It’s hard to believe that anything could have been done cheaply to save costs on the NASA space shuttle. Yet that appears to be exactly the case with the insulation problems that have been plaguing recent flights. On Friday, cracked insulation was found on all three of the fuel tanks scheduled for upcoming flights. And the cracks have probably been there a while.
Cracks are appearing in foam-covered cork insulation that is applied to aluminum alloy brackets. The brackets, which are 17 inches long and four inches wide when foamed, support the liquid oxygen feedline on the external fuel tank. The cork prevents ice from forming on the brackets. Super-cold fuel is inside the tank. Engineers are now finally developing a better solution—replacement of the aluminum alloy with titanium. For the next shuttle flight, the foam and high-density cork insulation will be removed and replaced with foam only. The titanium parts will be ready by spring.
Bad materials engineering has been one of the banes of the space shuttle program. And the problems have not exactly been rocket science. The most famous, or course, was the O-ring failure that led to the disintegration of the Challenger in 1986. It was well known that the fluoroelastomeric materials in the O-rings had extremely poor low-temperature capabilities. Once compressed, very cold O-rings take time to return to their normal shape. Temperatures were very cold the night before the Challenger launch, but temperatures at launch time were within allowable guidelines. Because of poor communications, the problems with the O-ring materials’ properties were not adequately known, and the launch proceeded. O-ring joints now have on-board heaters that are turned on when temperatures drop below 50F.
Artificially created metamaterials are already appearing in niche applications like electronics, communications, and defense, says a new report from Lux Research. How quickly they become mainstream depends on cost-effective manufacturing methods, which will include additive manufacturing.
SpaceX has 3D printed and successfully hot-fired a SuperDraco engine chamber made of Inconel, a high-performance superalloy, using direct metal laser sintering (DMLS). The company's first 3D-printed rocket engine part, a main oxidizer valve body for the Falcon 9 rocket, launched in January and is now qualified on all Falcon 9 flights.
Lawrence Livermore National Laboratory and MIT have 3D-printed a new class of metamaterials that are both exceptionally light and have exceptional strength and stiffness. The new metamaterials maintain a nearly constant stiffness per unit of mass density, over three orders of magnitude.
Smart composites that let the material's structural health be monitored automatically and continuously are getting closer to reality. R&D partners in an EU-sponsored project have demonstrated what they say is the first complete, miniaturized, fiber-optic sensor system entirely embedded inside a fiber-reinforced composite.
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