Hot Air Optional

An enterprising questioner at xkcd's what-if blog asks if it would be possible to drop from a great height with an uninflated balloon and tanks of helium, then on the way down inflate the balloon enough to reduce your falling speed and survive the landing.

The short answer seems to be that it is possible, but it would probably be difficult. The amount of helium would require several commercial tanks and some way of releasing the helium into the balloon very quickly, or you would run out of time. Personally, I am surprised MacGyver never had to do this.

The author notes that a large enough regular balloon would do the trick as well, by acting as a parachute. Which brings up the notion, he points out, of using an actual parachute to do the same thing more simply.

Unfortunately, a regular balloon would not inflate quickly enough to do any good unless a high-pressure fan of some kind was available. A hot-air balloon presents the same problem: beginning your fall with the equipment necessary to create enough hot air in a time short enough to do any good.

And of course, one could use alternative sources of hot air, but these might create their own problems. A sufficient number of my fellow clergy could probably produce enough hot air to inflate the balloon, but would that number be so large that it would overwhelm the balloon's drag factor and lifting power? Lawyers would create more hot air per person, and politicians even more. But there we run into the factor of knowing that if we have that many of either group on a splattery collision course with the ground, we face a great temptation to superglue that balloon's air intake shut.