Launch HN: Radical (YC W23) – Autonomous high-altitude solar aircraft

Very interesting! This sounds a lot like the more recent iterations of the Airbus Zephyr: https://en.wikipedia.org/wiki/Airbus_Zephyr

I don't know how much you can share, but I'm curious about the solar and battery system.

Are you using silicon cells, multi-junction cells, or something else?

What sort of battery chemistry do you use? It seems like deep battery cycling is a must to keep weight under control, but battery degradation is probably the limiting factor for mission duration. The low temperature in the stratosphere also seems more challenging than what terrestrial vehicles deal with.

Very cool idea. As far as applications, I love the idea of this being a lower cost / higher resolution version of satellite imaging, think Ororatec, Planet, Spire etc.

This sounds like military technology of the kind that e.g. Ukraine would currently like a few samples of. Or at least, dual-use.

There is definitely some market overlap in wireless telecommunications. But there are some distinct differences with satellite services. One big one is that our aircraft isn’t in orbit, so it’s much easier for us to provide targeted coverage over a specific area without needing a full constellation. Flying at 20 km also puts us much closer to users which makes high-speed direct-to-device service (5G) a lot easier.

In terms of coverage, from that altitude, we have good line of sight coverage over large areas. Obviously, satellites can cover wider areas, but it turns out that in most suburban/rural settings the ground footprint becomes limited by the population density and bandwidth available - so the larger satellite footprint is only really useful in extremely remote locations.

Do you have any ethical concerns about the use of your technology for surveillance of civilian populations?

That’s the obvious use case for this technology, right? Cheaper and more easily retargetable than satellites. Longer duration, quieter, and more resilient than manned aircraft, but not fast or maneuverable enough to survive in contested airspace.

So that leaves large area, long term surveillance in uncontested conditions as the prime use case.

Sounds an awful lot like cops or an occupying force putting a fleet of these up to indefinitely track all movement or signals over entire neighborhoods or cities. Do you plan to market and sell your technology for this use?