Maybe spider silk? Spiderman is cool. Yup, make it out of spider silk and that would sell a lot of cars.
What Volvo doesn't mention though is that if you extract that kind of energy from a single flywheel system the car will spin violently if the tires break traction. The only way to handle that much torque is to have a dual flywheel system using counter rotation to negate that rotational torque. Step on the gas a little too hard when on ice and you are out for quite a surprise.
Yes, having a router is better than having no router, but only if YOU still own it. Once the bad guys p0wn it then it is no longer your friend.
Also, hypersonic technology is hard. Do the math. Its a lot harder than either politicians or reporters might think. Just because somebody can test a vehicle for a short distance (ie tens of seconds) does not mean it is a viable solution to anything. Making one that actually flies for any duration and can maneuver and evade is not yet a reality. At those speeds you don't need much to go wrong, to get going really really wrong. Its very unforgiving above Mach 7.
There are very few countries that can pull it off right now and they are not even the ones we particularly need to worry about. Those that we do need to worry about are still trying to figure out simple ICBM's, which is a full magnitude easier than even the simplest short duration hypersonic flight, and a whole lot cheaper to make.
Today is a good day for information-gathering. Read someone else's mail file.