Space and Sensor information

[TheEngineer]

Hi !

Got a vision after reading an article about MHD generators.
Well, those would offer to work without contact between heat carrier and actual material surfaces.
Thus possible temperature ranges could be fairly high, so that reasonable efficiencies could be achieved (in the future).
Here the ultra-high temp radiators could be used.
E.g. a scoutship with 850 MW PP output and an optimistic efficiency of 0,85 could radiate away around 150 MW waste heat on 20 m² at comfortable 3500 K radiator temperature.
But as one might see, this really is at the edge of pure handwaving.

TE

 

[aramis]

If we assume that the bottle precludes actual heat transfer (IR isn't heat; heat is, technically, the excitation of molecules. IR can cause heat...) and high efficiency broad em-spectrum cells to convert vast portions of the energy radiation to electricity (say 95%), dumping the helium out the back should carry most of the heat generated in the plant out.

for reference (from Wikipedia):
Surface temperature 5785 K
Temperature of corona 5 MK
Core temperature ~13.6 MK

So, we can assume at least 6000K working fluid in the fusion core. Probably at least 10 KK

 

[Anthony]

Originally posted by Aramis:
If we assume that the bottle precludes actual heat transfer (IR isn't heat; heat is, technically, the excitation of molecules. IR can cause heat...) and high efficiency broad em-spectrum cells to convert vast portions of the energy radiation to electricity (say 95%), dumping the helium out the back should carry most of the heat generated in the plant out.

The amount of helium produced is absurdly small, though it might be dumping hydrogen, there's no other explanation for the fuel consumption of Traveller fusion reactors. However, in any case dumping waste product out the back will produce a discernable heat (and visible) signature.

 

[TheEngineer]

Hi !

Well, the example scout has a fuel consumption around 0,1 l/s or 8 g/s LH.
This might be a high consumption regarding the fusion, but perhaps still is not enough to get rid of 150 MJ per second ??

TE

 

[Anthony]

Originally posted by TheEngineer:
Hi !

Well, the example scout has a fuel consumption around 0,1 l/s or 8 g/s LH.
This might be a high consumption regarding the fusion, but perhaps still is not enough to get rid of 150 MJ per second ??

Hm. Using CT fuel use (PP-1 burns 1T/28 days) I get a fuel use of 413g/s. 250MW is 2.78 micrograms of energy per second, or about 400 micrograms of hydrogen fused per second if you give it 100% efficiency. 625 MJ/kg, for hydrogen, works out to a temperature of ~50,000 degrees; if we assume 80% efficiency the remaining temperature is less than 10,000K, which is about right to produce a mysterious blue-white glow

 

[TheEngineer]

Hi, maybe I'm wrong, but perhaps lost a factor 0,001

?
1T/28 days > 1000 kg / (28*24*3600) > 0,000413 kg/s

Just wondered why MT fuel usage suddenly is lower than CTs....

Anyway its still good for the glow

 

[Plankowner]

I think the sun only fuses Hydrogen at about 0.01% efficiency. So assuming 100% efficiency in a Fusion Power Plant might be very optimistic. The excess fuel usage would be the inefficiency of the PP and could be used to carry off waste heat as well...

Of course dumping hydrogen gas at 10K degrees or so, will create it own heat signature...

 

[Anthony]

Originally posted by TheEngineer:
Hi, maybe I'm wrong, but perhaps lost a factor 0,001

Hm. Duh. Yes, you're right. And yes, MT dropped fuel usage, though it's still quite high relative to the energy content of the fuel.

The sun has an efficiency of 0% -- 0% goes into work, 100% goes into heat.

 

[aramis]

Anthony: Only if one looks at it without including Earth in the reference frame... at which point a very tiny fraction is work...

Rest:
Detecting a large volumes of high temp gases is not going to remain terribly easy over time; they will cool on their very quickly near-infitine surface area and near-0 density...

Again, it's a flare, but at least it doesn't melt the Ship!

Oh, and IMTU, anything leaving the bubble dissociates at the molecular level and precipitates out...

 

[Icosahedron]

Just another thought on this. In CT, the fuel is only used during a movement burn, this indicates to me that at other times the reactor is idling at a very low energy output and therefore would not build up a lot of heat. The only time it gets really fired up is when the ship moves, and then the energy produced is converted (at X percent efficiency) to motion. The excess heat (100-X)must then be dumped somehow, so maybe in a way all ships are torch ships?
Anyone care to figure out if the fuel consumption figures can be made to tally by flinging relativistic Hydrogen out the back as a heat sink?

 

[Anthony]

As a heat sink? Unclear but irrelevant, since the hydrogen being dumped will be just as visible as radiators (it will, however, shift the emissions peak into the X-ray range. This will not make ships harder to spot).

As for M-drive efficiency, M-drives blatantly break conservation of energy (and momentum).

 

[aramis]

Icosahedron:

Where in CT do they burn fuel only when maneuvering? That realism isn't introduced in core rules (to my knowledge) until TNE, and the prior existences are in MT's Hard Times and CT's Beltstrike, neither of which are core. CT has NO maneuver fuel at all in Bk2 nor HG; only powerplant fuel.

 

[Liam Devlin]

Okay, I've got a question, involving manuevering, IR sensors, atmospheres, etc:

Scout Ship A (Standard 100dt, J2/2G), powered down, and lying 'doggo' for nearly a week in a Small Gas giant's outermost ring (orbit 3), detected initially on her passives a hostile number of vessels at extreme long range (180,000Km's+), inbound to their location at 1 & 2G's (ostensibly to refuel wilderness style, amassing 600 and 400dtons.

Scout ship A has a deadline to get word back to higher echelon HQ number of and class(es) of vessel hostiles, had has been here already 7 days of a four week patrol. SCout Ship A's Commander decides to risk Active sensors as current distance and speed indicate target hostiles ETA to SGG outer ring at 6 hours & 3 hours respectively, and smaller vessel is on 'point'.

The risk is deemed acceptable as movement at 2G for Scout A to Jump diameter can be made away from hostiles if Active sensors detected in 1.5 hrs from position in ring at orbit 3 from SGG.

Scout A uses Active sensors briefly on both hostile vessels, determining closer/ faster vessel is P-class Corsair, and slower is an upgunned M-class Liner in raider configuration.

Problem begins with Corsair detecting the scan, and increasing Speed to 3G; Scout Ship A, now facing faster better armed foe decides cannot make it to Jump point safely, and flies out of the ring for the SGG's atmosphere, where it hopes to elude the P-class Corsair's sensors.

Due to 'headstart' distance, Scout A can just get within atmosphere of the SGG before Corsair can get within effective Laser fire distance.

My question involves this:

Can the Scout ship fly through the atmosphere at full burn, then dump built-up heat, and last cut her drives to sling shot (coasting) out over the horizon of the SGG (out of "LOS" of sensors) with any decent chance of not getting picked up by the P-class in hot pursuit?

Would a differing angle of exit from route on entry help this manuever?

Exiting the SGG's surface, does this give the hunted an advantage or disadvantage? Will the SGG's sensor image/ IR image blindout the Scout's smaller signature?

Any suggestions to the above scenario for the pursued? For the pursuer?

The end objective to this is, using the slingshot method manuver, but no longer burning thrust/ and drives 'cold' can they escape to Jump diameter coasting there?

 

[Icosahedron]

Originally posted by Aramis:
Icosahedron:

Where in CT do they burn fuel only when maneuvering? That realism isn't introduced in core rules (to my knowledge) until TNE, and the prior existences are in MT's Hard Times and CT's Beltstrike, neither of which are core. CT has NO maneuver fuel at all in Bk2 nor HG; only powerplant fuel.

Oops, I got my rules mixed up. That's what comes of borrowing house rules from numerous sources.

However, it still stands to reason that IF the reactors can idle, it solves most of the heat build up problems.

Anthony, I wasn't suggesting the Hydrogen was dumped to hide the heat, just to get rid of it, and I was wondering if the fuel consumption figures (being too high for fusion alone, according to you and The Engineer) were meant to (or could be made to) explain a torch ship with relativistic exhaust?

 

[TheEngineer]

Hi !

Liam, so many variables, prediction overflow

Generally I would agree, that the Scout has to get away ASAP, otherwise the SGG is perhaps just a trap for a slower ship.
The slingshot maneuver could be a good trick to create an surprising departure angle from the SGG. You should not have contact with any siginifant part of the atmo, because it would heat up and slow down the vessel.
Most of the rest is up to the quality of sensors and the exact geometry of the setting IYTU

Could You draw a rough sketch of the situation ?

regards,

TE