so,

hot air balloons are pretty great because they don't have hard to store leaky and expensive , or flammable gasses

air is everywhere . you just need to heat it up.

we all know how traditional propane baloons work.

otherwise there's 'solar' balloons.

solar hot air balloons have been toyed with some time. directly thermal balloons that work on soaking up the suns direct rays and transmitting the heat to the internal air of the balloon.

meanwhile, the problem with propane powered hot air balloons are they are heavy. solar balloons are not really reliable nor does the air heat up all that much.

the upside is that, unburdened by lifting rigs, they are so lightweight they don't need much lifting bouyancy from the hot air gas. they are essentially big black garbage bags that float when it's sunny out.

how about a new approach to creating an ultra lightweight balloon that needs no propane and can stay tethered but without bringing it down to resupply with lifting gas. PLUS the balloon can generate electricity on site, without electric cables, or heavy solar panels mounted on the balloon.

simple-----get a rectenna to recieve microwaves with a battery and an electric heating element in the balloon.

the microwaves can be directed precisely on target and travel directly into the balloon . the balloon is not propane powered and thus, between solar energy and microwave energy, the balloon does not need to have a heat leaking outport/inport.

a small valve for air can be designed into the balloon which is designed to keep heat IN the balloon as well as possible while being fairly light weight.

the balloon can convert solar and microwave radiation directly to heat, and when needed convert the microwave energy to electricity for whatever electrical needs the balloon might have. a small valve allows for air release and entry.

this sort of platform could also be ideal for a floating city where these balloons are tethered to the mother platform and are reheated as necessary. systems are designed for as little heat leakage as possible.

BONUS POINTS

USE HELIUM INSTEAD OF AIR---AND

FOR HAVING IT BE A TOTALLY SEALED VALVELESS BALLOON WITH INTERNAL HEAT SINK ( IF THE BALLOON GETS TOO MUCH HEAT)

The bouyancy of HOT helium is such that you could probably run the balloon on very little helium. problem is 'hot' helium is probably especially leaky. however advanced new thin films are especially impermeable and may one day soon serve as appropriate skins for these types of hot helium containing baloons.
-- teslaberry, Apr 08 2014

What [Alterother] thought.
-- blissmiss, Apr 08 2014


good Idea, only issue l can see is how cost efficient would it be, in comparison to just filling it with Helium or hydrogen. (obviously more efficient than a hot air balloon)
-- mofosyne, Apr 08 2014


My cubemate is the grandson of Jean Piccard, (the namesake of for whom the character Jean-Luc was named) and has a special place in his heart for balloons. I'll have to run this by him to get his input.
-- RayfordSteele, Apr 08 2014


[+] but I didn't really read this. Could you give a three liner summary?
-- pashute, Apr 08 2014


and move it to Vehicle:Aircraft:Baloon
-- pashute, Apr 08 2014


Blis, what did alterother thought?
-- pashute, Apr 08 2014


There is a simpler way to do this. Inside the balloon, at the bottom of the balloon, have a microwave-safe plastic pan of water. Beam the microwaves at the base of the balloon, from an angle and a distance, so that the water absorbs the microwaves. Ensure the gondola hangs far enough below the bottom of the balloon so that the microwaves miss the passengers. The water turns to steam and heats the air in the balloon. Any water that cools will condense and return to the pan, where it can be boiled again.
-- Vernon, Apr 08 2014


[+] idea [+] Vernon's suggestion.

Liquid-to-vapor is 1000x volume. Heated gas is just linear to absolute temperature % differences.

That said, don't be thinking "cities" yet. As, you can never get more upwards force than the displaced air. Meaning, the maximum limit is ~1 kg/m^3 displaced. So a 10m cubed balloon has an upper lift limit of ~1,000 kg (~1 ton). Actual limits are 0.1-0.3 that.
-- sophocles, Apr 08 2014


Line of sight problems can turn into a fun juggling game:

Thousands of balloons are floating, but as they get in each other's way, you can't target energy at them, so they fall. The ones that fall furthest get within line of sight again, & you can shoot them.
-- sophocles, Apr 08 2014



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