Bottoms up

February 2024

Q: Two astrodynamicists plan to open a bar with their Nobel Prize money. They’re going to call it “The Libation Point,” and the taps will feature an IPA called “Lisa’s Juice.” Explain the two aspects of the joke and why the underlying physics are so alluring to those in their profession.

Send a response of up to 250 words that someone in any field could understand to aeropuzzler@aerospaceamerica.org by noon Eastern Feb. 15 for a chance to have it published in the next issue.

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FROM THE JANUARY ISSUE: Could a giant bat fly? 

We asked you what physics and aeronautics has to say. Clint Balog of Embry-Riddle Aeronautical University reviewed your answers.

WINNER: Although it would be intriguing to see a huge evening bat soaring over our towns, physics wouldn’t allow these massive creatures to fly. This is proven by the square-cube law, which states if the side length of an object is multiplied by a number X, the surface area would be multiplied by the square of X, while the volume and mass would be multiplied by the cube of X. This means that the mass of an object would grow at a much faster rate than the surface rate. Therefore, the cross-section, or the area, of the wings on the bat would increase at a much lower rate than the mass as the bat is growing. This ratio between the new cross-section of the wings and the new mass of the bat would not be equivalent to the ratio of the original cross-section of the wings and the original mass of the bat. This would make the bat unable to fly due to the bat’s new wing size not being large enough to support the large mass of the bat.

Vijval Katepally

AIAA high school member in Frisco, Texas

Balog would add that “the biomechanical aspects of the square-cube law also factor in. Once scaled up, the animal’s muscle cross-section would increase by the square of the scaling factor, while its mass would increase by the cube of the scaling factor. Therefore, its cardiovascular and respiratory functions would be significantly burdened and its muscular strength severely reduced. In the case of the bat, it would also have to fly faster to gain the same amount of lift as a normal-sized bat.”