How do jump drives really work?

[rancke]

This applies to you more then me, what have you added to the discussion?

I've contributed the knowledge that the notion that a significant portion of the hydrogen is used as coolant is nonsensical, of course.

Except it looks like it already is canon:

So? I never said it wasn't canon. I said it was nonsense. Pointing out that it's canon doesn't refute that the fifth time any more than it did the first. If you want to refute it, you have to demonstrate through reasoned argument that it isn't nonsense. You may want to try that.


Hans

 

[Dragoner]

I've contributed the knowledge that the notion that a significant portion of the hydrogen is used as coolant is nonsensical, of course.


So? I never said it wasn't canon. I said it was nonsense.

It is a falacious argument since you are supposing a non-testable hypothesis and without any proof for your position.

Meanwhile, hydrogen is used as coolant today....so it is obviously not nonsense. What does seem to be happening is that you don't understand how that works, so nobody can understand, n'est-ce pas?

 

[rancke]

If you were to use more exotic coolants they MIGHT only be avalible at Class A starports. No Skimming or Ice cracking.

So? They would be available at Class A starports. And Class B starports. And any starport with enough trade and traffic to have regular freighters and liners visiting them.

Also How much harder/more expensive is it to get and hold Nitrogen vs Hydrogen today?

So let's say they use water instead. I've already been using that instead of nitrogen for my most recent posts. How much more expensive and difficult to get than liquid hydrogen do you think water is?

It may be better, and it might work, But is it really more economical?

Yes. See several of my previous posts.

Ships using this system would be stuck going from Starport A to Starport A. Pinning them down to higher Tech older developed routes. Not likely to be as oprofitable due to large volumes of traffic.

Well, they'd be restricted to visiting systems where they can get hold of water. Or to carry an extra load of water along on a jump. Not really a problem that would offset a major economic advantage.

If ships were to ply these routes saving money due to coolant savings then prices would also drop due to lower shipping costs. Carriers would drop prices trying to force out all non Nitro equipped carriers and that would become standard. At this point ONLY certain carriers could afford to deal in these systems and the system would suffer from the monopoly.

True. So basic economic forces would drive hydrogen-coolant-based ships out of business.


Hans

 

[rancke]

It is a falacious argument since you are supposing a non-testable hypothesis and without any proof for your position.

Meanwhile, hydrogen is used as coolant today....so it is obviously not nonsense. What does seem to be happening is that you don't understand how that works, so nobody can understand, n'est-ce pas?

I don't know if you're for real or not, but it's obviously an exercise in futility to argue with you. I shall stop wasting my time on you.

 

[Dragoner]

I don't know if you're for real or not, but it's obviously an exercise in futility to argue with you. I shall stop wasting my time on you.

It is rather hard to argue with facts.

 

[Ishmael]

Dragoner, I think it might be worthwhile to question a jump drive's ( sans attached power plant ) efficiency in order to gauge just how much waste heat needs to be dissipated.
If it turns out to be low enough ( though I doubt that it will be ), maybe the waste heat could be gotten rid of with radiators.
The same might be true for certain forms of power plants/supplies.

By basing an efficiency curve along the lines of T/(T+1), where T is related to tech level, the curve approaches 1 without ever reaching it ( nothing is 100% efficient ). Multiply this value by the maximum theoretical efficiency for the equipment to get final machine efficiency.

This could give an idea of how much better in performance a tech 15 jump-1 drive is when compared to a tech 9 jump-1 drive.

 

[aramis]

canon says hydrogen is used as a coolant
real world has areas where liquid hydrogen is used as a coolant
that should be good enough

if we get into actual real thermal management, I doubt the OTU ships, etc. would survive in its present form.

The only Real World place I've heard of Liquid H2 as coolant is in hydrogen burning rocket engines, and a few experimental stations where N2 isn't cold enough.

The fire and explosion risks generally see to that...

And on engines, using it for coolant does double duty: cools the nozzle, AND preheats the fuel. Kerosene engines have also done the same. But it's in a place where a failure to contain isn't much more risk than the engine itself having other failures.

The implication of the gravitic based drives in MT, non-TNETU TNE, and T4 is that mass isn't that much of a matter for starships; the drive is literally causing the ship to "fall" in the direction of thrust. Which makes the mass a matter of structural soundness and resistance to inertial forces.

Late CT implies same, but doesn't present it cogently, and T20 essentially uses HG design and a different combat system.

@ Hans: for throw-away cooling, LHyd is useful but bulky; N2 has a wider regime and is fairly easy to skim for; much of what is being filtered out to get H2 from gas giants is ammonia (NH3) and methane (CH4)... it would take more processing time to accumulate the nitrogen... but it's no harder to do, just lower return per unit time/energy. Also why I never require skimmers to worry about replacement nitrogen when GG refueling... it's a byproduct of the purification plant cracking the ammonia.

Then again, the fuel use rates for power plants are pretty damned high (or the energy return is extremely low).

 

[Ishmael]

The only Real World place I've heard of Liquid H2 as coolant is in hydrogen burning rocket engines, and a few experimental stations where N2 isn't cold enough.

http://en.wikipedia.org/wiki/Hydrogen-cooled_turbogenerator

Then again, the fuel use rates for power plants are pretty damned high (or the energy return is extremely low).

I agree with that totally. In fact, I view that as evidence that only some of the 'hydrogen' is fused while the rest is coolant or some sort of working medium that isn't contributing to power generation, but may be in use for controlling the reaction in some fashion.
In any case, I feel that the whole 'fuel is all hydrogen' is a game abstraction which simplifies the idea that there are several gasses and liquids in use. Purified fuel gives you an amount of clean hydrogen and appropriate types and mixtures of coolants, etc. and that wilderness refueling gives dirty hydrogen ( not pure, but not bad enough to cause failure ) and a questionable mix of 'stuff' for coolant which may or may not be adequate for the job...kind of like putting seawater in your car's radiator as opposed to a proper mix of antifreeze and pure water; it'll work, but will eventually cause problems/failure.

power plant efficiencies will have a huge effect on cooling requirements.
modern day combined cycle have only recently reached above the 60% mark, which is far less than Trav's apparent assumptions. Clearly Trav plants are using still-to-be-invented methods.

I'm afraid I don't use reactionless drives imtu.
I've already made a spreadsheet to figure structural aspect in ship design.
imtu, mass matters...quite a lot

 

[Dragoner]

Dragoner, I think it might be worthwhile to question a jump drive's ( sans attached power plant ) efficiency in order to gauge just how much waste heat needs to be dissipated.
If it turns out to be low enough ( though I doubt that it will be ), maybe the waste heat could be gotten rid of with radiators.
The same might be true for certain forms of power plants/supplies.

By basing an efficiency curve along the lines of T/(T+1), where T is related to tech level, the curve approaches 1 without ever reaching it ( nothing is 100% efficient ). Multiply this value by the maximum theoretical efficiency for the equipment to get final machine efficiency.

This could give an idea of how much better in performance a tech 15 jump-1 drive is when compared to a tech 9 jump-1 drive.

I agree in theory. However, to do the math it would be good to know how the hydrogen fusion plant actually generates power and what the actual power needed to go into jump would be.

So by the Carnot cycle: Nth =< 1- 3K(temp of space)/5,000,000K (Hydrogen Fusion min w/ quantum tunneling) it becomes a super efficient powerplant at 99%. This would say, that not much cooling is actually needed, but we still don't know the work over time. An earlier post suggested somewhere around 900Mw? Which comes to 3,240,000,000 kilojoule/hour, so 1% is 32,400,000 Kj/H. We can cut down on this amount by cutting the usage rate and putting that volume towards the coolant side, still it seems not much hydrogen is actually needed for the fusion process itself. Wiki states that: The gigajoule (GJ) is equal to one billion joules. Six gigajoules is about the amount of potential chemical energy in a barrel of oil, when combusted. thus in conversion it is 32.4 gigajoules of energy that must be dissipated, eg less than six barrels of oil. Somehow that seems wrong to me, though maybe the drive is amazingly efficient? Or maybe my mind is already down at the pub. All in all, talking thousands of years in the future, it does seem possible.

*Ok, went back and it looks like per McPerth's post that I got the Megawatts off by an order of a thousand, so maybe the thermal energy to be dissipated is on the order of 5,500 barrels of oil. Now that seems a lot, still though, hydrogen is almost free; I would almost hazard to say that the loin's share of the LH2 is used for the cooling process.

 

[Ishmael]

I'm not sure I am in agreement with the numbers for carnot eff.
While the numbers are good ( although I'd put the Low temp res at ~14K as temp of liquid h2 ), I'm not sure that they reflect the efficiency related to converting the heat from the fusion process to useful power for other equipment.
For that, I'd think the low reservoir would be the temps of the radiators (~1000K? cherry red steel ) and the high temp reservoir at ~2500K ( temp should probably be lower than melting point of conversion machinery's materials ). This would probably end up being analogous to steam turbines or other heat engine. ~1-(1000/2500)= ~60%

Another more efficient method under study is direct conversion of kinetic energy of particles to electric potential. The following suggest ~90% may be possible.
http://www.visionofearth.org/industry/fusion/how-do-we-turn-nuclear-fusion-energy-into-electricity/

but even these numbers depend on the ability to capture the heat or particles in a useful fashion.
which may be less than ideal. Perhaps this is the stage where my experimental tech progression would fit;
introduced at T9, therefore at T9, the first tech level its available; efficiency would be 1/(1+1) times 90%...the tech 9 power plant would be 45% efficient at converting the energy of fusing hydrogen to useful energy. T15 is the 7th tech level that fusion power plants are available, therefore 7/(7+1) times 90% = 79% efficient.

The fusion reaction by itself is 99.999% by carnot eff., so call that 100%
From that, we should be able to gauge just how much h2 is actually fused as fuel... the rest is non-fuel or coolant. I suspect that radiators and coolant together as envisioned by trav won't be enough, but I need to work out the numbers.

naturally, the waste heat also increases a ship's signature to sensors.

 

[shadowcat20]

At this point it is looking like Canon does not work by current standards and we have to resort to Handwavium.

What I have learned so far is H2 can be used as fuel but in small amounts.

H2 can be used for cooling but other things work better.

Caps are needed for the jump process but we never figured out if that was all that was needed.

All the H2 is used in the process so jump tanks are no problem.

Canon is screwed up because the writers of old did not compare notes and have a grand design to all work off of.

We can argue the fine points for years....

 

[aramis]

At this point it is looking like Canon does not work by current standards and we have to resort to Handwavium.

What I have learned so far is H2 can be used as fuel but in small amounts.

H2 can be used for cooling but other things work better.

Caps are needed for the jump process but we never figured out if that was all that was needed.

All the H2 is used in the process so jump tanks are no problem.

Canon is screwed up because the writers of old did not compare notes and have a grand design to all work off of.

We can argue the fine points for years....

The simplest solution is to just deem that the Annic Nova either doesn't exist, or is TL22+, in the OTU.

This leaves the issue of fuel burn. Since HG deems power AND fuel are required, as does TCS makes it clear drop tanks can be used then dropped just prior to jump. MGT and MT both agree on the drop tank issue, as well.

What we can't say with any certainty is how the fuel is used, just that it is. Which means we know that it's going to be using multiple 20-30cm connections (probably 1 20cm per 10 tons, or 1 30cm per 20...) and it's moving a LOT of fuel, which also means it's noisy.

 

[shadowcat20]

As a side note, All the references I can find call H2 "fuel" rather than "coolent" so this hints that the entire coolent sideshow is a minor consideration compared to the main use of H2. To run the jumpdrive.

Also, who is to say the jump drive is not just a turbocharger for the powerplant? Helps the plant to burn faster generating more power.

I know, just the first edition of LBBs maybe....

The thread has served it's use though. All of us came up with some great ideas and lots of useful facts popped up.

 

[aramis]

As a side note, All the references I can find call H2 "fuel" rather than "coolent" so this hints that the entire coolent sideshow is a minor consideration compared to the main use of H2. To run the jumpdrive.

Also, who is to say the jump drive is not just a turbocharger for the powerplant? Helps the plant to burn faster generating more power.

I know, just the first edition of LBBs maybe....

The thread has served it's use though. All of us came up with some great ideas and lots of useful facts popped up.

Earlier drafts of T5 took the turbocharger approach. I've not waded enough into the current draft of ACS to know if that still holds true.

 

[mike wightman]

The simplest solution is to just deem that the Annic Nova either doesn't exist, or is TL22+, in the OTU.

This leaves the issue of fuel burn. Since HG deems power AND fuel are required, as does TCS makes it clear drop tanks can be used then dropped just prior to jump. MGT and MT both agree on the drop tank issue, as well.

What we can't say with any certainty is how the fuel is used, just that it is. Which means we know that it's going to be using multiple 20-30cm connections (probably 1 20cm per 10 tons, or 1 30cm per 20...) and it's moving a LOT of fuel, which also means it's noisy.

Sorry but no.

The Annic Nova is not some super high tech relic.

It's just a variant on how the jump drive works within the OTU - something Marc has mentioned time and again that there are alternative ways to make jump drives work.

The solar collector system on board the Annic Nova is one such alternative , there may be others.

The problem stems from later canon where writers didn't read up on the subject or just used their already ingrained erroneous ideas.

The definitive work on jump drive is Marc's article in JTAS 24 - use that as your starting point and work from there.

We know that solar collector based jump drives charge the jump engines over a period of weeks and that the collection sails an machinery take up a space equivalent to a hydrogen based jump drive's fuel requirement to balance things in the meta game.

We know the 3rd Imperium and all her interstellar neighbours favour the hydrogen based system, probably because of the fast turn around time.

We know that the hydrogen based jump drive has several subcomponents - what muddies the waters is the original jump drive being it's own power plant while later versions require a separate power plant.

But here's the thing...

In CT the jump drive is big, much bigger than the maneuver drive and power plant combined.

In HG the jump drive becomes much smaller but now requires a power plant to feed it - and yet the jump fuel required stays the same.

Solution - there are actually 2 types of hydrogen based jump drive in use in the OTU.

The CT version which includes its own power plant and is big, and the military grade HG jump drive that requires a separate power plant. The revised edition LBB2 rule that a jump drive requires a power plant should be scrapped - that's the really contradictory bit and allows the x-boat to function as originally designed.

During a jump preparation sequence on HG based jump drive the ship's power plant operates at maximum output to charge the jump capacitors, using fuel from the jump drive allocation, a lot of it being used as coolant.

And yes I accept there are better coolants but you already have liquid hydrogen on board for the power plant and jump drive energy generation so why complicate already extremely intricate engineering by having yet another engineering system on board?

Never try to justify things using real world physics of heat capacity etc. because the OTU isn't the real world (and no - water would be a lousy coolant because at the temperatures of a fusion reactor you are going to end up with incredibly hot monatomic oxygen and hydrogen - now that really is an explosive mixture ).

Actually the idea of a more efficient coolant system may be an alternative jump drive that also exits somewhere within the OTU - might be fun to come across such a thing at some point.

And finally a real answer to Hans over a fusion power plant powering a solar collector accumulators - it has to be done slowly, and it can't be done in port because there is no way the port authorities are going to allow a fusion reactor to be running at peak output for 1-6 weeks depending on charging time. So you are adding at least a week to your jump cycle - 1 week in jump - 1 week travelling to/from world finding cargo passengers etc - 1 week charging jump accumulators - 1 week in jump.

Hmm - a hydrogen based jump drive merchant can jump ever fortnight a hybrid can do it every 3 weeks - there's your economic reason for going with hydrogen.

Why not keep the jump ships in orbit or even at 100d and have interface craft carry cargo and passengers? Only the big boys could afford this infrastructure and is similar to the LASH system that GT introduced IIRC.

And it would probably require another power plant to be available to run the rest of the ship systems.

Another thought - the slow charging accumulators are probably the big part of the sollar collector based jump drive. So you could do away with the collector sail and its deployment machinery but would that give you enough spare room to fit a power plant and its fuel?

If I were to design construction rules for sollar collector based jump drives compatible with LBB2 or HG I'd make sure that you would only get enough space for a small power plant to preserve game balance. After all the builders of the Annic Nova could put fusion plant on the sub-craft but not the main ship.

This suggests to me that you wouldn't have enough space.

 

[McPerth]

So? They would be available at Class A starports. And Class B starports. And any starport with enough trade and traffic to have regular freighters and liners visiting them.


So let's say they use water instead. I've already been using that instead of nitrogen for my most recent posts. How much more expensive and difficult to get than liquid hydrogen do you think water is?


Yes. See several of my previous posts.


Well, they'd be restricted to visiting systems where they can get hold of water. Or to carry an extra load of water along on a jump. Not really a problem that would offset a major economic advantage.


True. So basic economic forces would drive hydrogen-coolant-based ships out of business.


Hans

And whould the Imperium allow that?. This whould mean that most of systems with starport C- whould be out of trafic, and so fall into isolation.

I've read somewere (Sorry, I don't remember if a challenge, JTAS, MTJ or elsewhere) that Imperium favors low jump merchants just to keep many systems that are not too profitable for trade visited just beause they are on path, and so it may make it economic to visit them and see if some profit might be done from the stop.

If LN2 cooled ships took off LHyd colled ones, traffic whould move out of those systems, and J1 ships whuld disapear, as, if you must stop on A or B class starports to refill your coolant, J1 (and even J2) isn't deasible out of clusters.

Yes I know those are political reasons, but Imperium is a political entity, and its most important interest is to control ship lanes and keep trade going.

The only Real World place I've heard of Liquid H2 as coolant is in hydrogen burning rocket engines, and a few experimental stations where N2 isn't cold enough.

The fire and explosion risks generally see to that...

And on engines, using it for coolant does double duty: cools the nozzle, AND preheats the fuel. Kerosene engines have also done the same. But it's in a place where a failure to contain isn't much more risk than the engine itself having other failures.

The implication of the gravitic based drives in MT, non-TNETU TNE, and T4 is that mass isn't that much of a matter for starships; the drive is literally causing the ship to "fall" in the direction of thrust. Which makes the mass a matter of structural soundness and resistance to inertial forces.

Late CT implies same, but doesn't present it cogently, and T20 essentially uses HG design and a different combat system.

@ Hans: for throw-away cooling, LHyd is useful but bulky; N2 has a wider regime and is fairly easy to skim for; much of what is being filtered out to get H2 from gas giants is ammonia (NH3) and methane (CH4)... it would take more processing time to accumulate the nitrogen... but it's no harder to do, just lower return per unit time/energy. Also why I never require skimmers to worry about replacement nitrogen when GG refueling... it's a byproduct of the purification plant cracking the ammonia.

Then again, the fuel use rates for power plants are pretty damned high (or the energy return is extremely low).

As explosive risk of using Lhyd, when we talk about real world (TL7-8 Solomani), we're talking about working on an atmosphere rich in oxigen. When we talk about traveller jump, we're talking about working in vaccum, so I see the explosion risk quite diminished just for lack on oxigen.

About skimming N2 from the monia taken out by the fuel purifiers, I think the percentage of amonia is in the higher strates of a GG atmosphere, where skimming is done (its molecular weight of 17, against 2 of H2 whould keep it deeper, IMO) whold be rather low, yet that's mere speculation and no, I haven't any scientific data to support it (aside from the molecular weight stated before). So I think the quantity of N2 (or amonia, which is a good coolant, if rather corrosive) skimmed this way wouldn't be enough.

Consider the US Navy as another alternative. As I understand it, pretty much everything on an aircraft carrier runs on Jet Fuel. The planes, the forklifts, the other vehicles. Anything that needs liquid fuel, is tuned for Jet Fuel, thereby simplifying deployment and logistics. Again, in the larger, generic world, these vehicles aren't appropriate. But for the World of the aircraft carrier, it makes complete sense.

I didn't know the fact, but that's another point as the use of LHyd whould be feasible. Using Jet Fuel for what could work on Diesel is quite expensive and (if I'm not wrong) dangerous, but is used just to simplify logistics. So I think whould happen on using LHyd as coolant when you have to carry a fairly good quantity anyway.

 

[McPerth]

One thing we have to take in account when speaking about coolants is that cold, as such, doesn't exist. When you want to heat something, you can give it heat, as energy, either converting other energies or producing it by chemical or physical methods. When you want to cool something, the only choice you have is to take heat away from it.

As long as I know (I'm not an expert), to do that, you must trasfer this heat to another mater or to give it away as IR radiation.

The latter way is quite slow, as you can only produce so much IR radiation, and, even making yourself a true IR beacon (not too big a problem when leaving system), I don't think it's possible to cool a JD in the short span of time you go into jump.

The former one needs some mater to transfer the enregy to, somenting not aailable on vaccum, so we must use some coolant and release it to space, as if we keep it, we keep the heat on the ship.

The black globe rules in HG and MT say that if you have enough energy stored and fuel on tanks, you can jump. What I couldn't find on rules is how much energy is enought for a jump. I asumed (as many other people, for what I've read on this thread) that this means the jump sinks are full (8775-9000 Mw h/ton as we calculated, see my entry on Dec 31, page 4 this thread).

This means that a Scout or free trader releases as much energy as a 3 kton nuclear bomb to jump. I don't dare to calculate the equivalence of ah Azhanti, let alone a Tigress.

If you have to cool all this energy on 40 min (the time given as needed for a jump), you must use lots of quick coolant and release it, so I don't think you can take the coolant with you for other jumps.

As an aside, if the vast amount of LHyd is used for cooling, then someone with eyes on the jumping ship would likely see some indication of the all the fuel being jettisoned prior to jumping.

True, you'll leave quite a big cloud of heated gas, but I think it whold dissipate quite quickly, and, anyway, as you jump, being detected is not a big problem if you're no longer there when anyone can react.

I'll patiently await the armchair thermodynamics and fluid mechanics specialist to tell us how much heat the remaining LHyd consumed in the process would absorb, who knows, maybe it all balances out in the end . I never looked much at thermodynamics.

Well, It seems your challenge has been answered :rofl:

 

[rancke]

Well, they'd be restricted to visiting systems where they can get hold of water. Or to carry an extra load of water along on a jump. Not really a problem that would offset a major economic advantage.


True. So basic economic forces would drive hydrogen-coolant-based ships out of business.

And whould the Imperium allow that?

The question wouldn't even arise. The outcompeting would have happened 10,000 years ago. My whole argument is based on the proposition that if a significant amount of the hydrogen we know is expended in a jump is expended as coolant, then there are much better alternatives available from the moment mankind -- make that sophontkind -- begins to design it very first jump-capable vessel.

This whould mean that most of systems with starport C- whould be out of trafic, and so fall into isolation.

Unless the systems with Class C- starports had water available. Or the profits to be made on a return trip to said system was enough to finance carrying a double load of coolant water. Which is would be if a trip to the system with a hydrogen-coolant ship would be profitable. Not really a problem that would offset a major economic advantage.

(Didn't I just say that? I did! I did! I did just say that! And you actually quoted me saying it!)

I've read somewere (Sorry, I don't remember if a challenge, JTAS, MTJ or elsewhere) that Imperium favors low jump merchants just to keep many systems that are not too profitable for trade visited just beause they are on path, and so it may make it economic to visit them and see if some profit might be done from the stop.

That's a proposition propounded by some fans to explain some features of the background (mostly related to communication times). It contradicts other parts of canon, though admittedly there's not a lot of it (The rules allow PCs with the necessary funds to order a jump-6 ship at any Class A starport in the Imperium and there's a mention of Oberlindes having a number of J5 couriers). However, it doesn't actually work to explain away the oddities, so I prefer to stick to the assumption that more than a century after it was invented, jump-6 is no longer out of bounds for civilians (if it ever were).

In this case it's moot, anyway, because jump-2 and jump-3 is superior to jump-1 over any distance greater than one parsec (depending on assumptions they are either faster and economically more or less the same or both faster and cheaper), so those systems would mostly be bypassed anyway. And there is plenty of evidence for civilian jump-2, -3, and -4 traffic.

If LN2 cooled ships took off LHyd cooled ones, traffic whould move out of those systems, and J1 ships whuld disapear, as, if you must stop on A or B class starports to refill your coolant, J1 (and even J2) isn't feasible out of clusters.

Not true. Alternately cooled J1 ships would also be more economic than Hyd-cooled ones, so anything that was economic for the latter to do would be even more economic for the former to do.

And it still wouldn't address another canonical fact that I've brought up several times already, only to have it carefully ignored, the fact that the rifts are supposed to be major barriers to traffic. Which they would be if you could build a ship with room enough for four or five jumps worth of coolant.


Hans

 

[rancke]

Sorry but no.

But yes.

The Annic Nova is not some super high tech relic.

No, it's an anomaly featured in one very early adventure that does not fit with the vast majority of other canon. Accepting it would require invalidating some much more important parts of canon for practically no gain. So it's not worth accepting.

It's just a variant on how the jump drive works within the OTU - something Marc has mentioned time and again that there are alternative ways to make jump drives work.

One time. He mentioned it once. Presumably without considering the logical ramifications. AFAIK, neither he, nor any of the people he has authorized over the years to write official Traveller material has ever mentioned it again.

And even if Marc Miller said it once a day and twice on sundays, it would still not be compatible with the rest of canon.

The problem stems from later canon where writers didn't read up on the subject or just used their already ingrained erroneous ideas.

How canon evolved is irrelevant. The important thing is that it did evolve and what it evolved into.

In CT the jump drive is big, much bigger than the maneuver drive and power plant combined.

In HG the jump drive becomes much smaller but now requires a power plant to feed it - and yet the jump fuel required stays the same.

Solution - there are actually 2 types of hydrogen based jump drive in use in the OTU.

Not a solution, because Book 2 ship construction is incompatible with the established background information for the OTU (most egregious example: dates for when jump-2, -3, -4, -5, and -6 was discovered).

And yes I accept there are better coolants but you already have liquid hydrogen on board for the power plant and jump drive energy generation so why complicate already extremely intricate engineering by having yet another engineering system on board?

Because it would give a significant increase in volume available for other purposes, upping its earning potential considerably.

Never try to justify things using real world physics of heat capacity etc. because the OTU isn't the real world (and no - water would be a lousy coolant because at the temperatures of a fusion reactor you are going to end up with incredibly hot monatomic oxygen and hydrogen - now that really is an explosive mixture ).

Always try to justify things using real world physics, because while the OTU is indeed imaginary, the imaging includes being very much like the real world except in a few select instances. Of which jump physics is one but the physical properties of the elements and other substances isn't.

And finally a real answer to Hans over a fusion power plant powering a solar collector accumulators - it has to be done slowly, and it can't be done in port because there is no way the port authorities are going to allow a fusion reactor to be running at peak output for 1-6 weeks depending on charging time. So you are adding at least a week to your jump cycle - 1 week in jump - 1 week travelling to/from world finding cargo passengers etc - 1 week charging jump accumulators - 1 week in jump.

I'll accept that it has to be done slowly as it doesn't contradict anything else we know. The upper limit on the limit on a jump-1 drive is one week divided by five, since the Annic Nova can recharge enough to do a jump-2 and a jump-3 in one week. So, the Annic Nova jump drive (or rather, the capacitors that activate it) has to be charged over 34 hours.

Oh, the capacitors has to be charged a full week and the fact that the AN's solar sail can gather enough to power a J2 and a J3 jump in a week merely means that the solar sails and the capacitor banks are five times as large as necessary for a jump-1 ship?

Very well. So you empty the capacitors and enter jumpspace. You now have a week to recharge the capacitors while you're in jump...

Oh, for some reason the recharging won't work in jumpspace?

Very well. That does put the kibosh on regular commercial use of the ANJD, at least for the lower jump drives. Not so much the freetraders who already spend a week in each system (I don't buy the notion that "the authorities" would forbid fusion reactors from run while ships are in port[*]), but for the regular ships that only stay in a system for a couple of days before jumping out again. What a pity there's no other application for this drive.

[*] And if they did, they surely wouldn't object to the ship hooking up to the starport power grid and recharge that way.​

Except, that is, to cross rifts and go through systems with no ready source of hydrogen. Why, you could cross the Great Rift in half a dozen jumps instead of having to spend a couple of dozen jumps going around. I think you might even save a few hours by doing it that way, don't you?

It's a real head-scratcher to imagine why no one does that, isn't it? Could it be that the ANJD doesn't actually exist in the OTU, whatever other Traveller universes it may exist in?

Hmm - a hydrogen based jump drive merchant can jump ever fortnight a hybrid can do it every 3 weeks - there's your economic reason for going with hydrogen.

It would not be enough to do provide a reason in the case of the higher jumps. A jump-4 that can jump once every three weeks carrying a 60% payload (note: figures are not exact) would outcompete one that can jump once every two weeks with a 30% payload.


Hans

 

[HG_B]

Always try to justify things using real world physics, because while the OTU is indeed imaginary, the imaging includes being very much like the real world except in a few select instances. Of which jump physics is one but the physical properties of the elements and other substances isn't.

In that case, non JD fuel wouldn't be carried as LHyd but probably as H2O...