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Why the air umbrella is a bad idea

The air umbrella is a novel idea, but blasting away raindrops with air is going overboard. (Chuan Wang)

Umbrellas have been around seemingly forever. But if there were ever to be a second coming, it wouldn’t be a stretch to assume it would resemble the air umbrella.

Conceived in the form of a sleek wand, the device is both minimalist and high-tech. Push a button and a stream of jet air flows out from the motorized tip, generating an invisible barrier against the rain. It’s almost too perfect.

Of course, then, we have the big question of whether an actual product will ever materialize.  

For now, specifics are spare. The inventor’s fundraising campaign site on Kickstarter features a promotional video that, using a series of graphics-rendered mock-ups, details various models currently under development. Backers can choose from a compact women’s version, which measures a foot long, weighs just over a pound and is limited to 15 minute of operation on a single charge, as well as two other models that are longer and can run for 30 minutes. Near the end, there’s a brief lab demo of the latest prototype.  

With that, the air umbrella easily blew past its goal of $10,000. As of this writing, it’s raised just over $100,000, with funding set to close Friday morning.

To its credit, the air umbrella aims to solve some of the most pervasively glaring flaws of umbrella design. For one, the folding mechanism that enables canopies to collapse down also tends to give way to gusts that get caught along the inside, causing it to invert. Even when functionally intact, some parts can still poke passerbys. There’s also that annoying “wet umbrella” problem.   

A handful of start-ups have tried tackling these deficiencies through clever redesigns, though all fall short in some way. Alternatives include the redrawn Rainshader, with a canopy that’s curved downward, away from nearby pedestrians and the Senz umbrella, a variant that’s aerodynamically-formulated to channel wind flow fluidly across the surface to prevent the kind of resistance that can flip an umbrella inside-out. In Japan, inventor Hiroshi Kajimoto introduced the UnBRELLA, which, ironically, is designed to fold inside-out to allow excess droplets to drain out. 

The air umbrella design isn’t besieged with any of these complications because, well, there’s no actual physical canopy, so to speak. Simply put, as raindrops fall, a continuous stream of fast-moving air catches and blows them sideways. The physics is somewhat similar to how a leaf blower works.

“Rain falls at a terminal velocity or steady speed of 7 mph, which is reasonably slow,” explains Louis Bloomfield, a physics professor at the University of Virginia and author of How Things Work: The Physics of Everyday Life. “So with a consistent wind force, you can conceivably redirect their path away from the person below.”

While Bloomfield, who has no connection to the project, deems the technology to be fundamentally sound, he did question the practicality of a high-priced (starting at $88) gadget that weighs up to two pounds and takes at least an hour to recharge.

“With jetted air, you have only a fraction of a second to get it going sideways very quickly and that’ll require a lot of power to produce forces that strong,” he adds. “I imagine if you’re going for a walk, it’s likely the battery will run out on you.”

And though no one is in danger of getting poked, sharing a sidewalk with an air umbrella will likely mean enduring another kind of annoyance. 

“For people nearby, it might feel like walking in a windstorm because they’ll definitely feel a breeze,” he says. “It’ll probably be worse for the person next to you because they’ll also be sprayed by the drops that are being blown aside.”

His recommendation? Stick with a standard, unpowered $5 umbrella. 

“Even if you have a fancy, high-tech device, you’re still going to end up needing a regular umbrella anyway.” he says. “That kind of defeats the purpose, I think.”