Thoughts on planetary combat

[Ted C]

It would actually be amusing to subvert a few sci-fi cliches and create a sci-fi universe where most of the time and energy and danger of interstellar transit is in the sublight portions of the trip.

Then I would suggest the Vatta's War series, by Elizabeth Moon. Ships moving FTL are essentially invulnerable, but they have to stop at "jump points" periodically and move through space at sublight speed to reach another jump point to start the next leg of an interstellar journey (no real explanation why, that's just how it works, apparently).

Ships are vulnerable attack while "boosting" out of a system to reach a jump point, while flying to the destination planet after emerging from FTL, and during the trip from one jump point to another where a transition is necessary.

Pretty good series, overall. Doesn't dwell much on how the technology works, but very consistent about what it does.

[Shroom Man 777]

It's not personal safety which has driven longer ranged artillery lately, but the need to cover more area than before with a single firing battery as artillery forces shrink from their cold war highs.

You could put ablative coatings onto an artillery shell to at least increase the dwell time of a laser on it; but the problem would be that accuracy would be gone as that ablative coating is burned off unevenly.

Don't the Europeans have an artillery system wherein multiple guns fire simultaneously in quick succession precisely at a single target? If all guns fire first rounds that have ablative coating, but the succeeding rounds aren't coated, while the lasers take more time in destroying the first coated shells (that become less accurate when their coating is destroyed), it would buy time for the rest of the rounds to hit?

[Junghalli]

...pop quiz: Calculate the mass and area required for a solid object to vent the heat put off by the Sun.

Then read what you said and you might be able to answer question two: Why am I chuckling right now?

Wouldn't a Dyson Sphere collecting the entire sun's output have the same problem?

It makes me kind of wonder if major exports of planets would be:

1.) liquid oxygen for life support systems in spacecraft.

You could get water (which can be cracked into hydrogen and oxygen by electrolyses) from near-Earth asteroids at a much lower delta V cost.

[ThomasP]

Of course everybody is going to nuke me from orbit for the heinous crime of being "no fun," but it seems to me the most cost effective way of conquering a planet is by inserting a few Manchurian Candidate agents and have one win the next election for planetary president.

One of Charles Stross's books, Iron Sunrise I think, had a polity that used this very premise. In fact he even made note of the fact that this civilization had developed (paraphrasing) "the only viable means of planetary conquest".

That's in a fairly high-tech setting as well.

[Patrick Degan]

In Doctor Who, the Daleks solved this problem by bombarding Earth with plague missiles disguised as a shower of meteroids and contented themselves to wait a few years. The plague killed off the balance of the planetary population, leaving too few survivors to keep up an organised global society or put up any sort of resistance. When the surface degenerated to utter anarchy, the Daleks moved in without having to fire a shot.

[Samuel]

In Doctor Who, the Daleks solved this problem by bombarding Earth with plague missiles disguised as a shower of meteroids and contented themselves to wait a few years. The plague killed off the balance of the planetary population, leaving too few survivors to keep up an organised global society or put up any sort of resistance. When the surface degenerated to utter anarchy, the Daleks moved in without having to fire a shot.

How high tech was Earth? If the whole system was colonized rogue asteroids would be noticed. Of course you could accomplish the same thing by slipping in a disease in a freightor or other space ship.

[Junghalli]

How high tech was Earth? If the whole system was colonized rogue asteroids would be noticed. Of course you could accomplish the same thing by slipping in a disease in a freightor or other space ship.

The challenge then would be making a disease that an advanced starfaring civilization couldn't deal with. In a realistic universe I suspect people advanced enough to be doing interstellar colonization could probably just upload to a new body if nothing else works.

[Ariphaos]

Wouldn't a Dyson Sphere collecting the entire sun's output have the same problem?

It's twenty to forty times the radius of the Sun, and only harnessing the Sun's energy. You want to add orders of magnitude to that, on a space ship.

[Patrick Degan]

In Doctor Who, the Daleks solved this problem by bombarding Earth with plague missiles disguised as a shower of meteroids and contented themselves to wait a few years. The plague killed off the balance of the planetary population, leaving too few survivors to keep up an organised global society or put up any sort of resistance. When the surface degenerated to utter anarchy, the Daleks moved in without having to fire a shot.

How high tech was Earth? If the whole system was colonized rogue asteroids would be noticed. Of course you could accomplish the same thing by slipping in a disease in a freightor or other space ship.

Earth, by the 2150s, had gotten up to the level of planetary weather-control, moonbases, and transmat technology. They had a functional world government ("The Moonbase", "Enemy Of The World", "The Seeds Of Death"). There was enough of an infrastructure in place to have made a conventional invasion (these were pre-Time War Daleks, BTW) a very bloody affair for the mutants from Skaro.

[Sea Skimmer]

Don't the Europeans have an artillery system wherein multiple guns fire simultaneously in quick succession precisely at a single target? If all guns fire first rounds that have ablative coating, but the succeeding rounds aren't coated, while the lasers take more time in destroying the first coated shells (that become less accurate when their coating is destroyed), it would buy time for the rest of the rounds to hit?

Firing multiple guns to achieve a simultaneous impact is called a time on target and was invented by the US Army in WW2. Today any digital fire control computer (you can attach these to towed guns as well as fancy self propelled ones) can easily allow gun crews to shoot a time on target mission. Back in WW2 we had to do it all by hand, and yet in one case it took only 1 hour to do the math to allow all the artillery of an entire US Army to shoot a TOT at a single Italian town held by the Germans.

So anyway what you may be thinking of is multiple round simultaneous impact. With this tactic a howitzer with a variable propellant charge can shoot several shells at different angles and different velocities. The longer trajectories are given to the first shells fired ect... resulting in anything from four to eight shells from one howitzer impacting in the space of less then 10 seconds. Pz2000 and a few other systems can do this; the exact number of rounds that can be fired with this tactic depends on the range to target and the performance of the howitzer.

This is however not a great counter to a laser anti artillery system. The reason being that while the shells impact at almost the same time, they are still not fired at the same time and the first ones fired will be lofted excessively high, increasing time of flight and thus enemy engagement time. That is not good.

The ideal counter (besides using multiple rocket launchers for epic levels of ammo spam,) is to use a high velocity lower angle shooting gun instead of a howitzer to reduce time of flight to the utter minimal. The short lines of sight also reduce the number of enemy laser units which will be able to fire at all. Firing at low angle has the inherent disadvantage when firing conventional ammunition the shells will also arrive at a low angle and thus cannot search behind obstructs like hills or plow deeply into the ground to destroy entrenchments. Thus the whole reason for howitzers in the first place.

However using advanced guided shells, which are likely to be standard within the next 20 years, let alone the next several hundred, this limitation no longer applies. A guided shell with pop out wings like ERGM can make radical changes in direction, allowing it to dive vertically on a target after spending most of its flight time in a relatively horizontal glide. Technology like this should be quite able to allow a future low angle guns to fulfill most of the roles now requiring mortars or howitzer.

If scramjet shells ever work, something physically unlikely but far more plausible then interstellar warfare in the first place, then this will work all the better since a scram shell might actually continue accelerating after its fired (modern tank guns can launch projectiles to about mach 5.2 already) and the shockwave from a low angle shot alone would kill people and collapse weak structures.

Other options for nullifying laser defenses might center on using new submuntions designs, kinetic or explosive, which can be released very early in a shells flight and still reach the target area. That way one shell can turn into a couple targets, confusing and swamping the defenses and making a kill evaluation much more difficult.

[Cykeisme]

Firing at low angle has the inherent disadvantage when firing conventional ammunition the shells will also arrive at a low angle and thus cannot search behind obstructs like hills or plow deeply into the ground to destroy entrenchments. Thus the whole reason for howitzers in the first place.

If the velocity (and thus trajectory) of the shell can be configured to only just clear the tops of hills or other terrain obstructions by a small margin, it might actually be an advantage; the shell will be hidden from the target's defensive lasers until it clears the hill, minimizing the time window to kill the shell.

Of course, I suppose guided shells like you mentioned would be able to take even better advantage of this.

[Darth Wong]

Firing at low angle has the inherent disadvantage when firing conventional ammunition the shells will also arrive at a low angle and thus cannot search behind obstructs like hills or plow deeply into the ground to destroy entrenchments. Thus the whole reason for howitzers in the first place.

If the velocity (and thus trajectory) of the shell can be configured to only just clear the tops of hills or other terrain obstructions by a small margin, it might actually be an advantage; the shell will be hidden from the target's defensive lasers until it clears the hill, minimizing the time window to kill the shell.

Of course, I suppose guided shells like you mentioned would be able to take even better advantage of this.

The targeting system would need a pretty good picture of the intervening terrain. With a high firing arc, you don't really need to know much other than the distance and direction. Given those two pieces of information, you can just fire and assume that it won't hit anything en route.

[Fingolfin_Noldor]

To burn a hole into a shell probably requires a Continuous Wave laser rather than a pulse, unless the pulse and tracking system is good enough to inflict a small hole into the shell and detonate the explosives inside. It takes time for a pulse laser to penetrate a thick piece of metal and several pulses. One thing they are looking at right now is at a laser with non-gaussian intensity distribution, and the intensity distribution will look rather like a near continuous intensity over a certain radius (you can get that when you pump your laser medium to the point of saturation). Thereby, you get high continuous intensity over a spot, and you can make a bigger hole faster. This is where CW lasers are superior.

On the other hand, there might be a way to sheath a shell with a layer of plasma and deflect the laser, but that of course increases the complexity of the shell, and one might be better off with a missile like the Iskander SS-26.

[Darth Wong]

I suppose it should be pointed out that if cheap and powerful lasers become feasible, then people might start deploying orbital laser platforms.

[Fingolfin_Noldor]

I suppose it should be pointed out that if cheap and powerful lasers become feasible, then people might start deploying orbital laser platforms.

The Soviet Union had some plans to deploy CO2 lasers in orbit if I recall.

[Junghalli]

It's twenty to forty times the radius of the Sun, and only harnessing the Sun's energy. You want to add orders of magnitude to that, on a space ship.

Not on a ship, on a very large collection of ships. I was thinking of a large array of relatively small lasers and power plants just like a Dyson Sphere would be, not one giant laser and reactor.

Anyway it's fairly irrelevant as, thinking it over some more, the method that strikes me as best is laser bombardment from a distance followed by conventional forces mopping up any hardened or mobile facilities that manage to avoid being destroyed by it.

[Sea Skimmer]

The targeting system would need a pretty good picture of the intervening terrain. With a high firing arc, you don't really need to know much other than the distance and direction. Given those two pieces of information, you can just fire and assume that it won't hit anything en route.

For accurate predicted artillery fire the elevation of the firing unit and the target is already quite important. Otherwise if you aim at an enemy on a hillside you may miss him by hundreds of meters or very well hit the wrong side of the hill if he is on the reverse slope. Firing from inside one valley down into another can get even more complicated. So good topographical maps are a given, and computerized at this point.

Predicted fire has been in general use by field artillery since about 1917, though coastal artillery employed it earlier. Before that everyone just walked the guns on target with ranging shots and observers. That tended to give away strategic surprise when 1,700 guns lined up wheel all did this for weeks as they moved into attack positions before a grand week long bombardment.

Orbital lasers would probably not far that well in a counter battery duel with lasers of equal technology on the ground until all the ground dwellers space tracking facilities are disabled. That’s easier said then done since the defender can do orbital space tracking and target identification using entirely passive telescopes of unexceptional size. Until then the defender has surprise and concealment on his side and can chose when to expose a laser and take a favorable shot. You can start throwing a lot of technology at it for either side, but that natural advantage of ground cover is a big advantage given a light speed weapon.

[MKSheppard]

To burn a hole into a shell probably requires a Continuous Wave laser rather than a pulse, unless the pulse and tracking system is good enough to inflict a small hole into the shell and detonate the explosives inside.

No actually, what they do is burn enough of the shell's casing off to cause it to tumble, and aerodynamics takes over the rest.

[Darth Wong]

The targeting system would need a pretty good picture of the intervening terrain. With a high firing arc, you don't really need to know much other than the distance and direction. Given those two pieces of information, you can just fire and assume that it won't hit anything en route.

For accurate predicted artillery fire the elevation of the firing unit and the target is already quite important. Otherwise if you aim at an enemy on a hillside you may miss him by hundreds of meters or very well hit the wrong side of the hill if he is on the reverse slope. Firing from inside one valley down into another can get even more complicated. So good topographical maps are a given, and computerized at this point.

Actually, the mathematical concept of direction is three-dimensional, hence it includes elevation. You're thinking of the colloquial use of the term, which ignores the third dimension.

In any case, topographical maps would have to be quite accurate to fire shells at low elevations to barely skim over the tops of hills and ridges. Are they actually that good?

Predicted fire has been in general use by field artillery since about 1917, though coastal artillery employed it earlier. Before that everyone just walked the guns on target with ranging shots and observers. That tended to give away strategic surprise when 1,700 guns lined up wheel all did this for weeks as they moved into attack positions before a grand week long bombardment.

Orbital lasers would probably not far that well in a counter battery duel with lasers of equal technology on the ground until all the ground dwellers space tracking facilities are disabled. That’s easier said then done since the defender can do orbital space tracking and target identification using entirely passive telescopes of unexceptional size. Until then the defender has surprise and concealment on his side and can chose when to expose a laser and take a favorable shot. You can start throwing a lot of technology at it for either side, but that natural advantage of ground cover is a big advantage given a light speed weapon.

Granted, that makes sense.

[MKSheppard]

In any case, topographical maps would have to be quite accurate to fire shells at low elevations to barely skim over the tops of hills and ridges. Are they actually that good?

In 2000; NASA flew the Shuttle Radar Topography Mission (SRTM) to provide accurate elevation data for the world in conjunction with the National Geospatial-Intelligence Agency. Only the 30 meter datapoint sets for CONUS have been released publically; the rest of the world has to do with 90m datapoint sets.

So basically it's just a matter of space to store digital elevation maps of the world, and use those for starting points for artillery calculations. These maps can be supplemented by higher resolution digital radar maps from UAVs of threat areas, which might be a good use for UAVs; fly them over a possible threat area, and update your maps of the area before you launch a major operation.

[Sea Skimmer]

Actually, the mathematical concept of direction is three-dimensional, hence it includes elevation. You're thinking of the colloquial use of the term, which ignores the third dimension.

Well then I don’t know why you’d assert they don’t have or need terrain data in the first place. How else are you going to determine elevation of the firing battery and the target?.

In any case, topographical maps would have to be quite accurate to fire shells at low elevations to barely skim over the tops of hills and ridges. Are they actually that good?

I never said anything about skimming trees in the first place, that’d only work given an ideal combination of terrain features. However this would be a role for very small cruise missiles, something the US is already working on.

But anyway it’d be a huge improvement just to keep the shells below 1,000 feet AGL instead of lofting them several miles in the air or more. Enemy laser units are not just limited by the altitude of the projectile after all, but also local terrain features will mask fields of fire unless the laser parks on top of a hill with no trees or buildings around it. Such positions being painfully obvious, the laser isn’t likely to survive long if it occupies them.

The idea isn’t to make it impossible for any laser to intercept the shell, but to just ensure that only a small fraction of the enemy lasers can do so. That makes saturation fire much more realistic. You might only need to defeat the lasers defending a few enemy battalions with shells sailing over low, instead of those of two divisions plus those in the corps rear area if you fired a conventional shot that went up to 30,000 feet before it came back down.

In any case mapping is certainly good enough for all of this. The resolution on current military radar mapping system can distinguish a tracked vehicle from a wheeled vehicle. Compared to that measuring ground level accurately is nothing. Vegetation heights would be a concern if you want true tree skimming fire, but certain bands of radar can detect trees accurately and lidar could be used for the job in good weather. Both mapping radar and lidar can produce resolutions of under one meter under ideal circumstances. An invader would do his mapping from orbit before landing; a defender would have already done so.

[Darth Wong]

Actually, the mathematical concept of direction is three-dimensional, hence it includes elevation. You're thinking of the colloquial use of the term, which ignores the third dimension.

Well then I don’t know why you’d assert they don’t have or need terrain data in the first place. How else are you going to determine elevation of the firing battery and the target?

You need terrain data, just not the kind of really accurate terrain data you'd need for the "skimming ridges" trick I was questioning.

I never said anything about skimming trees in the first place, that’d only work given an ideal combination of terrain features. However this would be a role for very small cruise missiles, something the US is already working on.

Yeah, I know you didn't mention it. But you were answering my question which was posed to someone else who did propose it.

But anyway it’d be a huge improvement just to keep the shells below 1,000 feet AGL instead of lofting them several miles in the air or more. Enemy laser units are not just limited by the altitude of the projectile after all, but also local terrain features will mask fields of fire unless the laser parks on top of a hill with no trees or buildings around it. Such positions being painfully obvious, the laser isn’t likely to survive long if it occupies them.

The idea isn’t to make it impossible for any laser to intercept the shell, but to just ensure that only a small fraction of the enemy lasers can do so. That makes saturation fire much more realistic. You might only need to defeat the lasers defending a few enemy battalions with shells sailing over low, instead of those of two divisions plus those in the corps rear area if you fired a conventional shot that went up to 30,000 feet before it came back down.

In any case mapping is certainly good enough for all of this. The resolution on current military radar mapping system can distinguish a tracked vehicle from a wheeled vehicle. Compared to that measuring ground level accurately is nothing. Vegetation heights would be a concern if you want true tree skimming fire, but certain bands of radar can detect trees accurately and lidar could be used for the job in good weather. Both mapping radar and lidar can produce resolutions of under one meter under ideal circumstances. An invader would do his mapping from orbit before landing; a defender would have already done so.

That's pretty impressive; I didn't know they would have that kind of precision in their mapping.

[Sea Skimmer]

The only real limitation is that the higher the resolution you want the longer it takes the radar to make the map and the bigger the map becomes. As a result its normal to take a wide area picture, and then create highlights of areas that look interesting to do things like identifying specific vehicles. No sense wasting time looking for tanks on a steep mountain slope or the middle of a lake ect. Radars operating at a low resolution can also still detect moving ground targets, which once again facilitates the wide area coverage + spotlight function to get the most out of the radars finite duty cycle time.

The radar on the Global Hawk drone, which isn’t even all that big, can either map a 23 square km strip at 6 meter resolution or a 10 square km strip at 1.8 meter resolution in the same unspecified time period. It has other classified modes for higher resolutions. In all it can map 40,000 square miles per day at the 6 meter standard which is more then good enough for artillery planning. Dedicated ground surveillance radar planes like the E-8 JSTARS can do even better. Note also that these radars can function at a significant slant range (as much as 500km for the best ones, provided you have LOS, stupid mountains) so you do not necessarily have to overly the target to image it and risk being easily shot down.

All and all this is going to mean that long before anyone fights the first space war, let alone the first interstellar war, western armies are going to need to start making serious investments in training and materials for deception and camouflage again. Something everyone ignores heavily today.

[Sea Skimmer]

Also meant to add, on the matter of tree skimming, even assuming the terrain setup was such that all the ridges in the way are the same height or what have you to make the tactic effective, my hypothetical low angle guided shell still will need a set amount of distance and altitude to nose over from its low near horizontal trajectory onto the desired nose down vertical impact trajectory.

The more violent this maneuver can be the lower the shell can fly and the closer to the target an obstruction like a ridge can be without masking it from being hit at all. However more violence means a better control system, which is likely to add drag and weight to the shell detracting further from its speed and explosive payload. All else being equal, the lower the shell flies the more velocity it will need to reach a given range too.

Making this idea work would thus involve a number of tradeoffs and potentially several different rounds would be produced for the job.You might have relatively conventional high angle shells for long range when nothing but a lobbing trajectory will work, a low altitude shell for mid ranges, and then a tree skimming sabot shell that can only reach perhaps 10km but which can reach that range flying as low as the terrain can physically allow.

[SCVN 2812]

Its been submitted a few times that using kinetic kill vehicles, natural (such as the space Australia-asteroid) or artificial (big honkin' space guns) would be the natural solution if an invader is running up against defenses that would make a ship to surface duel a bad idea.

I have to wonder why its assumed that this is automatically a guaranteed win for the attacker. Wouldn't the very same defenses that stand off the attackers be useful in altering the trajectory of dangerously sized asteroid if not disabling its propulsion or even outright fragmenting it into less lethal pieces? If you have weapons and starships, the thought should probably have crossed someone's mind that someone might go to the time and effort to try and use natural rocks as cheap artillery and that maybe, just maybe, some long range missiles or x-ray lasers might be needed to complicate if not thwart just such an attack?