Choosing 4E Spaceship Propulsion

[hal]

What might be interesting, is trying to adapt GURPS SPACESHIPS to TRAVELLER 2300 AD (unlike the title, it isn't the Traveller Line of ship building rules nor is it the Third Imperium or even pre-third imperium). The idea that ships can only move via stutterwarp to a distance of 7 light years (or thereabouts) has very specific ramifications for travel in the universe as for the near earth interstellar space.

Best of all? Stutterwarp permits ships to move via pseudo velocity that results in the ship stopping cold when the drive stops cold, and keeping up a specific speed via hexes, if the drive is moving. The drive shuts down (becomes inefficient) when within a given distance of a gravity well (making it useless for landing on planets etc).

For what it is worth, the entire 2300 AD line of products can be purchased on a CD from FAR FUTURES ENTERPRISES for $35 plus shipping and handling.

The fun part will be adapting the stutterwarp for use with GURPS SPACESHIPS, but it should be doable. Click on the link below to view what is available on the CD.

2300 AD

PS - almost forgot. STAR CRUISER contains the information required to build ships in the 2300 AD universe - as well as rules for running battles. The star cruiser rules might help create the stuff you need for the stutterwarp conversion for GURPS SPACESHIPS.

[nondescript handle]

Originally Posted by hal

[...] The idea that ships can only move via stutterwarp to a distance of 7 light years (or thereabouts) has very specific ramifications for travel in the universe as for the near earth interstellar space. [...]

It was 7.7 ly. The problem is that these ramifications are very different from what was presented in the 2300AD source material.
With 7.7 ly routes and real-world star positions you don't get "arms", you get a "web."

See for example: http://evildrganymede.net/2012/02/13...near-star-map/

[gruundehn]

In the Lensman series E.E. Smith gave the speed in Parsec per hour, typically 60. This gave the entire series a galactic scope, later inter-galactic.
I am trying to get published as a Sci-Fi writer myself and the system I use is a "Jump" drive. Each ship can jump up to 4 Parsecs at a time but there has to be a long wait between jumps as the effects mess with electronics and the Human nervous system. Your ship points at where the target star is NOW and hit a velocity that gets you to the target system and away from known hazards. The crew must make HT rolls (to use GURPS terms) in order to recover and until they do they are completely "out of it" and vulnerable. The normal space drive can only get up to about .5G so that it takes a long time to get from the entry point to the target planet / spaceport. This sort of drive system is instant in the sense that jumping from one system to another takes no time but recovering from the jump takes days - depending on how often you allow a HT roll. Fail it too often or jump too soon and you start getting serious mental Disadvantages. Or the ones you have get worse. This can give you the plot elements of having the villians waiting at known places where spaceship from specific systems will be arriving at and attacking while the incoming crew is dazed from the jump effect. Smart crews would try to avoid this by entering at unexpected locations - a Navigation Roll at a penalty - but this can all be up to you.

[gruundehn]

Just remembered two other systems you might use.
First: A. Bertram Chandler used a time / space drive. You went "foward in space and backward in time" and you had to be very careful about tuning the system because if you hit the point where time stopped, then you stayed in place forever. So yu could travel a great distance at a slow speed but got to your location fairly quickly as the time was reduced.
The second system, I forget the author who came up with this one, was that you went back in time until your destination was extremely close, went to your destination and then shifted back to your "normal" time.

[Fred Brackin]

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"?

The campaign was set far from Earth in a "frontier" area and I rolled up "sectors" using the First In rules.

I was also using a relatively "realistic" frequncy for inhabitable planets and came up with an average distance of 30 parsecs between them.

This number resulted from a brute fiorce mass calculation I did long ago from Space 1e. I was satisfued at the time that at least it was not too optimisitc.

I did not look at Earth's neighborhood closely but my system kicked out Alpha Centauri, Barnard's Star and Sirius. I would expect the first usable line to go to Tau Ceti off-hand. Finding an inhabitable planet at Tau Ceti would be possible but in my estimation improbable.

So actual distances covered by the Gloria Monday and her sister ship, the Tuesday Weld were very large by Traveller standards. It fit my ideas of realsim better.

An important point in the way I did things is that ships normally rode jump lines to as close to the target star as they could stand. After consultaiton i came up with a distance of 0.1 AU. This also aided technobabble concerning pirate ships hiding in the coronal glare.

So while the trip from the starting planet to the first jump line may have averaged abotu 0.5 AU, later jump line chnages only averaged 0.1 AU with another average 0.5 AU to the target planet. Total distance for a 5 jump transit (which usually looked rather zig-zaggy) only added up to 1.5 AU or less thus producing that 1 week average trip.

So trip time wasn't even linear with jump number.

[Fred Brackin]

Originally Posted by Seneschal

Does that negate the need for SM+5 ships in you setting?

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?

No, there were fighters. It was possible for small ships to destroy big ships and this made small ships quite attractive at any combat range that their pilots could stand to sit in the cockpit for.

Above that there was a class or "Assault Transports" that used a similar-sized engine core to the usual small merchant ship but in a ship half the size with only 1/10th the cargo space. After the War (there's always an After the War) a lot of Assualt Transports ended up as pirate ships which wanted to capture merchanters for spare parts.

I simply assumed that the drive had a normal G-rated flight capability useful in atmosphere but I was trying (quite hard) to produce small cheap ships that were simple to operate even on shoestring budgets.

The first group of PC's iconic ship was the Gloria Monday and (heavily used) it had a fair value of c. $500,000 credits and could break even charging what were very close to UPS rates for shipping. I seem to reall something like $10 per cubic foot, but hey I really was trying to make rag-tag groups in small shoips practical. With Traveller prices (30x as much or more) as a counter-example even a single Free Trader needed to be run as a small-to midsize LLC and not a loose partnership betwen a couple of buddies.

[hal]

Originally Posted by nondescript handle

It was 7.7 ly. The problem is that these ramifications are very different from what was presented in the 2300AD source material.
With 7.7 ly routes and real-world star positions you don't get "arms", you get a "web."

See for example: http://evildrganymede.net/2012/02/13...near-star-map/

Thanks for the clarification on the distance permitted - as I wasn't about to dig up my 2300 material for this post ;)

That having been said, I visited the webpage you listed above and thought that the Evil Doctor Ganymede (sp?) did a bang up job examining the 2300 universe in light of recent advances regarding astronomy. Mind you, I can't verify whether he's right or wrong, but take on faith that he's right. :)

Which brings me to the next point. If using the documentation of what stars are where in the 2300 universe, and used the concept of stutterwarp in general - it brings about a case of "with foundation comes form" (ie build the basic universe rules and draw your plots from that building). WIth the new revised data (along with Astrosynthesis 2.0 - or 3.0 as it is now getting up to), the GM an have a fair bit of fun creating the form of his universe, and then watching what is implied, unfold as if written for him.

I'm going to have to dig up the material I can find on the stutterwarp itself, as it basically results in a pseudo-velocity like arrangement permitting a ship to move X hexes per turn, as well as having a zero velocity once the drive shuts down. The ship building rules are NOT the same as for use with GURPS, but one should be able to build GURPS analogs to some extent. ALmost makes me want to do so myself - but for one thing.

FUTURE ARMADA series starships has caught the eye of my one player, and he now wants a reactionless drive FTL style campaign that utilizes those deck plans for the ships. This in turn requires that I forgo the colony style campaign I was going to run set on Mars using Transhuman space style ship construction and combat. <shrug>.

[Seneschal]

'Scuse me for not replying, I had an exam-day.

Originally Posted by Daigoro

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.

Looks like a good source of inspiration, even if the scale is much bigger than what I'm planning. I did plan on treating psionic powers as vital components of modern communication and transportation. I also wanted, kinda like you, to make psionics control gauge bosons (force-carrier particles): photons for Ergokinesis, probably Higgs bosons for Psychokinesis (though where this crosses into pure gravity control and Warp via wormholes is hard to determine), but then it started to get tricky with gluons (there is no GURPS source for nuclear-force-based psions, since they would be a can of worms, plus they wouldn't have very diverse powers), and it also doesn't explain ESP and probability-alteration, so I'm still on the edge about the concept.

Originally Posted by hal

Best of all? Stutterwarp permits ships to move via pseudo velocity that results in the ship stopping cold when the drive stops cold, and keeping up a specific speed via hexes, if the drive is moving. The drive shuts down (becomes inefficient) when within a given distance of a gravity well (making it useless for landing on planets etc).

As much as it irks me, it seems that Newtonian movement and space opera aren't really meant to be, especially because I really like the implications of these fixed-speed "boost drives" that stop immediately after shutting off engines. I also think I finally understand what the hell those "quarter impulse" and "full impulse" in Star Trek mean, and why their ships lose all speed as soon as they blow a fuse.

Well, the real answer is "because screenwriters hate physics", but pseudovelocity works just as well.

Originally Posted by gruundehn

A. Bertram Chandler used a time / space drive. You went "foward in space and backward in time" and you had to be very careful about tuning the system because if you hit the point where time stopped, then you stayed in place forever. So yu could travel a great distance at a slow speed but got to your location fairly quickly as the time was reduced.
The second system, I forget the author who came up with this one, was that you went back in time until your destination was extremely close, went to your destination and then shifted back to your "normal" time.

I think something like this would suit a super-advanced godlike alien race (quite a few of which I plan on introducing in the setting, acting aloof, playing intergalactic games and ignoring the fledgeling protagonist species beneath them), but they would also come with mind-bending time-travel and paradox issues if widely available.

I also get the feeling that the people aboard a ship using the first kind of drive would get to experience the entire trip real-time, even if an outside observer sees the ship travelling instantly. The second one is a bit more plausible when you take into account an expanding universe.

In both cases, you'd get trans-temporal warfare like in Baxter's Xeelee Sequence, which greatly complicates things.

Originally Posted by Fred Brackin

No, there were fighters. It was possible for small ships to destroy big ships and this made small ships quite attractive at any combat range that their pilots could stand to sit in the cockpit for.

Above that there was a class or "Assault Transports" that used a similar-sized engine core to the usual small merchant ship but in a ship half the size with only 1/10th the cargo space. After the War (there's always an After the War) a lot of Assualt Transports ended up as pirate ships which wanted to capture merchanters for spare parts.

I simply assumed that the drive had a normal G-rated flight capability useful in atmosphere but I was trying (quite hard) to produce small cheap ships that were simple to operate even on shoestring budgets.

The first group of PC's iconic ship was the Gloria Monday and (heavily used) it had a fair value of c. $500,000 credits and could break even charging what were very close to UPS rates for shipping. I seem to reall something like $10 per cubic foot, but hey I really was trying to make rag-tag groups in small shoips practical. With Traveller prices (30x as much or more) as a counter-example even a single Free Trader needed to be run as a small-to midsize LLC and not a loose partnership betwen a couple of buddies.

I'm pretty sure I'll go with your drives, the concept fills pretty much all the requirements for accessible, high-traffic space travel, and solves the problem of kinetic weapons. I really wanted spaceships that weren't "eggshells with sledgehammers", in fact, I tweaked the dDR values a lot (the condition I wanted to achieve was that, to kill a ship, you need the main gun of a ship one SM bigger (or a same-SM ship with a spinal gun)). I also think the $500,000-per-heavily-used-small-ship is not too much off-target if you want everyone and their mum to have a spaceship (my players' SM+8 tramp freighter with stardrive has a resale value of ~10 million, but I might lower prices even further.

I had another question though - how did you handle multiple-system engines? Do you allow, say, a SM+5 bomber to equip 4 PV systems, and get four times the movement points (if we use Spaceships 3 tactical rules) than its high-SM target? Or did you put a limit?

[Fred Brackin]

Originally Posted by Seneschal

I had another question though - how did you handle multiple-system engines? Do you allow, say, a SM+5 bomber to equip 4 PV systems, and get four times the movement points (if we use Spaceships 3 tactical rules) than its high-SM target? Or did you put a limit?

This actually predated Spaceships by quite a bit and I haven't trried to convert to Spaceships. I not only had all the stuff already done up for Ve2, i had a really nie computer program (GVB) that made designing in Ve2 at least as fast (if not quite as simple) as using Spaceships.

If I had been working within the scale/detail limits of Spaceships (which I find not entriely satisfactory) I'd have done some things differently.

For the Merchant ship/Assualt Transport trick I'd have made the military ship a full SM smaller and made the 1 drive system of the merchant ship equal to 3 drive systems for the military one.

[Seneschal]

Originally Posted by Fred Brackin

This actually predated Spaceships by quite a bit and I haven't trried to convert to Spaceships. I not only had all the stuff already done up for Ve2, i had a really nie computer program (GVB) that made designing in Ve2 at least as fast (if not quite as simple) as using Spaceships.

If I had been working within the scale/detail limits of Spaceships (which I find not entriely satisfactory) I'd have done some things differently.

For the Merchant ship/Assualt Transport trick I'd have made the military ship a full SM smaller and made the 1 drive system of the merchant ship equal to 3 drive systems for the military one.

That's okay, you don't have to think in Spaceship 4E rules. I merely wondered if one could improve top speed by getting a bigger/more powerful engine, or if the limit was an absolute one (i.e. limited to the source of the propulsion). Like how lightsails are limited by solar wind speed (~250 mps at 1 AU). But I think it's better with variable drive performance.

Maybe I could divide them into Cheap (200 mps), Good (250 mps), Fine (300 mps) like all equipment. Assuming they all require constant electricity, the most one could fit inside a spaceship is four or five (assuming you don't want to run out of space or buy multiple power plants) which would give a speed range of 200 - 1500 mps. It's not a big enough difference to run into fast-pass problems and space travel that is too short.