James Webb Space Telescope sunshield is ready to fabricate

The James Webb Space Telescope's (JWST's) five-layer sunshield has passed its critical design review, meaning that its design is complete and meets mission requirements. Because it has achieved thermal, deployment, and stray-light targets, the sunshield is now ready for manufacturing.

The shield will be about the size of a regulation tennis court, says NASA; a regulation tennis court is 23.8 x 11.0 meters in size. One-third-scale membranes have already been fabricated and have undergone inspection at Nexolve (Huntsville, AL).

Sunshield manufacturing and test plans were also evaluated and approved as part of the review, which took place Jan. 11 through 14 at Northrop Grumman's space systems manufacturing facility (Redondo Beach, CA).

"This is the first time a sunshield of this size and complexity will fly on a space telescope," said Scott Willoughby, JWST program manager for Northrop Grumman Aerospace Systems.

In preparation for the design review, 18 separate subassembly design audits were conducted on the sunshield's extremely complex system of latches, tensioners, spreader bars, and telescoping boom assemblies. The goal was to validate these subassemblies at the system level and evaluate points where they interface.

A first time for everything

"There are no textbooks or guidelines on how to design and build a deployable sunshield of this size," said Keith Parrish, JWST sunshield manager at NASA Goddard Space Flight Center (Greenbelt, MD). "Nearly a decade ago, NASA and Northrop Grumman had to start from scratch and literally invent the techniques, materials, and mechanisms needed to do the job. We still have quite the challenge in front of us now that we start into the fabrication and testing phase but it's also a very exciting time."

Each of the sunshield's five membrane layers is from 0.001 to 0.002 in. thick and is made of Kapton. The layers are separated from each other and held in place by spreader bars and deployable booms. The sunshield will absorb and deflect solar light to keep the telescope and its IR detectors operating at cryogenic temperatures; the aim is to shield the JWST not just from the Sun, but from the Earth and Moon as well.

Expected to launch in 2014 (with a 70% chance of successful launch in that year?), the JWST is a joint project of NASA, the European Space Agency, and the Canadian Space Agency.