Flying with a helium balloon is the most energy efficient way to fly:
- no energy used
- no downwash (therefore sometimes called aerostats)
A helium balloon rises due to the difference in the atmospheric pressure between its top and bottom. This buoyant force acts naturally on everything immersed in a fluid in a gravitational field, not just on lighter than air volumes. Also on your body, so your scale is not exactly right, you're a bit heavier.
At sea level, the atmospheric pressure is about: 10330 kg/m2
At sea level, 1 cubic meter of air weighs about: 1,225 kg/m3
When going up 1 meter, the atmospheric pressure drops about 1,2 kg per square meter, at sea level.
Extreme buoyant lift is shown by a boat. A boat makes a hole in the water. Because the top of the boat is above the surface of the water, no water can come in. The weight of water is much higher than air, so the difference in pressure per meter is also much higher.
In theory it's also possible to let a boat float on air. The top of the air-boat should be in space, so no air can get in, and of course should the air-boat be large, light, and very strong.
An aircraft that flies on buoyant lift, must be huge and very light in order to gather enough upwards force. Some gasses are very light, lighter than air, like helium or hydrogen. Gas can be made even lighter per volume by heating it, expanding it.
Sucking a disc vacuum will make it lighter, but the atmospheric pressure is so high that a lightweight disc will surely collapse. Are there ways to create a large vacuum or lower pressure area, without the need for a heavy construction?
Gas can also become lighter per volume by dynamic expansion, by for example by spinning the air, or by charging the air with an extremely high voltage. I've never seen that being used anywhere. © Me.
I'm thinking about creating a giant vortex ring, because that has a lower pressure center, and thus less weight. But a giant vortex ring in contact with the surrounding air, will lose a lot of energy that way...