Travel time, hyperspace, etc

[FluffyFreak]

Rudimentary L4/L5 display added to SystemView in PR #3536.

Which I shall leave as a WIP for the time being whilst we discuss it.

[clausimu]

Some of this is just going to have to "play out", I mean we can discuss it, and I'm implementing the L4/L5 viewing right now

That's great!

[impaktor]

Just like clausimu I was a bit confused by fluffy's earlier post, but:

Ok so entertaining the "jump-to" idea for L4/L5 it would work something like:

• takeoff from planet/station,
• reach hyperspace safe distance,
• target another planets L4/L5 in system OR a different system entirely,
• jump,
• arrive at planets L4/L5 OR the usual several AU from star in another system,
• fly to destination planet/station normally.

That is exactly the way I imagined it would work. Fake reason: you can not resolve the L-points for targeting them when not in the same system.

For when doing in-system jumps, I guess the precision of entry point should be pretty high, since having a fudge factor of several AU might drop us close to another planet's L-point, which might seem strange. So, by chance, targeting Mars' L-point might drop me right over Earth, which would be strange. I guess when you jump to an L-point, this is done from +12 AU out far from any disturbing mass.

Ok, I'm officially confused.

If I understood you correctly, you we're talking about entering a system at an L-point. The way I thought we discussed it was you still enter the system way out from the main star, first then can you target L-points.

[bszlrd]

Ok so entertaining the "jump-to" idea for L4/L5 it would work something like:

• takeoff from planet/station,
• reach hyperspace safe distance,
• target another planets L4/L5 in system OR a different system entirely,
• jump,
• arrive at planets L4/L5 OR the usual several AU from star in another system,
• fly to destination planet/station normally.

Yupp, this makes sense in my opinion too.
Bad guys from a risky job could be lurking around the L-point closest to the destination, waiting to ambush you. You might even trick them by jumping to a bit further L-point if you have the time to finish the job by that route. And if they chosen the wrong L-point (or not having ships on both), they might try to intercept you when you turn up on their scanners. At this distance I imagine that it would be far easier than from a 12 AU trip.
Assassinations could work similarly: you lurking and waiting for the target at the L-point. And you could also pick the wrong one and attempt an intercept before the target lands.
Impaktors false reason seems reasonable about the why too. Not precise enough from another system to aim for it safely. And/or you come in "too fast" when you jump from another system, practically no chance to hit it close enough. Like a slow golf ball would go into the hole even if you don't aim perfectly, but if it's very fast, then it just goes around the edge of the hole and rolls away.

Question: how much time an in-system jump would take? - Faster than light, or not so fast? (Like there's not enough room to "accelerate" in hyperspace to reach that multiple C speed of jump between systems?). How much it would depend on the distance? Like if a pursuer can't intercept it's target, from several light-minutes/hours away, could his/her sensors pick up the departure cloud from that distance, see the exit position with the analyzer and jump after the target? Maybe even reach it sooner because he/she was closer to it than the target.

Also from fiction standpoint, there could be reasoning that you can't jump to an L-point if there's a station there, so there's no convenient police base there. They need to patrol the area, and especially in smaller/poorer systems there might not be enough resources available to "put an officer to every corner".

[FluffyFreak]

Yeah sorry for my earlier confusion, I think it was the I-War reference that threw me, didn't you have to jump both to and from Lagrange points in I-War?

[DraQ]

I would also like to add another couple of factors to using the hyperdrive, both in-system and conventionally:

• must be facing destination direction of jump, to within a few degrees not 100% of course,
• must not be jumping through planet/star/massive-body.

Those two are interlinked obviously :)

Agreed, it's pretty commonsensical limitation and would be nice to have.

Regarding L-points - I'm not sure L4/5 would be a good idea for jump points:

• Being stable L points they make good candidates for housing not just artificial objects but also a natural bodies. Currently and here in Sol they only house small objects like some asteroids and some minor moons of Saturn but there is no reason why they couldn't potentially have whole planets at them (one of the hypotheses regarding formation of the Moon postulates Earth's coorbital that got destabilized and there was a report of potential pair of extrasolar coorbitals a few years ago).
• If we're going with gravitational explanation, then the only point where the gravitational forces cancel out is L1 or rather a point close to it (at L1 you also need to have centrifugal force cancelled out, so it's closer in) that shouldn't be that hard to calculate lying on the line joining both bodies where m1/(d1^2) = m2/(d2^2) (where d is the distance to the respective body and m is its mass), since all terms are greater than 0 the distance ratio equals sqrt of mass ratio.
• The near-L1-point point would also not require any special handling logic, assuming multiple body gravity is implemented at least in regards to adjacent frames of reference (as in immediate parent and children), if jump limitations are to be gravity based and explicitly finding it would only be needed for player and AI navigation, jump logic could be implicit.

Do note that any massive body in L4 or L5 will have its own gravitational equilibrium point near its L1.

Also from fiction standpoint, there could be reasoning that you can't jump to an L-point if there's a station there, so there's no convenient police base there. They need to patrol the area, and especially in smaller/poorer systems there might not be enough resources available to "put an officer to every corner".

Sadly this doesn't work - base could be easily put in orbit around L4/5 at minimum safe distance as L4/5 are stable points so bodies perturbed out of them will stick around (but even the unstable L1 and L2 allow for something resembling orbits around them at extremely modest stationkeeping effort), besides something else could already be "put" into them (like a planet).
And you would definitely want to put some cops by the only main road into the town - especially when banditry is bad enough that citizens are allowed to carry spaceship grade weapons for self defence ;).

Anyway, here's my take on the subject compiled into cohesive form:

• Jump is technically possible from anywhere as long as there is sufficient clearance (measured in km at most) from substantial material objects (atmosphere included).
• Jump cost consists of fixed part that's the function of drive class (say squared) and variable part that is function of distance, ship's mass and net gravitational force affecting the ship at the moment of jump.
• Fixed part is whatever it takes to energize drive and form the wormhole/warp bubble/whatever ships in Pioneer use for long distance travel, bigger drives need more fuel to be fired up
• Overall jump range as function of variable part is lower than in current implementation, but follows similar logic, except without upper cap - jump can be as long as allowed by the fuel carried
• Jump cost and other parameters is calculated in consistent manner for both in-system and interstellar jumps, fixed part keeps in-system jumps not a free lunch
• Jump cost is increased by adding penalty proportional to net gravitational force affecting the ship and based on base cost, jumping from near any L1 point is free of penalty, jumping from far fringes of the system carries little penalty as well, but isn't very practical.
• AI tries to jump from L1 points if possible, all L points are displayed on orbital map.
• All bodies of non-negligible mass (as in possessing gravitational fields accounted for by game's engine) can be chosen as destinations regardless of whether they are in current system or another
• Exit point is consistent with following rules:
  • Exit point lies on a hemisphere facing the start point around destination
  • Hemisphere's base radius is around 10AU (largest red supergiants may need about as much clearance, which I suspect was the reason for choosing this particular distance back in Frontier)
  • Hemisphere's radius is reduced by a fraction that's inversely proportional to target's mass (low mass bodies have much smaller safe minimum jump-in distances, as mass tends to infinity the minimum distance tends to 10AU)
  • The exit distance also has random noise added that is also inversely proportional to target's mass (low mass bodies are more difficult to focus onto), but may has substantially larger multiplier than minimum distance reduction (so average distance may actually be larger).
  • The exact exit point is randomized (good for both gameplay and fiction) but is increasingly correlated with any other jump to the same destination as distance and time difference decrease.
• FluffyFreak's extra rules are in :)
• Drive sequence triggers shields down
• Drive sequence is interrupted if the ship fires weapons or thrusters or if it is hit

Undecided:

• Travel time formula - should be consistent between interstellar and in-system jumps, but constant velocity probably won't cut it so some sort of curve further penalizing short jumps (due to minuscule distances in-system) could be in order - any thoughts?
• Gravity penalty - based on whole cost or just fixed part? (basing it on just variable part would make it irrelevant for in-system travel, so bad, basing it on fixed part would sort of make sense as it would only affect ship when starting and could be explained as extra cost of wrangling curved spacetime into the right shape)

So in short a typical travel would look like this:

• Take off
• Get clear of the surface/station/atmosphere (obligatory)
• Get to the near L1 point or at least reasonably close to it (desirable)
• Pick any astronomical body in range in current or another system
• Jump
• Arrive at randomly determined point, typically around several AU from the target and on its near side
• Get your bearings and fly normally to your destination

What do you think?

[FluffyFreak]

I think you're suffering from the same confusion as I was DraQ :)

The Lagrange points are "jump-to" locations, destinations, within the same system that you're in. Rather than "jump-from" or departure locations.
Jumping-out can be done so long as you meet all the jump criteria.

Also I've been reading up on calculating L1/2 & 3 points and I have to say that if it's easy then I would like someone to have actually done it.
Instead what everyone does is what you just posted, yet another equation that doesn't actually give you the distance from the Earth toward the Sun where L1 is.

Actually I'm annoyed by all that, everyone assumes you've got a bloody degree in mathematics and it's makes it impossible for someone like me, who struggled with GCSE maths, to join in. It's elitist fuckery.

Sorry it's just really annoying having your weaknesses rammed repeatedly into your face whilst being told that the answer is "simple" :(

[FluffyFreak]

Ok, a bit calmer now, try again.

L4 or L5 is a destination (exit) point for in-system travel - Earth to Neptune.
The Star(s) of a system is/are the target from inter-system travel - Sol to Epsilon Eridani.

When exiting an inter-system jump you come out just like we currently do, nothing changes in this regard, you're still ~12AU from the star you targeted on the side nearest the system you departed.
When exiting an in-system jump you come out at the targeted L4/L5 point, regardless of other mass that's there (for the time being), with some random jitter so you're not popping out at it's exact location atop another ship.

You're got a real knack for overcomplicating things DraQ ;)

[FluffyFreak]

Also that rant wasn't actually at you DraQ, just every asshole on the 'Net who shows you a partial derivation and the goes "the rest is of course obvious..." :)

[impaktor]

Also I've been reading up on calculating L1/2 & 3 points and I have to say that if it's easy then I would like someone to have actually done it.

Well, I used to have the math skill to do it, but that's pretty much degraded now. I'll see if I have time and brush up on my Goldstein Classical Mechanics.

The reason I think L4-L5 are good is not because of "physics", but rather because they have the very good property from a game mechanics perspective of clearly being linked to the planet you want to go to, as they're smack on the orbit of the planet. However, the other L-points are just out in nowhere, and including them in the system view would clutter things up terribly I suspect, and understanding why there are dots all over the place in empty space (in system view) would be highly non-intuitive for some / (many?) players.

As for accidentally jumping into a station/asteroids in the L4/L5 points, that can easily be hand-waived away with space is big.

shows you a partial derivation and the goes "the rest is of course obvious..." :)

Ha!, sounds like some of my math-books, they would show the solution of an example problem with just saying "answer is obvious".