Why don't we use balloons to get satellites into space. Wouldn't it use a lot less fuel to get a rocket 20 miles up and then launch?

Two main reasons for that:

#1 The most important obstacle is that actually would use a VERY big percentage of the fuel you *usually* use to launch a rocket from ground. Not all of it, but basically 70%.

Because fuel consumption is mostly about attaining the desired delta-v to manage into orbit. And at 20 miles from ground, that delta-v is basically the same for the orbit as the one from the ground (it depends on the distance from the Earth's center of the point you're launching from, so a decrease in speed due to the change in height of 20 miles is minuscule compared to the ~four THOUSAND miles of Earth's radius)

Sure, you'd have to fight a lot less air drag then when launching from ground, and that's actually where like 99% of your fuel savings would come from ... but that doesn't pay off really.

#3 Air obviously gets increasingly THIN as you ascend.

Ever seen the size of a balloon it takes to lift only a basket of five people, at sea level?

By the time you got even to the ten mile height, air density is so small the balloon would have to be a dozen *miles* in diameter - just to keep the satellite ITSELF from lowering.

Now when you take these two problems, there's no way to combine them - at any height - to not spend extra money and resources totaling the balloon and the rocket.

Also, what other people forgot to mention, take into consideration that it's excruciatingly hard to deal with a launch from anything else than a solid, reliable ground.

You know all the fuss a company has to go through to execute a ground-based launch? Take that ten-fold and you got yourself a launch in air.

Getting the rocket to start going at miles above Earth, and managing to get the balloon and whatever out of the way (which is going to be really hard because it should be massive), with all the wobble due to air currents, borders impossible (even after all the other stuff was done).

Hope that was useful!

Don't think we have enough helium to get a reasonable sized rocket that high ( it's fairly rare and no one has considered hydrogen since the Hindenburg, it would work ). Space plane is the intermediary and we are working on that one. We can't put a balloon into space and you seem to know that, a rocket isn't tons it's kilo tons and even at 20 miles altitude the Earths gravity is huge , that's 20 miles added to a 4000 mile radius . It does make sense but not sure it is practical.

It wouldn't work. There is a finite amount of helium available. We could try substituting for another gas but hydrogen is flammable so it wouldn't work. Nitrogen might work but it's not light enough to lift a balloon let alone a rocket ship.

Now lets assume we get enough helium. It still wouldn't work. As I stated helium is a finite resource so we use it in this balloon and how much helium will leak out? NASA is facing a similar issue with their plans to go to Mars. The valves leak too much. So even if you got enough helium to lift up the rocket, then you'd lose a lot of helium as it rises and you'd lose even more when you attempt to get the balloon back down. Since the only way to get it down would be to let some helium out, I'd assume most of it since the rocket itself would weigh significantly more than the balloon.

It's not a feasible idea but keep thinking. Engineers are trained to write down every single idea no matter how stupid they think it is because maybe part of it will help. Another idea, let's genetically modify giant gorillas to pick up the rocket and throw it into space.

Balloons float only because the air inside the balloon is less dense than the air outside, causing it to rise. But at the balloon gets higher, the less dense the air becomes and it will reach a point when the 2 densities becomes relatively equal. It can get you high in the atmosphere, but that's about it.

As well the satellite will weigh the balloon down, thereby it won't reach space by balloon alone.

During the X-prize competition, a company considered using balloons to get the vehicle high into the atmosphere, but then used rockets to get the space craft the rest of the way into orbit.

I remember watching a weather balloon in a telescope once. It appeared as a ghostly white disk which was very slowly moving against the background stars. I didn't realise what it was at first so for me it was the nearest I have ever got to seeing a 'UFO'.

Anyway after about 45 minutes the white disk had faded somewhat. I kept watching it until suddenly and without any warning it split into two distinct parts which then moved off rapidly in opposite directions. That's when I realised I was watching a weather balloon because as they rise up they have to expand due to the decreasing air pressure. The pressure inside the balloon increases. Once the balloon reaches a critical volume it bursts and whatever load it has been carrying falls back to Earth.

Well it would be pretty stupid and dangerous to use balloons, considering that it requires millions to lift up a single person. It would actually be more expensive to fill up millions of helium balloons than a rocket with fuel. Plus, balloons don't go as high as space, when they reach the edge of the Earth atmosphere they stop, then go back down again.

Altitude is not the major obstacle for getting an object into orbit--it is velocity. It has to go at least 5 miles per second just to reach low orbit, which makes a 20 mile altitude boost miniscule in comparative difficulty. A lot of people have the misconception that once you leave the atmosphere, there is zero gravity and an object will stay in space. That's not true at all--it's the object's velocity that keeps it from falling back to earth, not its altitude.

The so called Rockoon is not a new idea, and yes it works but it's a viable solution only for very small rockets (and I have never heard of a rockoon that reached orbit, usually they are just suborbital)

In suborbital sounding rockets the importance of the height reached is more important than speed, while orbital launches must obtain orbital speed to avoid falling back to earth, and in this case the advantage of starting the engines at 20miles of altitude(but also with speed close to zero ) is almost negligible, in fact a launcher can reach the same altitude(but with also a very significant speed) in few seconds.

And compare the cost of the alternative "making a rocket stage just slightly larger and add few %of fuel" with "let's build a colossal balloon, that has to be filled with helium or hydrogen, that can be punctured, which is more sensitive to wind conditions"

A space launcher have mass is in the order of hundreds of thousands kilograms. for example the Vega rocket, (a very small and lightweight launcher) weights about 137,000 kg (302,000 lb) , neglecting the balloon weight at sea level the balloon should have a volume exceeding 190000 cubic meters, equivalent to a sphere with a radius of about 36m(and a diameter of 72m) and consider that the rocket itself is about 30m high. This at sea level, reaching higher altitudes the atmospheric pressure get lower and lower and the balloon must get bigger and bigger to have the same buoyant force, it's simply unfeasable, and all this would save just few tons of relatively cheap solid rocket fuel.(for comparison the airship Hindenburg had an empty weight of about 118000 kg and a payload of about 60000 kg, and the volume was 200000 cubic meters)

This technique can be helpful if you want to launch a small sounding rocket(we could say the scientific equivalent of a rocket model) of few tens(maybe hundred) kg at high altitudes, but it will then fall to the ground immediately after reaching the maximum altitude

A balloon would not work because a satellite needs to attain a velocity which enables it to remain in orbit. A balloon could lift the satellite into space, and a rocket could then launch it into orbit but the balloon would need to be pretty huge.

That's gonna be some honking big balloon--and I think (but I don't know for sure) that once the atmosphere gets thinner and there's less air pressure, the pressure inside the balloon would be greater than that outside the balloon, and it would explode. It takes a lot of power to escape gravity--you can't get that kind of power with a balloon.