Navy demonstrates multi-day solar UAS flight

15 hours ago (navair.navy.mil)

The article mentions that this Skydweller UAS completed a 73 hour flight.

Back in 2022 there was a solar powered Airbus Zephyr drone that was tested over the Southwestern US with a flight time of 64 DAYS. I wonder how this new drone is different and how a 73 hour flight is significant in comparison.

Here is an article about the Zephyr Drone and its crash that ended its nearly record-tying flight:

https://simpleflying.com/airbus-zephyr-flight-ends/

Here is a flight replay from adsbexchange showing one day's worth of its flight path where it traced out the Liberty Bell(?) and the shape of the lower 48 at nearly 70,000ft. (Scrolling through its other dates show more playful flight paths)

https://globe.adsbexchange.com/?icao=ae1313&lat=33.419&lon=-...

  • The Skydweller is capable of carrying an ISR (Intelligence/Surveillance/Reconnaissance) equipment load, which is several times heavier than the Zephyr -- not to take away from the Zephyr's accomplishments ("on the shoulders of giants", etc).

    The article mentions "wide-area surveillance"[1], which translates to "a lot of cameras" (FLIR, visible light, etc).

    You also need more solar and more batteries to power all that ISR.

    1. https://en.wikipedia.org/wiki/Wide-area_motion_imagery (eg. GORGON STARE)

  • It looks like that Zephyr drone only weighed about 160lbs and didn't carry any payload. I believe these new Skydweller drones can carry an 800lb payload. Maybe that is the significant difference?

This was envisioned by the movie Interstellar where the opening scene shows them chasing an old autonomous Indian Air Force drone that had been flying for years, ostensibly after that agency ceased to exist. I'm sure it's been in other media as well but that's what comes to mind here.

Anyway, it should be interesting to see where this goes in the future.

  • I am still skeptical it would work out for regular aircraft due to all the moving mechanical parts, not o mention battery charge cycles for night flying.

    But I could definitely see it working for autonomous underwater drones that glide in the water, going up and down by changing their density. Few simple mechanical parts & some project already demonstrated very long endurance.

    • Mechanical failure is usually a probability distribution and with a large enough population, you get outliers.

      https://en.m.wikipedia.org/wiki/Centennial_Light

      “ The Centennial Light is an incandescent light bulb recognized as the oldest known operating light bulb. It was first illuminated in 1901, and has only been turned off a few brief times since.”

    • I’m probably hugely oversimplifying here but let’s say you attach the electric motor directly to the prop, perhaps with some minor gearing, then what’s left in terms of moving parts? Some rudders, right?

Very cool. I've been wondering on the upper limit on this for a while: Indefinite autonomous flight. Upper atmosphere or lower. I think I was inspired by SevenEves' gliders, but in my head, they would be small (er than depicted in the novel, and this article)

  • I think altitude is what would make these valuable. If you can approach LEO and away from standard military tech, they could easily prove refreshable tech platforms.

Did it follow the sun around the world or did it circle around its launch location for three days?

  • Not sure about this one but previous multi day attempt were not tracking the sun. They go really high during day and then use battery and altitude to make it through night

  • To follow the sun it would have had to fly over 1000mph for the whole duration of the flight. So I guess it circled

I wonder what sort of payload it has. Could this conceivably lift a person?

  • Yes. It is indeed based on the Solar Impulse 2, the first manned solar aircraft to circumnavigate the earth.

    https://alert5.com/2025/07/30/converted-solar-impulse-2-airc...

    • You can use 'circumvent' here, but the meaning is a little odd. That's more like heading from Mars to the Sun and finding a way around the Earth to continue to your destination. Usually, people use 'circumnavigate' instead, which is used to describe vehicles (boats, planes, bicycles, etc.) making their way all the way around Earth.

      1 reply →

  • One possible payload would be a fast deploy cellular base station that can loiter over disaster areas to provide connectivity. Backhaul would be via satellite like Starlink or if you have multiple aircraft you can route between them to a place with working connectivity. They could also broadcast FM emergency update info.

    • If you ever dig through Tarana's patents, what you'll come across is more or less what you're describing.

    • Presumably they could also be rented for big commercial outdoor events, too. On a grander scale, maybe these might make a big network like the old Project Loon more feasible, though presumably the things would have to be able to fly high enough to escape most of the weather (and vandals and conspiracy theorists armed with rifles).

That plane is extremely hollow; you can clearly see the deformation because its not extremely rigid. It's some sort of thin high strength fabric over a minimal skeleton.

  • I'm not sure what you are basing that assessment on. Hollowness is a given for an aircraft of it's size, but I can't say I see any signs of it being extremely so. At least from the pictures of the article it is definitely not clear that it would be deforming unusually much.

    Quickly checking the construction is carbon fiber, which is kinda no-brainer.