High-speed testing for wheels
Wheels have great potential for improvement, because there has never been serious high-speed testing. Pneumatic tires have been used at 1000 km/h 45 years ago, but not developed further, despite advances in materials and tire technology. Solid aluminium wheels have done 1,200 km/h, but no faster due to the speed of sound.
A considerable budget is available for wheel research, as $billions can be saved in the cost of a simple tube without rails, linear motors etc.
Rolling road test rig can be used for initial research.
Full speed pod testing would need a test track at least 45km long.
A CFD study is important to study aerodynamic drag.