Capacitors vs. Hydrogen Dump in Ship Design

[DCAnsell]

I'm sure this has been discussed before, but I wanted to get some comment on something I'm working on as part of the tech framework for my own non-OTU setting.

As some of you may know, one of my primary criteria for designing stuff is the ability to use as much published material as possible, especially things like ship designs, with only minimal need to tweak for inclusion in my setting.

That said, the following:

Jump Capacitors: In the Shackled Horizons setting, jump drive works similarly to the way it does in stock Traveller, except that instead of dumping hydrogen and creating a jump bubble, ships instead use high energy capacitors to 'dump' energy into the jump engine and jump grid of their ship, creating a jump bubble and sending them through jump space.

It takes a LOT of energy to create a jump bubble, and the capacitors to allow a jump to occur take up (shockingly) exactly the same space as jump fuel tankage does in the OTU. The mass is higher than tanks full of hydrogen, even with allowance for waste space, but that's okay, I think, since actual weight/mass isn't directly accounted for in the ship design sequence.

Entering and leaving jump are relatively high energy events, significant enough to be noticed at long distances, even by relatively crude sensor equipment. "Stealth" jump drives are simply not possible, under current technologies available in the setting.

Some limitations:

Interacting with jump space creates energy imbalances and other weird effects in the ship's jump grid. Re-entering normal space with these effects destabilizes the ship's jump grid. A 'destabilized' jump grid cannot sustain a jump bubble. To re-stabilize the grid requires being within a substantial gravity well, as well as time (measured in hours) and some effort by the ship's engineering staff. A significant fubar by the engineers can potentially result in radiation effects within the ship, though this is quite rare. Entering a significant atmosphere with a destabilized grid is also rather hazardous, since the chances of those radiation and other bad effects become greatly higher.

Recharging the capacitors also takes significant time, generally around 168 hours for a power plant capable of powering a 1-G rated GAHET drive (GAHET= Grav-Assisted High Energy Thrust, usually called the 'gat' or just maneuver drive) in a particular sized hull. This time is divided by 4 if the GAHET drive is not in use. It's not common, but some ships have been designed with a second power plant to facilitate capacitor recharge.

Consequences:

1) Gas Giants in and of themselves are no longer choke points in a star system, since profoundly large amounts of hydrogen fuel are no longer required to jump. Hydrogen fuel is still required for the GAHET thrusters, but the quantities are much, much lower, roughly equivalent to the normal stock power plant fuel tankage to get (14 x G-rating of maneuver drive) G-hours of thrust. Power plants themselves do not require hydrogen fuel, instead operating for one year between replacement of fuel elements during annual maintenance.

2) The only way to cross voids and rifts is to find a brown dwarf or other source of significant gravity well, to allow for jump grid stabilization. Such locations, if known, are always closely watched, and often are sought after secrets.

3) In addition to thruster fuel, class A, B, and C starports can offer 1 day capacitor recharges, at cost scaled to the energy needs of the ship. Orbital ports of those classes also might offer jump grid stabilization services, which a lot of commercial vessels take advantage of.

I'm not a scientist, or an engineer, but does the above seem workable without utterly smashing suspension of disbelief?

 

[klingsor]

That amount of capacitors is, as you said, going to store a lot of energy. If anything happens to them very, very bad things will happen to the ship so it would seemingly make a ship with charged capacitors quite fragile compared with plain vanilla Traveller ships. Any other drawbacks I can think of you have already caught.

 

[DCAnsell]

That amount of capacitors is, as you said, going to store a lot of energy. If anything happens to them very, very bad things will happen to the ship so it would seemingly make a ship with charged capacitors quite fragile compared with plain vanilla Traveller ships. Any other drawbacks I can think of you have already caught.

That's a good point. On the other hand, uncharged capacitors probably make reasonably good impromptu armor for soaking damage.

That leads to some interesting choices tactically. Do you keep your charge, and try to jump away, or do you dump and fight? That might also mean that only orbital ports would charge capacitors, and most worlds might not even allow a ship with charged caps to land. It would definitely add to the case for not putting the starport in the center of your biggest city

The other option is to postulate very safe capacitors, both structurally and in terms of how and under what conditions the energy will discharge. For example, maybe they are designed to vent outwards if ruptured, though I'm not sure how practical that would be.

 

[Rikki Tikki Traveller]

The Jump Grid would also be fragile and subject to easy damage (assuming it is on the outside of the hull and armor). Hull hits would increase the chance of a misjump.

 

[DCAnsell]

The Jump Grid would also be fragile and subject to easy damage (assuming it is on the outside of the hull and armor). Hull hits would increase the chance of a misjump.

Another great point. I think also once you'd lost half your hull points, jump would be pretty much impossible/unsurviveable.

 

[Gee4orce]

I think the requirement for a gravity well to 'stabilize the jump grid' or whatever, is clearly there just for 'game balance' reasons. For me it breaks the believability a little bit. I suppose you could change the rationale behind it but keep the requirement to have to visit a gravity well for some reason or other.

Other than that I quite like this approach. It's no more or less silly than a ship having to dump tons and tons of H2 into space every time it jumps.

 

[Gee4orce]

The Jump Grid would also be fragile and subject to easy damage (assuming it is on the outside of the hull and armor). Hull hits would increase the chance of a misjump.

Another great point. I think also once you'd lost half your hull points, jump would be pretty much impossible/unsurviveable.

Incidentally, this is no different to the standard Traveller interpretation of how Jump drives work - a grid embedded in the hull. There's nothing in the rules that I can remember to say that hull damage increases the chance of a misjump, but it seems like an obvious and interesting thing to include.

 

[Rikki Tikki Traveller]

Gee4orce, you are correct and I hesitated to even bring up that point. There are YEARS of arguing over whether a Jump Grid is a valid idea for Traveller given exactly what you say, hull hits do not affect Jump performance. But, Jump Grids are Canon in GDW material.

MY point was that if you are going to change the Jump Drive anyway, then you might as well account for all the issues correctly.

IMTU Jump Grids don't exist. I use a different explanation for how it works, but the in-game effects are the same as the Official Jump Drive.

 

[Ishmael]

imtu, jump grids are used and hydrogen bubbles are not ( actually, I never heard of hydrogen jump bubbles in the older material I own; hydrogen is dumped as a form of 'evaporative' cooling in that its for dumping off waste heat.

the jump grid is embedded in the hull itself and thus only takes damage when the hull is penetrated. that's why MT and HG don't have jump damage for hull hits, but do for internal explosions... a hull hit doesn't penetrate the mahin hull and thus doesn't damage the embedded grid.

Other than that, I use mass instead of volume to figure jump performance ( and not in whole numbers --- 2 decimal places because I use a 3d space and those decimal places might count, ). I'm using that because gravity wells affect jump-drive and therefore the mass that forms the gravity wells affect jump-drive.

 

[Dave Chase]

Jump Grids and Jump Bubbles are discussed in T5.

Depending on which Playtesters, owners of the T5 Material yell the loudest about the Jump technobabble will depend on if Jump Bubbles truely exist.

The main issue is if there is a Jump Grid (part of the Hull) and Jump Bubble (something different than the grid) then they must have some 'technology' or effect reasons and be different too.

(sigh)

Dave Chase

 

[kristof65]

Couple of comments:

Recharging the capacitors also takes significant time, generally around 168 hours for a power plant capable of powering a 1-G rated GAHET drive (GAHET= Grav-Assisted High Energy Thrust, usually called the 'gat' or just maneuver drive) in a particular sized hull. This time is divided by 4 if the GAHET drive is not in use. It's not common, but some ships have been designed with a second power plant to facilitate capacitor recharge.

I can't speak for YTU, but real world capacitors really don't take that long to charge/discharge. Even the huge room size ones used on things like VLF Transmitters. It's one of the advantages of capacitors over batteries, the disadvantage is that they often can't hold their charge stable for a long period of time.

Often times how quickly a capacitor can be charged is really dependant upon the amount of power available to charge it to full potential. A more beleivable restriction would be a charge time of 1 hour per ton of Capacitor divded by the power plant potential. So a ship with 40 tons of capictors could charge in 40 hours if it had a Power Plant rating of 1, 20 hours if it had a rating of 2, and so on. Actually, I'd go 10 minutes per ton - caps can charge pretty quickly.

The other thing to consider is that once a cap is charged, the charge on it will start bleeding off. How fast it will bleed off depends on a lot of things, like the potential, the circuitry it's connected too, etc. To get the maximum effectiveness out of the caps charge, you need to be applying power to it after it's charged (not much, but some) up until you're ready to discharge it. What that means is that a ship won't typically be able to charge up their jump caps, then power everything down and sit stealthy and "off the radar" so to speak, then suddenly power back up and jump - at least not to their maximum jump potential. Ships ready to jump should be noticable by the fact their power plants are running - either to charge the caps, or keeping them charged.

Now, with a week spent in jump space, most ships should have sufficient power plant performance to recharge their caps while in j-space, meaning they only need a trickle to maintain that charge after jump. Other than the gravity well requirement you're proposed, I see no reason for the caps to prevent a ship from jumping again immediately after exiting jump space.

Of course, all of those comments are based on my years of working with capacitors in radio and power supply circuits. I'm by no means an electrical engineer, and there is a lot intricacy to electronic components that's beyond my training and experience.

I think the requirement for a gravity well to 'stabilize the jump grid' or whatever, is clearly there just for 'game balance' reasons. For me it breaks the believability a little bit. I suppose you could change the rationale behind it but keep the requirement to have to visit a gravity well for some reason or other.

That more depends on how it's worded than anything. Heat sinks and heat dumps are used in a lot of things, for me it doesn't break beleivability to require the gravity well as a form of stability dump. All that's needed is a little more thought into the wording of it.

 

[DCAnsell]

Jump Grids and Jump Bubbles are discussed in T5.

Depending on which Playtesters, owners of the T5 Material yell the loudest about the Jump technobabble will depend on if Jump Bubbles truely exist.

The main issue is if there is a Jump Grid (part of the Hull) and Jump Bubble (something different than the grid) then they must have some 'technology' or effect reasons and be different too.

(sigh)

Dave Chase

Yeah, I got the Jump Grid idea from some older MT material, though now that I look for it in the T5 playtest stuff I have, I may have been referencing that in my mind.

In the setup I'm working on, the Jump grid sustains the jump bubble, or jump field, whatever, that keeps the ship in jumps space, and lets it survive there.

The jump bubble itself would be what the jump grid does, not a technology in and of itself.

 

[DCAnsell]

Couple of comments:

Recharging the capacitors also takes significant time, generally around 168 hours for a power plant capable of powering a 1-G rated GAHET drive (GAHET= Grav-Assisted High Energy Thrust, usually called the 'gat' or just maneuver drive) in a particular sized hull. This time is divided by 4 if the GAHET drive is not in use. It's not common, but some ships have been designed with a second power plant to facilitate capacitor recharge.

I can't speak for YTU, but real world capacitors really don't take that long to charge/discharge. Even the huge room size ones used on things like VLF Transmitters. It's one of the advantages of capacitors over batteries, the disadvantage is that they often can't hold their charge stable for a long period of time.

Often times how quickly a capacitor can be charged is really dependant upon the amount of power available to charge it to full potential. A more beleivable restriction would be a charge time of 1 hour per ton of Capacitor divded by the power plant potential. So a ship with 40 tons of capictors could charge in 40 hours if it had a Power Plant rating of 1, 20 hours if it had a rating of 2, and so on. Actually, I'd go 10 minutes per ton - caps can charge pretty quickly.

That's some interesting information. I guess I'm thinking that it takes a truly ginormous (technical term) amount of energy to move a ship into jump space, and I'd really like the rules on recharging to reflect that. When I write this up more formally, I'll make very clear that the capacitors involved are greatly advanced, maybe even handwavium technology.

The other thing to consider is that once a cap is charged, the charge on it will start bleeding off. How fast it will bleed off depends on a lot of things, like the potential, the circuitry it's connected too, etc. To get the maximum effectiveness out of the caps charge, you need to be applying power to it after it's charged (not much, but some) up until you're ready to discharge it. What that means is that a ship won't typically be able to charge up their jump caps, then power everything down and sit stealthy and "off the radar" so to speak, then suddenly power back up and jump - at least not to their maximum jump potential. Ships ready to jump should be noticable by the fact their power plants are running - either to charge the caps, or keeping them charged.

Now, with a week spent in jump space, most ships should have sufficient power plant performance to recharge their caps while in j-space, meaning they only need a trickle to maintain that charge after jump. Other than the gravity well requirement you're proposed, I see no reason for the caps to prevent a ship from jumping again immediately after exiting jump space.

Of course, all of those comments are based on my years of working with capacitors in radio and power supply circuits. I'm by no means an electrical engineer, and there is a lot intricacy to electronic components that's beyond my training and experience.

I very much appreciate the comments, especially based on your experience. And given the the vast amounts of energy the caps would be holding, even on a 100 ton jump-1 ship, even relatively micro-amounts of bleed off might increase the ability to detect a fully charged ship.

I think the requirement for a gravity well to 'stabilize the jump grid' or whatever, is clearly there just for 'game balance' reasons. For me it breaks the believability a little bit. I suppose you could change the rationale behind it but keep the requirement to have to visit a gravity well for some reason or other.

That more depends on how it's worded than anything. Heat sinks and heat dumps are used in a lot of things, for me it doesn't break beleivability to require the gravity well as a form of stability dump. All that's needed is a little more thought into the wording of it.

The basic idea of needing a gravity well is based on the stutterwarp from 2300AD. The idea in the back of my mind is that the jump grid is the 'interface' between the sidereal universe, as reflected by the structure of the jumping ship, and the bizarre physics and environment of jump space, with the jump field, or bubble, being where those two very different universes interact. The destabilization effect is meant to reflect the inherent and quite violent stresses of that interaction.

 

[Rikki Tikki Traveller]

imtu, jump grids are used and hydrogen bubbles are not ( actually, I never heard of hydrogen jump bubbles in the older material I own; hydrogen is dumped as a form of 'evaporative' cooling in that its for dumping off waste heat.

the jump grid is embedded in the hull itself and thus only takes damage when the hull is penetrated. that's why MT and HG don't have jump damage for hull hits, but do for internal explosions... a hull hit doesn't penetrate the mahin hull and thus doesn't damage the embedded grid.

Other than that, I use mass instead of volume to figure jump performance ( and not in whole numbers --- 2 decimal places because I use a 3d space and those decimal places might count, ). I'm using that because gravity wells affect jump-drive and therefore the mass that forms the gravity wells affect jump-drive.

Now why didn't I think of that? The Grid is located on the INSIDE of the hull. I had always envisioned it on the OUTSIDE of the hull.

That explanation makes perfect sense.

GOODONYA!

 

[kristof65]

That's some interesting information. I guess I'm thinking that it takes a truly ginormous (technical term) amount of energy to move a ship into jump space, and I'd really like the rules on recharging to reflect that. When I write this up more formally, I'll make very clear that the capacitors involved are greatly advanced, maybe even handwavium technology.

Perhaps this will help you sort things out. Capacitors are used in a variety of ways in electronics, from filtering out noise and surges, to storing large amounts of voltage temporarily. In this case, they're going to be used to store voltage . Batteries do the same thing, and are actually better at it, but the advantage of capacitors are that they can release their voltages quickly, far faster than a battery, and far more efficiently than building a huge power power plant to deal with short term energy bursts. When you use a capacitor in this application, you're effecttively storing more power than what the power plant can deliver, often called a charge pump application.

In a charge pump application, the thing that really drives home the amount of power being delivered really isn't how long it takes the capacitor(s) to charge up, but how big they are and how many of them there are.

There are also many different ways to make capacitors, but all effectively have the same features - two conductive plates seperated by a dialectric layer. The choices of materials used can vary significantly, and substantially change the physical size of a capacitor - often times "standard" electrolytic caps will be 5-6 times the physical size of similarly rated tantalum caps. This trend has gotten more pronounced with technological advances - caps made 20-30 years ago can be 2-3 times the size of same caps made now.

To give you an idea, I've taken several tours through a 2 million watt Very Low Frequency transmitter facility - these are used to communicate with subs under water. The buildings themselves are part of the transmitter assembly. The one I've been fortunate enough to tour has probably the Traveller equivilent of 4-6 dtons of capacitors, each of them the size of two large refridgerator boxes. Those caps were designed and built using 1960's know how and processes.

Now consider even the smallest jump 1 star ship, which would have 10 tons of much higher tech caps. That still implies a lot of power - gajillions of watts/amps/volts. In the case of the standard Type S scout, which would have 20 tons of capacitors, and my recommended recharge time of 10 minutes per ton/divided by PP rating, you're looking at a 1.4 hour recharge time - which does seem short, when looked at by itself. Compare that to the 500 kton Tigress, with it's 150,000 tons of Jump capacitors and level 6 power plant - which would take 4167 hours. Wow, now that I did the calculation...

Hmm - yep, that implies a lot of power, but really breaks the system for larger ships. I'll have to consider other options for you - like possibly hull size times jump number or something. Still, the fixed recharge time to me feels wrong, and overly long. Granted, I haven't worked with anything that high power, but even in an old cathode ray TV, the caps are fully charged long before the tube warms up.

I very much appreciate the comments, especially based on your experience. And given the the vast amounts of energy the caps would be holding, even on a 100 ton jump-1 ship, even relatively micro-amounts of bleed off might increase the ability to detect a fully charged ship.

No problem. Do be aware I'm not an expert on caps, I'm just going on repair and troubleshooting experience that I have with them, as well as my schooling

The basic idea of needing a gravity well is based on the stutterwarp from 2300AD. The idea in the back of my mind is that the jump grid is the 'interface' between the sidereal universe, as reflected by the structure of the jumping ship, and the bizarre physics and environment of jump space, with the jump field, or bubble, being where those two very different universes interact. The destabilization effect is meant to reflect the inherent and quite violent stresses of that interaction.

I would simply say that time in j-space causes certain types of fields/particle build up that a gravity well disperses.

 

[lastbesthope]

IIRC there would be the following (dis)advantages to the opposing systems.

1) Hydrogen fuelled Jump stuff:

Pros:
Refuel from gas giants
Can vent dangereous explosive material quickly

Cons:
Explosive hydrogen in storage


2) Capacitor bank
Pros
Not so explosive as hydrogen
Hydrogen fuel can be gathered to power a generator/fuel cell to charge the capacitors over time.

Cons
You can't vent charge into a vacuum very easily
Lots of potential for leakage of charge in a non sentient being friendly fashion

LBH

 

[BP]

... non sentient being friendly fashion

 

[DCAnsell]

IIRC there would be the following (dis)advantages to the opposing systems.


Cons
You can't vent charge into a vacuum very easily
Lots of potential for leakage of charge in a non sentient being friendly fashion

LBH

That's an interesting thought. You couldn't just make such a tremendous amount of energy disappear...the only way to actually dump the charge in the capacitors would be to run it through the jump engines and the jump grid. Which, assuming you could do it without frying something, or actually jumping, would probably be quite a spectacular event.

 

[lastbesthope]

... non sentient being friendly fashion

Should have hyphenated that better: non sentient-being-friendly fashion

LBH

 

[lastbesthope]

IIRC there would be the following (dis)advantages to the opposing systems.


Cons
You can't vent charge into a vacuum very easily
Lots of potential for leakage of charge in a non sentient being friendly fashion

LBH

That's an interesting thought. You couldn't just make such a tremendous amount of energy disappear...the only way to actually dump the charge in the capacitors would be to run it through the jump engines and the jump grid. Which, assuming you could do it without frying something, or actually jumping, would probably be quite a spectacular event.

Well remember, energy can neither be created or destroyed, merely change form.

ALl that charge dumped into a jump grid would get used in making the jump point.

The other ways to get rid of it would be to dump it through a dummy load (Big resistor, possibly use the hull for this so long as everyone on board and any important equipment could be shielded, which would then convert it to heat which would then be dissipated, thuogh this has it's own porblems in vacuum due to lack of conduction or convection.

The other way would be to transmit the energy, i.e. channel it into a broadcast of some sort and get rid of the energy that way.

It can be done, but you have to think about 'how' it can be done.

LBH