Roumen.ganeff

For more than a century, air cars have remained a quixotic quest of engineers—an idealistic exercise with little long-term likelihood of entering mass production. As fuels go, air has obvious upsides: It’s ubiquitous, clean, and, best of all, free. But air requires energy to store energy because it must be compressed, limiting the utility of an all-air car. Two engineers from French automaker PSA Peugeot Citroën thought they could overcome that problem by pairing two tried-and-true technologies: a gasoline engine and hydraulics. To test the concept, they formed the Hybrid Air Program in 2010 and connected the engine of a subcompact car to a commercial airplane’s hydraulic system. “We were trying to push the project against a lot of people who didn’t trust the fact that we would succeed,” says engineer Karim Mokaddem. 

The Hybrid Air powertrain, which Mokaddem designed with Andrés Yarce, uses a hydraulic pump and a piston to compress the nitrogen gas in a tank called the high-pressure accumulator. Hitting the accelerator releases the pressurized gas, which then moves hydraulic fluid through the same pump in reverse. The pump acts as a motor to power the wheels and the hydraulic fluid ends up in a second tank. 

During normal driving, the system will switch between gas and air power, says Yarce. Much like with hybrid-electric vehicles, the gasoline engine provides a boost up steep hills and on the highway, and it repressurizes the nitrogen tank if the regenerative-braking system hasn’t done so. Yarce and Mokaddem predict that, for urban driving less than 43 miles per hour, between 60 and 80 percent of drive time will be under air power alone. Compared with gasoline-electrics, the Hybrid Air powertrain is lighter and cheaper, and there are no bulky batteries that wear out or intrude on passenger and trunk space. “The system is designed to live for the life of the vehicle,” says Yarce. “The only possible [maintenance] will be an air recharge.”

Yarce and Mokaddem’s prototype was so successful that PSA Peugeot Citroën has decided to manufacture production vehicles. The Hybrid Air powertrain will appear in all Citroën and Peugeot subcompacts as an option in Europe and possibly other international markets in 2016. The company hasn’t yet released a price, but it says that its air cars will cost around the same amount as other gasoline hybrids. 

The Air Car

Illustration by Graham Murdoch

1) The Hybrid Air Car uses compressed nitrogen, which is held in a tank called the high-pressure accumulator.

2) A hydraulic pump and piston compress nitrogen in the accumulator. When the nitrogen is released (by pressing the accelerator), the pump runs in reverse. Acting now as a motor, it harnesses the energy of the moving hydraulic fluid to send power to the wheels.

3) After the hydraulic fluid passes through the motor, it flows to the low-pressure accumulator, where it is stored for later use.

4) A gasoline engine supplements the air power when accelerating or going up hills. This could be an 82-hp 1.2 L I3 for subcompacts and a 110-hp 1.6 L I4 for compacts.

This article originally appeared in the March 2014 issue of Popular Science.

The Harmon Kardon Aura

Jonathon Kambouris

For all their engineering, speakers are mostly just formless boxes—eyesores that we shove into corners and forget about. The Harmon Kardon Aura is one that even the most design-conscious can proudly plop in the middle of their living rooms. Engineers molded the six-driver Bluetooth speaker into a retro-futuristic dome that evenly distributes audio 360 degrees. A 30-watt subwoofer fires up into the dome, which radiates the bassline up, out, and into the room—instead of into the floor. Interior LEDs sync with the music to draw a little extra attention.

Harman Kardon Aura

Drivers: Six, plus subwoofer 
Frequency: Response 50 Hz to 20 kHz
Price: $399

This article originally appeared in the March 2014 issue of Popular Science.

Class 10 and ready for HD video

At Mobile World Congress, SanDisk announced the world's first 128 GB microSD memory card. It's Class 10 UHS-I with read speeds around 30 MB/s and should be compatible with any device that can support SDXC, which includes most Android devices launched over the last few years. SanDisk also took the opportunity to announce a 64 GB embedded NAND module tailored specifically to Android devices, though right now they're just sampling it to partners.

If we're going to be going around shooing 4K video on our devices, it's a good thing that memory is increasing so we can actually save that footage. Plus, the Samsung Galaxy S5 ROM size may also make you wish for a little bit more room. Beyond that, it's hard to imagine loading up that much music manually. Still, at times like this I really feel for those that don't have access to their SD card slot.

Amazon and Best Buy are going to be the exclusive outlets for the new cards, which are available right now for $119.99. How much room do you have free on your device storage? Are you going to pick up one of these 128 GB cards? Does having this much room enable any new use cases?

The Samsung Gear Fit will track your exercise routines and look snazzy while doing it

In addition to taking the wraps off the Galaxy S5 at Mobile World Congress, Samsung also announced their next wearable device dubbed the Gear Fit. As you can see, the big sell here is a curved 1.8-inch 432 x 128 Super AMOLED display. It's dust and water resistent to keep up with whatever brutal fitness regimen you're undertaking. As usual, you'll be able to get smartphone notifications from just about everything on the Gear Fit thanks to Bluetooth 4.0 connectivity. Keep in mind that the Gear Fit will only work with Samsung devices, but given all of the tracking software built in, that limitation may be worthwhile. The 210 mAh battery should last you 3 - 4 of typical usage.