Electric jump drive.

[spank]

Inspired by the "why not metallic hydrogen?" thread, and some reading I've been doing on black gloves, I wondered, why not an electric jump drive?
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It's not as crazy as it sounds at first, reading the section on black globes in High Guard, it is stated that the black globe dumps absorbed energy into the ships capacitors and it states that it will ise the ship 's jump capacitors if no dedicated capacitors are installed. Furthermore if a ship absorbs enough energy and it has "sufficient fuel" it may jump at the end of the turn.
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The only questions are, how much energy per jump? And how much is "sufficient fuel" considering the capacitors are already charged? Could a ship be fitted with an external umbilical to charge it's capacitors from a jump tender, then separate and jump away? What would the fuel savings be?

 

[Condottiere]

Probably depends on the edition.

Mongoose Second allows batteries to power the jump drive.

You still need fuel.

 

[whulorigan]

At that point you effectively have the equivalent of a Jump-Gate. Transfer power externally (via cable or "beam" it via laser, et al), to on-board capacitors and jump. No fuel tanks needed (unless you need some minor fuel consumption to maintain a jump field in-transit). This is not much different in practical terms from a Jump Gate setup, where the ship is dependent upon an outside jump-power system to initiate the interstellar jump.

 

[AnotherDilbert]

The only questions are, how much energy per jump?

The jump fuel is put into the power plant to generate the needed energy for the jump. How much energy would that amount of fuel generate?

For simplicity, take a 1000 Dt ship with a J-1 drive. It would use 100 Dt fuel to jump. The power plant would use 10 Dt fuel to generate 10 EP for a month. So, 10 Dt fuel is 4 × 7 × 24 × 3 × 10 = 20 160 EP.
Jump fuel is burnt "less efficiently", let's say 50%. That would mean that the regular jump fuel generated 20160 / 10 × 100 × 50% = 100 800 EP.

So, if you have 100 000 EP or so you can jump immediately, without fuel. Unfortunately that is ~3 kDt of capacitors to jump a 1 kDt ship.

I'll take the 100 Dt jump fuel and the "few minutes" it takes to burn it.

And how much is "sufficient fuel" considering the capacitors are already charged?

Normal jump fuel.

 

[Spinward Flow]

This is not much different in practical terms from a Jump Gate setup, where the ship is dependent upon an outside jump-power system to initiate the interstellar jump.

And yet ... Jump Projectors exist at higher tech levels ...

Granted, those are intended to be used as offensive weapons (that force a misjump) rather than as a friendly "jump gate" type of setup that can control breakout destinations for third party craft ... but getting to that additional level of "refinement" in control ought to be possible with increasing tech level advancements.

Kind of like how in LBB5.80, meson gun spinal mounts first appear at TL=11, but then by TL=12 the first meson screen (and nuclear dampener) becomes available.

All you need is a way to make a Jump Projector into a system that induces a JUMP rather than a MISjump in the target, with a destination chosen by the "attacker" in a way that is controlled, rather than uncontrolled ... and you'll have your "jump gate" type of setup.

 

[kilemall]

Nuke powered jumps, Project Orion updated.

 

[mike wightman]

The jump fuel is put into the power plant to generate the needed energy for the jump. How much energy would that amount of fuel generate?

For simplicity, take a 1000 Dt ship with a J-1 drive. It would use 100 Dt fuel to jump. The power plant would use 10 Dt fuel to generate 10 EP for a month. So, 10 Dt fuel is 4 × 7 × 24 × 3 × 10 = 20 160 EP.
Jump fuel is burnt "less efficiently", let's say 50%. That would mean that the regular jump fuel generated 20160 / 10 × 100 × 50% = 100 800 EP.

So, if you have 100 000 EP or so you can jump immediately, without fuel. Unfortunately that is ~3 kDt of capacitors to jump a 1 kDt ship.

I'll take the 100 Dt jump fuel and the "few minutes" it takes to burn it.



Normal jump fuel.

It may explain how antimatter powered jump drives don't need all that hydrogen fuel though...

I originally postulated that collectors gathered "exotic jump particles" - a particle is just an excitation of a quantum field so what if the accumulators on a collector drive store these "jump field oscillations"? Useless for electricity generation but can be used to trigger the jump effect.

So a jump accumulator is different to a jump capacitor...

 

[Vargr Breath]

Annic Nova from 1979.

 

[Grav_Moped]

Annic Nova from 1979.

And the fact that it's from 1979 is the reason it can "work".

Under '77 rules, ships did not need to run a power plant during Jump. Its nominal 1km diameter Collector Sail (at 100% efficiency, at 1AU from a Sol-like star) is about Pn-4.3 or so. Over 1-6 weeks, it can collect enough energy to kick off a jump. It cannot collect enough energy to do that and also provide Pn=Jn power levels for the week spent in jumpspace.

 

[whulorigan]

Nuke powered jumps, Project Orion updated.

Would that be a Stutterwarp?

 

[McPerth]

My take:

how much energy per jump?

I guess this is answered in the Breaking Off, jumping section in the same LBB5, page 39:

It must expend energy points equal to two turns output from a power plant whose number is equal to the jump being attempted (EP required =0.01MJn).

So, I guess the total EP needed is 0.02MJn (as it is two turns worth)

And how much is "sufficient fuel" considering the capacitors are already charged?

This has been discussed for ages, as information is contradictory, as there’s no consensus about how much jump fuel is used to power the jump.

The fact the ship needs sufficient fuel to jump even with the capacitors full seems to point most of the fuel is not used for power, but for other needs (keeping the jump bubble is the most accepted one), but the fact Annic Nova may jump without fuel seems to deny this…

I guess the accepted consensus is “sufficient fuel” means the full jump fuel needs, but that’s not, to my knowledge, set in stone. If so, the only advantage of used power stored from the BG would be to be able to jump in a single turn while using the PP output for other uses (defense, firing, etc)

I'm sorry not to be able to give you hard rules about this, but AFAIK there are not, and I guess each Traveller player has his own interpretation of this point

 

[kilemall]

Would that be a Stutterwarp?

Stutterjump, or shovejump.

 

[AnotherDilbert]

It may explain how antimatter powered jump drives don't need all that hydrogen fuel though...

Yes, explicitly:

JTAS#24, "Jumpspace", p35:
REQUIRED ITEMS
An operating jump drive requires several basic components which, when operating together, make jump possible.
Power Source: Jump uses large amounts of energy to rip open the barriers between normal space and jump space. Normally, only a fusion power plant can supply this energy. Some alternate systems make use of solar power generators (which operate much more slowly), or anti-matter power systems (rare and very high-tech).

The jump just needs vast amounts of energy, delivered very quickly. How that power is generated is a technical detail.

I originally postulated that collectors gathered "exotic jump particles" - a particle is just an excitation of a quantum field so what if the accumulators on a collector drive store these "jump field oscillations"? Useless for electricity generation but can be used to trigger the jump effect.

I have no idea how Collectors works. It can apparently collect vast amounts of energy fairly quickly and release it very quickly, but it can't release small amounts of energy slowly (replace a power plant).

The example 1000 Dt ship above needs something like 100 000 EP ≈ 30×10¹⁵ J.
If the Collector can collect that in a week, it can collect 50 GW, much more than the regular power plant produces, yet it can't replace the power plant?

The morale of the story is: Don't dig too deeply into jump physics, it doesn't add up...


Edit: That is T5 collectors, Annic Nova does use the collector to charge a battery that is used instead of a power plant. That does make more sense, but what is the size of a ~20 GW equivalent solar collector?

 

[AnotherDilbert]

I guess this is answered in the Breaking Off, jumping section in the same LBB5, page 39:

So, I guess the total EP needed is 0.02MJn (as it is two turns worth)

You truncated the quote:

HG'80, p39:
Breaking Off: ...
Jumping: A ship which breaks off by jumping must have a destination and enough fuel to get there. It must expend energy points equal to two turns output from a power plant whose number is equal to the jump being attempted (EP required =0.01MJn).
...
A ship which cannot summon the required energy in two turns may not jump at all.

Just as described:

JTAS#24, "Jumpspace", p36:
THE TYPICAL JUMP
...
When the jump drive is activated, a large store of fuel is fed through the ship power plant to create the energy necessary for the jump drive. In the interests of rapid energy generation, the power plant does not work at full efficiency, and some of the fuel is lost in carrying off fusion by-products, and in cooling the system. At the end of a very brief period (less than a few minutes), the jump drive capacitors have been charged to capacity. Under computer control, the energy is then fed into appropriate sections of the jump drive and jump begins.

To jump you need the normal amount of jump fuel and the power plant to convert into energy.

It's not how much energy is available, it's about how quickly you can generate it. Just as described in the JTAS article.

Errata clarified:

CT Consolidated Errata 1.2, p17:
Page 39, Pre-Combat Decision Step, Breaking Off, Jumping (clarification): The ship’s jump drive, power plant, bridge and computer must be capable of supporting the jump being attempted at the time the jump should take place, and the ship must have sufficient fuel for the jump, or the jump does not happen.

No exceptions to the normal jump requirements are made.

This has been discussed for ages, as information is contradictory, as there’s no consensus about how much jump fuel is used to power the jump.

What contradictory information? There is no hint of any jump fuel consumption other than the normal that I have seen.

There is no question of jumping without jump fuel:

HG'80, "THE BLACK GLOBE", p43:
If a ship absorbs enough energy to make a jump, and is supplied with sufficient fuel, it may jump at the end of the turn.

There is no jump fuel use described other than:

HG'80, pp22:
Jump fuel requirements are computed at 10% of the ship tonnage per jump number; thus, the Akron is a 10,000 ton jump-6 ship and requires fuel tankage of 6,000. Fuel usage is computed similarly; 10% of the ship tonnage in fuel is used per jump number used (for the Akron, performing jump-1 uses 1,000 tons of fuel, while performing jump 6 uses 6,000 tons of fuel).

Note that "enough energy to make a jump" is much less than normal jump capacitor capacity. The Akron needs two turns output from a PP-6 = 2 × 0.06 × 10000 = 1200 EP. It has 10000×0.5%×6 = 300 Dt capacitors with a capacity of 10800 EP. The capacitors need only be about 10% full. The energy for the jump is supplied by the jump fuel, as usual.

 

[Condottiere]

 

[McPerth]

You truncated the quote:

In fact, I still think I quoted all the relevant part to answer the question (remember it was How much energy for jump?).

While the rest you posted is interesting, IMHO it adds nothing to answering the question, and I try to limit my quotes (mostly from published and IP protected material) to the strict minimum to make my point. Maybe I’m too prudent on it…

What contradictory information?

BG need to have fuel to jump despite having enough power on your sinks vs Annic Nova not needing the fuel exactly in the same situation.

At least I (and for the discussion there have been for long here, I guess many others) see it as contradictory…

Note that "enough energy to make a jump" is much less than normal jump capacitor capacity. The Akron needs two turns output from a PP-6 = 2 × 0.06 × 10000 = 1200 EP. It has 10000×0.5%×6 = 300 Dt capacitors with a capacity of 10800 EP. The capacitors need only be about 10% full.

Agreed, and I guess this numbers match the formula I gave (2x0.01MJn, though I already featured the 2 in the 0.02 instead 0.01 when writting it). Did I miss anything here?

 

[AnotherDilbert]

In fact, I still think I quoted all the relevant part to answer the question (remember it was How much energy for jump?).

While the rest you posted is interesting, IMHO it adds nothing to answering the question, and I try to limit my quotes (mostly from published and IP protected material) to the strict minimum to make my point. Maybe I’m too prudent on it…

As the JTAS article makes clear, the energy for the jump comes from consumption of the jump fuel, not just routine power from the PP. The context of the OP was jumping without jump fuel.

BG need to have fuel to jump despite having enough power on your sinks vs Annic Nova not needing the fuel exactly in the same situation.


At least I (and for the discussion there have been for long here, I guess many others) see it as contradictory…

There is no contradiction, it's not exactly the same. HG has no rules for Collectors, hence no rule for when a Collector-equipped ship can jump.

As the energy for the jump comes from the power system (whether fusion, anti-matter or collector), the jump would presumably require a full amount of LHyd fuel, AM pellets, or a charged collector respectively.

Agreed, and I guess this numbers match the formula I gave (2x0.01MJn, though I already featured the 2 in the 0.02 instead 0.01 when writting it). Did I miss anything here?

You stated:

This has been discussed for ages, as information is contradictory, as there’s no consensus about how much jump fuel is used to power the jump.

I pointed out that the amount of energy the BG needs to provide is nowhere near enough to fill the jump capacitors, hence no suggestion that jump fuel would not be necessary.


There is still no suggestion, that I can find, that a ship can jump without the appropriate power system and fuel, pellets, or charged collector as appropriate.

 

[kilemall]

The morale of the story is: Don't dig too deeply into jump physics, it doesn't add up...

Stare too deeply into jump physics, and Grandfather stares back.

 

[AnotherDilbert]

Stare too deeply into jump physics, and Grandfather stares back.

If you're lucky...

 

[Spinward Flow]

In fact, I still think I quoted all the relevant part to answer the question (remember it was How much energy for jump?).

Jump (nominally) requires EP AND FUEL ... so when you cherry pick your way into asserting that "fuel is irrelevant" you open yourself up to skeptical responses from people who know better.

The question you should have been asking is ... "why is fuel necessary?" ... rather than taking the stance that fuel consumption was irrelevant.



The real bottleneck is the jump capacitors, since they have a clearly defined capacity limit (36 EP per ton of jump capacitors) and they require specific minimum of power pre-loaded into them in order to perform their role properly.

For convenience of analogy, I'm thinking of the EP (not fuel) requirement as being akin to "pre-heating the battery" on a Tesla groundcar prior to supercharging ... which is done to "condition" the battery for optimal power transfer rates that won't damage the engineering. I'm sure that at least a few of our forum posting regulars here have at least a passing familiarity with how supercharging works, even if you don't own a Tesla yourself (you probably know someone who owns one and has done it, etc.).

The numbers work out to being 18 EP of max capacity per 100 tons of starship per parsec ... but a starship's power plant only needs to provide 2 EP of output per 100 tons of starship per parsec over 2 combat turns in order to ENABLE a jump to be attempted. This then leaves 18-2=16 EP of "unused headroom" in capacity, which seems like an oddly LARGE MARGIN if it's just there for "safety" as opposed to being something that gets routinely used.

The obvious implication (is obvious) then becomes that the 16 EP of "unused headroom" per 100 tons of starship per parsec to be jumped IS NECESSARY SOMEHOW in a way that correctly "load balance matches" what is needed in order to jump. How does that 16 EP of "unused headroom" in capacity get filled? By means of a "controlled power spike overdrive" of the starship's power plant that can deliver the necessary power needed (well in excess of nominal output) for a very short duration (a few minutes) which while intensely fuel INEFFICIENT can get the job done. One of those "stupid but works, may be stupid, but it still works" kinds of deals.

My personal interpretation is that although a fusion power plant can deliver the necessary power OUTPUT needed for the jump drive to "do its thing" successfully, the actual "yield" of a fusion power plant in this "wasteful overdrive" condition is basically DIRTY POWER, as opposed to CLEAN POWER.

Basically ... this type of thing, to make it more obvious what I'm talking about:

The 16 EP of "unused headroom" per 100 tons of starship per parsec then ISN'T being used for a (pure) "fill then dump" all at once type of purpose or use case. It's not like the 10 tons of fuel per 100 tons of starship per parsec is being used to generate a (mere) 16 EP in a sudden overdrive of output power spike which then gets rapidly discharged in order to energize the jump drive in order to jump.

In my personal interpretation ... the 16 EP of "unused headroom" per 100 tons of starship per parsec is needed for POWER CONDITIONING so as to smooth out the "noise" of the "dirty electricity" output (as demonstrated in the image above) into something much more finely controlled and precise. The ACTUAL QUANTITY OF POWER being delivered is going to be WELL IN EXCESS of a mere 16 EP within a few minutes () but the TOLERANCE around that output is going to be within +/- 8 EP which it is then the responsibility of the jump capacitors to "smooth out" into a usable power curve (that doesn't reliably misjump!).

So rather than the jump capacitors being a kind of "baseload storage" type of setup for a jump drive, instead the jump capacitors are just there to "tame the noise" in the staggering amounts of power being delivered to the jump drive. The jump capacitors are there to "clean up" the power spike from the power plant into something more controlled and precise that can be used by the jump drive reliably.



In other words, 10 tons of fuel per 100 tons of starship per parsec to jump DOES NOT EQUATE TO ... 16 EP of output to fill the jump capacitors to maximum and then dump a mere 18 EP "in an instant" in order to jump.

If anything, it probably means that 10 tons of fuel pwer 100 tons of starship per parsec to jump EQUATES TO ... hundreds of EP of output which then jump capacitors condition to be within +/- 8 EP of the desired throughput into the jump drive.



Additionally, consider that if jump capacitors yielded a higher power density than fuel, we'd be using "jump capacitor only drives" instead of fusion power plants on overdrive to generate the necessary power spike.

In other words, 10 tons of fuel yields more power for jumps than 10 tons of jump capacitors (360 EP).



If the ACTUAL amount of power that needs to be delivered to initiate a jump is actually (numbers pulled out of the air purely for illustration purposes) ... 1200 EP per 100 tons of starship per parsec ... in order to supply that quantity of power you can either:

1. Consume 10 tons of fuel per 100 tons of starship per parsec (construction cost MCr0 for fuel tankage)
2. Install 33.4 tons of jump capacitors having 1202.4 EP capacity per 100 tons of starship per parsec (construction cost MCr133.6)

In other words, it's entirely possible that the reason why we have "fuel consuming" jump drives, instead of "capacitor driven" jump drives, could simply be a matter of practicality in the engineering. Nuclear fuel is simply "more energy dense" than any kind of jump capacitor technology that's available ... in addition to nuclear fuel tanks being "cheap" to construct, while jump capacitor technology is really expensive.

Therefore, the "lots of fuel plus a few jump capacitors" winds up being the More Efficient Option™ from both an allocation of displacement AND construction costs consideration, relative to the alternative of "a little fuel plus lots (and lots) of jump capacitors" when it comes to deciding which path to pursue.



Note that this interpretation does not foreclose on the option of Collectors (such as the one used by Annic Nova), but rather relegates the Collector "branch" of engineering to a different "focus" of the tech tech tree (so to speak). Furthermore, note that the "3x the tonnage needed" illustrated above when looking at fuel vs jump capacitors is (ironically?) also mirrored in the displacement of the Annic Nova main computer ... which is (also) oddly 3x larger than it ought to be.

Coinkydink?

Magic 8 Ball says: Answer hazy. Try again later.

Incidentally, for anyone playing the Home Game™ with all this theorycrafting ... if we assume that "starship combat rounds" last 20 minutes (LBB5.80) that means that there are 36*7=252 combat rounds worth of duration per week. So a Collector on a starship that is generating 1 EP per combat round would collect 252 EP per week ... and after 5 weeks would have collected 252*6=1260 EP ... sufficient for a 100 ton starship to jump 1 parsec using a Collector ... assuming my 1200 EP per 100 tons of starship per parsec supposition above is even approximately correct (pass the entire salt shaker for that one ... ).



The one thing that we do know for sure is that (per LBB5.80) jump capacitors are NEEDED in order to be able to jump, but with the CT RAW for starship design, mere EPs "in the capacitors" IS NOT ENOUGH ... there is also a requirement for jump fuel in order to jump.

Annic Nova was an example of a Collector powered jump drive which we were given no construction rules for in CT. So Collector driven jump drives CAN WORK ... but HOW to make them work under CT was never adequately explained ... because doing so would "peel back the curtain" on how jump drives operate, which was a can best left sealed back in the days when CT was being published.