If you fly fast enough in one direction can you reach space?

[JonnyFive]

Oakey said:

JonnyFive said:

Oakey said:

Munter said:

Eric Mc said:

If you have a means of propulsion which can operate in the vacuum of space (a rocket, essentially) then, yes, as long as thrust is constantly applied, the aircraft/rocket will keep climbing - and keep accelerating as well.

If the speed achieved is less than 17,500 mph, once the engine thrust stops (which is bound to happen at some point - usually when the fuel is exhausted), the aircraft/rocket will immediately start slowing down and will eventually fall back to earth.

If a speed of 17,500 mph is achieved, the aircraft/rocket would go into orbit around the earth - even when the engine has shut down.

If a speed of 25,000 mph is achieved, earth's gravity will not be able to hold on to it and it will go into orbit around the sun.

If it achieves a velocity of 37,000 mph, even the sun won't be able to hold it back and it will head out of the solar system never to come back.

Talking of escape velocities is confusing. Say I build a stack of bricks by standing on the top and hauling the bricks up using an electric motor. Eventually I could reach "space". Yet my velocity would be bugger all. Could a rocket with "unlimited" fuel not do the same thing? So long as it continues to move "up" even if only at 1 inch an hour, would it not eventually escape the earths pull? Why does it need those high speeds?

I think you need to think long and hard about your column of bricks, how high it would be to reach space, and the impact the rotation of the earth would have on that column. I wouldn't want to be stood at the top of it, that's for sure!

Theoretically speaking, which means all laws of physics and anything else credible goes out the window.. It is correct, no?

I think it needs the speed because it doesn't have unlimited fuel? Its got to get to a massive speed and get out of the earths pull pretty sharpish before it burns for too long?

How can it be 'correct'? It's a theory, that ignores all laws of physics!! That's like saying "If i jump high enough I can reach space".

In reality his column would start to bend, would it not? Not to mention at the top of it he'd be travelling at god knows how many mph.

Would you notice the rotational speed if your column couldn't bend? Theoretically..

(Genuine question as I'm stumped now )

[mrmr96]

Vipers said:

How do you define "In space" anyway?

Most people use 100km
http://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line

[Oakey]

JonnyFive said:

Oakey said:

JonnyFive said:

Oakey said:

Munter said:

Eric Mc said:

If you have a means of propulsion which can operate in the vacuum of space (a rocket, essentially) then, yes, as long as thrust is constantly applied, the aircraft/rocket will keep climbing - and keep accelerating as well.

If the speed achieved is less than 17,500 mph, once the engine thrust stops (which is bound to happen at some point - usually when the fuel is exhausted), the aircraft/rocket will immediately start slowing down and will eventually fall back to earth.

If a speed of 17,500 mph is achieved, the aircraft/rocket would go into orbit around the earth - even when the engine has shut down.

If a speed of 25,000 mph is achieved, earth's gravity will not be able to hold on to it and it will go into orbit around the sun.

If it achieves a velocity of 37,000 mph, even the sun won't be able to hold it back and it will head out of the solar system never to come back.

Talking of escape velocities is confusing. Say I build a stack of bricks by standing on the top and hauling the bricks up using an electric motor. Eventually I could reach "space". Yet my velocity would be bugger all. Could a rocket with "unlimited" fuel not do the same thing? So long as it continues to move "up" even if only at 1 inch an hour, would it not eventually escape the earths pull? Why does it need those high speeds?

I think you need to think long and hard about your column of bricks, how high it would be to reach space, and the impact the rotation of the earth would have on that column. I wouldn't want to be stood at the top of it, that's for sure!

Theoretically speaking, which means all laws of physics and anything else credible goes out the window.. It is correct, no?

I think it needs the speed because it doesn't have unlimited fuel? Its got to get to a massive speed and get out of the earths pull pretty sharpish before it burns for too long?

How can it be 'correct'? It's a theory, that ignores all laws of physics!! That's like saying "If i jump high enough I can reach space".

In reality his column would start to bend, would it not? Not to mention at the top of it he'd be travelling at god knows how many mph.

Would you notice the rotational speed if your column couldn't bend? Theoretically..

(Genuine question as I'm stumped now )

I'd imagine you'd still have to cling on for dear life, no?

ETA: Isn't this the same behaviour as if you were on a playground roundabout? In the centre of the roundabout (or back on earth) you wouldn't feel like you're going very fast, but at the edge of the roundabout (sat on the end of your column) you're feelng the speed a lot more?

Edited by Oakey on Tuesday 11th January 17:01

[mrmr96]

JonnyFive said:

Oakey said:

JonnyFive said:

Oakey said:

Munter said:

Eric Mc said:

If you have a means of propulsion which can operate in the vacuum of space (a rocket, essentially) then, yes, as long as thrust is constantly applied, the aircraft/rocket will keep climbing - and keep accelerating as well.

If the speed achieved is less than 17,500 mph, once the engine thrust stops (which is bound to happen at some point - usually when the fuel is exhausted), the aircraft/rocket will immediately start slowing down and will eventually fall back to earth.

If a speed of 17,500 mph is achieved, the aircraft/rocket would go into orbit around the earth - even when the engine has shut down.

If a speed of 25,000 mph is achieved, earth's gravity will not be able to hold on to it and it will go into orbit around the sun.

If it achieves a velocity of 37,000 mph, even the sun won't be able to hold it back and it will head out of the solar system never to come back.

Talking of escape velocities is confusing. Say I build a stack of bricks by standing on the top and hauling the bricks up using an electric motor. Eventually I could reach "space". Yet my velocity would be bugger all. Could a rocket with "unlimited" fuel not do the same thing? So long as it continues to move "up" even if only at 1 inch an hour, would it not eventually escape the earths pull? Why does it need those high speeds?

I think you need to think long and hard about your column of bricks, how high it would be to reach space, and the impact the rotation of the earth would have on that column. I wouldn't want to be stood at the top of it, that's for sure!

Theoretically speaking, which means all laws of physics and anything else credible goes out the window.. It is correct, no?

I think it needs the speed because it doesn't have unlimited fuel? Its got to get to a massive speed and get out of the earths pull pretty sharpish before it burns for too long?

How can it be 'correct'? It's a theory, that ignores all laws of physics!! That's like saying "If i jump high enough I can reach space".

In reality his column would start to bend, would it not? Not to mention at the top of it he'd be travelling at god knows how many mph.

Would you notice the rotational speed if your column couldn't bend? Theoretically..

(Genuine question as I'm stumped now )

Imagine dropping a rope from a geostationary satellite to earth.

[JonnyFive]

Is that Centrifugal Force? Would you get it because of the earth spinning and the base of your brick tower being on the ground?

In that respect, if you put a baloon out the top of the Burj Khalifa being 1 mile high, on a clear day without wind, would the baloon be off centre?

[Gargamel]

This isn't my specialist subject, but I am pretty sure the stack of bricks idea won't work.

I suspect that the first couple of courses of bricks will eventually collapse under the weight of the others piled on top of them ?

Just a thought

[mrmr96]

Gargamel said:

This isn't my specialist subject, but I am pretty sure the stack of bricks idea won't work.

I suspect that the first couple of courses of bricks will eventually collapse under the weight of the others piled on top of them ?

Just a thought

Do it as a pyramid?

[Gargamel]

mrmr96 said:

Gargamel said:

This isn't my specialist subject, but I am pretty sure the stack of bricks idea won't work.

I suspect that the first couple of courses of bricks will eventually collapse under the weight of the others piled on top of them ?

Just a thought

Do it as a pyramid?

Or simply re use the bricks from the bottom of the stack and place them on the top - recycling and weight saving

[Munter]

mrmr96 said:

Gargamel said:

This isn't my specialist subject, but I am pretty sure the stack of bricks idea won't work.

I suspect that the first couple of courses of bricks will eventually collapse under the weight of the others piled on top of them ?

Just a thought

Do it as a pyramid?

Chose bricks because I remember being told you could build a tower out in to space with them. By the time you have enough to crush the bottom ones the top ones are weightless. So I was told...

[dr_gn]

IIRC according to my Ladybird book "Exploring Space" you can get to the moon quite easily by harnessing about 15 swans with reins, attached to a big chair. You can then sit in the chair and the swans will fly up to the moon. I'm pretty sure that's how they did it before rockets.

I think that's how they did it, must admit I only ever looked at the pictures.

[deeen]

Munter said:

mrmr96 said:

Gargamel said:

This isn't my specialist subject, but I am pretty sure the stack of bricks idea won't work.

I suspect that the first couple of courses of bricks will eventually collapse under the weight of the others piled on top of them ?

Just a thought

Do it as a pyramid?

Chose bricks because I remember being told you could build a tower out in to space with them. By the time you have enough to crush the bottom ones the top ones are weightless. So I was told...

If it's on the equator, the brick at 22236 miles up will be weightless. Above that, the bricks will effectively be trying to take off, so once you get past that height, the more you build, the less pressure will be on the lower bricks.

Or you could just leave that 1 brick up there, and take away all the other bricks.


HTH

Edited by deeen on Tuesday 11th January 22:02

[JonnyFive]

deeen said:

Munter said:

mrmr96 said:

Gargamel said:

This isn't my specialist subject, but I am pretty sure the stack of bricks idea won't work.

I suspect that the first couple of courses of bricks will eventually collapse under the weight of the others piled on top of them ?

Just a thought

Do it as a pyramid?

Chose bricks because I remember being told you could build a tower out in to space with them. By the time you have enough to crush the bottom ones the top ones are weightless. So I was told...

If it's on the equator, the brick at 22236 miles up will be weightless. Above that, the bricks will effectively be trying to take off, so once you get past that 22236 mile high brick, the more you build, the less pressure will be on the lower bricks.

Or you could just put 1 brick there, at 22236 miles up, and forget all the other bricks.


HTH

How so you get your brick to 22236 miles up.. And then what about your electric winch?

Plus is 22236 miles random? Or is that the atmosphere edge?

[dr_gn]

deeen said:

Munter said:

mrmr96 said:

Gargamel said:

This isn't my specialist subject, but I am pretty sure the stack of bricks idea won't work.

I suspect that the first couple of courses of bricks will eventually collapse under the weight of the others piled on top of them ?

Just a thought

Do it as a pyramid?

Chose bricks because I remember being told you could build a tower out in to space with them. By the time you have enough to crush the bottom ones the top ones are weightless. So I was told...

If it's on the equator, the brick at 22236 miles up will be weightless. Above that, the bricks will effectively be trying to take off, so once you get past that height, the more you build, the less pressure will be on the lower bricks.

Or you could just leave that 1 brick up there, and take away all the other bricks.


HTH

Edited by deeen on Tuesday 11th January 22:02

I think a pyramid 22236 miles high would have enough gravity of its own to attract the top bricks back to itself.

[perdu]

Hooli said:

Mr E said:

Eric Mc said:

In theory a space cannon would work. But there are a couple of problems with space cannons.

1. All the velicity required for orbit or gravitational escape has to ne imparted the instant the projectile starts up the barrel of the gun. That means massive accelerative forces are imparted on it in a millisecond of the explosive charge firing. Not many instruments can survive that type of instant acceleration - 0 to 25,000 mph (say) in a fraction of a second.
Certainly no living being could withstand it.

Not necessarily.

Some sort of long acceleration track could impart the required energy in a sustained shove, rather than a single bang and tens of thousands of G. You could coil it (snail shell style) to make it more compact, but then you may introduce acceleration that you've just worked hard to reduce.

Ahh the rail guns so beloved of Arthur C. Clarke to put on the moon.

Ahh squared

the essence of the story "The Moon Is A Harsh Mistress" by Robert Heinlein: Unarmed Lunar colonists fight back against "Repressive Earth Rule"

My best ever favourite Science-fiction story




Oh sorry

we're talking big pile of bricks aren't we?

[RobDickinson]

Munter said:

Could a rocket with "unlimited" fuel not do the same thing? So long as it continues to move "up" even if only at 1 inch an hour, would it not eventually escape the earths pull? Why does it need those high speeds?

Yes and no. fi a rocket had unlimited fuel then velocity doesnt matter, your looking at a total cost to move up out of the gravity well, it doesnt have to be done quickly.

But as newtons laws of motion restrict us to chucking out mass at high velocities a rocket with unlimited fuel would need infinite mass and never move at all...

[deeen]

JonnyFive said:

Plus is 22236 miles random? Or is that the atmosphere edge?

It's the height for geostationary orbit. Atmosphere is much thinner than that, 75 miles.

I assumed the materials for the bricks came from earth, so ignored the gravitational effect of the pyramid. Don't know about the winch, maybe it got nicked by a bloke with a dag.

[dr_gn]

deeen said:

JonnyFive said:

Plus is 22236 miles random? Or is that the atmosphere edge?

It's the height for geostationary orbit. Atmosphere is much thinner than that, 75 miles.

I assumed the materials for the bricks came from earth, so ignored the gravitational effect of the pyramid. Don't know about the winch, maybe it got nicked by a bloke with a dag.

It's irrelevant where the bricks came from. The fact is that the top brick would be sitting upon the pyriamid itself. Since gravitational attraction is proportional to the inverse of the square of the distances between the centres of mass of the two objects, the top brick wouldn't "float" away at the same distance it would if it were in free space at that height above the earth, separated by nothing but the atmosphere.

[deeen]

dr_gn said:

deeen said:

JonnyFive said:

Plus is 22236 miles random? Or is that the atmosphere edge?

It's the height for geostationary orbit. Atmosphere is much thinner than that, 75 miles.

I assumed the materials for the bricks came from earth, so ignored the gravitational effect of the pyramid. Don't know about the winch, maybe it got nicked by a bloke with a dag.

It's irrelevant where the bricks came from. The fact is that the top brick would be sitting upon the pyriamid itself. Since gravitational attraction is proportional to the inverse of the square of the distances between the centres of mass of the two objects, the top brick wouldn't "float" away at the same distance it would if it were in free space at that height above the earth, separated by nothing but the atmosphere.

Sorry didn't realise we were actually going to build this.

Ok yes the pyramid does have an effect, because it moves the centre of gravity of the Earth. So I could express it better by saying for the top brick to appear weightless, it needs to be about 26200 miles above the centre of gravity of the combined Earth + pyramid.

But it is relevant where the bricks come from, cos that many bricks will weigh about a zillion tons, so if you bring them from somewhere else (Mars, for example) you increase the mass of the Earth+pyramid and the geostationary orbit will be higher.

[Neil H]

JonnyFive said:

Think OP means this;

If that's what he means, then it would work, but the path would be curved.

You don't need to reach tremendous speeds to reach space, only to escape the Earth's gravitational pull, or remain in orbit. You could work your way up there at a gentle pace if you found a way of doing it, however, once your engine stopped you would start to fall back to Earth if you hadn't achieved orbital speed at that point.

[Vipers]

I wonder if the pyramid builders had this problem