# Why are certain spaceships capable of warp at a moment's notice while others require some preparations?

After seeing an advert on my holo-watch about the latest fleet of interstellar spaceships capable of going into warp at the press of a button, I was both amazed and dumbfounded by it

Conventional warp requires onboard computer to sync with at least three deep space networks and plot the coordinates which can take anywhere upward of 72 hours which is the limitation of data transfer and Moore's law, I am wondering why these new Dreadnought Class spaceships are able to go into warp 2 (≤4c) at the press of a button and yet the safety records are nothing short of spectacular no accident so far including the testing phases?

I doubt you can simply download the old charts and extrapolate everything because a computer model still has its limitation, and a slight miscalculation could prove deadly!

• "...latest fleet of commercial interstellar spaceships..." vs "...new Dreadnought Class spaceships..." Be specific - military or civilian, or both. Feb 27 at 15:06
• @JustinThymetheSecond: I edited out the commercial and hopefully it does not invalid your answer ;D Feb 27 at 16:33
• @user6760 Some of them still run Windows(TM) - so they need to prepare before they do Feb 27 at 20:31
• @Aganju Warp is ready in 3 hours ... 72 hours ... 32727 years ... 10seconds ... warp failed due to an unexpected error, press ok to cancel and cancel to continue Feb 27 at 20:35
• Tangental sidenote: Space is full 3d, so probably wants 4 or 5 deep space networks to sync with, rather than the 3 we use for Earth-surface gps. Feb 28 at 20:24

The Dreadnoughts are taking advantage of a breakthrough in FTL communication technology, and they continue to sync with the networks and plot the coordinates while already at warp.

For this to work, we assume:

• The ship does not need the whole trajectory calculated to safely begin the jump, but does need it to safely complete the jump.
• Calculating the local (nearby) warp trajectory would yield results faster than calculating the destination (farthest point) on the warp trajectory.
• (Plot point) Communicating with the space networks while at warp represents an advance in technology that would "amaze and dumbfound" those who were not already aware of its development.

So ship A, which cannot sync while at warp, needs to sync-and-plot both the beginning of its trajectory (completed quickly, perhaps near instantaneously) and also every other part of its trajectory (a lot of time, especially as the distance increases) before it can even begin its jump.

While ship B, which can sync while at warp, can perhaps be constantly in sync with the local space networks and keep ready calculations for beginning a jump in any direction, and then maintains sync and refines its trajectory and plots destination coordinates as it goes.

• What would happen in case of loss-of-communication during warp, for example, due to a damaged antennae array?
– Mast
Feb 28 at 8:04
• @Mast Plot would happen, I would guess. Feb 28 at 8:22
• If this ship goes below warp 8 we're all dead! Feb 28 at 11:05
• That said, it might also stand to reason that the Dreadnoughts need to have correctly calculated every point on their trajectory before they reach it...in which case, it's simply a matter of automatically dropping out of warp if you run out of pre-calculated trajectory. You could hand-wave it either way; depends on the OPs preferences/intentions...
– Qami
Feb 28 at 14:13
• Note: if ship B can sync while at warp, it doesn't need to keep ready calculations. If it knows the destination is "vaguely left", it can just warp "vaguely left", and then sync details on the way. It'll have a suboptimal start to its route (plot point!), but given a 72h headstart, it's worth it. Feb 28 at 20:27

The older Warp drives are ballistic. Like a bullet fired from a gun.
You have to set the direction and impulse at the beginning, and thus need to have your settings exactly right, or you miss your destination.

The new Warp drive is dynamically steerable, like a missile.
You can continually refine your orientation, so all you need to get started is the general direction towards your goal. You will have time to refine your aim further along the journey.

• This is great! It's similar in essence to my answer, but provides a different foundation (ability to steer for yours, vs. for mine--shall we say--ability to look out the window)
– Qami
Feb 27 at 12:53
• My stunt would have been to warp about 3 million km and then begin calculations. If I really needed to get clear by a long ways, I'd warp in the Z axis out of the plane of the galaxy. The idea is when you're targeting deep space, you don't need to be all that precise. Mar 1 at 17:10

### It still takes 72 hours, a tiny tweak in the order of events makes it seem instant.

After a few decades of CEOs cutting talent from the engineering department and using the savings to pay their own bonuses, there was no chance the company could improve on their design. The ships still need 72 hours to calculate trajectories, warm up the engines, and accelerate within subspace. But with market share slipping and no money to pay for actual talent, they needed to hack something together, and fast.

An unpaid intern hacked at the code and found a way to open the FTL bubble to subspace at a moments notice using the default safe settings, the ship enters subspace and then sits there idly while finishing the rest of the setup and calculations, taking 72 hours.

The unpaid intern then modified the data feed from the FTL drive to the bridge such that it reports it's travelling at about 3.9c even though it's still warming up. By the time the engine is actually ready to accelerate (72 hours later), the ship is only 0.03 light years behind where it should be, which slowly closes over the length of the journey as it does 4c when reporting it's doing about 3.9c.

Combined with a minimum safe jump distance (must jump minimum of 0.3 light years - like flicking a light bulb on and off quickly it's bad to do short jumps), that subspace has no stars so is pitch black so you can't see stuff swooshing, the inertial dampeners suppressing the G forces, and the lightshow of it disappearing into subspace immediately when you press the jump button, everyone totally believes the company had a breakthrough innovation.

• Ingenious, and when I think of the sort of things certain car manufacturers have gotten up-to, "typical". Feb 27 at 15:32
• Hey, stop leaking our Unpaid Intern secrets! :) Feb 27 at 20:36
• @NotThatGuy: If "normal warp" takes a month or even a couple weeks to get to the next star, then "faking" 72 hours might not be noticeable. I think "warp" just means fast, rather than seconds/instant. Feb 28 at 20:30
• I work in transport safety, and I can tell you faking instrument data is a great way to enable accidents and sabotage. Especially if you give the responsibility to unpaid interns. But I suppose you have a window in time between rollout and getting sued into oblivion where it can happen. Mar 1 at 7:27
• @NotThatGuy The OP said so. Interstellar ships travelling at 4c. I think you're mixing up warp and fold - warp simply means changing the geometry of spacetime to achieve superluminous speeds (or just avoiding having to accelerate); folding is usually instant after a charge-up period ("bring the two points together and then jump when they're right next to each other"). Most FTL in sci-fi is anything but instant. Mar 1 at 13:39

It's all just marketing BS. What they fail to mention is that you can only jump straight to warp if your "destination" is nearby (like, a few light-minutes nearby).

As you surely know, the drive safety interlocks won't let you engage the drive unless you've plotted your route completely and know you aren't going to run into anything. Well, some egghead got the bright idea to remove the minimum distance limiter to allow short hops that don't need to collate data from far away (or maybe the new drives permit much shorter cycle times than were previously possible).

The thing is... for your average traveler, such short hops are basically useless. In other words, they're hoping you don't read the fine print.

But you mentioned these are Dreadnought Class ships. Military ships. Well, as you surely also know, navies often have different priorities than civilians. Being able to change position quickly is extremely valuable for a ship in combat, but not so useful for ships that just need to get from A to B. (Oh, and it turns out the "new" drives also need to be overhauled after only a third of the drive hours. Again, for naval ships, the added flexibility is totally worth the extra costs, but don't expect to see these drives coming to your typical passenger liners or cargo haulers any time soon.)

• I like this idea; alternatively, as these are military vessels: if there was some kind of break through (or just incrementally passing a milestone) in battery/heatsink ability, these military ships might be able to "daisy chain" these jumps together. Feb 27 at 20:14
• The huge advantage, militarily, is that if you can hop light-minutes away, that gives you exactly the minutes you need to plot for a longer jump. To your foes, it's indistinguishable from an immediate long-jump. The "trick" is not so much marketing hype, as a military secret to prevent the foe from figuring out the same trick and send them down the wrong research rabbithole. Feb 28 at 17:11
• @DewiMorgan, exactly; it's a move to buy time in an engagement. Depending on whether you can use the drive in-system (although that would tend to make it useful to civilians, also, for intra-system travel), maybe even a way to dodge incoming missiles. Feb 28 at 17:21
• It's a neat idea, but I'm not sure it holds up well. If it doesn't work intra-system, then it effectively doesn't work at all, since you'd have to spend hours, days, or even longer traveling at sublight speeds, just traveling between warp points and non-empty space. If it does work intra-system, then you've just opened up daily commutes between planets, which seems like a pretty big deal for civilians. I suppose you could drop the distance down to milli-light-seconds, with a long enough wait between jumps have it be a rough usefulness equivalent to supersonic jets. Mar 1 at 19:57
• I'm thinking Picard Maneuver... Mar 2 at 12:23

Bureaucracy.

The commercial ships have to file a flight plan, get permission from the destination, get clearance from the departing system, sign waivers in triplicate and in physical form, to alleviate the system from liability, pass all inspections and get customs clearances, pass all quarantine conditions, make sure all payments are cleared by the financial institutions, satisfy all immigration and visa requirements, and generally go through all of the hoops, and pay tribute to the bureaucracy gods.

The dreadnaught, being under the command of the Supreme Authority, has a universal diplomatic immunity and has clearance to go anywhere at will, no paperwork required.

I am reminded of that scene from Shrek, where the poor 'greeter' at the castle gate has to go back and forth, zig zagging through the barricades and ropes that control the crowd flow queue, and Shrek just barrels through all the ropes and goes straight in.

• Although that scene is less of a "surpreme authority" and more of a rogue-ish I-don't-care moment. Mar 4 at 8:00

The upgrade uses Laplace's Demon, and a lot of memory.

https://en.wikipedia.org/wiki/Laplace%27s_demon

According to determinism, if someone (the demon) knows the precise location and momentum of every atom in the universe, their past and future values for any given time are entailed; they can be calculated from the laws of classical mechanics.[2]

The package includes a plan to warp from (quantized) anywhere to anywhere else, calculated in advance. The upgrade is a memory upgrade; with quantum memory storage as proton spin, there is a near infinite reservoir of calculations ready. These are the same calculations that the current model uses but all done in advance and stored.

The issue then is retrieval. The system keeps track of the ships position and keeps ready only calculations relevant to that position for the touch of a button. If you wanted calculations relevant for points X and Y distant from your own you can retrieve those also but you will need to push several other buttons.

The system has memory to spare and also comes with every movie or video ever made and every song ever recorded, and some books.

• Not to forget every movie that ever will be made... Mar 2 at 12:25
• Laws of classical mechanics constitute a formal system, and because of this, there will be solutions to these wave equations inaccessible to the demon. via Godel. Even infinite memory does not guarantee that solutions to all the wave functions can be found. Knowing the momentum means that the position is a wave function over all of space. Laplace's demon will not be able to calculate courses in this manner. Sep 18 at 3:32

You know, warp engines have strange effects on the fabric of space-time, and we can exploit them

When the dreadnought officer presses the button, the flight control center starts all the calculations or - in case of departure from an uncolonized system - the dreadnought releases a small probe, which collects and computes all the data necessary for the jump.

Newer warp engines allow nonlinear jumps through both space and (to a limited extent) time: in this case the dreadnought perform the latter and jumps 72 hours later at the same spatial coordinates, when it collects the results of the calculations, either from its probe or from the data center.
Since the jump in time is inherently unstable (you know, it always happens when you tinker with entropy and potential energy of the time flux), the ship can stay in this 72-hours future just for a few fractions of second before coming back, but they are sufficient since there is enough bandwidth to download the results and the center/probe knows in advance when and where the ship will be, so they already know when and where to broadcast the data.

As soon as the ship comes back in its present, some instant after (according to how the passengers perceive the time), it has all the information necessary to perform the true jump through space and reach its destination.

• This seems like it has some potential to explain why it's so safe, too. At least for short distance travel (anything reachable within 72 hours of warp travel) the data center/probe essentially gets to watch the ship make the journey and can see any possible unexpected obstacles along the way, giving it the opportunity to route around those. Mar 1 at 20:11

It's MUCH more expensive, but the expense is warranted by being a warship.

## A new algorithm computes destinations all the time

First, they have a larger auxiliary generator and a bank of computers that does nothing but syncing and plotting all the time, in case you need it. The only breakthrough is a new algorithm that uses the data they are collecting to produce a bunch of intermediate data, which is used to develop the final calculation in a second or two.

Not mentioned is the cost: destinations are now slightly less accurate (larger CEP) so you are no longer able to jump into a precise orbit location, you must jump into a conservative orbit and reposition once you are in the ballpark.

That and the fuel, spare parts, and heat disposal needed to keep those computers working.

## The engines are on hot standby at all times

The engines are also built a great deal beefier. Part of that 72 hours was the warmup of the physical engines. Not these; they are ruggedized to be kept in a spun-up state all the time.

Of course, this has a number of tradeoffs: Much higher manufacture costs, more frequent and longer maintenance downtime (drydock), and of course, stupendously higher fuel costs. "Fortunately" they have plenty of spaces to store fuel; because it threw a monkey-wrench in ship design.

Previously, a bunch of areas on the ship were only irradiated during warping. You could use those spaces for galleys, recreation, commissary, and other places sailors will not be when you are at general quarters for warping, including the best feature of those ships: the surplus of space gave lots of space for crew quarters. Now, those areas are irradiated continuously, so no-go. On the upside, you don't need to muster to general quarters for warping anymore (to evacuate those areas)... you can just do it.

You'll have to figure out whether to build the new ships bigger, or just have a stark downgrade in crew accommodations.

The warp requires setting up rather precise location around the target star to match your velocity vector with the gravitational field at the destination. For this, you need extraordinary precision of your location, something like $$10^{-5}$$ per distance error is already too much (i.e. within an AU or so per lightyear). Now, you use GPS (Galactic positioning system), unfortunately, it first needs to get a fix by listening to several signal sources for some time, to download the galactic ephemerides and then calculate the intersection of spheres around those sources. Takes some day, it can be shortened if you get an accurate disance to a known nearby pulsar or such.

However, this is for civilian use. The GPS contains other, encrypted signal, with much better precision and much shorter time to get a fix. This is strictly for the military and the encryption keys are a closely guarded secret. The Dreadnoughts, being military ships, have the decryption keys already built in into their positioning units firmware.

# It was a lie

Sure, it used to take 72 hours to sync up and get the flight data. 100 years ago. But over time improvements in ship computers, additional satellites, improvements in encoding, all of those have chipped away at the time it takes to get the data. Until as long as 20 years ago plotting FTL took less than a minute.

But that didn't suit the people in charge. Requiring a three day planning window was much more useful. It is harder to smuggle, or plan an insurrection if you have to connect to the network and announce where you are going three days in advance.

What changed? Well, that could depend on the needs of your story. A new, more honest group came into power. The ship manufacturers got blackmail material. Or they banded together to tell the government they wouldn't play this game anymore. Maybe they were fooled too, but finally figured it out. Whatever the case, in order to prevent unrest, rather than reveal the truth, they just claim that this new instantaneous version of FTL plotting is some incredible new tech.

It's not like most of the unwashed masses understand interstellar networking, more or less FTL drive.

# It was a (different) lie

It is true, up until these new Dreadnought were developed, it to 72 hours to prepare to go to FTL. But the networks and course plotting didn't have anything to do with it. That was just something they told the people. Something simple they could understand. Or something they wouldn't complain about.

Maybe it took that long to build up spatial distortion in the drive (which needed to be done slowly and steadily and released at exactly the right time, or it could cause spatial tears or other environment damage/destruction). Maybe it took that long to clear the subspace whales out of the interstellar travel lanes. Maybe it took that long to back up the passengers brains before their bodies were incinerated by hyperspace stresses (said brains being downloaded into cloned bodies on arrival).

Whatever it used to be, that has been improved or solved. So they claim that the networking issue has been solved. Because the people bought that lie in the first place.

• It was a different different lie: thedailywtf.com/articles/The-Speedup-Loop Mar 1 at 18:06
• Seriously, governments lie to us to cover up and supress technological advancements? Here I thought they just did that through stringent regulations and obsolete standards. "Regulation 43-mt-017 specifically prohibits that." And so we were stuck with NTSC for decades past it's best-before date. Mar 4 at 17:30

It's an ongoing lie.

The new tech is fake. All demonstrations were scripted step-by-step. The ships absolutely knew where to go 72 hours before, that's why they could go there.

Any outsider trying to buy the new ships will be refused sale or stalled for as long as possible.

Possible reasons:

a) It's a deterrent against an enemy who could attack anywhere. That enemy will be less inclined to attack once convinced that a large fleet could converge wherever at the drop of a hat. Convincing everyone else is just collateral damage.

b) The ship's owners are itching to attack a place they weren't supposed to know exists, but they're trying to protect the intelligence source which revealed it. If they attack now, their source is busted. They have a plausible avenue to publicly leak the location, covering their previous knowledge and their source. However, the target will know that they know, and will proceed to evacuate. They have a fleet on standby who will attack immediately when the leak comes. The new tech is a cover for how they can attack as soon as the information comes out.

# Precalculation

I'm assuming "warp" is instantaneous travel, not mere "light speed or a couple times faster". Otherwise, saving 3 days just doesn't change much on a galactic scale.

If something takes 72 hours to calculate, then it really makes sense to start calculating it 72 hours in advance.

But if you need to be able to warp anywhere in the galaxy, then there's an infinite number of possible routes to precalculate. You simply can't calculate an infinite number of them ahead of time, let alone then update those models in realtime to handle the celestial mechanics as things in the galaxy move.

But what you can do, if you have a powerful enough military computer, is subdivide the galaxy into "nodes" and plot a network of routes from node to node. That reduces the calculation that you need to do from "where you are to any destination in the galaxy", down to "any destination in the galaxy, from its nearest node".

Assuming calculation time is linear with distance, then in a galaxy 107,000 lightyears across that normally takes an average of 72 hours to calculate, you'd need to plot a node only roughly every 24.5 lightyears, to get your average calculation time down from 72 hours to one minute.

You don't have to spread them evenly, either: you can cluster them where stars or population or likely military targets are denser, which should reduce that minute down to even fewer seconds in the majority of cases. No point plotting many navigation nodes between the spiral arms, for example.

As well as needing crazy computing power, running constantly to keep the numbers precalculated, another possible disadvantage arises if warp fuel is proportional to the distance warped. You still need to continuously calculate the routes between all those nodes, and you likely lack processing power to calculate all possible routes between all nodes: at an absolute minimum you need to connect each one to the next. In the 107 x 107 x 1 kilolightyear galaxy, that means around 778 million nodes, so 778 million jump calculations needing to be continuously updated. In fact, if you arrange them into a binary tree, you use the same number of links (root node gets 2 connections, all "branch" nodes get 3 connections, all "leaf" nodes get 1 connection, so it works out about the same 778M links), and the maximum number of hops you need to get from one leaf node to another is just 60... but that's still 59 more "hops" than the normal direct route, so while it'll still be near-instant because warp-speed, it'll be very indirect and inefficient in terms of fuel.

For the military in an emergency, that just makes sense: when you need to get somewhere NOW, and not in three days, conserving resources is not a priority. You still CAN take three days to calculate the most efficient path, but when you need to, you have the option to warp 60 times the distance, burning 60 times the fuel, in order to arrive in seconds instead of days.

That is a tradeoff that will save lives!

Except, of course, war is war, and it will not save any lives. It will just change the nature of space warfare. Before this innovation, an attacker could attack a remote base with a fair amount of impunity, knowing that even if a warp-space SOS were sent out, by the time a response had come, some 3 days would have passed. So they could attack, plot a trajectory out, and be either gone or almost ready to leave when the reinforcements arrived.

Now, though, essentially as soon as a large force turns up to any location, the reinforcements will arrive within a minute. So large-force warfare to wipe out a base needs to be replaced with small-force guerilla warfare. Single "fire ships", drones or suicide ships attacking a base. Ships posing as legitimate freighters calculating their trajectories first, then launching missiles just before they warp out. Bioterrorism. Chemical warfare. Launching large black masses at bases from a large enough distance at high speed.

And so on.

• If you were a commercial logistics firm, you would have standard shipping lanes already well-defined. Mar 4 at 17:31

Extrapolating from modern airlines: Older ships needed to run calculations to find the route that costs the least fuel to get there, because there's lots of competition and lifting fuel into the ship is expensive, so every penny saved in fuel is a huge increase in profits. Ships have historically taken longer/slower routes than needed, because the route used gravity assists, and therefore less fuel.

A new breakthrough (mining? storage? fuel type? etc) allows the use of a fuel that is cheap and or high density to be used instead. (more dense, therefore less space for fuel, therefore more space for customers). Now that expenses are driven by customer count/comfort rather than how much fuel is used, ships now prioritize the fastest route instead, which is far easier and faster to calculate, and they can be slightly lazier about it, since fuel savings no longer outweighs customer convenience.

• Variant on the extrapolation: The conventional drives are comparable to ERTOPS-60, an older reliability spec where a twin-engine jet aircraft must at all times be able to safely land within 60 minutes on one engine. The new military drive is comparable to ERTOPS-180, a very strict reliability spec allowing a one-engine flight time of 180 minutes. So the new military drive has substantially higher performance and reliability standards than the conventional models, and so can travel a more "direct" route (with respect to warp) than the conventional models. Mar 1 at 21:09

# It's a false flag to hide cloaking tech

The military recently launched ground breaking cloaking tech.

It's primary use is to gather intel. To prevent the enemy knowing that you are finding out about their buildup of an amadada before the ships have even gathered (due to you cloaked spy drones), you make it look like you are only findout out as it begins, but that you are able to react super fast, because of the supposedly instantly entering warp. but in reality, you have had almost a week to prepare.

Secondly, it hides that you are using cloaking to retreat from battle. If they knew your mothership was cloaking and hiding behind the moon, then they would engage additional sensing measures to try and defeat cloaking. But if they think you are now lightyears away they give up.

Thirdly, it hides your reinforcements. They think that they have you out-numbered, but then you are warping in reinforcements at zero notice, then they are going to be pretty catious. But what is actually happenning (in the times you are faking this) is that your fleet is 90% cloaked.

The fakes are good. Warp signatures and all, they put work into this. One part of that is the adverts.

## It doesn't actually take 72 hours (sorta)

Most of the normal 72 hours isn't spent getting the ship ready for the jump, but rather getting the jump ready for the ship. This means that we can get rid of a large amount of that time if the jump is closer to being ready all the time.

Most older ships would calculate hundreds of routes and then find the fastest one to the destination, however this takes a long time to do and contributes to a large amount of the time spent. The new ship doesn't need to do that. Instead it has a preset of a few thousand pre calculated fastest paths in places commonly traveled. It only needs to calculate a route to the startpoint and one from the endpoint to the destination and then uses the pre calculated routes.

These ships also eliminate the need for all the security precautions. Normal ships have to verify each course they take with multiple datacenters, then have to request access to each used interstellar "highway", then governments of each system they get near and finally verify with hundreds of ships so that they wont crash into each other. This company made it so all you have to do is verify with their own central server, making the process take a fraction of the time.

The safety record is impeccable as when the dreadnought makes a mistake and drops out of warp in the wrong place (another ship, large asteroid, small planet etc) its the other object that gets obliterated. Thanks to some new super shields and a lot of armor plating there is nothing a dreadnought can hit which isn't going to have a very bad day while the dreadnought keeps on going.

So far no one has tried seeing whats happens if a dreadnought hits another dreadnought at warp speed to see which survives.

## First you jump, after it's up to another engine

These big Dreadnoughts are... big. Vast even. They could house more than one FTL engine. So it's really a simple question of economics.

Small, non military ships contain only one FTL engine, with no steering capacity. You can jump, you can break, but this is all. You will need to be very careful before starting the jump.

Military ships have another set of priorities. One of them is "get hell out of here, now!" type of priority. First you jump and then you use another set of engines, still in the "cold" stage, to work out where and when to stop.

And you need very big machines to have a meaningful and precise impact to steer a thing as big as a Dreadnought in ludicrous speeds.

There are possible parallels here to the shift from steam to diesel power in shipping, which began to occur around WW2 era (though most ships built for the war itself used steam plant). One notable example of a large, diesel-powered warship of that era was the Graf Spee.

A diesel engine can be started and/or throttled up in a matter of a few seconds; a minute at most for exceptionally large engines, or if actively trying to avoid thermal stresses to reduce maintenance needs.

A steam engine or turbine, however, requires that enough boilers have first been lit off and brought up to pressure to produce enough steam for the power ordered. Lighting off a boiler from cold can take literally hours. You preferably want to do that in advance of need, rather than having to delay any orders for high power manoeuvring. On the other hand, keeping more boilers alight than necessary is wasteful of fuel.

An entry in one WW2 submarine's log illustrates how this could be taken advantage of in combat:

A Japanese convoy was sighted, escorted by a destroyer. Japanese merchants were a primary target for USN submarines, to sever the logistical supply chain that kept every part of the Japanese military in operation. This convoy was sailing near the coast in shallow water, probably trying to make submarine attacks more difficult since a favourite escape tactic was to dive deeper than Japanese sonar could search.

The typical IJN destroyer had three boilers; with all three burning it could make well over 30kt in a calm sea, but to escort slow merchant ships it would light only one, limiting it to about 18kt. This would be fast enough to keep up with a Type VII or Type IX on the surface, but not a USN "fleet boat". Judging that was the case, the submarine closed in for the kill under cover of darkness. The destroyer would be a difficult target to hit, so the strike was aimed squarely at the convoy itself.

The first thing the Japanese knew about it was when a ship exploded. Thus alerted, searchlights were turned on and the submarine soon located. But it had already turned tail and run its engines up to - and beyond - maximum rated power, making for deep water at about 24kt. The destroyer followed, but soon found itself falling out of gun range, and as the sun rose, could only watch as the submarine disappeared over the horizon. The second and third boilers then came online, and the destroyer accelerated - only to see the submarine reach the edge of the continental shelf and submerge, out of reach.

So how does that translate into warp drives?

Well for a start, the fact is that stars, rocks and balls of gas are very predictable in their motions. Even a very cheap computer by today's standards could calculate the position and trajectory of every charted natural object in a ten-lightyear radius in a fraction of a second. I don't buy any argument that computing power is the limiting factor here.

So why the heck do you need to communicate with "several deep space networks"? Probably to file a flight plan to prove that your course doesn't intersect any other spacecraft's course. Spacecraft are objects that you can't reliably predict the positions of from charts loaded at the last docking. Space is pretty big, so the chances of a hastily chosen flight plan being accepted are high but the communication delays are potentially long.

Next, consider that 4c is very slow by the standards of interstellar travel. At that speed, starting from Earth, you have two whole minutes to figure out where the Sun is and change course to avoid running into it - and more than ten minutes to similarly avoid Jupiter. You don't need to start running calculations for anything in Alpha Centauri for the next year, even if you started out in that general direction. By then, one assumes you have run out of patience and figured out how to safely engage some higher speed.

But this low speed, and the presumably large size of a dreadnought-type starship, does make a couple of things plausible that would be difficult for a smaller ship to match:

If a warp drive takes time to physically spool up - even on the order of a few minutes - then a small one could be kept on hot-standby to eliminate most of that delay, and it would make sense for it to have less speed capability than the full-sized main drive. This would be less of a burden for a very large ship than a smaller one, due to the fuel reserves carried.

Also, due to a dreadnought's size and comparative rarity, it could keep a permanent reservation in the flight-planning system of several dozen relatively short and slow warp trajectories that radiate from its actual current position. At 12 light-days long, these would be enough to clear a stellar system in a relatively unpredictable direction, while waiting for the normal flight-planning negotiation to complete for a full-speed warp.

## Computational Load is not an Effective Limitation

I don't think the need to wait for a computation to finish will be believable to your readers as a reason why the old ships need 72 hours to get ready to jump to warp speed. If our world is any guide, computers are likely be be cheap and easily replaced. A ship owner who can cut three days off each trip (six if it is a two-way trip) just by replacing the computers on the bridge will jump at the chance.

Go with a physical aspect of the technology instead, something expensive, bulky and hard to replace. To use a car analogy, replacing the radio is easy, people do it all the time. Converting a gasoline car to electric is a major undertaking and tends to produce mediocre results.

## Possible Physical Constraints

As the author you could decide that the old warp engine technology requires some kind of a warm up or pre-charge stage which the new technology does not. Maybe you have to charge giant capacitors because you need a huge pulse of power to break into warp. (Think of those big camera flashes which take a few seconds to charge and then make a popping noise as the built-up energy is released.) Of course, you need a reason why the capacitors can't be kept charged all the time. That's easy. Real capacitors lose charge over time due to leakage due to limitations of the materials of which they are constructed. If your capacitors lost say 20% of their charge per day, keeping them charged up and ready to go all the time might not be practical.

Another possibility is that the warp engines on the old ships will not work from a standstill. The old ships need to have reaction drives to get up to a speed at which they can engage the warp engines and jump. The new ships use a different kind of warp drive which can be engaged at much lower speeds. Retrofitting an old ship with the new engines and all their support pumps, controllers, cooling systems and what have you will surely cost more than the old ship is worth.

## Effect of Improved Capacitor Technology

I think I would go with the warp jump capacitors. To get to the required capacity the designers of the old ships had to compromise and accept a capacitor technology with a horrible leakage rate. Charging them for a jump is like filling a bucket with a hole at the bottom at a faucet. It takes a long time, you need to open the tap wide, and once its full you need to run and use it before it all drains out. Then all you need to make the new ships ready to jump at a moment's notice is a new low-leakage capacitor technology so they can wait charged and ready. Make a set of new capacitors cost close to what the old ships are worth and most of them will not be retrofitted.

Just remember that if you go with this solution, even the new ships will not be able to make a second jump a few minutes after the first. If filling a leaky-bucket capacitor takes three days, filling a modern low-leakage capacitor ought to take at least a day. You as the author can tweak the facts to make somewhat shorter, you can make the old capacitors even more ridiculously leaky and you can give the new ships significantly more powerful chargers, but with these premises you are not going to be able to justify a recharge time for the new ship which is not a significant part of a day. Hopefully they can charge their capacitors on the way to their destination.

## Interesting Story Possibilities

Even if retrofitting old ships does not make good economic sense, some people will do it anyway. Perhaps they are rich or eccentric or both. If an old ship is famous, that might justify the cost of a retrofit. Spies with the resources of a government at their disposal might retrofit an old ship as part of a subterfuge. In that case they would presumably simulate the old mode of operation most of the time.

Jumping out of the plane

The trick is that instead of calculating a single jump through the galactic plane, and having to calculate the gravitational effect of every star along the way, the new ships do one jump out of the plane, one jump across it, and another back in.

The jump out is almost instantaneous because it’s the reverse of when you previously jumped in, with some amount of error due to orbiting in the meantime, but since you’re jumping toward the intergalactic void, who cares if you pop out a few light years from where you expected? There’s nothing out there to hit!

The second jump across the disc still takes a while to calculate, but it’s easier since all the gravity is in one direction and roughly uniform, there’s still nothing to hit so the error doesn’t matter much, and you have all the time you need since nobody else would know where to even look for you. Heck, even you aren’t all that sure of exactly where the first jump was going to put you until you got there!

The third jump back into the disc would be the hardest, but again, nobody (even you) knows where exactly the second jump will leave you, and you have the entire time of crossing the disc to calculate a rough solution that just needs to be refined once you get there.

No civilian operator would even consider this because of how much fuel it wastes, but it provides an undeniable military advantage (particularly the quick escape part) if you’re willing to pay the cost. That’s also why these ships need to be so large.

Broadly, blending inertial dampening with the way steam-catapults get carrier aircraft up to speed so much more quickly than the same planes leave the ground.

Beyond that, should you not be asking he who wrote the rule-book, particularly if it says conventional warp can take upward of 72 hours to plot? How would that drive hold everything still while its gears chug through miscalculations that might prove deadly?

Further, consider how almost no-one in any Star Trek iteration objects to "explanations" such as "that's classified" or "we don't have time for that" or "you wouldn't understand"?