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How do the spaceship drives work? And what about the underlying 'Jump mechanics'?



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>From: Lesley Grant <lgrant@maths.tcd.ie>
>Subject: Cherryhlist
>Date: Tue, 14 Sep 93 15:32:11 BST
(...)
> gaming stuff:  Lately I've been really disappointed with the 
(...)
Jo and I have talked about this a lot. Nothing much has happened, as Jo is determined to work out how Cherryh's ships work before doing anything else. (...)
			Lesley


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>Subject: Re: Cherryhlist
>Date: Wed, 15 Sep 93 13:10:26 CDT
>From: goldman@orac.cray.com (Goldman of Chaos -- postmaster CRI-US)
(...)

The C.J. Cherry jump technology doesn't really seem too complex. Basically there seems to be two major drive systems, Slower than light thrusters and FTL capable gravitic wave drives (GWD). For STL maneuvering they seem to use a combination of thrusters and the GWD. The GWD seems only to be effective when the ship is actually in motion, witness Mallory's pulsing of the GWD near the end of Downbelow Station (DS) to get the Union commander's attention.

The riders seem to be equiped with a limited GWD, in Hellburner there was mention of "They tranked you down for jump. They didn't for this move." (pg 366 Warner Books paperback edition) I've read the passage a few times and I THINK C.J. Cherryh is telling us that flying the rider is a lot like being in jump.

Jump mechanics seem simple as well. You stay in jump until you hit a 'null point', unless you have the Mehendo'sat short jump technology. Null points seem to be large gravity sources. When you leave jump space, you retain the speed vector you had upon entering jump space.

(...)
Matt
(...)


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>From: Onno Meyer <Onno.Meyer@arbi.informatik.uni-oldenburg.de>
>Subject: cherryhlist
>Date: Thu, 16 Sep 1993 09:24:42 +0200 (MET DST)
(...)

It should be easy to summarize everything known on the jumpdrive, and every gap that remains has to be filled by guesswork.

The jumpdrive works in two different modes. It can change the velocity of a ship flying STL in major leaps. Three of these leaps are sufficient to brake a ship from more than half lightspeed down to insystem speeds. I'd estimate that a braking pulse are about 0,2c worth. The ships can accelerate with pulses, too. That has to be less effective or there would be no difference between "stringed jumps" without dumping and regular jumps. I'd estimate 0,05c for every pulse. These pulses can only change speed, not direction (see the turnaround at Urtur). These pulses probably can't be made instantly and/or are "noisy", or they would be more frequent in combat.

There is little known on the hardware of the jumpdrive. It uses "vanes" to project a jump-pulse, and the size of the vanes increases with increasing drive power (see the refit of the Pride and the description of the dartship in ML).
The drive assembly is expensive enough to make the jumpdrive and the realspace drive worth 90% of the total ships value (see the refit of the Pride). The jumpdrive is heavy enough to be a substantial part of a ships empty mass (see the chase in CH).
When the Pride was prepared to blow themselves and the hakkit to hell (was that TKSB or CH?), there is some technobabble that shows that a certain realspace speed toward the gravity well of the destination is necessary, otherwise the ships just goes to the nearest large gravity well.
A jumpdrive takes not only the ship but also much of its environment into jump (see the transits at Urtur). If this environment is to heavy, there will be disaster (see the battle in DS, and the voyage in the faded sun).
A empty merchanter or a warship can make several (4+) jumps on a single fuel load (see the chase in CH), but a loaded ship requires new fuel every jump or every two jumps (see the Legacys operations).

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>From: hposo@fltxa.helsinki.fi (Heikki Poso)
>Subject: Cherryhlist
>Date: Thu, 16 Sep 1993 22:28:22 +0300 (EET DST)
(...)
> The riders seem to be equiped with a limited GWD, in
> Hellburner there was mention of "They tranked you down for
> jump. They didn't for this move."  (pg 366 Warner Books
> paperback edition)  I've read the passage a few times and I
> THINK C.J. Cherryh is telling us that flying the rider is a
> lot like being in jump.
"'We're go,' Dek said, and instantaneously the carrier mains cut in with a solidity that shoved them harder than the pods ever had, 10+ in a brutal, backs-downward acceleration.
"Carrier was outputting now, making EM noise in a wavefront an enemy would eventually intercept in increasing Doppler effect, and to confuse their longscan they were going to pull a pulse, half-up to FTL and abort the bubble, on a heading for the intercept zone -- that was the scary part. That was the time, all sims aside, that the theoretical high v became real, .332 light, true hellride, with herself for the com-node that integrated the whole picture.
"They tranked you down for jump. They didn't for this move."

It is the carrier that does "this move", not the rider - they are still attached at this point.

Btw, it seems that the carrier can go from a low speed to .332c with just one pulse.
Heikki
(...)


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>From: Onno Meyer <Onno.Meyer@arbi.informatik.uni-oldenburg.de>
>Subject: cherryhlist
>Date: Fri, 17 Sep 1993 10:59:10 +0200 (MET DST)
(...)
> It is the carrier that does "this move", not the rider - they are still
> attached at this point.
This time you're right. However, there was a discussion some time ago that said that a rider without this drive would be a joke and no warship. Even if there is no direct quote that shows a rider with this pulse-drive, riders are described doing things they couldn't do without. For example, in DS riders patrol the fringes of the system, yet they come home to change crews every shift.
 
> Btw, it seems that the carrier can go from a low speed to .332c with
> just one pulse.
Possible - those carriers are real monsters.
Onno Meyer


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>From: Jo Jaquinta <jaymin@maths.tcd.ie>
>Subject: CherryhList/ More thoughts on Jumpdrives
>Date: Tue, 21 Sep 93 8:37:28 BST
Coalating various people's observations and quotes on jump-drives you might consider a different approach.

Jump drive does not, in and of itself, form a propulsion system. Instead we can interpret "boosting" and "dumping" as just that. The jump drive magnifies the effect of whatever propulsion system.
This can happen in one of two ways: (1) modifying the inertia of the ship or (2) modifying the effectiveness of the, say by changing the mass. We can look at each of these in the three described uses of it: (A) pulsing the vanes up or down, (B) jumping between stars, and (C) destroying starstations :-).
[Adopting Traveller terminology I will refer to their "realspace drive" as the "maneuver drive" or M-drive and the "trans-solar" drive as "jump drive" or J-drive.]
1.A) It could take the current inertia of the ship and dampens/enhance it. I.e if we are buzzing along at .8C and hit the dampers it might halve our inertia and dump us down to .4C. We hit it again and we dump down to .2C, again and we're at .1C. Or something like it dampens inertia by 10% per second of activation.
Warships have bigger Maneuver Drives and so can initially gives themselves a bigger kick to be enhances thus improving overall acceleration. Similarly they can stop dumping earlier since they can handle much higher velocities with their M-drive alone.
2.A) We can postulate that the vanes affect the preformance of the normal maneuver drives. The easiest way I can think of this is if, say, it could magically reduce the mass of the ship. Depending on the vane-to-mass ratio we might get a ship down to a fraction of its original mass.
Thus the normal M-drive when fired under the vane effect would obviously accelerate it considerably more. (Note: the M-drive *must* be a reactionless drive, otherwise there would be no net gain). Whatever reduces the mass would also reduce the effects of 40+G acceleration on the ship superstructure and crew.
Thus warships have M-drives and can accelerate faster under the J-drive effect giving them multiply enhanced boosts and dumps.
1.B) If pulsing the vanes in-system magnifies your inertia then activating them for jump would magnify it trans-relativistically. We know you have to be pointing in the right direction (many references to braketing stars in sights) and you hit the J-drive and *zing* off you zoom in that direction.
2.B) Similarly to the above when the J-drive is fully activated we can reduce the ship's mass effectively to zero (or maybe negative?). This allows the Einstinian barrier to be breached and trans-light velocities achieved.
3.A) How can boosting inertia destroy a stationary station? There are two types of inertia/momentum. Linear inertia (an object in motion tends to stay in motion) and rotational momentumn (a spinning top keeps spinning). If we boots the rotational momentum of an object it will spin catastropically fast. This is supported in that we do see ships stopping their rotation before jumping.
Alternatively it could be a requirement that it boosts inertia in the direction in which the drive is aligned. when docked at station the overal momentumn is not aligned with the drive. In such a case the consequent instabilities could rip the station apart.
3.B) We can therorise that the jump field does not have a uniform effect in mass reduction but that over the size of a ship the differences are not relevant. But over the size of a station if the nearest part is, say 1% of normal mass and the far par, say 5% than you will have severe structual instability. Espicially if your M-drive cuts in with a big kick.

For either (A) or (B) riderships are just ships with very good M-drives but only enough J-drive to perform (1).
Upon examination it seems there is more textual support for theory (A), although personally I prefer (B). Can anyone remember other passages with support or undermine either?
			Jo Grant


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>From: Jo Jaquinta <jaymin@maths.tcd.ie>
>Subject: CherryhList/ Dragging things into jump
>Date: Tue, 21 Sep 93 8:37:53 BST
Item: Ships can drag small nearby objects with them through jump.

Item: Ships need to jump between massive objects, except:

Item: There is a technique for short jumping

Postulation: The jump effect is sensitive to the curvature of space.

Exposition:
Can everyone remember those colourful demonstrations of relativity or black holes? All those green grid lines on black that dimpled into cusps around massive objects?
Imagine you have a heavy object sitting in space. It posesses a gravatational attraction. This is inversely proportional to the square of the distance you are from it. I.e. the attraction is very strong near the object but quickly tapers off. If we represent space as a horizontal line and the gravitational attraction as the slope at each point we get something like this:
**********************                          *****************************
*****************************            ************************************
*******************************        **************************************
*******************************        **************************************
*********************************    ****************************************
*****************************************************************************
We can then quite intuitively see that another object will be attracted to the massive object and roll down the slope toward it. I can remember some BBC show with a sort of distorted billiard table on it with balls rolling about the place.
The above represents a one-dimensional space, a two-d space can be seen on a billiard table but in the full 3-d you can't show the "gravitaional slope" by vertical displacement. 2-d is enough for demonstrating most things.
Lets say we have a ship as the object in the centre. Nearby object will each have their own little dimples around the ship. Clearly since ships can jump small objects near them the jump effect is not limited to the superstructure of the hull. By my above postulation we can theorise that it will cover the surroundings to a certain gravitiational gradient. On our billiard table we are effectively filling the dimple with water up to a certain level. Any object nearby will also be covered with the water. This corelates Item 1.
Lets look again at our diagram but instead imagine that this time in the centre of space our object is a star. This creates rather a massive dimple in the area. We know that ships have to travel some distance away from the central mass to enter into jump. Our postulation fits by assuming that the jump drive can only activate in a region with a gentle slope. That gives a fixed radius around each start that jumps can be entered.
Lets further imagine that when a ship enters jump-space it actually peirces the surface of our model and continues along translated into an orthoganal dimension "beneath" the "surface". When we approach another large mass the gravitational gradient bends below the surface we are traveling at we we "pop" back into normal space. This corelates with Item 2. We will be at the fringes of the system where the gradient is similar to where we left.
If you have your navigation wrong and miss the destination mass you could travel for some time before you hit another mass. If more rugged jump drives (e.g. military ones) can jump lower down the gradient they will come out deeper on the far end. (They might also travel faster through jump space) Of course if they jump too deep and don't target a massive enough exit-point they may miss altogether...
So far we have been only talking about breaching the interface more or less paralell to the generally assumed flat norm. If we breached at a slightly lower angle then our "exit gradient" would slowly increase as we travelled making exit more difficult. If we breached at a slightly higher angle our "exit gradient" would decrease. It the angle was sufficiently high we might reach "zero gradient" and precipitate us back in flat inter-stellar space. I.e. we've just done a short jump. That corelates Item 3.

It this model it looks like species like t'ca and knnn have mastered the ability to change their vector while "beneath the surface".
			Jo Grant


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>From: Onno Meyer <Onno.Meyer@arbi.informatik.uni-oldenburg.de>
>Subject: cherryhlist
>Date: Tue, 21 Sep 1993 11:33:14 +0200 (MET DST)
(...)
> 	Jump drive does not, in and of itself, form a propulsion system.
> Instead we can interpret "boosting" and "dumping" as just that. The
> jump drive magnifies the effect of whatever propulsion system.
> 	This can happen in one of two ways: (...)
That is wrong, since the drive is capable of changing speed in an instant, not over the time of an engine burn.
> 	2.B) Similarly to the above when the J-drive is fully activated
> we can reduce the ship's mass effectively to zero (or maybe negative?).
> This allows the Einstinian barrier to be breached and trans-light
> velocities achieved.
I think negative mass is nonsense. If you can't go below zero, there is no reason why hunters outrun merchanters, since each of them would have zero mass. BTW, isn't lightspeed the limit even for zero-mass objects?
> 	Alternatively it could be a requirement that it boosts inertia
> in the direction in which the drive is aligned. when docked at station
> the overal momentumn is not aligned with the drive. In such a case the
> consequent instabilities could rip the station apart.
Not only the alignment is necessary, a certain speed is necessary to maintain a "hyperspace bubble". The Hani said so when they were prepared to blow the station up.
> 	3.B) We can therorise that the jump field does not have a uniform
> effect in mass reduction but that over the size of a ship the differences
> are not relevant. But over the size of a station if the nearest part
> is, say 1% of normal mass and the far par, say 5% than you will have
> severe structual instability. Espicially if your M-drive cuts in with
> a big kick.
Again, when the station was about to blow, the described effect was unlike any structural failure.

(...)
(...)
> 	It this model it looks like species like t'ca and knnn have
> mastered the ability to change their vector while "beneath the surface".
(...)
That is the best explanation I've heard so far. The hani always talked about flying deep into the well to do this or that ...
Onno


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>Date: Tue, 21 Sep 93 19:14:01 -0400
>From: "Nancy Silberstein" <silbersteinn@a1.mscf.upenn.edu>
>Subject: Cherryhlist/Thanks, Jo
(...)

Jo, I enjoyed (enjoyed?) your discussion of the mechanics of space flight. Did I understand it? No-o-o. Will I reread it and try to formulate pertinent questions? Yes. However, I wanted you to know that your picture of a space dimple hit me between the eyes. THAT, I thought, is a gravity well!

Apparently I'm not ready for words yet, but I can handle pictures. Got any more?
njs  21-SEP-1993 14:30 


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>From: David Zink <zink@panix.com>
>Subject: cherryhlist
>Date: Sat, 25 Sep 1993 04:29:57 -0400 (EDT)
(...)
> The C.J. Cherry jump technology doesn't really seem too
> complex.  Basically there seems to be two major drive
> systems, Slower than light thrusters and FTL capable
> gravitic wave drives (GWD). (...)
Hey! I missed the part where we found out they were gravitic wave drives!! (Actually, gravitic wave drives are a legitimate hole in the whole `speed of light is the limit' thing. However, since they are only useful if you can generate gravity without corresponding mass, modern physicists don't see it as a pressing problem.) (...)
> Postulation: The jump effect is sensitive to the curvature of space.
Yes, I think that's pretty clear.
> > 	2.B) Similarly to the above when the J-drive is fully activated
> > we can reduce the ship's mass effectively to zero (or maybe negative?).
> > This allows the Einstinian barrier to be breached and trans-light
> > velocities achieved.

> I think negative mass is nonsense. If you can't go below zero, there is
> no reason why hunters outrun merchanters, since each of them would have
> zero mass. BTW, isn't lightspeed the limit even for zero-mass objects?
According to Einstein (I think it's an inaccurate limitation, Einstein's math error is fairly obvious, he claims to prove that nothing but nothing can ever communicate faster than the speed of light, when actually all he managed to prove was that nothing composed of any form of matter we've detected, and no electromagnetic radiation can ever travel faster than the speed of light. The only things these left out (in his day) were the strong and weak nuclear forces and gravity. They've managed to prove that the strong and weak forces are aspects of electromagnetism, so all that is left out of the box now is gravity. I don't know whether they've proven that gravity travels at the speed of light, but I know they assume it, and until someone proves that it, or some other force we haven't detected yet, does travel faster than light, the physics community thinks it a rather dead issue (there are some working on it, but they are few. This is one of the reasons why the Grand Unified Field Theory is so sought after).
	-- David
(...)


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>Date: Tue, 28 Sep 1993 07:46:54 EDT
>From: davis@licre.ludwig.edu.au
>Subject: cherryhlist
(...)
>Hey!  I missed the part where we found out they were gravitic wave
>drives!!
I don't think we did, it was put up as a possibility.

(...)

An interesting difference between knnn (and possibly t'ca) ships and other Compact ships: there are several references to hani ships "dipping into the interface" even on the long jumps (as opposed to manoeuvring or acceleration), and being incapable of changing vector or communicating during jump. The methane breathers seem to dip far further into hyperspace, and are clearly able to communicate and change vector there.

I think that drawing somebody did before (Jo?) was a good one, but there may be another level further down through which the knnn commute.
Ian Davis                                  davis@licre.ludwig.edu.au

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