Space Travel with balloon assist

[r_rajesh77]

Near space travels with balloons.

http://edition.cnn.com/2015/03/05/tech/balloons-fly-edge-of-space/index.html

look at above link.

balloons goes just 36 km above Earth surface. but Earth orbit is 100 km away.

so my thinking is if we pump oxygen outside near helium balloon artificially when u r in near space, is it possible to reach the orbit? or is it just the oxygen will come down and helium balloon doesn't go up?

Also I read about Escape velocity will not be a problem as mentioned in

https://www.google.co.in/amp/s/amp...._ever_build_a_space_elevator_would_i_be_able/

Thanks & Best Regards,
Rajesh

 

[Bandersnatch]

so my thinking is if we pump oxygen outside near helium balloon artificially when u r in near space, is it possible to reach the orbit? or is it just the oxygen will come down and helium balloon doesn't go up?

It will just come down. Balloons are held aloft (or propelled upwards) by the force of buoyancy, which can be understood as the stationary mass of fluid below pushing them up. Much like floating in water does, or somewhat similar to standing on sand. You'd need to release enough gas to raise the level of the entire atmosphere, so that it's as dense at the height you want the balloon to get to, as it is now at the highest altitude accessible to it.

To visualise it better, imagine it's not gas and a balloon, but water and a buoy - you're releasing water around the buoy, because you want it to float up.As for orbits, escape velocities, and space elevators - to be in orbit you need to have orbital speed. Otherwise you're just at some height and will be pulled back down.
At 100 km above Earth surface that's close to 7 km/s. If you don't have it, then you need something to hold you up against gravity (like buoyancy - only as mentioned above, it doesn't work in vacuum). To be in orbit without gaining any extra tangential velocity, you'd have to somehow manage to raise to the geostationary orbit (at ~40 000 km) where orbital speed is equal to the speed gained from Earth rotation - which is what the concept of the space elevator is using.

 

[rootone]

The problem with this concept is that you have to spend a lot of energy pushing that oxygen up,
and then as you say it just comes back down again.
The same energy could be more efficiently used by deploying a normal rocket engine.

 

[r_rajesh77]

Thanks a lot for the answers.Here is my question in response to your answers.

What if we have suspended a hollow cylindrical structure from 100km to 36km and fill it with oxygen. Both top and bottom sides of the cylinder are closed and the enclosed pipe has oxygen in it. And when the balloon reaches 36km from ground level, let it inside the pipe and close the bottom. Will bouyancy be there to lift the balloon to 100km hieght? If so, we can have multiple rides till 100km.

 

[Bandersnatch]

Will bouyancy be there to lift the balloon to 100km hieght?

Sure, providing you pump in enough gas. You don't even have to close off the top end.

But then you have to figure out how are you going to support the tube+gas in mid-air (or mid-vacuum), which gets you back to your initial problem.

(oh, and if you open the bottom of the cylinder, the air will rush out)

 

[r_rajesh77]

Yeah I agree this is a challenge-able, but I do think we have technology now to do it.

My solution would be to have several tube+gas suspended at different heights.

When I have anything concrete on implementation I will keep posted.

 

[Bandersnatch]

but I do think we have technology now to do it.

We have levitation technology? What do we need balloons for, then?

 

[CWatters]

What would you suspend the tubes from?

 

[r_rajesh77]

Bandersnatch, let me come to the original reason why i was thinking about this. Elon Musk wants to send humans by 2025 to Mars and I guess it is one way trip. I was wondering if it is possible to have two way trip by some means.Then balloons may be a feasible technology than levitation technology. I was trying to solve part of the problem, by getting people from Mars surface to a possible nearby space station at mars(which might happen in future).

Thanks & Best Regards,
Rajesh

 

[russ_watters]

My solution would be to have several tube+gas suspended at different heights.

Do you recognize that your "solution" doesn't get you into orbit? What do you want to do when you get to the top of the tower?

When I have anything concrete on implementation I will keep posted.

Considering that the tallest structures we can currently build are about 1km tall, you will have your work cut out for you. But yeah, keep us posted.

 

[r_rajesh77]

> What do you want to do when you get to the top of the tower?

Even though I originally had idea to use it in mars, if I use it on earth,I may want to dissent down, I will use a slightly heavier gas to dissent.

 

[nasu]

If you have the technology to build that tube why bother with a balloon? You can just use the tube to climb up, like an elevator. You don't need to fill it with gas and to use a huge balloon. You don't even need a full tube. Just a few pillars.
The balloon makes sense only if you already have the atmosphere. Otherwise is just an awkward way to do it.

 

[r_rajesh77]

If we have technology to build a tube, i agree we just can climb up.

I just have another question. When a balloon floats over water due to buoyancy, the entire balloon completely floats over water. Is this the case with balloons over atmosphere? If so, we can have a big balloon filled with helium whose size is of several square kms. This balloon would be completely floating over atmosphere. We can have our small balloon which is like a weather balloon filled with gas lighter than helium and introduced inside the very big helium balloon. This second small sized balloon will then reach the top of the first very big sized helium filled balloon. Will this work?

 

[Drakkith]

When a balloon floats over water due to buoyancy, the entire balloon completely floats over water. Is this the case with balloons over atmosphere?

No, because the air is getting less dense as the balloon rises. To keep rising, the balloon would need to expand as it rises so the density of the gas inside remains less than the air outside. At some point the balloon reaches the maximum amount of "stretch" and stops stretching or bursts.

 

[ZapperZ]

> What do you want to do when you get to the top of the tower?

Even though I originally had idea to use it in mars, if I use it on earth,I may want to dissent down, I will use a slightly heavier gas to dissent.

There are easier and cheaper ways of doing the SAME thing.

The buoyancy requires a displacement of the volume of gas equal in weight to what you wish to float. How BIG of a diameter do you think the cylinder have to be to be able to float that much weight that you had in mind? Do you think the size of hot-air balloons was picked arbitrarily? So how technically feasible and reasonable do you think the diameter of your tube will be to be able to accomplish this?

You are letting the concept that you have fallen in love with get top priority rather than the actual goal, i.e. you are putting the means ahead of the ends.

Zz.

 

[russ_watters]

No, because the air is getting less dense as the balloon rises. To keep rising, the balloon would need to expand as it rises so the density of the gas inside remains less than the air outside. At some point the balloon reaches the maximum amount of "stretch" and stops stretching or bursts.

Also, the atmosphere doesn't have a surface to float on.

 

[phinds]

@r_rajesh77 you REALLY need to study some basic physics. You are floundering around with all this because you don't understand very basic concepts.

 

[mfb]

Bandersnatch, let me come to the original reason why i was thinking about this. Elon Musk wants to send humans by 2025 to Mars and I guess it is one way trip.

You don't have to guess, you can look it up. Reusability is a key point of Musk's plans, and it means getting the spacecraft back from Mars for another trip. That includes the option for humans to go back if they want.

Inflated towers have been suggested as option to build structures about 15-20 km tall. Tall enough to be above most of the atmospheric mass, tall enough to see the sky getting dark even during the day. Probably a nice tourist attraction, and launching rockets from there would reduce issues with atmospheric drag. But you still need the rockets.
A space fountain is a proposed structure that could be built more than 100 km tall. That gets you to space - but not to orbit. You still need a massive rocket to reach orbital velocity. The only way you can avoid this is a full space elevator - but if you have this there is no point in balloons.

 

[CWatters]

I just have another question. When a balloon floats over water due to buoyancy, the entire balloon completely floats over water.

That's not actually correct. A balloon is very light, so it doesn't displace much water, but it does displace some.

To float at all the average density of your balloon has to be less than the density of the medium it's floating in. I found a reference that says the density of the atmosphere at 100km is 5.55*10^-7kg/m3.

So to float at 1kg balloon at 100Km you would need a balloon that had a volume of 181,818 cubic meters. That would be a balloon 70m in diameter. The surface area of the balloon would be 15,000 square meters. Can you make a balloon that big that only weighs 1kg? (I've ignored the weight of any gas in the balloon)

 

[mfb]

At a density of 1 g/cm³ that would give 60 nm thickness. Good luck making a stable balloon out of that.

 

[phinds]

At 1 g/cm³ that would give a density of 60 nm. Good luck making a stable balloon out of that.

?

 

[CWatters]

Thickness of 60nm?

 

[mfb]

Yes, thickness of course. The density somehow moved from the front backwards.