Detecting a Fleet

I keep seeing in the Honorverse that an attacking fleet, even if anticipated, will not show up on sensors until they exit hyper into normal space. Why not? Why doesn't Manticore have sensors seeded around the system in hyper? It might be difficult, it might be expensive, but if there's anyone in the explored galaxy that could manage it, it would be Manticore. Think of the advantages that would accrue to a warned system defense force. If you only stationed a dozen or so destroyers in the area, that would be a help. How hard could it be to detect an approaching fleet in hyper if you have the hardware to do so? There must be way, and it really doesn't look all that difficult to me.

This seems to be particularly important in regards to the impending attack on Beowulf. The Sollie fleet is certainly going to be coming in through hyper. Early detection would be a major help to the defending force.

zuluwiz wrote:I keep seeing in the Honorverse that an attacking fleet, even if anticipated, will not show up on sensors until they exit hyper into normal space. Why not? Why doesn't Manticore have sensors seeded around the system in hyper? It might be difficult, it might be expensive, but if there's anyone in the explored galaxy that could manage it, it would be Manticore. Think of the advantages that would accrue to a warned system defense force. If you only stationed a dozen or so destroyers in the area, that would be a help. How hard could it be to detect an approaching fleet in hyper if you have the hardware to do so? There must be way, and it really doesn't look all that difficult to me.

This seems to be particularly important in regards to the impending attack on Beowulf. The Sollie fleet is certainly going to be coming in through hyper. Early detection would be a major help to the defending force.

No, detection range in hyper is too short to be usable. Plus once they emerge in hyper they have at least an hour before they usually can threaten anything you really deeply care about.

The large array in normal space has a range measured in light-months. In hyper, sensor range is heavily reduced, into the range of light-minutes.

Then the hyperspace sensors has to communicate with normal space somehow. That means keeping courier boats(or warships) up there on standby with their hyper generator spun up all the time. You may as well just use destroyers to do the job - at least they'll be able to randomise their positions regularly.

Unfortunately, an enemy force which translates into, say, the alpha band several light hours out would not be detected. It could then build velocity and then cut their drives, attempting a surprise attack on any sensors or watchdogs in hyper or even go for a translation, beating the so-called sentries. This problem is repeated in each higher band, with decreasing sensor ranges and the additional liability of having to translate down more bands for the defenders.

This doesn't really add much warning time compared to the delay imposed upon the attacker by having to emerge beyond the hyper limit. Of course, now that MDMs are around, a lot of places became quite exposed - such as Sphinx or Mars.

Systems with Hermes buoys might be able to push those sentry destroyers out a bit and gain a few more minutes. Unfortunately, the time it takes for such a transmission to be relayed to Home Fleet's CO or the Admiralty probably means everyone goes to battle stations when the massive hyper footprints are detected anyway.

Well, there must be some reason that it's impractical, because otherwise people would be doing it.

My personal guess is that it's because detecting things in hyper is too short-ranged and unreliable to provide enough useful warning given the investment. It's been noted several times that detecting things in hyper is harder than in realspace - particle densities are higher, and even absent that the More Than Honor appendix gives a hard cap on detection range of about 20 light-minutes due to the basic physics of hyperspace.

This means that stationing pickets in hyper is not going to give you very much advance warning. At 0.6c (the maximum safe speed in hyper) an attacking fleet will cross that 20 LM range in about 30 minutes, so even assuming you can detect them at maximum range and instantly drop to realspace to get off a contact report, you're only getting a half-hour's warning. And given that said fleet is not going to be accelerating, the detection range is likely to be shorter even if they're not actively in stealth, which further reduces your warning time.

The other problem is how hyper has multiple bands. Pickets in the alpha bands aren't going to do you any good if the attacking fleet doesn't drop to the alpha bands until they're in the process of translating all the way back to realspace (a good example of this is when Honor and company arrive in Yeltsin in CH. 5 of The Honor of the Queen). You'd need pickets in every hyper band that you think they might use, which both multiplies the number of pickets needed and also means that the pickets in higher bands will take longer to translate all the way back to realspace to get off a contact report. (And in HotQ it took the convoy almost 10 minutes to translate down from the delta bands into realspace, which would cut down your warning time significantly.)

Ultimately my guess is that it's just impractical, even if it may be theoretically possible.

zuluwiz wrote:I keep seeing in the Honorverse that an attacking fleet, even if anticipated, will not show up on sensors until they exit hyper into normal space. Why not? Why doesn't Manticore have sensors seeded around the system in hyper?

1: Getting the warning from Hyper into N-Space requires a physical transition. That means warning of an incoming fleet would only be a few minutes faster than waiting for the fleet to generate a hyper-footprint.

2: Which of five (or more) levels of Hyperspace do you put your sensor net in? If you just put it in the Alpha band, you have a few seconds to detect a fleet as it passes through on a crash transition to N-Space. Your warning then comes a few minutes to an hour after the fleet arrives because you have to wake up your hyper-generator and physically drop into N-Space to transmit a warning. (or put unconscionable wear on your hyper-generator and wait on high alert.)

Here's an interesting thought though. Using the Sol system and some of the drawn diagrams of the Manticore system, etc. as prototypes... and an astral "fact".

In order to successfully attack and reach the orbitals of Sol, for example, to a certain extent you're not going to be able to get any force advantage based on surprise by coming in on the other side of the star system, etc. So most fleets and all SDM armed combatants come in at the minimum safe approach distance to the planet that isn't absolutely predictable.

Seed the asteroid belts within the appropriate ranges with towed but unfired up ghost-rider FTL recon drones. Designed to launch and follow that enemy fleet in upon arrival. About the time they finish deploying pods, a certain percentage go 500M-Ton ker-blooey to take out said pods, and the rest to "light 'em up, buoys!". Thoughts?

SharkHunter wrote:Here's an interesting thought though. Using the Sol system and some of the drawn diagrams of the Manticore system, etc. as prototypes... and an astral "fact".

In order to successfully attack and reach the orbitals of Sol, for example, to a certain extent you're not going to be able to get any force advantage based on surprise by coming in on the other side of the star system, etc. So most fleets and all SDM armed combatants come in at the minimum safe approach distance to the planet that isn't absolutely predictable.

Seed the asteroid belts within the appropriate ranges with towed but unfired up ghost-rider FTL recon drones. Designed to launch and follow that enemy fleet in upon arrival. About the time they finish deploying pods, a certain percentage go 500M-Ton ker-blooey to take out said pods, and the rest to "light 'em up, buoys!". Thoughts?

Effectively a defensive deployment of Mistletoe. It could help if the enemy was relying on deeply stacking pods prior to their first launch.

It'd take a fair number of drones to cover the probably approaches; and the likely approach vector would change throughout the year; so you need to reposition drones if only covering the current likely approach. It might be better if the drones were launched from an out-system ring of LAC bases (such as were prematurely used at Zanzibar). That would mitigate some of the endurance concerns from leaving drones on standby floating around.

Jonathan_S wrote:

SharkHunter wrote:Here's an interesting thought though. Using the Sol system and some of the drawn diagrams of the Manticore system, etc. as prototypes... and an astral "fact".

In order to successfully attack and reach the orbitals of Sol, for example, to a certain extent you're not going to be able to get any force advantage based on surprise by coming in on the other side of the star system, etc. So most fleets and all SDM armed combatants come in at the minimum safe approach distance to the planet that isn't absolutely predictable.

Seed the asteroid belts within the appropriate ranges with towed but unfired up ghost-rider FTL recon drones. Designed to launch and follow that enemy fleet in upon arrival. About the time they finish deploying pods, a certain percentage go 500M-Ton ker-blooey to take out said pods, and the rest to "light 'em up, buoys!". Thoughts?

Effectively a defensive deployment of Mistletoe. It could help if the enemy was relying on deeply stacking pods prior to their first launch.

It'd take a fair number of drones to cover the probably approaches; and the likely approach vector would change throughout the year; so you need to reposition drones if only covering the current likely approach. It might be better if the drones were launched from an out-system ring of LAC bases (such as were prematurely used at Zanzibar). That would mitigate some of the endurance concerns from leaving drones on standby floating around.

You missed the "towed and unfired" part and the fact that the asteroid belt is both a disquise and perhaps something like a LAC base ring. Idea being that you're not covering all that much of the star system, you're jus periodically and very quietly moving the array of drones to a new guard position with "x" degrees of the most likely approaches. That keeps the count requirements down and the sneaky deployment pattern way way up.

SharkHunter wrote:You missed the "towed and unfired" part and the fact that the asteroid belt is both a disquise and perhaps something like a LAC base ring. Idea being that you're not covering all that much of the star system, you're jus periodically and very quietly moving the array of drones to a new guard position with "x" degrees of the most likely approaches. That keeps the count requirements down and the sneaky deployment pattern way way up.

i saw that. But even without firing up their onboard reactors there's maintenance requirements on the drones. Heck sitting docked in their hangers there are routine maintenance requirements.

Since most systems you'd be willing to seriously defend from pod layers would have an outer LAC base ring I just though you could do two birds with one stone and leave the drones where they're easy to maintain.

SharkHunter wrote:Seed the asteroid belts within the appropriate ranges with towed but unfired up ghost-rider FTL recon drones. Designed to launch and follow that enemy fleet in upon arrival. About the time they finish deploying pods, a certain percentage go 500M-Ton ker-blooey to take out said pods, and the rest to "light 'em up, buoys!". Thoughts?

In short, you're wasting money.

Consider that no attacker is obligated to actually pass through the belt on the way to the planet and (in Sol's case) has a 21 lightminute diameter sphere on which he can enter realspace, the chance that a useful number of drones will be in range of the attacker is minuscule.