Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Solar-powered aircraft flown for nearly three weeks without landing

eandt.theiet.org

Post reply on HN
Print view View original

31–40 of 220 posts

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

#31

Post by rrss »

mkr-hn wrote: post #28
onychomys wrote: post #22

Earlier quoted context omitted.

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?

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?

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

#32

Post by spijdar »

mkr-hn wrote: post #28
onychomys wrote: post #22

Earlier quoted context omitted.

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?

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 the creation/destruction of chemical bonds, and associated movement of electrons.

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

#33

Post by luma »

mkr-hn wrote: post #28
onychomys wrote: post #22

Earlier quoted context omitted.

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?

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 you're being serious. You are technically correct, but also incredibly wrong in suggesting that the increased weight would be substantial enough to impact anything measurable. Depending on the size and capacity of the cell, you might see a difference due to general relativity on the order of nanograms.

see: https://physics.stackexchange.com/questions/34421/does-the-m...

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

#34

Post by Tepix »

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…

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

#36

Post by detritus »

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.

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

#38

Post by Tepix »

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.

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

#39

Post by jermaustin1 »

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?

A water/gravity battery comes to mind. Definitely not the answer you are looking for, but an answer none the less.
Post reply on HN