What are they inflated with? They’re pretty big, and if they were inflated entirely with helium it would not only be very expensive but generate more lift than is needed or wanted. Is dry nitrogen enough of a lifting gas to get them off the ground?
They use helium.
Nitrogen has a molecular mass of 28 grams per mole. Air is mostly nitrogen but the oxygen brings the average molecular mass of dry air to about 29. Since helium has a mass of about 4, it has about 25 times more lifting power than dry nitrogen. If helium provides more lift than needed, you could dilute with air to save money.
They’re also heavier than you’d think, and they’re being handled by dozens of people holding onto ropes.
That doesn’t sound right, the handlers are to control them as they have a huge surface area and the wind can really bounce them around. They’re a little bit like big sails. It’s not that they’re heavy so much.
You can take this cite for what it’s worth, but it saysthe big balloons take 12,000 cu. ft. of helium “which can lift up to 750 pounds.”
The balloons themselves are heavy - probably 300-400 pounds.
The lift due to the helium is several hundred pounds, and when the anchor rope is removed from the guide truck, it takes 20 or more people to hold it down.
The Macy’s parade is one of the single largest consumers of helium in the world.
Cite.
Did you just cite your own post?
Yep.
Before the parade gets under way, you used to be able to wander by and see them being filled the day/evening before. Now it’s also a major event and crowded as only a NYC event can be crowded. To hold down the balloons until launch date, they are covered with rope nets and big weights on the net… So they are pretty floaty. Keep in mind these are fairly thick vinyl, they make your beach ball look flimsy. The rope anchor points are made of some fairly thick, sturdy patches. yet, sometimes the balloons still tear. And they are solid enough to take down a lamppost instead of shredding.
In 1997 several of the balloons rose up in rebellion and attacked the crowd. One lady got a severe head injury and the NYPD was forced to disembowel several beloved childrens’ icons on live television. Nowadays they keep a closer look on the wind forecast.
It occurs to me now that if most of the helium can be recovered from the balloons after the parade, the expense might not be as severe as I’d presumed. Still, if it wasn’t for venerability’s sake, the balloons ought to be replaced with something better designed.
You would think it would be worth trying to save it, but at the end of the parade, the helium is simply released and it floats away (watch out, iPhone users!). I have a photo of the helium being released, and you can see the “wavering” effect in the air (just like “heat waves.”)
How much do you want to spend on recovery equipment? Airgas, annoyingly, doesn’t give web quotes to my zip code, but this price sheet from Oklahoma State University, detailing their purchasing prices for the gasses they buy, should be helpful: https://purchasing.okstate.edu/sites/default/files/documents/oshop/Compressed%2520Gas%2520Bid%2520Price%2520Summary.pdf
From it, dated 2018, they pay ~80 dollars for a 300 cubic foot container, pressurized to just under 3,000 psi. From that, figure out how much it costs to fill the balloons, and see if it would be worthwhile to try to recapture it. At a certain price, it would be. I guess they aren’t quite there yet.
Hmmm. When the looming helium shortage was appearing in the news a lot, the Macy’s Day organizers announced plans to recover the helium from the balloons:
https://cityroom.blogs.nytimes.com/2008/11/25/putting-the-helium-back-in-the-bottle/
If that never worked out, it should be noted that even though the Macy’s parade is a large single use, lifting applications only account for about 12% of helium use, from party balloons to filling blimps. By far the largest use of helium is in cryogenic applications, and MRI machines are the major user. They are supposed to be doing a much better job of recovering the helium these days.
We’re still working on antigravity sleds.
It’s tempting to think that some mixture of hydrogen (cheap) and nitrogen could get the job done and also not be a fire hazard.
Hot air balloons are lifted by nothing but air, heated by propane burners. And they have to carry the buburners, and propane, and humans aloft with them. Would it be possible to have a Macy’s balloon tethered to a burner truck*, which heats up the air and blows it through a large tube going up into the balloon? Possibly the noise of such an arrangement would make it unworkable, though.
- Of course, that would use up a fair amount of propane during the parade – still not good for then environment. Not having a parade at all would be best, environmentally; but we’re not willing to give that up anytime soon.
I’ve been in, or rather, carried under a hot air balloon. They are enormous. Bigger than the Macy’s parade balloons. Not sure such balloons would be able to fit between the buildings and other obstacles along that route.