Image: Warner Bros.
Not all superheroes wear capes, but many do, and it’s a long-established fact that these capes are crucial when it comes to flying around town to fight crime and brood and whatnot. And yet the people still don’t know, with anything approaching certainty, how exactly capes facilitate this process (at least, the capes that aren’t themselves imbued with the power of flight).
To clear up the confusion, for this week’s Giz Asks we reached out to a number of experts in engineering to figure out whether capes are actually aerodynamic. The consensus seems to be that capes are not really that aerodynamic at all, when you get right down to it. Just the opposite, really. But the mechanics here are interesting, and for those of you still interested in cape-assisted flight, a number of plausible alterations are proposed below.
Jamey Jacob
Professor, Mechanical and Aerospace Engineering, Oklahoma State University
Capes by themselves are not aerodynamic in the sense of producing lift or reducing drag. Thus, Superman’s cape serves no real purpose other than complimenting the Man of Steel’s costume color scheme, or providing some moderate warmth from upper level air currents. However, they do have an aerodynamic impact. Much like a flag flapping in the breeze, they would generate a drag force and flutter under certain conditions. Thus, from a purely aerodynamic perspective, an unsupported cape is detrimental—not beneficial—to flight.
That said, it is possible to make a cape provide useful aerodynamic forces if you can design it to retain a specific shape. Hang gliders or Rogallo wings do this for example, by stretching a thin fabric between a supporting frame, while parafoils do this by using ram air to inflate the fabric. In these cases, the flexible fabric forms an airfoil shape to produce a lift force. Thus a cape with this structure could be configured as a wing to produce aerodynamic lift and provide limited flight control for a superhero. Wingsuits do this by enhancing the a skydiver’s ability to produce limited lift by providing additional surface area and allowing the skydiver to control the distribution of aerodynamic forces using their limbs. However, this is moving away from what we normally consider to be termed a cape.
As Edna Mode said, “No capes!”
Geoffrey Spedding
Professor, Aerospace and Mechanical Engineering, USC
In some way [yes, they are], since anything that travels through the air experiences aerodynamic forces, then of course they must be. But the real answer is no. The question really means can they generate useful aerodynamic forces, and as usually configured, they will instead flutter uselessly like flags.
You could get them to act like wings, if you could have a leading edge spar that stiffened, and then some trailing spars and/or some way of maintaining tension in the cape. Perhaps the trailing edge would be elastic and then fixed tightly to the hips in a belt that could tighten the sheet up. What you have now ended up with is something that resembles a bat wing, or a hang-glider. Bats and hang-gliders use flexible membranes and they work quite well.