HOW BIG A HELIUM BALLOON WOULDIT TAKE TO LIFT A 175 LBS PERSON?

Answer 1

Let's ignore the mass of the balloon itself and the string/rope/harness/whatever that connects it to the person. We're also going to ignore the compression of the balloon; we can assume it's mylar or something and the helium inside is at normal atmospheric pressure (if the balloon is compressing the helium, it will need to be bigger, since the density of the helium goes up as the pressure increases).

At around room temperature and ordinary pressures, helium has a density of about 0.164 kilograms per cubic meter. Under the same conditions, air has a density of a little under 1.2 kilograms per cubic meter. For a ballpark estimate, therefore, we can say that a balloon with a volume of 1 cubic meter will lift roughly 1 kilogram, which makes the calculation easy: to lift a 175 lb (80 kg) person, you need an 80 cubic meter balloon, which if spherical would have a radius of 2.67 meters or a little over 8 feet 9 inches.

A helium balloon 18 feet across should be sufficient to lift 175 pounds. Now you know why blimps are HUGE.

Answer 2

To lift a 175 lbs person, you would need a helium balloon with enough lift force to overcome the weight of the person. Assuming typical lift capacities of helium balloons, you would likely need a very large balloon, potentially around 70 feet in diameter or larger. It's essential to consider factors like helium density, ambient air density, balloon material, and safety margins when calculating the exact size needed.