Range Limits of Jumpships

[Hellraiser]

I'm not familiar with the rules for making a KF Jump, but, I'm wondering how hard that 30LY limit is?

For example, if I'm wanting to go from Wyatt to Denebola, that is 30.2 LY per Sarna.

So is that a Flat out, NO, you can't do that?

You MUST jump to a half way point?

OR

Is there some sort of penalty to the navigator calculations roll?

Is it possible to make that jump at all & if it is, how much harder is it?

[AlphaMirage]

Impossible, full stop....

Why? KF Physics.

Caveat the Word of Blake did it, once, and burned out the jump cores in the process.

It is entirely possible there is a viable star between those two points you can jump to or you can just float in space and recharge with your reactor. Neither of which are particularly difficult and likely banal to experienced spacers.

Just tell COMSTAR beforehand if you suffer a jump drive malfunction and don't report in a few weeks.

[Hellraiser]

It is entirely possible there is a viable star between those two points you can jump to or you can just float in space and recharge with your reactor. Neither of which are particularly difficult and likely banal to experienced spacers.

I was just trying to figure out a better path on a map.

If my total distance is say 57 LY that is in theory 2 jumps.

But my "Route" to populated planets leaves me w/ jump points at the 25 & 31ish points it means I'm having to make a small 3rd jump or jump to deep space instead of a standard world.   Annoying is all :(

I was hoping it was something like 30 is the baseline, but you can risk burn out/miss jump for an extra +1 on the dice roll per extra 1 LY.
Similar to fast charging a KF drive.

[Frabby]

It’s not a hard limit, but not a baseline either.

There are jumps in canon that go slightly over the 30 ly limit (up to 32 iirc).
Think of the 30 ly limit as a game rule, like the 3 hexes (90 meter) range of machine guns. The bullets don’t drop to the ground after 91 meters but under game rules they don’t reach beyond 3 hexes, period.

I discussed jump ranges in this post a while back.

[Hellraiser]

Interesting stuff.

I do like the notes about some authors having JS move just over 30LY for certain jumps.

The Luthien/Wolcott one is obviously way off, but the GDL ones are close enough to be doable IMHO w/ some sort of penalty.

[Cannonshop]

Interesting stuff.

I do like the notes about some authors having JS move just over 30LY for certain jumps.

The Luthien/Wolcott one is obviously way off, but the GDL ones are close enough to be doable IMHO w/ some sort of penalty.

To be fair, the "maps" with "Scale" are, in terms of the game's history, relatively newish, often have imperfections and flaws that get corrected in subsequent printings, and aren't necessarily in the hands of a contracted author when he's writing...or, they get forgotten because the Plot has to go a certain way and too much delay corncobs the flow of the book or story.  (The tension collapses if the villain, protagonist, or villain protagonist is going to be arriving far too late to challenge their nemesis, because he's done his business and got gone while they had to fart around in empty systems for three chapters while said nemesis is doing their business...)

Speed of Plot is very much a factor in this here genre, and some authors just don't like doing that much math and/or geometry.

[RifleMech]

Impossible, full stop....

Why? KF Physics.

Caveat the Word of Blake did it, once, and burned out the jump cores in the process.

It is entirely possible there is a viable star between those two points you can jump to or you can just float in space and recharge with your reactor. Neither of which are particularly difficult and likely banal to experienced spacers.

Just tell COMSTAR beforehand if you suffer a jump drive malfunction and don't report in a few weeks.

There was one group that had a jumpdrive that could jump further than standard, but not as far as WoB, without burning itself out. I don't remember who had it or what sourcebook the rules are in though.

Also primitive jumpships made shorter jumps. The distance increased over time uo to 30 LY. It'd just be time, and speed of plot, before jumps start increasing again.

[AlphaMirage]

Interconnectedness Unlimited Super-Jump Drive on the Lucretia is not quite canon rumor but either way they are one offs that add flavor to the world not the norm.

Maybe it worked, maybe it didn't,

but they caused a lot of damage to the New Syrtis Yards along the way.

[Hellraiser]

The interesting thing that I've been seeing as I researched this is that most texts point out that the "theoretical limit" of a KF Jump with current technology is "around 30LY".

Words like theoretical & around make me think its not some hard line max where an inch more won't work.

There a flat out exceptions as noted.
Primitive KF Tech was variable in the rules from 1-29 LY with cannon examples being 15 & 20 IIRC.
The Manassas Drive was 40LY
The IU Drive was 50LY.
The WoB super drive was unlimited in theory but it blew out the drive so doing a jump beyond standard was a 1-way trip.

You also have misjumps that can port you through time or cause issues of 100+ LY jumps at a single time.

Point being, I'm thinking there should be some wiggle room in the rules for doing something like the 30.2LY jump I mentioned in the OP.

Like Frabby mentioned, MG bullets don't just stop at 90M hex range, we have the "Extreme" bracket of gunnery ranges that have a higher ToHit modifier.

[AlphaMirage]

I still like the inaccurate map explanation most. Nevertheless it is likely a dropped point of interest in the universe.

[Hellraiser]

So you are saying the Map is wrong & the author made no errors & something like Denebola to Wyatt is actually "under" 30.  (Or whatever the book example was?)


Or your saying the maps are right & the author just made an error that should be ignored?


I'm not in favor of ignoring the novels unless they are horridly mistaken like the Luthien/Wolcott jump which could have been retconned as the author leaving out several weeks of travel.

[AlphaMirage]

The 30.2 is actually 30 makes things much easier without retconning or further explaining a core concept of the BT universe. I'm fact it's more interesting if someone didn't keep their COMSTAR ASTRONAV subscription up to date.

[Hellraiser]

Rounding works for my example true, and I like that, but, one of the novel ones was more like 32.5 from that other thread.
Glengarry to Skye I think it was?

That is almost 10% more, which is why I think some sort of option like the shaving hours off of a recharge rule could be used to explain some of these minor limit issues.

It also just fixes some of the odd "routes" that your forced to do use.

I know Talon is one where your forced to go in the opposite direction to leave there for the rest of the FS/IS, but I've seen others where you end up having to do some crazy "half-loops to get somewhere because a world has nothing to one side of it on the map that is w/in the 30LY border.

[Daryk]

The only person you have to convince is your GM... if that's you, so much the easier. :)

[Cannonshop]

There are currently multiple ways to look at this problem, and a lot of it boils down to Randall's aphorism: "if it works for your  campaign, do it..."

[DevianID]

We know that the star charts are a bit wonky regardless, as they assume a flat plane, instead of a 3d one with z elevation.  So while the game rule is 30 LY hard stop, that is only because we have the benefit of digital maps now with precise measurements like 30.2.  The early writers clearly didnt have that, and whatever method they used likely had a degree of imprecision, such as trying to read a ruler.  But its ok for a writer to mess something like that up, and not ok for players to jump farther then 30 LY when using something like MekHQ--the program wont ever allow it, other then to just use GM mode to magically teleport you anywhere you want at the speed of plot.

As for actual ranges, I could speculate that the explorers in the early star league/terran alliance days stuck to systems not far off the vertical access as a safety protocol, like how they stuck to 30 light years.  If you only use systems on a fixed vertical slice, then you create traffic through that system as you expand outward.  This increases the chance that a marooned or struggling ship could get rescued.  If you start jumping more then 30 light years or to systems greatly off axis, your risk of misjump goes up and also you dont stop along the way to created traffic in the -inbetween- system.  It also would explain why dead-space recharges just arnt a thing... otherwise you could dead-space recharge and show up anywhere in the sphere without bothering with border systems... The clans, for example, could have just appeared on terra in the clan invasion without bothering to stop at a single planet along the way.

The taboo of 'further then 30 LY' or 'dead space' jumps, as well as the desire to be in a real system after each jump incase you need rescue, is apparently mighty powerful in battletech space operations.

[AlphaMirage]

There are canon examples where jumpships do dead space recharge or route through 'uninhabited' systems. As long as someone knows where you are going and can send for you if you go off schedule it's fine. The rules do not penalize this behavior.

Additionally there are plenty of dead worlds or outposts post war that might have a small caretaker population on an orbital or moon that isn't worthy of being recorded by COMSTAR any longer.

[Daryk]

You know... the "caretaker" population angle has some interesting possibilities... ;)

[RifleMech]

Interconnectedness Unlimited Super-Jump Drive on the Lucretia is not quite canon rumor but either way they are one offs that add flavor to the world not the norm.

Maybe it worked, maybe it didn't,

but they caused a lot of damage to the New Syrtis Yards along the way.

That's the group! Thanks :)

Wasn't that WoB that did the damage?  Either way, there are rules for longer range jumps.

The interesting thing that I've been seeing as I researched this is that most texts point out that the "theoretical limit" of a KF Jump with current technology is "around 30LY".

Words like theoretical & around make me think its not some hard line max where an inch more won't work.

There a flat out exceptions as noted.
Primitive KF Tech was variable in the rules from 1-29 LY with cannon examples being 15 & 20 IIRC.
The Manassas Drive was 40LY
The IU Drive was 50LY.
The WoB super drive was unlimited in theory but it blew out the drive so doing a jump beyond standard was a 1-way trip.

You also have misjumps that can port you through time or cause issues of 100+ LY jumps at a single time.

Point being, I'm thinking there should be some wiggle room in the rules for doing something like the 30.2LY jump I mentioned in the OP.

Like Frabby mentioned, MG bullets don't just stop at 90M hex range, we have the "Extreme" bracket of gunnery ranges that have a higher ToHit modifier.

Good list. :) 

[PuppyLikesLaserPointers]

Personally I view it as the safety line, rather than ruled by the god and the creator of the world as if it's an axiom. It's generally considered as safe distance, but I don't think that the precise maximum distance to not get an accident would be exactly 30 light year distance without even some hundreds of kilometers of difference. The exact safe distance would be also modified by the stars near of the jumpship and target(and maybe also the stars near of the course?).

Anyway, if you had an another system on 30.2 light year distance, then... well, they better think about to jump twice. Although it's only plus 0.2, but it's 0.2 LIGHT YEAR. I don't think that such unit would be easy to be ignored. It's not like moves 101km/h on the road with maximum speed of 100km/h. The distance over than 30 LY is around 12600 times of the distance between sun and earth. I don't say that every single jumpship cannot jump that much distance without an accident, but I bet that you don't want to commit suicide while spend ridiculous amount of money and life either. At least there would be some chance to do.

Still, if you are in emergency, it would be worth considering. It's not TOO far than the safety line, after all, so if your situation makes you to seriously consider such an option, then it can't be helped.

[Daryk]

If I jumped in a fifth of a LY short, I'd burn a little fuel on station keeping thrust to start moving toward the target while calling for HELP!

[DevianID]

I think this is a great point.  If a 30.2 light year jump incurs even a fraction of a bit more risk for a misjump due to range, when the 'advantage' of taking that risk is to skip waiting 1 week or less to recharge at a midway point... like 1 week is nothing.  A misjump is months or years worth of damage.

Jumps in battletech are crazy fast, in a light year per day rating, so the name of the game is safety not speed or distance.  Jumping 120 lightyears in a month with risky push the limits 30+ LY jumps, versus taking 90 light years with 4 shorter safer jumps, the 90 wins every time.  The amount of stuff within 90 light years is already stupendous, and if speed was really a factor you would use a command circuit or something.  Command circuits or space recharge stations are terrifyingly fast in a stellar sense.

[Hellraiser]

I don't disagree with you, and yet, we have rules for fast-charging a KF Drive, and that the same concept.
Sometimes time really IS of the essence.

This isn't about shipping lanes that I'm asking btw.
Its about moving troops for an assault/raid/relief mission.

Using my theoretical 57 LY in 2 jumps v/s 3 jumps scenario.
That is a full week delay on launching a raid or getting a relief force to the planet, etc etc.
Or heck, just escaping from the invasion force bearing down on you in the case of fast charge.

Now if that extra 1/5 of a LY is a 90% failure rate then clearly you don't do it.
But again, this is why I was asking what sort of rules there were.
In the same way you can shave off a few hours of charging, can you plot that jump a bit further.

Even the descriptions as I mentioned above are not HARD limits, they tend to say things like theoretical when talking about the limit.
Is there really a difference between a 29.99LY jump calculation v/s a 30.01LY calculation?  That is what I was wondering.
For that matter 15 v/s 29 LY.  Is the distance a matter of difficulty at all? 
What is the true "limiting factor" that gave us 15LY proto-drives v/s 30LY current drives v/s the 40-50LY experimental drives?
Mass of Germanium?  That seems to be the case w/ Proto drive improvements, but then Compact Cores blow that out of the water.  And its hard to imaging a Standard core getting much bigger but the IU drive was on a standard JS so something had to be different.
For that matter the Aegis doesn't have a HUGE amount of Cargo like most SLDF ships to increase its core in size.

If Distance is a factor at all in calculations then how much of a factor, like does it affect a to-hit roll for a successful jump?
If 30LY is the dead set limit then does exceeding it at all cause a fail?  What if the Nadir is 30LY but you try to jump to the far side of the system outside the orbit of "Pluto" or something.  Fail for a distance of a couple AU?

I feel like I'm going to chalk this one up to "works for your campaign" or "close enough on the map" w/o getting too detailed on the actual distances listed on Sarna.

[Daryk]

That's the chalk I'd use... :)

[PuppyLikesLaserPointers]

There is nothing on SO, at least, that says what happens if you try to do so. It have no mention about calculate the range, only for the jump points the ship initiate jump and the supposed destination. Although various fluff writes on SO does says that thirty LY is a hard limit since 23th century. It won't be a exact 30LY, though, but nothing says its exact length either.

I did searched A Time of War but no avail. The rules even don't concern about this.

Perhaps such vacancy means that the settings team thought that it is not possible to try to do this intentionally by modern K-F drive, unless you did some weird touches such as 'super jump'. But nothing says what exactly occurs when you did, or I didn't find that.

[Cannonshop]

There is nothing on SO, at least, that says what happens if you try to do so. It have no mention about calculate the range, only for the jump points the ship initiate jump and the supposed destination. Although various fluff writes on SO does says that thirty LY is a hard limit since 23th century. It won't be a exact 30LY, though, but nothing says its exact length either.

I did searched A Time of War but no avail. The rules even don't concern about this.

Perhaps such vacancy means that the settings team thought that it is not possible to try to do this intentionally by modern K-F drive, unless you did some weird touches such as 'super jump'. But nothing says what exactly occurs when you did, or I didn't find that.

alternatively, sometimes they leave stuff out so they have some flex for later, for instances, if the Plot demands something that would otherwise be impossible, having that gap lets them fill it to make it possible for the sake of a given plot point or development later.

[RifleMech]

Primitive Jumpships and Warships do have maneuvering drives so maybe jumping .2 LY short isn't as big a deal for them as it is standard Jumpships? And maybe the little bit past 30 LY is the furthest point in a planet's rotation, like during the summer months? Or the jump limit is about 30 LY, so a little over doesn't hurt while a lot does.

[Daryk]

0.2 LY is more than a little too much to overcome with conventional thrust.

[ANS Kamas P81]

No, that little bit past 30 light years - that 0.2 LY we're talking about - is over 12,600 times the distance from the Earth to the Sun.  The week-long transit from the jump point to Earth is about 8-9 AU, so there's no way someone's simply relying on maneuvering drives to make up that distance.  That's something like 1500 weeks of transit time, or near thirty years.

Space is big.

[Daryk]

Exactly!

[Cannonshop]

The universe in reality isn't neatly sliced into increments of ten, why should jump travel be neatly sliced into similar nice, round numbers?  Earth's orbit is not neatly 365 24 hour days, hell, our rotation isn't even a full 24 hours.

It's all got variables and variations.  30LY is an average because existence doesn't (and shouldn't) come  in neatly precalculated packages.

It's not Exactly 30 LY, because the universe doesn't come in exact scaling measurements.  It's all built to tolerances, with variation and variables.  your car doesn't get Exactly the mileage (Kilometerage?) that it says on the sales brochure, that's an average worked out in testing by taking a lot of samples, and dividing the sum.

so too, I would suggest, for Jumpship travel.  Some Merchants can stretch further, call 'em "Wednesday Cores", while others fall short (Friday and Monday cores)-but they all can just about reach 30 LY, more or less.

It's the floor, below which, the product is too defective to sell.

But they're not going to promise you 31, 35, or 40 LY at the dealership, because not all of 'em can do that...but at the shipyard dealer, they won't sell you a core that can't make 30LY out of the box once that became the standardized expectation-they'll grind it up and reprocess it instead until they can sell you a core that will MAKE 30 LY...even if you're only going to ever make a 5LY hop between two close-knit stars.

Because they can sell it to at a given price point (well, sell it to the bank who'll repossess it from you if you can't make your payments.)

It's like when GM would built a model of car, and some of the cars off the line can pull 47 miles/gallon out of a downdraft carb, but the average is going to be 15-that's what they put on the sticker, and any of that model that can't make 15 gets reworked, because if it gets out that they're selling bum vehicles, banks won't do the financing.

Basically, for a Standard Jumpship then, 30 LY is the average range that the shipping industry settled on for "we can finance this at a good rate".  Further WOULD be better, but it's not reliable enough to keep the yard working, so they don't claim to tolerance or manufacture past 30 LY. (after which, you start getting weird accidents, see for example, SLS manassas).

So why 30LY? it's a decent chance in a unvierse like Battletech, that there's going to be habitable something within 30LY of a given star, and enough of them WERE habitable that this became a baseline expectation for "We're probably going to go this far in a single jump at least once, usually more than once".

which lets the manufacturer have tolerances that are reasonably repeatable with the core-casting or core-forging gear they have.

and it covers most potential clients' needs.

This, in turn, would influence MILITARY suppliers (compact cores, subcompacts) because if your fleet's movements aren't predictable, (aka you don't know how far any given ship of a given class can actually go reliably) then your navy's not going to be much good, and being able to jump as far as Bill McHukster in his Merchant makes your space soldiers a laughingstock when they come to enforce the rules.

and nobody wants that.


can you find a ship that can go further on a jump? with enough money, but you're not going to find two that can do it with any reliability minus being the conglomerate that owns all the merchant banking and the lion's share of communications...and that conglomerate or goofy cult? has a vested interest in maintaining the appearance of 30LY being an absolute, as opposed to average, limit.

after all, they own parts of everyone else's yards too, and there's a decided financial and strategic motive to keep things...stable...ish.

[RifleMech]

0.2 LY is more than a little too much to overcome with conventional thrust.

No, that little bit past 30 light years - that 0.2 LY we're talking about - is over 12,600 times the distance from the Earth to the Sun.  The week-long transit from the jump point to Earth is about 8-9 AU, so there's no way someone's simply relying on maneuvering drives to make up that distance.  That's something like 1500 weeks of transit time, or near thirty years.

Space is big.

That would leave orbital rotations and average jump distance.

[PuppyLikesLaserPointers]

Yeah. 0.2 LY is ridiculously long range, after all. 12600AU is not a kidding. There is a reason why AU is only used in solar system.

[theagent]

0.2LY wouldn't be quite so bad...but I still wouldn't recommend the trip.

• Assuming you have to account for galactic drift, let's say you have to actually travel 0.3LY.  That's 18,972.0531 AU, or 2.83822 trillion km.
• Assuming you're going to use constant thrust the entire way, first accelerating towards the turnover point to decelerate, we'll cut that in half:  0.15LY, 9,486.0265 AU, or 1.81911 trillion km.
• Assuming starting velocity (v⁰) is 0mps, & that our start part is "0" (x₀), and assuming 1g acceleration (so that we can convert the burn times to burn-days), the formula is X = X₀ + v₀t + (at²)/2, which simplifies down to X = (at^2)/2.  We have X & a but don't know t, so we rewrite to solve t:  t = SQRT (2X/a).
• Substituting for X (1.81911x10¹⁵m) and a (9.80665m/s²), we get t = SQRT (1.44709x10¹⁴), which works out to 12,029,501.39 seconds, or 3,341.5282 hours, or 139.23 days. That's the time to accelerate, so double it to 279.46 days for the entire trip.
• So you would need enough fuel for roughly 280 burn-days...or almost 40 weeks of travel.
• FYI...when you reach turnover, your ship will be approaching 0.4c (0.3935026c, to be exact), so don't hit any rogue asteroids

That's a lot of fuel & life support to have on hand.

But it could be worse.  If you only had, say, 43 burn-days of fuel, you could use 21 burn-days to accelerate, save back 1 burn-day as a reserve, & plan on using the remaining 21 burn-days to decelerate closer to your target...but you'll end up spending two and a half years in freefall as you coast from shut-down to turnover (total trip time 944.1 days, roughly 2.58 years).  Your life support would run out well before that.  Even if you could extend to 90 burn-days each way, you'd still have almost 341 days between burns.

[Frabby]

The universe in reality isn't neatly sliced into increments of ten, why should jump travel be neatly sliced into similar nice, round numbers?  Earth's orbit is not neatly 365 24 hour days, hell, our rotation isn't even a full 24 hours.

It's all got variables and variations.  30LY is an average because existence doesn't (and shouldn't) come  in neatly precalculated packages.

It's not Exactly 30 LY, because the universe doesn't come in exact scaling measurements.

Right up to this point I agree with you.

But I don’t think the car manufacturing/mileage comparison works. It’s a good argument but it is entirely based in real-world economics. Within the FASAnomics of the BattleTech universe or when viewed from a LosTech angle, the argument unfortunately falls apart.

You could say my mileage varies. ;)

[VhenRa]

0.2LY wouldn't be quite so bad...but I still wouldn't recommend the trip.

• Assuming you have to account for galactic drift, let's say you have to actually travel 0.3LY.  That's 18,972.0531 AU, or 2.83822 trillion km.
• Assuming you're going to use constant thrust the entire way, first accelerating towards the turnover point to decelerate, we'll cut that in half:  0.15LY, 9,486.0265 AU, or 1.81911 trillion km.
• Assuming starting velocity (v⁰) is 0mps, & that our start part is "0" (x₀), and assuming 1g acceleration (so that we can convert the burn times to burn-days), the formula is X = X₀ + v₀t + (at²)/2, which simplifies down to X = (at^2)/2.  We have X & a but don't know t, so we rewrite to solve t:  t = SQRT (2X/a).
• Substituting for X (1.81911x10¹⁵m) and a (9.80665m/s²), we get t = SQRT (1.44709x10¹⁴), which works out to 12,029,501.39 seconds, or 3,341.5282 hours, or 139.23 days. That's the time to accelerate, so double it to 279.46 days for the entire trip.
• So you would need enough fuel for roughly 280 burn-days...or almost 40 weeks of travel.
• FYI...when you reach turnover, your ship will be approaching 0.4c (0.3935026c, to be exact), so don't hit any rogue asteroids

That's a lot of fuel & life support to have on hand.

But it could be worse.  If you only had, say, 43 burn-days of fuel, you could use 21 burn-days to accelerate, save back 1 burn-day as a reserve, & plan on using the remaining 21 burn-days to decelerate closer to your target...but you'll end up spending two and a half years in freefall as you coast from shut-down to turnover (total trip time 944.1 days, roughly 2.58 years).  Your life support would run out well before that.  Even if you could extend to 90 burn-days each way, you'd still have almost 341 days between burns.

My calcs for 0.2LY is about 330 days [real time, 319 with time dilation]

159 days burn, a few hours drifting, than turnover and 159 days of deceleration. You reach 42% of light in the process.

The issue is for such a long trip you can't really use the standard calculation because relativistic effects are starting to come into play.

[Cannonshop]

Right up to this point I agree with you.

But I don’t think the car manufacturing/mileage comparison works. It’s a good argument but it is entirely based in real-world economics. Within the FASAnomics of the BattleTech universe or when viewed from a LosTech angle, the argument unfortunately falls apart.

You could say my mileage varies. ;)

When you're looking  at any product, you're looking at tolerances.  the smaller the item the easier it is to keep tolerance-to a point, the larger scale the item the wider the tolerances are going to be.

Compare a jet aircraft with tolerances down to plus or minus .003 inches versus a skyscraper where 1/8th of an inch is considered 'too close to measure" (and that's just rude structure, not even the moving parts).

I used the mileage example because it's something most people can immediately grasp and envision.

the other reason, is the existence of 'single jumps' that per the Sarna, couldn't happen if the 30LY were a fixed number that could not be exceeded fairly routinely.  It makes more sense, for 30LY to be the "achievable average performance for a production ship" and thus, become the baseline standard for ALL Production ships-because they can achieve it as a minimum performance standard and not bankrupt every shipyard that tries to exceed it on the regular.  (that last .0005% of precision uses hundreds of times more money, time and resources, than the preceeding 99.995%)

I work in industry-as in work in industry, (as opposed to sitting in meetings).  Flaws are inevitable, that's why we have tolerances in the first place-to average out the flaws in order to get a set performance out of the product.

You could shave a few TONS off of most jet airliners if you could somehow make the structure parts to the bare minimum thickness required to meet the spec.  The problem is, there are variations in the alloys, variations in the processing, variations in the manufacturing and variations in the assembly and you'd have to scrap ten planes to get one that works by doing that.

to stay in business (and keep the customers going) there have to be tolerances worked into the build-an allowable slop...but that slop has to meet a minimum performance standard or your airframe is shit.

so I see 30LY as the performance minimum that's been adopted across the industry, and, thanks to 300 years of killing scientists and engineers and burning books, it's become accepted as an ultimate limit because anyone with the skills to exceed it on a repeatable, regular basis? died a long time ago and whatever they knew died with them.

[theagent]

My calcs for 0.2LY is about 330 days [real time, 319 with time dilation]

159 days burn, a few hours drifting, than turnover and 159 days of deceleration. You reach 42% of light in the process.

The issue is for such a long trip you can't really use the standard calculation because relativistic effects are starting to come into play.

Close enough, probably.  Although at least time dilation isn't too bad (only losing 11 days, for example, from a 330-day trip isn't too bad). 

It's when you start getting significantly above 0.6c that the time-dilation starts to get really bad.  Losing 20% of the time at 0.6c is going to start really playing havoc with your time calculations, losing 40% at 0.8c makes it even worse, & I really wouldn't want to push it to the point of hitting .9c or higher.  Hell, I'm not familiar enough with astrophysics to even calculate how the acceleration curves would get modified as time-dilation starts affecting the vehicle...

[Daryk]

Lorentz equations aren't that bad... it's just math, after all... :)

[DevianID]

For Lorentz to factor we would need to know if the increased mass of the ship was not countered by the increased mass of propellent.  Since the propellent of our torch ships is not defined other then "it works" its fair to assume Lorentz doesnt matter for torch ships at 'merely' 40% C.

Also, jumpships seem to already handle the drift velocity between stars, so you shouldnt need to treat a .2ly missjump as .3ly due to drift, as drift has to be factored out already or you'd jump to a zenith point only to see your target star whizz by you.

Edit: Im no loremaster but i'd assume that a 'real' jump would rely on the space distortion from gravity to punch its hole through space to teleport.  So you probably cant 'dead space' jump even if you wanted to, you need to connect to the space distortion and set your reference frame velocity.  I mentioned it earlier but more or less since they dont do deadspace jumps to, for example, very very easily travel from clan space or periphery space in the civil war to terra with 0 chance of detection, then there SHOULD be a reason for this.

[RifleMech]

"Dead space"? As in jumping to a point between systems? I'm pretty sure it's been done. It just isn't a favorite place to go without lots of fuel, or a Lithium-Fusion Battery.

[Daryk]

Jump "points" are defined by a maximum gravitational field... anything outside of that field is fair game for a jump.

[RifleMech]

Thanks. I thought that was the case.

[PuppyLikesLaserPointers]

That is doable I think. Usually you don't have a reason for this for you need a lots of fuel to recharge the battery without an aid for a star. But if you are at least one among criminal(include pirate), soldier who is in charge of attack a system and you want to be unnoticed until you can reach to the target system, spy, or ComStar Explorer Corps or various other explorer, then it is still an option.

Yes for normal merchants and civilians, as well as the soldier on their own nation right now, you don't need to waste the fuel like that since you can use the local star's wind instead.

edit: It's from the other game series, but I have seen Praetorian of Dorn, the novel of Horus Heresy, that the enemy legion attempt to ambush by jump the fleet far away from the distance than the defenders are able to aware their jump, then using their thrusters to advance for around a half of year(or a full year? I don't recall it correctly) to remain unnoticed until they are very close to the system's defense stations.

So, if you have enough ships to spare, supply, and more importantly, time to prepare, then it is not entirely impossible to jump far from the standard jump points then ambush the enemy without an electromagnetic pulse that could be detected by the defenders.

Although I wonder that, even if their destination is farther than the standard jump point, but still their arrival leaves the electromagnetic pulse anyways, and as you know you cannot hide anything on space; will the defender's observatory remain unnoticed such a light far from the system, but still very closer than the other star? A system that makes you to decide such a costly scheme, that surely have the advanced observatory as well as the defending fleet as well?

[Intermittent_Coherence]

Ehhh... Any fictional FTL has limitations. It's baked into the setting and informs it. 30LY seems arbitrary but it's been around for a while and works as well as any.

It doesn't have to be a hard limit. Maybe there are exceptions. Maybe this yard has better build quality that can do a bit more. Maybe this other yard adds a proprietary widget to their products that allows them to squeeze a bit more. Maybe some crews are just that good. All these add flavor to a setting.

It's also a way to add narrative tension. Everybody knows doing more than 30 is high stakes gambling with everybody's lives, but what if they have to get to someplace (or away from someplace) real quick? Cue the exception.

[AlphaMirage]

That is doable I think. Usually you don't have a reason for this for you need a lots of fuel to recharge the battery without an aid for a star. But if you are at least one among criminal(include pirate), soldier who is in charge of attack a system and you want to be unnoticed until you can reach to the target system, spy, or ComStar Explorer Corps or various other explorer, then it is still an option.

Yes for normal merchants and civilians, as well as the soldier on their own nation right now, you don't need to waste the fuel like that since you can use the local star's wind instead.

So, if you have enough ships to spare, supply, and more importantly, time to prepare, then it is not entirely impossible to jump far from the standard jump points then ambush the enemy without an electromagnetic pulse that could be detected by the defenders.

Although I wonder that, even if their destination is farther than the standard jump point, but still their arrival leaves the electromagnetic pulse anyways, and as you know you cannot hide anything on space; will the defender's observatory remain unnoticed such a light far from the system, but still very closer than the other star? A system that makes you to decide such a costly scheme, that surely have the advanced observatory as well as the defending fleet as well?

It doesn't use that much more fuel and as it is hydrogen it is pretty cheap and available onboard the dropships it carries if not its own internal supply. I argue in my Free Trader's Guide that such a 'burner' operation would be the default during periods of abundance as you can shave almost a day of charge to jump with no penalty and it would be more consistent than using sails. Sails would of course still be used but that would be more of a pacing issue up to the jump captain.

15 AU is the detection limit for a jump emergence so just jumping beyond Uranus will make your appearance difficult to detect by the emergence wave at least. You could also jump at an eccentric point off the planetary disk, to somewhere not visible from the target continent on that planet. That could help conceal your thrusters as you approach as few systems have a space based detection grid, it is more likely to be ground based.

[RifleMech]

That is doable I think. Usually you don't have a reason for this for you need a lots of fuel to recharge the battery without an aid for a star. But if you are at least one among criminal(include pirate), soldier who is in charge of attack a system and you want to be unnoticed until you can reach to the target system, spy, or ComStar Explorer Corps or various other explorer, then it is still an option.
(snip)

I think regular merchants might use such areas as well if it's the best way between two planets. If the route is travelled enough there might even be a recharge station there.

[PuppyLikesLaserPointers]

It doesn't use that much more fuel and as it is hydrogen it is pretty cheap and available onboard the dropships it carries if not its own internal supply. I argue in my Free Trader's Guide that such a 'burner' operation would be the default during periods of abundance as you can shave almost a day of charge to jump with no penalty and it would be more consistent than using sails. Sails would of course still be used but that would be more of a pacing issue up to the jump captain.

15 AU is the detection limit for a jump emergence so just jumping beyond Uranus will make your appearance difficult to detect by the emergence wave at least. You could also jump at an eccentric point off the planetary disk, to somewhere not visible from the target continent on that planet. That could help conceal your thrusters as you approach as few systems have a space based detection grid, it is more likely to be ground based.

You don't need to exit too far from the destination planet, then. Maybe some systems have artificial satellite for surveillance but it also needs the maintenance that not all systems can afford that.

I think regular merchants might use such areas as well if it's the best way between two planets. If the route is travelled enough there might even be a recharge station there.

Perhaps, although costly, but it is possible and also worth considering to make a refueling station on the stopover sites even if the area has no habitable planets - or the space don't even have a star nearby! Although you need to keep fed the station with not only the food for the staff as well as the hydrogen if its position lacks a star nearby(thus it also lacks a jovian planet nearby as well), but if it increase the overall tranport quantity then the larger government might consider make one. I don't have in mind about any of but some kind of those station could be already exists in battletech universe and I won't be surprised even if it's true.

[RifleMech]

Perhaps, although costly, but it is possible and also worth considering to make a refueling station on the stopover sites even if the area has no habitable planets - or the space don't even have a star nearby! Although you need to keep fed the station with not only the food for the staff as well as the hydrogen if its position lacks a star nearby(thus it also lacks a jovian planet nearby as well), but if it increase the overall tranport quantity then the larger government might consider make one. I don't have in mind about any of but some kind of those station could be already exists in battletech universe and I won't be surprised even if it's true.

I don't think every jump area would have one. Just the most heavily travelled. It'd also make sense that the House would pay for it as it keep their economy moving. Hauling supplies to the station could be done in trade for a recharge.

[Daryk]

There are enough dwarf stars between habitable worlds to not have to build a recharge station that needs constant refueling in completely dead space.

[PuppyLikesLaserPointers]

Yeah. If you want to make it, then there would be many jumpships want to use that as the waypoint.

[VhenRa]

Honestly, the most likely to exist [in terms of having lots of traffic and some, any, sorta infrastructure] are systems that used to be inhabited prior to the 1SW that are well placed for short-cuts.

https://imgur.com/a/4z1HHVz

Take this for example.

[Daryk]

Yeah, Meinhof in that example is EXACTLY the kind of system that would have a recharge station.

[quewin]

Expanding on your thought, how much of the recorded colonization during the Star League era was simply building (recharge) station(s) in transit systems? How many of these were abandoned simply because the infrastructure could no longer be maintained?

All those canon Clan Waypoints and Transfer Stations (that disappeared) certainly provide a precedent.

An even more interesting possibility with somewhere like Meinhof is that its infrastructure could have reasonably been built (and owned) by General Motors itself.

[Daryk]

That's exactly what I was thinking... by that point, private enterprise could totally afford to support a recharge station... ;)