Mongoose 2300AD: Stutterwarp Station Keeping and Orbits

[hdan]

Forgive me if this is well established canon somewhere, but as a 2300AD newbie (brought in by the Bundle of Holding), I'm having trouble wrapping my head around starships without any reaction drives at all.

If this has been beaten to death elsewhere, I would appreciate a link.

Since stutterwarp doesn't change your momentum and many starships lack reaction drives, how do such ships match velocities with the planets the visit? Is it a matter of "hovering" in a gravity well long enough to build up momentum in the direction you want, then warping over to a place 90 degrees around the world to enter orbit?

If so, would not these "approach nodes" get pretty crowded?

If not, do ships just blaze past worlds and hope interface vessels can catch up with them, load/unload, and then get away before they get too far off?

Or can a stutterwarping ship control its motion finely enough that it can "stutter dock" by effectively canceling out its momentum relative to an interface craft? I'd think it would be impossible to dock with a stutterwarping ship though....

Thanks in advance,
/hdan

 

[Kilgs]

Um... good question.

To answer the second part, the stutterwarp "moves" a ship by displacing it a millimeter or so. Spinning the drive quickly results in gajillions of these micro-moves which transport the vessel without breaking the laws of physics (it's sci-fi, quiet you!).

If you turn off a stutterwarp drive, you simply stop in place with NO momentum. There's no actual thrust so you don't have to worry about applying reverse thrust to slow down or stop. So, yes, a stutterwarp drive ship with no reaction drives can simply stop and an interface vehicle can approach it.

(This raises obvious concerns regarding the need for accuracy in plotting jumps near orbital facilities and the like...)

But as for entering orbital velocity... you raise an excellent point. I'm guessing they don't and remain outside the envelope just sitting there. Unless the gravity well can pull them along or perhaps a tug yanks them into the orbit? Me no scientist so I'd simply ignore it ;-)

 

[McPerth]

If you turn off a stutterwarp drive, you simply stop in place with NO momentum.

Well, as I understand stutterwarp, if you turn it off you stop in place with no momentum change from what you turned it on (so you maintain you momentum).

So, in order to remain in orbit, you must calculate where you momentum will put you in a more or less stable orbit (I guess being stable for the 40 hours you'll need to dischare the coils will suffice) to turn off you stuterwarp.

Also, I've always assumed in developed systems there are tugs (with reaction drives) for delicate maneuvers for the ships lacking them (e.g. to dock to a space station).

 

[mike wightman]

Ships have to be built somewhere - which means they have the orbital velocity of the building shipyard.

When they move by stutter warp they maintain this orbital velocity.

The only way to change orbital velocity is to:

use a reaction drive

switch off the warp drive near a large object and use it to change orbital velocity.

I have long held the theory that this would be a better explanation for why warp ships can only go so far before they have to "discharge the drive" - after travelling several light years the difference in gravitational potential energy, orbital velocity etc makes it highly dangerous to step off the ship without matching local orbital mechanics.

One day I'll do the math but it is a rather difficult set of equations...

 

[Kilgs]

Well, as I understand stutterwarp, if you turn it off you stop in place with no momentum change from what you turned it on (so you maintain you momentum).

I was going to point out that the OP was talking about ships with no reaction drive so they would have no initial momentum...

Ships have to be built somewhere - which means they have the orbital velocity of the building shipyard.

When they move by stutter warp they maintain this orbital velocity.

Doh! ;-)

Again, likely needs a handwave. Or assume that a non-reaction propulsion ship is towed out to space, and released as close to 0 thrust as possible, by a tug. Then when it needs to make orbital velocity contracts with a tug.

 

[whulorigan]

I was going to point out that the OP was talking about ships with no reaction drive so they would have no initial momentum...

Momentum is relative to reference frame. It may be true that it might have no initial momentum relative to its starting reference frame, but its destination reference frame would almost certainly have a different momentum value relative to the initial frame/ship's frame.

 

[hdan]

Momentum is relative to reference frame. It may be true that it might have no initial momentum relative to its starting reference frame, but its destination reference frame would almost certainly have a different momentum value relative to the initial frame/ship's frame.

That's my point. "orbit" around one world is almost guaranteed to not be a useful velocity for orbit around any other world. Well, as long as the relative speeds between systems isn't too high, and you pick a world with a roughly similar year length, you *might* be able to find a way to make your velocity work for you....

It's the same with jump drives - "same velocity" relative to your start point is not going to have any meaningful relationship to that velocity in another system.

I do sort of like the idea of carefully executed "gravity tug" maneuvers to get ships into a decent velocity as you approach a world, possibly needing to spend some time slingshotting around another world to align your approach, though that sort of math has little place in an adventure game, and as a GM I'd abstract it all away with navigation skill checks.

 

[Kilgs]

I do sort of like the idea of carefully executed "gravity tug" maneuvers to get ships into a decent velocity as you approach a world, possibly needing to spend some time slingshotting around another world to align your approach, though that sort of math has little place in an adventure game, and as a GM I'd abstract it all away with navigation skill checks.

If I'm understanding you correctly... a procedure where prior to jumping the ship has the right amount of velocity to enter orbit? Then it jumps into a position, with the right velocity, that puts them in orbit.

That could result in one heck of a fender-bender with no way to control approaches from light-years away. Granted we're talking about a lot of real estate but a collision is bound to happen in or outbound since the origin/destination points are going to be similar.

 

[hdan]

If I'm understanding you correctly... a procedure where prior to jumping the ship has the right amount of velocity to enter orbit? Then it jumps into a position, with the right velocity, that puts them in orbit.

That could result in one heck of a fender-bender with no way to control approaches from light-years away. Granted we're talking about a lot of real estate but a collision is bound to happen in or outbound since the origin/destination points are going to be similar.

It's more like something you'd do as you approached a system. You might swing past a gas giant to "bend" your realspace trajectory in a useful direction, or maybe slow yourself down by stutterwarping to a position where the gravity well is behind you, and then stutter-hover while your realspace vector shortens, etc. You'd still have some navigation issues, but since each inbound vector would be slightly different, I think things would work out.

Plus, with a couple day's travel time, maybe station-keeping thrusters are sufficient to tweak realspace velocities during transit?

On the other hand, having thought through this a bit more, stutterwarp wreaks havoc with your kinetic and potential energies, and there's really no way I can see to reconcile it with physics. Well, maybe there's one way - the drive converts the minor changes per jump into heat and whatever the "gravimetric charge" thing is called.

Argh, my head hurts. Maybe it's easiest to just say that a ship winds up more or less in a proper orbit when it approaches the "wall", provided the navigator does a decent job.

 

[epicenter00]

There's basically two lines of thought about this.

1) Stutterwarp ships have conventional maneuver thrusters. They used for station-keeping and fine maneuvering since approaching something to dock to it using Stutterwarp is ... problematic (see also: Bayern accident).

2) Stutterwarps can change their vector by hanging around in a gravity well that will give them the vector they want. For instance you locate a gravity well where you'll "fall" in the direction you want. You know that your Stutterwarp jump will be 100m because of how deep you are in the gravity well. You move the ship to the relation with the mass to get the proper vector. You "fall" 100m letting yourself build momentum. Then you flicker your Stutterwarp, appear back to where you started. Let yourself fall 100m again. Reappear at your original position. Repeat until you get the velocity you want. Each time, your ship is building momentum. This is a very basic example, in application, Stutterwarps flicker thousands of times per second, so the ship would appear like it is is standing still, yet building momentum constantly.

I'm personally of the opinion Stutterwarp ships actually use both methods. They use #2 to mostly match velocities with their destination, then use conventional maneuver thrusters for the fine work. This allows Stutterwarp vessels to save on reaction mass for their thrusters.

 

[Murph]

i.e. the old EE "Doc" Smith thing about "matching intrinsics" The inertialess drive of the Lensman series is similar in concept.

Ships have to be built somewhere - which means they have the orbital velocity of the building shipyard.

When they move by stutter warp they maintain this orbital velocity.

The only way to change orbital velocity is to:

use a reaction drive

switch off the warp drive near a large object and use it to change orbital velocity.

I have long held the theory that this would be a better explanation for why warp ships can only go so far before they have to "discharge the drive" - after travelling several light years the difference in gravitational potential energy, orbital velocity etc makes it highly dangerous to step off the ship without matching local orbital mechanics.

One day I'll do the math but it is a rather difficult set of equations...