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TommyThompson
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- TL;DR Summary
- Build a tube to space.
Use our atmosphere to push a ship up the tube.
Build a tube to space.
Use our atmosphere to push a ship up the tube.
Use our atmosphere to push a ship up the tube.
Tommy, thinking outside the box is a great idea but only after you know what is IN the box. I suggest you study some basic physics.TommyThompson said:Build a tube to space.
Use our atmosphere to push a ship up the tube.
Welcome to PF.TommyThompson said:Build a tube to space.
Use our atmosphere to push a ship up the tube.
Always worth a try, Tommy .TommyThompson said:Summary:: Build a tube to space.
Use our atmosphere to push a ship up the tube.
Build a tube to space.
sophiecentaur said:That would mean you would need to extract (with a huge pump)all the air from above the piston.
The whole atmosphere is exposed to vacuum at the top. Yet somehow we continue to breathe...TommyThompson said:The tube would be exposed to the vacuum of space at the top. Therefore it's a vacuum tube.
Clearly you misunderstand what "vacuum tube" means. I say again, you would do well to just read some basic physics. Asking random questions on an Internet forum when you don't understand the basics is not going to prove very helpful.TommyThompson said:The tube would be exposed to the vacuum of space at the top. Therefore it's a vacuum tube.
Not if the air is flowing fast enough... which is what you're going to need to push the wall up and keep it from falling over. Wind will mess it up.TommyThompson said:The tube would be exposed to the vacuum of space at the top. Therefore it's a vacuum tube.
To expand a bit on my previous, if you open a hole in the side of a spaceship, air will indeed rush out and leave the ship evacuated. Earth's atmosphere does not rush off because it's held down by gravity. Gravity will not stop holding down a bit of air just because you put a tube around it. So the tube will remain full of air.TommyThompson said:The tube would be exposed to the vacuum of space at the top. Therefore it's a vacuum tube.
What in the world does the air speed do with whether or not it's a vacuum tube? I think perhaps you also don't understand what a vacuum tube is.hmmm27 said:Not if the air is flowing fast enough... which is what you're going to need to push the wall up and keep it from falling over. Wind will mess it up.
Well... if you can keep the air flowing through fast enough it will be an evacuating - not evacuated - tube. A "vacuum tube" is an electronics device.phinds said:What in the world does the air speed do with whether or not it's a vacuum tube? I think perhaps you also don't understand what a vacuum tube is.
hmmm27 said:A "vacuum tube" is an electronics device.
HAHA - plus many other objections. The poor OP has stepped into a big pile of PF brown stuff with his fanciful idea. He has received a vast amount of theoretical and practical objections to it - but it's a topic that has so many different facets to it.Filip Larsen said:If pumping has to occur at a decent rate, this implies a significant loss due to heat loss and similar.
Good idea. After you get that done, build a Dyson sphere.TommyThompson said:Summary:: Build a tube to space.
Use our atmosphere to push a ship up the tube.
Build a tube to space.
Use our atmosphere to push a ship up the tube.
I think you are not getting the joke.Ibix said:The whole atmosphere is exposed to vacuum at the top. Yet somehow we continue to breathe...
What on Earth makes you think it was a joke?FinBurger said:I think you are not getting the joke.
What makes you think this is a joke? It's far from the most harebrained misapplication of a misunderstanding of pressure that I've seen.FinBurger said:I think you are not getting the joke.
Shhh. You're giving him too many ideas. He needs to invent the thing himself. Maybe he wants to ride up on a cathode ray.Vanadium 50 said:Yes, but we can minaturize them with transistors. Then the tube is only 2 meters tall.
It's still not 100% clear to me how this is supposed to work. It seems that the idea is to pump down the tube and open it up from the bottom and let the air rush in, pushing the rocket up as it refills the tube. If so, there are two problems with that:
a) compare atmospheric pressure to a Saturn V's thrust per area of the 1st stage.
b) even if this got the rocket to the top - which it wouldn't - it has no horizontal velocity and would just fall back again.
yes, but that was lifting a much larger mass, and it was fighting air pressure in front of the rocket, and it throttled back part way through to avoid too much frictionVanadium 50 said:a) compare atmospheric pressure to a Saturn V's thrust per area of the 1st stage.
You can do some basic calculations to see if this will work. You should know roughly how fast a rocket needs to go to achieve orbit, and you can calculate the acceleration based on the length of the barrel. Calculate the acceleration over a 10km barrel, then calculate the allowable mass per unit area. I suspect you will find the thrust woefully insufficient.Al_ said:yes, but that was lifting a much larger mass, and it was fighting air pressure in front of the rocket, and it throttled back part way through to avoid too much friction
russ_watters said:this assumes you could achieve a constant acceleration profile from 0 to mach 20+, with air rushing into the barrel
It's not going to rush in faster than the RMS velocity of atoms at sea level, is it? So the maximum attainable speed is going to be on the order of 300m/s. Optimistically. And you'd presumably stop accelerating around the height where the capsule weight equals the weight of air that would naturally be in the column above you. That'll be quite a lot before the top.russ_watters said:[this assumes you could achieve a constant acceleration profile from 0 to mach 20+, with air rushing into the barrel]
As air flows in the bottom, air builds up in the tube below the projectile. The weight of this air acts against the air flowing in. The pressure differential between air flowing in and air at the bottom of the tube becomes less and less until they equalize. This will happen when the weight of the projectile plus the weight of the air below it weighs the same as a column of just air of equal diameter to the tube.Al_ said:Hmm. Maybe, this isn't such a crazy idea, if...
Bear with me.
The tube slopes upward and ends at a high altitude where the air poses little frictional resistance, say 10km. There is a cover over the top end preventing the thin air entering. At ground level, it is also sealed by a door, and large pumps remove 99.9% of the air. Inside the bottom end is a
sharp-nosed projectile. When the air is pumped out, the door is opened. The tube acts as a gas gun, accelerating the projectile to high speed. Open the cover at the top just in time.
The Hypertube idea shows us that a sharp-nosed vehicle can avoid contact with the sides of a tube at hypersonic velocities in very thin gas.
The question is, can it reach orbital velocity. There are ways to boost the thrust, such as opening ports in the sides as the projectile passes, or using hydrogen gas like they do in gas guns. Hydrogen would achieve a higher pressure at the top, being lighter.
I don't get this calculation. I think an air pressure of 10^5 Pa across pi/4 m^2 would give a force of 7.5*10^4 N producing an acceleration of 1.5*10^5 m/s^2 with a mass of 0.5 kg. IJanus said:So let's say that your tube is 1 meter in diameter, and your projectile masses 0.5 kg
in this case, at the very start, the upwards acceleration would be 10 m/sec/sec (~ 1g), but would die off to zero at ~16 km.
Now if the acceleration had remained 10 m/sec/sec over the same distance, the projectile would have reached ~ 0.566 km/sec or just small fraction of escape velocity. With a decreasing acceleration, you couldn't reach even a fraction of this.
Ragtrade said:Can you lift a significant payload to, let's say, the edge of the atmosphere with far less 'cost' (energy?) than the current brute force 'Tsiolkovsky' technology
High speed? What makes you say that? The force exerted by atmospheric pressure on the bottom of the projectile may be less than the weight of the projectile. In which case the velocity will be zero. All this to obtain a pressure on the bottom of one atmosphere? Vacuum does not have some magic power. It does not create large forces on objects. At the most it can allow the atmospheric pressure to act unbalanced.Al_ said:, accelerating the projectile to high speed.
It's the sort of effect that drives the weather; massive amounts of energy involved but not particularly usefully directed when the energy turns up in a small space. (Hurricanes and other bad weather examples). Wind turbines and sailing ships use it but don't have much effect on (even) the local weather.Ibix said:The basic principle is called a "solar chimney"
A tube launch system is a proposed method for launching spacecraft into space using a long, vacuum-sealed tube. The spacecraft would be propelled by electromagnetic acceleration through the tube, reaching high speeds before exiting into the atmosphere. This system is based on the concept of a railgun and would use similar technology to launch objects into space.
A tube launch system has the potential to be more cost-effective and efficient compared to traditional rocket launches. It would eliminate the need for large amounts of fuel and could potentially reduce the cost of launching payloads into space. However, the technology is still in its early stages and would require significant investment and development before it could be used for commercial space launches.
One of the main benefits of a tube launch system is the potential for reduced launch costs. It could also have a smaller environmental impact, as it would not require the burning of large amounts of fuel. Additionally, the speed and efficiency of a tube launch system could allow for more frequent and reliable launches, opening up new possibilities for space exploration and research.
There are several challenges and limitations that need to be addressed before a tube launch system can become a viable option for space launches. These include developing the technology to accelerate objects to high speeds without causing damage, creating a vacuum-sealed tube that can withstand extreme pressures and temperatures, and ensuring the safety of the spacecraft and crew during launch and exit from the tube.
While the concept of a tube launch system has been proposed and some research and development has been done, it is not yet a fully realized technology. There are ongoing efforts and investments being made to further explore the potential of this system, but it is difficult to predict when it may become a reality. It will likely require significant advancements in technology and infrastructure before it can be used for commercial space launches.