Choosing 4E Spaceship Propulsion

[Fred Brackin]

Originally Posted by Seneschal

This sounds just about right, but I'm not sure how a fixed speed (if I understood correctly, PV ships have no acceleration, they instantly achieve ~300 mps or so, and come to a full stop just as fast) would work in spaceship combat, especially the tactical variant discussed in Spaceships 3.



This would greatly simplify things, but with the multitude of different cultures and alien species I plan on having, it would be a bit weird if everyone used lasers and only lasers. It also makes ramming/boarding infeasible.

A fixed speed will give you a number of hexes per turn which is exactly what the tactical variant wants.

It also makes deep space battles of types other than fast passes possible. If you're on Earth and a fleet from Mars is headed your way at 1G constant there is virtually no way you can "rendevous" with them to maneuver against each other unless you wait until they are virtually on top of you.

Do the math. If the two planets are at closest approach it's only a 2 day trip at 1G. If Earth's interception fleet launches as soon as the Martian invasion fleet is seen to light it's engines the two will pass each other in 1 day just as the Martians are about to turn over and begin deceleration.

Unfortunately, they will be headed in opposite directions at over 500 miles per second or 1000 mps relative. With the longest range beam weapons in Spaceships they could fire at each other for no more than 200 seconds and maneuvering would be pointless.

With a maximum speed and rapid acceleration to it you can race out to meet them and still turn around and match their speed and direction. Maneuver battle becomes normal rather than extremely rare.

You don't have to have only lasers. Any beam weapon with "field-jacketing" to interact with the drive field in the correct way would do. This also allows you to play with the weapon's relative ranges. With just normal physics, almost no weapons except lasers are useful unless ships suddenly emerge from subspace or "de-cloak" well within laser range.

Barring such tricks or outrageously thick armor the laser-armed ships will kill the particle beam/whatever armed ships long before the latter get into their firing range.

You can also use missiles or even cannon shells with PV minidrives as outlined in my previous post.

For boarding you need a way to disable weapons and propulsion on your target ship without destroying it. I recommend an "emp torpedo" or similar device to achieve the desired effect. It's not a normal space combat result. Drifting space junk is the norm.

Space pirates would launch emp torpedoes at merchant ships justifying fancy flying and/or anti-missile weaponry on the part of the merchant ships. Logical merchant ships with the relative capabilities of 2012 cargo ships have little amusement value.

[Seneschal]

Originally Posted by Fred Brackin

A fixed speed will give you a number of hexes per turn which is exactly what the tactical variant wants.

It also makes deep space battles of types other than fast passes possible. If you're on Earth and a fleet from Mars is headed your way at 1G constant there is virtually no way you can "rendevous" with them to maneuver against each other unless you wait until they are virtually on top of you.

Do the math. If the two planets are at closest approach it's only a 2 day trip at 1G. If Earth's interception fleet launches as soon as the Martian invasion fleet is seen to light it's engines the two will pass each other in 1 day just as the Martians are about to turn over and begin deceleration.

Unfortunately, they will be headed in opposite directions at over 500 miles per second or 1000 mps relative. With the longest range beam weapons in Spaceships they could fire at each other for no more than 200 seconds and maneuvering would be pointless.

With a maximum speed and rapid acceleration to it you can race out to meet them and still turn around and match their speed and direction. Maneuver battle becomes normal rather than extremely rare.

You don't have to have only lasers. Any beam weapon with "field-jacketing" to interact with the drive field in the correct way would do. This also allows you to play with the weapon's relative ranges. With just normal physics, almost no weapons except lasers are useful unless ships suddenly emerge from subspace or "de-cloak" well within laser range.

Barring such tricks or outrageously thick armor the laser-armed ships will kill the particle beam/whatever armed ships long before the latter get into their firing range.

You can also use missiles or even cannon shells with PV minidrives as outlined in my previous post.

For boarding you need a way to disable weapons and propulsion on your target ship without destroying it. I recommend an "emp torpedo" or similar device to achieve the desired effect. It's not a normal space combat result. Drifting space junk is the norm.

Space pirates would launch emp torpedoes at merchant ships justifying fancy flying and/or anti-missile weaponry on the part of the merchant ships. Logical merchant ships with the relative capabilities of 2012 cargo ships have little amusement value.

Heh! So, it's actually better for space opera than Newtonian movement. I realize deep-space combat would be impossible normally, and I figured most conflicts would take place in orbit, but this sounds more exciting. It also allows any two ship to rendezvous regardless of their respective travel times, so stationary lurking pirates can always easily begin pursuit. Also, ramming could be used to force an enemy's engines to go down.

Does that negate the need for SM+5 ships in you setting? Generally, something like a fighter craft or drone wouldn't be necessary even in normal Spaceship rules, but if they don't have acceleration many times that of long-range vessels (e.g. a 3G chemical rocket compared to a 0.005G fusion rocket) they lose even their Handling advantage. Do they equip 4 or 5 PV drive systems, perhaps?

Also, you said that the PV drive activates after reaching orbit. If I were to use them, how would I handle atmospheric flight? Air-breathing jets?

[nondescript handle]

Originally Posted by Fred Brackin

[...]For FTL I used "jump lines". These from between any stellar bodies (or anythign else with a degenerate matter core) and had a useful length of 3.3 parsecs x the combined masses of the two bodies in terms of solar masses.[...]

You've mentioned this setup before, and I find it very interesting. Did you use real world data, or generated "sectors"?

Because with 3.3 parsec (10.76 ly) and the nearest 100 stars I've lost only a dozen or so of the Ms, and Gs (such as Sol) are almost as connected as Altair (it is quite crowded with possible routes). Maybe another formula works better for such a "small" volume.

[vierasmarius]

Originally Posted by nondescript handle

You've mentioned this setup before, and I find it very interesting. Did you use real world data, or generated "sectors"?

Because with 3.3 parsec (10.76 ly) and the nearest 100 stars I've lost only a dozen or so of the Ms, and Gs (such as Sol) are almost as connected as Altair (it is quite crowded with possible routes). Maybe another formula works better for such a "small" volume.

Maybe the formula could include "jump line robustness." For example, keep it as is, but if the resulting "length" of a jump line is double the actual distance between the stars, then the jump line has a Robustness of 2, etc. The exact effects of Robustness are up to the GM of course, but could include the maximum size of ship that can cross, the number of simultaneous jumps allowed, the speed of jumping ships, the reliability of the jump line, etc. This could even be extrapolated backwards, allowing jump lines with <1 Robustness, which would be very risky to cross.

[Seneschal]

Originally Posted by nondescript handle

You've mentioned this setup before, and I find it very interesting. Did you use real world data, or generated "sectors"?

Because with 3.3 parsec (10.76 ly) and the nearest 100 stars I've lost only a dozen or so of the Ms, and Gs (such as Sol) are almost as connected as Altair (it is quite crowded with possible routes). Maybe another formula works better for such a "small" volume.

Sorry, did you use a program to calculate that, or just looked up a list of nearby stars?

I get the feeling that the system seems to favour campaign maps where main "highways" are located between high-mass stars with practically uninhabitable systems. Something like the Pistol Star, that doesn't even live long enough to have planets, would be the lifeblood of galactic traffic, connecting with Sol-sized stars at 300-400 parsecs! Catch a ride between ~50 such stars and you've travelled through half the Milky Way! (with a week of intra-system travel between each "line", that takes about one year)

[vierasmarius]

Originally Posted by Seneschal

I get the feeling that the system seems to favour campaign maps where main "highways" are located between high-mass stars with practically uninhabitable systems. Something like the Pistol Star, that doesn't even live long enough to have planets, would be the lifeblood of galactic traffic, connecting with Sol-sized stars at 300-400 parsecs! Catch a ride between ~50 such stars and you've travelled through half the Milky Way! (with a week of intra-system travel between each "line", that takes about one year)

You could posit a "sweet spot" in which the interplay of hyperspatial forces is sufficient to keep open a stable jump path, but not so powerful that it rips travelling ships into their constituent atoms or converts them into tachyons. Continuing somewhat from my previous post, jump lines between stars whose combined masses exactly match the distance between them (ie, "Robustness" or Strength of 1) are optimal, allowing fast and safe travel. Stronger paths require heavily reinforced ships, while weaker paths can drop you out with little warning. Shorter paths would be preferable over long ones if the travel time of a jump path varies with its length, rather than being fixed.

Or you could forget the formulaic approach, and simply assign jump paths arbitrarily, biased towards connecting interesting systems. After all, hyperspace is not a set of rules that you need to abide by, but a tool in your worldbuilding kit. Use it however you want to promote the kinds of stories you want to tell.

[Seneschal]

Originally Posted by vierasmarius

You could posit a "sweet spot" in which the interplay of hyperspatial forces is sufficient to keep open a stable jump path, but not so powerful that it rips travelling ships into their constituent atoms or converts them into tachyons. Continuing somewhat from my previous post, jump lines between stars whose combined masses exactly match the distance between them (ie, "Robustness" or Strength of 1) are optimal, allowing fast and safe travel. Stronger paths require heavily reinforced ships, while weaker paths can drop you out with little warning. Shorter paths would be preferable over long ones if the travel time of a jump path varies with its length, rather than being fixed.

If nondescrip handle is right, and the 3.3 parsec equation gives a too crowded galaxy, this might be a good idea. Ok, so hyper-robust lines would require HT rolls, with ships suffering damage, possibly even system failure, and too-weak lines requiring Navigation (Jump Line) rolls or being kicked out half-way.

For this to be any penalty at all, line navigation would have to be non-routine (e.g. if you fail, your margin of failure drops you off with an AU or two of drift at your destination, prolonging your intra-system cruise time, critical failure indicates a jump mishap with more serious consequences).

The problem is that, unless you're in the centre of the galaxy, a network of G-class stars precisely 3.3 parsecs from each other will be a rare occurrence - you'd have to take detours through lighter/heavier systems (or risk injury/delays).

[vierasmarius]

Originally Posted by Seneschal

The problem is that, unless you're in the centre of the galaxy, a network of G-class stars precisely 3.3 parsecs from each other will be a rare occurrence - you'd have to take detours through lighter/heavier systems (or risk injury/delays).

Well, you could allow jump lines in the range of, say, Strength 1-3 to be traversible without penalty. Just fiddle with the numbers until you get a nice range of useable and interesting jump paths.

EDIT: Oh, just had another idea. To further bias results towards short jumps rather than long ones, you could make the number of rolls (navigation, ship HT, etc) based on the length of the jump. So even if two jumps have the same Strength, the longer one is riskier because there are more opportunities for failure. Alternately, roll once per jump, but include a penalty based on the path length. If properly balanced, this means jumps between massive stars will always be riskier than between smaller ones - if the path is long enough to be stable and not over-powered, it will be long enough to carry addition penalties.

[nondescript handle]

Originally Posted by Seneschal

Sorry, did you use a program to calculate that [...]

Yea, I modified a very simple program I already had for that.
Very, very raw output (i.e. unedited node maps) for "combined mass times 10.76ly" and a 2300AD-inspired "combined mass times 7.7ly" for the RECONS data (from Evil Dr. Ganymede) can bee seen here: http://flic.kr/ps/2bmevV

[Daigoro]

Originally Posted by Seneschal

I've decided to thoroughly flesh-out the setting before we start again, going with the Sci-Fi kitchen-sink approach, and then taking out elements that don't fit the tone. Now, we've agreed to keep it (relatively) light-hearted and adventurous, with very high TLs (around TL 11 mostly), rayguns, space pirates, interstellar kingdoms, psionic powers, that sort of thing, but we also wanted to establish some ground rules and keep it consistent. Less space-fantasy and more far-future-tech advanced enough to be miraculous.

If you have a look at King's Eclipse in my sig, you might find something useful. It's a collaborative setting a few of us on here did some work on a while ago, and it fits most of your criteria.

The main fantasy part of it is the psychic sentient black hole entities, but everything else in your list is in there.