Nordviking
SOC-9
As I do Not have FF&S can someone shed some light on the Fuel consumption of the HePLar Drive
HePLaR Drives
- Thread starter Nordviking
- Start date
Heplar uses 0.25 kiloliters of fuel per hour per megawatt of power required.
Each megawatt of power generates 20 tons of thrust, and requires 0.1 kiloliters of volume and 0.1 tons of mass. It costs 1000 credits per megawatt of power.
Now an example, taking the humbly Type S with a 2G drive.
Rules state that thrust equal to 10x displacement is required per G of acceleration (upto a loaded mass of 15xdisplacement at which time it becomes a mass/thrust relationship)
So the 100dt Scout with 2G requires 10x100x2
ie 2000 tons of thrust
To get this a Heplar Thruster will need 2000/20 Megawatts ie 100 Megawatts
Volume of the Heplar will then be 0.1 x 100
ie 10 kiloliters and mass will be 10 tons.
Fuel consumption will be 0.25 x 100 = 25 kiloliters per hour (this will be at 2G so a G hour of fuel will be half this ie 12.5 kiloliters of fuel)
A G Turn would be half this figure again ie 6.25 kiloliters.
Each megawatt of power generates 20 tons of thrust, and requires 0.1 kiloliters of volume and 0.1 tons of mass. It costs 1000 credits per megawatt of power.
Now an example, taking the humbly Type S with a 2G drive.
Rules state that thrust equal to 10x displacement is required per G of acceleration (upto a loaded mass of 15xdisplacement at which time it becomes a mass/thrust relationship)
So the 100dt Scout with 2G requires 10x100x2
ie 2000 tons of thrust
To get this a Heplar Thruster will need 2000/20 Megawatts ie 100 Megawatts
Volume of the Heplar will then be 0.1 x 100
ie 10 kiloliters and mass will be 10 tons.
Fuel consumption will be 0.25 x 100 = 25 kiloliters per hour (this will be at 2G so a G hour of fuel will be half this ie 12.5 kiloliters of fuel)
A G Turn would be half this figure again ie 6.25 kiloliters.
M
Malenfant
Guest
And given the Type S has 500 kl of fuel for its HEPlar drive (is it me, or does it not actually say that explicitly in the stats in the TNE book?) that means it can sustain 2G acceleration for 20 hours.
Doesn't sound like a lot...
Doesn't sound like a lot...
mike wightman
SOC-14 10K
It isn't 
This was one of the tech paradigm shifts which has a major impact on the mechanics of the TNE-OTU.
Ships can no longer make interplanetary journeys as easily as they did/can in CT/MT/GT/T4/T20.
It does, however, make insystem jumps much more useful for getting around a system. Which is what we Terrans invented them for
This was one of the tech paradigm shifts which has a major impact on the mechanics of the TNE-OTU.
Ships can no longer make interplanetary journeys as easily as they did/can in CT/MT/GT/T4/T20.
It does, however, make insystem jumps much more useful for getting around a system. Which is what we Terrans invented them for
TJP
SOC-12
Even though I kinda liked HEPlaR (as I've never been a big fan of reactionless drives), I wondered why they changed to it. It really isn't any more realistic than reactionless thrusters (ie. thruster plates) as the exhaust velocity of it is stupendous, to say the least. It completely changes the nature of N-space travel(*) and requires more starship bookkeeping as re-mass needs to be counted. Et cetera. The only thing it seems to remedy is near-c rocks/starship planetkillers.
(*) IMO, any (realistic or semi-realistic) reaction drive isn't going to work well in space opera as it'll quite thoroughly preclude small free traders zipping around in space, which are a staple of space opera.
(*) IMO, any (realistic or semi-realistic) reaction drive isn't going to work well in space opera as it'll quite thoroughly preclude small free traders zipping around in space, which are a staple of space opera.
Commander Drax
SOC-12
Hi Guys,
Heplar as written in the original fire fusion and steel is a realistic and scientifically sound drive system except for one thing, that it is extraordinarily fuel efficient. This is a deliberate fudge on the part of GDW as more real life fuel consumption would reduce the usefulness and effectiveness of traveller starships by an inordinate magnatude. The fuel aboard aboard a typical free trader would probably last 4 to 5 hours (at max) instead of the usual 30.
Despite this I like Heplar and can think of loads of ways to explain this incredible efficiency in any game. I like it becuase in system journeys with it take ages, and makes gas-giant refuelling for merchants almost pointless, thus keeping merchant shipping close to the source world and destination.
Also militarily invading a star system and capturing the gas-giant is just as pointless, as the bulk of your fuel skimmed from such a place would more than likely be used travelling from the gas giant to the mainworld in a typical system (imagine using heplar to travel from jupiter to earth). So in this case it's much better to jump directly to the mainworld for a surprise and overwhelming attack, that hopefully will capture any fuel sources there (like the airspace needed to allow safe ocean refuelling).
Lastly its a great benefit for smugglers as their vessel would only have a high signature when thrusting, and when coasting would effectively be running silent.
As a last word I've designed some rules to integrate Heplar with T20.
These will be freely available, along with a technological overview on the soon to be re-launched Pocket Empires website.
If all goes well the site will be re-launced on November 1st.
(If all goes well that is."
Heplar as written in the original fire fusion and steel is a realistic and scientifically sound drive system except for one thing, that it is extraordinarily fuel efficient. This is a deliberate fudge on the part of GDW as more real life fuel consumption would reduce the usefulness and effectiveness of traveller starships by an inordinate magnatude. The fuel aboard aboard a typical free trader would probably last 4 to 5 hours (at max) instead of the usual 30.
Despite this I like Heplar and can think of loads of ways to explain this incredible efficiency in any game. I like it becuase in system journeys with it take ages, and makes gas-giant refuelling for merchants almost pointless, thus keeping merchant shipping close to the source world and destination.
Also militarily invading a star system and capturing the gas-giant is just as pointless, as the bulk of your fuel skimmed from such a place would more than likely be used travelling from the gas giant to the mainworld in a typical system (imagine using heplar to travel from jupiter to earth). So in this case it's much better to jump directly to the mainworld for a surprise and overwhelming attack, that hopefully will capture any fuel sources there (like the airspace needed to allow safe ocean refuelling).
Lastly its a great benefit for smugglers as their vessel would only have a high signature when thrusting, and when coasting would effectively be running silent.
As a last word I've designed some rules to integrate Heplar with T20.
These will be freely available, along with a technological overview on the soon to be re-launched Pocket Empires website.
If all goes well the site will be re-launced on November 1st.
(If all goes well that is."
M
Malenfant
Guest
Isn't HEPLar supposed to have an unfeasibly high impulse for what it is?
And also, the reaction mass is a bit odd. From what I understand, isn't it better to lob out a stream of HEAVY ions out of the back of the craft? Current/recent spacecraft (I think NEAR was an example) are using Xenon as a reaction mass, which is about 130 times more massive than hydrogen and therefore can impart more momentum to the spacecraft.
And also, the reaction mass is a bit odd. From what I understand, isn't it better to lob out a stream of HEAVY ions out of the back of the craft? Current/recent spacecraft (I think NEAR was an example) are using Xenon as a reaction mass, which is about 130 times more massive than hydrogen and therefore can impart more momentum to the spacecraft.
Commander Drax
SOC-12
All of these things are true, but hydrogen was considered to be the best fuel source for a variety of 'all round reasons', in that jump tankage is also hydrogen, and hydrogen being the most abundant element in the known universe is readily extractable from gas-giants and water oceans/ice etc. Also fusion plants require hydrogen so whilst I agree that there are better candidates for reaction mass, hydrogen is much simpler from a logistical point of view.
Current technological assumptions regarding Ion drives only give them a low thrust to mass ratio, which whilst ideal for long in system trips wouldnt be practical for a short hop from the surface to jump point.
Its interesting though, after all I'm not going to be foolish enough to say that Ion drives won't be improved with more development and research and the like.
Perhaps traveller ships should have short duration plasma burning rockets for quick hops out of atmosphere to orbit and jump distance coupled with an extremely efficient Ion drive for long in system trips. There again any trip likely to take longer than a week would probably be ruled out if the ship was jump capable and could execute a micro-jump.
Hmmm...
Current technological assumptions regarding Ion drives only give them a low thrust to mass ratio, which whilst ideal for long in system trips wouldnt be practical for a short hop from the surface to jump point.
Its interesting though, after all I'm not going to be foolish enough to say that Ion drives won't be improved with more development and research and the like.
Perhaps traveller ships should have short duration plasma burning rockets for quick hops out of atmosphere to orbit and jump distance coupled with an extremely efficient Ion drive for long in system trips. There again any trip likely to take longer than a week would probably be ruled out if the ship was jump capable and could execute a micro-jump.
Hmmm...
Checking TNE Mk1 Mod 1 The type S scout is listed as carrying 80 G Turns of fuel (40 G Hours) Checking my earlier figures 80x6.25=500
So the 80G turns means the type S could accelerate at 1G for 80 turns (40 hours) or at 2G for 40 turns (20 hours) So yes this is limited, but there are even worse fuelled ships out there like the very popular Jayhawk class far trader which has 48 G Turns (24 hours) of maneuver fuel.
Note though that if a ship is not using its full jump fuel, ie the type S doing a jump-1 rather than jump-2 the fuel remaining (105 kiloliters in this case) can also be used for maneuver.
105 kiloliters gives an additional 16.8 G Turns.
In a system most ships only need fuel to get in and out of that 100D limit. It is with warships that the real fun begins. Try that famous vessel class the Azhanti High Lightning. If it does a jump-5 it better hope there is a secure fuel source at its destination becuase it will arrive with of 34 G turns of fuel, less any used maneuvering to that 100D limit.
A warship commanders life is not a happy one.
So the 80G turns means the type S could accelerate at 1G for 80 turns (40 hours) or at 2G for 40 turns (20 hours) So yes this is limited, but there are even worse fuelled ships out there like the very popular Jayhawk class far trader which has 48 G Turns (24 hours) of maneuver fuel.
Note though that if a ship is not using its full jump fuel, ie the type S doing a jump-1 rather than jump-2 the fuel remaining (105 kiloliters in this case) can also be used for maneuver.
105 kiloliters gives an additional 16.8 G Turns.
In a system most ships only need fuel to get in and out of that 100D limit. It is with warships that the real fun begins. Try that famous vessel class the Azhanti High Lightning. If it does a jump-5 it better hope there is a secure fuel source at its destination becuase it will arrive with of 34 G turns of fuel, less any used maneuvering to that 100D limit.
A warship commanders life is not a happy one.
mike wightman
SOC-14 10K
All the more reason to jump with a vector relative to your destination, you can then use your fuel for any course adjusments.
Come to think of it, if you are dead in space relative to your target when you emerge from jump you can just let gravity do its job.
Getting your Astrogation wrong could be a but of a downer...
Come to think of it, if you are dead in space relative to your target when you emerge from jump you can just let gravity do its job.
Getting your Astrogation wrong could be a but of a downer...
Commander Drax
SOC-12
Well if you're a merchant you shouldn't really need anything more than 4G hours of fuel, (leave the surface, break orbit, jump, arrive in system, travel to orbit and then surface again) with a few m3 left over for course corrections and emergencies.
Mercantile ships should therefore have very small fuel tanks, allowing them to dedicate more volume to cargo and passengers.
I like this approach when it comes to merchant ships: configurability. Got spare staterooms? Stick cargo in them. Design the ship to have small permanent tanks for normal use, and when you think you need more, break out the collapsible fuel bladders. Very handy when you're low on cargo and want an extra margin of safety.
Of course, it makes your ship's datasheet all big and ugly and full of caveats.
Of course, it makes your ship's datasheet all big and ugly and full of caveats.
Hmm, I always liked HEPlaR better than reactionless thrusters (which were really only a product of MT. Original Traveller was vague and at IIRC in High Guard the drives were explicitly implied to be fusion drives with the ability to make attacks, etc).
As far as braking cannon... has anyone done an analysis of TNE HEPlaR reaction mass consumption versus that of MT with reactionless drive + fuel hungry power plants?
As far as braking cannon... has anyone done an analysis of TNE HEPlaR reaction mass consumption versus that of MT with reactionless drive + fuel hungry power plants?
Just some quick "back of envelope" figures here; I don't have my books with me and I'm quoting these from memory. Back when FF&S came out, I tried to calculate the specific impulse of the heplar drive, and kept coming up with about 4E6 seconds. According to The Starflight Handbook, fusion drives ought to max out around (I think) 2.6E6 seconds, again, assuming I didn't miss a step somewhere. So heplar appears to be about half again as efficient as any fusion drive ought to be.
So what gives? FF&S describes heplar as "damper-mediated fusion", so I'd assume that nuclear dampers are employed to increase the energy output of the fusion reactions. This raises two more questions in my mind; 1) Nuclear dampers are supposed to suppress the strong nuclear force. Wouldn't this inhibit fusion, rather than encourage it? and 2) Heplar is TL10--isn't that quite a bit earlier than any other mention of nuclear dampers? I thought they were introduced around TL12.
I like the idea of reaction drives in Traveller, but heplar seems to have some inconsistencies.
XO
So what gives? FF&S describes heplar as "damper-mediated fusion", so I'd assume that nuclear dampers are employed to increase the energy output of the fusion reactions. This raises two more questions in my mind; 1) Nuclear dampers are supposed to suppress the strong nuclear force. Wouldn't this inhibit fusion, rather than encourage it? and 2) Heplar is TL10--isn't that quite a bit earlier than any other mention of nuclear dampers? I thought they were introduced around TL12.
I like the idea of reaction drives in Traveller, but heplar seems to have some inconsistencies.
XO
mike wightman
SOC-14 10K
Nuclear dampers can be used to enhance (nodes) or suppress (antinodes) the strong nuclear force.
And you are quite correct, introductory TL is 12.
And you are quite correct, introductory TL is 12.
Well, there's one mystery solved--a nuclear "enhancer" could be used to accelerate fusion reactions. Regarding the TL12 nuclear dampers--that's the TL at which they're first used as defensive screens. However, is it possible that heplar uses an earlier, much shorter-ranged version of the same technology? What I'm thinking is that a very small, localized nuclear damper could possibly be made at TL10, then by TL12 its range would be improved enough to defend the ship it's mounted on.
XO
mike wightman
SOC-14 10K
Sounds reasonable, it could be the result of research into the manipulation of the strong nuclear force for fusion power plant improvement, and that early versions are set up to enhance only.
