stupid physics questions

[pogo]

The problem with balloons is they work by being lighter than air. Even though it's far denser than air here it's still air. So you'd be hard pushed to lift a heavy rocket with fuel (still needed to escape gravity and the top of the atmosphere), never mind all the other things that are needed to launch it. And it's windy. Not so much at the surface because the air is so thick and drag against the ground. But as you go up you get stronger and stronger winds, while the atmosphere is still thicker than Earth. Then there are those clouds of sulphuric acid.

[Darkflame]

Well, in that case I guess Id go back to favoring orbital tethers of some sort.
Maybe you could still use balloons (and maybe even kite like effects?) to at least remove some of the weight of the cable when it hits the atmosphere so it has to support itself a bit less.

I generally think whereever your going you will need "easy" repeatable ways in and out of the planet. Anything else will end up being suicide. At least, for a long time.
Maybe thus comet colonies are the easier goal.

[zip accident]

The problem with balloons is they work by being lighter than air. Even though it's far denser than air here it's still air. So you'd be hard pushed to lift a heavy rocket with fuel (still needed to escape gravity and the top of the atmosphere), never mind all the other things that are needed to launch it. And it's windy. Not so much at the surface because the air is so thick and drag against the ground. But as you go up you get stronger and stronger winds, while the atmosphere is still thicker than Earth. Then there are those clouds of sulphuric acid.

You're right that it would be a one way trip, for a very long time.

If the temperature came down I'm not sure what that would do to the clouds of sulphuric acid, and that is a problem. However the mass of the atmosphere is mostly CO2, which plants break down to solid carbon and gaseous oxygen. It would be a very oxygen rich atmosphere for a while, but it would be much lighter (20x earth's at a pretty random guess?). Plants would take their time to do that, and we would have to wait while they did, but in such a rich environment their spread would be very quick.

What about using the atmospheric thickness as an advantage, and using balloons?

Balloons for living under maybe, for space launches, not a chance, they have most of the disadvantages of aircraft and are slower too.

Well, in that case I guess Id go back to favoring orbital tethers of some sort.
Maybe you could still use balloons (and maybe even kite like effects?) to at least remove some of the weight of the cable when it hits the atmosphere so it has to support itself a bit less.

Space elevators don't work on Venus, it's "day" is months long, so a venusian stationary orbit would be very high, maybe high enough to intersect the orbit of Earth or Mercury.

I generally think whereever your going you will need "easy" repeatable ways in and out of the planet.

Why? if the atmosphere is breathable for humans, there is food, and it's not poisonous, I don't see that at all.

Anything else will end up being suicide. At least, for a long time.

I disagree.

Maybe thus comet colonies are the easier goal.

Asteroids, yes. We ought to be living on space stations and perhaps asteroids for many years before Venus is ready. Comets tend to be ices, methane ice, water ice, ices of other things that are gases on Earth, so again problematically cold, with the added problem that they disintegrate if you do warm yourself up.

[pogo]

If the temperature came down I'm not sure what that would do to the clouds of sulphuric acid, and that is a problem. However the mass of the atmosphere is mostly CO2, which plants break down to solid carbon and gaseous oxygen. It would be a very oxygen rich atmosphere for a while, but it would be much lighter (20x earth's at a pretty random guess?). Plants would take their time to do that, and we would have to wait while they did, but in such a rich environment their spread would be very quick.

Plants depend on the environment being right as much as us. More so I would think: at least we have the advantage of locomotion. If plants don't get just the right conditions they give up and die, as any gardener knows. In nature other plants come in and take their place, as over hundreds of millions of years plants have evolved to occupy almost every niche. But none has evolved to withstand the conditions on Venus. For one it's too hot, much much too hot. The pressure is far too high, which is not just a direct problem for any cellular creature but it changes things such as the boiling point of water. It also changes the property of the CO2, so it's no longer a gas but a supercritical fluid.

Sure you could put a few plants in a reinforced, refrigerated, acid-proofed facility with artificial lights. But that's all you could do, shipping everything from Earth. Basically it would be so expensive it would never scale up. It would be like using a small greenhouse here to counteract global warming. Except again the atmosphere of Venus is so much more massive than that of Earth.

[zip accident]

Plants depend on the environment being right as much as us. More so I would think: at least we have the advantage of locomotion. If plants don't get just the right conditions they give up and die, as any gardener knows.

Those are usually plants from the wrong climate, or in an inappropriate niche. In their native habitat most plants are fairly hardy. These for instance:

http://arstechnica.com/science/2013/05/ ... taneously/

In nature other plants come in and take their place, as over hundreds of millions of years plants have evolved to occupy almost every niche. But none has evolved to withstand the conditions on Venus. For one it's too hot, much much too hot.

That's why I said we need to get the temperature down first.

The pressure is far too high, which is not just a direct problem for any cellular creature but it changes things such as the boiling point of water. It also changes the property of the CO2, so it's no longer a gas but a supercritical fluid.

Really, at 30 degrees C? I don't see it as much of a problem if that is the case, so long as the temperature is right.

Sure you could put a few plants in a reinforced, refrigerated, acid-proofed facility with artificial lights.

That is definitely not the idea.

But that's all you could do, shipping everything from Earth. Basically it would be so expensive it would never scale up. It would be like using a small greenhouse here to counteract global warming. Except again the atmosphere of Venus is so much more massive than that of Earth.

The idea would be to drop in some tough plants, and let them run riot, which they probably would do. You'd scatter seeds, and that would be it.

[pogo]

That's why I said we need to get the temperature down first.

The pressure is far too high, which is not just a direct problem for any cellular creature but it changes things such as the boiling point of water. It also changes the property of the CO2, so it's no longer a gas but a supercritical fluid.

Really, at 30 degrees C? I don't see it as much of a problem if that is the case, so long as the temperature is right.

You have a quite fantastic view as to how this would work. How do you get the temperature down first? It's hot because of the CO2, which caused and maintains a greenhouse effect. You need to remove the CO2 first. Then remove a stupendous amount of heat.

But even assuming that were possible the pressure really is a killer. Apart from crushing things it will make it hard to move and alter how many processes work, such as respiration of plants and animals. It blocks out light and by storing heat stops the temperature varying over the long days and nights.

One other problem: if the CO2 were converted it would be almost pure oxygen, under very high pressure, so very combustable. It really needs to be removed, but again you have to ask how? and to where?

[zip accident]

You have a quite fantastic view as to how this would work. How do you get the temperature down first?

I said, you put a shade between Venus and the Sun. It would be huge. Since it would be quite a long way out in space, the mass wouldn't be the problem it would be near a planet. There are probably all sorts of difficulties getting that right, and it would need to be adjustable so that it did a bit less after all the CO2 was gone. However, assuming that can be made to work somehow, less energy in, with the same level of energy coming out, means a lower temperature.

But even assuming that were possible the pressure really is a killer. Apart from crushing things it will make it hard to move and alter how many processes work, such as respiration of plants and animals. It blocks out light and by storing heat stops the temperature varying over the long days and nights.

In the seas of earth, pressures get vastly higher than those present in the atmosphere of Venus, plenty of living things exist in the deeps. Not many plants because there's not enough light, but life goes on a long way down. The sulpfuric acid clouds are more of a problem, the carbon dioxide is an opportunity for plants.

One other problem: if the CO2 were converted it would be almost pure oxygen, under very high pressure, so very combustable. It really needs to be removed, but again you have to ask how? and to where?

To oxides. Probably by combustion. It happened here in the Carboniferous, which was a long time ago, but lasted quite a long time too.

[pogo]

You have a quite fantastic view as to how this would work. How do you get the temperature down first?

I said, you put a shade between Venus and the Sun. It would be huge. Since it would be quite a long way out in space, the mass wouldn't be the problem it would be near a planet. There are probably all sorts of difficulties getting that right, and it would need to be adjustable so that it did a bit less after all the CO2 was gone. However, assuming that can be made to work somehow, less energy in, with the same level of energy coming out, means a lower temperature.

You know how huge? Many times greater than the planet: think how the Earth which is many times bigger than our Moon barely eclipses it (it sometimes doesn't when you get an annular eclipse). People have thought of this for Earth, as a solution for global warming, but putting up anything that would make even a small difference would be impossibly expensive and take too long. And that would be only to counteract global warming, which is raising Earth's temperature by a few °C.

For Venus you need to reduce the temperature not by a few °C but by several hundred. There is 93 times as much atmosphere so it stores 93 times as much heat per °C, while the greenhouse effect act to keep the heat in. Even if such a shade could be built I doubt it would reduce the temperature down to levels we could live in because of that greenhouse effect. But it can't be built – it would be impossible above Earth and so many times more impossible (if that makes sense) above another planet.

[Darkflame]

Space elevators don't work on Venus, it's "day" is months long, so a venusian stationary orbit would be very high, maybe high enough to intersect the orbit of Earth or Mercury.

If your not touching the ground, why would you need it to be geostationary?
I am thinking of a skyhock system - effectively flying into a hock and then being pulled up.

The question then is if the hock-up speed would be too much - not sure what maths would be needed to work that out. I'd guess ideally you'd end up with a "sling" effect, where the "forward" (around the planet) momentum is transfered to a upwards force.

Balloons for living under maybe, for space launches, not a chance, they have most of the disadvantages of aircraft and are slower too.

I was thinking a floating platform from which another craft launches from.

What disadvantages are you thinking of in this context?

I'm really just thinking from the perspective of "least energy to lift". That is getting as high as possible before you use a rocket, so that the fuel doesn't have to be wasted lifting itself.

Why? if the atmosphere is breathable for humans, there is food, and it's not poisonous, I don't see that at all.

Once a colony is established, sure.
I just think that will take a lot of time and big construction. Much easier if you can make round trips.
You don't want one decease outbreak to kill everyone off, for example.

Asteroids, yes. We ought to be living on space stations and perhaps asteroids for many years before Venus is ready. Comets tend to be ices, methane ice, water ice, ices of other things that are gases on Earth, so again problematically cold, with the added problem that they disintegrate if you do warm yourself up.

But they have water.
I think selectively melting water would be easier then constantly importing it no?

Heat can be generated from solar and controled to a large extent - but you cant pull water from nothing.

[pogo]

Space elevators don't work on Venus, it's "day" is months long, so a venusian stationary orbit would be very high, maybe high enough to intersect the orbit of Earth or Mercury.

If your not touching the ground, why would you need it to be geostationary?
I am thinking of a skyhock system - effectively flying into a hock and then being pulled up.

The question then is if the hock-up speed would be too much - not sure what maths would be needed to work that out. I'd guess ideally you'd end up with a "sling" effect, where the "forward" (around the planet) momentum is transfered to a upwards force.

The point of geostationary is it puts you above the same spot, so an object does not need to speed up to get on the lift. How much speed up otherwise? Orbital speeds for low orbits (around Earth but Venus is a similar size) are many km per second. Impossible on Earth as atmospheric drag stops you accelerating anything to such a speed, or if you try the object burns up (otherwise it would be easy to launch rockets: just accelerate them on a maglev in a vacuum then shoot them into space). Even more impossible on Venus where the atmosphere is much thicker.

Without geostationary you need to use rockets to stay above the same point, permanently burning them just to stay in place, burning them a little more as you lift something. Balloons don't get you out of the atmosphere (again we could use them on Earth to launch things into space if it were possible and saved energy).

[Darkflame]

The point of geostationary is it puts you above the same spot, so an object does not need to speed up to get on the lift.

Why would it need to speed up significantly? It doesn't need to chase the hock.
Your craft just needs a path that intersects the path of the hocks lowest point - it could be static (or traveling in the complete opposite direction) as the hock comes to meet it.

My query about the speed was more about the strain put on the craft/hock as they hit eachother. Or, in extreme speeds, even just problems caused by the hock-end heating up as it skims the atmosphere.

Obviously precision timing and aiming are needed. If we assume a parabolic flight path (like SpaceShipOne), then the hocks location would need to intersect the craft while its at the apex of its flight.

Balloons don't get you out of the atmosphere (again we could use them on Earth to launch things into space if it were possible and saved energy).

I know that, I was just wondering if (with a thicker atmosphere and thus more bounency) you could use it as a mothership on which to launch from, and thus save fuel.

So, you get up past a lot of the atmosphere, launch some sort of scramjet from the mothership, which intersects with a skyhock.

[pogo]

But something in orbit, especially parabolic orbit, is going at many km per second. Many times faster than a speeding bullet. The speed is similar to the speed of something in free fall from space, which is why objects burn up explosively when they fall even in the thin atmosphere. It can't go slower or it would fall due to gravity.

So intersecting with an object in orbit? Something like hitting it with a bullet, except many times faster. Given that energy increases with the square of the speed the outcome would be literally explosive.

[zip accident]

Hock:


Hook:


Earth orbital speed is 18,000 mph. Non-negotiable, anything slower falls to the ground.

[Absolute_Zero]

A theory of everything ... has physics gone too far?

Ultimately correct or wrong-headed, the winner of this little debate in the marketplace of ideas is pretty clear imho... the supposedly "fairytale physics" wins easily [debate-wise].

[zip accident]

A theory of everything ... has physics gone too far?

Ultimately correct or wrong-headed, the winner of this little debate in the marketplace of ideas is pretty clear imho... the supposedly "fairytale physics" wins easily [debate-wise].

I'm tending to think of it the other way around, if some of these quantum mechanical effects are real, anything might be possible, including magic.