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

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61–70 of 206 posts

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

#61
post #12

Why go with heavier than air?

Each has merits, but in our evaluation, if you are able to overcome the aircraft design challenges, fixed-wing offers a far more capable platform. The stratosphere has winds that can exceed 100km/h. With balloons, station-keeping is an enormous challenge. We spoke to a lot of people in the Google Loon project, and ultimately this became a defining problem for them. Airships/dirigibles help a bit, but still have to dr…

[deleted]

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

#62
post #49

Earlier quoted context omitted.

Could be catapult launched?

I don't think one could just "throw" something 70k feet up in the air.

Climbing to altitude is the straightforward part. The transition from zero knots to the stall speed of the aircraft (minimum speed at which it can remain airborne) is the tricky bit. Designing for a lower stall speed necessitates wings which produce higher drag (by being larger) which requires more propulsion, which means bigger batteries and motors. So launching from a catapult or rocket or mothership or whatever means a lighter plane.

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

#64

How does the aircraft get to 70k feet? Is it launched from a separate vehicle?

The aircraft is able to climb under its own power. We have a diurnal energy cycle - charging the battery up through the day and deploying battery energy in the night. If we launch in the morning with a full battery, we have a whole day's worth of extra solar power to use to climb up to altitude.

Winds will be a bigger issue than energy when climbing. Up at 20 km (70k ft.) winds are quite calm, but we need to ascend through more turbulent winds as we climb. We’re sizing our MVP around this.

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

#65
Daniel, from RCTESTFLIGHT on YouTube, has a series of videos where he experiments with solar airplanes, which wad really interesting to watch from the standpoint of a RC and electronics hobbyist:

https://youtube.com/playlist?list=PLXvxJNOIXBsM83XxVG7tDUmql...

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

#66
Looks amazing! So many potential applications.

Does it use PX4, Ardupilot, a customized version of these, or custom firmware? What sort of MCUs and ground station? Are you using an all-in-one electronics sort of unit, or distributed systems (eg CAN nodes, LRUs or w/e) How are you solving the RF communications, ie what sort of range are you getting, and what frequency/transmitters/power level? What sort of range do you expect? It seems like it would be unlimited, other than the RF comms.

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

#67
post #19

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…

This is a concern for us. As with many disruptive technical advancements (e.g. in Nuclear or AI), there are many ways our technology can be used - both good and bad. It's important to us that what we do is ethical - that means supporting and pursuing use cases with huge positive societal value like rural connectivity or wildfire monitoring. With that said, there are definitely ethically-questionable use cases for thi…

I'm glad to hear that, I hope you stick to those principles if the police or military come calling. They have deep pockets and your investors will want their 100x.

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

#68
post #49

Earlier quoted context omitted.

Could be catapult launched?

I don't think one could just "throw" something 70k feet up in the air.

Spinlaunch would disgree but here the trouble is getting off the ground; Take-off is the most demanding phase of flight in terms of propulsion demand.

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

#69
post #54

This looks like a great project. Global Hawk [1] has all the current autonomous aircraft records (longest autonomous flight, etc.). Obviously you can't go as fast as Global Hawk, but one great thing is you don't have to worry about all the issues around fuel freezing. To at least some of our surprise, 60k+ feet around the equator was much colder than 60k+ feet around Edwards AFB and we approached the freezing limits…

That record is only ~23 hours because it is a record within a very heavy weight class (14,000 kg+). There are many crafts similar to the one presented here that have done multi-day flights. This one can fly for months at a time: https://www.airbus.com/en/products-services/defence/uas/uas-... . And you can track it real time via ADS-B when it's up there! Speaking of ADS-B, how do you get airspace clearance? And what d…

Clearance was really hard back in 2002 when Global Hawk was coming out of test phase and into production. There wasn't another autonomous plane, so it was the first to do what it was trying to do. That wasn't really my field, but I know it was truly painful to get FAA approval for lots of things. They were really concerned with some autonomous plane flying over cities, so most of our long flights avoided flying over populations. That was pretty easy in CONUS, but flying into Germany for the Euro Hawk was super painful apparently. There isn't exactly un-populated areas around there. Regarding voice, yes there was someone in the ground station on comms, and to any other airplane, they appeared to be coming from the aircraft and not the ground. Altitude makes a lot of things easier, plus the military has a lot of restricted airspace. I honestly have no idea how a civilian autonomous aircraft will pull it off. I'm sure a lot has changed in 20-ish years, so maybe it is not a painful now. With the FAA, I'm sure it'll still be a headache.

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

#70
post #14

Very cool. I used to dream of this stuff when I was younger. Reminds me of Atlantik Solar: https://www.atlantiksolar.ethz.ch/ . Hasn't been updated in a while, but focused more on low-altitude autonomous survey missions.

Atlantik Solar was a very cool project, read a lot of their research - count me as a fan :)
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