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Old 08-13-2022, 07:57 AM   #61
Varyon
 
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Default Re: [Spaceships] Million Merchant Marathon

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Originally Posted by Fred Brackin View Post
They need to make the shades out of photovoltaic film so they an absorb that sunshine and use it to power the reactionless drve units that do the stationkeeping.
I believe photovoltaic films tend to be a bit too fragile for this task, but coating your metal (or whatever you opt to use) with such would be a good idea (or maybe this society knows how to make ultra-durable photovoltaic film). I was simply going off of scc's desire to have the surface be reflective.

Although I do wonder how Venus would appear in Earth's night sky with such a large, high-albedo "structure" up in its orbit. How bright would that be?

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Originally Posted by Fred Brackin View Post
The thrust units also need to be around the edges rather than in the center. You would need a stiff disc for a center mount. There'll be some extremely strong cables involved too.
Depending on what the minimum efficient size is for these reactionless drives, simply having several dozen small ones spread out over the inner surface may be ideal.
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Old 08-13-2022, 11:01 AM   #62
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Default Re: [Spaceships] Million Merchant Marathon

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Although I do wonder how Venus would appear in Earth's night sky with such a large, high-albedo "structure" up in its orbit. How bright would that be?
Depends how efficient it is. If all you're stopping is light that would have otherwise hit Venus anyway, any increase in brightness because of the structure would be paired with an equivalent reduction in brightness of Venus itself, so all that matters is the albedo of the structure as compared to the (already quite high) albedo of Venus.
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Old 08-13-2022, 04:04 PM   #63
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It's not technology that's stopping, it's politics. Europe trying to enforce environmental protection standards in Africa would go down about as well as Russia's current invasion of Ukraine.
What makes you think it would go that well?
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Old 08-13-2022, 04:35 PM   #64
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And they can’t spare a couple million robots to clean up Africa? Grumble grumble I’ll stop now.
Agreed. They have to experiment with terraforming anyway. It should be much easier to terraform the planet we have!
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Old 08-13-2022, 04:37 PM   #65
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I suspect that for brobdinagian purposes like terraforming you want to keep all of your terraforming machinery working as close to 24/7 as possible.
The problem is that all machinery (that we have built so far) requires preventive maintenance. Take things down when there is no window.
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Old 08-13-2022, 04:45 PM   #66
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As for reusing the cargo containers, they're going to need equipment to keep their cargo cool and now drives systems and this is a government program, not throwing away perfectly usable equipment is frowned upon.
Governments have created some of the most wasteful projects in existence.

And is it cheaper to reuse these cargo pods at their destination than by sending them back? If I had to put drives on those things it would be a very small and very low-thrust device. Or perhaps just a self-destruct (assuming you could design one that was fail safe).
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Old 08-13-2022, 06:44 PM   #67
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Most sci-fi also makes heavy use of superscience drives for a similar reason - with or without a human crew, transporting things through space with hard-science drives is boring. Even with superscience, transporting things through space is likely to be boring, unless something goes wrong.

I honestly have no issues with inefficiently using manned ships for this kind of stuff for the service of drama, although I suspect you're either going to either have things be fairly boring or will need to have interesting problems occur with strikingly-unrealistic frequency. If that's the campaign you want, go for it.
Well two things. Most, if not all, adventuring activity will take place in ports between cruises. Two, I've already decided that later on FTL travel will also be slow, so most spaceship crew will have Hibernation 9 and ships will carry stasis tubes for passengers who don't have that advantage.

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Ha ha ha ha ha ha ha ha ha ha ha ha ha ha *deep breath* ha ha ha ha ha ha ha ha ha ha ha ha ha ha!
EU and British Commonwealth, who are the primary backers behind this, seem to de a bit better. And one of the reasons this project got started was America imploding, so the American tendency to overspend is gone.

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Aluminum foil of standard thickness weighs around 4.5 kg per square meter, or 4500 metric tons per square kilometer. 44 million square miles is around 114 million square kilometers, so a sunshade consisting of nothing but that foil would weigh in at 513 Pg (513,000,000,000 metric tons). To put that in perspective, that's roughly 10,000 times the weight of the Great Wall of China. And you're going to have some inefficiencies due to it being made up of separate components, plus you'll need to add in the weight of the attached robots. Even if your reflective plastic is somehow lighter than such an incredibly-thin sheet of aluminum foil, you're talking about an absolutely massive edifice, here.

And, honestly, using some sort of metal may be a better option than plastic. Plastic requires that you either grow plants and turn them into bioplastic, or drill for oil to turn into more traditional plastic. Earth currently generates somewhere north of 340 million metric tons of plastic each year, so you'd need 1,500 years worth of modern plastic production to build your sunshade. Probably better to harvest your needed materials from asteroids - you won't find any oil, but there's plenty of metal to go around.
Well world production of aluminum foil is only 6 million tons, so that would take even longer to spin up then plastic.

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Originally Posted by Fred Brackin View Post
They need to make the shades out of photovoltaic film so they an absorb that sunshine and use it to power the reactionless drve units that do the stationkeeping.

The thrust units also need to be around the edges rather than in the center. You would need a stiff disc for a center mount. There'll be some extremely strong cables involved too.
Only need about a 10 square meter or so to power the robot, but photovoltaic film should be available, the ten years prior to starting this project was about getting Earth to use power satellites to supply it's energy needs.

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Agreed. They have to experiment with terraforming anyway. It should be much easier to terraform the planet we have!
Getting toxic chemicals out of soil is different then giving something an atmosphere or giving it soil at all.
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Old 08-13-2022, 07:23 PM   #68
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I
Depending on what the minimum efficient size is for these reactionless drives, simply having several dozen small ones spread out over the inner surface may be ideal.
Nevermind the drives. The disc has to be a weight-bearing structure (it's own weight) and a stiff disc will be either very small or very heavy.

The lightest structure for large sizes (like a mile or even kilometer across) will be a spider web of buckytube cables with a thin layer of either reflective or photovoltaic material transferring its' weight to the cable structure.

For strength and stabiility you "anchor" those loadbearing cables to thrust units at the cables' ends. Putting thrust units in the middle doesn't help.
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Old 08-13-2022, 08:56 PM   #69
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Aluminum foil of standard thickness weighs around 4.5 kg per square meter, or 4500 metric tons per square kilometer.
Standard thickness for what? The density of aluminium is 2 700 kg per cubic metre, so foil that massed 4.5 kg per square metre would be 1.67 mm thick. That's chonk foil.

I weighed a roll of aluminium foil in my kitchen. Net of the box and the cardboard core it's rolled up on, a 30 m by 30 cm roll (9 square metres) massed 343 g. That is 0.038 kg per square metre. 38 tonnes per square kilometre.
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Old 08-14-2022, 12:26 AM   #70
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Nevermind the drives. The disc has to be a weight-bearing structure (it's own weight) and a stiff disc will be either very small or very heavy.

The lightest structure for large sizes (like a mile or even kilometer across) will be a spider web of buckytube cables with a thin layer of either reflective or photovoltaic material transferring its' weight to the cable structure.

For strength and stabiility you "anchor" those loadbearing cables to thrust units at the cables' ends. Putting thrust units in the middle doesn't help.
Well this thing is probably some sort of drive field design that applies thrust evenly across the entire surface opposing the direction of thrust, if not the entire structure/vehicle. And I think you'd need something more structurally sound then buckytube cables, just to hold it all together.

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Standard thickness for what? The density of aluminium is 2 700 kg per cubic metre, so foil that massed 4.5 kg per square metre would be 1.67 mm thick. That's chonk foil.

I weighed a roll of aluminium foil in my kitchen. Net of the box and the cardboard core it's rolled up on, a 30 m by 30 cm roll (9 square metres) massed 343 g. That is 0.038 kg per square metre. 38 tonnes per square kilometre.
This would mean it would require 4.3 billion tons for the whole thing. Probably going to have to increase output or it will take 600 years to b.uild
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