if i wanted to move something big, and the normal options such as trucks or cranes were not feasible, could I use helium balloons to lift them?
For the purpose of consistency lets say the load is a 10 tonne (10,000 kg) concrete slab, it has to travel 100 metres and jump a few fences along the way. If temperature is an issue, its a sunny 20 deg C.
specific questions are:
if using one spherical helium balloon, how big would it have to be to generate that lift?
When the slab leaves the ground can it be manipulated and pushed by hand or does the 10 tonne mass still have to be overcome?
Does temperature have an effect on the balloon - as the sun heats it up, if its a fixed, not expanding sphere, does it increase / decrease in lift power?
Yes to both. Friction is what usually makes it hard to move big things, and that will be almost nonexistent with this setup. But F = ma, which means that for a large mass and a small force, your acceleration is going to be very low. In other words, you can move it if you’re patient, but it’ll take a long time to get up to speed, and once you get it up to speed, it’ll take the same long time to stop it.
That’s not all that much concrete, I could place and finish that for maybe $1000 or a little more, another $500 to jackhammer and haul out the old slab.
As the balloon and helium warm up the fixed size balloon will weight exactly the same. Lift is derived not from the weight of the helium, but from the *difference *between the weight of the helium and the weight of the surrounding air.
If the *air *warms up it becomes less dense and the helium is relatively less different and your lifting force decreases. If the *air *cools down it becomes more dense and the helium is relatively more different and your lifting force increases.
Things are more complicated if your balloon is elastic. Then as the helium warms the balloon stretches and expands. Which changes how much air it’s displacing. This effect works against the effect explained above. Which effect predominates depends on the specifics of the balloon elasticity and of the different temperature changes of the helium and the air.
So you are looking at over $35,000 worth of helium just to lift the 10,000 lbs. You still have to lift the balloon and a balloon that big is going to be very heavy.
The OP’s another case of gut feel estimates way off from reality. 10,000kg of concrete is a small amount. 10,000kg of lifting force derived from helium is a large amount. Probably the opposite of what he thought when he posed the problem.
This is a smaller version of the threads in which people ask why blimps aren’t all over the sky. Lifting with balloons is a wonderful theoretical idea but runs rather quickly into insurmountable practical difficulties.
Peole sometimes move weughts like this on pressurized air. It’s not uncommon to see an air pressure socket in the base of very large heavy machinary.
In actual practice, it is much easier to start something like this moving, than it is to stop it. You just lean against it for a while, and it starts moving. For some reason, it’s much harder to get your head around the fact that you have to lean against it for the same amount of time to stop it, and this it will crush you flat if you get between it and a wall.
There was a very nice science fiction treatment of this by Dean Ing, titled “The Big Lifters.” Pretty good story, with the involvement of the truckers’ union, etc. Too bad it won’t really work; the idea is tremendously attractive. Mobile cranes, emergency lifting power, the ability to swap cargo between moving trains… Oh, well!
Thanks all for the replies - I knew you’d come good.
Yes, some of it is very counter-intuitive, such as the effect of rising and falling temperatures.
I know my 10 tonne slab is rather modest, but I wanted something I could multiply. And the cost is lower than I thought -this site gives U$33,000 for a 'medium passenger carrying" balloon of 18 metres diameter, so one scaled up to 27 metres diameter would have to give you change back from $100K. And yes, allow for the balloon’s own weight etc.
A sealed balloon would be presumably reusable time and again, until that moment’s inattention when it goes zooming off into the sky while you are busy trying to text someone and let go of the big string. It happened to me at the circus and it can happen again.
A quick question that has nothing to do with the OP. I have some old steps that need jack hammering and removal. Who do you call? Are there concrete removal specialists?
That’s a hot-air balloon. they’re certainly less airtight than you’ll want for a helium balloon. let’s say that costs double, so we’re at $66k. But then a 27m balloon has over twice the surface area as an 18m balloon. so $132k. then, as was said above, we’ll need to fill our 27m balloon with ~693k ft^3 of 1 atm helium. according to some online searches, the spot price is somewhere like $100/1000 ft^3, so we’re talking another $70,000, or about $200,000 all-in.
Any contractor should be able to handle that job … probably a concrete contractor would be best … MAKE SURE they’re licensed and bonded … ask to see their credentials … any honest contractor would be happy to produce them.
