Sprint drive

cthia wrote:Our sling and rock works because we always have the bird in sight. And the bird does not have a burst of acceleration or ECM to cause us to temporarily lose sight.

Weird Harold wrote:Never been bird hunting/watching, have you? Birds accelerate and decelerate very quickly and unpredictably.

I'm native american.

cthia wrote: In the Honorverse, tracking = sight. Tracking, sights missile at .81c. We time our rock for .81c. Sprint mode activates. Oops.

Weird Harold wrote:FWIW, missiles that are trackable are accelerating. If it is doing .81C when detected, it is going to be faster than .81C by the time your counter-missile fire reaches it. The question for defensive fire control is "how much faster." With fixed drive settings that can't be changed on the fly, it's an easy answer.

When and where missiles change drives -- NOT just drive modes -- is fairly predictable, especially if you have data on the opponent's missiles. The choices of where a "lost" missile could be are fairly limited -- not every missile will be reacquired, of course, but "speed" only gets you one "surprise" before the CM software gets updated for the second stage accel.

Now if the accel of all stages is infinitely variable during flight...

But that is a consistent and smooth acceleration and consistent and smooth tracking. Sprint mode denotes a significant change in acceleration which has to transmit that change to hardware which has to sync.

If used against point defense, the limiting factor isn't so much the software, but the hardware being controlled. Software can resolve itself almost immediately compared to the lag in hardware. There are no moving parts in software.

It is the difference between "in theory" and "in practice."

I would imagine that even Manty point defense software would have to be rewritten when first encountering this tactic.

Jonathan_S wrote:

Weird Harold wrote:No textev required, the principle is as old as trying for lunch with the first rock thrown at a bird.

In terms of the Honorverse, there's no no light-speed sensor that can directly detect an incoming missile in time to intercept it, so they are restricted to what can be determined by tracking the missile wedge and any emissions the missile might put out.

Computing a lead angle for a constant speed and course is trivial; allowing for a static set of known accelerations for a possible second stage is also trivial.

Computing a lead angle for a target that is randomly making minor changes in course is more difficult. Throw in random variations in acceleration/speed and computing a lead angle becomes very difficult. Honorverse missiles can vary their course but they can't vary their acceleration/speed. Even a few G's of acceleration change should throw off interception computations if anyone could figure out how to do it with missile drives.

In modern terms it's called "Jinking" to avoid SAM or AA missiles, and the ASG-22 Lead Computing Optical Sight mounted in the F-4(D) Phantoms I spent my career working on didn't even try for that level of prediction. (1960's vintage analog lead computer.)

Well yes, if you could vary the same drive up and down a thousand gees or so you'd throw off the targeting solution a bit. Though the wedge position can be seen FTL by the targeted ship, so your not generating much confusion. And of course that would be a massive breakthrough in drive tech. David set missiles up where the trade-offs for having acceleration over 10 times what a drone has is 1) much shorter drive endurance and 2) no ability to change acceleration setting once a drive is lit off. (Heck, CM's pay a further penalty for their even higher acceleration in that their nodes can't be dialed down even before lighting off, they only have 100% power)


Also by the time you get to the 1.5 - 2 million km range a CM can engage the attacking missile has to be on a vector that's pretty much towards its target. So even a 10 - 20% change in acceleration on their vector mostly towards the target will generate a surprisingly small lateral displacement. The target's CMs (or its nearby escorts) are basically flying back up the inbound track, it's not trying to hit a bird that's flying mostly perpendicular to you. Plus the CM only has to get within 10 km or so to kill the inbound.

I just don't think continuously adjustable acceleration would be as big an advantage as you do.

Which is not to say "on an equal an opposite vector," which would have to be the case against Manty missile fire that has benefit of real time data, control and access to optimum time to sprint -- compounded with enemy missile/CM specs.

Jonathan_S wrote:Also by the time you get to the 1.5 - 2 million km range a CM can engage the attacking missile has to be on a vector that's pretty much towards its target. So even a 10 - 20% change in acceleration on their vector mostly towards the target will generate a surprisingly small lateral displacement. The target's CMs (or its nearby escorts) are basically flying back up the inbound track, it's not trying to hit a bird that's flying mostly perpendicular to you. Plus the CM only has to get within 10 km or so to kill the inbound.

I just don't think continuously adjustable acceleration would be as big an advantage as you do.

By itself, variable accel won't do a great deal. It is simply a missing component of maneuverability that could be of benefit in penetrating enemy defenses.

It would be especially useful against the LAC screen's counter-missiles. They can't be on a straight line to the enemy without blocking out-going missile fire.

Where it would be of the most use is in the PDLC zone. PDLC laser beams can't maneuver or guide into a target, so anything that changes the target's position from the predicted position will generate a miss.

Stages don't really exist on GA missiles. The are separate drive units to burn out but they coexist, it's not like a typical rocket where the boosters fall off when they're spent. (Sollie missiles are, though!)

Take what probably is an oversize MDM. Outfit it with the drive system used by recon drones. Obviously it can't be used at the same time as the main drive but it could be used on the ballistic components. As it's a standard restartable drive they can do what they want with it.

You get all the defensive benefits of having an operating drive and a respectable ability to move away from where the enemy thinks the missile is.

The recon drone drive can put out enough acceleration that the missile can easily match any evasion it's target does, when the last stage lights as it closes it's going to be right on target rather than way off target if the target tried to move laterally while the missiles were drifting.

It also opens up some interesting strike options against heavily defended targets. Take one of those Rolands. They drop in to the target far out, "launch" their entire missile load and then build velocity towards the target. Go doggo on a path that's going to take them maybe 30mkm above the ecliptic and a decent fraction of lightspeed. The missiles are lagging a bit behind but aimed at the target. Recon drones lead the missiles by a good margin.

The ship controlling everything is simply a hole in space until it has to send out the attack orders to the missiles. (And signals don't seem to break stealth so even that doesn't reveal them.) The target sees a "ship" firing on them--but they can't find the ship (because it's really lying doggo far away) and have nothing to shoot at. Solarian defense is not able to substantially stop such missiles no matter how much of it there is--this lets one ship take a good peck at the hardest of targets.

quite possibly a cat wrote:If I was on the Solly or Malign side and designing missiles I would look into making a low powered first stage. Call it "marathon", and scale up the missile so the CM-derived "sprint" can slice through enemy counter missiles and survive. Also I'd want to see if I can't fit a nice energy mine or graser on as the warhead so I can out-range classic point defense.

Bluesqueak wrote:

cthia wrote:I certainly agree with you for the most part, Bluesqueak, however, I think you and I disagree on what is actually considered "copious" amounts of drive time left.

I'm specifically recalling the demonstration launch during SoV when the missile continued on, paraphrasing "...one minute...two minutes...three minutes...four minutes?," beyond targeted SLN ships, recognized by the frightened SLN CO.

I forgot the encounter. No time to look it up. Three or four minutes inside your missile envelop should cause the RMN AI to select available sprint mode. Certainly the AI can calculate :CONDITIONS :SPRINT MODE.

Ah, that one. I did have time to look it up - Chapter 67, I think. But you're misremembering it; the countdown is the horrified Solly crew realising the Manty missile has just gone one minute ... two minutes ... three minutes beyond the powered flight time of their own missiles. It's still heading towards them, though. And, in fact is still under powered flight (and so can dodge their anti missile defences) right up to the point where it goes past them and explodes at a safe distance from their ships.

That final distance as it goes past, blowing raspberries, is something like 85 seconds, not the eight minute countdown.

I do declare, please pardon my manners. This is indeed the passage in question. My apologies for mis'membering.

Still, copious amounts of drive time left simply seems like a waste. And the last paragraph of the referenced passage that Vince so kindly included seems to infer that there is indeed plenty of drive time wasted...

He felt his jaw clamping harder and harder in something very like horror. He felt the tension—the fear—of his bridge crew as that incredible missile just kept coming for them. And then, nine impossible minutes after launch, it streaked directly past Harpist—still under power, still able to execute its final attack maneuvers—and detonated harmlessly a hundred and fifty thousand kilometers ahead of her.

Oh well, s'pose it's better to waste drive time than people, places or things.

Loren Pechtel wrote:Stages don't really exist on GA missiles. The are separate drive units to burn out but they coexist, it's not like a typical rocket where the boosters fall off when they're spent. (Sollie missiles are, though!)

Take what probably is an oversize MDM. Outfit it with the drive system used by recon drones. Obviously it can't be used at the same time as the main drive but it could be used on the ballistic components. As it's a standard restartable drive they can do what they want with it.

I'm pretty sure a recon drone's drive is a large part of why they run over 10 times the size of a missile (and have 1/10th the acceleration). So that'd be a very oversize MDM

There's also the minor issue that you'd have to shield the inactive missile drive rings from the active drone drive ring, but I assume the MDM 'baffle' tech would work there as well. I'm not sure if a missile's drive could give the same accel putting an object that about 10 times as large. So the final sprint might be slower.

And of course with lower accel the drone/missile hybrid would take longer to cross the defensive zones of the target - again appearing the offset much if not all of the advantage of the momentary surprise of jumping to a radically different acceleration.


Though Manticore is clearly not entirely opposed to using big expendable weapons when it makes sense (Mistledoe) to date they've only done so when the drone drive weapon can sneak all the way to detonation range.

cthia wrote:

Bluesqueakpip wrote:Ah, that one. I did have time to look it up - Chapter 67, I think. But you're misremembering it; the countdown is the horrified Solly crew realising the Manty missile has just gone one minute ... two minutes ... three minutes beyond the powered flight time of their own missiles. It's still heading towards them, though. And, in fact is still under powered flight (and so can dodge their anti missile defences) right up to the point where it goes past them and explodes at a safe distance from their ships.

That final distance as it goes past, blowing raspberries, is something like 85 seconds, not the eight minute countdown.

I do declare, please pardon my manners. This is indeed the passage in question. My apologies for mis'membering.

Still, copious amounts of drive time left simply seems like a waste. And the last paragraph of the referenced passage that Vince so kindly included seems to infer that there is indeed plenty of drive time wasted...

He felt his jaw clamping harder and harder in something very like horror. He felt the tension—the fear—of his bridge crew as that incredible missile just kept coming for them. And then, nine impossible minutes after launch, it streaked directly past Harpist—still under power, still able to execute its final attack maneuvers—and detonated harmlessly a hundred and fifty thousand kilometers ahead of her.

Oh well, s'pose it's better to waste drive time than people, places or things.

No problem; I misremember stuff at times.

I'd say a minute or so isn't copious, because it allows the launching ship to retarget if the tactical situation changes. For example, enemy ships striking their wedges, targeted enemy ship is now in very small pieces, tactical officer realises threat B is more important.

A minute or so of 'spare' manoeuvre time can solve all those problems...

Bluesqueak wrote:
A minute or so of 'spare' manoeuvre time can solve all those problems...

Ok, everyone, let's back up - what are we trying to maneuver against? and When?

Starting last. A modern PDLC has a range of 50-100,000 KM

A modern laserhead will fire at 40-50,000 KM
(an old laserhead will fire at 20,000 KM), meaning nuke goes boom, lasers come out.

Before a laserhead "fires", it drops it's drive and ejects it's laserheads which position themselves a specific distance from the missile and align on target, this is done when the missile is about 100,000KM from the target. @.8c, this phase is covered in .2-.25 seconds

SO the missile is not maneuvering (or even accelerating) at all inside of PDLC range.

Prior to entering ejecting the laserheads, the missile acquires target, aligns the missile, and prepares to eject the laserheads. This is done beginning in the 200-250,000 KM range from the target. This phase is covered in ~.4-.6 seconds)

At this point the missile is very susceptible to CMs because it is no longer maneuvering. But ECM is supposed to cover.

So any use of a sprint drive is against the CM range, NOT the PDLCs, who are busy popping off missile as they align themselves to fire.

Theemile wrote:

Bluesqueak wrote:
A minute or so of 'spare' manoeuvre time can solve all those problems...

Ok, everyone, let's back up - what are we trying to maneuver against? and When?

Starting last. A modern PDLC has a range of 50-100,000 KM

A modern laserhead will fire at 40-50,000 KM
(an old laserhead will fire at 20,000 KM), meaning nuke goes boom, lasers come out.

Before a laserhead "fires", it drops it's drive and ejects it's laserheads which position themselves a specific distance from the missile and align on target, this is done when the missile is about 100,000KM from the target. @.8c, this phase is covered in .2-.25 seconds

SO the missile is not maneuvering (or even accelerating) at all inside of PDLC range.

Prior to entering ejecting the laserheads, the missile acquires target, aligns the missile, and prepares to eject the laserheads. This is done beginning in the 200-250,000 KM range from the target. This phase is covered in ~.4-.6 seconds)

At this point the missile is very susceptible to CMs because it is no longer maneuvering. But ECM is supposed to cover.

So any use of a sprint drive is against the CM range, NOT the PDLCs, who are busy popping off missile as they align themselves to fire.

I'm probably to blame for this mess. Mea culpa.

It is because I hadn't thought the notion through of whether the tactic would be used against CMs or PDLCs. Which changes the strategy quite a bit. Theemile's post gives lots of good detailed information I didn't know. Kudos Theemile.

Does point defense remind anyone else of the mechanics of shooting skeet? Always has me. Let's call it the baggage of life, shall we? In particular, our many hats.

*Nice video that shows how to determine your eye dominance.

Marrying the two as a mind experiment is interesting. Do think ECM when the speaker speaks of the different lines given you by many of the clubs. Background clutter.

I'll concur with the
"Never been bird hunting/watching, have you? Birds accelerate and decelerate very quickly and unpredictably." comment. Also with point defence being like the mechanics of skeet shooting. Used to do a lot (a really lot over more than 30 years) of both.

Skeet used to be used to teach ariel gunners how to deal with moving targets and develop a feel for the amount of lead you needed to put your projectiles where the target was going to be in the time it would take for said projectile to get to that point. Both skeet and trap were used because while skeet is mostly passing shots, trap forces you to deal with longer distances and relative rates of change. Bear in mind that with both skeet you are shooting from known distances at MOSTLY similar flight paths.
And, no, the targets in skeet and trap do NOT always go exactly the same path (for each station- and the relative path and changes in speeds vs distance you are dealing with change based on swith "station" you are shooting from. With skeet the birds should always fly though a ring of set diameter just outside the box of the # 8 station. But they don't. That is due to all sorts of things such a chipped or partialy broker bird- which changes the speed of what does come out and makes the bird behave erratically. Wind- any wind, or rain will also change the flight action. The dam things will do the oddest things rising, dipping, etc.
Trap is shot at birds going away. The thing is that the machine doing the throwing is moving between several directions of throw so the angle the bird is going away from you isn't known till it actualy leaves the house. At that point exactly the same things will effect the clay pigeons as happens from skeet except that with trap thay are all starting from very close to ground level and climbing before then start to drop in a semi-ballistic path. Think Firsby thrown on a low climb and eventual settling and slowing a bit.

Bird shooting. They change speed, veer off, cut in various directions, tower up or dive- no particular reason- and then you get to deal with the things the bird is also dealing with such as wind. And they may be doing most of that at the same time though towering does tend to slow them down a bit because they are going UP so if they were going "straight" forward the moment before they are going to start loosing speed as they change direction and go for altitude. Birds DO understand aerodynamics at least as far as it applies to their own ability to fly and make both sudden and exceedingly minor course corrections even if truly awful wind conditions, [try duck shooting on salt water in January in a snow storm] and most of the time they are going to be activly attempting to be tough targets. Heck, for a lot of birds, if you are chasing them in woods, they are already going to be needing to fly (at flank speed) though an obstical course in 3 dimensions to get away and they are going to be moving to avoid stuff you can't see.

I have seen a grouse flush in light woods, get shot at and keep accelerating and rising slightly- until it slammed into the rock-face on a steep hill. Examination found that it had been hit (and wouldn't have lived) but its brain was focusing on faster and higher but seems to have missed "collision alert" and it tried to fly though something.

It still boils down to shooting at someting, where you think it is going to be such that your shot (which is going to be slowing down and spreading out and opening "holes" in your pattern) will intersect with the target at a future point......and you had best keep swinging your gun to keep adjusting where it is pointing because it DOES take time between when you think "shoot", your finger pulls the trigger, the shell goes off AND the shot exits the barrel. You stop swinging (or lighten up on the swing) and you are going to miss because you will have shot BEHIND the trajectory of the bird.