Editing Transrapid (section)

===Energy requirements===
The normal energy consumption of the Transrapid is approximately {{convert|50|to|100|kW}} per section for levitation and travel, and vehicle control. The [[drag coefficient]] of the Transrapid is about 0.26. The [[aerodynamic drag]] of the vehicle, which has a frontal cross section of {{Convert|16|m2|0|abbr=on}},{{Citation needed|date=May 2014}} requires a power consumption, at {{Convert|400|km/h|0|abbr=on}} or {{Convert|111|m/s|0|abbr=on}} cruising speed, given by the following formula:

<math>
P = c_w \cdot A_{\rm Front} \cdot v^3 \cdot (\mbox{density of surrounding air})/2
</math>

<math>
\begin{matrix}
P &=& 0{.}26 \cdot 16\,\mathrm{m}^2 \cdot (111\,\mathrm{m}/\mathrm{s})^3 \cdot 1{.}24\,\mathrm{kg}/\mathrm{m}^3 /2 \\
P &=& 3{.}53\cdot10^6\,\mathrm{kg}\cdot\mathrm{m}^2/\mathrm{s}^3 = 3{.}53\cdot10^6\,\mathrm{N}\cdot\mathrm{m}/\mathrm{s} = 3{.}53\,\mathrm{MW}
\end{matrix}
</math>

Power consumption compares favourably with other high-speed rail systems. With an efficiency of 0.85, the power required is about 4.2&nbsp;MW. Energy consumption for levitation and guidance purposes equates to approximately 1.7&nbsp;kW/t. As the propulsion system is also capable of functioning in reverse, energy is transferred back into the [[electrical grid]] during braking. An exception to this is when an emergency stop is performed using the emergency landing skids beneath the vehicle, although this method of bringing the vehicle to a stop is intended only as a last resort should it be impossible or undesirable to keep the vehicle levitating on back-up power to a natural halt.