Never Exploit Venus & Mercury: A Pity for the Solar System

[Algr]

Mr Richfield, If you want people to take your ideas seriously you need to learn to have some respect for your audience. First the termites and monkeys, then you devote a whole paragraph to a typo that anyone ought to see means "angular momentum".

It should be obvious that my "planet" is simply a series of space stations. We've already built space stations, so arguing that they aren't feasible makes you look a bit silly. Mining asteroids for materials is not something I invented, and as for energy, how about focusing sunlight? (No we don't need the whole station molten at once. Sheesh.)

As to your plan: The moon reaches 200 degrees on it's day side. A tidally locked venus will have habitable temperatures only on a narrow twilight ring. And what will happen to geology when ground that has been at 800+ degrees for millions of years starts to cool down and contract? (Especially on the night side?) What will those earthquakes be like?

And finally there is your timescale. In 1000 years if we aren't extinct, we will have manned missions to many other solar systems. Is it likely that we won't find anything better to start with then venus? It is pointless to make plans with no payoff for a millennium when humanity changes as fast as it does.

 

[Jon Richfield]

Im on my phone so it was auto text trying to tell me what i wanted to say.

Ah! Well that is a relief. I had been wondering at what level to pitch the response. I seldom use a cellphone and avoid auto for exactly that sort of reason, so that explanation had not occurred to me. It did not look like finger trouble, so I got the impression of scientific illiteracy and I thought I was in real trouble. Welcome back to the world! At least we now can talk sense at each other.

You want to alter the rotation of the planet, aka change its angular momentum. Where it goes / comes from is irrelevant. Changing it isn't as easy as you are making out.

Where it goes to or comes from is extremely relevant. It is crucially relevant. Even your cellphone could tell you that if you spin it. If I had proposed that we correct the planet's spin by getting a lot of marathon runners to accelerate on the equator, then you might have a point. After all, we would lose the adjustment to the angular momentum every time one of them stopped for a rest. If instead I had a lot of really humungous flywheels accelerating near the poles, you might be at a slightly smaller advantage, because I could have the flywheels spinning in a vacuum on magnetic bearings. I might even tune them to achieve permanent changes to their system's angular momentum by electromagnetic interaction with the ambient magnetic field of the solar system. But I think you will accept that option is unattractive in engineering terms, so I would not push it too hard if I were you; always aim for practicality, I say, and you see JJ, those flywheels would have to be really huge, the ambient field is very weak, and above all, every joule equivalent of the planetary angular momentum would have to be generated locally.

We could not afford that JJ, so where we are to get it from is indeed relevant in the highest degree.

You see?

OTOH, changing the angular momentum is as easy as I make out. It is exactly, precisely as easy. No more, no less. Work it out. Any mass at a given (linear) momentum striking the planet on a given trajectory will affect its angular momentum by exactly that product of its mass and velocity in vector addition to the orientation of the planet's spin. One makes certain allowances for atmospheric and pedological factors of course, but what else is new?

Unless of course you know different! Do tell us if so!

Are you seriously telling me you know a way to pilot an asteroid, 10km in diameter, into a slingshot around venus, let alone consistently 80000 times?

Well, actually I wouldn't insist on the 80000 figure, because I have a sneaking suspicion that the Kuiper belt is not set up for our convenience as an array of conveniently standardised 1e12.5 tonne blocks, so let's work on a basis of 100000 times. 80000 is such an awkward number, isn't it?
But BTAIM, no, although I could do that (in principle) it would be pointless most times, wouldn't it? For a start it would not affect the planet's angular momentum, would it?
No, the idea would be to strike the appropriate limb of the planet solidly. Would you settle for that? That would affect the planet's angular momentum, right?

It isn't down to me to come up with ways for your plan to work, you want to claim it can be done, you tell us how.

JJ, I already have someone coming down on me for not being nice enough to you. I don't need you to tell me of at least one way in which it can be done, but for me to tell you would really smack of excessive patronism, don't you think? Besides, who knows, with your skills maybe you could propose something really different and original (my approach is creakingly pedestrian, I am sorry to say!) So let's leave it at that for now. When you find yourself stumped, let me know and I will help you out of your difficulty and explain some of the hazards of trying to assert and support a negative.

How about you cite a source for piloting asteroids or changing the angular momentum of a planet as per pf guidelines?

Ah yes! Silly me! I had not read on far enough when I keyed in the previous paragraph. Oh well, to help you on your way, any school physics textbook this side of the antidarwinistic bible belt should give you ample material on angular momentum and momentum vector arithmetic. Let me know when you get stuck, but please organise your questions first. Firstly, that way you will find yourself able to answer many of them yourself, and far more profitably than having me do it for you. Secondly, I don't have the time for too much stuff that your teachers should have told you already.
It might however, speed you on your way if I suggested that steering any solid body in space follows the same general rules, and that some of us have managed pretty well already.
Yes?
Go well!
Jon

 

[Jon Richfield]

Mr Richfield, If you want people to take your ideas seriously you need to learn to have some respect for your audience. First the termites and monkeys...

Mr Algr, Thank you condignly for your concern and correction. I find myself however at something of a loss to excogitate the significance of your apparently resentful preoccupation with primates and termites. Would you please explain whether and how you read anything offensive into that analogy; and in fact whether you understood the parallel at all? I hardly expected to have to spell out anything of that kind in this forum! As a helpful hint, avoid invoking stereotyped behaviour; it patently is not your field of expertise.

...then you devote a whole paragraph to a typo that anyone ought to see means "angular momentum".

A typo...? Al, you leave me breathless. Not only could anyone see what it meant (assuming that they knew what angular momentum was, which btw, most people don't, even including some in this forum!) but I did too. I even helpfully supplied the correction, remember? Free of charge! What is more, as typos go, it was rather misleading. If it had been "agnular" or "angilar" or "angulr" or "anngular" I would have passed it by as I do with all the usual stuff. You don't perpetrate anything of the kind of course, but I certainly do, or worse. You might find it instructive and even entertaining to read Laurence Durrell's "Frying the Flag".

So AL, try it from my perspective: JJ writes a rather curious argument suggestive of difficulty with the arcane concept of conservation of angular momentum, and spells it so hopelessly wrongly as to suggest that he had never seen the word. From this I am to deduce that he does indeed know what he is talking about and that he was betrayed by his cellphone?

Well, he took it in good part and pointed out that the error was indeed trivial and understandable, so that was that. We sorted it out in one exchange. But what your role in this might be, I am not so sure.

It should be obvious that my "planet" is simply a series of space stations. We've already built space stations, so arguing that they aren't feasible makes you look a bit silly.

It should indeed be obvious. It was so obvious to me that I could not understand why you were having difficulty with the concept. Silly, silly me, as you point out, if only I had in fact said that no such thing as a space station were feasible. Which please note, I had not. (Mind you, I would hesitate to point to our only extant specimen of a space station as a counterexample )

But Al, it is simplistic to classify a planet as a space station or a space station as a planet, as if the two were in general interchangeable, simply because they share certain orbital characteristics. You might well find it to be a wholesomely sobering exercise to sit down for a few hours and draw up a list of the respective attractions and functions of orbiting bodies of different orders of magnitude. Start with say something tiny, perhaps a few dozen times the scale of the Space Station. Then try something a few km across, say something like Phobos. Then something like Ceres. Then Mercury. (Good one Mercury!) then Venus (Great one Venus! For termites anyway!) Gas giants? Hmmmm... Well think about them anyway. Good stuff thinking. Pity it hurts so, isn't it? Worse than gym time!

If you do your assignment properly, you should be astonished at some of the implications and prerequisites that emerge.

Mining asteroids for materials is not something I invented, and as for energy, how about focusing sunlight? (No we don't need the whole station molten at once. Sheesh.)

You never invented mining asteroids for materials? I thought everyone had done that at one time or another. Oh well. But you know, you really need to do better than that if you want to stop confusing issues, which is a great waste of energy and intellect. If we want to mine asteroids, we can do that a lot more cheaply than moving them into new orbits and melting them and forming them into rings and attaching domes and all that. All we need do is go to where they already are, assess their value, and send out some automated mining equipment to retrieve whatever we happen to want, and leave the unwanted bits where we found them. If we discover that say, Themis is 50% osmiridium, such a project might be worth while, but anything much less dramatic than that is not likely to be attractive, certainly not in comparison to what we could do on a planet of our own, such as Venus. (Notice that moving Themis into a more convenient orbit so that the application of solar heat would become attractive, would be a project that would dwarf the challenge of adjusting the rotation of Venus.)

Now, just what do you expect to mine from your "planet" once you have assembled it and melted it and all that Good Stuff? All several trillion tonnes of it? How do you expect to make a viable proposition of it? What would Earth profit, and what would that artificial space station present as a self-supporting environment to long-term occupants? Mining? Agriculture? Fabrication? Energy? Fundamental research? Population space? All of those perhaps, but I really would like to see you spell it out cogently. Please! Something better, and with a better rationale than piecemeal solar energy fusion of asteroidal or meteoritic rock! OK?

Eish...!

As to your plan: The moon reaches 200 degrees on it's day side. A tidally locked venus will have habitable temperatures only on a narrow twilight ring. And what will happen to geology when ground that has been at 800+ degrees for millions of years starts to cool down and contract? (Especially on the night side?) What will those earthquakes be like?

Uh... I don't suppose you mean Kelvin? Rømer? Celsius? No? Then I suppose you mean Fahrenheit. Right? Tsk tsk... Oh well.

Al, did you notice that the primary rationale of the scheme depended on first giving Venus an atmosphere roughly comparable to that of Earth? Did you really think that this would have no effect on the surface temperature? Please justify your assertion, if so. If not, what would you expect to happen to the temperature on various parts of the surface of Venus?

Only a narrow twilight ring you say? Forgive my pointing out that you have a facile way of using qualitative terms to assert quantitative propositions. Note that firstly, if that ring of living space were only a few km wide, it would dwarf anything that you could assemble in space. If it were just 250km wide (very narrow, right?) it would be about 10000000 square km. Secondly, solar intensity at the orbit of Venus is only about twice that on Earth, and the angle of the sun to the horizon would be of great relevance, so actually, about the outer half of dayside, the face of the planet facing the sun, should be very livable; even the inner bullseye with the sun at its zenith would be perfectly liveable with a bit of shading and solar power. It would be a fabulous region for industrial real estate. After all this is Venus we are discussing, not Mercury ! Also please note that dayside is about double the land area of Earth.

Oh yes, the earthquakes... well quakes anyway. Frankly, I am unthrilled. There might well be quakes, but I suspect that our 100000 dino-killer impacts would have shaken up most impending quakes for a start. Also, Venus seems to have very little in the line of tectonic activity. The rate of cooling by conduction from underground to the surface would be very modest indeed. Even the heat content of soil 100m subsurface would show very little change in 1000 years. The nightside glaciers would cause far more quake activity, but then who lives nightside anyway? If at the time we begin to move in and settle, we find that quakes are troublesome, we simply adapt our building techniques. I was tempted to invoke the super-science of our descendants that you and JJ set such store by, but most of the quakes, if they are caused by cooling, would be horizontal S and P waves; easy to build for even using our current primitive techniques, right?

And finally there is your timescale. In 1000 years if we aren't extinct, we will have manned missions to many other solar systems. Is it likely that we won't find anything better to start with then venus? It is pointless to make plans with no payoff for a millennium when humanity changes as fast as it does.

"If we aren't extinct..." well, since we are not termites that is a large assumption, I grant. I frequently am surprised by the fact we have made it as far this. But 1KY is such a vanishingly short period that if we can't survive it, we hardly matter.

But really Al... Other solar systems...

You know, I actually am all in favour of expeditions of various kinds to other solar systems, but there is no reason other than idealism even to contemplate them! 1KY? Suppose we consider a confirmed, suitable planet at 10 LY away (adjust my figures to suit your argument, but if you reckon on a nice, cosy 'ole at 1 LY away, I'll want to know where you get your data from!) That is about 1e14km, right? Suppose we can get a suitably sized colony ship up to an average speed of 1000 kps (tell me when you have worked out how to do that and how much fuel you would be taking along and what speed you would expect to achieve en route! Bussard jets? Tell me more! Lots more!)

That leaves us with a journey of a mere 1e11 seconds or about 1e3.5 years. OK? Never mind the preparation, the sales talk and politics etc, just the 1-way journey would take well over 3000 years. Not 1000, 3000!

Eh?? Who said "Round trip"? Over 6000Y? Not counting settling-in time?

Now, the Venus/Mercury/Asteroids schemes should offer at least certain advantages while they were under way, and huge rewards thereafter, but just how do you expect to get material (as opposed to ideological) rewards from your interstellar schemes? Trade? Emigration?

Sorry Al, but someone said something to the effect that if there is something you cannot do anything about, then it isn't a problem; it is reality.

It really is! There is a lot of reality to our corner of the universe.

Jon

 

[Algr]

This is the kind of discussion that can have no end, so I'm not going to bother...

 

[JaredJames]

This is the kind of discussion that can have no end, so I'm not going to bother...

Agreed. I think I'll give it one last shot and then I'll see if it's worth continuing.

Mr Richfield, you want to alter the angular momentum of a planet. Yes, your technique would work. I have never denied that, however you are failing to understand that getting to the point of changing the rotation is the problem. Piloting an asteroid into a slingshot around the planet isn't easy and so far you haven't proposed a way to do it multiple times. Unless you are willing to share how to accomplish that feat, it stands that we simply don't have that capability.

That is why I'm saying where it comes from / goes to is irrelevant. We can give all the ways we like to change the rotation of a planet (or do anything) but if we physically cannot achieve them (by means of flying asteroids around / into a planet or otherwise), they really are useless ideas to us until the technology becomes available. (And at the point it does, if we still want to use it for that purpose.)

Despite your lovely long response, you still haven't provided a way to actually send an asteroid from the belt to Venus. As above, any concept you provide after that is meaningless unless you can explain how we get over that massive hurdle.

There are no school physics books which discuss asteroid piloting. My argument isn't with your angular momentum issue. It is with getting to changing the angular momentum.

Despite the main point of my last post asking you to tell me how we get asteroids to Venus in the first place, you still haven't responded with regards to that.

At the moment it looks as if you've provided an idea and then expect everyone else to fill in the blanks as to how we achieve it. It's no different to me giving an idea regarding the use of a perpetual motion machine but not explaining how we get the PPM. I can go into great detail about how we use the device but constantly avoid describing how to achieve the device itself, expecting others to actually come up with the device for me. This is simply not how things work and a bad way of discussing a topic.

This is the last chance I'll give you to explain the following:
a) How we get asteroids from the belt to Venus.

 

[Jon Richfield]

This is the kind of discussion that can have no end, so I'm not going to bother...

Very prudent Al, very prudent. The simple reason that you made no headway is that you had chosen to fight facts. Fighting me would be no problem, because I had nothing to fight about. All I had was facts. Facts have a nasty way of not fighting back. Facts don't care.
Even verry, very simple facts like:

* How long it takes to reach the nearest habitable planet in another solar system
* The logistics of getting there (and back)
* Viable space dwellings do not simply assemble themselves to order
* Space dwellings have functions largely different from planets
* When you start an object moving in space, it takes energy to stop them when they arrive
* More generally, the conservation of momentum and of angular momentum
* Still more generally, the conservation of energy
* Even with solar power, it is not trivial to melt just any old rock to build functional dwellings in space just anywhere
* Not even because Al says it is simple.

Ohhh... and a job lot more. You didn't really get to to first base with any of them did you?
I tell you Al, facts are mean, so mean that I blush to invoke them.

And what did you have?

Sorry about that!

But I'll be around if you return with any facts. Maybe you had better get help. You probably could scare up a friendly space engineer somewhere online.

Cheers,

Jon

 

[D H]

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