“It’s been known theoretically that thin plies could reduce permeability of the hydrogen through the laminate,” Vickers says. “But the work we’ve done recently has been quite comprehensive and has shown that not only can it reduce permeability through the laminate, but it can eliminate it completely.”
Boeing halved the 5.5-mil plies used previously, adopting plies weighing 70 grams per square meter instead of 145, Rivera says. In the 5.5-meter tank, the design will also tackle the honeycomb substructure that is believed to have contributed to the X-33 tank failure by substituting a “fluted” core structure.
“It varies significantly from honeycomb in that the core of that structure is essentially a hollow tube,” Rivera says. “So if you do have any escape of gases they’re very easily vented or purged through that hollow structure.”
The test at Marshall came a short distance from the test structure where NASA’s X-33 single-stage-to-orbit testbed came to an ignominious — and expensive — end in November 1999 when its composite hydrogen tank delaminated after it was filled. Vickers says the new composite tanks can be retrofitted into existing launch vehicles, passing the weight savings along directly to increase payload capacity.
That is attracting attention in the launch-vehicle industry as new players like SpaceX and Blue Origin crank up the competition.
“There is a lot of excitement about this technology,” Vickers says. “We are being approached by other organizations, both government and industry, to transition this technology to their products.”