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Old 06-17-2009, 12:58 PM   #21
Ulzgoroth
 
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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Originally Posted by Timolas View Post
If the drive doesn't let you land on the other hand, but does deposit you neatly into a stable orbit for the altitude you are at when you switch off... which orbit is that then? Perfectly circular for that altitude perhaps? Okay - but at what inclination? Are you going east or west?
Perfectly circular with your initial vector in the plane of the star's rotation so that your orbit has a non-negative dot product to the rotation of the local star. Will that do? If my basic solar system formation notions are accurate, that should usually keep you from dropping out of PV as a viable kinetic weapon.

As for non-physicality, didn't we jump out of physically solid concepts when we started using the dominant local gravity well as a key concept? Or maybe not, if it really just runs off the local gravity gradient.
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Old 06-17-2009, 01:52 PM   #22
Fred Brackin
 
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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Originally Posted by Ulzgoroth View Post

As for non-physicality, didn't we jump out of physically solid concepts when we started using the dominant local gravity well as a key concept? Or maybe not, if it really just runs off the local gravity gradient.
Not the locally dominant gravity well. The nearest source of frame dragging. I mean if soem body is actually dragging space-time along with it surely that's enough to effect your PV drive when you're not actively using pseudo-thrust.

Really, you can try and complicate PV all you want but it still works better (for adventure purposes) than newtonian drives. Those are much more complicated to deal with in game terms even if all you have to do is read a physics textbook. They're also childishly simple to turn into weapons.
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Old 06-17-2009, 02:06 PM   #23
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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you switch PV on and go up to 1,000 miles again. Repeat.
I get it. For some reason, I was thinking the PV was on constantly. I should know better, since we used the same trick to create planetbusters in D&D with the Dimension Door spell.

Certainly the PV drive is non-physical. It's handwavium to avoid some of the problems with Newtonian drives while also trying to avoid the handwavium of the other FTL concepts. Which is why I've been puzzling over the distinction between a PV drive and a "hyperspace" drive. PV leaves you in "normal space", of course. So what does that really mean? What's less "hyper" about PV?
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Old 06-17-2009, 02:23 PM   #24
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

Wouldn't the nearest source of frame dragging be the nearest rotating non-massless particle of any sort? Not that I'm all that up on my relativity, but I don't see any evidence of magic cut-off thresholds.

As for the superiority of PV for adventuring, that's pure subjectivity there. At the very least you'll have to specify what sort of adventuring in what sort of setting before such a statement is meaningful.

As far as simplicity, Newtonian drives are quite easy to understand and semi-newtonian reactionless even more so, given a minimal grasp of physics (Which grasp is very non-uniformly distributed. Practically everyone I know can at least do basic mechanics.), where as PV drives require either all this hunting around for a satisfactory set of mechanics, or deliberately refusing to address certain questions.
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Originally Posted by Anaraxes View Post
Certainly the PV drive is non-physical. It's handwavium to avoid some of the problems with Newtonian drives while also trying to avoid the handwavium of the other FTL concepts. Which is why I've been puzzling over the distinction between a PV drive and a "hyperspace" drive. PV leaves you in "normal space", of course. So what does that really mean? What's less "hyper" about PV?
For one thing, the fact that it's not necessarily FTL? PV drives are a substitute for real-velocity reactionless drives when you have a problem with c-fractional kinetic bombardment. Your FTL drive can be PV if you want, but most of them are significantly harder to twist into weapons than sublight drives in the first place.
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Old 06-17-2009, 03:07 PM   #25
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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Originally Posted by Ulzgoroth View Post
Perfectly circular with your initial vector in the plane of the star's rotation so that your orbit has a non-negative dot product to the rotation of the local star. Will that do? If my basic solar system formation notions are accurate, that should usually keep you from dropping out of PV as a viable kinetic weapon.
Fair enough, and sounds both good and sensible. But you'll still end up in situations where you don't want to be in that orbit; for rendezvousing with excitingly spooky derelicts and so on..... and your PV drive simply won't cut it to make the trajectory changes you want.

All I'm really driving at here is that the deeper your handwavium goes, the longer you are managing (hopefully) to stave off the point where you have to say "look, it just works, okay?". I guess all of us that post on threads like this one get a kick out of pushing that point to see where we can go with it.... but I'm not sure it'll ever be possible to come up with an entirely "player-proof" technical architecture. The loose threads will always be there for the really annoying players to start unpicking things with... or alternatively we go totally hard science, and create the most boring campaign in the history of the world. ;o)

Of course - if I'm wrong, and we can come up with the player-proof and entirely consistent superscience concept between us, then perhaps we should be rushing to the patent office instead of chatting about it on an rpg forum! (And then let's all meet up for a beer round Tau Ceti in a few years time, eh? First round is on me.).

Speaking seriously for a moment - I do genuinely think there is a real value in bright and imaginative minds (like wot we have, naturally) working through ideas like this with rigour, scepticism, and yet still an openness to possibility. We could be the only people in the world doing it - at least to the same level of serious consideration of the fantastic. You never know. Somewhere in it all could be the key to something real, and entirely world changing. Keep watching the skies.

Meanwhile - back to the games!

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Originally Posted by Fred Brackin View Post
Not the locally dominant gravity well. The nearest source of frame dragging. I mean if soem body is actually dragging space-time along with it surely that's enough to effect your PV drive when you're not actively using pseudo-thrust.

Really, you can try and complicate PV all you want but it still works better (for adventure purposes) than newtonian drives. Those are much more complicated to deal with in game terms even if all you have to do is read a physics textbook. They're also childishly simple to turn into weapons.
Oh don't get me wrong, I agree with you entirely Fred. My own PV drive is working just fine in my campaign - I added the handwave that near to a source of significant space-time curvature (or source of frame dragging if you prefer) it can couple itself to that source and exchange momentum in the manner of a maglev type system........ but that really is just to let me sweep these issues of velocity vectors under the carpet.

Two out of my four regular players were on the same degree course as me (Aeronautics and Astronautics) - that's how I know them - and foolishly I thought that this would mean they'd get the same enjoyment as I do from mucking around with this superscientific detail. But no! In a game we played a couple of years ago I included a lovingly engineered antimatter powered starship, with pages of spreadsheets to prove that it might just work..... and they gave it little more attention than a "nice ship, how many plasma pistols can I carry?".

Sigh. Players, eh? :oP (And ahem, cut me some slack on the inclusion of plasma weapons in a hard science game, won't you? I just like the "pew pew" sound they make.....)

Still - it was a valuable lesson in GMing I reckon (or at least it was for me, it may well be obvious to you guys). The first criteria for a good rpg space drive has to be "is it fun?". My comments about irritating players is really for comedic effect more than because I really have trouble with that - as long as you make the game entertaining, in my experience they'll happily swallow huge mouthfuls of improbability, cliche, and unreality.

And at the end of the day - there's probably a fair amount of fun to be had in telling stories about relativistic planet killers and other Horrors of the Modern Age(TM).
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Old 06-17-2009, 03:36 PM   #26
Fred Brackin
 
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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Oh don't get me wrong, I agree with you entirely Fred. My own PV drive is working just fine in my campaign - I added the handwave that near to a source of significant space-time curvature (or source of frame dragging if you prefer) it can couple itself to that source and exchange momentum in the manner of a maglev type system........ but that really is just to let me sweep these issues of velocity vectors under the carpet.

Two out of my four regular players were on the same degree course as me (Aeronautics and Astronautics) - that's how I know them - and foolishly I thought that this would mean they'd get the same enjoyment as I do from mucking around with this superscientific detail.
Out of 4 players I have (in different groups) who currently or formerly worked at the Kennedy Space Center I have one(maybe) who cared about how the drive worked. Even with him it may been more that he was familiar with the general PV concept.

To be fair, another one got why the total conversion plant used water as fuel instead of liquid hydrogen and why it split it into oxygen to go to main propulsion and hydrogen for the secondary power core.

She was also appropriately worried when I told her that without the secondary power core there was no power for the radiation shielding.

Some of this was not surprising, she's actually a life sciences type. The other's are actually IT people rather than literal rocket scientists. Plenty of Master's degrees to go around though. The fellow who works at NASA has 2. :)
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Old 06-17-2009, 04:58 PM   #27
Timolas
 
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

Go figure, eh?

I probably should have added that, of the three of us on that course, I was the one that only just scraped through while the other two cruised it. That may or may not be significant.... (of course I like to believe that this was entirely because I was concentrating on more important things, like What Is A Hyperdrive? Clearly that must have been the case. Oh yes. Um. Oh dear.)

Even more worrying though; one of the other two has since displayed a disturbing ability to apply his monstrous brain (and I do truly mean monstrous - it can bellow radioactive breath and everything) to munchkinism.

Oh.

My.

Lordy.



In other news: what is a hyperdrive? :oD

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Originally Posted by Anaraxes View Post
Certainly the PV drive is non-physical. It's handwavium to avoid some of the problems with Newtonian drives while also trying to avoid the handwavium of the other FTL concepts. Which is why I've been puzzling over the distinction between a PV drive and a "hyperspace" drive. PV leaves you in "normal space", of course. So what does that really mean? What's less "hyper" about PV?
As I understand it - that point about the normal space versus some other space really is the main difference; the rest is just colour (interesting colour, but colour nonetheless). A PV drive will usually let you interact with objects that aren't operating in PV drive - or at the very least you are able to see them and maybe shoot laser beams at them.

In most versions of a "hyperdrive" on the other hand, from the other dimension / universe / thingy that the drive puts you into, you only have very minimal interaction with objects that aren't also in hyperspace - and in many cases not even then either (the classic blind unsteerable variety - which includes Traveller's Jump Drive).

Of course any particular stardrive can be called a hyperdrive, regardless of how it actually operates - but following GURPS terminology, I'd argue that if you had a hyperdrive where the ship in "hyperspace" could still see and interact with objects in normal space (as per PV drives), then really what you have there is some kind of warp drive, perhaps combined with a cloaking device.

The difference between a GURPS warp drive and a PV drive on the other hand? Not much more than what your speedometer goes up to, I would say. An FTL warp drive that doesn't operate in some sort of PV fashion is asking for the planet splitter threat to step once more into the limelight, this time with bells on.
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Last edited by Timolas; 06-17-2009 at 05:06 PM.
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Old 06-17-2009, 09:50 PM   #28
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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Originally Posted by Ulzgoroth View Post
PV drives are a substitute for real-velocity reactionless drives when you have a problem with c-fractional kinetic bombardment.
Is that why you use them? For me the appeal is more that they are more plausible currently than reactionless drives at all, but still allow meaningful interstellar speeds without butting up against the rocket equation.

If PV turns out to be possible, it will be surely be utilized because it allows engines with reasonable mass thrust ratios and craft with achievable delta v to effectively acheive interstellar speeds; not because it is difficult to weaponize.
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Old 06-18-2009, 09:48 AM   #29
Fred Brackin
 
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

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Is that why you use them? For me the appeal is more that they are more plausible currently than reactionless drives at all,
Oh no. I use them because in normal PC situations they avoid huge amounts of math. Trying to set up interception situations (even a near-intercept to permit beam weapon combat)for two ships with constant acceleration is a mess.

Mostly you end up with situations where two ships (or two fleets) zoom past and try and obliterate each other in passing.

If you don't want to go with PV and still want some sort of cinematic-looking combat you'll have to go with something like Babylon-5 where ships pop out of hyperpace already within weapons range of each other.
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Old 03-06-2011, 01:28 PM   #30
vicky_molokh
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Default Re: [Spaceships] Actually GMing a world with Pseudovelocity drives?

An idea for another solution to the question of kinetic/potential energy and similar stuff - how about a PV drive:
  • Has a an effect that makes this pseudo-velocity semi-persistent - it 'bleeds off' gradually if the drive is turned off (or if it exceeds the drive/ship's max PV), and it is reduced or redirected significantly on a collision (e.g. PV loss/deflection is 50× the value of normal velocity's loss/deflection).
  • Has an effect that neutralizes 'real' velocity opposing its movement direction first, and only then starts giving PV. So if objects moves downward at 10 m/s, the PV drive of 1m/s² will spend the first 10 seconds neutralizing real speed, and spend the next 10 seconds giving PV upwards.
  • (Optional) A PV drive grants a speed that is pseudo in a large fraction, but not completely. E.g. a drive/ship combo rated for 50mps of PV actually attains a speed of 5 'real' mps and 45 pseudo-mps.
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