Pogo sticks and rockets

October 2024

Q: Why should every rocket scientist know what a pogo stick is?

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FROM THE SEPTEMBER ISSUE: We asked you to choose between two endings for an action film scene in which water is about to reach the battery pack of an air taxi that’s been ditched into the ocean with a hero and villain aboard. None of the responses chose the correct ending, so we asked Matt Alonis, an aerospace engineering fellow at TE Connectivity, to provide an answer:

“The answer is B — Our hero jumps into the ocean and starts swimming away furiously. The screen goes black and we cut to a yacht, where the hero requests a Fireball old fashioned and toasts the villain: ‘Better to go out with a bang.’

“In a standard eVTOL design, the batteries and high voltage cables would likely be in the wings, which are higher than the passenger compartment. Thus, there would not be a significant risk of touching unprotected power cables to complete the circuit. Electrical energy follows Ohm’s Law (I = V/R) and consequently, the path of least resistance, so being in contact with the water doesn’t guarantee the villain would be shocked even if the battery is submerged in the ocean, as the short distance between battery terminals is significantly closer than the distance to the passengers, resulting in a very high resistive path to the passengers, thus negligible current reaching them.

“The greatest risk in the scene is a battery fire or explosion. Without a battery management system, there is high likelihood that the eVTOL battery would overheat and catch fire. The hero should swim away from the battery pack and hope his adversary is a slow swimmer.”