The Zéphyr: the electric plane that replaces satellites

An experimental solar-electric spy plane, the Airbus Zéphyr S, took off from the Yuma Proving Ground military base in Arizona on June 15, according to military-related website The Drive. And he could still fly.

On its maiden flight in July 2018, the Zéphyr S set a new 26-day long-distance world record approved by the Fédération Aéronautique Internationale.

It remains to be confirmed that the current flight will last even longer and set a new record.

Several versions of the Zephyr were tested by the United States Army and Navy.

The newest, the Zephyr S, achieved flights to an altitude of 76,100 feet, another world record for an electric drone.

That is why Airbus speaks of a HAPS (altitude pseudo-satellite).

Only the famous American spy planes U-2 and SR-71 have reached such heights (see below).

This “pseudo-satellite” has this special feature: It has an exceptionally low weight for a wingspan of 25 meters (82 feet), it weighs only 65 to 75 kilos (143 to 165 lb), depending on the on-board electronics.

Its mylar and carbon fiber wings are fully covered with solar panels that allow it to continuously charge its 24kg lithium-sulphur batteries, about a third of its total weight.

Its fuselage, a thin cylindrical tube, terminates in a bulbous nose that houses its avionics and data acquisition and transmission systems.

The first electric solar drone to reach the stratosphere, the Zéphyr S was designed to fulfill a wide range of military and civilian missions, generally performed by satellites, at an affordable cost: terrestrial and maritime surveillance, reconnaissance, navigation, communications, missile detection , electromagnetic intelligence (SIGINT) and environmental monitoring.

The Zephyr can relay imagery and signaling information to ground commanders at a tiny fraction of the cost of an orbiting military satellite.

The drone uses ultra-miniaturized optical/infrared video sensors to produce real-time, high-resolution images day and night.

It has the ability to collect data over areas covering 1000 km2.

Like a geostationary satellite, but at a thousand times lower altitude (36,000 km versus 26 km), the Zéphyr can fly over a fixed point on the ground for long periods of time. Flying closer to the ground, the Zephyr’s camera can capture images with a resolution of 18 centimeters, while satellites have a resolution of about 30 centimeters.

Zephyrs also offer a distinct advantage over spy satellites in circumpolar orbit, which cross their target areas twice a day.

They circle over their target, providing continuous cover.

These quasi-satellites can even replace destroyed or inoperable satellites. Russia and China are actively developing their anti-satellite capabilities. American and allied orbital observation systems face growing threats.

The Zephyr civilian missions

On the civilian front, Airbus claims its electric high-altitude drone will monitor the planet’s environmental evolution and revolutionize how forest fires and oil spills are managed.

For border security, the Zéphyr S will be able to detect and track people crossing illegally and transmit their data to the authorities in real time.

The Zephyr’s ability to augment or replace satellite systems will be valuable in post-disaster scenarios, particularly when traditional cellular or Internet networks become inoperable. They can also serve as “cellular towers” ​​for cell phones and 5G, providing an alternative to standard towers in areas with poor infrastructure or uneven terrain.

Fly almost unlimited

Airbus engineers are aiming for 100 days non-stop flight and more for the Zéphyr. They’re even considering making landing and takeoff optional. Incredibly, the Zephyr’s solar panels can charge the plane’s batteries enough to keep it aloft almost indefinitely. DARPA, the Pentagon’s advanced research agency, previously developed the Vulture and SolarEagle programs, which aimed to keep an airplane aloft for five years.

Zephyr trials could be launched when the weather is favorable and “parked” in the stratosphere to give users great operational flexibility.

The limitations of the Zephyr

Zephyrs have the advantage of being more adaptable than traditional spy satellites while having much better flight endurance than other drones and other high-altitude spy planes.

The main limitation of the Zephyr is its small payload capacity. The Zephyr S is 30% lighter than its predecessor, the Zephyr 7, but carries 50% more batteries, making room for its operational 5 kg (11 lb) payload. That’s very little compared to the 2000 pounds of Northrop Grumman’s RQ-4 Global Hawk spy drone, the benchmark for military drones.

The Zephyr is much slower and less durable than high-speed jet spy planes, but it makes up for it in endurance. The Zéphyr pulverized the US Air Force’s Global Hawk, which could only fly 35 hours without refueling.

Many technical challenges await the Zephyr. Cosmic rays are a threat to his electronics. Its cruising altitude is well above inclement weather, but it is vulnerable to strong winds and inclement weather during ascent and descent.

Propulsion by solar energy brings with it limitations. Available brightness varies by latitude and date. The tropics offer the most energy: the further away the device is from the equator, the less energy is available in winter. However, this does not prevent him from carrying out his missions in winter as well. It flew in a winter climate for 11 days to show it could function on long winter nights. When the sun goes down, it has to drop to 45,000 feet to conserve energy in the denser air.

A Franco-British invention

The Zéphyr was acquired by the French Airbus in 2013 and developed by the British QinetiQ in the early 2000s. In April 2014, the British Ministry of Defense awarded Airbus a contract for the production and operation of the Zéphyr S. The aircraft were built at Airbus. Factory in Farnborough, UK. Some of the tests conducted by Wyndham Airfield, Australia ended badly. In March 2019, a Zéphyr S crashed due to extreme weather conditions. A second disintegrated in flight in September 2020.


Zephyr T

Photo courtesy of Airbus Defense and Space

Zephyr T

Airbus is currently developing the two-tail Zephyr T, designed to carry larger payloads. It is a larger aircraft with a wingspan of 33 m and heavier, weighing 140 kg. Its payload capacity of 20 kg is four times that of the Zéphyr S.


Takeoff of the Zéphyr S for a test flight in Arizona.

With kind approval

Takeoff of the Zéphyr S for a test flight in Arizona.

Zephyr operators must be very careful when deploying and launching the fragile aircraft. On the ground, its wings bend under its own weight. A couple of men is enough to toss it with your hand while running and carry it over your head. The Zephyr’s first method of deployment was a helium balloon, which propelled it to an altitude of up to 9,000 m (30,000 ft) before release.

The famous spy planes U-2 and SR-71

  • The U-2 is one of the few aircraft to have served the US Air Force for over 50 years. There are 31 operational U-2s left in the USAF. They will get an upgrade that could keep them flying for another 30 years. The U-2 participated in the conflicts in Afghanistan and Iraq and supported several NATO multinational operations. During the Cold War, U-2s conducted spy missions over the Soviet Union, China, Vietnam and Cuba. In 1960, Gary Powers was shot down by a surface-to-air missile in a CIA U-2 over the Soviet Union. During the 1962 missile crisis, a U-2 piloted by Major Rudolf Anderson was also shot down over Cuba. These setbacks prompted the Pentagon to take an interest in developing high-altitude drones. The subsonic U-2 has a range of 11,280 km and can reach 70,000 feet (21,000 meters).

The U-2

Photo archive, AFP

The U-2

  • The SR-71 Blackbird, intended to replace the U-2, could fly at over 3,500 km/h (the fastest plane in the world) at over 25,000 meters. He was retired from the US Air Force in 1998. Lockheed Martin is currently developing a successor, the SR-72, a hypersonic drone for reconnaissance and combat missions. It is partly made with a 3D printer. First flight planned for 2025. The SR-72 would fly at Mach 6 or 7408 km/h.

The Blackbird SR-71

Photo courtesy US Air Force

The Blackbird SR-71

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