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

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

#51

Post by kleton »

jthomaslm wrote: post #30
kleton wrote: 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…

What fraction of the power budget do you think will remain for non-propulsion?

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

#52

Post by nosequel »

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 of jet fuel.

The downside is you don't have any fuel to cycle through the computers for cooling and forced air becomes a big problem at high altitude. I'm sure you've thought about it, but what atmosphere do you plan to keep the cabins at?

Good luck on your project! Working on autonomous vehicles like Global Hawk and our DARPA Grand Challenge vehicle was one of the highlights of my career.

- [1] https://en.wikipedia.org/wiki/Northrop_Grumman_RQ-4_Global_H...

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

#53

Post by frontiersummit »

jthomaslm wrote: post #20
hermitcrab wrote: post #5

Was the 24 hour test at 20km? Doesn't it take a lot of battery power to climb to that height? >we then spent 6 years working together on delivery drones at Amazon Prime Air Was that ever a serious endeavour or just a publicity stunt?

The 24 hour test was with a sub-scale prototype at low altitudes. It turns out that testing a small aircraft in the thicker air at these altitudes matches some important physics of the larger aircraft (Reynolds number). Perhaps unexpectedly, climbing to 20km altitude isn’t too large a problem from an energy perspective. In a typical energy cycle, the aircraft has low battery in the morning, so if we launch with a ful…

Just over 20 years ago, a small model aircraft (https://en.wikipedia.org/wiki/The_Spirit_of_Butts%27_Farm) crossed the Atlantic in 39 hours using about a gallon of Naptha as fuel. The same year, the Design-Build-Fly club at my university built an electric aircraft which had some serious endurance and payload capabilities, though I don't remember the details. Keeping a model electric plane aloft for a day is impressive, but how many hobbyists have built something similar by now without any expectation of VC money?

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

#54

Post by H8crilA »

nosequel wrote: post #52

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 do you need to have, voice comms / ADS-B? I guess there's not much of a problem with that given that next to no one flies so high.

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

#55

Post by woodlander87 »

bloopernova wrote: post #33
extraduder_ire wrote: post #24

Earlier quoted context omitted.

I'd guess because it's less prone to get interfered with by wind, more easily controllable, and can stay up longer if battery power lasts overnight. I too would like to see more autonomous hydrogen balloons flying. Even on tethers to get height cheaper than a tower.

I'm not well-read on the technology involved. Is it possible (feasible?) to use a high altitude balloon to get a plane to altitude? You could either detach from the balloon, or use spare solar power to deflate the balloon in case you need it again. Maybe the balloon could help maintain altitude at night.

Perhaps not as high altitude as the stratosphere, but the US was experimenting with deployment and 'landing' of fixed wing aircraft from airships in the 1930s. https://en.wikipedia.org/wiki/USS_Akron

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

#56

Post by jthomaslm »

philipkglass wrote: post #11

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 batte…

Yes, Airbus’s project and team is very cool! What we’re doing shares similarities with Zephyr, but we’re focusing on a lower cost system, and a larger payload which will enable more use cases.

We’re using conventional silicon solar cells, rather than the GaAs cells used by Airbus. We give up some efficiency by doing this, but it keeps costs far lower - which we think is key to iterating quickly, and opening up some of the market use cases.

Similarly, we’re sticking with conventional battery chemistries (Lithium Ion). Battery energy density is by far the biggest driver for this technology - in the past decade we’ve seen huge advancements in battery tech, which is one of the reasons this technology is now possible. As you identify, cycle life is a key challenge and what will limit the aircraft’s endurance.

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

#57

Post by jthomaslm »

pj_mukh wrote: post #10

Wow, 10cm live view for complete situational awareness of forest fires feels like it should be a game changer. Can we make sure someone (if not you guys) fully builds this service on your flights for the fire service?

Wildland forest fires were actually the inspiration for this technology! A year ago Seattle had the worst air quality in the world for a few days, which piqued my interest in the area. Speaking to people in the USFS we learned about the challenges of getting real-time high-resolution data, and realized that an ultra long endurance drone would be a great way to get this.

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

#58

Post by H8crilA »

zeusk wrote: post #49
frontiersummit wrote: post #46

Earlier quoted context omitted.

I'm similarly curious. Designing for a higher stall speed permits smaller wing area, lower drag, and lower weight. The cost is that takeoffs and landings become troublesome.

Could be catapult launched?

Lee waves? Thermals? Cumulonimbus thermals? :)

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

#59

Post by moralestapia »

zeusk wrote: post #49
frontiersummit wrote: post #46

Earlier quoted context omitted.

I'm similarly curious. Designing for a higher stall speed permits smaller wing area, lower drag, and lower weight. The cost is that takeoffs and landings become troublesome.

Could be catapult launched?

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

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

#60

Post by jthomaslm »

bglazer wrote: 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 this technology and I don’t underestimate how difficult it will be to navigate. We certainly have no intention of monitoring civilian populations and haven’t spoken to any police forces about what we’re doing.
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