The Role of Ground Forces in Interstellar Warfare

[JagerIV]

Why would ground to orbit weapons have such strict range limits? With any sort of kinetic or missile weapon, the orbit to ground range is yes. Missiles could also have reentry vehicles capable of controlled atmospheric flight.

Poor comparison...
"Getting there" is only one of the problem, a missile interceptor needs to get there fast and hit the target.
Here's an actual anti-missile and it's quite a bit bigger:

Ground Based Interceptor – Wikipedia, wolna encyklopedia

pl.wikipedia.org

Well if the defending side has fortified airbases, that's one thing the attacker would be using their megaton orbit to ground weapons against.

Well, because that is the line of sight. As you say, a kinetic or missile can fire non-line of sight, but that does also have issues of speed and range too.

Eh, the ground based interceptor is an example of an anti orbital missile, but it certainly doesn't show a minimum viable size of one. For example, SM-3 and THAAD are also anti orbital missiles, and are much smaller at 1.5 and 0.9 tons each. And all of those are solid fuel as well, likely for the zero warning concerns, and solid fuel rockets are dramatically worse than liquid fuel rockets. Which are perfectly viable in non-zero warning situations, where you have 10-20 minutes to refuel or know your likely to shoot the missile that day.

Because you have such large mass ratios, small improvements in the interceptor also give large returns: the GBI seems to have a 21 ton weight with a 70 kg interceptor, for a mass ratio of 300-1. A more advanced interceptor of 20 kg, in line with a current shoulder fired missiles, get it down to a six ton missile. Mass ratio in line for a Falcon 9 is a 130-1 for payloads to Mars: That suggests a high performance rocket with Falcon 9 tech and a 20 kg payload may be on the order of 2.6 tons, 500 kg with LEO assumptions. And every kg shaved of the interceptor cuts down overall missile mass by 25-300 kg.

I'm doubtful of anti orbit manpads as generally practical outside extremely edge situations, but couple of hundred kg to a couple of tons seems quite doable, especially since they do exist in the form of SM-3s and THAADs, who's rapid prompt intercept needs may be forcing the use of sub optimal tech such as solid propellants.

I know the megaton weaponry is a bit of a meme, but I think in comparing orbital weaponry to non-orbital its useful to measure that out.

Taken most literally, a megaton weapon like a laser or such would be roughly 4 petajoules of energy. Many current electronic systems have power to weights in the 1 MW/ton range. At that power to weight, a 4 petajoule system weighs 4 billion tons. This seems impractical. High performance systems and modern weapons seem to be in the 10 MW/ton range. Now weight is down to 400 million tons. Still a bit troublesome. Very high performance like shuttle turbopumps can get 150 MW/ton, so were talking about 26 million tons. This is at least something that might plausibly fit in a Star Destroyer. Super advanced 1 GW/ton gets the weight down to merely 4 million tons. As a point of comparison in WWII the allies dropped roughly 2.7 million tons of bombs overall.

If you instead transported 4 million tons of material, you could move 20,000 Armored vehicles, 1 million personnel, 100,000 logistical vehicles, and have a million tons of consumables. Dropping the equivalent of the US army may be more effective at achieving military objectives, on a faster timetable, for less cost, and at less collateral damage, than a single doom laser.

And such high power is not necessarily a given for space either: 1 cm/s^2 acceleration at an impulse of 50 km/s, enough for roughly a km/s delta v per day, only requires a vehicle power to weight of 250 kw/ton. At 1 MW/ton engines are only 25% of the ship's mass, and at 10 MW/ton only 2.5%. 100 km/s exhaust velocity and 10 cm/s^2 would be 5 MW/ton. Advanced would require roughly 50% of ship mass be engine/power plant, very advanced a mere 5%.

Now admittedly, a 200,000 ton ship with that 5 MW/ton performance is a ship with a 1 TW engine. High performance engines suggest roughly 10,000 ton engine mass, probably half its weight in fuel, maybe 10,000 tons of tankage. 80,000 tons of other, which maybe 50-60k can be mission mass?

We then can see a little clearer what trade offs may be: 50,000 tons of lasers, maybe 10 MW/ton power to weight for 500 GW laser power, nothing to sneeze at. Or maybe 500 armored vehicles to the surface? A carrier with 100 high performance fighters? Or a missile boat of 5,000 high performance missiles?

When doing combined arms between direct fire, fighters, missiles, and troop ships, I get the sense the balanced force probably does not have zero ground troops. Depending on what the cost/effectiveness is, I lean to them potentially being reasonably substantial.

 

[Marduk]

Well, because that is the line of sight. As you say, a kinetic or missile can fire non-line of sight, but that does also have issues of speed and range too.

Eh, the ground based interceptor is an example of an anti orbital missile, but it certainly doesn't show a minimum viable size of one. For example, SM-3 and THAAD are also anti orbital missiles, and are much smaller at 1.5 and 0.9 tons each. And all of those are solid fuel as well, likely for the zero warning concerns, and solid fuel rockets are dramatically worse than liquid fuel rockets. Which are perfectly viable in non-zero warning situations, where you have 10-20 minutes to refuel or know your likely to shoot the missile that day.

Because you have such large mass ratios, small improvements in the interceptor also give large returns: the GBI seems to have a 21 ton weight with a 70 kg interceptor, for a mass ratio of 300-1. A more advanced interceptor of 20 kg, in line with a current shoulder fired missiles, get it down to a six ton missile. Mass ratio in line for a Falcon 9 is a 130-1 for payloads to Mars: That suggests a high performance rocket with Falcon 9 tech and a 20 kg payload may be on the order of 2.6 tons, 500 kg with LEO assumptions. And every kg shaved of the interceptor cuts down overall missile mass by 25-300 kg.

Mass ratios don't work straight like that because of bstioud materials engineering scaling effects and atmosphere.
This is the reason why we don't have scaled 100 kg F-15 models going with anything near the same speed and range as real F-15, and all the WW2 fighter models also don't move anywhere near as fast, high or far as real WW2 fighters despite better technology. The aerodynamic effects based on mass cross-section vs area alone inherently favor the larger scale, as with scale increase masses and volumes increase to third power while areas only to the second power.

GBI (also solid fueled btw) is a different kind of ABM, meant to cover a larger area and intercept the missiles at higher altitude, which also helps with MIRVS and some other tricks that can be used with missile, while things like SM-3 are more like point defense - all you need to do is compare range and ceiling figures (en wiki may lack those for GBI).

I'm doubtful of anti orbit manpads as generally practical outside extremely edge situations, but couple of hundred kg to a couple of tons seems quite doable, especially since they do exist in the form of SM-3s and THAADs, who's rapid prompt intercept needs may be forcing the use of sub optimal tech such as solid propellants.

I know the megaton weaponry is a bit of a meme, but I think in comparing orbital weaponry to non-orbital its useful to measure that out.

Taken most literally, a megaton weapon like a laser or such would be roughly 4 petajoules of energy. Many current electronic systems have power to weights in the 1 MW/ton range. At that power to weight, a 4 petajoule system weighs 4 billion tons. This seems impractical. High performance systems and modern weapons seem to be in the 10 MW/ton range. Now weight is down to 400 million tons. Still a bit troublesome. Very high performance like shuttle turbopumps can get 150 MW/ton, so were talking about 26 million tons. This is at least something that might plausibly fit in a Star Destroyer. Super advanced 1 GW/ton gets the weight down to merely 4 million tons. As a point of comparison in WWII the allies dropped roughly 2.7 million tons of bombs overall.

Why the self-imposed need to deliver the energy in a single second? Nuclear weapons are extremely inefficient in terms of their yield vs damage done, and the larger they are, the more inefficient, the larger part of the blast going up into the atmosphere or into the ground. A laser that spreads the same energy over a 60 second long lightsaber from the sky, C&C style, would have far more orbital bombardment use than one doing it in a second.
Probably even if it had 1/10 that power it would still be more useful.
And then, if you need impulses, well, all depends on available supercapacitor technology to not be restricted by needing the power generation to match the peak power output of the weapon, as by all chance it would not need to.

If you instead transported 4 million tons of material, you could move 20,000 Armored vehicles, 1 million personnel, 100,000 logistical vehicles, and have a million tons of consumables. Dropping the equivalent of the US army may be more effective at achieving military objectives, on a faster timetable, for less cost, and at less collateral damage, than a single doom laser.

At 4 megatons, we are in 40k capital ship masses.
The point is, if you have a fleet operating at this scale, why not both? Say, that army combined with again that in orbital firepower has definitely greater combat capability than just doubling the army, as the utility of having such superheavy artillery support in the orbit is definitely great, and in particular replaces a lot of the need for other heavy artillery support, which tends to be logistically heavy.

 

[bintananth]

@JagerIV,

When it comes to rocket fuels which are storeable and useable at a moment's notice you don't have many good choices.

Solid: Ammonium nitrate (NH4NO3) or ammonium perchlorate (NH4ClO4) plus powdered aluminium and not much else.

Liquid: Nitric acid (HNO3), some other very strong acid with lots of oxygen, or nitrogen tetroxide (N2O4) burning hydrazine (N2H4) or a methylated derivative of hydrazine. And once again ... not much else.

You ain't getting LOX/LH2 performance out of anything which can be stuck stuck on a shelf in a warehouse which doesn't have heat or A/C.

 

[JagerIV]

Mass ratios don't work straight like that because of bstioud materials engineering scaling effects and atmosphere.
This is the reason why we don't have scaled 100 kg F-15 models going with anything near the same speed and range as real F-15, and all the WW2 fighter models also don't move anywhere near as fast, high or far as real WW2 fighters despite better technology. The aerodynamic effects based on mass cross-section vs area alone inherently favor the larger scale, as with scale increase masses and volumes increase to third power while areas only to the second power.

GBI (also solid fueled btw) is a different kind of ABM, meant to cover a larger area and intercept the missiles at higher altitude, which also helps with MIRVS and some other tricks that can be used with missile, while things like SM-3 are more like point defense - all you need to do is compare range and ceiling figures (en wiki may lack those for GBI).

Why the self-imposed need to deliver the energy in a single second? Nuclear weapons are extremely inefficient in terms of their yield vs damage done, and the larger they are, the more inefficient, the larger part of the blast going up into the atmosphere or into the ground. A laser that spreads the same energy over a 60 second long lightsaber from the sky, C&C style, would have far more orbital bombardment use than one doing it in a second.
Probably even if it had 1/10 that power it would still be more useful.
And then, if you need impulses, well, all depends on available supercapacitor technology to not be restricted by needing the power generation to match the peak power output of the weapon, as by all chance it would not need to.

At 4 megatons, we are in 40k capital ship masses.
The point is, if you have a fleet operating at this scale, why not both? Say, that army combined with again that in orbital firepower has definitely greater combat capability than just doubling the army, as the utility of having such superheavy artillery support in the orbit is definitely great, and in particular replaces a lot of the need for other heavy artillery support, which tends to be logistically heavy.

I don't doubt that the GBI is more capable than smaller missiles. It looks to be orbital, rather than sub orbital, which makes sense for its mission goal. Scaling is also a thing I agree: its one reason air launched missiles can get such high relative performance. The main point of my argument that something parked in low orbit is vulnerable to an immense variety of weapons, many of them quite mobile and easy to hide. Obviously higher up means fewer weapons are a risk, as stated in the original argument. Pushes to the use of more heavy launchers as possible. Probably ideally reusable. Heavy lift bombers as it were.

The main core of the argument is that in a low orbit vs ground fight, ground likely has the advantage. For why going that extra 100 km to land may actually be quite worth it than sticking around in low orbit.

Well, to explore what a megaton weapon actually implies recourse wise. Believing no ground forces are needed seems to me to rely on two incorrect notions: an unbound sense of what space assets can do, and a tendency to treat the space assets as free.

The earlier example of orbital fire support suggests the limits of the platform, where a 20 ton terrestrial fighter may actually have greater combat use than a 20 ton low orbit weapons platform. Or this example here that a super doom laser actually implies a very big ship, which could be used for other things. And that that doom laser is likely to be quite expensive: If your doom laser is 1-10 trillion dollars, well, that buys a lot of military equipment. 200,000 tanks can be in a lot more places at once, and can take far more risks: losing even 50,000 tanks is still cheaper than doom lasers. And the ability to move around doom lasers also implies the ability to move around quite substantial ground forces.

I do agree though the giant doom laser is very impractical as an actual weapons system. But, you did use the term megaton weaponry as an example of the scale of the spaceborne weaponry, so I wanted to double check how much was being discussed there.

And I would agree both, or more like all 4. Remember though that the argument was over whether ground forces have any roll at all. And in order to see if they have a place, trying to quantify what the trade offs in capabilities and costs actually are is useful: we have a bit of an intuitive sense regarding ground forces: why you need some infantry in order for fighter jets to be useful for example (fighter jets can't hold ground, have great difficulty maintaining constant observation). Less of that with space forces, so it seemed a good idea to feel out some sense of what the space trade offs are, to see how much of a role ground forces have in those trade offs.

@JagerIV,

When it comes to rocket fuels which are storeable and useable at a moment's notice you don't have many good choices.

Solid: Ammonium nitrate (NH4NO3) or ammonium perchlorate (NH4ClO4) plus powered aluminium and not much else.

Liquid: Nitric acid (HNO3), some other very strong acid with lots of oxygen, or nitrogen tetroxide (N2O4) burning hydrazine (N2H4) or a methylated derivative of hydrazine. And once again ... not much else.

You ain't getting LOX/LH2 performance out of anything which can be stuck stuck on a shelf in a warehouse which doesn't have heat or A/C.

Definitely true. But, not as relevant in the case of wartime missiles. Because you don't need to store them fueled on a shelf for years. I don't think aircraft stay fueled for particularly long, but that doesn't overly matter because we can just fuel them when needed.

Most of the current anti-ballistic missiles seem designed for peace time hair trigger alert. Nothing is likely to happen in any particular day, but from warning you have minutes to respond. If your super high performance hydrolox missile has a gas station level pump of 30-40 liters per minute and takes 30 minutes to fill up, its useless as an anti ballistic missile weapon.

If however you can see the enemy fleet massing for an attack 1 day out, taking 30 minutes to fill up the missile and a small supply of sustainer fuel so it can stay on the air conditioned truck for a full week, that 30 minute refueling time is irrelevant.

Storability does not seem like it would be as all consuming an issue in space situations that is is for peacetime hair-trigger ballistic missiles.

 

[Marduk]

I don't doubt that the GBI is more capable than smaller missiles. It looks to be orbital, rather than sub orbital, which makes sense for its mission goal. Scaling is also a thing I agree: its one reason air launched missiles can get such high relative performance. The main point of my argument that something parked in low orbit is vulnerable to an immense variety of weapons, many of them quite mobile and easy to hide. Obviously higher up means fewer weapons are a risk, as stated in the original argument. Pushes to the use of more heavy launchers as possible. Probably ideally reusable. Heavy lift bombers as it were.

Why would interplanetary\interstellar invasion ships be so artificially handicapped by being parked, and at the easiest to target low orbit at that? Why would they larp as space stations?

Yes, the push towards heavier and higher performance systems is real... And that in turn means more worthwhile targets for orbital strikes that are harder to hide.
Light, cheap and numerous ground based systems may well be able to decimate a landing force when most vulnerable if they cover the whole planet, and that's a problem for the orbital support to solve.

The main core of the argument is that in a low orbit vs ground fight, ground likely has the advantage. For why going that extra 100 km to land may actually be quite worth it than sticking around in low orbit.

Well, obviously, a large scale ground invasion would start with gradual taking control of the orbit, getting rid of any defense stations and ships, and so on, with increasingly tightening grip of invasion fleet with lowering of orbit, until feasible ones for deployment of bombardment weapons and ground forces are reached.

Well, to explore what a megaton weapon actually implies recourse wise. Believing no ground forces are needed seems to me to rely on two incorrect notions: an unbound sense of what space assets can do, and a tendency to treat the space assets as free.

Why the red herring of no ground forces at all?

The earlier example of orbital fire support suggests the limits of the platform, where a 20 ton terrestrial fighter may actually have greater combat use than a 20 ton low orbit weapons platform. Or this example here that a super doom laser actually implies a very big ship, which could be used for other things. And that that doom laser is likely to be quite expensive: If your doom laser is 1-10 trillion dollars, well, that buys a lot of military equipment. 200,000 tanks can be in a lot more places at once, and can take far more risks: losing even 50,000 tanks is still cheaper than doom lasers. And the ability to move around doom lasers also implies the ability to move around quite substantial ground forces.

The counterpoint is that 200,000 tanks can do jack shit to the orbital doom laser, while they can do a whole lot to 200,000 other guy's tanks that are just landing. It can plink away at them with impunity. The most they can do is waste its time.

I do agree though the giant doom laser is very impractical as an actual weapons system. But, you did use the term megaton weaponry as an example of the scale of the spaceborne weaponry, so I wanted to double check how much was being discussed there.

You are using the most ambitious definition of megaton weaponry possible - a weapon with ability to do a megaton strike *every second*, and in turn needing a power source capable of sustaining that. Obviously there are alternate design options, like capacitor based designs, and that's without even getting into plain ol' kinetics, nukes, and also more exotic options like antimatter storage.

And I would agree both, or more like all 4. Remember though that the argument was over whether ground forces have any roll at all. And in order to see if they have a place, trying to quantify what the trade offs in capabilities and costs actually are is useful: we have a bit of an intuitive sense regarding ground forces: why you need some infantry in order for fighter jets to be useful for example (fighter jets can't hold ground, have great difficulty maintaining constant observation). Less of that with space forces, so it seemed a good idea to feel out some sense of what the space trade offs are, to see how much of a role ground forces have in those trade offs.

The logic with combining ground forces and orbital assets is kinda similar to naval landings. You not only want, but pretty much need to use the heavy orbital weapons to pound the crap out of planetary defenses as landing preparation, and keep doing so as ground forces land, if you want to do a successful opposed landing, as opposed to a mass sacrifice of ground pounders. Ideally you would want them to basically just do a cleanup operation and scout out locations that need a do-over from the orbital weapons after the main bombardment runs out of detected targets, however infrastructure and population preservation objectives (or part of planet being protected from orbital bombardment too well somehow) can shift a lot more workload to them, and\or necessitate of more, lower yield, higher precision orbital support, more resembling conventional artillery and airstrikes.

If however you can see the enemy fleet massing for an attack 1 day out, taking 30 minutes to fill up the missile and a small supply of sustainer fuel so it can stay on the air conditioned truck for a full week, that 30 minute refueling time is irrelevant.

Storability does not seem like it would be as all consuming an issue in space situations that is is for peacetime hair-trigger ballistic missiles.

And then the asshole invader admiral decides to hold for a week or two and the missiles have to be de-fueled or the fuel will corrode through their fuel tanks... There is a reason why as soon as good solid fuels were made available, everyone switched to solid for all military uses outside of... silo based pretty much first strike weapons, peacetime or wartime. Being unpredictable is one of common themes being attempted in any military strategy since forever, no reason to choose defenses that can be circumvented by that.

 

[JagerIV]

@Marduk , Just to quickly address the last point on missiles.

"Oh no, the enlisted had to waste an hour. How sad. Anyways".

Also, we do still use liquid fuel in rockets, notabably Cruise missiles. When the mission needs increased performance, using liquid does not seem like a particularly great burden. If a capital ship wants to waste thousands of tons of fuel to force the planet to waste some fuel, that seems like a battle the planet is quite willing to fight. Probably wasting for fuel in gasoline with the forces dispersing than rocket fuel in the refueling and de-fueling.

By your logic, aircraft are terrible, and forcing fighter scrambles on false alarms is some high impact military strategy, which I just don't see.

And this all assumes a purely reactive, defensive use: if your attacking the enemy with missiles, if high performance fuels means you need to take an extra half hour before the attack to refuel, but makes the attack much more likely to succeed, well making life a tiny bit harder on the enlisted seems well worth it.

Vehicles needing to be fueled does not strike me as any great cost.

 

[Bear Ribs]

Yeah, the thing about a fleet maneuvering around to try to get people to fuel up their rockets and waste it is that the fleet is going to be wasting way, way more. Not only all their fuel from traveling through space and apparently having to spend more fuel coming to a stop and then starting again, but a ship has to internally produce all its air, carry/grow all its food, basically a ton of basic life support that the biosphere of a planet does for free. An idiot admiral deciding to piss away a week or two of his ships being in space doing nothing is going to consume absurdly more resources than planetary defenders needing to stand down from high alert temporarily.

 

[Marduk]

Yeah, the thing about a fleet maneuvering around to try to get people to fuel up their rockets and waste it is that the fleet is going to be wasting way, way more. Not only all their fuel from traveling through space and apparently having to spend more fuel coming to a stop and then starting again, but a ship has to internally produce all its air, carry/grow all its food, basically a ton of basic life support that the biosphere of a planet does for free. An idiot admiral deciding to piss away a week or two of his ships being in space doing nothing is going to consume absurdly more resources than planetary defenders needing to stand down from high alert temporarily.

It's a war, not a market competition, you don't win by being cheaper in the next quarterly cycle. Better lose some supplies than some ships and divisions onboard them. If you can waste some basic supplies to get the enemy's defenses paralyzed in a stand down maintenance cycle to strike then, it's a great deal.

@Marduk , Just to quickly address the last point on missiles.

"Oh no, the enlisted had to waste an hour. How sad. Anyways".

Also, we do still use liquid fuel in rockets, notabably Cruise missiles. When the mission needs increased performance, using liquid does not seem like a particularly great burden. If a capital ship wants to waste thousands of tons of fuel to force the planet to waste some fuel, that seems like a battle the planet is quite willing to fight. Probably wasting for fuel in gasoline with the forces dispersing than rocket fuel in the refueling and de-fueling.

Cruise missiles use liquid fuel, true, but they aren't rockets, they are air-breathing turbojets, so it's not liquid rocket fuel, and as such, they can be left fueled for a very long time, not unlike your car.
Also they aren't defensive, so they don't need to be ready at all times, just when you plan to strike.
When you hear of, say, US submarines or destroyers launching Tomahawks or Harpoons, they aren't fueling the missiles before launch.

By your logic, aircraft are terrible, and forcing fighter scrambles on false alarms is some high impact military strategy, which I just don't see.

It's in fact a perfectly valid strategy, being used against Taiwan right now. And that's for fighters, which do not use stuff as chemically nasty and readiness affecting as liquid fuelled rockets.

Taiwan's armed forces strain in undeclared war of attrition with China

Taiwan President Tsai Ing-wen visited a low-key but critical maintenance base for fighter jet engines on Saturday, offering encouragement as the Chinese-claimed island's armed forces strain in the face of repeated Chinese air force incursions.

www.reuters.com

And this all assumes a purely reactive, defensive use: if your attacking the enemy with missiles, if high performance fuels means you need to take an extra half hour before the attack to refuel, but makes the attack much more likely to succeed, well making life a tiny bit harder on the enlisted seems well worth it.

Yeah, for first strike missiles, it's much less of a hurdle, as i said. But for retaliatory\defensive systems, switching to solids or anything else that provides better readiness is a massive advantage.

Vehicles needing to be fueled does not strike me as any great cost.

It's not any vehicles and any fuels we are talking about. If you had to fuel your car with the stuff used for the kinds of missiles that can only be fueled before launch and can't stay fueled for long, you would have a different perspective.
The fuel is just bloody corrosive. If they spend too much time fueled, you need to send them to full overhaul, which means a good section of your very important missiles will be out of action for a considerable time after just some cycles of such feinting.

 

[JagerIV]

It's not any vehicles and any fuels we are talking about. If you had to fuel your car with the stuff used for the kinds of missiles that can only be fueled before launch and can't stay fueled for long, you would have a different perspective.
The fuel is just bloody corrosive. If they spend too much time fueled, you need to send them to full overhaul, which means a good section of your very important missiles will be out of action for a considerable time after just some cycles of such feinting.

I'm sorry, but what are you talking about? Seriously, what do you think is so corrosive it can be stored in a tank on a truck, but not in a tank on a missile, that is a high performance fuel? None of the common ones I can think have this problem.

Highest performance of course is hydrolox, with methane being a close second. Neither of these are particularly corrosive. They're cryogenic, which makes storing them difficult due to insulation and refrigeration needs, but that's a different concern.

Proton for a non-cyrogenic fuels use N2O4/UDMH, which are used specifically because they're long term stable.

"UDMH is stable and can be kept loaded in rocket fuel systems for long periods, which makes it appealing for use in many liquid rocket engines, despite its cost. In some applications, such as the OMS in the Space Shuttle or maneuvering engines, monomethylhydrazine is used instead due to its slightly higher specific impulse. In some kerosene-fueled rockets, UDMH functions as a starter fuel to start combustion and warm the rocket engine prior to switching to kerosene.

UDMH has higher stability than hydrazine, especially at elevated temperatures, and can be used as its replacement or together in a mixture. UDMH is used in many European, Russian, Indian, and Chinese rocket designs. The Russian SS-11 Sego (aka 8K84) ICBM, SS-19 Stiletto (aka 15A30) ICBM, Proton, Kosmos-3M, R-29RMU2 Layner, R-36M, Rokot (based on 15A30) and the Chinese Long March 2F are the most notable users of UDMH (which is referred to as "heptyl" [codename from Soviet era][citation needed] by Russian engineers[6]). The Titan, GSLV, and Delta rocket families use a mixture of 50% hydrazine and 50% UDMH, called Aerozine 50, in different stages.[7] There is speculation that it is the fuel used in the ballistic missiles that North Korea has developed and tested in 2017.[8]"

Unsymmetrical dimethylhydrazine - Wikipedia

en.wikipedia.org

RP-1, being basically a refined jet fuel, likewise does not have massive unmanageable corrosion problems. Hydrogen Peroxide has some storage dangers, but that's from spontaneous combustion, not corrosion.

I'm honestly not sure what fuel your talking about.

 

[Doomsought]

Highest performance of course is hydrolox, with methane being a close second. Neither of these are particularly corrosive. They're cryogenic, which makes storing them difficult due to insulation and refrigeration needs, but that's a different concern.

The advantages of Hydrolox disappear very quickly when you factor in the difficulty in storing hydrogen.

 

[Marduk]

I'm sorry, but what are you talking about? Seriously, what do you think is so corrosive it can be stored in a tank on a truck, but not in a tank on a missile, that is a high performance fuel? None of the common ones I can think have this problem.

Highest performance of course is hydrolox, with methane being a close second. Neither of these are particularly corrosive. They're cryogenic, which makes storing them difficult due to insulation and refrigeration needs, but that's a different concern.

A container on a truck is much more replaceable and less weight limtied than the main body of a huge missile.
There is also hydrogen embrittlement.

Proton for a non-cyrogenic fuels use N2O4/UDMH, which are used specifically because they're long term stable.

Unsymmetrical dimethylhydrazine - Wikipedia

en.wikipedia.org

RP-1, being basically a refined jet fuel, likewise does not have massive unmanageable corrosion problems. Hydrogen Peroxide has some storage dangers, but that's from spontaneous combustion, not corrosion.

I'm honestly not sure what fuel your talking about.

North Korea: towards a solid-fuel ICBM?

North Korea’s latest military parade re-emphasised the fact that the country has long sought to add a solid-fuel intercontinental ballistic missile to its emergent strategic forces, a goal that may soon be realised.

www.iiss.org

Pyongyang has conducted successful flight tests of three different ICBM types since 2017, although the operational status of these systems is unclear. Each relies on corrosive and toxic mixtures of liquid propellants, meaning the missiles cannot remain fuelled for prolonged periods. Consequently, they are fuelled before launch in a process that can take hours and requires specialist equipment. This process may also provide opponents with a visual indicator of launch preparations and time to identify, react to and neutralise a missile before it is launched. In the case of North Korea's ICBMs – especially the massive Hwasong-17 – many analysts are uncertain that they can be safely erected from a stowed horizontal position when fully fuelled; if they cannot, the missiles would have to remain in the vertical firing position for additional time at the launch site, offering an even clearer warning to observers.

Soviet/Russian Cruise Missiles

Soviet/Russian Cruise Missiles

www.ausairpower.net

The P-15 / SS-N-2 Styx was a far simpler and very different weapon to the larger P-5/P-6 / SS-N-3 Shaddock, and ended up being produced in many different Soviet variants. The Styx was powered by an Isayev P-15 liquid rocket rated at 1.213-0.554 tonnes thrust, using toxic AK-20K/TG-02 propellant based on the Luftwaffe's Wasserfall fuel. This highly toxic and corrosive fuel presents serious handling problems in fuelling up and defuelling the missile, the propellant mix comprising AK-20K/F oxidiser (80% nitric acid, 20% N2O4 with fluorine or iodine additives) and TG02 fuel (50% xylidine and 50% triethylamine).

The same fuel was also used in some ballistic missiles.
Long story short, not sure about the more modern rocket fuels, but the logic seems to be that if a missile can be fueled only before launch and has to be defueled if not launched, there has to be a very good reason for it, and chances are it's probably not some easy and routine operation.

 

[JagerIV]

The advantages of Hydrolox disappear very quickly when you factor in the difficulty in storing hydrogen.

It definitely makes it less superior than its raw exhaust velocity suggests. I recall the surface to orbit missile report only ever used methalox as the cryogenic option, since it doesn't give a huge boost in performance over the non-cryogenic option (UDMH/NTO, same as proton), which double checking the document gives you a 20 ton missile vs a 14 ton missile, but the cryogenic one requires refrigeration, so the total weight is believed to rise to 22 tons with the needed temperature controlled canister.

Still, in the right situations the performance could still be useful, especially on upper stages.

A container on a truck is much more replaceable and less weight limtied than the main body of a huge missile.
There is also hydrogen embrittlement.

North Korea: towards a solid-fuel ICBM?

North Korea’s latest military parade re-emphasised the fact that the country has long sought to add a solid-fuel intercontinental ballistic missile to its emergent strategic forces, a goal that may soon be realised.

www.iiss.org

Soviet/Russian Cruise Missiles

Soviet/Russian Cruise Missiles

www.ausairpower.net

The same fuel was also used in some ballistic missiles.
Long story short, not sure about the more modern rocket fuels, but the logic seems to be that if a missile can be fueled only before launch and has to be defueled if not launched, there has to be a very good reason for it, and chances are it's probably not some easy and routine operation.

The P-15 article further convinces me its not actually all that serious of a problem, because you could store missiles like this at sea, and they could be operated in such a wide variety of conditions why such a wide variation in quality of personnel. This does not convince me this is a particularly crippling issue. I'm sure its annoying and somewhat risky to the enlisted, but you know whats also risky and annoying to the enlisted? Getting shot. If a toxic liquid propellant gets you more performance so the missile has a 20% chance to hit vs a 10% chance to hit, the trade off of enlisted grumbling about doing more work is probably worth the cost of having less of them die.

This just does not seem to be the crippling problem you seem to think it is. If you don't get anything out of higher performance, then solid fuels have many advantages, but if the extra performance is useful, and that performance could be something as simple as having an engine you can start,stop, and throttle, which is hard to do with solid fuel, then liquid fuel is not some crippling disadvantage. The space missiles probably use a lot of liquid fuel too!

And all this assumes some super toxic, corosive fuel: the likely fuels are UDMH/NTO, which is used specifically because its high performance and long term storable, RP-1, which is just highly refined petroleum, and thus cheap, methane, or hydrogen.

The flaw with your predicted strategy here is its immense cost innefficiency, which does matter.

Lets say it was as terrible as you suggest, maybe 10 refueling destroys the missile (rather than some easily replaced fuel tank, which you would think would be an easily replaced bit). Maybe I refill 100 missiles and thus waste $100 million dollars of equipment. However, the ship described runs out of fuel after 6 false attacks, after which it assumedly has to withdraw. So, I spent $60 million to completely negate your $10-100 billion dollar ship. My spending superiority is thus somewhere between 100-1000 to 1. Okay, I have stuff in repair for a week, the enemy ship has to return, do its own refits and repairs for a week, or a month, and come back 3 months from now. By which time all my missiles are repaired.

I think most defenders will take those odds.

 

[Marduk]

It definitely makes it less superior than its raw exhaust velocity suggests. I recall the surface to orbit missile report only ever used methalox as the cryogenic option, since it doesn't give a huge boost in performance over the non-cryogenic option (UDMH/NTO, same as proton), which double checking the document gives you a 20 ton missile vs a 14 ton missile, but the cryogenic one requires refrigeration, so the total weight is believed to rise to 22 tons with the needed temperature controlled canister.

Still, in the right situations the performance could still be useful, especially on upper stages.


The P-15 article further convinces me its not actually all that serious of a problem, because you could store missiles like this at sea, and they could be operated in such a wide variety of conditions why such a wide variation in quality of personnel. This does not convince me this is a particularly crippling issue. I'm sure its annoying and somewhat risky to the enlisted, but you know whats also risky and annoying to the enlisted? Getting shot. If a toxic liquid propellant gets you more performance so the missile has a 20% chance to hit vs a 10% chance to hit, the trade off of enlisted grumbling about doing more work is probably worth the cost of having less of them die.

It's not a crippling issue for strike weapons because it's something used on one's own initiative. But even in their case, everyone who can switches to other options, or at least less nasty liquid fuels, due to the risks, costs and infrastructure requirements of fueling/defueling the missile in platform.
It's less "annoying to the enlisted" and more "adding to maintenance costs and risk of weapon disabling at least, and incredibly explosive at worst accidents".
And if the missile has to be refueled before launch, that time is added to interception delay, which in case of defensive missiles may as well dramatically reduce their effective performance, or make them completely useless (say, if refueling takes 20 minutes, but the expected warning time for the intercept targets is 15 minutes).
It does get worse as an issue in weapons that by their nature have to be used reactively, as in SAMs and ABMs.

This just does not seem to be the crippling problem you seem to think it is. If you don't get anything out of higher performance, then solid fuels have many advantages, but if the extra performance is useful, and that performance could be something as simple as having an engine you can start,stop, and throttle, which is hard to do with solid fuel, then liquid fuel is not some crippling disadvantage. The space missiles probably use a lot of liquid fuel too!

And all this assumes some super toxic, corosive fuel: the likely fuels are UDMH/NTO, which is used specifically because its high performance and long term storable, RP-1, which is just highly refined petroleum, and thus cheap, methane, or hydrogen.

The flaw with your predicted strategy here is its immense cost innefficiency, which does matter.

Lets say it was as terrible as you suggest, maybe 10 refueling destroys the missile (rather than some easily replaced fuel tank, which you would think would be an easily replaced bit). Maybe I refill 100 missiles and thus waste $100 million dollars of equipment. However, the ship described runs out of fuel after 6 false attacks, after which it assumedly has to withdraw. So, I spent $60 million to completely negate your $10-100 billion dollar ship. My spending superiority is thus somewhere between 100-1000 to 1. Okay, I have stuff in repair for a week, the enemy ship has to return, do its own refits and repairs for a week, or a month, and come back 3 months from now. By which time all my missiles are repaired.

I think most defenders will take those odds.

You are running in a wild assumption that fuel costs are a bigger concern in military missiles than the payload and its rarity/cost, while in reality, fuel is an afterthought in light of the cost of stuff like avionics, and more complex engines.
In civilian space rockets:

There are no such detailed stats for military missiles with classified components, however you can compare the prices of guided and unguided rockets of similar sizes to get an idea for how pricey the payload\guidance may be.

If a missile has an "easily replaced fuel tank", well such modularity would incur non-negligible costs to the mass budget and money budget due to more complex engineering, negating some of the gained performance.
That's one of the other reasons why those who can would rather use expensive solid fuels with rather simple engineering and engine, even if they have to make the rocket a bit bigger, than to deal with higher performance liquid fuels - the engineering and maintenance costs may often dramatically exceed the cost of any fuel.

However, for military purposes, that's still nowhere near as bad as sacrificing readiness on defensive missiles - their whole reason for existence is readiness. If it's not kept high and resistant to virtual attrition like feint attacks and false alarms, they are pointless.
If you can get liquid fuels that aren't too finicky to keep the missiles in high readiness for at least months at a time, fine, you can use them competitively with solid fuels, but then you functionally use them the same way as solid ones.

In your example, sure, you may well refurbish the 100 ABM missiles for 100m. However, each of the missiles, particularly the high performance interceptor on it, with its advanced sensors and avionics, represents closer to 50 million investment each at least, and that's without even getting into their support infrastructure like tracking radars. So thanks to the feinted attacks, you have $5bn worth of vital military hardware tied up in a depot being useless rather than ready in launch tubes. Now there is a hole in your defense systems the size of 100 missiles.
If the enemy attacks now, that may save several, if not dozens of 10-100bn ships (or at least a shipload's worth of strike missiles), by virtue of virtual attrition, and you can be sure that the missile maintenance facilities will be among their targets.

Also orbital refueling of spacecraft is something done even with current tech btw, so congratulations if they remembered that logistics matter and brought a tanker to their planetary siege.

 

[JagerIV]

It's not a crippling issue for strike weapons because it's something used on one's own initiative. But even in their case, everyone who can switches to other options, or at least less nasty liquid fuels, due to the risks, costs and infrastructure requirements of fueling/defueling the missile in platform.
It's less "annoying to the enlisted" and more "adding to maintenance costs and risk of weapon disabling at least, and incredibly explosive at worst accidents".
And if the missile has to be refueled before launch, that time is added to interception delay, which in case of defensive missiles may as well dramatically reduce their effective performance, or make them completely useless (say, if refueling takes 20 minutes, but the expected warning time for the intercept targets is 15 minutes).
It does get worse as an issue in weapons that by their nature have to be used reactively, as in SAMs and ABMs.

You are running in a wild assumption that fuel costs are a bigger concern in military missiles than the payload and its rarity/cost, while in reality, fuel is an afterthought in light of the cost of stuff like avionics, and more complex engines.
In civilian space rockets:

There are no such detailed stats for military missiles with classified components, however you can compare the prices of guided and unguided rockets of similar sizes to get an idea for how pricey the payload\guidance may be.

If a missile has an "easily replaced fuel tank", well such modularity would incur non-negligible costs to the mass budget and money budget due to more complex engineering, negating some of the gained performance.
That's one of the other reasons why those who can would rather use expensive solid fuels with rather simple engineering and engine, even if they have to make the rocket a bit bigger, than to deal with higher performance liquid fuels - the engineering and maintenance costs may often dramatically exceed the cost of any fuel.

However, for military purposes, that's still nowhere near as bad as sacrificing readiness on defensive missiles - their whole reason for existence is readiness. If it's not kept high and resistant to virtual attrition like feint attacks and false alarms, they are pointless.
If you can get liquid fuels that aren't too finicky to keep the missiles in high readiness for at least months at a time, fine, you can use them competitively with solid fuels, but then you functionally use them the same way as solid ones.

In your example, sure, you may well refurbish the 100 ABM missiles for 100m. However, each of the missiles, particularly the high performance interceptor on it, with its advanced sensors and avionics, represents closer to 50 million investment each at least, and that's without even getting into their support infrastructure like tracking radars. So thanks to the feinted attacks, you have $5bn worth of vital military hardware tied up in a depot being useless rather than ready in launch tubes. Now there is a hole in your defense systems the size of 100 missiles.
If the enemy attacks now, that may save several, if not dozens of 10-100bn ships (or at least a shipload's worth of strike missiles), by virtue of virtual attrition, and you can be sure that the missile maintenance facilities will be among their targets.

Also orbital refueling of spacecraft is something done even with current tech btw, so congratulations if they remembered that logistics matter and brought a tanker to their planetary siege.

I understand your logic, but I think your premises are very off.

1) Core to your assumption seems to be that missiles of a space capable species will be worse designed than 1950s missiles, since most of the issues your concerned about were solved in the 1960s. And suggest fighters which can take 30-50 minutes to go from zero in in the air are worthless. None of this strikes me as a reasonable assumption. Your corrosion concerns weren't even as big of a deal as you suggest with 1960s ultra cheap USSR missiles built out of sheet metal. That they would be even worse in future anti orbital weapons of a civilization that can clearly fairly trivially reach orbit is absurd.

2) I do not assume fuel costs are a huge issue. I assume terminal defense missiles are cheap. An S-300 missile apparently runs for about $1 million dollars. Aim 120 $1 million. A Tomahawk is roughly $2 million. The stuff you may want to refuel but are sufficiently short range that you need to wait for them to get closer suggests to me a terminal defense missile, otherwise you would generally just fuel and fire.

I think this is partially driven by thinking in terms of ballistic missile defense, while orbital space is much larger, and thing take longer.

Say "safe" are was moon distance, roughly 300,000 km. Closing to LEO is at least 4 km/s, assuming parking orbit in LEO. Thus my roughly 5 km/s cost for launching a fake attack. At those speeds its roughly 3 days from burn to arriving. 3 days warning is a radically different battlefield situation than 20-30 minute warning. If the spacecraft was launching heavy missiles against Earth with 10 km/s delta v to strike in a relative straight line, were still talking about 8 hours from launch to impact. Heavy missiles from much closer, say Geostationary, a mere 30,000 km, were still taking about 50 minutes warning.

And then even closer in in LEO, orbital mechanics impose some lack of immediate responsiveness: when in orbit, getting out of orbit can actually take a bit: lowest energy way is a burn that will have your missiles impact the surface half way around the world (meaning your shooting at something your ship itself can't see) and will impact there in about 50 minutes. More energetic thrust gets your missile down earlier, but then your partially limited by your orbital period of 100 minutes. So if you have an ideal launch window, you come into it roughly every 100 minutes.

Thus, even with fairly fast (chemical) rockets, you need to be fairly far away to get short response windows. However, as you recognized earlier, once your in orbit your about half way to anywhere, so if your missile is not sub orbital, striking further out is not that huge of a leap.

So, reactive missiles are a smaller portion than otherwise. Well, maybe not numerically: I was assuming 100 terminal defense missile out of, say 1,000. Even the minuteman as a 30 ton missile you had about a 1,000 set up. With more advanced tech so they're more in line with a Scud, or even a S-300 missile, a production of 10-50k seems plausible to me. Especially in this kind of orbital denial dispersal to trucks and such, to force something like the scud missile hunt.

So, I was saying even if the problem was as serious as you suggest, which I don't believe it would be, its temporarily disabling a 100 or so $1 million dollar missiles out an inventory of 1-10 thousand of them. The 100 missiles would be the volley against 1, and even there its assuming the defenders are idiots and over fueling.

Virtual attrition is a thing, sure. This however would not likely be a significant source of it. The fuel expenditure of relocating the trucks every day/couple of hours is probably a much greater source of attrition than the fuel in the missiles are likely to cause.

In summary:

1) This all assumes future missiles are worse designed than cheap 1960s missiles.
2) Defenders are idiots
3) Attackers have infinite resources
4) 15 minutes is decive on an attack with hours to days of warning, and which the counter attack takes hours or days to carry out.

Now, all of that, solid has definite advantage. When it gives you all you need, no reason not to use it. If liquid however gives a useful capacity increase, I am utterly unconvinced that the downsides are at all signifigant enough to make using them absurd.

One final point: a liquid ballistic missile like the Chinese DF-5 takes around 30-60 minutes to fuel (this seems however to be a transport issue: when placed in silo it can apparently be left fueled long term). This is already not terrible in the hours to days warning regime. But it also is a huge missile: 180 tons, probably at least 160 tons of fuel. A half hour to fuel suggests the pumps can do about 88 kg of fuel per second. For a much smaller missile, say with 1 ton of liquid fuel, that suggests they can be fueled in 11 seconds. Down to firehose volumes of roughly 20-40 kg a second a one ton rocket can be refueled in 1 minute, a 5 ton rocket in 5-10 minutes.

So, even if the storing fueled was the problem you think (which I don't think they are), and the speed of the refueling was a critical issue (which I'm not sure it is) an easy solution is to just do stronger, faster pumps. Though I also find the idea that it would be rediculous to assume a bit of machinery that needs maintaince done to it couldn't be designed in a way that maintaince could be done, well, absurd. I mean, how do you think it gets built in the first place?

 

[Marduk]

2) I do not assume fuel costs are a huge issue. I assume terminal defense missiles are cheap. An S-300 missile apparently runs for about $1 million dollars. Aim 120 $1 million. A Tomahawk is roughly $2 million. The stuff you may want to refuel but are sufficiently short range that you need to wait for them to get closer suggests to me a terminal defense missile, otherwise you would generally just fuel and fire.

AA missiles are not something you want to use against future orbit to ground missiles. They are spotty enough against existing ones already as more of a secondary/emergency option in not so unlikely scenario of nothing better being available.

RIM-161 Standard Missile 3 - Wikipedia

en.wikipedia.org

Ground-Based Interceptor - Wikipedia

en.wikipedia.org

Serious ABMs go for over an order magnitude higher price.

I think this is partially driven by thinking in terms of ballistic missile defense, while orbital space is much larger, and thing take longer.

Say "safe" are was moon distance, roughly 300,000 km. Closing to LEO is at least 4 km/s, assuming parking orbit in LEO. Thus my roughly 5 km/s cost for launching a fake attack. At those speeds its roughly 3 days from burn to arriving. 3 days warning is a radically different battlefield situation than 20-30 minute warning. If the spacecraft was launching heavy missiles against Earth with 10 km/s delta v to strike in a relative straight line, were still talking about 8 hours from launch to impact. Heavy missiles from much closer, say Geostationary, a mere 30,000 km, were still taking about 50 minutes warning.

If your largest defensive missiles have ranges in mere few thousands of kilometers, why such long "safe" distance? What distance is safe is obviously dictated by the weapons defenders have available. There is also a blanket assumption that the defenders have perfect sensors no maneuvering or stealth weapons can screw with their warning period.

And then even closer in in LEO, orbital mechanics impose some lack of immediate responsiveness: when in orbit, getting out of orbit can actually take a bit: lowest energy way is a burn that will have your missiles impact the surface half way around the world (meaning your shooting at something your ship itself can't see) and will impact there in about 50 minutes. More energetic thrust gets your missile down earlier, but then your partially limited by your orbital period of 100 minutes. So if you have an ideal launch window, you come into it roughly every 100 minutes.

Such basic modeling can miss some obvious advanced weapon choices that screw with it massively.
Say, two stage HGV carrier missiles. Can be fired from very high orbits, and then enter either a low orbit, skim into atmosphere, or slam into it, releasing HGVs that will unpredictably go for targets sometimes a good chunk of the planet away from the impact point, using atmospheric maneuvers to go around apparent dV limitations for choosing the impact point.

Thus, even with fairly fast (chemical) rockets, you need to be fairly far away to get short response windows. However, as you recognized earlier, once your in orbit your about half way to anywhere, so if your missile is not sub orbital, striking further out is not that huge of a leap.

So, reactive missiles are a smaller portion than otherwise. Well, maybe not numerically: I was assuming 100 terminal defense missile out of, say 1,000. Even the minuteman as a 30 ton missile you had about a 1,000 set up. With more advanced tech so they're more in line with a Scud, or even a S-300 missile, a production of 10-50k seems plausible to me. Especially in this kind of orbital denial dispersal to trucks and such, to force something like the scud missile hunt.

So, I was saying even if the problem was as serious as you suggest, which I don't believe it would be, its temporarily disabling a 100 or so $1 million dollar missiles out an inventory of 1-10 thousand of them. The 100 missiles would be the volley against 1, and even there its assuming the defenders are idiots and over fueling.

Virtual attrition is a thing, sure. This however would not likely be a significant source of it. The fuel expenditure of relocating the trucks every day/couple of hours is probably a much greater source of attrition than the fuel in the missiles are likely to cause.

Well, for truck based dispersal the need for missiles to not need depot maintenance often is also non-optional, as doing it implies driving the whole thing outside of the deployment area.

In summary:

1) This all assumes future missiles are worse designed than cheap 1960s missiles.
2) Defenders are idiots
3) Attackers have infinite resources
4) 15 minutes is decive on an attack with hours to days of warning, and which the counter attack takes hours or days to carry out.

What guarantees the warning, and what makes the attackers move around their whole fleet of invasion ships for harassing attacks, instead of smaller vessels or dedicated harassers/bombers with relatively low use of resources?

Now, all of that, solid has definite advantage. When it gives you all you need, no reason not to use it. If liquid however gives a useful capacity increase, I am utterly unconvinced that the downsides are at all signifigant enough to make using them absurd.

One final point: a liquid ballistic missile like the Chinese DF-5 takes around 30-60 minutes to fuel (this seems however to be a transport issue: when placed in silo it can apparently be left fueled long term). This is already not terrible in the hours to days warning regime. But it also is a huge missile: 180 tons, probably at least 160 tons of fuel. A half hour to fuel suggests the pumps can do about 88 kg of fuel per second. For a much smaller missile, say with 1 ton of liquid fuel, that suggests they can be fueled in 11 seconds. Down to firehose volumes of roughly 20-40 kg a second a one ton rocket can be refueled in 1 minute, a 5 ton rocket in 5-10 minutes.

A wild assumption that pump capacity is the bottleneck, which is rather unlikely, use a bloody bigger pump if you need to. The procedures and the size of piping/thermal limits of the missile itself are more of a problem, and those scale with the missile.
15-60 minutes seems to be the norm for ballistic missiles that are fueled in field in general, regardless of size.

So, even if the storing fueled was the problem you think (which I don't think they are), and the speed of the refueling was a critical issue (which I'm not sure it is) an easy solution is to just do stronger, faster pumps. Though I also find the idea that it would be rediculous to assume a bit of machinery that needs maintaince done to it couldn't be designed in a way that maintaince could be done, well, absurd. I mean, how do you think it gets built in the first place?

No one is saying that the maintenance cannot be done, only that it takes time, and it some cases it has to be done in a specialized facility to which the missile has to be transported.
During all of this time, if an attack happens, the missile may as well not exist because it cannot take part in the fight.

 

[JagerIV]

1) Anti Satellite weapons are cutting edge specialized weapons. And thus expensive. If your in a society that has 200,000 ton spaceships moving in planet conquering scale fleets, anti satellite weapons are standard issue common equipment. Given we are already seeing anti orbit weapons like the RIM-161 now, it being standard issue when space access in general is 10-100x cheaper in real terms seems quite reasonable to me.

2) Not largest, smallest. I more or less agree with Davide's Negretti (a work I can't seem to find a PDF link online for) theory of three categories of anti Orbit missiles:

A) Terminal Defense: Sub orbital missiles, and thus fairly range and altitude limited. He believed 6 km/s was sufficient for about a 500 km radius bubble of targeting against maneuvering targets, a bit further out for non-maneuvering targets like communication or reconnaissance satellites. He believes you can do this in very small missiles with plausible advancements in electronics, I'm suspicious of getting it as good as he thinks, and see these still likely being at least hundred of kg to couple of ton weapons. His preference here is

"Kerosene and HTP70. The propellant is storable, of low toxicity and with extremely low launch signature, making it a good choice for battlefield deployment." P. 84, Negretti

This is what I refer to when I'm talking about terminal weapons: weapons designed to defend or engage targets within a local area.


B) Orbital Denial: Weapons more or less just capable of orbit, which basically just means higher LEO as practical targets (2,000 km up) and against maneuvering targets he seems to believe the horizontal effective range is about 2,000 km as well. Further off from that takes fairly slow orbital shifts, making it questionably useful against any maneuverable craft. He assumes these can be made 5-2 tons depending on fuel (5 tons being the solid fuel option, 2 ton being a UDMH/IRFNA missile: he is generally quite fond of UDMH/IRFNA)

UDMH/IRFNA
Used in the Cold War era MGM-52 Lance tactical ballistic missile, a storable
hypergolic propellant combination that can be handled in the field with no
issue, employing Unsymmetrical Dimethylhydrazine as fuel and Inhibited Red
Fuming Nitric Acid - Nitric Acid with a very slight amount of Hydrofluoric
Acid added to protect the tanks from corrosion - as oxidizer. Over 295 s
of specific impulse can be achieved at sea level, while 345 s can be achieved
in vacuum. The plume is relatively discreet, but engine transients during
start-up may give rise to a characteristic billowing orange cloud.

This is based on his assumptions that a 50 kg payload with modern tech can be quite devastating, and modern construction techniques can be applied. I tend to be a bit more conservative in my estimates, especially on issues such as cost: he assumes 3 stage rockets to reach these performances, while I believe since engines tend to be the dominate design consideration a larger rocket but that's only two stage is probably worthwhile.

c) Long Range area denial. More than mere orbital, Negratti puts the lower cut off at roughly 15 km/s. These can strike more or less anywhere in the system, and thus need the batteries and power to be operational for that long. These are about 100 tons to 20 tons assuming a 200 kg payload. Its for these long range strikes where the low performance of solid can be really crippling, and you really need liquid fuels to get enough performance to consistently do anything.

d) I would also add on top of all that heavy lift bombers: modern equivalent would be something like starship, using a reusable high performance heavy lifter to deploy missiles into orbit directly. Probably the best option for non-low orbit chemical rocket delivery. Obviously one of the prime enemy targets.

3) I am unfamiliar with the HGV abbreviation. As described it sounds like a standard attack.

4) Sure, and your evidence has further convinced me it won't be necessary: if something shoddily built as 60s USSR missiles can be deployed to a tiny boat and be fine, whatever missile is used will also be fine. It might need depot maintenance eventually, but so does the truck. The electronics will eventually have batteries go bad, gears may need re-greased. Truck is probably going to give you crippling problems first.

5) Sure. But then your not mobilizing your entire missile strike force to shoot down a single bomber are you? Fighters and such are good for such attacks and inflicting attrition, as much because risking a fighter doesn't risk nearly as much of the fleet as most ships.

6) This is a hard thing to prove, but even then you fall back on the issue of "are airplanes and cars worthless because they take time to fuel and need maintaince?"

7) Yes, missiles take maintenance. So do cars. So to the spacecraft and fighters being used against, or the friendly ones the missiles are assumedly being used in support of. I have trouble picturing a situation where those spacecraft and fighters take less maintenance than the missiles will. Your condemning missiles for being like every other bit of military equipment. Being less needly than many of those other bits of equipment.

A planet on the defense is also generally going to be in a much better place to provide that maintenance than an expeditionary invasion fleet. A planetary militia based on historical norms is likely going to be relatively people rich and supplies poor: something like a P-15 termit may be preferable than a less maintaince intensive system (though nothing I've read on the missile even really suggest it was unusually maintaince intensive) because the planet has more enlisted to throw around than capital.

Solid has its place, especially in terminal close in surprise encounters. However,

1) This means very close encounters.
2) Many modern fuels don't really have much readiness problems anyways, and those that do no worse than scrambling fighters, which would likely be a key part of any defense.
3) Based on my review of solid performance, they simple don't have the performance needed to engage targets outside of low earth orbit anyways, about 2,000 ish km up or out from the silo. I no longer believe solid rockets have the meaningful capacity for further than that relatively close range engagements of a couple thousand km. Anything further out chemically powered needs to use liquid fuels for the range. Any space based system likely needs to use liquid propellants generally for the weight saving.
4) But, outside that point defense 500-3,000 km range, your dealing with travel times that the downsides of liquid, which I'm increasingly believe are actually very minor in the scheme of interplanetary war, are even less relevant.

 

[Vyor]

Reminder that the biggest issue of taking out missiles is that you don't know where they're coming from or where they're going.

Neither of these is an issue if you're shooting at orbiting spaceships.

 

[Marduk]

1) Anti Satellite weapons are cutting edge specialized weapons. And thus expensive. If your in a society that has 200,000 ton spaceships moving in planet conquering scale fleets, anti satellite weapons are standard issue common equipment. Given we are already seeing anti orbit weapons like the RIM-161 now, it being standard issue when space access in general is 10-100x cheaper in real terms seems quite reasonable to me.

2) Not largest, smallest. I more or less agree with Davide's Negretti (a work I can't seem to find a PDF link online for) theory of three categories of anti Orbit missiles:

A) Terminal Defense: Sub orbital missiles, and thus fairly range and altitude limited. He believed 6 km/s was sufficient for about a 500 km radius bubble of targeting against maneuvering targets, a bit further out for non-maneuvering targets like communication or reconnaissance satellites. He believes you can do this in very small missiles with plausible advancements in electronics, I'm suspicious of getting it as good as he thinks, and see these still likely being at least hundred of kg to couple of ton weapons. His preference here is



This is what I refer to when I'm talking about terminal weapons: weapons designed to defend or engage targets within a local area.


B) Orbital Denial: Weapons more or less just capable of orbit, which basically just means higher LEO as practical targets (2,000 km up) and against maneuvering targets he seems to believe the horizontal effective range is about 2,000 km as well. Further off from that takes fairly slow orbital shifts, making it questionably useful against any maneuverable craft. He assumes these can be made 5-2 tons depending on fuel (5 tons being the solid fuel option, 2 ton being a UDMH/IRFNA missile: he is generally quite fond of UDMH/IRFNA)



This is based on his assumptions that a 50 kg payload with modern tech can be quite devastating, and modern construction techniques can be applied. I tend to be a bit more conservative in my estimates, especially on issues such as cost: he assumes 3 stage rockets to reach these performances, while I believe since engines tend to be the dominate design consideration a larger rocket but that's only two stage is probably worthwhile.

c) Long Range area denial. More than mere orbital, Negratti puts the lower cut off at roughly 15 km/s. These can strike more or less anywhere in the system, and thus need the batteries and power to be operational for that long. These are about 100 tons to 20 tons assuming a 200 kg payload. Its for these long range strikes where the low performance of solid can be really crippling, and you really need liquid fuels to get enough performance to consistently do anything.

Those are very small payloads. With expensive miniaturization of electronics and nuclear warheads, it can work, but it leaves precious little room for things like penetration aids, alternate sensors, and multirole capabilities.

Also, a lot of predictions about costs, for top of the line guidance/countermeasure discrimination, you still will probably need top of the line electronics, because that's what the enemy will be using for their defenses, and that screams expensive.

d) I would also add on top of all that heavy lift bombers: modern equivalent would be something like starship, using a reusable high performance heavy lifter to deploy missiles into orbit directly. Probably the best option for non-low orbit chemical rocket delivery. Obviously one of the prime enemy targets.

For bombers to make sense at all as more than another missile stage, more exotic options like nuclear are more likely.

3) I am unfamiliar with the HGV abbreviation. As described it sounds like a standard attack.

Hypersonic glide vehicle. Fast like a ballistic missile, but with full, cruise missile like maneuvering ability.

4) Sure, and your evidence has further convinced me it won't be necessary: if something shoddily built as 60s USSR missiles can be deployed to a tiny boat and be fine, whatever missile is used will also be fine. It might need depot maintenance eventually, but so does the truck. The electronics will eventually have batteries go bad, gears may need re-greased. Truck is probably going to give you crippling problems first.

That is completely backwards in light of what we in fact do know about maintenance needs and complexity of various equipment. More complex and high performance devices generally need more and more maintenance. Fighter jets require orders of magnitude the maintenance trucks do, and the intervals are orders of magnitude shorter.
Ballistic missiles merely kept in readiness also last for months or few years at most without any more intense exercises.
If literal rocket technology gets so perfected to a point where it's not a maintenance hog, their trucks will be resembling something from BT or 40k.

5) Sure. But then your not mobilizing your entire missile strike force to shoot down a single bomber are you? Fighters and such are good for such attacks and inflicting attrition, as much because risking a fighter doesn't risk nearly as much of the fleet as most ships.

How do you know how many and what kind of missiles a bomber carries?
How do you know it's even possible to intercept, as it may be merely putting missiles on an odd orbit while staying far away from the planet?
There is a lot that can be done in terms of harassing tactics in that vein.

6) This is a hard thing to prove, but even then you fall back on the issue of "are airplanes and cars worthless because they take time to fuel and need maintaince?"

In some scenarios, yes. We are talking readiness, it's not a binary question, it's a matter of proportion of time it takes to take something out of the line, and what time it takes to put it in readiness again. Your average car is absolutely great in that regard - it's ready to do its job most of the time, and once every few months or years it may need a few days in a workshop.
But the expensive military toys aren't like that.
For example, in the B-2 fleet on average for each operational bomber 1 or 2 are undergoing maintenance at the same time, readiness given being around 40%.
If your car had to spend 60% of time being worked on by a mechanic, you would have a bit different outlook on that.

7) Yes, missiles take maintenance. So do cars. So to the spacecraft and fighters being used against, or the friendly ones the missiles are assumedly being used in sort of. I have trouble picturing a situation where those spacecraft and fighters take less maintenance than the missiles will. Your condemning missiles for being like every other bit of military equipment. Being less needly than many of those other bits of equipment.

Again, we are talking about readiness. The question is not if something needs maintenance, the question is how much and how often.

Here's a mystery for you... Why can a destroyer operate without going somewhere for maintenance for far longer than a fighter jet can?

A planet on the defense is also generally going to be in a much better place to provide that maintenance than an expeditionary invasion fleet. A planetary militia based on historical norms is likely going to be relatively people rich and supplies poor: something like a P-15 termit may be preferable than a less maintaince intensive system (though nothing I've read on the missile even really suggest it was unusually maintaince intensive) because the planet has more enlisted to throw around than capital.

Again, basic logistics and common sense defeating theoretical math. If it takes 5 minutes for a dude to change a car battery, that doesn't mean 50 dudes can do it in 6 seconds. Attempting that would probably cause a lot of confusion, wasted labor and little improvement in the timing. Equipment, transport and procedures needed tend to be the main limits in such cases.

Solid has its place, especially in terminal close in surprise encounters. However,

1) This means very close encounters.
2) Many modern fuels don't really have much readiness problems anyways, and those that do no worse than scrambling fighters, which would likely be a key part of any defense.
3) Based on my review of solid performance, they simple don't have the performance needed to engage targets outside of low earth orbit anyways, about 2,000 ish km up or out from the silo. I no longer believe solid rockets have the meaningful capacity for further than that relatively close range engagements of a couple thousand km. Anything further out chemically powered needs to use liquid fuels for the range. Any space based system likely needs to use liquid propellants generally for the weight saving.
4) But, outside that point defense 500-3,000 km range, your dealing with travel times that the downsides of liquid, which I'm increasingly believe are actually very minor in the scheme of interplanetary war, are even less relevant.

There is little point for defensive missiles to aim for interceptions further away than this, if possible at all on account of reaction times, detection tracking etc, it would have additional requirements for no extra benefit even if doable. If you are intercepting something coming at you, well, it has to become a very close encounter at some point if it ever wants to hit in the first place.

Secondly, new solid fuel technologies are constantly worked on, and due to the sheer complexity of the subject involving things like manufacturing technologies and grain shapes, a lot of stuff can happen there, involving, say, the potentially higher densities of solid fuel.

 

[JagerIV]

Would be curious on how practical/impractical utilizing an EMP weapon might be as part of the lead up to invasion. The military would be hard-wired against it but I don't know how practical that would be to do for the civilian sector.

Best case scenario you'd plunge a large swath of the planet's population into a virtual dark age causing chaos and rioting from lack of services to transportation of food and other goods being disrupted. Further hinder and tie up the planet's resources as they try to deal with that and my invading army.

Hm, I think history suggests this is not actually the case: people say things are 3 days from anarchy, but that's actually not the case: USSR, China, and India have had massive famines which didn't seriously threaten the state, or even particularly its operation overmuch.

In the case of an EMP, as you suggest it may cause a great deal of disruption to the civilian economy, but not to the military. Which if anything is likely to make the civilians more obedient to the military: if your in a town, and the only source of communication and organization is the military, most people are likely to just fall in line with what the military is saying: after all, they're the only one who have comms and functioning supply: being in the good grace of the military is the optimal way to feed yourself if there is a food shortage. If your in the great leap forward, the path to surviving is probably to signal that your more loyal than everyone else to the Red Army, not to rebel.

The times when starving people actually charge machine guns seems historically rare, and it makes sense in a game theory logic: if the soldiers will shoot you, then you risk a high chance of death. But, if you have the strength to attack machine gun nets, there's likely 10-20 other strategies you could pursue that have some chance of success, and certainly have less chance of immediate death.

And all of this is in situations of people who are not living particularly high above subsistence! Richer areas, well, have more wealth. As overweight Americans, we have extensive fat stores so simple caloric starvation takes a while. We have some beans and rice. In case of cold we have gas, which I don't think has any part that's dependent on electronics, but even if that goes we have a lot of trees around because we previously had gas, and thus almost no one has needed to chop down trees for fuel. Many have wood grills, basically just for fun that can now be used to cook.

Food in general to not starve is not a huge amount of material: rationed food can be about 1 kg a day, so 300 million people on rations is roughly 300,000 tons of food per day. The American Airforce C-17 fleet of 230 has a combined payload of 18,000 tons, the 370 c-130s collectively can carry about 7,000 tons, and the 50 C-5 Galaxy's can carry another 6,000, for a total of about 30,000 tons of airlift capacity. So, short hops of 2 hours with 10 trips a day, you can just barely move enough food to keep everyone from starving with Airforce strategic airlift alone.

Obviously you wouldn't need to do so: other civilian infrastructure could be brought to operation, and if you needed to just use military transport capacity, you'd probably lean on the 100k+ trucks the army has, with something like 1 million tons transport capacity.

Or, for a look at the civilian side: The US ships roughly 12.5 billion tons of good. If even rounding up you need 1 million tons of goods shipped per day so people don't starve, so about 365 million per year, you need to destroy 97% of civilian shipping capacity, long term. If you only destroyed 90% of it, that leaves 1.2 billion tons of shipping left, which you only need, lets round up again to 400 million tons so people don't starve, leaving 800 million tons of capacity to sustain military operations and carry out rebuilding back up to the billions of tons of transport natively available.

There is just so much surplus available that unless you are destroying 80-99% of everything, your still likely leaving a surplus which can be re-invested into fairly quickly rebuilding and getting everything back online.

 

[Vyor]

Those are very small payloads. With expensive miniaturization of electronics and nuclear warheads, it can work, but it leaves precious little room for things like penetration aids, alternate sensors, and multirole capabilities.

Also, a lot of predictions about costs, for top of the line guidance/countermeasure discrimination, you still will probably need top of the line electronics, because that's what the enemy will be using for their defenses, and that screams expensive.

For bombers to make sense at all as more than another missile stage, more exotic options like nuclear are more likely.

Hypersonic glide vehicle. Fast like a ballistic missile, but with full, cruise missile like maneuvering ability.

That is completely backwards in light of what we in fact do know about maintenance needs and complexity of various equipment. More complex and high performance devices generally need more and more maintenance. Fighter jets require orders of magnitude the maintenance trucks do, and the intervals are orders of magnitude shorter.
Ballistic missiles merely kept in readiness also last for months or few years at most without any more intense exercises.
If literal rocket technology gets so perfected to a point where it's not a maintenance hog, their trucks will be resembling something from BT or 40k.

How do you know how many and what kind of missiles a bomber carries?
How do you know it's even possible to intercept, as it may be merely putting missiles on an odd orbit while staying far away from the planet?
There is a lot that can be done in terms of harassing tactics in that vein.

In some scenarios, yes. We are talking readiness, it's not a binary question, it's a matter of proportion of time it takes to take something out of the line, and what time it takes to put it in readiness again. Your average car is absolutely great in that regard - it's ready to do its job most of the time, and once every few months or years it may need a few days in a workshop.
But the expensive military toys aren't like that.
For example, in the B-2 fleet on average for each operational bomber 1 or 2 are undergoing maintenance at the same time, readiness given being around 40%.
If your car had to spend 60% of time being worked on by a mechanic, you would have a bit different outlook on that.

Again, we are talking about readiness. The question is not if something needs maintenance, the question is how much and how often.

Here's a mystery for you... Why can a destroyer operate without going somewhere for maintenance for far longer than a fighter jet can?

Again, basic logistics and common sense defeating theoretical math. If it takes 5 minutes for a dude to change a car battery, that doesn't mean 50 dudes can do it in 6 seconds. Attempting that would probably cause a lot of confusion, wasted labor and little improvement in the timing. Equipment, transport and procedures needed tend to be the main limits in such cases.

There is little point for defensive missiles to aim for interceptions further away than this, if possible at all on account of reaction times, detection tracking etc, it would have additional requirements for no extra benefit even if doable. If you are intercepting something coming at you, well, it has to become a very close encounter at some point if it ever wants to hit in the first place.

Secondly, new solid fuel technologies are constantly worked on, and due to the sheer complexity of the subject involving things like manufacturing technologies and grain shapes, a lot of stuff can happen there, involving, say, the potentially higher densities of solid fuel.

Why the fuck are you acting like they'd bother invading current earth like this when there are cheaper and faster ways to take over a planet of our tech level?