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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

#141

Post by Stevvo »

contingencies wrote: post #137
titanomachy wrote: post #133

Earlier quoted context omitted.

Wow, the "Silent Yachts" one has a "fully automated towing kite"! That's not something I've ever encountered before, very clever. Removes the need for an annoyingly tall mast and probably saves a lot of weight as well.

A mast provides a predictable center of lift in the boat on two axes, easy to control, handles high winds elegantly. Kite? Not so much. Also, try sailing in to the wind with a kite. May be possible, but very, very slow going. Traditional sail plans strike a balance between functionality at all points of sail, ease of handling and safety. They also have downwind sail options.

One advantage of a kite sail is you have more surface area for solar panels and those panels are not going to shaded by the sail while underway.

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

#142

Post by Scoundreller »

ncmncm wrote: post #126
noitpmeder wrote: post #116

Earlier quoted context omitted.

Again I have to believe this is only a temporary restriction.

SpaceX are launching satellites with ("frickin") lasers now. So, if you are in the middle of the ocean, your packets step between satellites on the same orbit, forward or back, until they get in range of a node. First actual use is for polar service. On certain routes, packets will be artificially delayed so that high-speed traders can pay big bucks to get their packets through first, ahead of fiber. And, maybe pay e…

I suspect this is why starlink has some base station licenses in eastern parts of Newfoundland. It’s the closest you can get to London before swimming from Contiguous North America.

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

#143

Post by javajosh »

goldenkey wrote: post #121
Stevvo wrote: post #117

Earlier quoted context omitted.

I have a 38' steel sloop with 400w of solar + a wind generator on-board. I'm not a full-time liveaboard, but I have been on-board for the last couple of months and you can definitely make it work. Sailing is labor intensive, but not in the ways you imagine. Navigation, docking and provisioning are all straightforward. Where it can sometimes feel like a full-time job is maintenance. Everything on a boat wants to break…

I learned a few years ago about barnacles, which by virtue of being unaerodynamic and super heavy if you let them form huge colonies on the bottom of your ship, can decrease fuel efficiency severely. I saw how much work maintanence was, I said 'nope!' I guess a house is similar in some ways. Shingles don't last forever, pipes get corroded. The salty sea though, it's a bit more unkind to things, aye?

If you use anti-fouling bottom paint and either a) live in a region where it's pleasant to dive and scrub your hull, or b) can pay a service to do it for you, either way it's only a once a month thing, and a haul out ever couple of years. Although I can't speak to steel hulls, with fiberglass water can get into the fiberglass causing blisters that have to be ground out and epoxied in, which is precisely as annoying and expensive as it sounds.

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

#145

Post by javajosh »

silisili wrote: post #132
jws wrote: post #74

Earlier quoted context omitted.

…cause a boat to tilt to the side… This is a net positive. The alternative is to roll back and forth with the waves. It’s much nicer with the sail up and ata bit of a heel. Also, just to throw this in, one of the world cruising sailing couples which wrote for the magazines switched to a diesel powered boat as they aged and found that they spent less of fuel than they had on new sails. Sails are consumables if you car…

Interesting last point...curious why is that? Do they get battered from weather and physically tear, or do they just stretch/thin over time?

Racers use very thin, light, and stiff sails made from mylar or similar materials. They are typically very expensive and want to be changed as often as possible, at least once every racing season. Modern small pleasure yacht cruising sails "canvas" is laminated polyester, aka dacron, which is far thicker, more durable, springier, and more common than mylar.

It's an interesting question, where does the wear come from. But sails are a very active part of the boat; every tack is going to drag the sail across the deck of the boat, rub against fittings. When a sail luffs, head-to-wind it's whipping around with the weight of the sheets (control lines), and then when you're taking the sail down it's getting folded (best case) or stuffed into a bag (worst case) [EDIT: some sail materials like being shoved in a bag!]. And of course even when a sail is just sitting there powering the boat it's under a tremendous amount of force, which stretches it over time.

Sails do fail, and yes often by ripping in half. I've personally never heard of a sail failing at the control points (e.g. the tack of a jib), probably because those areas are heavily reinforced.

https://www.northsails.com/sailing/en/sails/materials

https://en.wikipedia.org/wiki/Sail

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

#146

Post by krisrm »

zucker42 wrote: post #139
algo_trader wrote: post #82

Earlier quoted context omitted.

nice analysis Is it feasible to operate these at lower altitudes? e.g. can we have solar/air drones posted every 100 miles of interstate highway?!

> e.g. can we have solar/air drones posted every 100 miles of interstate highway?! What's the usefulness of this or was it just a random example?

As someone who lives somewhere with photo radar, I assume photo radar.

Nobody likes photo radar.

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

#147

Post by rootusrootus »

llbeansandrice wrote: post #128
rootusrootus wrote: post #125

Earlier quoted context omitted.

At least with a house the timeline is long and it's easy to hire someone to do it for you. Even galvanized pipes last 40-50 years without much problem, and newer pex pipes may last indefinitely. Roofs are 25+ years.

Not soaking your house in salt water really helps with longevity I've found

For sure. Even then, the techniques used by builders at the beach seem to allow houses to endure a long time.

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

#148

Post by wingworks »

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…

These guys spent the night on the Silent-Yachts one a ~month ago. https://www.youtube.com/watch?v=iIte4FNI0U0

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

#149

Post by pg_bot »

bagels wrote: post #66

To fly through the night, you need energy. I'm wondering if it's more efficient to store it in the batteries, or as stored kinetic energy by flying to a high altitude and descending through the night.

If you fly fast enough you can outrun the night, but that opens up a whole new set of problems.

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

#150

Post by caconym_ »

tomxor wrote: post #47
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-…

[EDIT] remove redundant info > Airbus would need quite a few of these in order to build a global internet connectivity service then. Yes it would require more units, but with a much smaller cost per unit for build, launch and maintenance. That's where it will start to get interesting: Which will have the lowest cost per GB, per user, per square km of coverage etc? I suspect even if it's cheaper it would still remain…

> with a much smaller cost per unit for build, launch and maintenance

Somebody further down in the comments estimates $250k in launch costs for each Starlink satellite^[1]. Elsewhere, I found a claim that SpaceX execs said in 2019 that the per-satellite cost was "well below" $500k^[2]. So let's say $400k per satellite including manufacturing and launch, just to pick a number.

Once it's in orbit, you need to pay for operations, but not maintenance (except on your ground-based infrastructure). And multiple factors (e.g. cheaper launch) stand to bring that price down.

Realistically, how much do we expect one Starlink satellite's worth of telecom UAS to cost on an ongoing basis, including the maintenance and operations costs that don't apply to Starlink? Where is the analysis? OP's article makes the "cheaper" claim with (AFAICT) absolutely nothing to back it up, and the fact is that full size aircraft are not cheap.

The service density flexibility and possibility for additional radio bands Starlink can't provide might be a good argument for this system to exist, but all this talk of it being cheaper seems very vague and presumptuous. What am I missing?

^[1] https://news.ycombinator.com/item?id=28832257

^[2] https://www.teslarati.com/spacex-starlink-satellite-launch-s...

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