Talk:3161: Airspeed
must be a heated competition 79.78.17.137 21:34, 29 October 2025 (UTC)
It's actually worth noting that a quick google says that land speed records for hot air balloons are actually fairly fast, wikipedia claiming it clocks in at around 245 mph. Jet streams allow them to go pretty fast! 45.78.106.197 23:42, 29 October 2025 (UTC)
Airspeed is relative to the vehicle, and a balloon has no "front", so a gust in one direction is in theory indistinguishable from a lull in the opposite direction; both will appear as a momentary increase in airspeed until the balloon accelerates (in whichever direction) to match the local air movement. (I say "in theory" because if you consider your gusts and lulls relative to the overall movement of the airmass, it's plausible that one or the other will tend to be sharper.) The "gust that allowed them to coast", and the whole notion of "coasting", isn't really right. A non-zero airspeed means that the balloon hasn't re-stabilized with the local air movement, in whichever direction. In fact, "coasting", defined here as momentarily moving differently from the airmass as a whole, is actually an unlikely source of the 2MPH airspeed, because it requires that the balloon accelerate to match local air movement, before returning to the movement of the airmass as a whole. More likely is a localized change (a gust or lull), that causes the local air to be moving differently from the airmass as a whole, while the balloon is still moving with the airmass. Such a localized change might be present for a very small amount of time, not long enough to appreciably change the balloon's movement. But I'm not feeling like spending enough effort to distill that down into one sentence to update the explanation. Jordan Brown (talk) 23:59, 29 October 2025 (UTC)
You don't need a mine shaft to go for the minimum-altitude record, if you're measuring against MSL. Just make sure that your lines and your balloon are really strong, and your basket is really heavy, and your basket is water-tight, and go for Challenger Deep. Jordan Brown (talk) 00:21, 30 October 2025 (UTC)
3161 demonstrates a commonly held fallacy - the balloon has NO actual "airspeed" because it moves passively with the surrounding air mass; it has no method for generating lateral force on its own, to either vector add/subtract airspeed from the moving wind surrounding it. The balloon is never actually being "blown". This isn't just semantics - it has real relevance to powered aircraft flight. 01:38, 30 October 2025 (UTC)Aviator Joe, CFII
Sure it does, transiently. It just can't cause itself to have a non-zero airspeed. An abrupt change in the movement of the local air - a gust, horizontal wind shear - would register as a non-zero airspeed, until either the local air goes back to matching the overall airmass (and the balloon), or the balloon accelerates (via drag) to match that moving air. Consider: you're cruising along in your airplane at an indicated airspeed of 100kt, and you get a 10kt gust from the front. Your airspeed indicator momentarily jumps to 110kt until the airplane restabilizes at an IAS of 100kt again, and then when the gust goes away the reverse happens; your IAS drops to 90kt for a while, then returns to 100kt. The exact same thing can happen in a balloon, except that the base IAS is zero - the balloon that you were passing as the gust hit you sees an IAS of 10kt as the gust hits it, then zero as it restabilizes, then 10kt in the opposite direction as the gust fades, then zero again. Jordan Brown (talk) 02:42, 30 October 2025 (UTC)
