Rotor Stator windings Stator iron Figure 24. Cross section of rotor inside stator 4.3.3. Energy Storage Components Energy storage allows this linear accelerator to only draw its average power of 8,000 hp (6 MW) (rather than the peak power of 70,000 hp or 52 MW) from its solar array. Building the energy storage element out of the same lithium ion cells available in the Tesla Model S is economical. A battery array with enough power capability to provide the worst-case smoothing power has a lot of energy – launching 1 capsule only uses 0.5% of the total energy – so degradation due to cycling is not an issue. With proper construction and controls, the battery could be directly connected to the HVDC bus, eliminating the need for an additional DC/DC converter to connect it to the propulsion system. 4.3.4. Cost As described above, the propulsion elements on the capsule are limited to the rotor and not expected to cost any more than $3 million USD for the overall system. The bulk of the propulsion cost is for the stator elements connected to the track and for the inverters to drive the stator. All tube-side propulsion costs together for linear accelerators add up to $140 million USD. This cost is roughly divided as followed: - Stator and structure materials = 54%