Credit: NASA/JPL-Caltech Caltech grad students helped JPL build a custom wind tunnel in a vacuum chamber for the Mars Ingenuity helicopter The Ingenuity helicopter may be the first vehicle ever to fly on Mars, but Mars was not the first place it has ever flown. Before packaging it up and blasting it to the Red Planet, engineers at JPL gave the helicopter a trial run in a special wind tunnel designed with help from researchers at Caltech. To simulate flying on a planet where the atmosphere is 100 times thinner than Earth’s, a custom wind tunnel was built inside of an 85-foot-tall, 25-foot-diameter vacuum chamber at JPL, which Caltech manages for NASA. Pressure in the chamber was pumped down to approximate the Martian atmosphere, while an array of 441 pairs of individually controllable fans blew on the helicopter to simulate forward flight in the enclosed space.