Although not the first to try and build a DIY solar-powered remote control airplane, [ProjectAir]’s recent attempt is the most significant one in recent memory. It follows [rctestflight]’s multi-year saga with its v4 revision in 2019, as well as 2022’s rather big one by [Bearospace]. With so many examples to look at, building a solar-powered RC airplane in 2024 should be a snap, surely?
The first handicap was that [ProjectAir] is based in the UK, which means dealing with the famously sunny weather in those regions. The next issue was that the expensive, 20% efficient solar panels are exceedingly fragile, so the hope was that hot-gluing them to the foam of the airplane would keep them safe, even in the case of a crash. During the first test flights they quickly found that although the airplane few fairly well, the moment the sun vanished behind another cloud, the airplane would quite literally fall out of the sky, damaging some cells in the process.
For the final revision, a storage battery was picked, which got charged with an MPPT charger. The airplane itself was changed to be as low-drag as possible, with 60 photovoltaic (PV) cells stuck to its wings. This resulted in the somewhat spindly, swept wing, tail-less pusher design. After debugging a fun issue with EMI from the motor and the navigation module a test flight could be performed, which had the airplane autonomously keep a fixed course. That’s when everything went horribly wrong.
During the subsequent crash investigation, it was found that a total power loss occurred, due to the MPPT charger overcharging the battery, possibly due to a shared ground with the PV cells. Simultaneously, likely due to rushing the testing as bad weather was incoming, the backup battery on the controller was not installed, resulting in the airplane plummeting once primary power ran out. Fortunately, all of these are fixable issues, while providing a learning experience at the cost of an RC airplane and the PV cells that got destroyed in the crash.
Perhaps most importantly, this shows that even if much of building one’s own PV RC airplane in 2024 is just sticking off-the-shelf modules together, there’s no substitute for good engineering, not to mention assembly & pre-flight checklists.
I Wonder if a flying wing design could offer a low drag/ high wing surface area solution interesting for such an andeavour.
A friend of mine ran simulations and built this one.
https://xflr5.sourceforge.io/Screenshots/Aile_Volante.htm
Flew a bit more than 10 hours.
I sadly I crashed it after 8 hours (2 pilots relaying) due to being a noob pilot and being disoriented after so much time.
pre-flight checklists …… I’m constantly amzed why people do not do this.
Wholeheartedly agree. I’ve wondered the same for some advanced amateur rocketry projects. I think it’s pride related – Checklists? Checklists? We don’t need no stinking checklists. We’re SMART.
Haven’t checked the vid yet, but if it’s crashing on power loss the design sounds inherently unstable. Might be worth a redesign to get that sorted… a decent glide profile should help get it back safely
With the control surfaces stuck in what ever position they were in when the power failed, I can’t imagine any other scenario that crashing.
5seconds of sunshine window in the UK :D
In UK, there’s no MPPT. There’s only HAPP (Hoping for any power please). And it doesn’t work very well
MPPT: Minimum power point tracking
MPPT: More Power, Please & Thank you
hehehe, kind of true, but it really isn’t actually that bad. Even when we have had one of the stormiest and wettest summers there is a fair bit of power to be had.
With an array that sort of size you will get meaningful power while the sun is up, should be more than enough for a relatively glider like aircraft to extend its range a long long way, assuming it can survive the high winds it should do fine even over the unusually gloomy even for the UK skies round here of late. And if as looks likely it was never meant to survive anything but fair weather flying, well then when it is in the air at all it will have lots of power available.
Kinda think in the UK we could try some kind of piezo electric wing stimulated by getting hit with rain/hail/sleet etc… :)
seems like testing the cells+charger+battery combo is something you could do on the ground without smashing anything up :)
Hmmm highly swept foam flying wing of dubious design, expensive fragile solar cells and cheap chineseium electronics…. what could possibly go wrong.
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I don’t understand why anyone would go with a design that would just crash out of the air when it loses power.
Ignoring that apparently the solar cells were easy to damage making crashes especially undesirable. That would still leave that it is likely much better for an efficient design to be an extremely good glider with only minimal input needed to stay airborne.
Who cares about drag if your design has the glide ratio of a quadcopter.
Here’s video of an efficient unstable flying wing. Active stabilization instead of reflex airfoil gives more lift for the same size wing. They got 6% gain and expect more. https://youtu.be/iQ03qMD9u90