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So, I read on the net the other day that one method of delivering water while terraforming Venus (this is assuming the problems of day length and sun exposure are sorted out) is to bombard the planet with hydrogen which reacts with the co2 atmosphere to produce water and graphite.

The article I read this on suggested using hydrogen from Jupiter, but in my project Jupiter has already been claimed by another state looking to terraform Ganymede, so the Venus terraformers use a Bussard ramjet field to “harvest” hydrogen from the atmosphere of the sun, where it is then delivered to Venus. The problem of getting the ramjet close enough to the sun is, I figured, not an issue since it can be placed at a distance and the electromagnetic field is extended for the rest of the way.

Is this plausible? I can’t find a problem with it myself, but I want to be sure.

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  • $\begingroup$ By all appearances, you're not thinking dramatically enough. In your story, the majority of scientists-engineers reckon sun harvesting is a dandy idea. But there are significant objections from a minority. The majority wins, the project is approved, the hydrogen is harvested, Venus is transformed! At the "ribbon cutting ceremony" where humans are standing on the surface of Venus under blue skies, someone looks up and asks "Is the sun supposed to be that colour?" (or massive flare storms or whatever aftershock results that rattle the story) $\endgroup$
    – Blaze
    Oct 9, 2022 at 17:11
  • $\begingroup$ You''d need to get inside to harvest meaningful amounts. I wonder how one would harvest hydrogen from a star without the cargo exploding underways :o $\endgroup$
    – Goodies
    Oct 9, 2022 at 21:59
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    $\begingroup$ Both the Sun and Jupiter are so large that either could terraform many Venuses and Ganymedes. If Jupiter is easier to use, then both should share (or a war should probably be fought over it). $\endgroup$
    – John O
    Oct 10, 2022 at 15:29
  • $\begingroup$ @Goodies The Space Hinderberg should just make sure that the mooring ropes aren't wet and those won't conduct a static charge to the hydrogen, obviously. $\endgroup$
    – John O
    Oct 10, 2022 at 15:30
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    $\begingroup$ "Jupiter has already been claimed by another state looking to terraform Ganymede": A mosquito bites an elephant. A second mosquito sees it and thinks, that elephant has been claimed by another mosquito: I need to find myself a different elephant. $\endgroup$
    – AlexP
    Dec 31, 2022 at 20:24

3 Answers 3

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In 1971, MIT students at the World Science Fiction Convention roamed the halls chanting, "The Ringworld is Unstable!" Larry Niven fixed the problem using Bussard Ramjets along the rim of the Ringworld. O'course, that wouldn't work, either...

And that's why you should ignore everyone and stop seeking confidence to use a perfectly good suspension-of-disbelief solution.

If you ask a group of engineers or scientists whether or not a sci-fi idea is plausible, you will always be given sheets of paper explaining how it can't be done.

  • During the 1990s when I was working as an Electrical Engineer designing one-micron geometry BiCMOS circuits it wasn't just believed that nanometer MOSFET geometries were impossible — we knew it. Why do I have trouble with the phrase, "follow the science!"? Because I've lived long enough to know it's not that trustworthy. 1990s science knew that nanometer geometries were impossible. Until 2016 when researchers at the Lawrence Berkeley National Laboratory created the world's first 1nm gate.

Conclusion

I love your idea. It has scientific backing in the form of using hydrogen (regardless of its source) to create water on Venus. Your story can't use Jupiter, which is a honking long way away anyway! A ring of Bussard Ramjet platforms casting a series of hydrogen streams past Mercury and into the path of Venus' orbit is uber cool!

Use the information you read on this Stack to load your story with interesting facts, but don't rely on any of it to tell you wat not to do. Write that story, dude. If Larry Niven can use Bussard Ramjets to stabilize the Ringworld (way, way, way too far away from the sun!) then you can use them to bring water to Venus.

Cool idea!

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  • $\begingroup$ Sometimes we just have to suspend disbelief because the idea is too cool not too. It's a fine line though... if the science is bad enough I'm just not going to be able to get past it. Star Wars I can accept as just a swords and sorcery epic in a dollar-store SF halloween mask, but I kind of draw the line at flying space fighters around like F-18s. Space fighters don't swoop, and the don't make cool noises as they zip past. $\endgroup$
    – Corey
    Oct 10, 2022 at 0:33
  • $\begingroup$ @Corey I get your point - but unless you intend to be the only person who ever reads your story you need to think about your audience. Even The Expanse, likely the most scienfically TV show to date, had to give into the reality that the best educated and least-likely-to-suspend-their-disbelief audiences get bored when epic space battles are presented in silence. I love this idea, but it has some major problems from a science standpoint. Problem #1 is Mercury because your ramjets would need to be inside its orbit to be effective. (*Continued*) $\endgroup$
    – JBH
    Oct 10, 2022 at 4:47
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    $\begingroup$ #2 is dispersion. Keeping the stream together for tens of millions of miles shouldn't even be mentioned in your story. #3 is quanity. You'd need either ramjets so large that the need to move hydrogen from the sun using them is a technology dichotomy or so many that the resources needed to make the project happen violates economic common sense. The price you pay for trying to achieve "real science" stories (not an uncommon effort on this Stack) is pretty high because for a good story your audience will forgive any scientific weakness and for a bad story they won't care how good your science is. $\endgroup$
    – JBH
    Oct 10, 2022 at 4:51
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    $\begingroup$ I was agreeing with you about the cool factor overriding some of the problems. Just pointing out my pet hate for bad space fighter portrayals. And time travel. Oh, and mysteriously unexplained artificial gravity that nobody ever comments on. And... ok, so I have a few pet hates :P $\endgroup$
    – Corey
    Oct 10, 2022 at 9:43
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    $\begingroup$ @Corey Independence Day is my shameful love-it-though-I-oughtn't movie. I think it exemplifies the principle of "fun blinds people to faults". $\endgroup$
    – user86462
    Jan 1, 2023 at 9:45
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No. This is absolutely not practical. The solar wind is far too low density to be useful on this scale.

The solar wind is round-about $7.5 \times 10^{12}$ particles per square meter per second at the Earth's orbit. And a little less than twice that at Venus's orbit.

The atomsphere of Venus is 92 Atm. pressure and 96.5% CO2. This means about 1450 moles/m$^3$, roughly $8.6 \times 10^{25}$ molecules per m$^3$.

It means that each square meter of your collector requires about 184 thousand years to convert 1 cubic meter of atmosphere at surface level. A collector with the same diameter as Venus would require (since the area of a sphere is 4 times the area of its cross section) 3/4 million years to convert the bottom meter of the atmosphere of Venus. Assuming you could get 100% efficiency.

And as a reality check, note that Venus has been there for about the same time as the rest of the solar system, some 5-ish billions of years. And the solar wind has been spraying on Venus that whole time. And Venus is still jam-packed with CO2.

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    $\begingroup$ Looked up how close could we get to the sun; The Space shuttle reinforced carbon-carbon heat shield is designed to withstand temperatures of up to 4,700°, if the shield wrapped the entire shuttle, it could fly within 1.3 million miles of the sun. Saturn is 886 million miles from the Sun. Surely getting 680 times closer would change this calculation; based on surface area enclosed at 1.3M miles and 886M miles, hydrogen concentration should be ~316 million x greater at 1.3M. Assuming it can be transported, instead of 3/4 million years, you'd be looking at less than a day, not 750,000 years. $\endgroup$
    – Amadeus
    Oct 7, 2022 at 19:27
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    $\begingroup$ user98816 states in their question harvest from the atmosphere of the sun. So this answer seems to not address what they have suggested? $\endgroup$ Oct 8, 2022 at 2:09
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    $\begingroup$ @Amadeus Even starting at Venus' distance, it costs significantly less delta-V to escape the Solar system than get within 1.3 million miles of the Sun. on a Hohmann transfer. From a high circular orbit, getting near the surface of the sun requires killing nearly all your orbital velocity, and escaping the solar system only requires increasing it by about 41%. $\endgroup$
    – notovny
    Oct 9, 2022 at 15:52
  • $\begingroup$ @notovny The point is not to escape the solar system, but to blow hydrogen into the orbit of Venus. We don't need the Ramjets back, they can orbit the sun and eventually crash into it; they just need to accelerate the hydrogen. Even if we position them 10M miles from the sun, the concentration increases 700,000x and shortens the collection to 13 months or so. Nothing is intended to "escape the solar system". $\endgroup$
    – Amadeus
    Oct 9, 2022 at 20:53
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Looked up how close could we get to the sun; The Space shuttle reinforced carbon-carbon heat shield is designed to withstand temperatures of up to 4,700°, if the shield wrapped the entire shuttle, it could fly within 1.3 million miles of the sun. Venus is 107 million miles from the Sun. Surely getting 82 times closer would change this calculation; based on surface area enclosed at 1.3M miles and 107M miles, hydrogen concentration should be ~942 thousand x greater at 1.3M. Assuming it can be transported, instead of 3/4 million years, you'd be looking at about 10 months, not 750,000 years.

And that is with existing materials, used on the Space Shuttle. If you take some minor liberties with future shielding technology, you could probably get the Ram jets much closer to the Sun.

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    $\begingroup$ Why is the orbital radius of Saturn relevant? The answer that you were originally commenting on with this one was talking about collectors near the orbit of Venus, not Saturn. $\endgroup$
    – Ben
    Oct 10, 2022 at 1:37
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    $\begingroup$ @Ben !!! Wow, I screwed that up! Corrected. The idea works, not as dramatically, but with Venus closer, the collection time is still reduced to about 10 months, which I consider quite feasible. $\endgroup$
    – Amadeus
    Oct 10, 2022 at 9:31
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    $\begingroup$ The heat from the sun is all radiative. You only have to deflect the IR radiation or cast a shadow to shield the hydrogen collect-ifying thingy. Like Mercury, the hot side is very hot, but the night side is still space cold. $\endgroup$
    – Gillgamesh
    Oct 10, 2022 at 13:22
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    $\begingroup$ How to transport that much hydrogen collected this way would make a great question. $\endgroup$
    – Gillgamesh
    Oct 10, 2022 at 13:23
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    $\begingroup$ @Amadeus Or you could use Mercury it's self? using your calculations how much hydrogen could mercury collect? They could pack it into mud balls (Mix the hydrogen into a more stable compound, encase it material mined from Mercury) throw them outward, using mass driver, into a catchment orbit of Venus to be recovered and reprocessed. Bonus they get to keep the encasing material for building more infrastructure, Mercury is rich in heavier elements. $\endgroup$
    – Gillgamesh
    Oct 10, 2022 at 14:02

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