Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

NASA's Webb Telescope unique structural 'heart' passes extreme tests

29.09.2010
NASA engineers have created a unique engineering marvel called the ISIM structure that recently survived exposure to extreme cryogenic temperatures, proving that the structure will remain stable when exposed to the harsh environment of space. The material that comprises the structure, as well as the bonding techniques used to join its roughly 900 structural components, were all created from scratch.

The ISIM, or the Integrated Science Instrument Module Flight Structure, will serve as the structural "heart" of the James Webb Space Telescope. The ISIM is a large bonded composite assembly made of a light weight material that has never been used before to support high precision optics at the extreme cold temperatures of the Webb observatory.

Imagine a place colder than Pluto where rubber behaves like glass and where most gasses are liquid. The place is called a Lagrange point and is nearly one million miles from Earth, where the Webb telescope will orbit. At this point in space, the Webb telescope can observe the whole sky while always remaining in the shadow of its tennis-court-sized sunshield. Webb's components need to survive temperatures that plunge as low as 27 Kelvin (-411 degrees Fahrenheit), and it is in this environment that the ISIM structure met its design requirements during recent testing. "It is the first large, bonded composite space flight structure to be exposed to such a severe environment," said Jim Pontius, ISIM lead mechanical engineer at NASA's Goddard Space Flight Center in Greenbelt, Md.

The passage of those tests represent many years of development, design, analysis, fabrication, and testing for managing structural-thermal distortion.

The ISIM structure is unique. When fully integrated, the roughly 2.2-meter (more than 7 feet) ISIM will weigh more than 900 kg (nearly 2000 lbs) and must survive more than six and a half times the force of gravity. The ISIM structure holds all of the instruments needed to perform science with the telescope in very tight alignment. Engineers at NASA Goddard had to create the structure without any previous guidelines. They designed this one-of-a-kind structure made of new composite materials and adhesive bonding technique that they developed after years of research.

The Goddard team of engineers discovered that by combining two composite fiber materials, they could create a carbon fiber/cyanate-ester resin system that would be ideal for fabricating the structure's 75-mm (3-inch) diameter square tubes. This was confirmed through mathematical computer modeling and rigorous testing. The system combines two currently existing composite materials — T300 and M55J — to create the unique composite laminate.

To assemble the ISIM structure, the team found it could bond the pieces together using a combination of nickel-iron alloy fittings, clips, and specially shaped composite plates joined with a novel adhesive process, smoothly distributing launch loads while holding all instruments in precise locations — a difficult engineering challenge because different materials react differently to changes in temperature. The metal fittings also are unique. They are as heavy as steel and weak as aluminum, but offer very low expansion characteristics, which allowed the team to bond together the entire structure with a special adhesive system.

"We engineered from small pieces to the big pieces testing all along the way to see if the failure theories were correct. We were looking to see where the design could go wrong," Pontius explained. "By incorporating all of our lessons learned into the final flight structure, we met the requirements, and test validated our building-block approach."

The Mechanical Systems Division at NASA Goddard performed the 26-day test to specifically test whether the car-sized structure behaved as predicted as it cooled from room temperature to the frigid — very important since the science instruments must maintain a specific location on the structure to receive light gathered by the telescope's 6.5-meter (21.3-feet) primary mirror. If the contraction and distortion of the structure due to the cold could not be accurately predicted, then the instruments would no longer be in position to gather data about everything from the first luminous glows following the big bang to the formation of star systems capable of supporting life.

The test itself also was a first for NASA Goddard because the technology needed to conduct it exceeded the capabilities then offered at the center. "The multi-disciplinary (test) effort combined large ground-support equipment specifically designed to support and cool the structure, with a photogrammetry measuring system that can operate in the cryogenic environment," said Eric Johnson, ISIM Structure Manager at NASA Goddard. Photogrammetry is the science of making precise measurements by means of photography, but doing it in the extreme temperatures specific to the Webb telescope was another obstacle the NASA engineers had to overcome.

Despite repeated cycles of testing, the truss-like assembly designed by Goddard engineers, did not crack. Its thermal contraction and distortion were precisely measured to be 170 microns — the width of a needle — when it reached 27 Kelvin (-411 degrees Fahrenheit), well within the design requirement of 500 microns. "We certainly wouldn't have been able to realign the instruments on orbit if the structure moved too much," Johnson said. "That's why we needed to make sure we had designed the right structure."

The same testing facility will be used to test other Webb telescope systems, including the telescope backplane, the structure to which the Webb telescope's 18 primary mirror segments will be bolted when the observatory is assembled.

For an in-depth feature story WITH a VIDEO and IMAGES: http://www.nasa.gov/topics/technology/features/jwst-unobtainium.html

Rob Gutro | EurekAlert!
Further information:
http://www.nasa.gov

More articles from Physics and Astronomy:

nachricht Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst

nachricht Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Northern oceans pumped CO2 into the atmosphere

27.03.2017 | Earth Sciences

Fingerprint' technique spots frog populations at risk from pollution

27.03.2017 | Life Sciences

Big data approach to predict protein structure

27.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>