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You dont need to carry fuel though. Solar on top of the airship can keep it moving along indefinitely, paired the ability to hang around aloft while waiting for
by Fatnino 4y ago
You dont need to carry fuel though. Solar on top of the airship can keep it moving along indefinitely, paired the ability to hang around aloft while waiting for more sun.
- walrus01 4y agoPhotovoltaics are way less powerful than you give them credit for, unless you want the electric motors to only push it at 10 knots... Where pv excels is cumulative kWh per month collection from something like a big cheap ground based array, the amount of watt hours you could collect in 12 hours from a top half of an airship covered in PV is not a lot, compared to the load of powerful electric motors.
- Tade0 4y agoI did the math for USS Akron, which was around 240x40m and was propelled by a 3.3MW power plant. It has a projected surface area of 7500m2, which, using modern, 22% efficient monocrystalline panels, yields 1.65MW, or half the desired amount, which I assume was used mostly for liftoff. In any case it's the same order of magnitude, so should be at least somewhat useful. There's always the question of weight, but much of that is the usual glass and aluminium casing.
- Denvercoder9 4y ago> which I assume was used mostly for liftoff Doubtful. It was filled with helium, so it would lift off on its own by virtue of being lighter than air. That power was necessary for propulsion.
- sandworm101 4y agoThe devide your numbers in half because sun will only ever hit half the airship. Then realize that when you neee power the most, in bad weather, the sun wont be there. Then subtract the mass of all those panels from the availible payload.
- ben_w 4y agoFrom @Tade0 writing "projected surface area", they have already accounted for the fraction in sunlight. You can also tell this is what was meant by noting a rectangle of those dimensions is larger than the stated projected area, which you should expect from the pointy bits on the ends. The weather that destroyed the USS Akron seems rather more important than the power source. I wonder if we can reliably make them go above or around clouds these days? I’ve not noticed clear air turbulence in air travel since I was a kid. If you have a positive answer on the weather safety, and if the PV is light enough that it could be considered a way of reducing fuel use rather than a Boolean yes/no decision to either fully replace a chemical fuel or not use it at all, it seems worth investigating. Edit: Just realised, while I’m usually unconvinced by RF beamed power, but with that surface area, and the general form of the inner frame, and it being in the sky so less danger from industrial accidents, this might possibly be a case where it could work.
- TylerE 4y agoNot indefinitely. Do descend they must vent lifting gas, and you can never get that back.
- smolder 4y agoAlternatively, the lifting gas can be compressed to raise the density and descend.
- TylerE 4y agoWhy would that change anything? Neither mass nor volume (of the craft) changs.
- Fatnino 4y agoVolume is changing somewhere. You compressed a gas bag so now normal outside air fills that space and your airship is heavier.
- TylerE 4y agoIt's a rigid envelope, not a gas bag. The volume doesn't change, and you certainly wouldn't mix in atmospheric air.
- smolder 4y agoI don't think it's infeasible that air could displace the lifting gas that was compressed, even in a rigid envelope. You could maybe build flexible bladders on the inside for this purpose. Another way to add weight using the same principle would just be to compress outside air into rigid tanks on the craft, making it heavier.
- devilbunny 4y agoDirigibles are rigid airframes, not rigid gas containers. They used gas bags to displace normal air from inside the frame and replace it with lifting gas.