SomeGuy123

The Expanse technical thread

86 posts in this topic

1.  Why are they running out of water on Ceres?  They show a big recycling plant in episode 2, and isn't a space habitat a closed system?  It doesn't have to be a closed system but it seems like a no-brainer to make it one.  My only thought is that something is consuming water permanently, which segues to 

2.  What kind of performance could Epstein Drives theoretically have if they are just a way to make fusion easy and high thrust? (as in, they still obey conservation of momentum)

My thought is that the logical reaction would be lithium-7 + protons.  They would then inject oxygen into the fusion plasma stream when they want more thrust.  This would therefore make the primary propellant they use water.

A quick perusal of this table here says 8.5% of the speed of light is the exhaust velocity.  My thought is the Epstein must be using aneutronic fusion, that the secret behind it is that it shapes plasma so well that there are these plasma mirrors inside, where sheets of hot plasma reflect the incredible heat of a star away from the components of the drive.  These plasma mirrors aren't going to be very effective against neutrons, but they would reflect away light and charged particles, allowing you to reach insane internal fusion reaction rates relative to the mass of the drive.  This also agrees with plot points in the show - the drive has so much hot fusing plasma inside that if a software failure causes the bottle to fail, it blows up the ship it is attached to.  It's basically the core of a fusion bomb continually reacting.

So for every proton, you get 2 helium atoms.  Total atomic mass 8.  Oxygen has an atomic mass of 16.  So you're tripling your total mass.  Assuming even division of the kinetic energy, and some energy is lost and the Epstein is only 95% efficient (it has to be extremely efficient or the whole ship using it is going to vaporize)

x = 1/2 * m * .95(8.5%c)^2

x = 1/2 * 3m * (V)^2

.5m(8.5c)^2 = 1.5m(V)^2

0.33333 *.95  (8.5c)^2 = V^2

0.562(8.5c) = V

V = 4.777%C

ISP =  1 459 845

Now we're hauling ass.  If your space awesomesauce wtf sci-fi Mars warship (that is "stealth" as well, of course, cuz special black paint prevents the star like flare from your engine from being detected) is half propellant (gotta have room for the railguns, armor, and really posh looking interior!) you can do a 10 m/s burn for 275 hours!

It depends on planetary positioning but it appears that this is about 11.4 days at full thrust, you could build a ship that could do a Mars to Jupiter run at 10m/s^2 the whole trip.  This is also why in theory, if you just posit that the Epstein drive internally basically uses magic - it's made of indestructible adamantium with internal mirrors that reflect 100% of all incoming energy away from the drive - you could do multiple gravity burns, for days even, if you had a ship that is all engine and propellant tanks.  (there are rich people racing ships in the novels that can do this)

 

One thing of note : if you're using proton-lithium or proton-boron fusion, the main mass of fuel is actually the lithium or boron.  The water consumption is nothing.  You'd be consuming the ship's mass in boron or lithium to do a high gravity trip between planets.  I'm not sure how much lithium or boron there really is in our solar system, at least in minable forms, to be throwing it away like this.  

Something like the Epstein might be possible, albeit it might have to be extremely large.  If you think about it, the larger a fusion reaction chamber is, the more the outer plasma protects the walls of the chamber from being heated by the energy produced by the inner core.  Logically you could just keep making the reactor bigger and bigger and bigger.  You could never use the energy produced directly - converted to electric power, you'd be producing as much energy as it takes to convert your whole ship to vapor every second - but you could allow it to escape, shaping the thrust plume with magnets indirectly and using yet more layers of plasma to protect you.  

Of course, good luck with stealth.  The absurdity of even attempting to stealth something that probably makes a plasma plume brighter than the inner planets as seen from earth...

Edited by SomeGuy123
2 people like this

Share this post


Link to post
Share on other sites

Nobody wants to discuss fusion drive performance or water recycling?  Bueller?  Anyone?

1 person likes this

Share this post


Link to post
Share on other sites

I only watched the first episode, but I read the first two books, and I'm reading the third.

In the first book, in the end is a little interview:

Quote

Leviathan Wakes has a gritty and realistic feel. How much research did you do on the
technology side of things, and how important was it to you that they be realistic and accurate?

Okay, so what you’re really asking me there is if this is hard science fiction. The answer is an
emphatic no. I have nothing but respect for well-written hard science fiction, and I wanted
everything in the book to be plausible enough that it doesn’t get in the way. But the rigorous
how-to with the math shown? It’s not that story. This is working man’s science fiction. It’s like
in Alien, we meet the crew of the Nostromo doing their jobs in this very blue-collar
environment. They’re truckers, right? Why is there a room in the Nostromo where water leaks
down off of chains suspended from the ceiling? Because it looks cool and makes the world feel
a little messy. It gives you the feel of the world. Ridley Scott doesn’t explain why that room
exists, and when most people watch the film, it never even occurs to them to ask. What kind of
drive does the Nostromo use? I bet no one walked out of the film asking that question. I wanted
to tell a story about humans living and working in a well-populated solar system. I wanted to
convey a feeling of what that would be like, and then tell a story about the people who live
there.
So how does the Epstein drive work?
Very well. Efficiently.

Here you can read  a little prequel that explains the discovery of the Epstein drive, http://www.syfy.com/theexpanse/drive/ , It's only 7 pages.

TL,DR: The Expanse wants to be realistic, things making sense but no hard sci-fi, no math.

 

For the water, it's used as reaction mass at least for the rcs of the ships (IIRC they use superheated steam), and I understand reading the books that also for the Epstein drive.

 

The stealth is not really stealth, it's just radar absorbent coating, and being only a few degrees warmer than the background radiation, so no reactor no engines making heat, only coasting in stealth.

Edited by kunok
improving format, typos etc

Share this post


Link to post
Share on other sites
2 hours ago, kunok said:

The stealth is not really stealth, it's just radar absorbent coating, and being only a few degrees warmer than the background radiation, so no reactor no engines making heat, only coasting in stealth.

Wow.  Their aim must be phenomenal.

As for the "few degrees warmer" thing... can we assume that the ship is therefore uncrewed?  Or do they handwave thermal equilibrium laws away?

I expect that even if this isn't hard science fiction, it'll still be plenty entertaining.

Share this post


Link to post
Share on other sites

Right.  Even if you ignore thermal equilibrium, the Epstein...those numbers above assume it's a real engine with the ability to basically contain a fusion bomb, for hours of burn time, and it's 95% efficient.  That's basically as described by the author.

The flare that would leave..one thing in the latest book they got right is that from a human perspective, seeing a ship in the distance using one of these engines, you see a gigantic plume of glowing gas.  At the very top of the massive drive cone is a tiny object you might miss.  That's the ship.

One would think that every time somebody fires one of these things off, thousands of separate sensors in the solar system would get triggered without fail, automatically recording the course of the spacecraft in question.  And you would reasonably assume all the major factions - Earth, Mars, the Belters - would have vast surveillance networks.  It wouldn't be very expensive - as I said, firing a drive like this, with a plume power measured in terawatts, is going to be really easy to see.

So if you have a stealth warship, that's cute, but one would reasonably expect that everyone would know about it's every move as you just can't hide your flare.

Share this post


Link to post
Share on other sites

i was tempted to watch it but decided against it. dont really want to take on new shows right now. might binge it some years later though.

Share this post


Link to post
Share on other sites
12 hours ago, Nuke said:

i was tempted to watch it but decided against it. dont really want to take on new shows right now. might binge it some years later though.

Decent sci fi shows that have high budgets don't grow on trees.  I don't actually know of any other show other than this one.  What's higher in your schedule?

Also, having read the books, I know that a great many intelligent and unexpected plot twists are in store for us.  Despite the early episodes, violence and space battles is not the main plot driver.  There's events that happen 4 books later I can see them foreshadowing in these early episodes.  Hope the show does well so it can make it to that point.

Edited by SomeGuy123

Share this post


Link to post
Share on other sites

I have also read all five books of the series. As I'm living in Germany I will probably have to wait a few years till I can watch the series (at least legally :P)
.

I've read of the "major TV series" on the back of the last book and since then I'm wondering how they will do many things. Especially the elongated bodies of the belters and the ever changing gravity. Okay they can fake high g's, but large potions of the story take place in microgravity and this is always very dificcult to display (I suspect the only reasn why every major space show featured artificial gravity :P).

 

Regarding the stealth in space point. In the first book this is a great thing. In the following books it is more and more downgraded. Seems like someone lectured Corey about this topic ;)

Share this post


Link to post
Share on other sites

Are you guys really talking about "science" for a show where spaceships stop when they switch off their engines or where the actors keep their Hollywood hairdo under zero-g ?

Share this post


Link to post
Share on other sites
33 minutes ago, Nibb31 said:

Are you guys really talking about "science" for a show where spaceships stop when they switch off their engines or where the actors keep their Hollywood hairdo under zero-g ?

It's far more accurate than most sci-fi out there, in terms of physics. The hair thing is something that I'm willing to let pass, most characters have fairly short hair anyways. 

What do you mean the ships stop when they shut down engines? I don't recall such moment. 

Share this post


Link to post
Share on other sites

The only thing I have taken away from this thread is EPISODE 2 IS OUT?!?!?

I may return to edit this post after watching it xD

Share this post


Link to post
Share on other sites
11 minutes ago, Karriz said:

It's far more accurate than most sci-fi out there, in terms of physics. The hair thing is something that I'm willing to let pass, most characters have fairly short hair anyways. 

What do you mean the ships stop when they shut down engines? I don't recall such moment. 

I'm not saying it's not enjoyable. I've only watched the first two episodes and it's really quite good, but I don't see what's accurate about it. The universe seems to be a mix of BSG and Alien. The ships seem to have their engines lit up all the time (unless they are just big tail lights) whenever they are moving and everyone evaluates distance in terms of kilometers which is meaningless in terms of space navigation. An enemy ship being 80000 km away is meaningless if you don't know their trajectory. They could be 10 km away, but on a course that would make interception impossible. In reality, they should be reasoning in terms of dV and orbit. 

Sci-fi is only fantasy where the "magic" plot device is replaced with technobabble. In pretty much any science fiction story, you can replace aliens with trolls and dragons, and technology with magic, and it would still work. That doesn't mean that it isn't good entertainment, but you have to take it for what it is, fantasy, not science.

Edited by Nibb31

Share this post


Link to post
Share on other sites
32 minutes ago, Nibb31 said:

I'm not saying it's not enjoyable. I've only watched the first two episodes and it's really quite good, but I don't see what's accurate about it. The universe seems to be a mix of BSG and Alien. The ships seem to have their engines lit up all the time (unless they are just big tail lights) whenever they are moving and everyone evaluates distance in terms of kilometers which is meaningless in terms of space navigation. An enemy ship being 80000 km away is meaningless if you don't know their trajectory. They could be 10 km away, but on a course that would make interception impossible. In reality, they should be reasoning in terms of dV and orbit. 

Sci-fi is only fantasy where the "magic" plot device is replaced with technobabble. In pretty much any science fiction story, you can replace aliens with trolls and dragons, and technology with magic, and it would still work. That doesn't mean that it isn't good entertainment, but you have to take it for what it is, fantasy, not science.

Well yeah, mostly the ships don't have to worry about orbits and delta-v because the have the "epstein drive" which is essentially a really efficient engine that can burn 1g or higher for months. They burn halfway to the destination, flip around and burn away the other half. It's technologically basically magic, but in terms of inertia and acceleration it checks out.

The distance thing is a bit weird. I suppose the nearby ship is just assumed to have a fairly close velocity vector, and with the epstein drive catching up shouldn't take long.

What I do like that stuff like artificial gravity isn't magic in this series, it has to come from linear acceleration or centrifugal forces. Being focused in our solar system is also refreshing, no FTL needed.

Edited by Karriz

Share this post


Link to post
Share on other sites
1 hour ago, Karriz said:

Well yeah, mostly the ships don't have to worry about orbits and delta-v because the have the "epstein drive" which is essentially a really efficient engine that can burn 1g or higher for months. They burn halfway to the destination, flip around and burn away the other half. It's technologically basically magic, but in terms of inertia and acceleration it checks out.

The distance thing is a bit weird. I suppose the nearby ship is just assumed to have a fairly close velocity vector, and with the epstein drive catching up shouldn't take long.

What I do like that stuff like artificial gravity isn't magic in this series, it has to come from linear acceleration or centrifugal forces. Being focused in our solar system is also refreshing, no FTL needed.

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.

1 person likes this

Share this post


Link to post
Share on other sites
On December 18, 2015 at 11:55 AM, SomeGuy123 said:

Right.  Even if you ignore thermal equilibrium, the Epstein...those numbers above assume it's a real engine with the ability to basically contain a fusion bomb, for hours of burn time, and it's 95% efficient.  That's basically as described by the author.

The flare that would leave..one thing in the latest book they got right is that from a human perspective, seeing a ship in the distance using one of these engines, you see a gigantic plume of glowing gas.  At the very top of the massive drive cone is a tiny object you might miss.  That's the ship.

One would think that every time somebody fires one of these things off, thousands of separate sensors in the solar system would get triggered without fail, automatically recording the course of the spacecraft in question.  And you would reasonably assume all the major factions - Earth, Mars, the Belters - would have vast surveillance networks.  It wouldn't be very expensive - as I said, firing a drive like this, with a plume power measured in terawatts, is going to be really easy to see.

So if you have a stealth warship, that's cute, but one would reasonably expect that everyone would know about it's every move as you just can't hide your flare.


Even modern ships play cloak and dagger with their sensor/radio emissions, even their lighting profiles at night. There have been numerous examples of warships slipping into lines of freighters at night and setting their emissions to look like and read like another warship or civilian ship. US Carriers even do this with lighting and emissions to look like bulk carriers. Their line and Radar Cross Sections very much look like bulk freighters or oil tankers.  Deception has a long and storied past with naval combat since before the golden age of Fighting Sail. 

With low observable ships, you could probably throw out a pattern of RADAR/LADAR reflectors that would give your stealth space ship a profile that looked like an ore freighter, or a water hauler or some other craft bumping around. Diddle your drive signatures for less efficient civilian modes and you'll look like just another ship blipping around the belt doing it's thing. The reason the Can't got killed was that they were too close and the operators of the Anubis didn't want any possible witnesses, which the crew of the Canterbury was. 

As to being stealthy, it would be even more useful to have a gaagle of RADAR/LADAR reflectors on your hull and then discard a set of them facing an opponent in a tactical situation (ie a battle). OR even both halves, the sensors of your opponent would likely continue tracking the reflectors and stop following the actual ship. Embed some remote emitters in those reflectors as well as jammers and other components with enough gear to make them look like the real ship while maneuvering and you'd seriously stand a chance of completely breaking your opponents lock in a heated battle. 

Edited by Montieth
added points.
1 person likes this

Share this post


Link to post
Share on other sites
On 18.12.2015 at 5:55 PM, SomeGuy123 said:

Right.  Even if you ignore thermal equilibrium, the Epstein...those numbers above assume it's a real engine with the ability to basically contain a fusion bomb, for hours of burn time, and it's 95% efficient.  That's basically as described by the author.

The flare that would leave..one thing in the latest book they got right is that from a human perspective, seeing a ship in the distance using one of these engines, you see a gigantic plume of glowing gas.  At the very top of the massive drive cone is a tiny object you might miss.  That's the ship.

One would think that every time somebody fires one of these things off, thousands of separate sensors in the solar system would get triggered without fail, automatically recording the course of the spacecraft in question.  And you would reasonably assume all the major factions - Earth, Mars, the Belters - would have vast surveillance networks.  It wouldn't be very expensive - as I said, firing a drive like this, with a plume power measured in terawatts, is going to be really easy to see.

So if you have a stealth warship, that's cute, but one would reasonably expect that everyone would know about it's every move as you just can't hide your flare.

This an stealth probe is plausible, but that is something small unpowered and pretty passive, its easy to make it harder to see than an 3 meter asteroid. as it hardly reflect light, if you are willing to accept reflection in some direction you can keep it colder. 
An ship is harder, an ship under power is impossible. 
 

Share this post


Link to post
Share on other sites

I forgotten about this thread.

The thing about people does thinks this scenario can't have stealth it's than they think that with that tech level i'ts doable to make devices with enough resolution and field of view, so you can see everything at once. Field, of course. Resolution? Not even kidding today.

But I think the expanse doesn't feature so magical or so futuristics sensors, so you need to actively focusing on something to keep track of it..

Edited by kunok
I think i'm a littlle drunk :|

Share this post


Link to post
Share on other sites

As I recall from the books, the main "stealth" technology is to aim all waste heat and similar radiation away from the target. So it's stealthy from the front, not the back.

Ships don't stop when the drive is turned off; they just stop accelerating. The Epstein Drive is so magically efficient that they can simply accelerate their way across the solar system with nearly unlimited delta-v, so they get effective G from acceleration and they get places really quickly. Smaller ships like lifeboats can't mount an Epstein Drive and have to use a regular fusion-powered reaction drive ("teakettle drive") which results in much slower voyages.

(I'm trying not to spoil future seasons by talking about things from the books that haven't been revealed in the show yet.)

Ceres has a water shortage because it was mined for water by Mars a century or so before, and recycling isn't perfect. (But really, it's mainly a plot element to show how the belters are oppressed by the inner planets.)

I don't think it has come up yet in the series, but they also have anti-cancer drugs that can keep you healthy even after absorbing what would be a fatal dose of radiation -- but only if you keep taking the treatments for the rest of your life.

Share this post


Link to post
Share on other sites

Because virtually any method of cloaking a ship from both sight and thermal sensors would break the laws of thermodynamics, I propose a new possible cloaking device for the ships:

 

The Somebody Else' Problem Field. In the book Life, The Universe, and Everything (The third Hitchhiker's Guide to the Galaxy book), there is a technology which cloaks ships from computers and people, simply by making it seem like the spacecraft is Somebody Else' Problem. Unless you're looking specifically for a SEP-field cloaked object, you won't know where it is, even if you are literally walking over it!

 

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

1 person likes this

Share this post


Link to post
Share on other sites

The more obvious thing I noticed the couple times I watched part of it was everyone just walking around. They have artificial gravity?

Share this post


Link to post
Share on other sites
7 minutes ago, tater said:

The more obvious thing I noticed the couple times I watched part of it was everyone just walking around. They have artificial gravity?

Centrifugal artificial gravity, thrust-based gravity, and sometimes magnetic boots (not actually realistic for the latter, but needed for filming TV unless you want to double the budget).

 

Centrifugal gravity is for space stations and Ceres, Thrust gravity is for torchships that accelerate at 1 gee, and magnetic boots are for when you would otherwise have no gravity but you're already over budget.

2 people like this

Share this post


Link to post
Share on other sites
12 minutes ago, tater said:

The more obvious thing I noticed the couple times I watched part of it was everyone just walking around. They have artificial gravity?

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

Edited by kunok

Share this post


Link to post
Share on other sites
8 minutes 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

They also have something they call "the juice" which helps them survive high G. It helps mitigate damage from the acceleration and also keeps the pilots from blacking out.

Share this post


Link to post
Share on other sites
1 minute ago, mikegarrison said:

They also have something they call "the juice" which helps them survive high G. It helps mitigate damage from the acceleration and also keeps the pilots from blacking out.

True but only for shorts periods. IIRC was amphetamine cocktail? I remember the books says something about it but I'm not sure.

In any case if they trie to use it to much they start playing with the death, taking higher and higher possibilities of a heart-stroke or another lethal injuries.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now