Let's Do the Science: The Epstein Drive

[@srbrant5391]

Fast, efficient, reliable and given a name that aged like milk under a heat lamp.

[@steveclen-murphy582]

didn't the moon used to be made of cheese?

[@Gaunerchen]

@@steveclen-murphy582 You believe in the moon?!

[@srbrant5391]

Steve Clen-Murphy It used to until sweeping reforms were made.

[@androkguz]

I get the feeling we will be talking about the expanse longer than we will be talking about real life epstein

[@iExploder]

The Epstein drive didn't kill itself.

[@hcwm2]

The books say that the exhaust plume is highly dangerous. Big ships must fly away from the dock on manuvering thrusters ("teakettle") until they are several kilometers away. Only then they can start the Epstein drive (the TV show takes more liberty with this). Also, ships need a certain size to fit such a drive in the first place. Smaller shuttles must rely on the so called "torch-drive", which is also fusion-based but more compact, more primitive, cheaper to build and a lot more wasteful. Torch-drives were the precursor to Epstein-drives. Solomon Epstein tinkered with the torch drive of his yacht to make it more efficient until he "invented" the new drive by accident. The subsequently sustained high-g burn killed him.

[@SargeRho]

They do reference it in the show, though. When the Nauvoo departs Tycho Station, her exhaust plume(s) melt part of the scaffold.

[@karlstorie8813]

Very few science fiction writers deal with the fact that an efficient space drive is an extremely powerful weapon. Even accelerating a 100 tonne spacecraft at 1 g, which seems like a reasonable thing to want to do, and using boron-11/proton fusion, the power of the exhaust would be 5 TW--twice the average energy the United States uses per second, in all forms. Quite a beam of carbon nuclei if it hit you! A real interstellar drive would be a planet-destroying weapon.

[@SargeRho]

Or a planet-destroying laser beam, as I think it's more likely that we'll push spaceships to other stars, than have them push themselves :P

[@karlstorie8813]

Good point. The Moties in "The Mote in God's Eye" didn't use their lasers to slow down their Crazy Eddie Probe at the other end because they figured they would have been hijacked to use as weapons long before then. So they shut them down before the announced end of acceleration and destroyed them.

[@allisonmackay3818]

"A drive is a weapon in proportion to its power as a drive." Larry Niven (paraphrased)

[@kjames982010]

The Epstine drive didn't hang itself.

[@wt743]

Didn't propel itself either...

[@alhemmings8554]

Nor was it killed off before it got to trials.

[@Rapman21]

You just won the internet.😂

[@zzz181085]

LMAO

[@Preyhawk81]

and its fuel are children.

[@garethsmith7916]

Based on information in the books, the drive is an inertial confinement fusion drive with a magnetic coil to boots the exhaust, that uses a D-3He reaction, and that can use an afterburner system for landing.

[@LetsDoTheScience]

You might understand the physics here better than I do. There are a couple of things that seem to make this unlikely but I'd like to get your thoughts as you may know it better than I do: The energy return form D-3He reactions doesn't seem anywhere near what would be needed for 15 or 30G acceleration, even with Magnetic boost. This is one of the more powerful and efficient fusion engines we can calculate now and it's nowhere near the acceleration. So I'm proposing there is some kind of secondary reaction going on, fueled by the reactor. In particular this kind of fusion drive would provide a vast surplus of power available to catalyze a secondary reaction. Also, although batteries seem good in this setting, it seems unreasonable to tie your primary power source to the need for thrust. So generally I concur that the type of fusion reactor would make a good candidate, I'd still assert there is some other mechanism that forms the actual drive that is fed by that reactor.

[@garethsmith7916]

I'm not entirely sure if they use a D-3He in the drive, but it is mentioned in Babylon's Ashes that a small belt station ran out of 3He for the reactors. They may use an other reaction like p-11B reaction for the drive. I'm pretty sure that may be energetic enough, but not entirely. I am sure that the writers don't have the regard the physics, given their estimates for times it would take to reach places.

[@garethsmith7916]

Lets Do The Science, also your videos are great.

[@warellis]

Ironically, from what people have said about the travel times in the books, they're actually sort of too slow given the speeds that are often mentioned in the books. Like the authors say the ships will reach somewhere at x time but if you actually calculate, you often find that the ships should reach earlier than x due to their constant accelerations and all.

[@warellis]

Well it is essentially a scifi magic fusion torch drive, like practically all torch drives are. The original Heinlein torch drive was really a matter-conversion engine (and I don't mean antimatter, I mean one of those magical 100% conversion drives that are still reaction engines.) It's mentioned in Leviathan Wakes in Chapter 17, when they're discussing the Rocinante for the first time, by Naomi that the Rocinante: "“We’ve got a full tank of water, the injectors have enough fuel pellets to run the reactor for about thirty years, and the galley is fully stocked. You’ll have to tie me up if you plan to give her back to the navy. I love her.” So it seems like water is the reaction mass and fusion pellets are the fuel source for the reactors in-setting.

[@just.sovannara]

If I see mankind exploring the entire solar system before i die, then I can die in peace

[@ireallyreallyhategoogle]

You mean if mankind survives the next 20 years, right?

[@JamesSarantidis]

@@ireallyreallyhategoogle Exploration of the Sol System and the Human Self-Extinction are more closely related than many people think. History has shown that vast amounts of colonizable space can lead human groups of power (Ancient Greeks, Roman Empire, British Empire, etc) to expand to new territories instead of conquering rival nations of equal power. If there is a platinum vein on Mars and you have means to go there, why wage a costly war? Sure, wars will not stop ("War never changes") but it will be focused on space trade lanes and extraterrestrial colonies instead on the only planet we all call home. If human groups with power (Nations, Conglomerates, Religions, etc) have conquering others as the only option to become better, then war becomes an inevitability. I think it is the responsibility of our current generations to steer humanity towards Exploration instead of Conflict, for the prosperity and survival of all things that live.

[@DarthGreek]

if you were born before the 2010s i think you wont see much. a maaned mission to mars though would be good and possible to see

[@damienspectre4231]

mankind is spending close to a trillion dollars a year fighting islamic extremism. but for those looney bins, you might have seen it already

[@BobbinMcferry]

How will you know they saw everything though...?

[@nosorab3]

excerpt from the wiki: "The drive utilizes magnetic coil exhaust acceleration to increase drive efficiency, which enables spaceships to sustain thrust throughout the entire voyage." Dubiously canon, but it fits in with what we've seen. Instead of some new flavor of fusion with exotic fuel, the magnetically interactive plasma is funneled into a coilgun-like apparatus and accelerated to even greater speeds, the added velocity of the mass ejected out the back is translated into additional thrust for the ship. So 'runs on efficiency' means "wring every last newton of thrust out of our propellant"

[@reezlaw]

That would still require a relatively ample amount of reaction mass though, wouldn't it?

[@BalooSJ]

@@reezlaw The more energy you have available for accelerating your reaction mass, the less of it you need. Simplified, reaction mass, energy, and speed is governed by the interplay between kinetic energy and momentum. The mathematic formula for kinetic energy is E = m * v^2 /2. The formula for momentum is M = m * v. The thing is that momentum is a vector (it has a direction), and the total momentum of an event has to be 0 (equal and opposite reaction). So if (and my stuff) weigh 100 kg, and I throw a thing weighing 1 kg at a speed of 10 m/s in one direction, I will also throw myself at a speed of 0.1 m/s in the other. To do this, I need to supply 1 * 10^2 /2 + 100 * 0.1^2 /2 = 50 + 0.5 = 50.5 J of energy. If I instead had a thing of the same weight as me, I would only need to throw it at a speed of 0.1 m/s in order to propel myself at 0.1 m/s in the other direction. That only takes 0.5 J (for a total of 1 J), instead of the ~50 J it took to throw the small thing. The faster I can throw the thing (my reaction mass) in one direction, the faster I can propel myself in the other, but the energy needed scales up with the square of the velocity. So you need to pump increasingly high levels of energy into your reaction mass in order to go faster. If I can't put out ridiculous levels of energy, I'm going to need more reaction mass to compensate. This is why our rockets generally consists of almost all reaction mass with a tiny bit of payload, and even have systems designed to relieve themselves of the casings for the reaction mass in order to reduce the amount of reaction mass needed (multi-stage rockets).

[@reezlaw]

@@BalooSJ sure, that makes sense

[@glintongordon6811]

​@@BalooSJthat calculation is only for vacuum of space flight or is it applicable to be used to break earth gravity? Starting from 0.

[@glintongordon6811]

​​@@BalooSJsorry I'm this late, it's been 3 years, hope you are still there

[@BrandyBottle]

Generalkidd -- My Grandfather was born in 1898, he told me about seeing first the hot air balloons, then the biplanes, then the single wings, then jets, then our first satellite launches, then Mercury, Apollo, Gemini, and finally sitting in front of the TV watching the first man to set foot on the moon! So, in under 75-years, we went from the caveman-era (balloons)-to-space flight (rockets)... It'll only take one discovery and we're out there!!!

[@krzysztofrusek9096]

For that science leap we needed 2 World Wars... Im not sure what price will be next science leap :(

[@theothertonydutch]

Trump is on top of the expenses. :P

[@krzysztofrusek9096]

?? Another anti trump crying antifa fighter? You dont understand what I'm speaking of. Any leap in science is fueled by war. From earliest bronze spears to WW II radars and remotly controlled bombs. Well wars reduce population and by default - halts economy and innovation (after war is period of rebuild and stagnation caused by loss in population) To put it simply - war gives us great discoveries and technlogies but cuts our population and humanity needs at least 4 bilion people to do not regene and sustain quantity of geniouses ingeeniers and sciencists. Percent of geniuses is constant - it is less then 0,5% of population. So we need to maintain 9 bilion people on Earth to advance our science. Question is how to stimulate growth and do not stagnate.

[@die1mayer]

I don't think wars are necessary for human progress, rather competition in general and adequate funding for new technologies. Conflicts will continue to exist but full-scale war has just become too destructive to be a viable option for anyone. These space technologies do have a basis in reality however, Wernher von Braun really wanted to go to Mars after the Moon but the US simply had no interest at the time, JFK was shown a model of a nuclear-propulsion armed spaceship called Orion, Reagan tinkered with the idea of a missile shield in space(SDI), the russians also tested lasers and a flak cannon in space. Fusion reactors already exist as testing platform (Tokamak and Stellerator). Nowadays private companies like SpaceX aim for space tourism, trying to reduce the cost of launch via reusability or stratolaunch, China plans a manned mission to the Moon but that is mostly for prestige. The Moon is actually very attractive for mining operations in the future, because it is resource-rich and not that far away.

[@krzysztofrusek9096]

Well now radar is easly accesable - everyone can build one if really wants. How many radars were before WW II ? Five or six ? All experimental constructions in universities. And suddenly - becauses of War - radar were needed on battlefield - for aircraft nad ship detection on UK coast, on ships, on wheels ( Wuzburg radars). Let me ask you - how many product made out of boron nitrates have you seen? I didnt seen any civil construction using boron nitrates as a part in composite material. Thats military tech. Same with grafen , carbon fullerens and other stuff. After next war - that stuff will be accesable by civil industry and military will work on another generation of "military grade technologies" That is science jump fueled by war - to put it simply military tech becames outdated and is accesable by civilian factories.

[@widget3672]

I finished season 4 when it came out and there's a couple of shots of the inside of the epstein drive fusion chamber (more protomolecule meddling) - and it seems to be a large magnetic confinement system no unlike a tokamak but without the donut hole making a real torus. The thing apparently drops 'fuel pellets' into a laser compression for fusion - sort of like the National Ignition Facility, and despite the huge engine bell, it seems to be surprisingly contained - I suppose it uses magnetic confinement to control and focus fusion products into high velocity, high volume nuclear powered engines that eject plasma for propulsion. Now, I appreciate that in going from Star Trek style space travel to The Expanse style space travel that reflects our collective understanding of space better - gravity is not waved off as something to worry about later, but it makes a central characteristic that defines whole populations and ways of life - and I like to think that the Expanse does a great job of showing things from a number of perspectives and angles, no one sees themself as being 'the bad guy' because there isn't really a bad guy (even protogen) because despite their willingness to engage in horrific acts, they believed their rationale reasonable and the show doesn't hide that - though it makes a point of how there are a lot of people out there... People like Dr Strickland, like Prax and like Amos. I suppose I like the idea that we're getting closer and closer to that dream like vision of interplanetary solar-system-wide human settlements and what life in that could be like just tracing a short line out from the technologies we already have today and in a matter of decades could be game changing. Almost worries me how much more work we'll have to do before we can even get close to this as a reality (especially with consideration that Star Trek wasn't absolutely unbelievable for its time, what if in another generation or two there's another epic science fiction show that makes the expanse look dated *"Ha, they thought they had to use Newton's laws for motion in space. How cute, look at them trying to use fusion in that tiny little reactor."* - Science and nature have a history of throwing us off and being confusing, but even as we make new discoveries that do push us closer to whatever limits we may have, I'm excited for the future - and I think that's what good sci-fi does best.

[@entropiated9020]

I recently happened to be watching Star Trek TNG and DS9 while also watching The Expanse (gotta diversify!) On their trajectory pre-protomolecule, the Expanse universe was nowhere close to a Star Trek future. But with the gift of the ring gate (essentially a fancy wormhole à la DS9) the humans in the Expanse have gotten a huuuuge step up in terms of ability to reach out and expand the human sphere of influence. Not 1300 planets, but 1300 SOLAR SYSTEMS to explore! If Earth, Mars and the Belt don't end up destroying themselves over it, it'll be glorious!

[@widget3672]

@@entropiated9020 (that's kind of the plot of books 5 and 6)

[@dauchande]

Didn't David Brin say if you're going to violate the laws of physics, you might as well violate all of them?

[@Robinlarsson83]

That's not the drive, where we see the fuel pellets, it's the Fusion reactor that powers the entire ship, not just the drive. It may be that the Epstein drive is a direct fusion drive, or maybe it's just powered by electricity from the fusion reactor? They are basically always running the reactor, whether they are running the Epstein drive or not.

[@Generalkidd]

You should do an episode on communications in the future. They seem to be able to transmit large files including HD video across the solar system at high bandwidth speeds whereas today a single high resolution image would take hours, sometimes days to fully download. The New Horizons probe for example only is only able to transmit data back to Earth at like 1-2 kb/s whereas in the Expanse, they seem to be able to transmit and download full HD videos almost instantly despite the delay from how long it takes light to travel long distances in space. Why does our modern day deep space communications have such limitations and is it actually possible to transmit large files at high bandwidth speeds across vast distances with radio waves?

[@dominiccingoranelli3071]

I'm kind of surprised that this comment didn't receive much attention. Don't big youtubers usually get a ton of attention on their comments?

[@davidhart1674]

A distributed (mesh) buffered relay/routing system perhaps. I recall in s03e04, when the Rocinante is near Jupiter, Holden saying to Naomi regarding the video message Avasarala wants to send to Volovodov on Earth (Errinwright's self-incriminating one) "Find us a router to bounce a tight-beam [laser] off of, something that can't be traced back to us." Presumably the solar system could be littered with millions or billions of these relay devices plus larger routing platforms. Already on Earth we have in excess of a billion devices capable of relay (smartphones, even though they're not used that way for the most part), and millions of Internet routers, and pundits are anticipating trillions of IoT devices in the next few decades.

[@hefeibao]

@@davidhart1674 That is how I saw it too.

[@nathanklumpenaar9378]

@@davidhart1674 In the books it is also made clear that almost everything can run on peer-to-peer networks. Which does seem to suggest that almost any device can function as a some sort of router.

[@philgiglio7922]

Lasers have a very high bandwidth. Belters/MCRN/Earthers all use lasers for both ranging and communications.. Same idea as fiberoptic, just free space.

[@trolleyfan]

The Kzinti lesson: "A reaction drive's efficiency as a weapon is in direct proportion to its efficiency as a drive."

[@ClockworkAvatar]

I knew someone would mention this.

[@lockwright4110]

@David Johnson ~ Aye, it commits the old sin of imagining only the ships with railguns are armed, when a fusion powered plasma rocket (a directed nuclear weapon) would put the railguns (admitedly very powerful kinetic weapon) to shame. But it's still a lot better than most of the science fantasy on TV, so I repeat to myself 'It's just a show, I should really just relax' la la la ♫ ...

[@nehorlavazapalka]

most fictional antimatter engines would either need very strong, lightweight magnets or some kind of gamma ray laser thingy that would pump out the gamma photons in a correlated stream since we're talking PWs of power in Expanse sized ships if we're goign antimatter and ~ 10 % c+

[@Draekris]

Book spoilers! A small ship is eventually used as a nuclear missile in exactly that way. There is also a lot of use of improvised kinetic weapons (including ships and improvised guided kinetic bombs dropped from fast moving ships). (And discussion of dropping rocks on people throughout the books.)

[@AlphaSquadZero]

A weapon becomes more efficient the smaller the area you focus the pressure at the cost of less overall force and a drive becomes more efficient the wider you let the exhaust spread at the cost less overall pressure. So, in the end drives make for terrible weapons and weapons make for terrible drives.

[@TheFuzzypuddle]

2 hour or less unmanned delivery to the moon... sounds like amazon prime

[@Gigipretty64]

Makes sense that Bezos would want to be able to ship earth goods back to his home planet.

[@CHMichael]

Would be funny to drop some names like amazon shuttles or elon musk city on mars.

[@JeanClaude-go6br]

Actually it could be a round trip of 1 hr and 13min if we take the speed of the plasma torpedo instead.

[@Nauctshea]

As far as I remember, the books specifically state that they have a reaction mass in addition to the Epstein Drive to produce thrust. Running the ship at 1/3 or 1/2 is not primarily for the comfort of the crew or to conserve energy, but to conserve reaction mass. They probably inject it into the fusion output to give the exhaust enough mass to produce thrust. The Epstein Drive is efficient enough that the real limiting factor in distance and speed ships can travel is not the amount of fusion fuel but reaction mass. This would also give the Epstein Drive exhaust the utterly destructive force it's been seen to produce.

[@mrkacperso8974]

Yep I believe it's clearly stated in pursuit after Free Navy, that if they will accelerate at current level they will run out of a reaction mass, miss the station, and be lost in space around the Sun. The were clearly using Epstein drive then (pursuing ppl who stole protomolecule, it was no time to save fuel, but to fly as fast as they can).

[@jacobshort6528]

Imagine using trashed garbage from Earth as the reaction mass for the drive, cleaning up the Earth

[@JeffUmstead]

The reaction mass is highly purified water, and it requires a relatively small amount

[@Generalkidd]

I'm curious, suppose we launch a small ship, like a space shuttle, into space and it docked with a large rocket like a Saturn V that's fully fueled in space. What kind of acceleration and g force in space could a fully fueled Saturn V rocket achieve and how long could it sustain that thrust?

[@cinquine1]

The saturn V had a total burn time of 1025 seconds. Someone did the math and it has a total of 18 km/s of delta v. That's the speed of voyager 1 right now, so that gives you the idea of the performance. This is because the rocket is designed for power, not efficiency. The first stage would be hugely wasteful in space, and the entire thing is a chemical rocket, so it is terrible compared to the things talked about in this video.

[@SahilP2648]

Elon is planning just that for his Mars mission

[@kaseyboles30]

@@cinquine1 Also you would have to at the very least redo the bell's (probably a lot more than that) on the 1st stage engines for vacuum operation, or your efficiency that's already meager would drop massively.

[@Zamolxes77]

Unfortunately spaceships don't work like cars. You can't take a ship designed to do one thing and put it to do something is not designed for then hope for the best. That's the kind of logic a US senator uses . Cars, (and everything else designed by man except rockets) operate in more or less equal gravitational constant and constant atmospheric pressure. Rockets and spaceships do not. Does your hypotetic Saturn 5 contain the command module and the LEM as well or not? Is your space shuttle loaded or not ? Someone above says Saturn V had 18 km/s delta V. For what mass, the CM and LEM mass ? Space Shuttle dry mass was 78 tons 5 times the mass of the LEM ! You can;t talk about dV and not talk about the payload mass. One payload gives you a dV table, another payload gives you a different one. To answer your question: it won't go very far if anywhere at all.

[@ezio48]

They don't travel to the stars in the Expanse! They are confined to the solar system.

[@sirwahthemonke]

Not because of thier technology

[@oliverfranke7650]

@@sirwahthemonke But they could. Constant acceleration of one g means you need 66 years and around three months to get to Proxima Centauri. And in fact the Mormons had the Navoo build to do exactly this. So it's not impossible for them.

[@sirwahthemonke]

Just fucking insanely difficult. Fuck this is an old comment

[@themadhammer3305]

@@oliverfranke7650 not impossible just requires 3-4 generations in constant space flight with nowhere to run and no help if stuff goes wrong. There's a good reason the Navoo was considered one of mankind's greatest achievements in the books. Mind you I am just starting the third book so there may be more I'm missing and if there is please limit spoilers:)

[@oliverfranke7650]

@@themadhammer3305 That's not the point. Your reasons just say "Don't try". It is in fact possible and the Nauvoo proves it possible.

[@CarFreeSegnitz]

#Epstein Rocket efficiency is all down to getting reaction mass up as high a velocity as possible before letting it go out the nozzle. The Epstein drive must, somehow, manage to send particles with some mass out the nozzle at very nearly the speed of light. There's only one device on Earth that does that: particle accelerators. The only way the Epstein drive can be as efficient as portrayed is by being, at least in part, a particle accelerator. Particle accelerators have to be pumped with energy. What is the most efficient source of energy by mass of fuel: some form of nuclear energy. Chemical energy is at least a million times too diffuse to work... so Epstein Drives are not powered by double-A batteries. Obviously fusion gets bandied about in The Expanse so this must be the power source for the particle accelerator component of the Epstein Drive.

[@a-blivvy-yus]

Two possibilities building off this idea: 1. Less plausible, but given the extremely large mass of neutrons, what if the thrust is produced by a neutron accelerator. Modern particle accelerators require charged particles, so that seems improbable. If it were to happen though, it both solves the problem of the neutron radiation and uses an otherwise-wasted product of the fusion reaction as fuel to produce thrust. 2. If they can simply capture and contain the neutrons somehow, they break down into charged particles at a fairly decent rate, so it would be possible to use the instability of the contained neutron radiation to fuel particle accelerators, gaining most of the same benefits (though not quite to the same degree as the proposal above).

[@ChrisWilson999]

Yes, and our particle accelerators like LHC are *extremely* inefficient. If however we figured out how to accelerate any atom to within a billionth of a billionth of a KPH of C with 80% efficiency, then a 1G or better drive would be possible. Remember a particle moving so close to light speed would have a *huge* mass (relative to a stationary atom). Sending it out the back of a ship would have an equal and opposite reaction and you can put a *lot* of atoms in a small space. As long as you had a power source that could keep sending them at the necessary rate to provide 1G, you could accelerate for long periods of time.

[@kukipett]

I think you know about the size of the LHC and the extremely thiny mass it can handle. I'm a physicist and i can understand dreams, but reality is a bitch that wake you up with a huge kick in the ass! Such things as the Epstein drive are wet dreams we can imagine but to keep such a fantastic story as The Expanse intact, we better forget about explaining that drive and see it as the Star Trek warp engine, something magical ! In the two case, it was some kind of crazy scientist that made that huge discovery all alone in his garage with a tool kit and parts coming from vacuum cleaners and lawn mowers !!!

[@manictiger]

​@@kukipett To be fair, they used to say that about nuclear fission. Ah, it's just a flight of fancy. It'll never happen. It's pretty on paper. While, using a particle accelerator as a way to travel seems horribly inefficient, I think we'll find a way to continue "hacking" on the quantum level. Hell, in The Expanse, they're not even using quantum technology to communicate! 300+ years in the future and they apparently didn't figure out that the quantum world is really funky and can be used to do some really funky things, such as communicate with 0 picosecond delay.

[@csenky]

@@kukipett Well I'm not exactly a physicist (I'm a moron to engineering whatsoever), and obviously if we knew how to do these things we see in sci-fi movies, these wouldn't just be movies... But be reasonable, comparing ST warp engine to the Epstein drive is like comparing the LotR movies to Troy (2004) for example. One is trying to keep a foot on the ground, the other is up high in the clouds, and we all know which is which.

[@MrSpartanspud]

One thing we do know is that drive will never kill itself. Very durable in that regard.

[@andreas_klinger]

FYI: in the books they speak of distant outposts that primarily receive their goods via unmanned cargo rockets

[@anarchofuturist3976]

or railgun projectiles

[@Gordozinho]

or clown driven brick walls

[@anarchofuturist3976]

Lucas lee what? I was saying in the books, they use railgun to launch supplies.to distant colonies

[@warellis]

So like a mass driver? Sort of like the mass drivers we see in Mobile Suit Gundam or the Moon Is A Harsh Mistress?

[@JTMC93]

warellis yes a Mass Driver. Though if it is a Rail Gun it is a Linear Accelerator. A Mass Driver uses a Coil Array.

[@gregbenwell6173]

In the one episode where the Nauvoo is "trusting away" from Tyco Station, there is a slight part of the scene where it is melting the gantry metal as the engines are powering up!!! And the plasma is what is causing the metal to melt!!!

[@daedalus-N7]

Greg Benwell in Leviathan Wakes, they actually had to tug the Nauvoo with tugs away from Tycho station for 8 hours before they could even fire up the main drives. to not cook everyone on tycho with radiation. also when the Nauvoo was approaching Eros millers suits radiation alarm went off when it was still 30 mins away from impact.

[@gregbenwell6173]

Jesse yes I know all this, I have watched that episode about ten times now and as the tugs are returning to their base, and the main engine is firing up, there is a gantry girder IN THE FOOTAGE, that is for a split second glowing red hot as the main engine of the Nauvoo is beginning to fire up, that melts away!! Like I say watch it, and watch it very closely, and you can see the girder melting from the heat of the engine! And it only shows it for a fraction of a second.....so you really have to be looking for it!!!

[@daedalus-N7]

yes i am aware of it melting the girders in the tv show. and burning up that one tug that got to close. i was just mentioning that it would have probable melted all of Tycho if they fired up the main drives right beside the station, in the book lol

[@TheRantingRooster]

Greg Benwell approximately 17:22 to 17:27 in the video. Also Tycho Station appears to be perpendicular to the Nauvoo, so when the engines kick in, while melting the gantry beams/truss, doesn't burn the station. What it 👀 like to me. Weird, I'm watching this very episode (kinda, surfing yt as while watching..)

[@JM-yq9ns]

Plasma doesn't have that kind of thrust, Plasma thrust has a very long burn time. Plasma is about 5000 Seconds per impulse. The shuttle has like a 114 Second burn. Now the shuttle has a shorter burn because it has a great kick. But Plasma is a slow low long burn. But this is a good thing because that means reaching greater speed over time, not in a short period of time like the shuttle, but because all the fuel burns up quickly in the shuttle vs the Plasma engine. The plasma engine is accelerating every atom at the speed of light. Unfortunately that means it takes longer to reach high speeds but that is ok because it is far more efficient and we can reach greater speeds than the shuttle can.

[@BusyBasaz]

#mytheory now I'm no scientist, but if I've learned anything from the cartoon kids shows growing up is that this engine is driven by love and friendship.

[@chasonsnotes]

Definitely, I love the show and want a protohuman bodyguard

[@djinnisequoia]

Right you are! "To infinity, and beyond!"

[@infernusifrit9348]

V.A.S.H.

[@klausgartenstiel4586]

the strongest ship in the fleet.

[@keirfarnum6811]

Or if you’re Wile E. Coyote, hate for a roadrunner.

[@micmccond7]

i place my bet on magnetic resonance of helium 3 fusion.

[@djinnisequoia]

Something about the way that phrase sounds tells me you are right. Or at least, it sounds really great! (must go look up now.)

[@kerbodynamicx472]

I think it’s ultra dense deuterium, basically supercritical deuterium, and then it goes fusion after a few seconds it is created?

[@damonedrington3453]

@@kerbodynamicx472supercriticality is a fission, not fusion phenomenon. Fusion energy cant start the same kind of chain reaction that a fission one can, because fusion requires atoms to be as close together as possible, and the energy released by a fusion reaction pushes said atoms apart. Only very strong magnetic fields or mass can force them to stay together and keep the reaction going

[@benwilliams9692]

recently there was a paper published that essentially used a primary reaction in a doughnut shape with the force forced inward to ignite a secondary reaction that directed the force out the back. If a system like that was made effective, it would surely provide those kinds of accelerations.

[@benwilliams9692]

www.nextbigfuture.com/2017/04/imploding-liner-fusion-propulsion-system.html I misspoke about initial reaction. Though, I suppose the electricity to run the magnets would come from a fusion generator.

[@cjhs77338]

The fuel pellets are to run the primary reactor and generate power. They have yet to say what they are but it is mentioned that helium 3 is mined for use in station and planetary reactors for power so it may be a hyper compressed version of helium 3. The books mention drive mass as being used to propel the ships in the form of highly magnetically accelerated plasma propulsion (As stated in the line of having enough fuel pellets to run the reactor for months but they would run out of reaction mass before that). And the maneuvering jets in the books use accelerated steam.

[@anarchofuturist3976]

helium 3 reactions would make sense. they produce much less radiation, so they would need less shielding for the reactor, resulting in a lighter ship.

[@marianpazdzioch6632]

They would run out of reaction mass withing hours if not minutes. Whole point of fussion is that it's effective, and uses much less fuel mass and produces much less byproducts than chemical rockets.

[@N7zebracakes]

They fuel pellets is when they run "teakettle", or without an Epstein drive. It provides lighter thrust for maneuvering "short" distances in space, usually from station to station within the asteroid belt, or moon to moon in the Jovian or Saturn systems.

[@obliviousfafnir01]

Nope. The Fuel Pellets are for the fusion reactor. The maneuvering thrusters are vented steam, hence why it's called "teakettle".

[@gkirmathal]

Apologies for the darn long reply. By my account, what is meant with term 'teakettling' was NOT the super heated steam based RCS system. But it was an "old timers saying", stemming from the torch drive era, that was used to compare the 'very low thrust' (of only running on reactor plasma only mode) to that of a 'wispy steam cloud' coming of a 'boiling teakettle' (the steam from an actual teakettle, would hardly generate generate any thrust in a vacuum at all). Steam has VERY BAD isp, but okish thrust, therefor steam based RCS could not have been be used as a propulsion means for prolonged periods. But plasma as propulsion can. It gives very low thrust, due to low molecular weight. Which is inline with what is mentioned in the books. So IMO, that usage of steam + kettle and RCS in the books confuses(d) a lot of readers what it meant. In Nemesis Games, if I'm not mistaken, it is even mentioned a few times that Inaros's ship was teakettling for prolonged periods, to conserve reaction mass, having near to no thrust gravity (besides them being on the drift).

[@Soupie62]

I always assumed the Epstein drive somehow reinforces its own magnetic containment field. I also thought the magnetic field extended, acting like the Van Allen belt to protect people from cosmic radiation.

[@Empiro3]

In book 4, they state that it takes a civilian freighter 18 months to travel 5 light-hours. If you work out the math, it means that they only accelerated 11 hours or so at 1/3 g instead of any significant part of the trip. In the other books, travelling out to Neptune also takes months (presumably on a Earth ship, they would accelerate at 1g the whole way if they could). I believe the authors didn't really think carefully about how fast you can get at a constant acceleration for days at a time. I wonder how the show will handle it going forward (they've been pretty vague about travel times so far).

[@MannyLectro]

Hmm I think it does make sense. 1go is shown to be too much for most belters, even for marsians. I think most of the solar system is used to travelling ar lower g's.

[@toddkes5890]

Civilian freighter might have it where they use algae recycling for food, in order to carry more cargo. The fuel tanks might require special connections, but food can be MREs, algae tanks (with vitamin supplements as needed), and only needs a basic power supply and room. The original freighter might have been an Earth-Luna or Earth-Mars freighter, but pressed into service for longer-distance transport. Or they wanted someone out of the way, and put them on that 18-month trip.

[@Dawn-hd5xx]

The big reason you can't trust any speed or time given in the books though is the fact that the author acts like acceleration is velocity, and that 1/3g is how fast you're going, not how fast you're changing how fast you're going. It does give an easy way to allow for "gravity" on ships without requiring every ship to be spinning like the Nauvoo / Behemoth / Medina. I think it's a fair tradeoff, taking a little creative liberty with physics in order to avoid magic artificial gravity while still allowing for maneuverable ships that aren't always at zero g (a big enough ring for artificial gravity isn't going to be suitable for fast combat like a fighter would be involved in).

[@Fafhrd42]

They did. They're pretty specific about most travel happening 'on the float.' Which is to say: ballistic. There are very few cases of ships going under constant thrust with flip from point A to point B. They do an initial thrust of about 1/3rd g to get up to a decent speed, and then cut their engines and float until they need to slow down again.

[@lenapod]

Tom Jiang Lenghtier traver time could be a tradeoff with fuel consumption. Many belters might not be able to afford enough fuel for constant acceleration.

[@RedBattalion9000]

[Expanse] "It's the longest funeral in the history." How romantic but realistic space adventure ever.

[@pvalpha]

*puts on SciFi speculation hat* I'd wager that its some sort of magnetic bottle engine where only thrust products of a certain energy/velocity are allowed to escape. Basically a re-burning engine where hydrogen is brought to fusion temperatures (or beyond) and only hydrogen and helium ions with sufficient KE are able to escape the bottle along the outer edge of the engine bell. It would use an MHD design to move the ionized particles through various magnetic shells and back into the core. Thus everything that doesn't escape is sucked back in for successive passes through a partially exposed fusion core. The bell and components would be constructed out of a Tungsten alloy with powerful electromagnets driven by the ship's primary internal fusion generator. All waste heat from inside (including the crew compartments and internal fusion power systems) is directed to the engine system to be focused on the core. The exhaust products would be moving about 30 percent of the speed of light, assuming that at least 3 acceleration passes through the core are made with the particles gaining 10% of light speed each pass and some fraction of the particles having the capacity to fuse into He which would kick the exhaust products up a notch. It would be impossible to get it up to He+ fusion, which would result in carbon product (which would be bad for the crew because carbon isn't magnetic, and would have just as much a chance of firing through the tungsten shield and into the ship... not to mention HE+ fusion would be... well... more than hot enough to vaporize tungsten alloy. Of course, this brings up another potential way of boosting thrust: allowing small amounts of tungsten to be ablated by the partially exposed fusion reaction, and become a part of the acceleration loop. Basically a rod of tungsten that is slowly inserted that in essence acts as an afterburner fuel. Much heavier and denser... capable of much higher dV because of its density. I don't know if its magnetic, but you could have the rods on the outer edge of the bell where the exhaust product would ablate the material and carry it along at 10-15% of the speed of light if the plasma is moving at 30%. Ablation is not the same as melting - and something tungsten is actually vulnerable to considering its other strengths. You'd also want a lot of shielding between the engine and engine bell and the rest of your ship. Magnetic field snapping is a thing, and you would want something to absorb most of that radiation if a reactant arc backfired towards the ship. If your fields are good enough, most of the magnetic products should be able to be trapped in the magnetic fields generated by the bell and redirected back into the fusion stream. But disassociated neutrons might not be so polite. This would be a very efficient engine, and should be able to sustain a 1g thrust until fuel exhaustion even on a massive ship.

[@Reliken]

Paul Vance The books have a plot point around the magnetic bottles of the engines and the destruction that would occur if that bottle failed. You might be right!

[@ZenPunk]

>>>>It would be impossible to get it up to He+ fusion, which would result in carbon product (which would be bad for the crew because carbon isn't magnetic, and would have just as much a chance of firing through the tungsten shield and into the ship... not to mention HE+ fusion would be... well... more than hot enough to vaporize tungsten alloy.

[@Stoney3K]

I'd even go on a limb here and say that the Epstein drive would employ a *resonant* magnetic bottle compared to a regular magnetic bottle that the "torch" drives would use. Think of a cross-breed between the now experimental EmDrive and a fusion torch, which would mean that a lot of the thrust comes from the electromagnetic energy that is stored in the engine and only a small fraction of it is expelled out of the exhaust, only serving as a fusion power source to keep the drive going. It would also explain away the "accidental" invention of the insanely efficient drive by just playing around with it, since it meant that mr. Epstein had inadvertedly configured his drive in some kind of resonant mode leading to a runaway acceleration and unexpected efficiency.

[@mrkacperso8974]

@@Reliken Also in Expanse there is some secondary plot centered around magnetic bottle (or more about what happens when there is no bottle no more)

[@ViraL_FootprinT.ex.e]

I've gone through this series at least three times within the past year and a half, and now I'm watching reactions to it on KZbin. It's like watching it for the first time all over again.

[@erikcharrier5943]

The biggest thing I see missing is radiators. There will be a lot of waste heat that the ships need to dump and the mass flow of the propellant is far too low to cool the engines. The lack of big visible reaction mass tanks requires extreme exhaust velocities. In other words, the drives are spectacular particle accelerators that will make excellent weapons. As a consequence of the power available to ships, there are a few weapons that I would expect to see more of: - Point defense lasers. If you can accelerate a ship at 15Gs, you can operate a laser powerful enough to vaporize rail gun slugs and achieve mission kills on missiles. - There should be particle beam weapons made out of Epstein drives optimized for different variables. - High velocity means that flak or canister shot (from a missile or railgun) can make kill cones that will easily destroy anything without heavy armor. In other words, knowing the approximate location of a "stealth" ship is enough to turn it into Swiss cheese. - Battles should take place where there are huge velocity differences between fleets and it takes them a day or more to turn around and reengage if the enemy survives.

[@Matisaro]

My mental canon is that the epstein drive is a way to take hydrogen all the way to iron in several stages (like a large sun) then it uses the maximised energy harvested from each gram to push heavy iron nucleus for thrust. #mytheory

[@lockwright4110]

@Matisaro ~ What your describing is nuclear transmutation. Science fiction author and former Lockheed engineer Wil McCarthy used this concept as the power plant for interplanetary (in-system) propulsion in his 1998 novel Bloom, where he called it a "ladderdown" reactor. As he observed, it would require the direct manipulation of the strong nuclear force to synthesize all the way to iron nuclei without the pressures present in dying stars. More tellingly, if you could do that, you could make any amount of any element you had the working raw mass to achieve, so there would be no need to harvest water or any other element from around the solar system. In that book, the colonies on Jupiter's moons paved their streets with gold, because why not. But we're talking wormhole and warp drive levels of fun but total BS science magic for that. It's pretty implied that although the Protomolocule seems to take transmutation in stride, the humans in the Expanse still have to get their raw materials the old fashioned way. Fun idea to think about though :)

[@Generalkidd]

So alchemy is technically possible... With enough energy, you could eventually turn water into gold...

[@Psycorde]

Although that amount of energy itself seems more valuable than materials you get at the end

[@MrMonkeybat]

Once in space you dont need alchemy pave your streets with gold there is many times more gold in a single asteroid like Psyche than the Earths crust.

[@DrewLSsix]

MrMonkeybat. A so far unexplored invasion story..... instead of blasting cities aliens should sprinkle megatons of gold over populated areas, effectively destroying all world economy's and leaving the world open for the taking.

[@sergeipoliakov2089]

Haven't got the chance to read the books yet, however, if the show is consistent with Corey's ideas when it comes to drive tech, we probably have a bit more information. Now, as far as I know, the conservation of momentum is still a thing in the Expanse (well, let's not mention that flying potato thing that nearly wiped out the Earth). Therefore, the drive exhaust some form of particles. Exhaust velocity is most likely somewhere in range of 3.7% (Epstein's yacht) and 6.8% (Rocinante) the speed of light. We know that on Rocinante reactor runs on Deuterium and Helium 3. If the fusion result is the exhaust, then it should mostly be helium-4 nuclei and high-energy protons. Although, there might be some additional steps in between the fusion and the exhaust. During the pursue of the Chetzemoka (s5e10), the Rocinante engages with the Free Navy forces and Holden and De Baca mention that the ship is low on reaction mass. Assuming it isn't the fuel pellets for the reactor and not the fuel for the maneuvering system (although, one can't be sure if it really isn't), it might be that whatever this mass is, it may play role in the aforementioned additional steps and be the main component of the drive's exhaust gases. Having said that, I would speculate that whatever fuel is used to power Rocinante's OMS, it is different from the main drive's as it doesn't rely of fusion, since it perfectly works when the protomolecule shuts down fusion on Ilos. The reality, most likely, is that authors do not know how the hell the Epstein Drive works. Most of the technologies in the series are the realistic upgraded versions of what we're developing today -- e.g. viable fusion. Space drives are not like that. Although, there are some possible prospects for ion, plasma or photon, they couldn't provide the effect Corey wanted. So, they went nuclear and created the new type of fuel -- efficiency. By the way, regarding liberal physics with usage of these drives on landing pads and stations. We know for sure that the main drives aren't used near other surfaces. During the landing on Ilos (s4e1) we clearly see that Rocinante is landing solely using OMS with the main drive off. Take a moment to appreciate the thrust of the OMS if it can overcome ~1g of gravity. (That actually makes me wonder how these thrusters operate. Probably efficiency, since I can't imagine hypergolic - or any other systems that provide such efficiency and thrust both in the atmosphere and in space) The same goes for space stations -- during the battle at Thoth station neither the stealth ship, nor the Rocinante use their main drives when maneuvering close to the station. The smaller ships, like drones used at Tycho stations clearly don't have fusion cores and probably rely on chemical (maybe ion?) engines.

[@mattstorm360]

There is no such thing as an unarmed spaceship.

[@datpolakmike]

Idea: the drive doesn't use the plasma of the fusion reaction itself as propellent, instead, it uses the captured energy from the reaction as a power source to accelerate propellent particles. Rather than spewing a bunch of fast-ish and really hot particles as propellent, it uses something functionally like a railgun to accelerate a few cold particles at extremely high speeds. This would explain why they're so efficient and need to carry so little fuel, because they're using such a small amount of propellent to maximum effect.

[@synergy021]

Awe.. I just discovered this channel and then notice the shows are all 3 years old and the creator retired. So sad, good stuff.

[@Claymore_Chicken]

My gripes with this show are the fact that the ships can manoeuvre so easily with just short bursts from the RCS thrusters. Moving several hundred metric tonnes of metal in space isn't easy. And the way that they throw those things around is just so unrealistic, yet everyone praises the show for being the "first TV show to realistically depict space combat". At 5:30 we see him sling-shotting around the moons, and one would only do that to gain orbital velocity, and it would take a massive amount of power to slow down, yet all we see him do is let out little puffs from the RCS, throwing the ship around like it's a fighter. At 6:43 the ship is drifting (with all that velocity from the slingshots) past the blue moon, and when he sees the enemy ship he quickly backs off in the complete opposite direction with nothing but short sustained bursts of RCS. Now I'm no rocket scientist, but I do think my even basic grasp of orbital mechanics would say that this is simply impossible.

[@MattSSPP]

The show producer posted a blog before that episode even aired that the "slingshot" sequence was totally messed up and he apologized for it. The maneuver that takes minutes in the show should have taken weeks, and he admitted that, but couldn't afford to redo the CGI.

[@Claymore_Chicken]

Yeah, I suspected that the budget is the real limiting factor as to why there are so many little things that don't make sense in the show. Like the square corners in the face plates of some of the helmets. Atmospheric pressure doesn't like corners. And the fact that they have one massive engine instead of many smaller ones, in case of one engine being damaged. And the notion of a stealth ship in space, which is utterly preposterous. And I'm not really a fan of the gatling guns in the suit arms. It makes it look too much like the Delta-6 Accelerator from GI-Joe. Having a gatling gun would mean you need a lot of ammunition to be effective in a firefight, and yet the ammo backpack is so small.

[@antred11]

Jackmerius Tacktheritrix I agree. My initial appreciation of this show (and the books, too) is fading. The further it progresses, the more liberally it adds copious amounts of handwavium.

[@5000mahmud]

There is a lot this show gets wrong. However, it is still more realistic than most sci fi shows out there

[@antred11]

+Andy Wilderness You're passing justified criticism off as "whining". This video is literally called "Let's Do the Science", so yeah no shit we're doing to debate the realism on the show.

[@TrophyGuide101]

This isn't the Epstein drive I was looking for...

[@eno2870]

There are most certainly "fuel tanks". The books talk about fuel and ejection mass on numerous occasions.. I've only seen a couple episodes of the show so I can't speak to that. The reaction thrusters are specifically stated to use water as a fuel, though I'm not sure if the drive fuel source is ever stated.

[@themadhammer3305]

From what I've read of the books it's only ever refered to as 'fuel pellets', I've yet to see anything more on exactly what those are but since it's not what the story is about I doubt there will be any more info than that

[@mrkacperso8974]

@@themadhammer3305 There is talk about reaction mass in regards to main engine, like for example when the were pursuing free navy (books) they were running low on reaction mass, and on numerous occasions there is talk about saving fuel to reach their destination. When crew boarded Roci they said that pellets supply will last for years so there would be no need to worry for it to reach nearest resupply point.

[@themadhammer3305]

@@mrkacperso8974 ah I haven't gotten to the point where their pursuing the free navy yet. Thinking back weren't they also worried about fuel after the Canterbury was destroyed and they were running on the shuttle?

[@mrkacperso8974]

@@themadhammer3305 sorry then ;). You are correct about the fact that they were worried about the fuel after the Cant was destroyed, but the shuttle was not equipped with Epstein drive, it had "torch" drive which is lot less efficient than Epstein, they didn't even used it then to avoid damaging the Cant. At least that was the case in the novels.

[@seriousthree6071]

The problem is they don't have enough fuel capacity to sustain 10G, even if you had a perfect fusion engine. Then there is the excess energy generation. You need massive cooling. 1G is much more obtainable. Do not forget the ship has to be slowed down too, you have to turn it around half way.

[@timomuller2784]

There was one episode, where Naomi checked on the propel mass of the roci and was quite worried because they blew out so much allready when they escaped from the donager exploding.. Though it's far from unlimited and the propellant and the fuel seem to be two different things in the epstein drive. There are also several occasions in the book and at least on in the show where they use the drive cone to burn stuff off *gg*. Cheap ships dont have an epstein and just sling shot around: seems to be expensive as well. The torpedos of Earth and Mars are also using epstein drive, I think thats the application with the maximum acceleration we've seen so far (at least for human built application ;-)) The biggest one should be the Navoos drive(s): accelerated with one G for two weeks , reaches the orbit of Pluto, drives shut off and than travels for one hundred years with 5 % of lightspeed to Alpha Centauri... At least that was the plan XD

[@flantastic287]

Wasn't it au Ceti? Pretty sure.

[@sidedace1512]

Tau Ceti

[@mrkacperso8974]

She was worried about reaction mass, not the pellets. She said pellets supply on Roci (then Tachi) will last for years. Idk if it was stated in the show, but was in the books.

[@Ignisan_66]

Both the show and the books mention numerous times that the ships also have "reaction mass" as well as fuel. I believe this reaction mass is water. Water is very common in the sol system, is quite dense compared to liquid hydrogen for example, has a lot of hydrogen in it which improves specific impulse. Plus this water can also be used in RCS for maneuvering and "teakettleing. I believe the energy from the fusion reactor is used to vaporize, ionize and then accelerate the water to tremendous speeds and hurled out of the drive via magnetic nozzle.

[@lfast1234]

#mytheory The problem that seems to be overlooked is heat. Even 1% of the heat from a 1G engine would need huge radiator fins. Somehow you have to dissipate the heat from generating all that energy. And the Expanse ships do not have radiators. The old fission bomb drive, where you blow off small bombs behind a reaction plate has the tremendous advantage that all the heat is carried away with the reaction mass. The Epstien drive will likely follow that model. So the plasma torch is also the reaction chamber for whatever magical fusion system drives the ship. The other piece of magic is dissipating all the heat from internal systems without radiators. Perhaps this heat is somehow channeled into the exhaust? 'Efficiency' is simpler matter. In order to use a negligible amount of fuel your exhaust velocity (aka Isp, Specific Impulse) has to be more than about 10x your Acceleration X Time between refueling. Example: 1 month at 1G requires an exhaust velocity of about 3x10^7. That's only 10% the speed of light. Childs play! :)

[@id104335409]

It's the drive to find, sponsor and transport "young models" around the world.

[@Caddoan]

i like my jokes like i like my skies. Dark.

[@nuvi5480]

In the Cibola Burn novel, (Expanse #4 I think), the squatters were mining lithium as a fuel source

[@starchives2365]

They never mentioned the purpose of lithium. It seems most likely to me that they use pellets loaded with deuterium and tritium for fusion (as hydrogen is the easiest to fuse) and mined lithium to use as batteries

[@tsmcgu]

They make a big deal out of the fact that Martian Marines train at 1G, which strongly implies that the average naval... person (can't think of the term) doesn't. Which implies that the average Martian ship (really crew) could not handle a sustained 1G trip, while the average Earther ship/crew clearly could (they live at 1G). This would seem to mean that Earther ships can routinely accelerate at triple the rate of Martian or Belter ships. Which seems like it would mean they could dominate any kind of long-term engagement (if you have to get ships to the Jupiter AO in a hurry, the ones that can accel/decel at 1G will lap the ones going 0.3G, no matter the distance difference).

[@ZeroRyoko]

What about Muon-catalysed fusion? Perhaps Epstines discovery was the stable creation of Muons allowing low temperature fusion, which would be very efficient. This would also allow the creation of plasma that could be used to disassociate a propellant, one of my friends suggested industrial carbon diamond dust, as this is a dense material space for storage would be negligible and it could be pumped like a liquid. Just a thought.

[@andrewreynolds912]

Really? That's interesting

[@IntheeyesofMorbo]

Since lithium is insanely in demand/valuable according to book 4 (according to episode 1 of season 4) it stands to reason thats critical to the drive. I think its an advanced very efficient fusion based drive using deuterium and tritium created during the fusion process from the lithium blanket used as shielding (or the tritium could be produced in stationary power plants). Maybe some new process makes the fusion anuetronic (no neutrons produced)

[@andrewreynolds912]

You could be correct

[@andrewreynolds912]

I heard anuetronic fusion could be made compact and powerful to power small ships

[@jeffvw1994]

Amazing how the tv series is almost as good as the books.

[@user-vq7eb3eu2l]

7:30 Holy Sh*t! The speed v.s. time analysis is mind blowing. Sitting here for the last 10 minutest trying to wrap my head around what could be achieved with fusion drives. So cool! Thanks for putting it in the video.

[@randall172]

did you confuse fusion and fission? 4:45

[@pseudotasuki]

Repeatedly.

[@SimianConfetti]

the books constantly refrence "fuel pellets"

[@karlfranzemperorofmandefil5547]

@@SimianConfetti it's fuel pellets launched into the drive and then ignited by a laser

[@tracymetherell8744]

Miss your show. Please start doing it again

[@jbeck2k10]

I believe your confusing fusion and fission reactions in your descriptions.

[@dynestis2875]

Important difference.

[@miinyoo]

Neat. That was considerably more well thought out than expected.

[@marekhlavackovi3677]

They also use reactions mass. It is in the show

[@sjerkins]

Once you postulate a containment system that makes a fusion reactor efficient to operate; that implies you have magnetic deflection technology sufficient to deflect plasma from the structural members of a landing bay. In such a system; firing up the engines before the blast deflectors were deployed could result in making the landing bay a molten slag heap. With what we have today; to start prototyping such a technology would require finding a solution to the high temperature superconductor to standard conductor bridge. Then you could generate magnetic containment fields with low enough power and tight enough flux density to make a ship size fusion reactor. Superconductor to standard conductor bridging is a nail which if found would free so many scifi horses to course through the battle for the future.

[@kirkbolas4985]

I recall seeing a “patent” for the drive and the actual signatory attributed as its inventor was signed “Epstein’s Mother”.

[@kellymoses8566]

Thrust: 6,370,000 N Specific Impulse (isp): 1,927,000 seconds Exhaust Velocity (ve): 18,900,000 m/second (6.8% of light speed) Mass Flow Rate: 2.2 kg/second Thrust Power: 60.2 Terawatt Total power output: 96.8 Terawatt Engine's Thrust to Weight Ratio: Presumably over 3 (The Roci has a dry TWR of 2.6) Fusion type: D-He3 (1:2 mixture ratio) Fusion pulse rate: "[what we see] can be achieved with as few as 10 pulses per second, or hundreds if possible"

[@quentinfinck8137]

#epstein #mytheory Could the Epstien drive just be an improved Ad Astra Vasimr drive www.adastrarocket.com/aarc/VASIMR It would make some sense as the fusion reactor would provide the power for the drive. With about 200 years of improvement on the basics of it, I would think that it would fit rather well as the Epstein drive.

[@LetsDoTheScience]

Some variant or similar mechanism seems reasonable. Folks seem a little fixated on the idea of directly dumping fusion plasma to the engines, but an approach like this seems to make a lot more sense. I wonder what the current fuel requirements of this are and how long it lasts. I couldn't find any information and my google-fu is failing me.

[@quentinfinck8137]

arstechnica.com/science/2017/02/nasas-longshot-bet-on-a-revolutionary-rocket-may-be-about-to-pay-off/ Try this article on Ars Technica. It goes into some of the details.

[@Khosann1]

I think we can explain the long travel times with limited supply of available drive mass (also limited ram scoop ability in solar system, if the drive mass is hydrogen). So we should ditch the idea of constant acceleration. If a freighter could travel 5 light hours in 18 months, that would mean 11 hours or so acceleration at 1/3 g. Assuming that half of the drive mass will be used for deceleration, traveling Neptune would take months as books state. So I don't think they did the math wrong (not totally wrong anyway). And yes, I assume fusion powered VASIMR drive.

[@JTMC93]

2350 is roughly when The Expanse is supposedly set. so ~350 years would make the drive amazing. Most likely they use efficiency over all else. Evidenced by ship design and such so they use short burns and Orbital Flight Paths. Possibly using gravity maneuvers to produce further acceleration. Perhaps it is a hybrid VASIMR and CANNAE Drive?

[@corumeach]

As you can see here: www.projectrho.com/public_html/rocket/enginelist.php the VASIMR drive is at the start of the MW drives, while the mysterious Epstein drive is in the highest category, having the highest Specific Impulse of all drives, lest Antimatter MAX. It is difficult to believe, that one can improve a concept so drastically. In the series, the Epstein guy just pumped 4% more fuel to the thrusters and all of a sudden the ship went whoosh. That's pretty naive I guess.

[@paxwallacejazz]

I'm an American jazz pianist living in Copenhagen Denmark and happily just scrape by, without access to the wonderful safety net available to Danes and EUs, but even so, believe me, I live better than I would in the U.S. without having to do anything but play jazz. I've only seen a few episodes at other folks places but I wish I could watch this vision of the future where we make it intact past the the coming climate driven ecological collapse.

[@robertwestfall7561]

Metallic Hydrogen would most likely be the "fuel" used.

[@destroyer1667]

Afaik Metallic hydrogen isn't fusible though so that can't be the case

[@gaming_henry]

I was expecting some math's. One suggestion is to take the Helium3 and fuse it over and over into Iron 56. By containing all this energy in momentum of the resulting iron and ejected protons and throw them out the back, should produce the thrust required from very little fuel.

[@akazlev]

Interesting. But this is precisely why in the end I decided on Reactionless Drive for my science fiction work in progress, to avoid all this fiddly speculation. Just use exotic matter or negative energy to bend space time and be done with it! But for the actual capacities of a real life hard science torchship, see Winchell Chung's superb Atomic Rockets website (which is similar to this youtube, only more detailed, more technical, and without needing to explain pretend stuff). Of course, 10G is impossible, except for a small missile; the power output would vaporise your ship

[@caav56]

Reactionless Drive is a solution that makes even worse problems. Kind of like removing lice by setting your hair on fire. Sure you'll be giving Tyranny Of The Rocket Equation concrete overshoes and dumping it into the ocean to sleep with the fishies. But you will also be giving every space fleet, astromilitary, corrupt corporation, James Bond Villain and little Jimmy in his garage lab access to civilization-destroying relativistic weapons. Are you sure you wanna do that?

[@seth_sesu]

Are your transit time calculations including deceleration time? Or does it assume constant acceleration and flying past the target?

[@aleksadragutinovic3341]

What if its some kind of an ion drive on steroids powered by the electricity from the fusion reaction.

[@john-lenin]

Alien goo that turns children into superhuman space zombies. Sounds legit.

[@HarekYarifind]

Waste heat is the main problem with high ISP and high Thrust fusion propulsion. You need a colossal size radiators to radiate enormous amount of waste heat or your ship will just literally melt away like a snowflake. In Expanse universe ships doesn't have any of them at all. Sorry to say that, but Epstein drive is no more realistic than a warp drive, maybe it will be possible in the future but on our technological level it only a dream.

[@paulshields1883]

but if you can shed the waste heat in your exhaust plume, you'll be okay

[@HarekYarifind]

Fusion rockets can't do that without tremendously drop their efficiency to the level similar to chemical rockets using reaction mass to physically flush excessive heat. That's why huge radiators on torch ship is inevitable evil.

[@cosmicphoto05]

"maybe it will be possible in the future" Like, 200 years in the future. :D

[@toddkes5890]

Until the exhaust plume gets spotted all the way across the system. Check out "Atomic Rockets" There ain't no stealth in space - www.projectrho.com/public_html/rocket/spacewardetect.php#id--Strategic_Combat_Sensors--There_Ain%27t_No_Stealth_In_Space

[@AbeDillon]

+Todd Kes: That guy's writing style is super obnoxious. Did he make up his own internet law and the cite it?

[@FreeThinker79s]

The Problem of D-He3 fusion is that even spin polarized with that it produces Neutron with even in small percentages, will produces huge amount of Heat which we would have to get rid of. A better solution would be fusion based on Fusion of Hydrogen with Lithium-7 the most common isotope of Lithium. This is a pure A-Neutronic type of fusion which would minimize the amount of wasteheat.

[@eitan71]

The Expanse is an AMAZING show !

[@livingod101]

I agree on the efficiency. We already have pellet based fusion technology. And if used "efficiently" a small pellet could generate a lot of heat and it could be a chain of events. A fusion happening to small pellets which heats up reactionary pellets creating more heat which could turn certain compressed matter from solid to pure ions and electrons. Capture the electrons for energy and ions as thrust.

[@weepingod]

very unfortunate name

[@piotrd.4850]

That's why realistic sci-fi is hard. For otherwise wonderful Expanse, there's singular fallacy here, aside space debris. There's little need to ARM the ships - exhaust from RCS or main drive will have more power than any weapons complement (common for all sci-fi). Point and shoot - and there you have it. Not to mention, navigational risks...

[@velucadhirim6725]

This video did not age well

[@bigpharma2705]

Why?

[@patryn36]

The drive is a two stage drive system, first you have the hydrogen fuel pellets used to initiate fusion, second you have driver coils accelerating the plasma similar to what the dawn probe used. The main difference between the dawn probe engines and the epstein drive is that the dawn probe is mainly limited by available power, solar power, the epstein drive is the power source and the fuel for the driver coils. Aside from a few elements of material science, we can build those drives now, all that is needed is sufficient orbital infrastructure to build and twerk everything.

[@fortkavanagh]

I think it's some we haven't discovered yet?

[@rowshambow]

Thanks for the day numbers on the flip and burns between the moon etc

[@rileyboomer8627]

"Use #epstein so I know you made it to the end" well that didn't age well at all did it

[@henrikskjolden]

Randomly stumbling across this channel and watching your expanse videos I must say I came late to the party after reading your "about" section. I hope you one day find the time to return as this is some proper quality content without any unnecessary bias! :)

[@nightcaste]

Neutron radiation IS ionizing. If you're going to call your channel "Let's do the science", maybe you should actually know what the hell you're talking about, or at least take 20 seconds on Google.

[@cinquine1]

Well it's not directly ionizing, because neutrons can't excite electrons at all. When neutron radiation is absorbed by a nucleus then the nucleus can emit ionizing radiation. We call this indirectly ionizing radiation, and the distinction between the two is important.

[@BananaBLACK]

Is that the differnce between Alpha and Beta particles?

[@cinquine1]

-Alpha particles are fast moving helium nuclei, beta particles are fast moving electrons (or positrons).- Disregard, I misread your question. No, both alpha and beta radiation are directly ionizing.

[@weylin6]

I don't know why they call it ionizing when it's more... isotopinizing

[@BananaBLACK]

I am doing my research from the perspective of radiation poisoning treatment. I was under the impression that alpha particles are not nearly as destructive as beta, when it comes to organics. In fact can be scrubbed off, but left lodged in a biological system, decay into beta particles. Causing delayed symptom. Am I on the wrong track? I have been trying to put together an Encyclopedia of Survival. Everything from lone survival to civil survival. It turns out there is as many treatment for radiation poisoning as the are types of radiation.

[@TonboIV]

Rather than being concerned about how the drive produces energy, heat is the biggest problem. A nuclear reaction certainly can produce huge power levels, and the drives in the Expanse certainly must operate at very high power levels given their thrust and isp, but this necessarily comes with huge heat, no matter how it's done or how efficiently. The ships seen don't have large fuel tanks, meaning there's only a small amount of exhaust to carry away waste heat, and there are no large radiators seen either.

[@namyun2743]

@TonboIV How the drive produces energy is a SCIENCE problem. Dealing with the heat byproduct is an ENGINEERING problem. Without the former, the latter doesn't matter.

[@smackerlacker8708]

You know you're a nerd when you watch Sci-fi and ask yourself "How do the engines on this space ship work?", instead of the question most non-nerds would ask "OMG, that outfit looks so tight, how can she breath in that?".

[@Knervik]

@7:29 "Constant 1g acceleration" is much easier spoken of than accomplished. Exponential increase in energy input is necessary to maintain it.

[@Billy420-69]

That jerry curl halfro is distracting.

[@cosmicphoto05]

It's what all the cool kids will be doing 200 years from now. :D

[@claudianreyn4529]

If they use metals, those could be one of these: Aluminium, Scadium, Titanium, Vanadium, Chromium, Manganese. The Aluminium > Iron cycle could be interesting, probably the first one that comes in mind. How much energy would create that, would be a good question.

[@DaNuker]

the name didnt age well lool

[@SIrL0bster]

I think you're pretty much spot on- It has to have a very high energy capture to work- However, there are aneutronic fusion reaction chains. Those don't produce neutrons that need to be captured. After that, you can get very high efficiency fusion by capturing energetic particles directly from the confined plasma. An Inverse cyclotron converter has a theoretical maximum of 90% energy capture. The remaining 10% (which would be pure heat) you can probably use as a pre-heating cycle for your reaction mass, and that probably would already get it to a plasma state. From there, just use electromagnetic type thrusters to dump as much energy as you want into the reaction mass, and off you go.

[@martinwatson2005]

I’ve really enjoyed your programs; it’s a shame you had to stop making them as they are a great idea and well executed. Thanks.

[@DWCmoose]

The books also mentioned they use water as their ejection mass, so water + heat is the only thrust they're using. water responds to strong EM fields, so accelerating the ejection mass with coils like in this type of space drive : en.wikipedia.org/wiki/Magnetoplasmadynamic_thruster

[@howardmiller5381]

Currently, ion drives are being used for long period thrust. It ionizes a gas like xenon, then uses electricity to accelerate the xenon nuclei. It's not much thrust, but the power comes from solar cells and can go on for a long time. Replace solar cells with nuclear power and a large amount of plasma, which is, like ionized xenon, a gas stripped of electrons, only a whole lot more of it. Now you have a nuclear drive, all components of which already exist. The next step is to use magnetic fields to compress and fuse the plasma. We're creeping up on that step now. The next step would be to inject more plasma after fusion, then fuse it again. You could start with hydrogen (two atoms per molecule of water), and fuse it to helium. The fuse a hydrogen nucleu and a helium nucleus to lithium, or two helium nuclei to beryllium. That would be pretty efficient. However, it's not the Epstein drive, but maybe it's a way to get around the solar system. You mentioned that water was a valuable commodity in The Expanse. Every habitat would have some leakage, but water would be constantly recycled. Maybe massive quantities of water are needed for it's hydrogen. Oh yeah, the oxygen would be useful too.

[@Canofjuice72]

Wanted to interject with some updated science here. There has been a lot of work recently into using boron fuel cycles for Fusion reactors (specifically mentioning the 11B(p,α)αα cycle in this comment). This produces next to zero neutron radiation. What it does produce however, is a final product of Helium3, which allows for the use of a direct energy converter (a device that converts the kinetic energy of high-speed particles in a magnetic field directly into usable electricity. We do hear a lot of talk about reactors leaking radiation in the expanse so there could be something else going on, but this type or reaction is currently the way forward. Right now, the classic deuterium-tritium reaction is used simply because of its stability at low temperatures. It has sever drawbacks in nearly every other regard. Meanwhile a boron fuel cycle requires something on the order of six billion degrees in order to be efficient.Believe it or not though, we're slowly getting there. What we could be seeing is a fusion reactor providing gobs of power for some kind of hyper-efficient VASMIR style plasma rocket. However I'm not sure what kind of crazy superalloy you'd need to act as the RF heating element inside such an engine at the scales we see in the show.

[@MatthewCallison]

Thank you for your comments. I think that there is some sort of hand-waving-ium for the Epstien drive, but I loveThe Expanse. Thank you for your input!

[@KnoppersBomber]

As far as i undertand from Epsteins explanation as a narrator it's basically a conventional engine "turbo-boosted" using magnetic coils around the nozzle (similar to the Biefeld-Brown effect), powered by a fusion reactor. That's why Epstein expected only 10% more efficiency. He didn't develope an entirely new drive, i strapped a turbo to a regular engine. It's the perfect analogue. You can increase a combustion-engines efficiency by a multitude by adding a turbo-charger. Edit: my second theory is that Epstein used a conventional atomic engine and somehow increased the output of it's heat-elements using a fusion reactor.

[@John73John]

Regarding fuel, in one of the books (4 or 5 I think) the major conflict is over a large lithium mine. I don't remember if it was explicitly stated, but it was at least strongly implied that the lithium is primarily used for the fuel pellets. Fuel pellets were mentioned numerous places in the books, whether they're pure lithium or lithium combined with something else (i.e. deuterium, tritium) is unclear. In other places the books talk about using water as reaction mass. In one book a ship has plenty of fuel pellets, but is running low on reaction mass (water). This isn't "flying teakettle" (see below) this is using the fusion + water to directly produce the thrust. Flying teakettle also uses superheated steam, but it isn't coming directly from the fusion reactor. It's done on some small short-range ships that don't even have a reactor, they heat water with electricity from batteries or solar panels for example. This is also how the maneuvering thrusters on even the fusion-equipped ships work, with electricity supplied by the reactor.

[@WolfeSaber]

I see the engines are a combination of NASA's VASIMR engine and fusion engine. I also see forward intake vents on some of their ships. Now, I see the engines more of as aneutronic reaction engines based on what I saw in Season 4. We see solid pellets being blasted. These could be the protons needed for the reaction. Plus, the colonist were making a big deal about the lithium, a fuel for aneutronic fusion. As for the secondary reaction talked about, the alpha radiation given off could be used in a direct fusion reaction at the nozzle for more power. Along with a gas or some additional mass going down the nozzle and we might just have our Epstein Drive.

[@thomasboomer9809]

#Epstein. Always loved your shows because the best part of the Expanse is how the creators try so diligently to get the science right. The average viewer doesn't know that, and your presentations really bring out those details for everyone.

[@JcBravo8]

The science is bonkers but what makes it seem real is the consistency in the aesthetic worldbuilding.

[@Forgan_Mreeman]

when I hear people talk about how the epstein drive might work no one mentions that episode where we got a look inside one of the drives. it was some episode in the 4th season I think (?) where they were in the ring space and all the ships inside it couldn’t move because “fusion was no longer working”. when Naomi tried to start the engine we saw a black sphere get released into the drive and it was struck with something, it exploded and then they were able to start their engines. that scene feels like a big clue to how these drives might function

[@JohnAlthaus-jz8bo]

Well this rocket will never kill itself.

[@garretstephenson8700]

A lot more is described in the books than is presented here. The fusion is done via fuel pellets and lasers. The opposite side of the Rossi from the cargo bay is the reaction mass water tank. The common 1/3g thrust is explicitly stated to be used to conserve this reaction mass.

[@dawall3859]

The best candidate I can see it being is focus fusion. In that form of fusion you create a magnetic plasma and use the inherent instabilities in it to create a plasmod. In that plasmod you will have nuclear fusion taking place. Out of one end of the plasmod you will produce an electron beam and out of the other a neutron beam. It will also give off X-rays and microwaves all of which can be converted into electricity directly with no radioactive waste.

[@jaslarja]

2:50 neutron radiation is definitely ionizing radiation

[@deusexaethera]

#MyTheory is it's a fusion-powered Hall thruster that uses solar plasma as reaction mass. Water is unlikely to be used as reaction mass, but it *could* be used as radiation shielding in a double-hull design, because water is extremely good at slowing and capturing nuclear particles moving at relativistic speeds before they can shred important things. As a bonus, capturing "fast" neutrons using water will produce deuterium, which is an excellent fusion fuel, so surrounding the reactor with a water jacket is one way to recapture some of the energy wasted as radiation to breed more fuel for the reactor. Alternately, it could be a thermonuclear drive, which uses a small amount of fusion to induce fission in heavy nuclei, such as uranium, mined from the asteroid belt. Those heavy nuclei would make even better reaction mass than solar plasma, though it would require carrying the reaction mass onboard the ship. Or perhaps this is the "torch drive" that preceded the Epstein drive.

[@thatxmas]

#mytheory (4 years later) - The fusion reaction is used to create a charged plasma that contain the fusion material and a metal to add mass to the exhaust flow. The plasma can then be electromagnetically accelerated and focused out through the engine nozzles. I was thinking Nickel, Iron or Cobalt would be common enough.

[@danielfernandocarballo1890]

To begin with, suppose that the standard propulsion of spacecraft before Epstein used a mixture of deuterium and helium 3, which fuse with some ease. The result would be a mixture of deuterium, helium 3, helium 4, neutrons and gamma rays, at a temperature of several million degrees. Depending on the degree of efficiency, the initial fuels would be transformed into merger products in an amount of 5 to 10%. The finding of Epstein could be a way to increase that percentage to over 50%, which would give more than 10 times the previous push. For example, increasing the pressure at which fuels are found or finding a way to reflect the fusion products back to the area where the fuels are joining. If, in addition to that, something like Lithium 7 is injected, it can absorb the neutrons, and the resulting Lithium 8 can be broken into two helium nuclei 4, which increases even more the total efficiency Everything is based on the possibility of creating fusion engines capable of occupying a few cubic meters and achieving efficiencies above 5%. The bell that guides the plasma (without touching it, because it will evaporate) is not included in these measures. A water tank of several thousand liters would brake any escaped neutrons that went towards the crew quarters.