[Spaceships] Designing Hyperspace / FTL for space opera (and implications)

[Humabout]

Hyperdrive:

A Babylon-5 style hyperdrive/jump gate setup could work without impacting things like smuggling too greatly, if smugglers have access to hyperdrive ships. The potential for hyperdrive-capable ships eleminatest eh threat of blockades against all but non-hyperspace capable ships (presumeably cheaper private vessels and smaller military vessels).

Depending on limitations on the hyperdrive, Dune-like transport ships could easily arise. One enormous hypership carries lots of smaller ships ANYWHERE while passage via jumpgate is used for commercial or public conveyance.

Jump Drive:

While a jump drive may take the form of those suposed by Origin in the Wing Commander games, it is also possible for them to follow Asmiov's concept of a hyperdrive. In this case, they function anywhere sufficiently distant from large gravitational fields (read: star systems) and work instantly. Unfortunately, they are not the most accurate things in the galaxy, so multiple shorter jumps are required to minimize the risk of jumping to a point so far off course you can't determine your location in space (and thus cannot accurately plot your next jump). Advanced computations are required to tell the jump drive how to opperate, and these can take anywhere from hours to weeks, depending on the level of computing technology available (this was a huge advantage for the ship in Foundation's Edge and Fountation and Earth), and naturally, because of galactic drift, inaccuracies in each jump, and for storytelling reasons, new computations must be made after each jump.

Again, planet-busters cannot just pop out of hyperspace because emerging within a solar system is too risky because of inacuracies in the jump. In terms of combat, hyperdrives yield a greater need for strategy and timing because once in, it will take time to get out or reposition. Here, the quality of the drive is far less important than the speed of the navigational computer (although a more accurate drive never hurts).

It also would mean that you have to approach planets at relativistic speeds, so while the 1,000-light year jump takes literally zero time, the trip from your 50-AU orbit to Earth's 1-AU orbit might take a month (assuming a constant 1G acceleration for half the trip, a 180-degree rotation, and another 1G deceleration burn).

I realize these don't give many implications, but just some thoughts. Personally, I like the idea of mixing jump gates/hyperspace and asmovian hyperdrives (jump drive). both can be modeled to have advantages over the other and could represent two different civilizations' approaches to FTL.

[Pragmatic]

I prefer a two-tier system.

A bunch of "wormhole"-connected systems, where travel takes a normal sublight engine. There may be anywhere from three to three-hundred systems in each "network," and any particular system may have one to five or more "wormholes." (More along the lines of the "Lost Fleet" universe than the "Starfire" universe. Not instantaneous like Starfire, but not as long as the Lost Fleet.)

And a "jump drive" that allows jumps of medium-range distances, taking about a week. (Think "BattleTech" or "Star*Drive.")

Thus, stellar empires will tend to grown quickly through the "wormhole networks," but there's the possibility of "jumping" to a nearby network. "Jumpships" would have to carry additional systems (batteries and jump drive and what-not), so would either have unarmed "carrier" ships, or weak combat capabilities.

[Pomphis]

Originally Posted by Molokh

I also found that Reactionless drives seem too cheap/efficient/fast-accelerating on average when compared to Reaction drives of the same TL.

I'm not sure I 'get' what is so special about the Probability Drive.

a) Yes. But have you actually run the numbers for interplanetary trips with reaction drives ? We are talking months.

b) Only that it is a canonical jump drive that does not need jump points.

[weby]

In my own scifi setting there are actually 3 types of FTL travel in use.

The normal travel distances are quite long with distances of hundreds of pc between inhabited worlds being normal.

Jump gates:
These are huge structures consisting of huge powerplants and capacitors due to high power requirement. They allways work in pairs and have a 30pc maximum range. The need to have the large gate at both ends makes these the feature of the "main routes" where they are in chains.
Benefits:
-Move to target instantly
-No FTL drive needed in the ships traveling
Disadvantages:
-Need the huge structures. (Smallest possible gates are 20 000 tons)
-The huge energy demands put a limit on mass transmitted at one time and mass transmitted over a given time period for given gate.

Warp(microjump) drives:
Are the drives used by most exploration and military craft. They are bulky,heavy,Very expensive and very mass sensitive but capable of moving the ships at 5pc/day(typcical heavy warship) to 20pc/day(fast courier/scout).

Also used in the main ship to ship weapons as that is the only thing capable of catching a warp drive ship..

Benefits:
-Move fast where there are no gates.
-Huge combat advantages from ability to move at FTL speed in combat.
-Can operate at FTL speeds anywhere outside atmospheres.
Disadvantages:
-Require huge machinery(about 20% mass for a heavy warship 80% mass for a fast courier)
-Very expensive due to manufacturing difficulty.

Hyper drives:
These are used by everything else. They are small(typical requirement 0.2-1% of ship mass) and fairly cheap. They can move ships at 0.2pc/day to 1pc/day depending on the generation of the drive. They cannot be used close to large masses.

They are used in places where the gates do not go and for bulk non persishable cargoes even along gate routes as transporting things that way basically costs nothing except time.

Also most military craft have hyper drives as backup and even military smallcraft routinely have hyperdrives.

Benefits:
-Very Cheap
-Does not take much space/weight.
Disadvantages:
-Slow
-Easy to track. The source and target vectors of any jump is detectable for weeks afterwards in most cases from quite far away. (Military craft, pirates and smugglers can activate several hyperdrives at same time confusing the track a lot, making it very hard, but not impossible)
-You cannot change destination or see outside when traveling. (Though you can drop out of hyper anywhere along the plotted route)

FTL communication along the Jump gate route is very fast. The gates have constant high bandwith link between them. Thus messages travel at maybe 300pc/second along such routes.
Elsewhere the speed is slower:
-the high bandwith communications and imaging FTL radar travels at 10pc/day
-Low bandwith communications and FTL radar travels at 30pc/day.

The low bandwith communication is basically only good for simple text messages(think telegrams). The high bandwith is enough for several channels of HD video.

FTL communication ranges are long though, a (large)backpack sized communicator can reach 100pc(high bandwith)/1000pc(low bandwith) shipboard systems way further.

[vicky_molokh]

Originally Posted by Pomphis

a) Yes. But have you actually run the numbers for interplanetary trips with reaction drives ? We are talking months.

But they have unlimited delta-V. They're a better investment in the long run. Thus they should somehow be worse elsewhere. As of now, they aren't terribly expensive, yet they seem better than reaction drives in all areas.

[thtraveller]

Originally Posted by Pomphis

a) Yes. But have you actually run the numbers for interplanetary trips with reaction drives ? We are talking months.

Maybe for the outer planets at low TL. You can do Earth-Mars in 5 weeks at TL9 http://forums.sjgames.com/showthread.php?t=56322

[David Johnston2]

Originally Posted by Molokh

But they have unlimited delta-V. They're a better investment in the long run. Thus they should somehow be worse elsewhere..

Not really. They're superscience. They don't exist as an alternative to more realistic drives, but as a replacement for them.

[Ulzgoroth]

Originally Posted by Molokh

But they have unlimited delta-V. They're a better investment in the long run. Thus they should somehow be worse elsewhere. As of now, they aren't terribly expensive, yet they seem better than reaction drives in all areas.

Reactionless drives are generally going to blow high-impulse reaction drives away unless you make them have significantly lower acceleration, or very expensive, because even high-impulse rockets almost never can have as much impulse as they'd like.

High thrust is another thing, though. A high thrust water-burning fusion torch gets 3g per system. The delta-V is a bit limited at TL10, but the thrust ratio is hard to beat (you'd need a high-thrust Orion or a high thrust water-burning antimatter plasma torch).

Since high-impulse is usually what matters for trade, the only place I can see fusion torches beating any kind of reactionless much is for ships that need planetary take-off capability.

[David Johnston2]

Originally Posted by Ulzgoroth

Since high-impulse is usually what matters for trade, the only place I can see fusion torches beating any kind of reactionless much is for ships that need planetary take-off capability.

Or of course, combat manuevering.

[vicky_molokh]

Originally Posted by David Johnston2

Not really. They're superscience. They don't exist as an alternative to more realistic drives, but as a replacement for them.

That's somewhat sad, as this essentially means that TL(x)^ > TL(x). It makes building a world where many technological solutions coexist in different niches much more difficult, because items of the same absolute TL no longer balance against each other.