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Solar-powered aircraft flown for nearly three weeks without landing

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Re: Solar-powered aircraft flown for nearly three weeks without landing

#51

Post by jcims »

onychomys wrote: post #22
gusgordon wrote: post #13

For those curious about the physics of these aircraft, here's an analysis I did of the same concept. The goal is to determine the smallest aircraft configuration that can indefinitely sustain flight: https://github.com/gusgordon/atmospheric_satellite#readme

Is there a reason you optimized the amount of starting energy in the battery? I know basically nothing about how solar power works, but surely you'd just fill the battery up to 100% with an extension cord on the ground before launching it?

Maybe it helps surface how much charge is required to climb to altitude vs how much charge is required to sustain it? This may also help surface how much of a buffer you may have in takeoff time in order to survive night. E.g. if you require 100% charge then it's likely you have to take off at a fairly specific time of day.

Re: Solar-powered aircraft flown for nearly three weeks without landing

#52

Post by tpmx »

Tepix wrote: post #38
tpmx wrote: post #23

Probably/unfortunately not really a Starlink competitor, right? They don't specify the "cruising" altitude, but I assume it's ~10 kilometers at most, probably less? Airbus would need quite a few of these in order to build a global internet connectivity service then. Edit: https://en.wikipedia.org/wiki/Airbus_Zephyr says ~20 km. Starlink sats (will) operate at ~540-570 km: https://spaceflightnow.com/2021/04/29/spacex-…

These planes can compete with Starlink in certain scenarios, for example you can launch them in the event of floods that knock out the regular telecommunications infrastructure.

With Starlink soon having ~global coverage, why bother transporting, launching and servicing these aircraft for a one time thing? I don't see the benefit. Will also be really hard to reach low prices for end user terminals with this approach.

Very high quality visual/signals surveillance seems like a much more obvious market fit.

Re: Solar-powered aircraft flown for nearly three weeks without landing

#54

Post by jjcm »

Tepix wrote: post #34
stareatgoats wrote: post #24

This is great and points to how solar in some cases already can facilitate continuous operation without the need for refueling of planes, boats, cars, you name it. Expect this to grow as battery and solar cell tech develops further. My favorites atm are the yachts that are capable of sailing just about anywhere in the world without a drop of fuel. The price is prohibitive, but considering that you might not need a ho…

Why wouldn't you use the wind energy also? It's a lot of fun, readily available and a lot cheaper…

From the images on the site it looks like it deploys a sailing kite in addition to the solar powered engines.

Re: Solar-powered aircraft flown for nearly three weeks without landing

#55

Post by njovin »

JCM9 wrote: post #40

In 1958 two guys flew a Cessna 172 nonstop for 64 days without landing. They refueled mid-air via a truck that drove under them during a low pass.

I had never heard of this record until now. Cross-country flying in small planes like this can be incredibly tedious and the refueling sounds very dangerous. I can't imagine doing it for this long. Apparently, neither can the guy who did it:

> When asked by a reporter if he would ever replicate the stunt, Cook replied: “Next time I feel in the mood to fly endurance, I’m going to lock myself in a garbage can with the vacuum cleaner running, and have Bob serve me T-bone steaks chopped up in a thermos bottle. That is, until my psychiatrist opens for business in the morning.”

Source: https://www.airspacemag.com/daily-planet/airborne-for-64-day...

Re: Solar-powered aircraft flown for nearly three weeks without landing

#56

Post by Retric »

Tepix wrote: post #34
stareatgoats wrote: post #24

This is great and points to how solar in some cases already can facilitate continuous operation without the need for refueling of planes, boats, cars, you name it. Expect this to grow as battery and solar cell tech develops further. My favorites atm are the yachts that are capable of sailing just about anywhere in the world without a drop of fuel. The price is prohibitive, but considering that you might not need a ho…

Why wouldn't you use the wind energy also? It's a lot of fun, readily available and a lot cheaper…

Sails have several major downsides, most notably they take up a lot of deck space and cause a boat to tilt to the side. If you’re regularly sailing long distances it’s much faster but top speed isn’t that big of a deal when your living on the boat full time.

Other options like kites and wind turbines can work well but they all all significant upfront costs as well as ongoing maintenance issues. Spending that same money on a bigger boat gets you much more space, and of course a generator can give you redundancy or higher top speeds.

Re: Solar-powered aircraft flown for nearly three weeks without landing

#57

Post by luma »

rrss wrote: post #31
mkr-hn wrote: post #28

Earlier quoted context omitted.

Batteries are heavier when fully charged. Takeoff weight matters. It's not much heavier, but it might be enough to affect things at this scale. edit: remember the context. This is about an abstract optimization to find the minimum viable aircraft.

what kind of batteries are meaningfully heavier when charged? are you just talking about like E/c^2?

Gas tanks :D

Re: Solar-powered aircraft flown for nearly three weeks without landing

#58

Post by hodgesrm »

JCM9 wrote: post #40

In 1958 two guys flew a Cessna 172 nonstop for 64 days without landing. They refueled mid-air via a truck that drove under them during a low pass.

Good Lord, what an adventure! Thank you for posting!! I had no idea about this flight.

Here's an account that popped up on Google.

https://www.aopa.org/news-and-media/all-news/2008/march/01/e...

Re: Solar-powered aircraft flown for nearly three weeks without landing

#59

Post by runarberg »

detritus wrote: post #36
GhostVII wrote: post #26

What's the benefit over something like a weather balloon? Pretty interesting thought, tape a few hundred micro SD cards to it and you've got some impressive bandwidth.

You can tell this where to go - weather balloons are utterly beholden to the whim of wind patterns.

I thought that you could somewhat control a balloon by using different wind patterns in different elevations.

https://www.youtube.com/watch?v=NvJ2Ei8K2DI

Re: Solar-powered aircraft flown for nearly three weeks without landing

#60

Post by btilly »

spijdar wrote: post #32
mkr-hn wrote: post #28

Earlier quoted context omitted.

Batteries are heavier when fully charged. Takeoff weight matters. It's not much heavier, but it might be enough to affect things at this scale. edit: remember the context. This is about an abstract optimization to find the minimum viable aircraft.

I can't tell if this is satire or not, but taken in good faith, how? A fully charged battery would necessarily have more mass than a fully depleted battery, but the difference should be so tiny as to be immeasurable. Or am I wrong? We're essentially talking about the sum weight of a bunch of electrons, which are extremely light. There's no other exchange of matter going on when charging/discharging a battery, just th…

A battery doesn't have a static charge. When it discharges, electrons move from one side to the other, then back through the batter, and you modify which atoms have which elections. But it continues to have no static charge.

However it has less potential energy. And therefore you change mass by the mass associated with that potential energy.

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