Friendly Neighborhood Kerbonaut’s guide to Far Future Technologies’s Engines

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Disclaimer: English is not my first language, I will definitively make mistakes or formulate sentences weirdly.

Some parts of the images are in Italian, but all the important parts are in English.

 

Note: KSP’s Delta-V readout can be unreliable with those engines, Kerbal Engineer Redux is recommended.

 

Premise

The intent of this guide is not to tell to Kerbonauts how to play the game, every player have different style, and the beauty of the game is that there is more than one right way to do everything.

I will only explain what is required to make the engines work, give my opinion about the strong and weak points of every engine, give some insight, share my experience and some basic design of ships.

 

Chapter One – A general introduction

Chapter Two – Be Cool

Chapter Three – The Fission Engines

Chapter Four – The Fusion Engines

Chapter Five – The Antimatter Engines

Appendix One – Balancing Fuel

Appendix Two – Burning Like Nobody Is Watching

Edited Wednesday at 06:07 AM by urturino

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Chapter One – A general introduction

 

Nertea divides those engines like this:

3 category, Fusion, Fission, Antimatter, each category have a Torch Engine, engines so good that the others look like garbage compare to those.

Let’s try to see the differences between those engines.

 

Fuel:

6 out of 15 engines can switch on flight between 2 modes.

I will talk later about the difference between the two modes, for now let’s only talk about what fuel tank those engines want to work.

 

Antimatter Engines are pretty consistent, they use Antimatter, and accordingly with their category, at least another type of fuel:

Deuterium+Helium3 for Fusion

Fission Pellet + build-in Ablator for Fission

Liquid Hydrogen for Antimatter

 

Fusion Engines are also pretty consistent.

Almost all of them have a mode that use Deuterium+Helium3 + Liquid Hydrogen.

3 of them have a Deuterium + Helium3 mode (It’s not a mistake, both Hammertong’s modes are D+He3, and both Discovery’s are D+He3+LH2).

And the only exception is the Impulse that needs Lithium and EC.

 

Fission Engines is a jungle, where (almost) every engines have a different fuel.

There is 5 types of Fission Fuel:

Enriched Uranium, witch is build-in in the only engine that use it.

Fission Pellet, witch have it’s own tanks.

Fissionable Particles and Nuclear Salt Water, that share some tanks.

NUK for the new Orion Drive engine.

 

Charging

6 out of 15 engines can be used like every other stock engines, you turn them on by staging and they are always available, you just have to throttle up and they will burn.

The other 9 require to be charged before be turned on, but they don’t work all in the same way.

4 of them, 3 Fusion and 1 Antimatter, have a build-in fusion reactor.

They need charge to startup the reactor (which use D+He3 and produces EC); As long the reactor is running the engine can be use like any other stock engine, it’s always on, always available.

It’s up to the Kerbonauts to decide if leaving the reactor always running (and use the EC produced as primarily source of electricity), or turn on the reactor only when the engine is needed and using another source of EC during the long journeys to save D+He3.

From now on I will call those engine “Reactor Charge”.

 

The other 5 engines don’t have a reactor, it’s the engine itself that need to be charged to startup.

Witch mean they will turn off completely and need a new charge every time they will be throttle down to 0.

Rendez-vous with those engines can be a painful experience, and many Kerbonauts could prefer to have a strong RCS to make Rendez-vous easier or at least enough batteries to charge them 2-3 times at the faster speed available (every engine has a minimum time to charge, but it can be slowed down).

Note: The engine must be turned on at every use, you can do it manually from the PAW menu of the engine or with an action group key, but if the throttle is still to 0% when it’s turned on it will shutdown immediately and it will need a new charge.

From now on I will call those engine “Engine Charge”.

 

Thrust and ISP

First of all, there is a thing you need to know: Two of those engines have variants, witch mean their weight and TWR will change accordingly to the variant used.

They are the Fresnel and the Frisbee.

Frisbee have variants between 32 tonnes and 84.5 tonnes, thrust and ISP stay the same so TWR will drop in heavier variants, the advantage is that heavier variants need less radiators.

Fresnel have variants between 26 tonnes and 50 tonnes, thrust and ISP increase in heavier variants, but so does heat production.

(For every category, this is the order you are suppose to unlock the engines in Science and Career.

For the Fresnel it’s indicated the heavier variant.)

What do we notice?

First, almost every multi-mode engine is more powerful and less efficient in mode 2 (Impulse is the only exception).

Second, not all Far Future engines are incredibly efficient. Many of them are less efficient than a Ion engine, but obviously they are different types of engines and must be used for different purposes.

Here is the same table with the engines ordered by ISP.

You will not make an interstellar generation ship with engines like Impulse, Discovery, Hamilton or Verne. They are not intended for that use. Even with futuristic technologies those engines are still subject to the Tyranny of the Rocket Equation.

For now it’s enough, we now have a general understanding of those 15 engines.

We still have no idea of how to use them, we barely talked about radiators, witch are extremely important to use those engines.

 

 

Chapter Two – Be Cool

This chapter is not about cool design for ships. Before dive intro the engines, let’s me talk about cooling system.

All the engines except the Hamilton produce heat, and will shutdown after few seconds if they haven’t enough radiators to cool them down.

Stock radiators are useless, too weak, you need something better, and luckily Nertea himself solved the problem with the mod Heat Control. You are all strongly recommended to install it.

Build-in with Far Future Technologies, System Heat is the replacement to stock heat system of Nertea; Far Future Engines use this system to calculate the temperature of the engines.

We don’t need to go into the details of how it works, the only important thing to know is that every System Heat’s parts producing or radiating heat is in a Loop.

The heat of a loop stays inside it and can only be radiated by the radiators of that loop (there is a part for moving heat from one loop to another, but that is not relevant to this discussion). Nertea provides a tool, available in the game’s toolbar, that tells us if loops are radiating more heat than they are producing.

Why is this important? Why you can’t just put a lot of radiators on the same loop and call it a day?

Radiators have an optimal temperature at which they radiate the maximum heat.

The bigger and more powerful Heat Control’s radiators are optimal at 1000k, which work great for Far Future’s Engines, but they become useless for parts that require to be cool down at lower temperature, like a small nuclear reactor from Near Future Electrical.

So, if you not want your nuclear reactor to be meltdown by a far future’s engine is better to put them in different loops with their own radiators.

For the rest, cooling down engines is just a question of where to put all the radiators needed in the ship without ruins its design (Oh, no, it was a chapter about designing cool ship after all).

 

 

 

Edited Wednesday at 06:20 AM by urturino

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Chapter Three – The Fission Engines

There is 6 of them; Let’s dive in those engines:

 

X-6 "Clarke" Fission Fragment Rocket Engine

If you are playing in Sandbox mode you will probably never use it. But, if you are in Career or Science mode and you have just unlock the node Experimental Nuclear Propulsion, you will be probably tempt by its ISP to try it.

The Clarke is a 10.8 tonnes engines with less Thrust of a Spark Engine, 12 kN.

It has its own build-in fuel tank of Enriched Uranium, an ISP of 350’000 s and produces 15 MW of heat, and it can’t be refuel.

You will never have a good TWR with this engine.

Therefore you will never feel the need of use it again after you will unlock or tried better engines.

But it can easily gives you 100’000 m/s of Delta-v, so if you are willing to perform maneuvers that literally last in-game days it can be a good engine for very small payload.

Using it is pretty easy, you just have to add enough radiators to keep it cool, and it will just work until depletion of the fuel.

There is a very basic design, it weights 18 Tonnes, and with 5 Tonnes of payload it gives to you 124’000 m/s but with a painful 0.05 TWR.

If you want to use this engines, make yourself a favor and install BetterTimeWarpContinued.

 

X-20 "Verne" Pulsed Fission Engine

The Verne is the exact opposite of the Clarke. It’s a 18 Tonnes engine with 640 kN of Thrust and 9’500 s of ISP.

Despite the name and the plume animation, the engine provides a constant thrust, likes all the other “Pulsed” engines of the mod.

It uses Fission Pellet as fuel.

Verne is a Engine Charge, it requires 5000 EC every time it’s turned on.

Like I said in the introduction, rendez-vous with these engines can be very difficult, and my advise is to have strong RCS with a lot of Delta-V.

I use RCS thrusters from Tea Kettle RCS, which are powerful, have an high ISP, and only use Liquid Fuel; But every Kerbonauts is free to find their own solution to this problem, included not using this engine for anything than need to rendez-vous.

Verne produces 13MW of heat, so you’ll need more o less the same amount of radiators of Clarke.

T his basic design with 3 small tanks weight 123 Tonnes, and with 50 Tonnes of payload it gives you 26’600 m/s of Delta-V (plus 680 m/s for RCS with thrusters from Near Future Launch Vehicle) and a very comfortable TWR of 0.38.

That is enough Delta-V to reach Eeloo and come back to Kerbin’s orbit twice (with very little margin for error).

 

X-12 'Hamilton' Nuclear Pulse Engine

Last engine to be add to the mod, Hamilton is a Orion Drive engine, with a weigh of 56 Tonnes, 5’000 kN of Thrust and 2’900 s of ISP.

It doesn’t produces heat, it doesn’t require charge. You just put the right tanks and it will work.

Exactly like Verne, it should be a pulse engine, but it provides thrust at a constant rate.

There isn't much to say, this is very simple to be used, all power, not-so-high efficient engine.

The primary downside of this engine is its weight; Just the engine and the bigger tank are 393 Tonnes. Bring it to orbit can be challenging.

With 100 Tonnes of payload it gives you 21’000 m/s and 0.95 TWR, enough to brings itself to orbit with a small initial push.

 

X-7 "Asimov" Afterburning Fission Fragment Rocket Engine

Asimov is a 18 Tonnes engine, that not require to be charged, with 2 modes:

Mode 1 uses only Fissionable Particles, with 30 kN of Thrust and 450’000 s of ISP, and producing 16 MW of heat.

Mode 2 uses Fissionable Particles and Liquid Hydrogen, with 300 kN of Thrust and 45’000 s of ISP, and producing 13 MW of heat.

Despite the engine is large 3.75 meters, the tanks available are 2.5 meters and some even smaller radial tanks.

This is because the engines consumes very few Fissionable Particles in both modes.

By default those Tanks contain Nuclear Salt Water, it’s required to switch the fuel type on the PAW menu of the tanks.

I’ll be honest, I can’t find a good use for mode 1 of this engine, if not for emergency if the Liquid Hydrogen boils off by mistake.

mode 2 is definitely more interesting.

One small Fissionable Tank and two medium size (5 Meters large) of Hydrogen give you 198’000 m/s with 0.36 of TWR, all of this with 20 tonnes of payload.

And after all the Hydrogen will be depleted, you could still switch to mode 1 and have another 7’500 m/s. (But at 0.06 TWR)

Every Kerbonaut can definitely find a way to have fun with this engines.

 

X-2 "Heinlein" Nuclear Salt Water Rocket Engine

and

X-42 "Niven" Nuclear Salt Water Rocket Engine

The last two engines in Fusion category are the Nuclear Salt Water engines.

Their characteristics are very different, but their functioning is identical, so allow me to affront them together.

Heinlein is the entry level of the Nuclear Salt Water. It weights 12 Tonnes, with 1’800 kN of Thrust and 3’850 s of ISP, and generates 8 MW of heat.

Niven is the Torch Engine of Fusion category. It weights 28 Tonnes, with 3’800 kN of Thrust and 120’000 s of ISP, and generates 50 MW of heat.

The tanks for Nuclear Salt Water are the same of Fissionable Particles, plus others bigger tanks.

Both engines not need to be charged before startup, but they consume EC during the use, like Ion Engines.

Heinlein uses 25.009 EC/s, Niven, instead, uses 90.833 EC/s.

Therefore, feeding those engines of EC is the primary concern for the player.

Well, only for the Heinlein, for the Niven, the primary concern is where to put the radiators for 50 MW of heat.

Nuclear Salt Water tanks are heavy; The bigger tank is 88 Tonnes.

Three of those tanks can give to Heinlein 31’900 m/s and 0.40 of TWR with a small nuclear reactor, 50 tonnes of payload, and a total weight of 463 Tonnes. Good luck bring it to orbit.

But Heinlein is also a pretty decent sustainer engine.

With the longer 2.5 meters tank it has a TWR of 0.98 and 7’900 m/s with 100 tonnes of payload; It just needs a small first stage with enough Delta-V to lift it high enough to deploy the radiators.

With a first stage with 1’500 m/s at sea level, it reached orbit with 5600 m/s, enough for a small trip to Jool.

( Those solar panels are cool, but they will not be very helpful around Jool)

Niven, instead, as Torch Engine, is on another level.

With 6 of those tanks it gives 827’000 m/s and a TWR of 0.37 with 200 tonnes of payload, with a total weight of 1’046 tonnes.

You are probably thinking, “I like those numbers except the last one, how I bring this thing to orbit?”

It’s not my job to tell you how to play, but the probable answer is “In small pieces”.

The engine is 28 Tonnes, a single empty tank is 44 Tonnes. Once assembled in orbit you just have to fill it with the minimum amount of fuel to reach a refuel station.

Another option is to fill it the correct amount to have a TWR capable to put itself in orbit, but it still needs a prior stage to reach a high where it can deploy radiators safety.

Edited Tuesday at 04:10 PM by urturino

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Chapter Four – The Fusion Engines

6 engines, all of them require at least one of those tank:

They can hold Deuterium, Helium3, or both, you can change that in the PAW menu of the tank.

Fuel in those tanks will boil-off if the ship runs out electricity.

One of the engines will require a normal Lithium tank. And 4 of them require or can use a normal Liquid Hydrogen tank.

 

JP-10 "Impulse" Magneto-Inertial Fusion Engine

The Impulse will be the first fusion engine unlocked in Science or Career.

It’s a 11 tonnes engines with 2 modes:

Mode 1 uses only Deuterium, Lithium and 5.559 EC/s, generating 75 kN of Thrust and 3 MW of heat, with 5’000 s of ISP.

Mode 2 uses Duterium+Helium3, Lithium and 41.669 EC/s, generating 100 kN of Thrust and 3 MW of heat, with 7’500 s of ISP.

You can see mode 1 has less power and efficiency than mode 2. Before the last update of the mod, Helium3 was very expensive, so it made sense launching the engine with only Deuterium and reaching a refuel station of Helium3, but now Helium3 is 10 times cheaper, I don’t see a reason to use mode 1, beside maybe the lower EC requirement.

Impulse is a Engine Charge requiring 2000 EC at every ignition or mode switch. What I said for the Verne engine is still valid for this engine, RCS is your friend!

Impulse have less ISP than some Ion Engine from Near Future Propulsion, but it has the advantage to consume a lot less EC of them.

Let’s take this basic design:

Impulse at mode 2, 30 tonnes total (5 payload), 100kN, 7’500s, 26’800 m/s

A craft of similar weight with a Cyclotron VASIMR Engine set a 7500s of ISP will give you a very similar Delta-V, but with a smaller TWR since you will need a 8 tonnes nuclear reactor to feeds it of EC.

And if you tweak the Cyclotron to have a similar TWR of the Impulse you will end up with less Delta-V.

So, despite being the smaller of the bunch, Impulse is still a valid alternative to one of the best engine of Near Future Propulsion. It’s a good engine for small ship.

Impulse is also the first engine we encounter that need to balance fuel.

How to balance it? And most importantly, does it really matter?

Let’s make some test:

In the image of the basic design you saw 1 2.5 meters medium size tank of Lithium and 2 small tanks of D+He3.

If you keep them completely fill you will end up with 26’742 m/s, instead of the 26’801 of the image.

Yes, it’s only 59 m/s, the 0.22%. Let’s try with more fuel.

There is the 7 tanks of Lithium and 14 of D+He3. 70’313 m/s with out rule of thumb of 2 D+He3 for 1 Lithium.

4 of those D+He3 are completely unnecessary.

Here is 7 Lithium, 9 D+H3 (one of which fill for 1/3): 70’879 m/s. 566 m/s of difference.

That is 0.79%.

So, here is what we’ll do: If you want to learn how to balance fuel go to the Appendix One, otherwise, the rule of thumb is good enough the everyday use.

 

JR-15 "Discovery" Spherical Tokamak Fusion Engine

The Discovery is a massive upgrade compared to Impulse. It’s a 20 tonnes engines with 2 modes:

Mode 1 generates 200 kN of Thrust and 15.5 MW of heat, with 17’900 s of ISP.

Mode 2 generates 400 kN of Thrust and 8.5 MW of heat, with 8’000 s of ISP.

Both modes require D+He3 and Liquid Hydrogen.

The engine is a Reactor Charge and requires 10’000 EC to start-up its reactor.

The reactor consumes a small amount of D+He3 when is running.

Balancing fuel with the Discovery is challenging if you intend to use both mode with the same vehicle, because the ratio is different.

Mode 1 uses a ratio of 1:4:200 and mode 2 a ratio of 1:4:400.

Therefore, despite is desirable having a engine that can provides the double of the thrust at request for specific part of the mission, is very hard to create a vehicle that don’t ends up with unbalance fuels.

 

Also, we should ask ourself: Do we want to balance fuels?

If you are choosing to use the build-in fusion reactor of the engine as primarily source of EC, you’ll definitely want to have some extra D+He3 (Remember, Liquid Hydrogen boils-off, you’ll need a lot of EC/s to keep them insulated); But, how much?

If you are not playing with Kerbalism, or some other mod that calculates resources consumption of not-active vehicles, you can ignore the consumption of the reactor completely because fusion reactor uses so little D+He3 that the consumption during the time the craft is active is irrelevant.

(Do you make your timeawarp on Tracking Station as you should, isn’t? Tanks that boils-off and timewarp don’t mix well together.)

 

If you use Kerbalism & Co. keeping the reactor always on can require a lot of D+He3.

In 1 year it consumed 1’569 units of Deuterium and 6’277 of Helium3.

Which mean an big 5 meters D+He3 tank will last ~12.74 years.

For the same weight (8.0 vs 9.5 tonnes) you can have a Hyperion nuclear reactor from Far Future Electrical which will last longer, but it will be harder to refuel.

So, let’s recap, my advise is:

Stock game: Reactor always on, consumption is irreverent.

Kerbalism and Co.: Reactor off when engine is not burning, and if solar power is not an option, Fission reactor is a better source of EC.

But again, everyone is free to playing as they like.

So, let’s close this digression to fuel, and let’s see what this engine can gives us:

 

Discovery is very versatile.

You can get 23’000 m/s with a TWR of 0.34 in mode 2 for a 50 tonnes of payload

(with half D+He3 tank empty)

Or 73’700 m/s with a TWR of 0.22 in mode 1 with 20 tonnes of payload.

You can definitely found a good use of this engine by your own.

 

JR-45 "Fresnel" Mirror Cell Fusion Engine

Fresnel is a engine with 6 variants, between 6 meters and 22 meters, and 2 modes.

Longer variants are heavier and more difficult to bring to orbit, but also more efficient, more powerful, and more hot.

 

I will only talk about the longer variant: 22 meters long, and 50 tonnes of weight.

Mode 1 generates 375 kN of Thrust and 46.5 MW of heat, with a ISP of 200’000 s by using only D+He3

Mode 2 generates 1’875 kN of Thrust and 28.5 MW of heat, with a ISP of 40’000 s by using D+He3 and Liquid Hydrogen

 

The engine is a Reactor Charge and require 12’000 EC to start-up the reactor, with a minimum time to charge of 12 seconds.

Everything a have said for Discovery is also valid for Fresnel, its your decision if keeping the reactor running or shut it down during long journey.

 

Mode 1 can gives you 428’000 m/s and a TWR of 0.24 with 50 tonnes of payload.

Also, D+He3 tanks use a lot less EC than a Hydrogen tanks, so big solar panels can be a option even far from the Sun in this mode.

Mode 2 can gives you 20’700 m/s and a TWR of 0.31 with 500 tonnes of payload.

 

 

JR-20A "Ouroboros" Toroidal Tokamak Fusion Engine

Ouroboros is a 11 tonnes engine with the characteristics of sustainer engine; It uses D+He3 and Liquid Hydrogen and generates 8.5 MW of heat.

It’s a Reactor Charge, and required 3’500 EC to start-up its Fusion Reactor.

 

It has a atmospheric ISP of 1’800 s with 1’421 kN of Thrust. (Its atmospheric TWR is just slightly lower than Rhino’s.)

And a vacuum ISP of 1’900 s with 1’500 kN of Thrust.

Its fuel ratio is 1:4:800, so it uses less D+He3 compared with other engines for the same amount of LH2.

 

So… should we use it as a sustainer engine?

Well, if you are playing in career mode spending 670’000 founds for your upper stage engine is probably a bad idea, but if you refuel it and also use it for the rest of the mission, it can be a valid option for small ship with low Delta-V and high TWR, since it’s the more powerful of the 2.5 meters engines of the mod, and in general, it is beaten only by the Torch Engines, the bigger variants of Fresnel in mode 2 and the Hamilton.

 

Here is two examples of it as sustainer engine.

As first stage with SRBs, completely covered by radiators.

Or as upper stage with a 2000 m/s first stage.

In both cases, 100 tonnes in LKO.

 

As interplanetary engine a more honest comparison is with the engines from Kerbal Atomics (also from Nertea).

Deliverance is more powerful, but it has less ISP.

Emancipator is a lot more efficient and have similar Thrust, but it can’t be refueled once its Enriched Uranium is depleted.

Liberator has the same weight, but is less efficient and powerful.

 

Ouroboros is a valid alternative to all those engines, but it’s more expensive, need radiators and charge, and it’s unlocked too far in the tech tree.

 

K-80 "Hammertong" Inertial Confinement Fusion Engine

Hammertong is a 45 tonnes and 30 meters long engine with two modes both using only D+He3.

It’s a Engine Charge, requiring 20’000 EC (with a minimum time to charge of 20 seconds), therefore, like Verne and Impulse, doesn't have a Fusion Reactor.

Mode 1 has a Thrust of 40 kN, a ISP of 520’000 s, and it generate 31 MW of heat.

Mode 2 has a Thrust of 80 kN, a ISP of 260’000 s, and it generate 26 MW of heat.

 

With a big 5 meters tank of D+He3 and 20 tonnes of payload this engine will give you 438’000 m/s in mode 1, with a TWR of 0.04, and 103’000 m/s in mode 2 with a TWR of 0.08.

If you are brave enough you can add even more fuel.

With a big spherical tank you will have 2’376’000 m/s in mode 1, with a TWR of 0.03.

This is how 4 million m/s look like:

Sincerely I can't find a practical use of this engine, it’s just too weak for everything, but if you really want to build a generation ship, and don’t want/can use a Torch Engine, this is the engine for the job.

 

JX-200 "Cascade" Axial Flow Z-Pinch Fusion Engine

Cascade is the Torch Engine of Fusion category.

It weighs 32 Tonnes, and has 2 modes:

Mode 1 generates 1’100 kN of Thrust and 54 MW of heat by using D+He3, with 360’000 s of ISP.

Mode 2 generates 2’800 kN of Thrust and 36 MW of heat by using D+He3 and Liquid Hydrogen, with 85’000 s of ISP.

Cascade is a Engine Charge, and required 7’500 EC at every activation or mode switch.

 

If you use it in mode 1, the more D+He3 you have the better it is.

One big Spherical tank can gives you 353’000 m/s and a TWR of 0.18 with 500 tonnes of payload.

But the D+He3 required in mode 2 is quite little.

2/3 of a 3.7 meters tank are enough to be match with a big spherical tank of Hydrogen, and you’ll have 87’000 m/s and a TWR of 0.45 with the same 500 tonnes of payload.

If you create a craft with both big spherical tanks you’ll have 77’000 m/s in mode 2, and after all the Hydrogen will be depleted you’ll still have 161’000 m/s in mode 1 (always with 500 tonnes of payload).

There is anything else to say, it’s a Torch Engine, have fun with it!

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Chapter Five – The Antimatter Engines

There are 7 tanks of Antimatter.

 

For the Dirac and Casaba engines you will only need this one:

In the VAB it says 0.1 units, but it’s a rounding, in reality it’s 0.05 units.

For the Torch Engine Frisbee you’ll use the others:

The second thing you need to know is Antimatter cost Science points instead of money (At least in Career and Science mode, in Sandbox everything is free).

 

Nertea himself say we are suppose to pay for the small 0.05 tank and gather Antimatter in other ways for the bigger tanks.

Quote

 

The intended progression is

1) Get antimatter from KSC by spending Science, valid when using the microfusion/microfission engines but not much else
2) Get antimatter from the Kerbin belt, which is free (no Science) but the rates are low
3) Get antimatter from Jool, which should be abundant but is hard to get to
4) Generate antimatter, probably from high solar radiation places.

(https://forum.kerbalspaceprogram.com/topic/199070-112x-far-future-technologies-october-9/page/25/#comment-4422727)

 

The ratio is 1:1, 1 science point for every unit of Antimatter.

The payment is requested on the launch pad:

 

A-7007 "Dirac" Antimatter Initaled Microfusion Engine

The Dirac is the entry level engine of Antimatter category.

It’s a 10 tonnes engine, it generates 45 kN of thrust and 4.4 MW of heat, its ISP is 115’000 s.

It’s a Reactor Charge, requiring 3’500 EC; Its reactor uses D+He3 and Antimatter.

Therefore, now more than ever, is important to not leaving the reactor running when the engine is not burning. My advise is to create a Action Group with both Reactor and Engine toggles.

It’s also important to balance D+He3 and Antimatter on the craft.

Due to the small amount in the tank and the round up, even Kerbal Engineer Redux seems to have problems calculating the delta-v of the craft.

And the game isn't very helpful in communicating engine consumption.

So I chose a empiric method. This is the craft I have used for the testing:

With 10 tonnes of payload, a small spherical D+He3 tank, and 0.05 unit of Antimatter you have 24’000 m/s and a TWR of 0.14. (I probably have more batteries than necessary)

Burning (at x50 timewarp) to depletion of the Antimatter, the consume of the D+He3 was 4’132 units of He3 and 1’033 of Deuterium.

A second test with those exact amount ends up with a small, but yet irreverent, remain.

I imagine small fluctuations due to rounding in calculations are inevitable.

I have tried a third time at 2x timewarp and I got a great result.

In conclusion, the engine is what it is, it’s good to start playing with antimatter without wasting a lot of science, but if you are playing in sandbox you will probably never use it.

 

A-134NG "Casaba" Antimatter Catalyzed Microfission Engine

Casaba is the Fission engine in Antimatter category.

It’s a 32 tonnes engine, it generates 420 kN of thrust and 11 MW of heat, its ISP is 13’500 s.

It’s a Engine Charge, and requires 1’000 EC to startup.

It uses Fission Pellet, Antimatter and build-in Ablator.

Since we can’t use Ablator from other parts, and in the current version of the mod we can’t refuel it, Ablator is fixed bottleneck for this engine.

The amount of Ablator in the engine, a small Fission Pellet tank and the 0.05 units of Antimatter in the smaller tank are perfectly balanced, and can give you 44’600 m/s and a TWR of 0.39 with 50 tonnes of payload.

In the old version it was in theory possible to refuel the Ablator's engine, but this possibility has been eliminated in the latest version.

In the changelog of the mod we read: “Removed ablator refurbish mode from nuclear smelter as it doesn't work and I'll have to rethink it later”

Which mean the engine will be refillable again in future.

 

A-834M "Frisbee" Antimatter Engine

Frisbee is the Torch Engine of Antimatter Category, and it’s the more efficient engine of the mod.

The engine has 16 variants, between 6 meters (32 tonnes) and 110 meters (84.5 tonnes).

Thrust and ISP stay the same, only heat production in reduced in longer version down to 0.

The engine generates 4’000 kN of Thrust and have a ISP of 2’500’000 s.

It uses Antimatter and Liquid Hydrogen in a 1:1 ratio (in game units, not weight).

This monster, obviously too big to enter entirely in the VAB, with just a big 5 meters LH2 tanks (with 300’000 units to match the antimatter tank), a big Antimatter tank, and the 110 meters long variant of the engine with no radiators, has 2’845’000 m/s and a TWR of 1.84 with 100 tonnes of payload.

With 1000 tonnes has 536’000 m/s and 0.36 of TWR.

Kerbal Engineer Redux fails to calculate the burn time because is literally days.

And nothing stops you from adding more fuel.

There isn’t anything else to say, except to remember you those big tanks are very hungry of EC, just not forget Fission or Fusion Reactor, or Batteries and big solar panels. Have fun with it.

[urturino]

Appendix One – Balancing Fuel

 

We saw in the guide the majority of the engines requiring fuel balancing don’t actually have strong penalty if you use just a rule of thumbs to do that.

Anyway, if you don’t want to carry dead weight, here is a small guide to ratio.

Let’s take the Discovery as example:

To calculate the Delta-V of the vehicle with the Rocket Equation we use Kg, Tonnes or Pound, but the game gives us fuel consumption in generic “units”. (Is 1 unit = 1liter? I don’t know and I don’t need to know.

First we calculate the ratio. We can use a online calculators like https://www.omnicalculator.com/math/ratio-of-2-numbers or https://www.omnicalculator.com/math/ratio-of-3-numbers, but do it it’s easy, we take the consumptions in units/s, 0.078, 0.313 and 15.641, we divide “1” by the smaller one.

1 / 0.078 = 12.821

Then we multiplier the other numbers by that:

0.313 * 12.821 = 4.013

15.641 * 12.821 = 200.526

The fuel ratio of mode 1 of Discovery is 1:4:200

Since D+He3 are already balanced in their own tanks 1:4, you just need 200 times more units of LH2 than Deuterium.

The small D+He3 tank has 240 units of Deuterium, so the LH2 needed is 240 * 200 = 48’000

Kerbal Engineer Redux agree with our calculations:

I’m saying it just because every now and then there are some gamers that don’t know: You can set a precise amount of fuel by pressing the “#” button in the top right corner of the PAW menu.

 

You should be able to balance any fuel that is worth balancing.

 

[urturino]

Appendix Two – Burning Like Nobody Is Watching

 

You are saying “Ok, I have more Delta-V than I have ever dream of, but what would I do with it?”

The answer is “You reach your destination faster!”

Friendship ended with Hohmann Transfer. Now Brachistochrone curve is my best friend.

Spoiler

 

Obviously, there is a good video about it from Scott the Man, the Myth, the Legend Manley:

Spoiler

https://www.youtube.com/watch?v=toMnjO8aJDI

 

But, unless you are using a Torch Engines, you’ll not be able to keep the engine running for all the journey.

This is a rapid guide for the half way. For when you have 150-200’000 m/s and you still want to reach your destination faster.

 

First thing, forget everything you know about Launch Windows.

Despite the name, Brachistochrone curve are basically straight lines, you can’t use the same launch windows used for the Hohmann Transfer.

 

The game is not made for this kind of navigation (KSP2 was suppose to be, but, we know, bad things happened and now it’s dead).

For very distant destination your trajectory will stop way before the target planet and you’ll need to eyeballing it, almost always the stock burning time indicator will be useless, and sometimes even Kerbal Engineer Redux’s.

Don’t get frustrated by it, you have a lot of Delta-V, you will reach your destination, and with a bit of experience you’ll avoid all the minor inconveniences.

 

When you travel outbound, ideally, you want to burn prograde until your trajectory is more or less straight line and intersects with the destination’s orbit when the planet is there.

Therefore you want to start the journey when the tangent to Kerbin orbit is more or less align with the destination.

Another option is to set the destination as target and burn when the target’s marker reach prograde’s marker

The faster you’ll go, less the destination planet will had moved by the time you reached.

You’ll still need to add some Radial In/Out component to your maneuver, but again, you have a lot of Delta-V, stop thinking about inefficiency, your goal is not efficiency, is speed!

 

Obviously if you make a single 18’000 m/s maneuver to reach Jool the burning time will be too high.

My advise is to make first the minimum burn required to reach sun’s orbit and then making the big maneuver to the destination.

Since it will need few days to the ship to exit Kerbin’s SOI, try to start the whole process 5 -8 days earlier, so you’ll still be aligned with the destination for the big maneuver.

I was late, and I had to add 4700 m/s of Radial-Out to reach Jool, but still, 4700 m/s out of 150’000 m/s are nothing. Anyway, around Jool in 100 days.

I have made a 22’600 m/s just because I didn't wanted to make bigger burn, but nothing keep you to making it bigger and reaching your destination even faster.

Even your Orbital Insertion Burn will be massive, always program all the burns of your journey before start the maneuvers if you are planning to use all your Delta-V.

 

Insertion are complicated. We leaved Kerbin’s SOI before doing the big burn, we can’t doing the same now, we have to make the big maneuver on Jool periapside, but we’ll arrive at a very high speed.

My advise is to start the burn a lot earlier, not do a 50:50 split, but more a 80:20 (Even 90:10 for Moho or if you have small TWR).

If your Periapside start getting closed to the planet than planned, it means you started the burning to earlier, you can throttle down a bit or shutdown the engine for few minutes.

Congratulation you have reached Jool in 100 days.

But now you are realizing you still have over 100’000 m/s; it would be good to deploy the payload, come back to Kerbin and take another payload.

How do you go inbound?

For some reasons, I found inbound harder (or maybe I have less experience with it).

Again, it’s better to reach Sun’s orbit first, and waiting there the best time to start the journey.

Since orbital velocity is slow, it can require some time.

 

The goal is having a hyperbolic trajectory with the encounter with the destination close to the periapside.

The rest is the same, burn earlier for insertion if you don’t want to miss the planet.

I’m sure someone will find a better way to do all this, and will share it. Good, I’m pretty new at this too, and we need all the knowledge available.

 

Edited Tuesday at 01:05 PM by urturino

[Nertea]

This is cool! Nice note on the consumption rates on the fusion reactors, this should and will be adjusted. 

[urturino]

3 hours ago, Nertea said:

This is cool! Nice note on the consumption rates on the fusion reactors, this should and will be adjusted. 

Thank you. Coming from you it has even more value.