Space industry is tiny compared to other polluting industries, at least today. You'd have to increase it by a factor of 4000 to even meet current levels of air traffic pollution.

I guess the game also takes into account that propellants can be produced climate neutral, although whether this is economical in large quantities is debatable.

Also note that 'climate neutral' does not necessarily mean zero CO2 emmissions. Only that inevitable emmissions are being compensated for.

I recommend this video on YT by Everyday Astronaut who collected some numbers on this particular topic: https://www.youtube.com/watch?v=C4VHfmiwuv4

Originally posted by debott:

Space industry is tiny compared to other polluting industries, at least today. You'd have to increase it by a factor of 4000 to even meet current levels of air traffic pollution.

I guess the game also takes into account that propellants can be produced climate neutral, although whether this is economical in large quantities is debatable.

I recommend this video on YT by Everyday Astronaut who collected some numbers on this particular topic: https://www.youtube.com/watch?v=C4VHfmiwuv4

I am with that comment on the youtube thumbnail. This can't be good right????

It would be awesome if boost were to contribute to climate change in the game. Many of the techs in game could contribute to reduce this effect, like reusable rockets or hybrid air-breathing engines. Nuclear powered launch vehicles might also be an option, or a space elevator.

The most common first-stage is kerolox and the fuel is RP-1 grade kerosene.
(RP1 is essentially jet fuel which has been more carefully refined.)

After that are metholox and hydrolox, which use natural gas and water.

The only nasty rocket fuel in common use is hydrazine / UDMH, which is actually toxic.
(I haven't watched the vid, but hopefully it agrees with me. :-)

Originally posted by cswiger:

The most common first-stage is kerolox and the fuel is RP-1 grade kerosene.
(RP1 is essentially jet fuel which has been more carefully refined.)

After that are metholox and hydrolox, which use natural gas and water.

The only nasty rocket fuel in common use is hydrazine / UDMH, which is actually toxic.
(I haven't watched the vid, but hopefully it agrees with me. :-)

There's also solid fuels that have by far the most devastating effects on our atmosphere.

But there is a bit more to this when it comes to greenhouse gas emmissions. Only a portion of the emmissions is caused by the final combustion (i.e. inside the rocket engine). A great deal is caused by productions methods as well. Even hydrogen is today commonly refined from fossile gas and therefore inherently not carbon neutral.

Originally posted by debott:

But there is a bit more to this when it comes to greenhouse gas emmissions. Only a portion of the emmissions is caused by the final combustion (i.e. inside the rocket engine). A great deal is caused by productions methods as well. Even hydrogen is today commonly refined from fossile gas and therefore inherently not carbon neutral.

However, it's also worth noting that these things do not necessarily need to use fossil fuels, because the carbon-based materials COULD be manufactured from carbon already in the carbon cycle, if a carbon-neutral energy source were used (in which case space launches would technically be carbon-negative, since at least some of what is used will end up in space rather than in the atmosphere, but this would be negligible)

Exactly. Other than already being a rather minuscule portion of current fossil fuel usage, every type of rocket fuel we use can be made synthetically (and carbon-neutrally) from clean energy and carbon dioxide. Granted, it would be a very energy intensive process, but we are talking about a time period in the game where we have civilian fusion power.

Originally posted by cswiger:

The most common first-stage is kerolox and the fuel is RP-1 grade kerosene.
(RP1 is essentially jet fuel which has been more carefully refined.)

After that are metholox and hydrolox, which use natural gas and water.

The only nasty rocket fuel in common use is hydrazine / UDMH, which is actually toxic.
(I haven't watched the vid, but hopefully it agrees with me. :-)

There is/was (at least a few years ago when I did this paper for school) a big push to try and get hydrazine banned. It's a popular monopropellant worldwide that gets good mileage but is also well known for extreme toxicity.
The proposed alternative fuel is hydrogen peroxide, which in highly refined grades would just dissolve all organic matter for a half mile around in the event of an accident or burn off to pure water and oxygen.
Water is the world's leading greenhouse gas, by the way.

Originally posted by Mavrah:

Water is the world's leading greenhouse gas, by the way.

Yes, but in case you haven't noticed, it also leaves the atmosphere readily, and the amount of water the atmosphere can hold is based on temperature, so when it gets hotter due to other things making it hotter, it holds more water, making it even hotter.

Interesting thing is that by 2050 boost should stop exist as a game mechanics. Why? Because by that time you can easily have fusion torchships perfectly capable of taking off from Earth surface using only their main engine. Hell, you don't even need torchships. Even if we assume that using fission drives in atmosphere is not the best idea (which it isn't), even rather early fusion drives are capable of getting to orbit from Earth surface. Namely Triton Reflex with Mirror Cell 3 and Triton Polywell with Hybrid 2.

Originally posted by LorDC:

Interesting thing is that by 2050 boost should stop exist as a game mechanics. Why? Because by that time you can easily have fusion torchships perfectly capable of taking off from Earth surface using only their main engine. Hell, you don't even need torchships. Even if we assume that using fission drives in atmosphere is not the best idea (which it isn't), even rather early fusion drives are capable of getting to orbit from Earth surface. Namely Triton Reflex with Mirror Cell 3 and Triton Polywell with Hybrid 2.

Going through everything in detail takes too long, so quick version: D-T and D-D have massive neutron fluxes, making them unsuitable for usage near Earth. Tritium is also too difficult to get. He3 is also too difficult to get on Earth, because the only way to manufacture it is to make Tritium and wait. So that leaves p-B and p-p.
The Borane Plasmajet Torch x1 requires about 24 kilotonnes of mass just in the reactor and radiators, since you don't have the Exotics in the bulk quantities needed for this to use the Inertial Confinement Reactor V or the Exotic Spike Radiator, and the Droplet-type radiators are unusable in the atmosphere (they really should make it so that the ships with those radiators are unable to land on Titan, and maybe Mars and some of the moons with thin-but-relevant atmospheres), so you're stuck with the ICR IV and the Nanotube Filament Radiator. For comparison, a fully-loaded Saturn V was 3 kilotonnes of mass. The first stage of the Saturn V also had 35.5 MN of thrust, while the baseline of the Borane Torch is 5 MN, so you'd need to increase the thrust, and consequently reduce the EV, by a factor of 56 just to achieve the same acceleration unladen. With the combat acceleration for that torch capping out at 60x, that'd give you about 1 kt of lift capacity for the drive, which also needs to lift its propellant, which at that factor would give less than 12 kps of EV, With LEO having a velocity of around 7.5 kps, and the Earth's velocity at the equator being 0.47 kps, according to the Tsiolkovsky rocket equation (m(i) = m(f)*e^(DV/EV)) you'd need about 19 kt of propellant, which is far beyond the lift capacity of that rocket.
So, tl;dr, that thing couldn't possibly take off from Earth if the devs would implement making the Combat Thrust Multiplier not be free.

Now, the p-p torches also need copious Exotics, so they're out for bulk carriers too (plus the Protium Converter Torch is a WMD pointed out the back)

So, the only one remaining that's actually worth looking at at all is the Zeta Borane Lantern, on account of not killing everyone around it and actually having a reasonable fuel source.
The x1 has a baseline mass of 3.3 kt, so that's about the same as the Saturn V fully loaded. With full combat thrust it has 25 MN, so it's probably not taking off at all before looking at the propellant load. At the full combat thrust factor, it'd have an EV of 51.7 kps, so that'd be 480 t of propellant to reach LEO with just the drive+reactor+radiators.

This isn't accounting for the likelihood of the radiators not functioning at full capacity in the atmosphere due to the much higher temperature than space (although it would have the benefit of direct contact, but I don't know if that would be able to make up the difference, and it wouldn't be able to make it lighter since it'd still need to function with just radiation in space). Also, I'm not 100% sure, but I'm pretty sure that usage of the Tsiolkovsky rocket equation is wrong because it isn't accounting for the acceleration of Earth's gravity fighting against you, which makes it even worse.

So, tl;dr again, the fusion drives that aren't too dangerous or expensive to use wouldn't actually be able to take off from Earth, if the game properly reduced EV when using Combat Acceleration.

Originally posted by LorDC:

Interesting thing is that by 2050 boost should stop exist as a game mechanics. Why? Because by that time you can easily have fusion torchships perfectly capable of taking off from Earth surface using only their main engine. Hell, you don't even need torchships. Even if we assume that using fission drives in atmosphere is not the best idea (which it isn't), even rather early fusion drives are capable of getting to orbit from Earth surface. Namely Triton Reflex with Mirror Cell 3 and Triton Polywell with Hybrid 2.

Meh, the need comes and goes like most resources.
I'm trying to build up the Jovian moons after having bought/pirated every site on Mercury, Mars and in LEO. I need huge amount of boost to maintain all my buildings in the residential, tourist, hospital and administration chains. It's also the most valuable currency to the broken little NPC factions.
I'd be really concerned about lighting up fusion drives in-atmosphere. Think there was a Larry Niven short story about that.
I've also got antimatter nitrous boosters on all of my 4th gen fusion ships. There's no way that stream of radioactive, superheated plasma can good for the stupid turtles.

Methane rockets can be good for the environment if the methane is made from carbon dioxide in the air, plus water, and electricity from fusion power. The rockets are fired outside of the atmosphere for part of the flight, when that happens you're sequestering carbon that was originally in the atmosphere in outer space.

Originally posted by dallasm15:

Methane rockets can be good for the environment if the methane is made from carbon dioxide in the air, plus water, and electricity from fusion power. The rockets are fired outside of the atmosphere for part of the flight, when that happens you're sequestering carbon that was originally in the atmosphere in outer space.

In theory you are correct, but I think this is not really true in practice.

a) Burned methane exhaust is worse than the CO2 it would be created from, because the pollution is more than just CO2: there is also unburned methane and other carbons and the rocket produces condensation trails just like an airplane would. There is no conclusive studies yet on the effect of contrails, but estimates are that they have a greenhouse effect similar in size to the CO2 emmissions alone. Even worse, the pollution from space rockets also causes damage to the upper atmosphere, but I am not sure how bad that effect is.

b) For pretty much all orbits around Earth, the exhaust of rocket engines is being dumped right back into the atmosphere anyways, because the exhaust velocity of the engines is far lower than orbital velocity:
Ve for SpaceX Raptor 2: ~3,700 m/s
orbital velocity in LEO: ~7,800 m/s
Keep in mind that all that exhaust is being dumped backwards from you prograde vector. ;)

Considering that lategame tech has widely available green energy, using hydrogen from water is probably one of the more efficient ways to fuel rockets. Burning hydrogen leaves water vapors as exhaust. Pretty clean all things considered...