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Pathfinder: a Solar EV Airplane That Ate Altitude Records for Lunch, Without Any Pollution

A short time ago, we explained why electrically propelled aircraft are so much more difficult to build than their road roving four and two-wheeled counterparts.
Pathfinder 6 photos
Photo: NASA
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But the scientific achievement was never advanced by throwing in the towel and calling things too difficult. If there was anyone we'd trust to design such a radical design, NASA would probably be our pick. Happily, they're well ahead of us on this. Their most famous electric aircraft has already been built, tested, and placed inside a massive aerospace museum for all of us plebians to admire.

Meet Pathfinder, no, not the Mars lander although it was also an EV if you think about it. Before it came around, the idea of an all-electric aircraft seemed like a total pipe dream to all but the most radical of aerospace engineers. Aviation fuel wasn't all that expensive back in the early 1980s, especially if you know how expensive it is at the moment.

It would seem Americans, at least, assumed the 1973 oil crisis would be a one-time affair. With this false sense of security in mind, interest in the EVs air, or land, was at an all-time low. But when it comes to what NASA was up to at the time, the story was altogether different. There's no air for internal combustion to take place in space after all.

High-efficiency photovoltaic cells were to become the rugged backbone of the global space race beginning in the late 1950s. The American Vanguard 1 satellite was the very first man-made spacecraft to carry solar panels to store energy to critical power systems in 1958. Going forward, NASA was going to require solar panels of ever-increasing efficiency.

AeroVyronment Pathfinder
Photo: NASA
Why? Well, NASA had some pretty ambitious plans. They'd already successfully landed the Viking series of landers onto the surface of Mars twice. The two landers took full-color images of the red planet's surface while there, a first for mankind. But something profoundly bolder was being planned.

We're talking about long-duration Martian rovers with the ability to do so much more than make breathtaking panoramas. Stuff that needs more than a passable solar panel to keep on going for any extended length of time. Well, if they can keep an aircraft in continuous up to 70,000 feet (21,800 m), there's a good chance they'll work just as well on a Mars rover.

Thus, starting in the late 1970s, NASA contracted the AeroVironment Corporation of Arlington, Virginia, to clandestinely build a UAV concept, initially named "High Altitude Solar" or HALSOL. AeroVironment was founded by a humble engineer from the sleepy NYC satellite city of New Haven, Connecticut.

His name was Paul MacCready. He may not be as well known as the Wright Brothers or Werner Von Braun. But from a certain perspective, he's just as important to the world of EV aircraft as any of those two are to manned air and space flight.

AeroVyronment Pathfinder
Photo: NASA
His idea was simple in principle but endlessly complex in practice. Construct an ultra-lightweight airframe that uses its entire wingspan to generate life and also electricity through its gargantuan array of solar panels. The 98.4 foot (29.5 m) wingspan was packed to the brim with solar cells covering everything but the very brim of the wing. Powering the six propellers in the original design was a set of electric motors.

These motors jetted the HALSOL, as it was still named back then, up to a top speed of an eye-watering 15 miles per hour (24 kph). The first test flights began in June 1983. Although nobody was impressed by its top speed, the enormous amount of lift the lightweight flying wing generates made it perfect for experiments as an atmospheric satellite. An aircraft that can loiter very slowly around a target area to ascertain changes in geology or terrain to gather scientific data.

But where Pathfinder, as it was finally named soon prooved, its bread and butter was pushing the global electrically propelled aircraft record. Maxing out at 71,530 feet (21,800 m) in its original configuration. After a complete overhaul and relaunch as the upgraded Pathfinder Plus, this record was shattered yet again, maxing out at 80,201 feet (24,445 m). An all-time record for solar-powered aircraft, EV aircraft, and even propeller-driven aircraft. The added 44 feet (13m) of wingspan helped break the record, surely.

In 2002, Pathfinder Plus was used to transmit HDTV signals and IMT-2000 wireless communications signal from 65,000 feet (20,000 m), essentially making it the world's highest WiFi hotspot. Today, the record-breaking retired airplane is on display at the Steven F. Udvar-Hazy Center in Chantilly, Virginia. The official annex of the National Air and Space Museum in Washington DC.

AeroVyronment Pathfinder
Photo: NASA
Meanwhile, the NASA Spirit and Opportunity Rovers that used similar solar cell technology to that of Pathfinder went on to explore the Martian surface for the better part of the next two decades. Covering a combined over 30 (48km) miles of the Martian surface in the process. If this was the ultimate goal of Pathfinder, safe to say mission accomplished. Not producing any greenhouse gasses must just be the gravy on top.
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