NEW YORK—Early Saturday morning, in the midst of a round-the-world flight, Solar Impulse 2 made the short hop from Pennsylvania to New York City. After gliding past the Statue of Liberty, it made its way to John F. Kennedy Airport, where it will remain until the weather permits it to start the next leg of its journey. After spending the morning soaking up the sunlight to charge its batteries, the plane was wheeled into one of Kennedy's massive hangars to give the press a chance to meet both it and the pilots who are taking it around the world.

This is the second of the team's solar-powered craft we've been able to see up close, and it's not a radical departure from the earlier one, which had completed a flight across the US by landing at JFK. Solar Impulse 2 is slightly larger and a bit more robust looking than its sister, but the general outlines are quite similar: a four-engined, glider-shaped craft, with most of its upward-facing surfaces covered in solar panels.

Its stats are impressive: the wingspan of a 747 (at 72 meters) at a weight of only 2,300 kilograms. Its maximum speed, however, is only 140km/hr, and it typically flies quite a bit slower than that—the pilots count on finding the appropriate winds to push them along. And while the plane could operate at up to 12,000 meters, its cockpit isn't pressurized, so altitude is limited by its pilots' tolerance.

Many of the same technology partners from last time were on hand, too. We were invited to the press conference by Dassault Systems, which provided software used in the design and validation of the plane. Dassault also tracks every single piece of hardware on the aircraft. Belgian chemical company Solvay provided many of the materials that make up the aircraft itself. The motors that drive the propellers—pilot Bertrand Piccard loves to remind everyone that they're 97 percent efficient—actually come from Schindler, an elevator company. (Schindler's actual elevators are even more efficient than that, as they generate electricity through gravity when they descend.)

Covestro, a polymer company, provided the insulation, while a company called ABB managed the on-board electrical system, which it calls similar to one of the ground-based smart grids it provides.

Piccard and fellow pilot André Borschberg pointed out that all of the hardware inside Solar Impulse 2 is already on the market—there was nothing custom-developed for the aircraft. This is in keeping with the team's motivation for the flight: to raise awareness that clean and renewable technologies are ready and affordable now. It's a message they reiterate every stop they've made so far.

The fact that the technology is all off-the-shelf doesn't mean there's nothing new on the aircraft. But most of the new technology is focused on the part of the system that is stressed to its limit during flights lasting as long as five days: the pilot. The cockpit of Solar Impulse 2 isn't much larger than the original, making it a very cramped space to spend a work week. The Dassault representative noted that one of the challenges in the design phase was figuring out how to provide enough space for the pilots to have an on-board toilet they could use without moving around much.

Autopilot software had to be carefully developed to handle the aircraft's performance, which is very different from most commercial aircraft. And the whole thing had to be certified as safe so that it could be flown over populated urban areas.

John Timmer





John Timmer

John Timmer

John Timmer

John Timmer

John Timmer

John Timmer

John Timmer

John Timmer

John Timmer

We also spoke to Gaëlle Schlup-Ollivier at Nestlé, who showed off (and let us taste) the meals that were developed specifically for the flight. Schlup-Ollivier noted that not only is the cockpit unpressurized—it also lacks climate control. Temperatures can range from -20°C up to 30°C over the course of a day. The pilots also spent about a third of the day above 4,000 meters, with their breathing aided by an oxygen mask.

After adding turbulence on top of the pressure and altitude, nobody has much of an appetite. So meals for that part of the day are focused on fats and sugars to give the pilots a calorie boost. Once they drop down to breathable altitudes, they get more protein-rich meals. Any meal that involves liquid is dehydrated, allowing the pilots to simply use water as needed. And a special pouch was created that generates heat through a chemical reaction with water, helping warm the pilots in the harsh cold.

All of the meals were customized for Piccard or Borschberg's individual tastes. After all, Shlup-Ollivier pointed out, the best meal won't do much good if it doesn't get eaten. And clearly it worked. While we were talking, Piccard came over to go through the various items Schlup-Ollivier had on hand and had praise for several of them.

Of course, both Piccard and Borschberg seem to be inherently positive. With two-thirds of the world behind them, you might think they'd start looking forward to the end of the journey, but both retained an intense focus on the legs to come. The next big hurdle is the Atlantic and the weather conditions it presents. Piccard emphasized that three more flights after that will need to be made in order to return Solar Impulse 2 to its point of origin in Abu Dhabi, and all of them require the same level of preparation. Borschberg, who had flown the plane into JFK, was still enthusing about his close-up with the Statue of Liberty.

From the outside, this positive attitude and the general success of the project make the whole thing seem like a well-oiled machine that has taken all the risk out of the flight. But Borschberg told Ars about an argument with project staff that unfolded via conference call while he was in the cockpit at 20,000 feet. The argument centered on technical problems with the system that kept the pilot from sleeping for more than 20 minutes at a time. The staff threatened to resign if Borschberg didn't turn back to Japan, but he argued that getting the right weather for the five-day flight was a rare event and shouldn't be passed up. Eventually, Borschberg won the day and continued the flight.

Piccard and Borschberg both get to spend a bit of lower-pressure time in New York, waiting for the right conditions to head on. But neither of them seemed able to relax—too many decisions and preparations to be made. And when they catch a break from the flight itself, they're ready to talk to anyone who will listen about the benefits of clean, efficient tech.

Listing image by John Timmer