Is 4e defensive ECM too wimpy?

[Michael Thayne]

In Spaceships, Defensive ECM provides relatively modest benefits against same-TL opponents with a tactical array: between -1 and -3. You get a bigger bonus against lower-TL or civilian ships, but in serious military engagements, it seems somewhat questionable whether the systems are worth their hefty price tag.

A few other 4e products copy this approach, suggesting this isn't something meant to be peculiar to the Spaceships line. An article in Pyramid #3/53 gives real-world jet fighters ECM systems that inflict between -1 and -3 penalties on attackers, while in GURPS Mars Attacks fighters get a full -6 ECM penalty, consistent with a heavy commitment to ECM and nobody having the tactical arrays to target them effectively (apparently not even the Tiger Corps, a high TL force fighting on the human side).

This seems to be a marked contrast to classic Vehicles, where a variety of specific ECM systems are available with large benefits. Flares (p. 170) can provide a -5 penalty to IR homing attacks. Spoofing (p. 171) can force guessing games around which sensor contacts, and chaff can impose a whopping -10 penalty on radar detection. Extremely high jammer ratings (p. 60) are also allowed.

I'm not certain of this, but I suspect Vehicles is more realistic. Reading up on recent naval battles, electronic countermeasures seem to have been decisive in many naval battles since the Battle of Latakia in 1973, which Wikipedia claims was "the first naval battle in history to see combat between surface-to-surface missile-equipped missile boats and the use of electronic deception." Reading the description of the battle, it seems it might have turned out differently if not for Israel's use of chaff as a defense, and this appears to be true of other recent naval battles I've read up on.

Even in battles where ECM may not quite have worked out as-hoped, their effect was not small. For example, there was an incident in the Falklands War where a British transport was sunk by two Exocet missiles—which had been intended for a frigate, but diverted by the frigate's ECM. Not an ideal result, but also not one that would be accurately captured by applying a penalty ranging from -1 to -3 to the missile attack on the frigate.

Am I right that the 3e approach was more realistic? If so, what could be done to make appropriately effective ECM systems available in Spaceships?

[David Johnston2]

Originally Posted by Michael Thayne

Am I right that the 3e approach was more realistic? If so, what could be done to make appropriately effective ECM systems available in Spaceships?

Ain't nothing wrong with just increasing the modifier.

[Anthony]

If you wanted to pick a topic where accurate information is hidden in a haze of deception and classification, hard to pick something better than ECM. It's also an incredibly moving target, so an answer that's good for one year may be invalid a few years later. However, there's reason to think space is a very poor environment for ECM.

[David Johnston2]

Originally Posted by Anthony

If you wanted to pick a topic where accurate information is hidden in a haze of deception and classification, hard to pick something better than ECM. It's also an incredibly moving target, so an answer that's good for one year may be invalid a few years later. However, there's reason to think space is a very poor environment for ECM.

Oh yeah. Realistically all you have to is point your weapons at the heat source. ECM would be a waste of time.

[Anthony]

Originally Posted by David Johnston2

Oh yeah. Realistically all you have to is point your weapons at the heat source.

Well, directional dazzlers of various types are possible (decoys, unless ships are immobile, are much less possible; it's very hard to hide the mass of a rocket). The problem is that it's a very low noise environment, and thus there's not much for a sensor to get confused by.

[Michael Thayne]

Originally Posted by David Johnston2

Ain't nothing wrong with just increasing the modifier.

That may not be totally realistic either if the most effective ECM systems are limited by ammo—as are decoys and chaff, among other things.

Originally Posted by David Johnston2

Oh yeah. Realistically all you have to is point your weapons at the heat source. ECM would be a waste of time.

I'm not sure if this is really true, both because of decoys (which I'll get to in a bit) and because accurate targeting at a range of hundreds of miles may require use of active sensors, which would be vulnerable to jamming and chaff. Spaceships in fact seems to assume use of active sensors for targeting. Spaceships p. 45 mentions targeting as one of the "main uses" of active sensors, and says active sensors are "integrated" into the combat rules, which I think is the main justification for the implied +9 bonus to all vehicular weapons attacks mentioned in the sidebar on p. 66. Comparing to Ultra-Tech, targeting with active sensors (p. 150) seems to be the only thing that could justify a bonus like that.

Originally Posted by Anthony

Well, directional dazzlers of various types are possible (decoys, unless ships are immobile, are much less possible; it's very hard to hide the mass of a rocket). The problem is that it's a very low noise environment, and thus there's not much for a sensor to get confused by.

Certainly long-lasting decoys are going to be difficult to manufacture, without being almost as expensive as the warships they protect. But decoys that very briefly produce the IR signature of a much larger object are believable, AFAICT.

[Ulzgoroth]

Originally Posted by Anthony

(decoys, unless ships are immobile, are much less possible; it's very hard to hide the mass of a rocket).

The possibility of decoys depends a bit on what you're trying to decoy.

Many decoys planetside aren't likely to deceive a sophisticated or manned sensor array. But that's not really a problem for them since they're intended to fool terminal guidance on missiles or torpedoes, which is dumber and working from smaller sensors.

[Ulzgoroth]

Originally Posted by Michael Thayne

Certainly long-lasting decoys are going to be difficult to manufacture, without being almost as expensive as the warships they protect. But decoys that very briefly produce the IR signature of a much larger object are believable, AFAICT.

The sticky problem isn't so much the heat as the mass and exhaust. A sophisticated observer can look at your rocket reaction mass and determine the generated thrust, and thus know how much you mass from your observed acceleration.

The question is whether there are observers you want to fool that can't pull that off (fast enough).

[Anthony]

Originally Posted by Michael Thayne

I'm not sure if this is really true, both because of decoys (which I'll get to in a bit) and because accurate targeting at a range of hundreds of miles may require use of active sensors, which would be vulnerable to jamming and chaff.

Unfortunately, you have that backwards, because those vulnerabilities are not generic properties of active sensors, they're properties of radar, and radar is a poor sensor for use at space combat ranges because it has low angular resolution unless very very large. To get, say, 1 meter resolution at a range of 1,000 kilometers requires your sensor array to be 1 million wavelengths. That's pretty easy in optical and near infrared (1 meter optics will do the job), requires multiple linked sensors with an effective size of 10m or so for infrared, and is basically impossible for radar.

Also, GURPS rules notwithstanding, the most likely sensors for space combat would use a laser for rangefinding and are otherwise passive. Active sensors are fairly cruddy at space combat ranges.

[Michael Thayne]

Originally Posted by Ulzgoroth

The possibility of decoys depends a bit on what you're trying to decoy.

Many decoys planetside aren't likely to deceive a sophisticated or manned sensor array. But that's not really a problem for them since they're intended to fool terminal guidance on missiles or torpedoes, which is dumber and working from smaller sensors.

The stupidity of missiles admittedly is one thing that makes me wonder if we can extrapolate from current naval warfare to even near-future (TL9) space warfare. OTOH, a sophisticated AI on a brilliant missile isn't helpful if the target and its decoy look like equally large point-sources on its infrared sensor, so maybe decoys would stay viable.

Originally Posted by Ulzgoroth

The sticky problem isn't so much the heat as the mass and exhaust. A sophisticated observer can look at your rocket reaction mass and determine the generated thrust, and thus know how much you mass from your observed acceleration.

The question is whether there are observers you want to fool that can't pull that off (fast enough).

Don't those calculations require many observations over an extended period of time, though? If so, it might not be relevant for decoys launched mid-combat.

Originally Posted by Anthony

Unfortunately, you have that backwards, because those vulnerabilities are not generic properties of active sensors, they're properties of radar, and radar is a poor sensor for use at space combat ranges because it has low angular resolution unless very very large. To get, say, 1 meter resolution at a range of 1,000 kilometers requires your sensor array to be 1 million wavelengths. That's pretty easy in optical and near infrared (1 meter optics will do the job), requires multiple linked sensors with an effective size of 10m or so for infrared, and is basically impossible for radar.

Also, GURPS rules notwithstanding, the most likely sensors for space combat would use a laser for rangefinding and are otherwise passive. Active sensors are fairly cruddy at space combat ranges.

Fair. That raises the question: how hard is it to spoof laser rangefinding?