, it has to survive the trip to get there. That's
where the environmental testing chambers at NASA's Goddard Space Flight
Center in Greenbelt, Md., come into play.
When astronauts travel to the telescope later this year on Servicing Mission
4, they will take with them 22,000 pounds of cargo, including Wide Field
Camera 3 and the Cosmic Origins Spectrograph, Hubble's new, high-powered
scientific instruments.
Most of that cargo -- tools, supplies, instruments, and the like -- gets run
through Goddard's centrifuge, acoustics and thermal vacuum chambers to
ensure it can endure the rigors of launch on the space shuttle and the
harshness of space travel while orbiting more than 350 miles above Earth's
surface.
These chambers, only a sample of the dozens at Goddard, are housed in the
center's Environmental Test and Integration Facilities.
High-Capacity Centrifuge Facility
The centrifuge simulates the increased feeling of gravity's pull during a
launch. For astronauts, that's normally a few minutes at two or three times
the force of Earth's gravity, measured in Gs. The equipment being carried in
the shuttle's cargo bay usually sees between 6 and 7 Gs because of
vibration.
Goddard's 120-foot-diameter centrifuge can accelerate a 2.5-ton payload up
to 30 Gs, well beyond the force experienced in a launch. The most intense
roller-coasters in the world top out at about 5 Gs, and then only for brief
moments.
Technicians did not subject the new components going to Hubble on Servicing
Mission 4 to the centrifuge's full intensity, because they will never
experience forces that great in their operational lifetimes.
Still, engineers run the tests a little beyond actual environment
conditions. "We take the structural loading conditions that we expect to see
during launch and then jack them up 25 percent," says Mike Weiss, Hubble's
technical deputy program manager at Goddard.
Instruments should be able to handle actual conditions if they hold up to
the increased, simulated experience. Two 1,250-horsepower motors help the
centrifuge produce that experience.
Acoustic Test Chamber
It's true that in space no one can hear you scream. Blastoff, on the other
hand, can make quite a racket, which is why the Hubble engineers use the
Acoustic Test Chamber.
In this 42-foot-tall chamber, technicians expose payloads to the noise of a
launch. To do that, they rely on 6-foot-tall speakers.
The speakers (more accurately called horns) use an altering flow of gaseous
nitrogen to produce a sound level as high as 150 decibels for two-minute
tests. That's about the level of sound heard standing next to a jet engine
during takeoff.
The speakers are still audible -- at greatly reduced volume -- outside the
chamber, even through the insulation of the massive metal doors.
Thermal Vacuum Chamber
Weiss calls the thermal vacuum "the granddaddy of them all." More so than
any of the other chambers, this chamber exposes the Hubble components (and
other payloads) to conditions they will experience in space.
The chamber has massive mechanical vacuum pumps, which are essentially large
versions of the vacuum cleaners people use at home. To augment those, the
chamber uses cryopumps to ensure that the hard vacuum of space is simulated
in the test chamber. The cryopumps use liquid nitrogen to condense remaining
gases out of the chamber once the mechanical pumps have done their work.
The two types of pumps work together to eliminate all but the tiniest trace
of air in the chamber, down to about a billionth of Earth's normal
atmospheric pressure.
To simulate the hot and cold extremes possible in Hubble's neighborhood, 350
miles up, the thermal vacuum chamber can reach temperatures in a 600-degree
range from 302 F all the way down to minus 310 F. This chamber is the
perfect place to test Hubble's thermal protection for that reason, though
the chamber will not need to be pushed to its extremes for the trials.
Wide Field Camera 3, built at Goddard, has also spent considerable time in
the chamber. This powerful new camera will replace Wide Field and Planetary
Camera 2, installed on the telescope during the first servicing mission in
1993.
Engineers tested the new camera in the vacuum chamber by sending commands
identical to those it will receive in orbit. Temperature, vacuum and
commands combine to make the camera behave exactly as it will once
astronauts install it. The vacuum chamber tests have shown that the
instrument will function properly.
Hubble may seem like a fragile telescope at first, and in a lot of ways it
is. Its solar arrays, antennas and data-gathering instruments are delicate,
but Hubble has a robust structure well suited for durability in low-Earth
orbit and servicing by shuttle astronauts, Weiss says.
But even after completing their chamber run-throughs, the Hubble components
will have one last layover in the Space Systems Development Facility at
Goddard. This facility houses the world's largest Class-10,000 clean room, a
place where Hubble's hardware will be tested and inspected one last time
before launch.
For related images and more information, please visit:
http://www.nasa.gov/centers/goddard/news/topstory/2008/testing_chambers.html
Goddard Space Flight Center, Greenebelt, Md. March 13, 2008
301-286-5687
NASA Goddard Provides Environmental Testing for Hubble Components
Space is not a hospitable place, and when scientists and engineers design
and build new components for the Hubble Space Telescope, that fact is always
clearly in mind.
Hubble must endure harsh temperature swings of 215 F, micro-meteor impacts
and exposure to solar radiation. On top of that, before a spacecraft like
Hubble can operate in orbit, it has to survive the trip to get there. That's
where the environmental testing chambers at NASA's Goddard Space Flight
Center in Greenbelt, Md., come into play.
When astronauts travel to the telescope later this year on Servicing Mission
4, they will take with them 22,000 pounds of cargo, including Wide Field
Camera 3 and the Cosmic Origins Spectrograph, Hubble's new, high-powered
scientific instruments.
Most of that cargo -- tools, supplies, instruments, and the like -- gets run
through Goddard's centrifuge, acoustics and thermal vacuum chambers to
ensure it can endure the rigors of launch on the space shuttle and the
harshness of space travel while orbiting more than 350 miles above Earth's
surface.
These chambers, only a sample of the dozens at Goddard, are housed in the
center's Environmental Test and Integration Facilities.
High-Capacity Centrifuge Facility
The centrifuge simulates the increased feeling of gravity's pull during a
launch. For astronauts, that's normally a few minutes at two or three times
the force of Earth's gravity, measured in Gs. The equipment being carried in
the shuttle's cargo bay usually sees between 6 and 7 Gs because of
vibration.
Goddard's 120-foot-diameter centrifuge can accelerate a 2.5-ton payload up
to 30 Gs, well beyond the force experienced in a launch. The most intense
roller-coasters in the world top out at about 5 Gs, and then only for brief
moments.
Technicians did not subject the new components going to Hubble on Servicing
Mission 4 to the centrifuge's full intensity, because they will never
experience forces that great in their operational lifetimes.
Still, engineers run the tests a little beyond actual environment
conditions. "We take the structural loading conditions that we expect to see
during launch and then jack them up 25 percent," says Mike Weiss, Hubble's
technical deputy program manager at Goddard.
Instruments should be able to handle actual conditions if they hold up to
the increased, simulated experience. Two 1,250-horsepower motors help the
centrifuge produce that experience.
Acoustic Test Chamber
It's true that in space no one can hear you scream. Blastoff, on the other
hand, can make quite a racket, which is why the Hubble engineers use the
Acoustic Test Chamber.
In this 42-foot-tall chamber, technicians expose payloads to the noise of a
launch. To do that, they rely on 6-foot-tall speakers.
The speakers (more accurately called horns) use an altering flow of gaseous
nitrogen to produce a sound level as high as 150 decibels for two-minute
tests. That's about the level of sound heard standing next to a jet engine
during takeoff.
The speakers are still audible -- at greatly reduced volume -- outside the
chamber, even through the insulation of the massive metal doors.
Thermal Vacuum Chamber
Weiss calls the thermal vacuum "the granddaddy of them all." More so than
any of the other chambers, this chamber exposes the Hubble components (and
other payloads) to conditions they will experience in space.
The chamber has massive mechanical vacuum pumps, which are essentially large
versions of the vacuum cleaners people use at home. To augment those, the
chamber uses cryopumps to ensure that the hard vacuum of space is simulated
in the test chamber. The cryopumps use liquid nitrogen to condense remaining
gases out of the chamber once the mechanical pumps have done their work.
The two types of pumps work together to eliminate all but the tiniest trace
of air in the chamber, down to about a billionth of Earth's normal
atmospheric pressure.
To simulate the hot and cold extremes possible in Hubble's neighborhood, 350
miles up, the thermal vacuum chamber can reach temperatures in a 600-degree
range from 302 F all the way down to minus 310 F. This chamber is the
perfect place to test Hubble's thermal protection for that reason, though
the chamber will not need to be pushed to its extremes for the trials.
Wide Field Camera 3, built at Goddard, has also spent considerable time in
the chamber. This powerful new camera will replace Wide Field and Planetary
Camera 2, installed on the telescope during the first servicing mission in
1993.
Engineers tested the new camera in the vacuum chamber by sending commands
identical to those it will receive in orbit. Temperature, vacuum and
commands combine to make the camera behave exactly as it will once
astronauts install it. The vacuum chamber tests have shown that the
instrument will function properly.
Hubble may seem like a fragile telescope at first, and in a lot of ways it
is. Its solar arrays, antennas and data-gathering instruments are delicate,
but Hubble has a robust structure well suited for durability in low-Earth
orbit and servicing by shuttle astronauts, Weiss says.
But even after completing their chamber run-throughs, the Hubble components
will have one last layover in the Space Systems Development Facility at
Goddard. This facility houses the world's largest Class-10,000 clean room, a
place where Hubble's hardware will be tested and inspected one last time
before launch.
For related images and more information, please visit:
http://www.nasa.gov/centers/goddard/news/topstory/2008/testing_chambers.html