Explaining Fusion Engines in Realistic Sci-Fi 

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Interesting fact: fusion has a declining return on power output the heavier the elements you use. Fission on the other hand has a diminishing return with the lighter the element you use. There is a point where both fission and fusion return less energy than what you put into them. That point is the element Iron. The element where nuclear power dies.

If you can bend space and time for the sake of faster than light travel then you can probably produce fusion by simply condensing the space around the fusion fuel until it achieved the pressure of a star. If you can produce gravity artificially under the floors of your ship just for comfort and health of the crew, then you can focus that effect onto a piece of fusion fuel.

Projectrho is strong with this one .

Crossing my fingers for a video about a nuclear salt water engine. The probably most insane, but achievable, engine concept ever devised.

I love the depiction of "Cosmic Rays" :)

"Has advantages, such as not needing gigantic radiators" I don't know that kinda sounds like a disadvantage to me XD

You missed the most obvious alternative of electric confinement fusion or Farnsworth-Hirsch fusor. This design works like an ideal fusion engine from the start (very little modification needed of the reactor) and can be fed with B-11 and hydrogen to produce a fairly clean fusion process with only helium/alpha particles as a side product. It could theoretically have insane specific impulses and pretty good thrust to weight ratios.

Terra Invicta puts a lot of effort into implementing all sorts of propulsion mechanisms in for the player to develop and use on their ships - for good or bad. Yes, you can have an Orion-based design, lots of crappy ion engines, or eventually work your way up to actually good inertial confinement drives.

I'm very late to the party, but I just wanna say, if you want to use high-thrust fusion engines in your setting while still making it sound realistic, you can limit it to Solar System only. We don't really need more than a few hundred km/s of exhaust velocity even to Pluto; we don't have enough time to reach higher velocity before the flip-off point is reached. Since fusion engines are capable of spewing its byproducts up to 1000 km/s, we can easily trade some excess velocity for higher thrust.

Suggestion topic: asteroid mining Examples: EVE Online, The Expanse, Don’t Look Up

So, as part of an extremely expansive crossover AU I made a concept for a fusion reactor+engine that would have been made by Aperture Science. The key thing to remember with them is that although they are extremely smart, they also happen to be tremendously stupid and silly. So, the reactor part of it essentially used highly complex gravity fields to house an artificial star, with two exit points at the poles. Extremely energetic jets of fusion plasma would be emanated out of the artificial star and then piped into a series of pistons, literally just steam locomotive pistons in regards to design. Those pistons were hooked up to either solenoid or dynamo generators, but that’s whatever. This version of Aperture Science didn’t have anything strong enough to make turbine fans that could withstand fusion plasma, but they did have concepts for having twisted magnetic fields to create a sort of magnetic turbine fan in later iterations of this fusion reactor. The plasma would then be routed to a thruster mostly as just a way to utilize exhaust since they can’t just dump it Willy nilly like steam exhaust, but there is a sort of 'afterburner' system that would create a complex linear gravity field to fuse the plasma an additional level up the stellar fusion chain. Main reactor fuses hydrogen to helium, afterburner fuses the helium together.

Could you do a video on exotic sublight engines? Things like Star Trek's impulse engine are exotic due to their function being very different from other drives, either due to the engine itself or due to other mechanisms (like the impulse engine is plasma directed to the needed port instead of just dumped out the back)

Always love seeing starsector clips

I literally had this wait a second and process why is the spell jammer,(a giant magical, manta ray that swims in space in D&D )was an episode about fusion. Cosmic rays I go to bed now.

As a bonus, this also counts as a video on sci-fi weapons, per the Kzinti Lesson.

One thing to note about the IRL fusion : While they did manage to "produce" more energy than they "put in", they didn't manage to extract said energy, nor was the goal being actual power production. And the energy that they "put in" ? That is referring to the laser doing the actual fusion, not all the electricity that went into making the laser and powering the machinery. TL;DR : It was not power-positive by a long shot, and the goal wasn't producing power anyway.

Spacedock is unironically one of my favorite youtube channels currently! I was wondering: if you folks could make your dream air force (can use already existing aircraft or design your own), how would you make it? Also, what would be your dream realistic fighter jet (invented from the ground up)

Kudos on correctly using Saturn vs Jupiter for the location of the monolith. 👍🏼

The X4 soundtrack was a good choice for this video!

At 5:55 "....greater than a hummingbird's fart...." That was pretty good, I had to stop and laugh at that!! Thank you....

Another interesting concept is the VASIMR-engine which is basically a rocket engine with a gear shift (I hope I found the correct translation). This "gear shift" enhances the engines propellant efficiency as you can adjust the drive to the situation you are facing. The concept isn't specifically designed for fusion but it can be used to power the engine and boost its thrust.

Magneto-inertial drives also have a second, similar variant The magnetized target fusion one But the principle is the same. Use mass to squash mass until it fuses. So instead of using lithium foil, you can use deuterium to squash deuterium to fuse, by spitting it at the plasmoid in the middle at high velocities, then throwing some propellant on it afterwards. This version can achieve high thrust for its efficiency. (for any inaccuracy i apologize) I love Atomic Rockets, and how its author, Winchell Chung writes it

This video is excellent. For completeness, I should point out that in the 1995 computer game called "Mission Critical" by Legend Entertainment, the description and portrayal of the US Navy deep space light cruiser Lexington is impressively rigorous. The Lexington has a chemically-powered orbital maneuvering system and four aft-mounted fusion engines. The engines are fed via linear accelerator on the centerline of the vessel. It drives deuterium and tritium fuel into a pressure vessel, where inertial confinement fusion occurs via compression lasers. If I remember correctly, the Lexington is capable of a maximum acceleration value of 7 gravities when it is in normal space. The habitat module has the decks oriented in the proper direction relative to the axis of thrust. The vessel's exact dimensions are not stated, but I estimate the Lexington to be 260 meters long with an 88-meter beam and an 85-meter draft. The vessel is designed to be very fast, lightly armored, and heavily armed -- with a typical crew of 20, a maximum crew capacity of 25, and a primary role based around the employment of up to 18 unmanned combat space vehicles. She also has a few close-in weapons for use if things do not go according to plan. There is no magical inertial damper technology in the game. The design of the ship does have several intentional departures from scientific realism for narrative reasons. It includes an FTL jump drive and omits temporal dilation. Furthermore, the Lexington is depicted as deriving its electrical power from a pressurized-water nuclear fission reactor, similar to those found on modern submarines. This portrayal is unrealistic for a ship authorized by Congress in Fiscal Year 2111, as one would expect the Lexington’s power reactor to likewise be of the nuclear fusion type. I believe that departure was likewise for story purposes, so as to have a way to create dramatic tension through the danger of a power reactor meltdown once the Lexington becomes severely damaged in battle.

Yay I'm glad you touched on this topic. Scott Manley did a really interesting video on it as well so this got me hooked.

I'd be very interested in seeing a video about planetary defenses, concepts of orbital defense platforms or ground to orbit gun/missile battery's and such. I've always thought building sized artillery is bad ass.

For me the biggest thing in sci-fi isn't that it needs to conform to the real world and what would work in real life. For me what matters more is that it establishes and follows consistent rules within its own setting. Sci-fi is Science FICTION. I have no issues with a fictional story making up its own rules. But I do want them to follow the rules. Don't waste our time setting up something JUST so you can break it later. If you want to just disregard a real world limitation, fine. But then you have established how it works in your setting. Now THAT is how it works. Be consistent with that rule. I love the Expanse and have read the books several times each. I feel they do a very good job of being consistent within their own fictional setting. Star Wars is another personal favorite but a great example of failure to do this. As depending on the movie or book and even sometimes within the same story, the rules of spaceflight and what ships can and cannot do, are not consistent. Hyperspace and the hyper drive are fictional concepts and how they work and what they can do is not consistent across the franchise and it annoys me.

It would be awesome to see a similar video to this about fission drives!

The one thing Star Wars and Star Trek & a lot of others have always gotten wrong is, there is no top and bottom in space. The Expanse got this right. On an ISD in REAL space would look weird on its side and dumb reversed with the mast on the bottom. The Borg Cube starts to seem to be the most logical design. How weird would it be to approach the Galaxy Class with the saucer section on its side or on the bottom? These S.T. & S.W. ships all are based on the idea of surface water ships. The Expanse corrects this very well. Almost every ship is based on the principles of this very argument.

LOL!!! Those Cosmic Rays are of EPIC proportions!!!

I approve the X4 ost as background.

Add centrifugal force to a fusion reactor would be very efficient in terms of mechanics

I imagine two stages, though, not how we think of rocket stages. The first stage is the burn stage in which we use fuel and burn it to start moving the craft and gaining initial thrust. The second stage is the cruise stage in which we use our fusion reactors to power massive ion drives. That, more than anything, would be the ideal solution (I think, as far as near-term technologies go). Also, fyi, we wouldn't discard any of the stages in this, since they're just two different types of engines which move the ship and they rotate which ones are on/off depending on the situation and "stage".

If you're not familiar with it, the anime Outlaw Star has a focus on "grappler ships" that basically got started as tugs/utility craft until pirates got good at fighting with the manipulator arms. The hero ship is a high performance grappler ship.

I don't care what video about. I see The Expanse - I press like

For the "Zeus-nuclon" nuclear tug, the use of thermonuclear fusion was being worked out as an increase in thrust. Since in order to increase it is necessary to increase the temperature. But so far we have settled on rotary magneto-plasma engines.

I look forward to this great content

Fusion exist some sci fi guy: *Helium-3 is loaded* They dont even realize theres bunch of heavy element you can use as fusion fuel

Fusion engines only makes me think of the end of Halo where they blow up the Pillar of Autumn to destroy the ring. Now when I see that scene, I think of how a weaponized fusion engine would essentially create an artificial star, not too far off from what we see in the cutscene.

I KNEW MY IDEA ABOUT THE ENGINES CAUSING POSSIBLE DAMAGE TO THE SHEILDS WASN'T STUPID. I can full explain my Fleet tugs as possible things.

I want The Expanse back... :/

Haha that cosmic ray graphic… 05:39

No matter if fision or fusion but the real problem in space is colling.

very nice perhaps have a look at the 'Astrosling'

I wasn’t prepared for the cosmic ray 😂

3:31 You know, I'd give anything to see you feature some insights on all the Spacecraft/Stations from For All Mankind, such as: *Lunar-modified Space Shuttles* *OV-2XX Pathfinder-class NERVA Shuttle* *Helios Phoenix Interplanetary Spacecraft* *Mars-94* *Sojourner-1* *Jamestown Lunar Base* *Zvesda Lunar Base*

Im very surprised you didnt mention Mechwarrior/Battletech, as fusion engines are prominently used in them. The mechs run on a hydrogen fusion reactor, heavily shielded from radiation and held in containment with a powerful magnetic field.

i was like, where's Orion. I feel validaded. Suggestion, when you do Orion eventually, please, use Troy as an example.

A more recent of fusion ignition system uses 'small', opposing linear particle accellerators to create the heat and maybe pressure for nuclear fusion (I forget the exact details at this point). They can start and stop the fusion process many times a day. It uses an unusual, compact super conducting linear magnet design that has been known for years but almost never used.

Fascinating as this all is, it really gets the seal of authenticity by being illustrated in Kerbal Space Program 😉

You missed the akimbo sawn off double barrel shotguns from Bungie’s 90s Mac classic Marathon 2. I remember the in-universe description from the manual, which was written in the voice of the self-aware AI Durandal, saying something like “I won’t bother explaining as your primative brain wouldn’t be able to grasp its operating mechanism” which is some pretty fun shade.

Cosmic Manta Rays.... brilliant.

Great video...👍

Cool video, SpaceDock!

The "Real Engineering" channel here on youtube has a couple of really good videos on the current state of fusion technology from 5 months ago.

more video like that will be nice

Spacedock/Kerbal crossover? Epic

So the music credit is for Battlezone II but sounds like X4 Kingdom End

You don't need energy positive-fusion to generate thrust. You could have a fission reactor to make up the difference, and provide power to a fission drive that consumes net energy. In that case, use fusion as a way to get an engine with large mass flow (and thus large thrust) very hot exhaust (high fuel efficiency), while not actually needing a viable net-positive fusion power technology. Some form of nuclear propulsion (fusion, fission, or hybrid) is pretty much mandatory for non-fatal regular human interplanetary travel, especially for any planet further away than Mars. The energy involved also means gigantic heat radiators, unless you use something like metallic dust radiators or liquid tin radiators.

I did not expect to see Kurzgesagt here, but looking back? It only makes sense

It seems no one approaches internal confinement fusion by focussing the outbound shockwave of the fusion into the next target. Im thinking of a reactor in the shape of a unilluminable room.

What if you used the "Afterburner method" on a fissionable material like nuclear-salted water? Wouldn't use nearly as much of it as a standard nuclear-salt engine, and the fuel wouldn't need to be enriched so heavily with uranium or fissionable material, the heat and charged particles should be enough to induce fusion in the water molecules, the fissionable material still undergoes a chain reaction while remaining sub-critical and safe when stored, wouldn't need nearly as much neutron absorbing material around the fuel tanks, saving on containment weight.

I guess antimatter-catalyzed fusion will be part of an episode on antimatter drives.

I always thought if you had the gravitational mass of a star you could pump out speed for quite some time.

Who'd-yanna.. Who'd-yanna be, A Jedi?

Like the use of far future tech mod, basically the only “”””realistic”””” expression of fusion and nuclear fragment propulsion

Nice video.

Kinda hoping and (kinda not) to see the engine(s) concepts I developed for my Sci-fi setting to be featured but so far haven't seen them. Though Spacedock seems keen to focus on realistic Sci-fi based on emerging, modern technology.

A bit out of date (3monts after video published) as Starship now has even. ore powerful V3 rocket engines and will continuesly get even stronger and better.

Helion is looking sparky too right now. No not the Riddick system, the plasma playing chicken system.

main issue I see is you still need more than half the ships "tonnage" as reaction fluid no matter how efficient the drive is.

Well no, energy from fusion reaction can be used to produce electricity that will be the main mean to power up ion propulsors. Ion propulsors uses gas ionized to push a spaceship into space and its actually a sort of "tier 3" type of propulsion in a scale from 4 to 1 of types of space travel. We are currently at tier 4. With chemical propulsors that are not reliable to fly in space. At tier 2 we will have stuff like direct nuclear thrust or a ti-matter thrusters and warp etc. At tier 1 we will have hyperspace. Those techniques that will allows us to open a wormhole into space to travel from a point to another in exactly 0 seconds. Well, technically it will be "-1" but... Unfortunately we spend absolutely nothing on these technologies, so we expect to obtain such things just in two or maybe three centuries. 🤗 No less.

Thrust greater than a humming birds fart. LOL

Yesterday, today, and tomorrow: fusion is the power of the future.

That feeling when you wanna make a fusion reactor, but you can't figure out how to stop the emissions' blatant subversion of phase velocity.

Look, does a Fusion-based Linear Aerospike engine that uses powerful magnets in the aerospike center-body walls make sense and have any realistic chance of not immediately destroying itself? Probably not, but I'm using it in my sci-fi ship anyways cuz it looks cool lol

diesel can be use as a fuel for interstellar travel just check fast and furious 12

Ok but why so little thrust? If plasma pushes on the ship the same way gas propellent does, shouldn't it apply more force? Is it just a mass thing because inertia should be taken into account.

Question: Why is the magnetic containment field in a fusion reactor sometimes called a "magnetic bottle" (or just "bottle")?

Of course Kerbals are going to be in there somewhere.

Does the name David T. Adair rings a bell? 4.5 seconds of sustained nuclear fusion, in 1971! "Pitholem" nuclear fusion engine rocket? No? Anyone?

Now I will assume for the nif you knew about the lasers but not the whole system for it. I can appreciate the hype everyone has for the news, but its only true to an extent. In reality it is still far away from net energy gain and updated there lasers could get there but I dont think there budget will allow that anytime soon.

I am disappointed that you didn't mention the magnetic reconnection drive.

I just got a Pfizer advertisement with this video. Apparently science fiction is safe for Pfizer!

Probably talking around 150 - 200 years before we have fusion drive spaceships. But they should open up our Solar system for future generations. This is when exploiting the mineral wealth of asteroids could become reality.

Those darn Cosmic Rays! :/

You forgot about field-reversed configuration magnetic confinement reactors.

Seems most series forgo reaction mass or at least handwave it away. The only series I remember that uses it was the RCN series by David Drake which uses antimatter but only in vacuum for obvious reasons

I have been waiting 😂😂😂 finally

Is it possible to get a fast fusion engine running without any secondary propellant?

OK, after finding my math mistake (dividing instead of multiplying and coming up with 1/15 my walking speed). 1.4m m/s = 1400km/s = 5.04m km/h

It's hard to have a realistic torchship and simultaneously not also have a weapon of mass destruction. Pretty much impossible.

I'm curious if a fission-fusion engine might be viable for sci-fi

That's the deal with the hydromagnetic drive or something?

Starsector, nice ^_^

Did anyone mention the Star Trek phaser?

Echolance is my favorite realistic ship design. Doesn't use fusion. Most luxurious one way time machine.

Well, the sun throws a hideous amount of radiation too.

The one thing that is missing from Discovery 2 is Hal.

What if there was a propeller, oar or fin which could interact with dark matter? That way you don’t need propellant, just power generation.