# The Expanse technical thread

## 106 posts in this topic

So they can go from earth to Mars in a week?

That means a craft like that could easily head towards 2000km/s assuming that length journey was as far as propellant lasted. A small craft of 100 tons would at that point have ~2x10^17 J KE. That's pretty much spot on the total energy of the Tzar bomb the Soviets blew up. Anyone with a small craft and a computer can wreck places.

Might they can do better than 0.3g, or go longer than a week, it gets worse as KE goes as v^2.

Edited by tater

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18 minutes ago, tater said:

So they can go from earth to Mars in a week?

That means a craft like that could easily head towards 2000km/s assuming that length journey was as far as propellant lasted. A small craft of 100 tons would at that point have ~2x10^17 J KE. That's pretty much spot on the total energy of the Tzar bomb the Soviets blew up. Anyone with a small craft and a computer can wreck places.

Might they can do better than 0.3g, or go longer than a week, it gets worse as KE goes as v^2.

Yes, well kinetic strikes (or at least the potential of them) are definitely an active concern for characters in the novel.

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1 hour ago, tater said:

So they can go from earth to Mars in a week?

That means a craft like that could easily head towards 2000km/s assuming that length journey was as far as propellant lasted. A small craft of 100 tons would at that point have ~2x10^17 J KE. That's pretty much spot on the total energy of the Tzar bomb the Soviets blew up. Anyone with a small craft and a computer can wreck places.

Heh.  Let's just say that eventually the chickens come home to roost.  The authors of the novels did not forget this fact.

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On December 20, 2015 at 1:36 PM, Rune said:

Yup, it's either soft magic-fi, or soft sci-fi. In any case, the depiction of a bustling solar system is at least provocative. Every rock out there is settled in some form, and the legendary 'belters' are there in-force. Microgravities too. One does forgive the expensive-asboop-to-shoot 0-G hairdos, and the measurements in a unit of distance the audience understands, when one sees that the show actually tries to explain things like brachistochrone trajectories, variable levels of gravity, and the like.

It tries, there is no FTL, and even tough there is a magic drive to speed things up, pretty much everything else other than *redacted* is very much plausible physics and/or TV show-biz licenses. They don't care about dV because they have enough in the tank to consider interstellar voyages (I.E: the Nauvoo being a very pivotal example of this).

Rune. Loved the setting, meh about the main story arc.

The rocket equation still applies tho.... Smaller ships are easier to launch.

7 hours ago, kunok said:

They use brachistochrone trajectories, they acelerate at 0,3 g or something like that half the way, and the  other haf way they decelerate at 0,3 g so they have 0,3 g all the way except in the middle when they change from prograde to retrograde. (0,3g was taken as an example because it's an acceleration a belter can tolerate).

In the asteroids they just spins them to have centrifugal force... But it they weren't reinforced, in reality they will just break away I think

That would never work- most asteroids are rubble piles, and would break apart if spun fast enough for artificial G.

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2 hours ago, fredinno said:

That would never work- most asteroids are rubble piles, and would break apart if spun fast enough for artificial G.

He is talking about Ceres and Eros. In the setting, both have been spun up to provide something like 1/6th G on the exterior, dug out levels. Never mind why are they tunneling in the first place if they can spin up such massive objects... I guess when you have magical fusion drives you can do pretty crazy stuff.

2 hours ago, fredinno said:

The rocket equation still applies tho.... Smaller ships are easier to launch.

I don't get that. The rocket equation specifically makes no mention to scale, only ratios... According to it, a continent-sized mothership can have the very same dV as a small firework.

Rune. I'm currently reading the last novels, which weren't out when I first read the series... Kod, I missed a good sci-fi story.

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10 hours ago, GregroxMun said:

So that, my friends, is what Mars' warships do. They don't cloak, they mind-trick.

I really hope that wasn't a spoiler from someone who read the books. Based on the series, I'd love to think the martians are lovely ideallistic fellows who has nothing to do with nuking civilians. Such actions would fit the careless and destructive Earth people more.

That reminds me - I'm an episode behind, let me catch up.

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4 hours ago, Evanitis said:

I really hope that wasn't a spoiler from someone who read the books. Based on the series, I'd love to think the martians are lovely ideallistic fellows who has nothing to do with nuking civilians. Such actions would fit the careless and destructive Earth people more.

That reminds me - I'm an episode behind, let me catch up.

It's not a spoiler, it's a joke.

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1 hour ago, GregroxMun said:

It's not a spoiler, it's a joke.

I didn't mean the technology (hell, I read and hitch-hike too, still celebrating every towel day), but the origin of the stealth ships. It's pretty questionable at this point in the series.

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4 minutes ago, Evanitis said:

I didn't mean the technology (hell, I read and hitch-hike too, still celebrating every towel day), but the origin of the stealth ships. It's pretty questionable at this point in the series.

Oh, well you will find that out.

But like I said, all that "stealth" means is that they aim all their waste emissions away from the target and have RAM on their black holds, so they are hard to spot actively or passively.

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I might be late to the party (I meant to write this the other day). Ceres is having water problems primarily because all of the water had been mined out to be shipped to Mars for the Terraforming project. Mars has been super resource hogging in the belt for that purpose, thus why the Belters are not super happy with them.

Additionally, we are not yet perfect at closed system water reclamation. Even the ISS is only something like 90% efficient at reclaiming water.

And for Tater's question about the artificial gravity, not quite. A lot of places like Ceres, they (the Tycho group) spun up to get spin-gravity. On ships, any time you see floating stuff, they are in zero-G and are just walking around with mag-boots (the heel clicking scene). If nothing is floating around (and usually no foot-clanking) then its because the ship is under acceleration.

As far as the Epstein drives are concerned, they've never really (best I can remember) gone into detail with how they work or any really solid numbers (though you can probably derive how good they are if you collect all the info about travel times, dates, ship masses, etc). The fusion power plants are just power plants that are either directly connected to the drives (IE: A fusion engine of some sort) or they simply power the reaction going on in the drive (one heck of a spark-plug).

What is kind of interesting with their fusion plants though, is that they appear to be the type being researched at the National Ignition Facility, where it has a pellet of fusile material that is hit with a bunch of lasers.

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1 hour ago, Mazon Del said:

As far as the Epstein drives are concerned, they've never really (best I can remember) gone into detail with how they work or any really solid numbers (though you can probably derive how good they are if you collect all the info about travel times, dates, ship masses, etc). The fusion power plants are just power plants that are either directly connected to the drives (IE: A fusion engine of some sort) or they simply power the reaction going on in the drive (one heck of a spark-plug).

There's an explanation on the wiki, it's a kind of fusion drive, which uses extra magnetic coils to further boost the exhaust.

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Also, if you look at some scenes, they go to lengths to demonstrate weirdness of Coriolis effect when Miller (or others) are pouring liquids.

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13 minutes ago, Montieth said:

Also, if you look at some scenes, they go to lengths to demonstrate weirdness of Coriolis effect when Miller (or others) are pouring liquids.

Yeah. I assume that is CGI. It would be tricky (but likely not impossible) to do that physically using transparent tubes and surface tension. CGI would likely be way easier.

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The gravity in this show (natural and artificial) still confuses me. People walk around on Ceres or Eros like they have the same gravity as Earth, but they talk about how the low gravity is warping their bone growth.

I love the show, and I get that they can't afford to shoot zero-g scenes every episode. Just something I wonder about while I'm watching.

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14 minutes ago, Mitchz95 said:

The gravity in this show (natural and artificial) still confuses me. People walk around on Ceres or Eros like they have the same gravity as Earth, but they talk about how the low gravity is warping their bone growth.

I love the show, and I get that they can't afford to shoot zero-g scenes every episode. Just something I wonder about while I'm watching.

What does it look like to walk around in low G without a spacesuit? Because, you know, I've never seen it.

The humans don't have any artificial gravity in this show. They only have spin gravity and acceleration gravity. Which brings me to the interior set of the Roci, which is all wrong. In the set they walk horizontally to the different parts of the ship, but the ship is actually built like a layer cake and they should be climbing ladders to get to the different areas of the ship.

Edited by mikegarrison

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By the way, this reminds me. How come in Star Trek, whenever the bad guys would take over the Enterprise, the Star Fleet people never just turned up the gravity to about 4g and dropped them to the floor under their own weight?

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3 minutes ago, mikegarrison said:

By the way, this reminds me. How come in Star Trek, whenever the bad guys would take over the Enterprise, the Star Fleet people never just turned up the gravity to about 4g and dropped them to the floor under their own weight?

Because that would also affect the starfleet guys...?

It's mostly just dramatic reasons.

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9 hours ago, mikegarrison said:

By the way, this reminds me. How come in Star Trek, whenever the bad guys would take over the Enterprise, the Star Fleet people never just turned up the gravity to about 4g and dropped them to the floor under their own weight?

Or that it *never* fails?

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9 hours ago, mikegarrison said:

The humans don't have any artificial gravity in this show. They only have spin gravity and acceleration gravity. Which brings me to the interior set of the Roci, which is all wrong. In the set they walk horizontally to the different parts of the ship, but the ship is actually built like a layer cake and they should be climbing ladders to get to the different areas of the ship.

They do use ladders a lot. I think the show just cuts out a lot of the climbing because it's not interesting to watch.

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SPOILER for Babylon's Ashes

If you've read the newest book Fred Johnson dies on a hard burn because they had crappy 3rd rate juice

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Posted (edited)

On 2/10/2016 at 11:48 PM, Mitchz95 said:

The gravity in this show (natural and artificial) still confuses me. People walk around on Ceres or Eros like they have the same gravity as Earth, but they talk about how the low gravity is warping their bone growth.

ISTR from the books that Ceres is spun up so that people can walk around the interior under Earth-normal gravity.  Other asteroids aren't.  Most Belters spend their lives in considerably less than a full g.

EDIT: If physics ruins a show for you, don't calculate how much energy it would take to spin Ceres up to that speed.  It will annoy you.

Edited by Nikolai

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8 hours ago, Nikolai said:

EDIT: If physics ruins a show for you, don't calculate how much energy it would take to spin Ceres up to that speed.  It will annoy you.

It's been a while since I read the relevant book, but I seem to recall that it took several decades for them to spin up Ceres, and that it's been hailed as the greatest engineering achievement in history. And they started with it long after the Epstein drive was invented.

Loving the book series so far, but I have no idea where to find the TV series to watch legally. Is it available in Europe at all?

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You can watch it on Netflix. Alternatively, you can buy the 1st season on (imported) DVDs, which are IMHO overpriced, compared to other season boxes.

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Realism is a funny thing. It's hard enough to get it right in contemporary or historical movies (say, "Die Hard" or "Braveheart") let alone in space.  As long as "it's the future" is not used as a magic wand to do anything it doesn't bother me that much. I'd rather see a good story with decent plots than something that doesn't thrill but is 100% accurate. So perhaps hair doesn't float in microgravity environments as it's supposed to. Does that somehow affect the story? I'm glad it doesn't for me. The world is a lot less entertaining if every movie or tv show has to be 100% accurate.

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Anyway, i'm aboard the Hypestein drive for season 2

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