Comment on High Altitude Solar Cruise
Dasus@lemmy.world 2 weeks ago“scifi setting, honey”
Oh fuck off.
As soon as I bring in hard math you start crying “lol I was just joking”, because you never actually thought about the viability of anything you were saying.
You disregard the space required for a greenhouse, and you disregard the physics of flying, proposing a pool.
In a blimp, sure. In a plane? Have you even thought about the amount of lift needed? No ofc you haven’t.
I am proposing a slow vehicles, with a fairly big lift due to its large wings so probably able to fly at a much lower speed, generating far less drag, drag being the main lower bound for the thrust needs.
All of that is utterly utterly ridiculous.
It doesn’t really translate into kW and this is a huge oversimplification but as a wild guesstimate, I’d say the an255 needs some 40 000 to 120 000 kW for sustained flight in fair weather.
Even when you’re talking “scifi setting, honey” you’re not gonna change the laws of physics or how much energy the sun is producing, just the tech. So even if you have 100% efficient engines with 100% efficient solar panels, you’d still need at least 40 000 - 150 000 m2 as a surface area, at minimum for fair weather sustained flight. (That’s 7-26 handegg fields for our American friends)
No offense, but I don’t think you’re a professional aviator.
keepthepace@slrpnk.net 2 weeks ago
Let’s be clear, without joking I think you are wrong to dismiss these possibilities and that you have an almost pathological lack of imagination. Yes, science fiction is about techs that do not exist yet are plausible.
You can fit a pool and a greenhouse in 250t. 40 cubic meters of water is 40 tons, 40 cubic meters of soil is basically the same. You have room to spare for the tennis court.
I am not a pro aviator, but I am a pro engineer, on an unrelated field, but I can do my napkins calculations. I mentioned the An-225 to make a point on the physically possible payloads that are possible today, with proven tech. I am not proposing we need those neither do we need the exceptional specs of that exceptional plane.
We scale down speed, it scales down drag (and necessary thrust) quadratically. We assume better efficiency on solar panels, batteries and motors because that’s what we will have in the future. Needing thrust only for sustaining flight and not for take off is another x5 factor on your calculation.
Look at you! You managed to scale down your initial super confident 600 000 m² estimate by an order of magnitude! I am proud of you!
From what I am reading this is about the amount of power an airliner uses at max power on all the engines. You are looking at 1/10th to 1/20th of that for sustained flight, and quadratically less at lower speeds that those typical of those airliners.
Dasus@lemmy.world 2 weeks ago
You’re wrong to assert things without considering the utmost basics. Thats’ why you’re the exact same as those people who imagined those 21st century images in the 19th century.
Yes, it’s a fancy idea. But it’s completely ignoring reality.
There’s much better fantasies to be had of things we can actually build.
“I am a pro engineer”
No, you’re not, ROFL. You haven’t even done rounded up basic maths with basic physics fucking LOL
I didn’t even use a calculator for that shit and I have zero engineering experience or education.
Yeah a regular airbus. Which is why it’s 4-6 times higher for a AN255 in fair weather conditions. And what you’re proposing would need to be several times the size of the AN255.
But no, you’re not wrong. You can’t be mistaken. None of what you think can be unrealistic. It’s just me, the guy doing the math you refused to even consider, who’s utterly wrong and your fantasies of firemen with flapping wings are ofc completely realistic. Oh wait no that’s the 19th century guys, I get you confused you constantly because both of those are equally unrealistic.