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 Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials
17.01.2018 | Universität des Saarlandes

nachricht Black hole spin cranks-up radio volume
15.01.2018 | National Institutes of Natural Sciences

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: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Polymers Based on Boron?

18.01.2018 | Life Sciences

Bioengineered soft microfibers improve T-cell production

18.01.2018 | Life Sciences

World’s oldest known oxygen oasis discovered

18.01.2018 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>