Webb: The Stiffest Backbone in Space

Blake Bullock, blake.bullock@ngc.com

JWST-backboneAcross the country, teams of highly skilled engineers and technicians are building the backbone of the mighty James Webb Space Telescope.  This four-story-tall scaffolding, called the backplane, is one of the largest cryogenic structures ever built.  While its sheer size and visual complexity are impressive, the backbone’s engineering breakthrough is its amazing ability to remain almost perfectly still and rigid under extreme environmental conditions.

Imagine the magnitude of the tasks to design and build a structure to both withstand the violent rocket launch from the humid shores of Kourou, French Guiana, and then not flex more than 38 nanometers—approximately 1/1,000 of the diameter of a human hair—after it arrives at its station at L2, one million miles from Earth, where it will operate at temperatures as low as –400° F.

The role of Webb’s backplane is to support the primary mirror—18 hexagonal segments of polished beryllium—and the science instrument module containing the flight cameras and spectrographs. Fully loaded, it will weigh over 7,000 lbs., more than three times the weight of the structure itself.

It takes a team to invent and build unique hardware like the Webb backplane, and NASA has called on the diverse talents of many aerospace contractors.  Northrop Grumman Aerospace Systems of Redondo Beach, California, is responsible for the design and development of the entire observatory, including the telescope, the deployable sunshield, and the spacecraft bus. Ball Aerospace of Boulder, Colorado, ATK of Magna, Utah, and ITT Exelis of Rochester, New York, are among the 193 suppliers across the country contributing expertise and facilities to build components and systems for Webb.

In June, ATK completed the last piece of the support frame, a critical component at the core of the structure, which brings together Webb’s center section, hinged wings, secondary mirror support structure and the integrated science instrument module. In all, ATK designed, engineered, and constructed more than 10,000 parts for this piece, many from ultra-lightweight graphite. To ensure the stiffness and stability Webb requires, every connection point within this structure was manufactured with high precision, down to customized metallic fittings made of special materials, such as Invar and titanium.1

In August 2013, ATK shipped the Webb backbone structure to NASA’s Marshall Space Flight Center in Huntsville, Alabama, for cryogenic thermal testing, which will occur in the x-ray and cryogenic facility.2 From there, the structure will be shipped to Northrop Grumman for structural static testing, during which a team of engineers and technicians will carefully push, pull, and press on the hardware. Then, the structure will be ready to accept the telescope and instruments for the ultimate cryogenic-vacuum test, in Chamber A at Johnson Space Center, in Houston, Texas.

 

__________

1 Behind the Webb, episode 18, On the Wings of Webb
2 Press release