To push the envelope of transportation technology, you need to think big.
And as globalization continues to drive advances in ways to move people and goods around the world faster and cheaper, there's no shortage of ideas.
Some of them may never fly. But others that seemed futuristic just 25 years ago may be commonplace by 2039.
Major carmakers, for example, are hard at work developing autonomous cars that will put computers in charge of braking, steering and avoiding crashes—allowing drivers to text message and surf the Web while on their way to work.
Battlefield advances in unmanned drones are spawning a new generation of flying vehicles able to deliver freight to soldiers in remote locations. The ongoing spread of online shopping makes civilian applications of the technology all but inevitable.
But sometimes even the best ideas never leave the drawing board. Some are derailed by a wide range of forces—from advances in competing technologies to changes in the cost of materials or fuel.
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For engineers working on the cutting edge, that can be a delicate balancing act.
"It's sort of like, how do you write a song—do the lyrics come first or the music?" said Robert Boyd, a program manager at Lockheed's Skunk Works unit, devoted to advanced aircraft technologies. "Sometimes it goes both ways. What we create are products at the intersection of what's possible with what's needed."