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Re:Launch HN: Radical (YC W23) – Autonomous high-altitude so... by jthomaslm on Monday October 16, 2023 @12:59PM (#37902796)
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 full battery charge we have plenty of extra energy to climb up to altitude.

Prime Air - definitely a serious project, but I’m sure Amazon didn’t hesitate in milking the PR! Making a reliable drone delivery service at Amazon scales certainly isn’t easy. That team is still going strong and I’m sure we’ll see more from them as they ramp up commercial deliveries.

Re:Launch HN: Radical (YC W23) – Autonomous high-altitude so... by hermitcrab on Monday October 16, 2023 @01:07PM (#37902914)
>The 24 hour test was with a sub-scale prototype at low altitudes.

That's fine, but I think you need to make that clear or some people might think you aren't being straight.

Re:Launch HN: Radical (YC W23) – Autonomous high-altitude so... by frontiersummit on Monday October 16, 2023 @01:55PM (#37903592)
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 so... by hermitcrab on Monday October 16, 2023 @03:02PM (#37904561)
Impressive. Did it rotate the propellor the whole 38.9 hours on 1 gallon of fuel?