Almost orbital, solar-powered drone offered as “atmospheric satellite”

A model of the Solara 50, Titan Aerospace's commercial "atmospheric satellite," hangs above the company's booth at the AUVSI Unmanned Systems conference booth.

WASHINGTON—At the AUVSI Unmanned Systems conference, New Mexico-based startup Titan Aerospace unveiled the company's prototypes for "atmospheric satellites"—autonomous unmanned aircraft powered purely by solar energy and capable of staying aloft at high altitude for up to five years. The first commercially manufactured long-endurance solar drone, the Solara 50, is under construction now and is expected to fly next year. A bigger drone, the Solara 60, will soon follow.

While solar-powered flight has been a reality since the early 1980s, Titan is the first company to work on commercially manufacturing solar-powered drones. And unlike some of the prototypes that have been flown by the established players in the aerospace and unmanned systems field, the Solara drones are based on well-worn technologies and simplicity in design.

If successful, Titan could change the economics of businesses that have previously depended on low-orbit satellites and allow for a persistent coverage closer to what satellites in geostationary orbit provide.

Solar-powered flight has been a reality since AeroVironment took the lessons from the human-powered aircraft Gossamer Albatross—which flew across the English Channel in 1979—and applied them in the Gossamer Penguin and Solar Challenger aircraft in the early 1980s. But complexity and durability issues have dogged most efforts to create the holy grail of solar aircraft—a drone that can stay aloft indefinitely.

AeroVironment has built a number of solar-powered aircraft for the government, including the Helios prototype—a giant drone with a wingspan of 247 feet powered by solar panels and hydrogen fuel cells. The Helios crashed off of Hawaii in 2003 when it suffered structural failure due to turbulence.

The early success of Helios partially inspired the Defense Advanced Research Projects Agency (DARPA) and Boeing's "Vulture" program in 2008, an effort to create a drone that could spend up to five years on station at 60,000 to 90,000 feet with a thousand-pound payload. Qinetq's Zephyr, one of the program's competitors, flew for 336 hours and 22 minutes, setting the endurance record for unmanned aircraft—but it set the record after DARPA cut the funding for the Boeing contract and reduced the program's scope to work on solar cells and energy storage systems.

That didn't end the Defense Department's appetite for long-flying drones. But the alternative paths chosen so far haven’t paid off. Another AeroVironment aircraft, the Global Observer—a purely hydrogen-powered drone with a 70-foot wingspan designed for week-long missions—crashed in 2011, resulting in the termination of the program by the Pentagon. Boeing has its own hydrogen-powered, long-endurance drone, the Phantom Eye, in development; so far its longest flight has been just over two hours.

A model of Boeing's Phantom Eye at Boeing's AUVSA conference booth.

Titan's aircraft plans are more modest and much more ambitious at the same time. Solara 50 will have a payload of just 70 pounds—though depending on the time of year and location of the flight, longer daylight hours could sustain flights with heavier payloads. The next design, the Solara 60, will carry up to 250 pounds. Instead of using hydrogen fuel cells, the Solara aircraft use batteries charged from solar panels to power flight at night and provide about 100 watts of power to the aircraft's payload, as well.

The Solara 50 has a 50 m (164 feet) wingspan. The upper surfaces of its wings and tail are packed with over 3,000 photovoltaic cells capable of generating up to 7 kilowatts. It is launched by catapult and can land (when it has to) by skidding on its Kevlar-coated underside. Unlike the giant flying-wing configurations of the Helios and Zephyr, which had large numbers of propellers, the Solara has a single, high-efficiency motor.

In theory, a solar-powered drone capable of withstanding long flights at high altitude—in what Titan executives call the "sweet spot" in the Earth's atmosphere between 60,000 and 70,000 feet, above nearly all weather patterns in a zone where winds are typically less than 5 knots (5.75 miles/hour)—would be able to perform tasks usually reserved for satellites at a much lower cost.

For example, during a presentation by Titan at AVUSA, a company spokesperson compared using a satellite for multispectral Earth imagery—say, like Landsat's—to using an atmospheric satellite. A drone could be put up quickly, for much less initial capital. At the same time, it would provide targeted imagery at a cost of less than $5 per square kilometer—versus $35 per square kilometer from a satellite—while still offering the large area of coverage of a satellite.

Enlarge / Artist's rendering of Solara 50 at high altitude. Enlarge / The coverage area of a Solara 50, superimposed over New York.

As a communications relay, the Solara offers about an 18-mile radius of coverage—easily covering all of New York City's five boroughs, as shown in the map above. A "constellation" of Solara craft could create a persistent communication network for disaster relief efforts or could provide long-term services.

Titan already has customer reservations for the first three of its Solara drones, two of which are intended to serve as communications relays (though the customer has not been identified). The first will be delivered in February, with manufacturing ramping up for monthly delivery starting in April.

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Inside the solar-powered plane that crossed the US

A view out to the end of the wing, which cants upward slightly. The wing supports a total of four engines, and is covered in solar panels.

Three years ago, as I was in Switzerland to visit the Large Hadron Collider, a cousin of mine mentioned that they were testing a solar-powered plane at the airfield near his home in Lausanne. If a lightweight, human-powered plane managed to cross the English Channel, a solar-powered craft seemed like an obvious extension–in fact, the same team later crossed the channel in a solar aircraft. Whatever the Swiss were up to, it didn't strike me as that big a step. But with the arrival of that same aircraft in New York City last week, I got a much better sense of what's going on.

In the intervening years, Solar Impulse proved that it WAS a bit more than some solar panels slapped onto a lightweight design. It managed to take off without any fuel and complete a flight that lasted more than 24 hours, and it later successfully flew from Europe to North Africa. Its arrival in New York City (see a gallery here) was the final leg in a flight that started over the Pacific Ocean near San Francisco. Ultimately, the aircraft is just a testbed for what will eventually be the first flight around the world to be performed without any fuel.

Despite its enormous wingspan (over 63 meters, or 208 feet), Solar Impulse is a relative lightweight, tipping the scales at 1,600kg (3,500lbs). Its basic shape is that of a glider: a long, extensive wing to provide lift and a narrow body to minimize wind resistance. In fact, it's part of the normal flight plan to use it as a glider for several hours (more on that below); nevertheless, it does have four engines, each rated at 10 horsepower, and these are capable of driving the propellers at 400rpm.

The huge wing also serves another purpose: hosting an enormous array of solar cells. Rather than using the most efficient technology out there, Solar Impulse relies on some of the thinnest and lightest-weight silicon photovoltaics. The particular cells in use on the plane come from SunPower and are only 135 microns thick. Between the wing and the tail, there are approximately 200 square meters of photovoltaic hardware, far more than is needed to drive the engines. That's because the excess is sent into batteries.

Even using lightweight lithium polymer material, the batteries account for about a quarter of the plane's mass. All told, they can store nearly 100kWhrs of power, and they're part of the key to the plane's 24-hour endurance. But only part. During the peak hours of sunlight, the aircraft is able to both charge its batteries and climb up to its peak altitude of about 9,000m (30,000 feet). Once the sun is no longer providing sufficient power, the pilots can just shut off the engines and glide for several hours before switching to battery power. With careful management, Solar Impulse will still be over 1000m above the ground by the time power starts coming up the next day. Using this technique, the team has set a record by staying aloft for 26 hours.

In the same way that the aircraft is both big and small, the project as a whole both is and isn't about the future. Pilots Bertrand Piccard and André Borschberg made it clear that the project's intended message is that the sort of technology needed to get a solar-powered aircraft like Solar Impulse off the ground is a reality now. Everything that makes the plane work—the solar panels, the batteries, the engines, the lightweight polymers, and insulation—is being made and sold profitably, often by the companies that are now sponsoring Solar Impulse.

That doesn't necessarily mean they were ready-for-use in an aircraft like Solar Impulse. The initial work on the plane was done at the École Polytechnique Fédérale de Lausanne, with engineering work performed by the Solar Impulse team itself. Once that was done, many of the companies had to determine whether they offered, or could adapt, existing products to fit the design's specifications. A spokesman for the chemical giant, Solvay, for example, said his company undertook 50 research projects in response to the Solar Impulse design; about half worked out.

In any case, Piccard argues that these technologies are exactly what we need to make our existing standard of living sustainable. In his view, you can't adopt them in pieces; they have to be part of an integrated package, much like Solar Impulse itself. "To put solar power on a house with single glazed windows and no insulation is foolish" Piccard said at his New York press conference. "Make the house energy-efficient first, and then it can run on only solar power." To him, Solar Impulse is a flying advertisement for everything that efficient and renewable technology can already accomplish.

That said, the project is also meant to build interest for the next big step, a planned around-the-world flight tentatively being targeted for 2015. As Borschberg put it, the current plane is already capable of flying around the world. Previous flights have demonstrated its ability to sustain 24 hour flights. "The weak link is the pilot," Borschberg said. "The pilot is not sustainable yet." Right now, the pilot can grab some snacks while in the cockpit, but there's not a lot of room for anything else. Adding a second pilot probably isn't an option. Beyond the weight of the pilot, they'd need oxygen, food, water, a parachute, and more. Even in its current configuration, Borschberg estimated that the pilot adds about 225kg to the aircraft, which only weighs 1,600kg to start with.

So, the current plan is to build a larger aircraft, one that will allow the pilot to move around and sleep. They're still working on understanding whether it will make sense to carry oxygen and water, or if those can be efficiently recycled on-board. In any case, building a larger plane will clearly need some sponsors and backers, and part of the goal of the trip was undoubtedly to provide them with a demonstration of what they'd be backing.

This trip didn't go entirely smoothly, making it a learning experience for future efforts. The initial leg started from California's Moffett Field where Piccard took Solar Impulse out toward the Pacific for what he thought would be a simple photo-op flight over the Golden Gate Bridge. But the updrafts over the coastal hills were so intense that he ended up having to shut the engines off. Even then, he climbed well above his intended flight plan and had to ask the San Francisco Airport to reroute commercial traffic around him.

Borschberg ended up at the wheel when the landing in Dallas was complicated by headwinds that roughly matched the forward speed of the aircraft. The landing approach required that they face the aircraft into the wind and then drift sideways toward the airport before dropping low enough that the wind speed tailed off. He was also at the controls when some of the wing fabric tore off on the flight to Kennedy Airport in New York City. He took it philosophically, saying, "if I have to bail out, it'll be an interesting experience; if I land in JFK, it will be an interesting experience." Fortunately, the plane continued despite the tear, although it did have to land ahead of its planned arrival.

The project is focused on solar-powered flight, but the team hasn't been focused on promoting that as a future anybody will enjoy. It makes sense, given that the Sun doesn't provide light in a concentrated enough form to ever really propel anything substantial at a decent speed. But the project does make a compelling case: efficient, renewable technology has reached an impressive level of maturity. A maturity that just might take it around the world.

View the original article here

Inside the solar-powered plane that crossed the US

A view out to the end of the wing, which cants upward slightly. The wing supports a total of four engines, and is covered in solar panels.

Three years ago, as I was in Switzerland to visit the Large Hadron Collider, a cousin of mine mentioned that they were testing a solar-powered plane at the airfield near his home in Lausanne. If a lightweight, human-powered plane managed to cross the English Channel, a solar-powered craft seemed like an obvious extension–in fact, the same team later crossed the channel in a solar aircraft. Whatever the Swiss were up to, it didn't strike me as that big a step. But with the arrival of that same aircraft in New York City last week, I got a much better sense of what's going on.

In the intervening years, Solar Impulse proved that it WAS a bit more than some solar panels slapped onto a lightweight design. It managed to take off without any fuel and complete a flight that lasted more than 24 hours, and it later successfully flew from Europe to North Africa. Its arrival in New York City (see a gallery here) was the final leg in a flight that started over the Pacific Ocean near San Francisco. Ultimately, the aircraft is just a testbed for what will eventually be the first flight around the world to be performed without any fuel.

Despite its enormous wingspan (over 63 meters, or 208 feet), Solar Impulse is a relative lightweight, tipping the scales at 1,600kg (3,500lbs). Its basic shape is that of a glider: a long, extensive wing to provide lift and a narrow body to minimize wind resistance. In fact, it's part of the normal flight plan to use it as a glider for several hours (more on that below); nevertheless, it does have four engines, each rated at 10 horsepower, and these are capable of driving the propellers at 400rpm.

The huge wing also serves another purpose: hosting an enormous array of solar cells. Rather than using the most efficient technology out there, Solar Impulse relies on some of the thinnest and lightest-weight silicon photovoltaics. The particular cells in use on the plane come from SunPower and are only 135 microns thick. Between the wing and the tail, there are approximately 200 square meters of photovoltaic hardware, far more than is needed to drive the engines. That's because the excess is sent into batteries.

Even using lightweight lithium polymer material, the batteries account for about a quarter of the plane's mass. All told, they can store nearly 100kWhrs of power, and they're part of the key to the plane's 24-hour endurance. But only part. During the peak hours of sunlight, the aircraft is able to both charge its batteries and climb up to its peak altitude of about 9,000m (30,000 feet). Once the sun is no longer providing sufficient power, the pilots can just shut off the engines and glide for several hours before switching to battery power. With careful management, Solar Impulse will still be over 1000m above the ground by the time power starts coming up the next day. Using this technique, the team has set a record by staying aloft for 26 hours.

In the same way that the aircraft is both big and small, the project as a whole both is and isn't about the future. Pilots Bertrand Piccard and André Borschberg made it clear that the project's intended message is that the sort of technology needed to get a solar-powered aircraft like Solar Impulse off the ground is a reality now. Everything that makes the plane work—the solar panels, the batteries, the engines, the lightweight polymers, and insulation—is being made and sold profitably, often by the companies that are now sponsoring Solar Impulse.

That doesn't necessarily mean they were ready-for-use in an aircraft like Solar Impulse. The plane's design and construction was done at the École Polytechnique Fédérale de Lausanne, and then many of the companies had to determine whether they offered, or could adapt, existing products to fit the design's specifications. A spokesman for the chemical giant, Solvay, for example, said his company undertook 50 research projects in response to the Solar Impulse design; about half worked out.

In any case, Piccard argues that these technologies are exactly what we need to make our existing standard of living sustainable. In his view, you can't adopt them in pieces; they have to be part of an integrated package, much like Solar Impulse itself. "To put solar power on a house with single glazed windows and no insulation is foolish" Piccard said at his New York press conference. "Make the house energy-efficient first, and then it can run on only solar power." To him, Solar Impulse is a flying advertisement for everything that efficient and renewable technology can already accomplish.

That said, the project is also meant to build interest for the next big step, a planned around-the-world flight tentatively being targeted for 2015. As Borschberg put it, the current plane is already capable of flying around the world. Previous flights have demonstrated its ability to sustain 24 hour flights. "The weak link is the pilot," Borschberg said. "The pilot is not sustainable yet." Right now, the pilot can grab some snacks while in the cockpit, but there's not a lot of room for anything else. Adding a second pilot probably isn't an option. Beyond the weight of the pilot, they'd need oxygen, food, water, a parachute, and more. Even in its current configuration, Borschberg estimated that the pilot adds about 225kg to the aircraft, which only weighs 1,600kg to start with.

So, the current plan is to build a larger aircraft, one that will allow the pilot to move around and sleep. They're still working on understanding whether it will make sense to carry oxygen and water, or if those can be efficiently recycled on-board. In any case, building a larger plane will clearly need some sponsors and backers, and part of the goal of the trip was undoubtedly to provide them with a demonstration of what they'd be backing.

This trip didn't go entirely smoothly, making it a learning experience for future efforts. The initial leg started from California's Moffett Field where Piccard took Solar Impulse out toward the Pacific for what he thought would be a simple photo-op flight over the Golden Gate Bridge. But the updrafts over the coastal hills were so intense that he ended up having to shut the engines off. Even then, he climbed well above his intended flight plan and had to ask the San Francisco Airport to reroute commercial traffic around him.

Borschberg ended up at the wheel when the landing in Dallas was complicated by headwinds that roughly matched the forward speed of the aircraft. The landing approach required that they face the aircraft into the wind and then drift sideways toward the airport before dropping low enough that the wind speed tailed off. He was also at the controls when some of the wing fabric tore off on the flight to Kennedy Airport in New York City. He took it philosophically, saying, "if I have to bail out, it'll be an interesting experience; if I land in JFK, it will be an interesting experience." Fortunately, the plane continued despite the tear, although it did have to land ahead of its planned arrival.

The project is focused on solar-powered flight, but the team hasn't been focused on promoting that as a future anybody will enjoy. It makes sense, given that the Sun doesn't provide light in a concentrated enough form to ever really propel anything substantial at a decent speed. But the project does make a compelling case: efficient, renewable technology has reached an impressive level of maturity. A maturity that just might take it around the world.

View the original article here