Gravitics array and counter missile defense

Vince wrote:I honestly doubt that CMs carry grav sensors. If they did, then since a grav sensor is a grav receiver, then it could receive grav pulses from the ship that launched it at FTL speeds. And as of the latest Honorverse novels at the time of this posting, the only missile that we know carries a grav receiver is the Apollo control missile (which also has carries a grav transmitter). And even that 3 stage MDM, with a fusion reactor instead of plasma capacitors, is twice the size of the attack missiles that it acts as a forward relay and AI for, and has no warhead of its own.

When the Manticorans were initially designing FTL into their attack missiles, one of the designs considered was to put the grav transmitter/receiver into each attack missile (pod launched, so the biggest they had for both mobile and static use). This was rejected because in order to maintain the existing size of the missile, they would have to remove one of the 3 drive stages in order to fit in the grav transmitter/receiver, turning the pod launched MDM into a pod launched DDM, albeit with FTL fire control.

Counter-missiles are much smaller than ship-killers and are described as being myopic, indicating that their on-board sensors are short-ranged. For these reasons I don't think we will see CMs mounting grav sensors any time soon in the Honorverse.

Well grav sensors don't appear to be omnidirectional - ships seem to need them on each flank and on each hammerhead. If a CM does carry one for intercept it's be in on it's nose. Little hard to receive signals from the launch ship, behind with you, a forward looking sensor...

Still I'd been assuming that it was the FTL transmitter that was the real size hog in an ACM, not the receiver, but there's little no no relevant text-ev that I can find to support that - so this is more the impression and assumption I ended up with than anything I can really support.


Of course even if a receiver capable of useful bandwidth at up to 3 million km (max Mk31 range) can easily be added to the rear of a CM you still seem to need a pretty hefty towed platform to generate all the FTL control signals - though probably not as big as the Keyhole II that has to reach 4+ lightminutes. (Same issue with trying to add receive-only FTL to Mk16s; currently only SD(P)s can generate the control signals and they'd be using those to talk to their more capable full up Apollo birds)

Jonathan_S wrote:Well grav sensors don't appear to be omnidirectional - ships seem to need them on each flank and on each hammerhead. If a CM does carry one for intercept it's be in on it's nose. Little hard to receive signals from the launch ship, behind with you, a forward looking sensor...

Still I'd been assuming that it was the FTL transmitter that was the real size hog in an ACM, not the receiver, but there's little no no relevant text-ev that I can find to support that - so this is more the impression and assumption I ended up with than anything I can really support.


Of course even if a receiver capable of useful bandwidth at up to 3 million km (max Mk31 range) can easily be added to the rear of a CM you still seem to need a pretty hefty towed platform to generate all the FTL control signals - though probably not as big as the Keyhole II that has to reach 4+ lightminutes. (Same issue with trying to add receive-only FTL to Mk16s; currently only SD(P)s can generate the control signals and they'd be using those to talk to their more capable full up Apollo birds)

If a CM can mount a gravitics array of sufficient resolution on its nose, then it does not need elaborate communications equipment of any sort. After the initial target assignment (by whisker laser?), then it can be completely self directed.

tlb wrote:

Jonathan_S wrote:Well grav sensors don't appear to be omnidirectional - ships seem to need them on each flank and on each hammerhead. If a CM does carry one for intercept it's be in on it's nose. Little hard to receive signals from the launch ship, behind with you, a forward looking sensor...

Still I'd been assuming that it was the FTL transmitter that was the real size hog in an ACM, not the receiver, but there's little no no relevant text-ev that I can find to support that - so this is more the impression and assumption I ended up with than anything I can really support.


Of course even if a receiver capable of useful bandwidth at up to 3 million km (max Mk31 range) can easily be added to the rear of a CM you still seem to need a pretty hefty towed platform to generate all the FTL control signals - though probably not as big as the Keyhole II that has to reach 4+ lightminutes. (Same issue with trying to add receive-only FTL to Mk16s; currently only SD(P)s can generate the control signals and they'd be using those to talk to their more capable full up Apollo birds)

If a CM can mount a gravitics array of sufficient resolution on its nose, then it does not need elaborate communications equipment of any sort. After the initial target assignment (by whisker laser?), then it can be completely self directed.

It's never going to be as capable as the ones on ships - and even those can get spoofed by sufficiently good gravimetric ECM - a totally hands-off self-homing CM seems unlikely. Especially given that despite having a 1.5 - 3 million km range against an MDM target it's launched when the inbound missile is way out at 15 - 19.4 million km (60-75 seconds before it reaches 1.5 - 3 million km). A CM mounted grav array is unlikely to be able to achieve lock on at those ranges - so it'll still need handholding from the vastly larger and therefore more sensitive ship mounted arrays until relatively close to impact.

Just like in modern air to air combat - the AIM-120 Amraam missile has onboard radar and in theory is capable of fire and forget attacks over it's 60 km range - but it's much more likely to actually hit when given mid-course guidance from an aircraft as the larger more powerful radar is less susceptible to decoys and jamming than the tiny one you can cram into a missile body.

Jonathan_S wrote:It's never going to be as capable as the ones on ships - and even those can get spoofed by sufficiently good gravimetric ECM - a totally hands-off self-homing CM seems unlikely. Especially given that despite having a 1.5 - 3 million km range against an MDM target it's launched when the inbound missile is way out at 15 - 19.4 million km (60-75 seconds before it reaches 1.5 - 3 million km). A CM mounted grav array is unlikely to be able to achieve lock on at those ranges - so it'll still need handholding from the vastly larger and therefore more sensitive ship mounted arrays until relatively close to impact.

Just like in modern air to air combat - the AIM-120 Amraam missile has onboard radar and in theory is capable of fire and forget attacks over it's 60 km range - but it's much more likely to actually hit when given mid-course guidance from an aircraft as the larger more powerful radar is less susceptible to decoys and jamming than the tiny one you can cram into a missile body.

To a certain extent it does not have to achieve lock on an individual missile at range, as long as it heads in the correct direction; so that when its resolving power is achieved it can target a singlet. I expect you are correct that this would degrade performance.
What I guess I do not understand what comprises "good gravimetric ECM"? The main variable was the amount of power put to the wedge. I am not sure if there is any other form factor that can be adjusted, but probably there is something that can be varied on a ship to enable it to hide at low power settings. However has that ever been available on a missile?

tlb wrote:To a certain extent it does not have to achieve lock on an individual missile at range, as long as it heads in the correct direction; so that when its resolving power is achieved it can target a singlet. I expect you are correct that this would degrade performance.
What I guess I do not understand what comprises "good gravimetric ECM"? The main variable was the amount of power put to the wedge. I am not sure if there is any other form factor that can be adjusted, but probably there is something that can be varied on a ship to enable it to hide at low power settings. However has that ever been available on a missile?

Ships explicitly have stealth that hides the grav signature - though there's a limit to how high an acceleration you can have while hiding it - full power wedges "burn through" the stealth. But we've seen Ghost Rider recon drones hide their grav signature at up to 5,000 gees!

As to how the missiles can spoof or jam grav sensors, I don't think we've been given any details. I can think of two basic approaches - one using grav projectors to modify the ripples along the alpha wall that the wedge generates and the other using placement and maneuvers of multiple missiles within the salvo to mask the number and location of all the missiles (kind of like the mess of ship drive signatures that Honor used to keep the Peeps at 4th Yeltson from realizing she had SDs hiding in her formation.

During the fight with Thunder of God it appears that jamming fooled all the BC's sensors, including her large shipboard grav sensors

Honor of the Queen wrote:Nine missiles charged through space, and Thunder of God’s computers blinked in cybernetic surprise at their unorthodox approach. They came in massed in a tight phalanx, suicidally tight against modern point defense . . . except that the three lead missiles carried nothing but ECM. Their jammers howled, blinding every active and passive sensor system, building a solid wall of interference. Neither Thunder nor their fellows could possibly “see” through it, and a human operator might have realized there had to be a reason Fearless had voluntarily blinded her own missiles’ seekers. But the computers saw only a single jamming source and targeted it with only two counter missiles.

And even earlier during the first Fearless's fight against Sirius ECM was able to hide that a missile was lagging about 35,000 km (0.5 seconds) behind - even against the targets large shipboard grav sensors

On Basilisk Station wrote:"They suckered me, Sir," Jamal admitted. Sweat beaded his forehead, but his fingers were already racing across his panel. "They fired a pair of laser warheads and staggered their launch." He pressed the commit key, locking his new firing orders into the point defense computers, and twisted around to return his captain's look. "The interval was less than half a second, but the lead missile mounted some kind of ECM emitter, Captain. I'm not sure what it was, but it covered the gap between their launch times. The computers thought they were coming in simultaneously, and our fire solution missed the separation, so we nailed the lead bird, but the second one got through.

And later when we do get to Dragons Teeth a single missile is able to somehow fool a ship's computers that it's become an entire pod worth of missiles despite the ship tracking inbounds on grav sensors as well as active ones like radar. That's spreading those false signal apparent sources over at least 1,600 square km (up to 22, 23 km away in every direction).

So while it's unclear exactly how they're doing it, it's clearly more that varying apparent wedge strength. Even at the start of the series they seem to be able to create significant uncertainty about their actual position despite the FTL read on it. (And presumably if they can do that they can spoof heading changes for long enough to trick a CM, or the tac computer controlling it, into veering off to an incorrect intercept point; or continuing straight on after the missile did swerve)

Jonathan_S wrote:Ships explicitly have stealth that hides the grav signature - though there's a limit to how high an acceleration you can have while hiding it - full power wedges "burn through" the stealth. But we've seen Ghost Rider recon drones hide their grav signature at up to 5,000 gees!

As to how the missiles can spoof or jam grav sensors, I don't think we've been given any details. I can think of two basic approaches - one using grav projectors to modify the ripples along the alpha wall that the wedge generates and the other using placement and maneuvers of multiple missiles within the salvo to mask the number and location of all the missiles (kind of like the mess of ship drive signatures that Honor used to keep the Peeps at 4th Yeltson from realizing she had SDs hiding in her formation.

During the fight with Thunder of God it appears that jamming fooled all the BC's sensors, including her large shipboard grav sensors

Honor of the Queen wrote:Nine missiles charged through space, and Thunder of God’s computers blinked in cybernetic surprise at their unorthodox approach. They came in massed in a tight phalanx, suicidally tight against modern point defense . . . except that the three lead missiles carried nothing but ECM. Their jammers howled, blinding every active and passive sensor system, building a solid wall of interference. Neither Thunder nor their fellows could possibly “see” through it, and a human operator might have realized there had to be a reason Fearless had voluntarily blinded her own missiles’ seekers. But the computers saw only a single jamming source and targeted it with only two counter missiles.

And even earlier during the first Fearless's fight against Sirius ECM was able to hide that a missile was lagging about 35,000 km (0.5 seconds) behind - even against the targets large shipboard grav sensors

On Basilisk Station wrote:"They suckered me, Sir," Jamal admitted. Sweat beaded his forehead, but his fingers were already racing across his panel. "They fired a pair of laser warheads and staggered their launch." He pressed the commit key, locking his new firing orders into the point defense computers, and twisted around to return his captain's look. "The interval was less than half a second, but the lead missile mounted some kind of ECM emitter, Captain. I'm not sure what it was, but it covered the gap between their launch times. The computers thought they were coming in simultaneously, and our fire solution missed the separation, so we nailed the lead bird, but the second one got through.

And later when we do get to Dragons Teeth a single missile is able to somehow fool a ship's computers that it's become an entire pod worth of missiles despite the ship tracking inbounds on grav sensors as well as active ones like radar. That's spreading those false signal apparent sources over at least 1,600 square km (up to 22, 23 km away in every direction).

So while it's unclear exactly how they're doing it, it's clearly more that varying apparent wedge strength. Even at the start of the series they seem to be able to create significant uncertainty about their actual position despite the FTL read on it. (And presumably if they can do that they can spoof heading changes for long enough to trick a CM, or the tac computer controlling it, into veering off to an incorrect intercept point; or continuing straight on after the missile did swerve)

Although the fight of Fearless against the Sirius in OBS could be pure electromagnetic counter measures if the battle computer was mainly using the radar for information, it does not seem possible the situation against Thunder of God could be the same. And yet we are not given anything that suggests how a mechanism could exist to manipulate the information from the gravitics array in that way. I hate to say "handwavium", but I do not know what else to think.
We know that the FTL transmitter is at an extremely crude stage at the point of HotQ. The spider drive exerts tremendous force on the normal to hyperspace boundary without producing more than the smallest ripple, so that does not seem like a realistic method. The fuzz at the beginning of 4th Yeltsin was due to close packing of ships at the limits of resolution; as they got closer the ships were resolved.

So for reasons due to purposes of the narrative my ideas are junk.