Goes out the fresher vent, it does, silly.

Really, I've always liked jump grids and plates better but I like T5's take where the grids, plates, and bubble co-exist and have different roles.  Not so fond of jump occlusion.  We had a debate over nuclear damper fields cancelling out one time but a friend who's a roadie for a local band just nodded and discussed speakers cancelling out exactly the same way.

But Traveller's space dynamics exist to justify a game structure rather than mapping physical reality.  In general Traveller tries very hard to be gamist rather than simulationist.  I don't always agree with the workings of it but it is very functional in play.

I have a similar argument about the Spacemaster Privateers setting.  Which is on the surface a terrible sf setting full of furries and reactionless drives and free quantum power and force fields.  On the other hand, the furry races are easy to pick up and play archetypes.  Their dispersion by unknown ancients (I hate those guys) makes it possible for just about any party composition to infiltrate the evil empire.  The drives not requiring fuel or power strips down the record keeping and accounting that many find objectionable in an rpg.  Sure most PCs will put planet killer asteroids in their arsenal within a session or two but the bad guys can do it too.  And asteroids can be destroyed and redirected pretty easily in such a setting.

hmmmmm...I always have wanted to run another SPAM campaign...

Quote from: Phillip;857939And all that acceleration action is accomplished without any mass-energy reaction. (Even with some slipped in, the gaffe is far beyond any stretch by which "the computers are too big".)

Way back in early development, the concept was some sort of gravity drive with the reaction being on planets, but that was inconvenient for deep space.

Of course, it's inconvenient only if one doesn't abracadabra the rapid decrease of field strength over distance. That seems to me a less radical hand-waving, but sometimes the bigger load of baloney is easier for audiences to swallow.

I think you could get some mighty compact spaceships with antimatter drives. Assuming engines tough enough to take necessary increases in heat, the difference for a wide range of missions is not propellant mass but rather so many grams (or micrograms) of antimatter. Hand-wave a mirror for gamma rays, and you've got a "photon drive" that's about as good as rockets can theoretically get.

Yeah, they are effectively inertialess drives. The justification wobbles to and fro between editions, but for the most part they are. I guess it depends on how you define hard science (and also what you consider important). For me, they are rockets, they use energy (not propellent, but that's clearly a gamist convention, keeping fuel reserved for interstellar transit so that the GM can control which trade routes the PCs can take based on their fuel reserve), and they act like rockets (you accellerate towards your target, turn around, and decellerate). I don't really care that their actual definition is inertialess drive instead of gravity drive or photon drive. I can change that easily enough. What's important is that they act like rocket engines.

But that's just what works for me.

Quote from: Willie the Duck;858183What's important is that they act like rocket engines.

Well that the thing, the mechanics behind traveller's sub-light travel don't reflect the real world physics of inter system travel. Nor do they reflect Traveller's own technological handwaves. They are not even an abstraction.

Why? Because everything is in orbit. It never a case of pointing at a destination (or even leading it enough) and just go. However even with reactionless drive real-life physics imposes a lot of ifs, buts, and "oh by the ways".

So what is a better abstraction of the situation that still gamable? By using delta-vee. Delta-vee is the total change in velocity that a vessel is capable of. For example your rocket has to be capable of creating a change in velocity from 0 to roughly 9.4 km/sec in about 10 to 15 minutes to make Earth Orbit. If Earth had no air it would be exactly 7.8 km/sec but atmospheric drag and engines inefficiency while in the atmosphere means you need more energy.

The most gamable mechanic for rockets is a delta-vee budget for the different orbits and the time to achieve said orbit. One of your vechicle's states is the total delta-vee contained in your fuel.

For reactionless drive, the only constraint is time. Generally in most settings reactionless drives can put out thrust for weeks or months. So the question becomes how much delta-vee I can add in X time. Too low of a thrust means your craft will eventually be deflected from its destination.

In real life, ion drives come the closest. Currently Ion drives produce too low of a thrust to launch a rocket into orbit. However once a probe is in orbit then it can thrust for months as the ion drive is that efficient for the amount of fuel carried.

This gets into an area of physics where you are plotting orbits involving continuous acceleration which what the original Traveller formulas try to handwave. Unlike delta-vee budgets there is no simple abstraction that really captures what goes into this. Indeed how NASA and most space agencies handle this is to use special simulation software designed to run dozens of permutations to find the right time to launch and to do maneuvers.

What I would do for a gamable mechanic to abstract continous acceleration is for me as the designer to plot out some typical travel times to the same destinations on the delta-vee budget tables at different rates of accelerations.

Then put that in a table and be done with that. Most star system generation place their planets in specific sets of orbits making the setup of the table straight forward.

I would also mention the idea of using launch windows as an option. In the real world the only way to take the fastest way to a in-system destination is at specific times whether you doing with it a rocket or the continuous acceleration of a reactionless drive. Outside of that window, the voyage takes longer sometimes way longer even if the straightline destination makes it seem it should be a lot quicker.

I would mention this because for some campaign it can be a useful complication to challenge the PCs with.

The good news is that you don't really need to do any math to have this in a campaign. Due to how orbital mechanics work it is enough to use a simple set of guidelines and you will be in the ballpark as far as any numbers are concerned. Especially for games centered around reactionless drives like Traveller.

Quote from: David Johansen;857950Really, I've always liked jump grids and plates better but I like T5's take where the grids, plates, and bubble co-exist and have different roles.  Not so fond of jump occlusion.  We had a debate over nuclear damper fields cancelling out one time but a friend who's a roadie for a local band just nodded and discussed speakers cancelling out exactly the same way.

The way I handled jump in my Traveller campaigns was that it was an extension of the same gravitic technology that produced Grav Plates and Maneuver drives.

What I said a Jump Drive does is use gravity fields to fold a bubble of space around the ships as governed by the jump grid into a Alcubierre Warp. A Alcubierre warp is a way to distort space time so that a ship will move. However the energy needed to make a Star Trek warp drive is beyond even the ancients. But if you fold space in a way that you are in a realspace bubble connected by a microscopic neck to rest of the universe then the energy needed to form a Alcubierre warp around that neck is achieve even by Tech Level 9 technology.

However as it turned out only certain configurations are stable and those happen to be the ones that correspond to the speeds that produces Jump 1 to 6. Those configurations are like a marble rolling and encounters a dip. It it would naturally roll in and settle in the bottom. The other configurations are like the top of hill. The marble could be perched on top but the slightest change would send it rolling down.

Misjumps are a result of the Jump Drive initiating while the marble on top of one of those unstable hills. A ship can't turn or communication because it only connected through a microscopic hole to the universe, and because once the configuration is set it can't be altered in flight because again it "outside" of the bubble that the ship is in.

As it happens a Alclubierre warp configuration will decay in an average of 178 hours causing the ship to emerge in real space.

If that little microscopic warp configuration runs within 100 diameters of another mass it will stop it's motion and when it decays 178 hours later the ship will emerge into real space.

https://en.wikipedia.org/wiki/Alcubierre_drive
http://www.npl.washington.edu/AV/altvw81.html

This is my source for the microscopic folding
http://www.npl.washington.edu/AV/altvw99.html

Quote from: estar;858202What I would do for a gamable mechanic to abstract continous acceleration is for me as the designer to plot out some typical travel times to the same destinations on the delta-vee budget tables at different rates of accelerations.

Then put that in a table and be done with that. Most star system generation place their planets in specific sets of orbits making the setup of the table straight forward.

.

I'm not entirely clear how, in a purely gamable fashion, this is fundamentally different from Traveller (Mongoose anyway), having a table of rough trip times at various rates of thrust, as rated in G's.  Given that my copy also includes text pointing out that this includes acceleration and deceleration phases e.g. ye olde rocket flip.

If I'm following the argument correctly, Traveller positing a means of thrust that translates energy directly into motion, rather than thrust as material ejection, is more of a problem than FTL jump drives for considering Traveller remotely 'Hard'.

Traveller vehicles are all just mumbo jumbo. Don't even try to assign scientificness to them.

So, what game starships do you recommend?

Quote from: Spike;858704So, what game starships do you recommend?

It depends on what you're trying to do with starships in your game. More importantly, what your players are trying to do with them if they have their own setting in mind because they know nothing about Traveller's.

Well, Attack Vector Tactical is the gold standard of realistic three dimensional space combat.

GDW's Triplanetary is actually a pretty good two dimensional in system only game.  I've always wanted to run it with Ogre as the ground combat rules.

For Roleplaying, GURPS Vehicles and GURPS Spaceships are by David L. Pulver who really knows his stuff.  Sure you can put super reactionless thrusters in your ship but the rules cover other types of engines.  Be aware the tolerances are really unforgiving and the performance of realistic engines will always seem uninspiring.

Most sf rpgs try very hard to avoid that level of frustration and disappointment.

I think Cyberpunk had a space supplement, Near Orbit that was supposed to be pretty good.

I lose 1d12 SAN every time I even look at GURPS Vehicles, but then again advanced math was never my strong suit.

I don't mind more "abstract" starship systems, actually. Re: Traveller, we play using GURPS these days and I would never design my own ship using that system (maybe the "modular system, but still). The old LBB Starship system wasn't as baffling, but I guess it's because I was younger and my mind was more flexible.

In the non-RPG realm I always loved "Starfire" and of course "Star Fleet Battles". I mean really, REALLY loved them - Starfire specifically. You could play it in 30 minutes if you wanted, or have huge battles lasting hours. Was fun.

Full Thrust is a space wargame that I've played a lot in the past and there's a Traveller expansion/variant for it called Power Projection that is quite nice... probably what I'd be inclined to use if I were running a Traveller game and wanted to run something more than a quick 1on1 ship battle.
Full thrust has rules for ship design as well as optional vector movement that's similar to Mayday/Triplanetary but doesn't require hexes or multiple positioning markers. No 3D but it doesn't feel like sailing a ship or flying a plane either.

Cool, hadn't heard of that one, looks interesting.

That's one thing I do miss about the early days of my gaming life (late 70's-early 80's) - there were a TON of great wargames/boardgames (and many not-so-great I'm sure, but I was young). There are still at least a dozen that if I ever saw again I'd probably buy them in a heartbeat, just because I always wanted them and couldn't afford them.

(sorry for threadjack)

Starfire needs a relaunch and KS. Truly great game. Discovered it after years of playing SFB and just went wow!

Quote from: Spinachcat;858734Starfire needs a relaunch and KS. Truly great game. Discovered it after years of playing SFB and just went wow!

I always did like the cover art on the Starfire stuff but never played it.
Looking around just now there seems to be a baffling array of versions and supplements for it... some to be had cheaply, some not.
What's the most popular version of it? Did it ever have an RPG the way SFB has Prime Directive?

Quote from: Werekoala;858726I lose 1d12 SAN every time I even look at GURPS Vehicles, but then again advanced math was never my strong suit.

GRUPS is more accounting than advanced math.

QuoteIn the non-RPG realm I always loved "Starfire" and of course "Star Fleet Battles". I mean really, REALLY loved them - Starfire specifically. You could play it in 30 minutes if you wanted, or have huge battles lasting hours. Was fun.

And Starfire let you build your own ships and included technological obsolescence.