Ponderings on the Jump Drive

[morty_shworts]

How many EPs does it take to jump?
Page 354 of the T20 Book gives the following step by step of a jump.

The Procedure for entering Jump is as follows:
1. Jump Plot is generated.
2. Powerplant brought to Jump Readiness.
3. Jump Plot is fed to the navigational computer.
4. Jump Drive is brought to Readiness.
5. Jump Drive begins to fast-burn its Jump Fuel, developing high levels of power.
(how many EP's would that be?)
6. Jump Grid is charged. (how many EP does that take?)
7. Astrogator or Captain gives final Jump command.
8. Jump Field is formed.
9. Vessel enters Jumpspace.

Its steps 5 and 6 that I'm wondering about. How many EP's are produced when the jump drive consumes its fuel? A fusion reactor produces 1 EP per round for 241,920 round (4 weeks) on 1 ton of fuel. Going with this as a base that would mean that a standard free trader's J-drive would produce 5,322,240 EP in a mater of seconds from its 22 tons of dedicated fuel. That can't be right, as page 268 of the T20 book states “A 1-ton capacitor (in a Jump drive or not) can store up to 36 Energy Points”, and it also says a jump drive has capacitors equal in size to (0.5% x Jump USP Rating) x Hull Tonnage. So our free trader's jump drive capacitors could only store 36 EP. In fact it would take 147,840 tons of capacitors to hold all 5,322,240 EP.

The T20 book also says on page 354 “This fuel is used up at an immense rate in a powerful, but inefficient process.” Exactly how inefficient could that be to eat up 5,322,240 EP in just a few seconds. These numbers just don't add up.

I think that it would be more reasonable to say that a jump drive needs EP equal to the maximum EP rating of its jump capacitors to enter jump space, and EP after that equal to what the jump drive needs per round to maintain the jump field.

With this as the bases for what I was pondering over, would it be fare to say that a ship could be designed to use capacitors charged by its reactor to make jump. Going back to my example of the standard free trader, it would require 13 rounds to charge the ships capacitors and then the ship could jump. Or would it be more fare to say a ship so rigged would need x10 times the capacitors to jump using this system. Thus it would take 130 rounds or 13 minutes to charge its jump drive before it could jump.

 

[sgbrown]

Originally posted by Lord Morty of Schwartz:
How many EPs does it take to jump?
-clip-
The T20 book also says on page 354 “This fuel is used up at an immense rate in a powerful, but inefficient process.” Exactly how inefficient could that be to eat up 5,322,240 EP in just a few seconds. These numbers just don't add up.

I think that it would be more reasonable to say that a jump drive needs EP equal to the maximum EP rating of its jump capacitors to enter jump space, and EP after that equal to what the jump drive needs per round to maintain the jump field.

-clip-

Don't the various descriptions of how "canon" jump drives work normally include some hydrogen "fuel" vented along the grid to form a jump buble?

This appears to be one of the recurring issues with traveller "How exactly does jump drive work?" Typically an IYTU thing with a lot of implications whichever way you go.

 

[tjoneslo]

If you want a real answer to this, you'll need to go through the history of Traveller. So if you'll indulge me.

In Book 5, under the description of the Black Globe genrator, there is a rule which states that if the jump capaciters are full (i.e. have a full charge), and you have the jump fuel available, you can jump immediately. Otherwise jump preparations take a full turn. It is the implications of this rule which makes some people think the "Jump Fuel" is used to form the bubble of normal space around the ship while in jumpspace. Or similar operation.

Like your calculations show, the normal powerplant can provide enough power to fill the jump capaciters in a few minutes. Since High guard uses a 20 minute turn, the 13 minutes to fill the capaciters is correct.

With the publication of Digest Group Publication's Starship Operators manual (and later repeated in some MT books and T20), it is explicitly stated the "Jump Drive" consists partly of a fusion power plant and some or all of the "jump fuel" is used as a more traditional fusion fuel.

It is never stated how much power is generated by this "inefficient" power generator, but given the relative inefficiencies of the CT and MT fusion plants, it's pretty horrible.

On the other hand, if you think about a rocket engine, it generates a huge amount of power, but it can only be used in one way. So the jump drive uses the 36 EP from the capaciters to trigger a semi-controled fusion explosion around the ship (using the jump fuel). This causes the ship to "fall" into jump space. The exact quantity of energy (in EP or MW or whatever) is unknown, but it really doesn't matter since you can't use the energy any other way.

Personally I'm of the Jump Fuel is used to form the normal space bubble around the ship school of thought.

In either case, the calculation of 5 million EP is misleading, since either the jump drive doesn't generate any extra EP, or it generates it in a manner which can't be used for much (if anything) else. Depending upon your jump drive operation assumptions.

 

[sgbrown]

I'm sure it's not canon, but an interesting house rule (to be "discovered" by the players - not given to them) would be that black globe generators where actually the ancients way of minimizing the jump fuel required. The globes accomplished this by replacing the hydrogen used for establishing the "normal space bubble." A properly modified black globe equipped ship would only need to expend the energy needed to power the capacitors and jump with the globe engaged.

Knowing this secret could be very dangerous of course. Every interstellar government in known space would be extremely interested in a method to produce a J6 warship capable of multiple jumps without refueling. (And that actually requires less fuel if fired upon with the shields up!) This would definitely be "disruptive" technology.

More than a few adventure seeds come to mind for making it interesting should the players come upon this nasty little secret - or for letting NPC's make it interesting using this secret.

 

[Commander Drax]

Also not all of the fuel expended is used to create the jump field bubble and power the high yeild fusion reactor known as the Jump Drive - some or most of it is coolant (jump discharge mass) vented to space (into the bubble perhaps) to dissipate the vast amount of heat generatd by the jump drive.

I would agree that it should be possible to jump using stored electrical energy, however it has become traveller canon that a thin atmosphere of hydrogen is needed to prevent the jump field bubble from collapsing earlier than desired.

 

[robject]

Originally posted by Commander Drax:

... it has become traveller canon that a thin atmosphere of hydrogen is needed to prevent the jump field bubble from collapsing earlier than desired.

Ah, invoke the C word.

To misquote Monty Python: "bet it isn't".

 

[princelian]

I agree with robject here. It is not Traveller canon, but instead it has become a de facto standard used by many of the Traveller community (as represented on many threads here, for example).

It is not what I use - the J-fuel breaks into hyperspace (~30% usage) and then maintains a N-space field around the starship to protect it from the energies of J-space. But that's just how I have run it a long, long time, ever since I did evil to my PCs by introducing a fuel leak while they were in J-space, one requiring EVA to fix.

That was so much fun, I've kept the concept alive for a long, long time.

 

[mike wightman]

I've been playing around with different ways to power the jump drive:

fission/fusion power plant - charging the capacitors can take hours to days

solar collectors - charging the capacitors can take days to weeks

standard jump drive - charging takes minutes

So no hydrogen bubble for me

I'm also thinking of bringing back the jump governor...

 

[Savar]

Originally posted by Sigg Oddra:
I've been playing around with different ways to power the jump drive:

fission/fusion power plant - charging the capacitors can take hours to days

solar collectors - charging the capacitors can take days to weeks

standard jump drive - charging takes minutes

So no hydrogen bubble for me

I'm also thinking of bringing back the jump governor...

like them ideas, I was just wandering about the mass diffrences for useing caps only, and charging from other sorces then the jump drive.

 

[Ptah]

No hydrogen used as a jump bubble for me either.

The large amounts of hydrogen are used to generate energy to enter jump space and to maitian a bubble of N-space around the ship.

Turning on the jump drive causes an interaction between the power-plant and jump drive which causes huge amounts of energy to be formed but this energy and the associated waste heat is funneled/appears in jump space.

When enough energy is input into jump space a "rip" or opening forms and the ship enters jump space.

There is a brief moment where the engineer needs to transfer energy properly from jump opening creation to N space protective bubble. Failure results, at best, in a power surge that damages the ship. At worst, the ship enters jump space without the N space bubble and is never heard from again.

One key aspect to me of this IMTU approach is to keep the massive amounts of energy in jump space and most of the bad effects of misjump there as well. For me this is to prevent jump drives from being used as effective weapons (such as high energy fragments exiting jump space), since there are enough weapons already.

Once in jump space, it is the navigator's job to maintain the N space bubble's proper "shape" so it doesn't collapse. Energy needs to be constantly redistributed (a jump grid helps immensly with this). An experienced navigator will say each jump drive will have its quirks as well as each jump route.

There are also unexplained periodic increases in the difficulty of maintaining the N space bubble, referred to as hyperspace weather. Some navigators even swear things live in jump space telling tales of where they swear an intelligence was trying to weaken the N space bubble, countering their every power adjustment. Some like to call them jump dragons as in "here be dragons."

Navigators can be a little wonky IMTU especially since N space monitoring is a 24/7 job. Comps can do it to a degree but sentients appear to be better. On lower budget ships on non-standard routs 1 navigator stays awake the entire week since it is much cheaper to pump him full ot TL11+ drugs than to hire navigators for shifts.

More safety conscious operations stick to well mapped routes (part of the Scout Service duty IMTU) is to map this jump weather to provide data for better navigation. On well mapped routes you can get by with a comp navigator and a sentient on standby for emergencies.

 

[robject]

I like the CT idiom, where the power plant powers up the jump drive, and the jump drive uses all its fuel up within the hour to rip a hole in space.

It allows drop tanks, and makes the jump drive a very specialized item that can't be potentially used (Massive energy generation you say? Hmmmm!) for anything but entering and leaving jumpspace.

And I'm generally with Sigg on jump drive varieties. Use jump fuel or a trickle charge.

 

[Commander Drax]

"Ah, invoke the C word."

Found it -

If you look at Fire, Fusion and Steel 2 - Page 12 halfway down the page in the right column under 'Jump Grid Area' it says :

"The Fuel remaining in the Jump Drive's surge tank is used to create a thin hydrogen atmosphere around the ship during jump, which helps delay the collapse of the Jump Bubble."

Sigh - I hate being right!


Am I to consider that FFS2 is no longer cannon - "bet it is"


I think it's fair to speculate that across the Imperium there might be many different ways to enter jump - and whilst drives might be similar they could be designed by different manufacturers to perform in slightly different ways such as the MT jump drives that did not need any input power from the Jump Drive as detailed in MT's Starship Operators Manual in which the 'Old Timer' related a story about serving on a ship that had a damaged power plant - the jump drive was working fine so they jumped to a friendly system and got towed in by a navy tug - whilst heat and lifesupport was provided by back up batteries.

Just for the record I'm not a slave to canon but I do like to reconcile aspects of canon with new developments such as the TNE explanation of Jump Drive pushing a ship through for want of a better explanation "a wormhole", "a tunnel that traverses Jump Space" - thus experienced Travellers refer to time during jump as 'Time in the Hole'

Fire,Fusion and Steel 1 - Page 42

Whilst these MT drives didn't need input energy from the power plant as opposed to those in CT/T4 that did - I have no problem reconciling them along the lines of civilian drives need input energy - military drives don't or drives made by this manufacturer are preferred by some ship builders because they don't depend upon an external powerplant to maintain the jump field.

 

[atpollard]

Originally posted by Commander Drax:
Am I to consider that FFS2 is no longer cannon - "bet it is"

... but it shouldn't be.

(just trying to stir up trouble)

 

[Commander Drax]

There's loads of things I don't like in FFS2 - but I try and reconcile them as previously mentioned

 

[sgbrown]

Chalk this up as a silly newbie question if you will - but since FFS2 isn't T20, what system was it published for? And more importantly, would it be considered "cannon" for systems using different ship design rules? (ie can you use any "cannon" design rules for any other traveller rule set? Sounds rather problematic.)

 

[Ptah]

Originally posted by SGB - Steve B:
Chalk this up as a silly newbie question if you will - but since FFS2 isn't T20, what system was it published for? And more importantly, would it be considered "cannon" for systems using different ship design rules? (ie can you use any "cannon" design rules for any other traveller rule set? Sounds rather problematic.)

For Traveller the New Era (TNE). I think the chronology goes: Classic Traveller - MegaTraveller - TNE - T4- T20.

My view on canon (realizing I'm a heretic, he+) is it is canon for the OTU, but it neededn't be for YTU. How the jump fuel is used has little impact on mechanics although maybe the kind of adventures you run. That is wierd situations players can get into.

If you use different ship design systems you'll get different ship performance, sometimes light sometimes not so slight. Others can weigh in on the interchangeability of designs -some are working very hard on this for T5.

 

[robject]

FFS2 was built for Traveller 4th Ed. Cmdr Drax found the quote about what jump fuel was used for in it.

I don't care for the 'layer of hydrogen' official handwave -- don't care for the 'inefficient power plant' one either -- but neither seem to affect playability.