Comment on High Altitude Solar Cruise
Dasus@lemmy.world 2 weeks agoBasically you’re making a plane so huge that the batteries you need will weigh a fuckton, increasing weight and need for power even more.
What’s the wing setup for such an incredible massive plane, and what kind of battery / solar do you expect to be available?
I’d like to remind you that the larger the objects volume, the smaller the surface area in relation. Like a mouse has vastly more surface compared to it’s size than an elephant or a blue whale does.
What I mean by this is that the larger you make the plane, the less surface area you’ll have for solar. Unless you add more materials and make it even larger.
I would like to see a thing such as you describe, but it doesn’t sound too plausible.
Blimps don’t need to use helium, btw. Technically you could have an empty blimp. (void is lighter than air, duh) It’d just be quite the engineering challenge to have it not implode at the sizes required.
keepthepace@slrpnk.net 2 weeks ago
Just to be clear “eternal planes” exist today. They use solar during the day, batteries during the night. Unmanned they last forever and a 2-person plane like this already exists now.
What I am proposing is science fiction, but honestly the most straightforward and boring kind: I am proposing that from this current state, we will continue, percent by percent, improve efficiencies in batteries, motors, solar panels, we will improve material resistance and aeronautic designs.
Dasus@lemmy.world 2 weeks ago
Just to be clear, the physical law of the surface area being smaller in relation to the volume in bigger objects still exists, and you’re proposing a plane with a greenhouse and a swimming pool.
keepthepace@slrpnk.net 2 weeks ago
Yes and? You do know that current cargo planes are able to lift 250 tons without violating the laws of physics?
Dasus@lemmy.world 2 weeks ago
Oh yes, cargo planes which don’t have pools or greenhouses and which guzzle tons of fuel to power their huge engines?
Does the surface area of those planes determine how much energy they can get? Or is it the exceedingly high energy fuel which they pipe in to a tank inside the plane?
So you expect cargo planes to increase in size so much they’re not just lugging cargo, but also have greenhouses and swimming pools (and that’s ignoring the problems and pure stupidity of having a pool on a plane), but you expect solar to become so efficient it can actually deliver more energy from surface area of an aircraft than you can currently by pumping a metric ton of high-grade fuel in a minute?
The An-255 Mriya has six engines producing ~54,000kW each, meaning a total output ~324 000 kW.
The solar plane you mention, the Solar Impulse 2, has four engines producing 13.5 kW each for a total output of 54kW.
You can see the contrast, right?
I hope I would be wrong in this. But I’m not.
I think one would need something like a nuclear powered plane for shit like that. Which wouldn’t necessarily be a bad idea, honestly. I think we should look into that sort of tech because it would also work at the bottom of the ocean and it could power craft that could explore Venus.
Now don’t get me wrong I’m no nuclear shill, I think we should definitely power most things with renewables. And even planes, sure. But if you honestly want a plane which is large and stable enough to have a pool and a greenhouse, I don’t think we’re going to achieve that via solar. At least not directly. Perhaps planes like that could be powered via extremely high powered lasers from the ground and/or moon.
But like mathematically… roughly 1000 watts or 1 kW of energy comes from the Sun on a clear day for every m2 of ground. In space it’s like ~1300 at this distance. On a cloudy day way less than 1000. But well go with the 1kW/m2.
If we assume that this plane of yours needs to be able to capture the amount of power it uses and that it is not even that big, just has similar engines to the An-225, then you’d need a surface area of 324 000 m2.
The wing surface area of an A320 is ~100m2, so you’d “only” need 3240 of those to have enough area on the plane to have 100% efficient solar panels be able to produce the peak power of the An-255. Ofc you wouldn’t be flying with peak power all the time, and flying above clouds would mean good sun to panels.
The record for efficiency for solar panels in a laboratory setting is 47%. Those aren’t commercially available. Commercially available ones are currently around 22%.
Light clouds cover reduces solar panels to 75-80% output. Heavy clouds can reduce it to 10%.
And unless you’re planning to fly in one direction only and only during certain times, you’ll have to consider that you’re not always in the sun, nights exist.
So double everything assuming half of all time is night.
Then assume 22% efficiency.
Then keep in mind all clouds can’t be avoided so let’s say 90% output.
So it’s not 3240x the A320 surface area you need, but 6480 because nights, but then only ~22% efficiency for recharging so it’s ~30 000 times the surface area of an A320. Oh except cloud coverage. So ~33 333.33333 *(repeating of course) times the surface area of an A320.
And that’s why I find your suggestion improbable.
It’s hopeful and I’d like for you to be right. But I don’t think you are. Sorry.
If we could manage a bit of societal change so as the se rich motherfuckers weren’t stealing everything, I think we might actually speed the rate of technological growth by a metric fuckton.
But with this speed and looking at these facts? I just can’t believe in your dream, however nice it sounds.