A Dead Space Age Worldbuilding

>Me, I am thinking folks are overselling the importance of gravity just a wee bit.

I mean, we don't let astronauts live on the ISS for very long and they have to keep up a training regimen to keep in shape, and they're still pudding when they come back. Moon or mars bases have never gotten beyond the paper stage, but even then the moon has at least some gravity. We can get there in 3 days, so if staying on the moon for a year also makes you pudding we can just send people home. Mars has roughly 40% earth gravity, but we have literally no idea what that does to a human body long-term.

Other problems involve things like childbirth, but that's hardly going to be an issue to NASA.

It's not discussed as a problem because, well, we're nowhere near a situation where it will be.

Yeah, it's definitely a problem if they ever want to come back.

As for rotating habs, there is no reason why they necessarily have to be any bigger or more massive than the non-rotating kind. You just need a module at one end and a counter-weight at the other.

Edited by DeMarquis on Nov 19th 2020 at 3:55:49 PM

If you want a lot of people to spend a lot of time there, they need to be much bigger than the ISS.

That would be true of any space station, not something that is inherent in a rotating hab design.

A rotating hab has a bigger minimum size. If the ISS were to be spun up, the astronauts would puke their gut out.

I make use of this thing to calculate that.

Minimum radius needed is 224 meters spun at 47 m/s to generate about 1 G of gravity according to this calculator.

Sorry, but the smallest (and so far, only) rotating spacecraft ever built was a Gemini capsule. You all are assuming some sort of fully functioning permanent habitat and I'm just assuming an experimental design for research purposes, and secondary functionality as a storage facility and base of operations.

That's like assuming the first space launch has to be on a Saturn V.

That is, however, a pretty nifty calculator. I know from independent sources that you can go down to 100 meters radius if the inhabitants can tolerate 3 rotations per minute, and the calculator confirms that! Cool. Of course, the whole purpose of an experimental rotating hab is to vary the gravity and observe the effects.

Edited by DeMarquis on Nov 22nd 2020 at 9:50:14 AM

No, you've been talking all along about permanent space habitats. It's kind of your thing. Sure, we can experiment on a smaller scale, but for people to actually live in space long-term under simulated gravity, we need a very large structure.

Yes, rotating habs in space is sort of my thing, but it obviously will take incremental steps to get there. I'm not expecting to start with the space station from 2001.

On the other hand this isn't all that hard: the ISS has about the same internal volume as the cargo capacity of a Space X Starship— so take one, put it on a tether with a counterweight and rotate it, if you want that. On the other hand, the Lunar Gateway was only going to have 125 cu meters internal volume, so that's even easier.

Edited by DeMarquis on Nov 22nd 2020 at 9:55:53 AM

The main topic was a universe in which the system is already colonized. I would expect the whole initial phase of rotating habs to be over.

Like, the main point of a space station is to have an actual function, not to be an experimental piece. Slinging with a counterweight is fine if your capsule needs some gravity in transit but it's useless for any sort of serious hab. And with the main topic, we're talking about long-term to permanent habs.

Regarding the calculator the sources seem to vary. The upper bound of angular velocity seems to be about 6rpm. A radius of 25 meter seems to do in that case. Though it might come with big side-effects.

Anyway, a rotating hab would probably be more difficult to deal with than a non-rotating hab, and the slower it turns the easier to deal with. Seems to me that people will try to get away with as little as possible unless there are stringent requirements.

Edited by devak on Nov 22nd 2020 at 11:16:49 AM

We did get a little off-topic, although this isn't the On-Topic forum. And while I would agree that stations should have functions, it's also true that you can't develop a new technology without experimenting. However, that said...

"Slinging with a counterweight is fine if your capsule needs some gravity in transit but it's useless for any sort of serious hab."

Oh? Why? A rotating hab with a counterweight is simply a rotating hab with the living and working modules all on one side. How does that impair it's purpose? It seems rather to me that it facilitates it, by allowing everyone to live and work in interconnected modules, exactly as they do on the ISS now. If we do develop rotating habs (and I think manned interplanetary exploration will require it) then tethered counter-weights seem more practical to me than ring or cylindrical designs, at least at first.

As for the speed of rotation, the downsides are greater structural forces on the tether, possibly greater difficulty docking with it, depending on exactly how what technique they end up using, and greater coriolis forces within the hab. The research papers I have read indicate that 3rpm and a 100-200 meter radius might be the "sweet spot" where all the various advantages and disadvantages are balanced against each other.

Edited by DeMarquis on Nov 22nd 2020 at 7:01:55 AM

A 100 to 200 meter radius easily gives us that figure of several thousand tons that I was talking about earlier.

Anyway, it's veering off of the point being discussed, which is how all of that could collapse from Earth's side, and where I went with it was, "What is the current technological state that would allow for colonized worlds, asteroid mining, space habitats, and so on yet would be susceptible to being cut off due to some disaster or strife?"

The common element these all need is cheap, efficient transport from Earth's surface to orbit. With current technology and materials science, that means a rapidly, completely reusable spacecraft like Starship capable of flying thousands of trips per year and/or a skyhook (not a space elevator). It means orbital fueling stations, ISRU everywhere possible, and so on.

It seems likely that with cheap orbital transportation, we'd have figured out a solution to Kessler syndrome: there are already proposals being tested. It's improbable, therefore, that something like that would abruptly cut off all launches above LEO. We'd already have the resources in place (or readily available) to handle it. It might be a short-term hazard, though.

Similarly, local or regional problems wouldn't kill all access to space. By the time it's mature, Starship should have dozens of launch and landing facilities all over the globe, many of them self-sufficient (they can manufacture their own propellant from locally generated power). No one nation could cut off space for everyone. Even if we had a skyhook, it wouldn't be the only way to get to orbit; the risk would be too obvious. The problem would have to be global in scale.

So, what are some actual options? Here we can go back to science fiction. The novel Friday by Robert A. Heinlein supposes that most industry comes to be owned by a Ultra-Super-Giga-Corp named Shipstone that suffers a wave of infighting, manifesting as "terrorist" attacks across the globe. Terrorism on a sufficiently large scale could significantly impact spaceflight and space operations in general, much like the Sept. 11, 2001 attacks shut down most global air travel. This is a fundamentally temporary event, though.

A global depression probably wouldn't do it, because space transport would be (a) a source of high-tech jobs that should survive a demand shock, (b) considered essential by most governments to sustain infrastructure and military programs. A global war, on the other hand, might well do the trick, especially if it involves shoot-downs of rockets or anti-satellite attacks.

An ideological shift that makes everyone suddenly freak out and abandon space travel seems unlikely. The entire planet wouldn't do something like that all at once. An uncontrolled pandemic, on the other hand, could absolutely shut down non-essential space travel, and in that case the colonies and habitats would be the ones yelling at people to stop coming when they might carry a deadly disease.

A meteor impact seems unlikely. For one thing, there just aren't any big ones that are sufficiently likely to hit Earth in the next century, and for another, as we expand into space our ability to detect and prevent such events would only increase. A powerful solar event, on the other hand, could easily cause enough infrastructure damage to shut down space travel for a significant length of time.

Edited by Fighteer on Nov 22nd 2020 at 7:54:19 AM

Alternatively, you can have an interplanetary war that causes the demise of the space age like what I'm doing with my own worldbuilding for my Light Novel. Say such a war becomes so bad, it leaves Earth a social and economic wreck as its former self, unable to sustain whatever colonies it has left and forcing said colonies to be on their own. Over hundreds to thousands of years, you would have several displaced colonies adapting to be self-sufficient in the most extreme ways possible.

> And while I would agree that stations should have functions, it's also true that you can't develop a new technology without experimenting.

My point is that from the larger context of the topic, we're talking about reasonably mature technology.

> A rotating hab with a counterweight is simply a rotating hab with the living and working modules all on one side.

If the entire hab is a singular structure with living quarters on one end and connected all the way to the other end, it's just a spinning hab. Like, imagine a long rod with habs on one end and all the heavy machinery on the other, and that rod is traverseable. A counterweight-and-tether design is simply hab-cables-weight with no means of traversing the cable.

But my point is specifically one where you have a habitat or capsule and a counterweight attached by cable. It's low-weight and easy, but there's also no way to access the spinning habitat. You want a docking station at the rotation axis so an incoming spacecraft can dock more easily. With a tether-and-weight design the common axis is at a thick piece of cable.

You could try and dock with the hab directly but that would mess with the moment of inertia and unless your station is really massive, it's probably going to be a pain in the ass for everyone. According to that calculator, the tangential velocity would also be really high so it's expensive to dock with. And building a solution where you have an access tunnel between hab and weight, then you've just build a regular station.

Umm, no. Interplanetary war is a mythical idea dreamt up by sci-fi authors for Rule of Cool. In the paradigm we're discussing here, it's literally impossible, not just impractical and stupid.

Welp, there goes my entire LN premise. Sigh...

If you don't care about realism and just want to write about a space war, go for it. A simple measure for whether you're writing hard Science Fiction or Space Opera can be: Do spaceships fly around shooting at each other? The harder you go on the sci-fi end, the less believable this is.

On the super soft end, you have aircraft carriers in space, Old-School Dogfighting, visual-range engagements, and so on. As you get harder, you dispense with that and have BVR (beyond visual range) missiles, lasers, and kinetic weapons. Harder still and you dispense with fleets of starships and have extreme-range kinetic weapons and nukes being dispatched from planetary or orbital bases. Heck, the simplest way to wipe out an enemy is to divert an asteroid to crash into them.

Edited by Fighteer on Nov 23rd 2020 at 7:45:36 AM

Plus as established for this setting, the Spacers don't really care for Earth but know it is going to be needed for any major expansion again. Any interplanetary war would be a futile endeavor considering the colonies are barely self sustaining enough for people to not die in the several decades that the Space Age has been lost.

Ships can be outfitted with weapons but this is a relatively new development as the Spacers themselves have found their own reasons to fight one another as the human species is want to do, but that isn't the topic of conversation here.

So something would need to happen that would prevent or cripple the space-launch infrastructure that kickstarted this Space Age would be out of action. Perhaps rebuilding efforts focused on those last as more of it was towards items such as power, water, food, and hospitals and medicine?

Sure. The point is that the duration of the event dictates how serious it is. For space travel from Earth to be cut off for decades, you'd need a truly devastating problem: catastrophic economic or political collapse on a global scale. Things that could do it: a nuclear war, a Carrington-level solar flare or CME, a super-pandemic (way worse than COVID-19), a supervolcano eruption.

I'm excluding climate change because it's a slow-moving crisis - slow enough that we could adapt, but if this hypothetical future utterly ignores it, there could be devastating events that wipe out space infrastructure, though it's unlikely to happen everywhere at once.

I still think that "spaceships outfitted with weapons" is ridiculous. These cut-off colonies/outposts would have no reason to attack each other and every reason to cooperate. I suppose you could have problems like someone hoarding a unique supply of a particular necessity, but when it takes weeks or months to get places, you're really limited in what you can do.

It's especially problematic when the use of weapons has a pretty good chance of destroying the thing you're fighting over, although that has some great dramatic potential. The Ceresians decide nobody can have their stash of gamma-globulin so the Martians send disguised troops, the fighting destroys the stash and everyone cuts off contact out of fear, that sort of thing.

Edited by Fighteer on Nov 23rd 2020 at 8:47:00 AM

I did say the setting was softer sci-fi and not to worry about the technology and its implications, no old school dog fighting however. Best I can describe it is that it is more similar to some of the dreams the 20th century had about a colonized Solar System, it is just missing a lot of steps. So don't worry too much about the weapons or why everyone is fighting, ships and transit times are tolerable enough that the Spacers rather than return to Earth are currently trying to build their own society out of what they can.

The discussion is about what would kill the drive to space, and so far I've gotten plenty of good suggestions. This will help the verisimilitude of the setting very much.

"A 100 to 200 meter radius easily gives us that figure of several thousand tons that I was talking about earlier."

I can think of no reason why that should be true.

Anyway, as for the OP, if Earth is run by a unitary global government, a change in policy could drastically reduce the contact between Earth and the colonies, forcing them to become semi-autonomous. A global depression could similarly reduce the motivation for the kind of large up front investment and long term ROI that space enterprises typically show. If a disaster like a Kessler catastrophe occurred at the same time, there might not be a strong incentive to rebuild the infrastructure.

An interplanetary war? That depends on the tech and the number of people living in space. In the Expanse a rogue faction of people living in the asteroids drops large rocks on the surface, which has much the same effect as a global nuclear war. That might suppress interplanetary contact a bit. If war is out then hit and run terrorist tactics might have the same effect, esp. if two or more factions are using them on each other.

"A counterweight-and-tether design is simply hab-cables-weight with no means of traversing the cable."

Why can't you transverse the cable? Why do you need to transverse the cable, the other end is just a counter-weight. If necessary, you could just launch a shuttle from the hab, decelerate with respect to the axis of rotation, and wait for the other end to catch up.

Now docking is an issue, but it depends on how often one needs to do it, and the relative size of the incoming craft. I can think of several options. Matching velocity with the hab in the axis of rotation and letting the hab "catch" the incoming capsule is the most obvious way, as long as the incoming craft is a small percentage of the hab's total mass. Another way is to put a docking module at the center of rotation, and match rotational speed. Another is to decelerate the rotation of the station (the whole point of a research station is to examine the effects of different strengths of micro-gravity, after all. So it has to have this capacity).

Hmm... About the gravity thing, should we start a separate thread on that? It appears to be a heated subject among hard sci-fi writers and space enthusiasts alike.