Theoretical Sci-fi Physics.

[Malenfant]

Originally Posted by Anthony

Not really. A simple system consisting of an (extremely large) positive energy density in the floor, and an (equally large) negative energy density in the ceiling, wouldn't do much outside of the ship, and would generate a gravity field inside the ship. Such a field would not typically have an inverse square effect, it would be similar to the electric field between two charged plates.

I think that (or using wacky particles) is making it more complicated than it needs to be. We know of one pseudoforce (centrifugal) that creates exactly the effect we want, I think if you just say that there's some 'black box' that makes the pseudoforce that attracts everything to the bottom of the ship and leave it at that then that should work well enough (maybe the tech has to be physically located or concentrate at the 'bottom' of the ship too).

[Hilary_155]

Howdy again.

I am pretty sure I am going to use exotic particles now instead of hydrogen fuel for jump as well as for artificial gravity.

Rather than requiring jump fuel, ships will have large engines that stimulate exotic particles which in turn kick the ship into jumpspace.

I am also going to use a system of jump travel where stars propel the ships. Nuclear reactions in stars produce a particle not seen in our universe... they travel in Jump space. This is the missing neutrino mass that is expected from nuclear reactions in stars. Anyway, these particles travel super fast in jumpspace and 'push' ships from one star to another. It is up to the pilot to plot the right path and time the return to normal space... otherwise they could end up somewhere OTHER than near a star when they come back to normal space.

Stars would not slow down the ship as when they get half way there, they turn the jump bubble 90 degrees polar to those particles and they are no longer opaque to that force. A misjump could be a perfectly normal jump sequence only the pilot screwed up and they came out way far away from a star and must travel at space normal speeds to get back to civilization.

This would be the cheap jump engine. Expensive ones would allow the ships to move under their own power in jump space.

Additionally, the jump distance would not be restricted by the engine type, but a 2 or 3 or more parsec trip using the jump sail engine would require one hell of a good roll on the pilot skill. The farther the trip, the more any error is magnified. This means 1 parsec jumps are the norm (star to star). It also means stars would have regions of space where ships would queue up for jumps to other systems. They would have to put the system star at their back and aim at the destination star. So a system could charge a "lane tax' for these jump sail ships to enter the proper tram line to a specific destination star.

Thoughts?

[rasimus]

A few initial thoughts:
- Sounds like starships would spend a lot more time in normal space travelling between the correct spot and where they need to get to travel out of the system.
- There could now exist 'choke points'... the ideal spots to leave (and possibly enter) a system which can be defended. System blockades might be easier... but in lightly (un-)defended systems, piracy becomes just that much easier.
- Would larger stars produce more of these exotic particles? I.e. it might be easier to go further from large star, while a dim red one produces only feeble waves the pilot can ride upon. (Would this translates as a bonus for astrogation, or piloting -- or just a determination of the maximum jump?)
- The first player to make a 'surfer dude' pilot 'riding the stellar waves, dude', will have to be beaten to death with a sofa cushion.

This would be the cheap jump engine. Expensive ones would allow the ships to move under their own power in jump space.

- Does that mean there might be the possibility of interaction between vessels in jump space? Gonna have battles in jump space.. and only pirates and military vessels are gonna have the hardware necessary to maneuver?
- Are the engines going to be mass dependent? Are planetoid hull vessels going to be more or less practical?
- Are unmanned vessels going to be able to go thru jump space alone? Are you going to see fleets sending automated planetoid vessels thru jump space with insane qualities of missiles to clear the entrance space into a system before they send capital vessels?

- If you have exotic particles that travel ftl, can sophants artificially generate small quantities of these particles? (If societies have cheap fusion power, it's gonna be hard NOT to generate these new particles.) Can they use them for easy ftl communication?
- If for some reason, they can't generate them, the jump drives can interact with the particles. Can societies simply modulate the stellar emissions and use them for difficult ftl communication? (Even if it were simple, very rapid Morse Code... but it would seem that binary data transmission should be possible.)
- I _assume_ the particles travel faster than the ships they are ment to propel... so HOW fast do they travel? Are we talking about the possibility of Star Trek sub-space communcations?

[Hilary_155]

Rasimus, thank you for taking an interest in my theorizing. Your questions made me do some thinking.

Choke points: Yes. But with most systems, the ships that local authorities could bring to bear greatly outweighs anything pirates are going to have. Especially if the locals employ planetoid hull vessel manned defense systems.

You have to come from somewhere to get into a system using these jump sails (I prefer the sailing metaphor to surfing). So any 'pirate' band massing a fleet of ships will have to stage a take off from a nearby star.

There would also be layover stars system that have no viable planet to inhabit but serve as a stop in a series of jump-1 trips. These could prove interesting plot points.

Actually a number of sci-fi authors talk about how unrestricted FTL travel makes belonging to an empire moot. If someone can appear without notice near your planet and drop a few thousand nukes on it, without any way to stop them, belonging to an empire affords you no protection.

Star types: Some stars would produce more, less or none of these particles. For some stars the particle density required to push the ship would only be high enough if you were inside the star itself (or within 100 diameters of the star) and thus make it impossible (or only more difficult) to use to get around. Note: you can use this cheap jump engine anywhere, but without a push from a nearby star, you are not going anywhere.

Also, I would say that the ship is accelerated up to the speed of this solar jump-wind. If you start in a dense enough particle field, you can approach this speed as a limit (complex math, figure you can get 99% of this speed as a best possible scenario. Figure half density means you can get to 50% of this speed. Jump time equal real time. One week jump one at 99% equals 2 weeks (roughly) at 50%) I am still thinking about whether or you can choose to use the target star to slow back down or not. If the ship must remain opaque to this wind even as it approaches the target star, then trying to come out of hump space near the star means a miscalculation would push the ship tangentially from the target star as it got close (jump-wind density) increased. Does that make sense?

Battles in J space: I am going to treat jump space as all blacked out. Nobody can see in it. Ships cannot use sensors. It is theorized that when each ship enters jump space, it effectively enters its own little universe so no collisions can occur. Alternately, the trip in jump space is only THEORETICAL. They way a particle can tunnel from quantum mechanics. Maybe the week of time is spent crossing the threshold into jump space rather than making the trip.

Engines mass dependent: My plan is to make these sail jump engines work with anything, but because the field they create is spherical and extends into J-space, using larger and larger jump sail engines in larger ships means your ship will have to be increasingly more spherical to the point where even a perfect sphere would have the outer shell outside this field. The field produced increases more slowly as engine size increases than does the size of the ship. The engine can push any amount of matter into jump space, but all that matter MUST fall within the spherical field. Practically, these engines only work in ships from 100 to 1000 tons or so. Maybe a perfect spherical ship could go as high as 2000 tons. Past that, the ship is outside the field. Of course, you could just put more than one engine on the ship as long as you design the ship to fall within that field.

insane qualities of missiles: I would say that this threat is just as great if not greater in normal traveller or in any other space campaign setting. If anything, the choke point nature of this drive means you know the directions attacks will be coming from. Also, the world will be either on the sun side of the target star or on hidden side behind its own sun as viewed from any target star.

Detection and particles: I will have these particles easy enough to create on planets. But unless the ship has its own mass driver dedicated to research, ships will not be able to make their own. Various exotic particles will be the mechanism behind the artificial gravity device, all jump drives as well as the reactionless drive. I plan to allow a fusion plasma drive like the HEPlaR system for radioactive fun for penny pinching free merchants.

I have not decided on communication yet. Traveller uses dedicated communication ships or unmanned torpedoes or something for FTL comm. I think it would be cool to use PSIs for real time communication between systems. Alternately, allowing merchants to ferry messages between systems as mail carriers would generate a second income for such tramps without adding any real operational costs.

******

I am gearing my campaign world as a compromise between some physics ideas I have in my head AND technology that can make interesting plot devices.

[Hilary_155]

Truthfully I got the general flavor of this jump sail idea from the book, "The Mote in God's Eye". It isn't exactly the same, but the book talks about 'tramlines' and having to start and end your trip from very specific points that mark the ends of these tramlines. These are essentially highways in space and if you want to travel between stars you MUST use these tramlines. The stellar mechanism that creates these tramlines is essentially the same thing I was talking about with regard to extra-dimensional particles emitted inside extra-dimensional space.

I am working out the size, mass, energy and fuel requirements of this drive and some other technology. But I plan to rely on GURPS traveller 4th edition for stuff like staterooms and computers and hardpoints and weaponry and so on.

[rasimus]

You have to come from somewhere to get into a system using these jump sails (I prefer the sailing metaphor to surfing). So any 'pirate' band massing a fleet of ships will have to stage a take off from a nearby star.

Unless it was from in-system... an attack of opportunity, where the aggressor disables communication from the victim quickly, maybe while no one is able or willing to respond. In the slightly more populated areas, trade wars provide mostly legit attacks against vessels which have to visit the choke point.

There would also be layover stars system that have no viable planet to inhabit but serve as a stop in a series of jump-1 trips. These could prove interesting plot points.

I was thinking all those low pop and/or low tech planets that wouldn't patrol. I assume the 3I would patrol these within the Imperium, and maybe some nearby systems on the way to client worlds.

Some stars would produce <snip> none of these particles.

Ouch.... and if you decide you need those particles to slow down... you can't stop at those stars using the new jdrives. And if somehow you DID stop there... you probably couldn't leave?

One week jump one at 99% equals 2 weeks (roughly) at 50% of this speed.

If it were me, I might be tempted to avoid this whole subject, and handwave "once you get into jump space, both time and space lose meaning, and the vessel is either ejected after approximately 168 hours, or a misjump occurs and in many cases the vessel is never heard from again." The concept of speed (distance covered over a period of time) gets fuzzy in my head when you are talking about particles which move through another dimension (making 'distance' hazzy), making them move faster than c (relative to our universe) (making the measurement of time... problematic.)

It also brings into question - does the vessel gain and lose velocity in real space as it builds up a vector into jspace? What does it 'look' like when the vessel goes into jump? (Contemplating, if for no other reason, than flavor text for the players.)
--- In Star Trek, the vessel appears to go faster and faster, and just switches from normal space into warp.
--- In Stargate universe, a rip to hyperspace appears and a vessel moves into that rip, and the rip closes.
--- I've always pictured Traveller jump drives as more like the way Moya from Farscape jumps... the 'jump grid' on the outer hull lights up, and the vessel somehow simply moves into jump space. (I guess it's somewhat close to Stargate... but with more pyrotechnics.)

Your description, with accumulating velocity from these new particles sounds closer to moving to warp... but the new particles are pushing the vessel in a direction not defined by the other three spacial dimensions of our universe.

Maybe the sails billow in a direction away from the star, and moves slightly away from it due to conventional solar wind, but quickly fades from view like a ghostly apparition as it enters jumpspace?

I am going to treat jump space as all blacked out.

Well, that's a pretty definitive answer to the question on the color of jump space. :-)

Traveller uses dedicated communication ships or unmanned torpedoes or something for FTL comm.

Traditionally, I believe, Traveller has communication only as fast as ships, and jump ships are manned. Even the little x-boats have a pilot that just hangs out reading for a week. :-) (Or maybe playing x-box. Maybe THAT'S why they are called an x-box... ) FTL communication faster than a ship is often considered one of the features which would break the setting/mood/spirit of Traveller. (Which isn't to say you can't or shouldn't do that... it's just one of the things I mention because I think these alternate physics brings FTL comm into question, and you should have an answer when your players bring it up. :-) )

[jason taylor]

Some day I'd like to find some hazards for jump space. The problem is that, aside from internal strife among the crew, they would have to be incomprehensible unless we found a working system for jump physics and so far we haven't. Nothing wrong with incomprehensible-unless it means that the only thing to be done is to sit tight and live through it which limits the plot.

[jeff_wilson]

Originally Posted by freetrav

In general, for 'hard' science fiction, you're allowed one absolutely inexplicable tech handwave, maybe two if your non-explanation seems like it could be a reasonable extrapolation from what we currently know. For the most part, the two are going to be a faster-than-light space drive and gravity manipulation. Add a third, like psionics, and you're stretching things a bit, into "space opera". A fourth loses you disgusted readers, who will call it "space fantasy".[/SIZE]

Not to disagree with the above but to expand a bit: It was H.G. Wells who said that SF should involve a single impossibility and proceed from there, and writers with science and engineering backgrounds realized you can pick a sufficiently fundamental impossible thing and parley it into various effects necessary for human-scale protagonists to sail around the stars: Jack Williamson, for example, used "rhodomagnetism" for FTL and death rays and gravity control and psionics for teleportation and ESP by the single extrapolation of electromagnetism based on the iron-nickel-cobalt elemental trio to the next two triples that included rhodium and platinum, respectively.

This rule is very flexible, esp depending on the role the real physics will play in the story. Niven, Pournelle, and Drake get away with huge liberties in their setting backgrounds in order to make a plot that's all about real physics, and even getting parts of that wrong doesn't take away their "hard sf" cred. Niven's "Neutron Star" includes humanlike aliens, invulnerable spacecraft hulls,
FTL travel and communication, reactionless thrust, prolate spheroidal (watermelon-shaped) planets, but that's all to make an airtight whodunnit where the real physics of tidal forces is the culprit.

[Hilary_155]

rasimus...

I am assuming some level of galactic empire, or at least a federation where trade routes (Green zones) are patrolled by some BIG local ships. It is kinda crazy to think you can conduct piracy in those systems. But obviously the fun is to be had in the Amber Zones. A struggling tramp merchant will push the odds to make a buck. And there would certainly be risky Amber Zone jump routes that brave (reckless) captains could take advantage of.

Big cargo ships carry the bulk of the trade: grains, raw materials, machinery, and make long jumps (up to jump 6 as beyond this it is too hard to plot gravity fluctuations). Routes are listed in "effective" jump distance. Some short routes are harder to plot due to rogue moons or what-have-you. While other long distances that are free of obstacles would be easier to plot. The jump difficulty rating is working distance or effective distance rather than an actual linear distance.

But there must be a niche for tramp merchants for interesting play. I conceived this sail jump so that there would be said niche. But tramp merchants could carry small cargoes too and from the systems normally bypassed by large, long range cargo ships. These are the fringe systems. The small towns that don't fall on a highway exit ramp.

I wasn't thinking of having an actual sail. But I guess that would be cool. You would deploy the sail once in jump space and increase your surface area. Then when you are half way to your destination star, you take in the sail and thus present less of a signature to the target star so the stream doesn't slow you down as much.

I do want the jump drive to work thusly: The drive affects a specific volume of ship. It is the volume of the ship that affects how much power you need to use to enter jump space. Picture a 2 dimensional ship (like a boat silhouette). Now picture this ship being lifted up off the 2 D surface at right angles to that surface. The mass is meaningless as it is only 2 dimensional. It can be as big as you want, it weighs the same. It is a shadow. However, its area is important. This area is how much space is displaced in the next level up of flat dimensions (like a stack of paper). Since we are 3d, volume is the key. A ship displaces a volume of space above it (jump space). AND the jump drive creates a spherical region of affected matter. So ships have to be designed to fit in this bubble. This allows cheap ships to be built (no need for jump lines along the hull) BUT energy requirements increase geometrically for larger bubbles. So this is best used in small ships that do not require the rare earth jump elements.

[Hilary_155]

OK.

Suppose you had a 100 ton scout ship riding inside a BIG ship. The BIG ship goes into jump space. What would happen if the scout ship were to power up its jump drive and try to jump?