Stealth and fusion plant exhaust

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Tea Rex
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Stealth and fusion plant exhaust

Postby Tea Rex » Tue Aug 24, 2021 8:28 pm

A question for the ship design specialists here: The fusion drive of a ship constantly converts hydrogen to helium and the exhaust gas is presumably blown directly into space. This leaves an easily detectable gas trail in space, which is stupid if the ship wants to travel undetected and without leaving any traces. Is there a standard solution to this problem?
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Re: Stealth and fusion plant exhaust

Postby Condottiere » Tue Aug 24, 2021 8:44 pm

I think the High Guard technical term is reaction drive.

I believe that some science fiction author described it as a torchlight (implying it pointed directly at your location).
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Re: Stealth and fusion plant exhaust

Postby Tea Rex » Tue Aug 24, 2021 8:52 pm

Condottiere wrote:
Tue Aug 24, 2021 8:44 pm
I think the High Guard technical term is reaction drive.

I believe that some science fiction author described it as a torchlight (implying it pointed directly at your location).
Yes sorry, my mistake. No not reaction drive. The usual manoeuvre drive is not producing any exhaust gases whatsoever.
I wanted to write fusion power plant like in the title of the thread.
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Re: Stealth and fusion plant exhaust

Postby Condottiere » Tue Aug 24, 2021 8:58 pm

There are only two basic ones presented in High Guard.

Supposedly, the manoeuvre drive exudes heat, and is powered by the onboard reactor, by default fusion.

The reactionary drive has the fuel tank emptied through it.
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Re: Stealth and fusion plant exhaust

Postby Geir » Tue Aug 24, 2021 9:33 pm

Well, you could take the helium and push it back into the fuel tank. Rockets these days use helium as a pressurization gas to keep the propellants flowing, so it wouldn't be a new thing to stick helium in with liquid hydrogen. It would even mass a tiny bit less than the hydrogen it replaced - though that doesn't mean anything with an M-drive. Then you wouldn't have to 'flush the tanks' until you refuel.
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Re: Stealth and fusion plant exhaust

Postby Condottiere » Tue Aug 24, 2021 9:42 pm

Looping it would make it perpetual motion.
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Re: Stealth and fusion plant exhaust

Postby Sigtrygg » Tue Aug 24, 2021 11:23 pm

Waste heat in Traveller ships is one of the great magical mysteries that is yet to have an official solution.

A power plant producing GW to TW of power has an enormous amount of waste heat to remove and yet it all just magically disappears..

Even if there is a magical solution there is still the issue of the ship being maintained at 300K-ish for its occupants, this produces a healthy glow easily detectable by today's IR sensors, and no you can't insulate the ship to prevent this heat signature without cooking the crew.

Magic.

There are only two ways you can remove heat from a spacecraft- radiate it to space or use a coolant that is vented to space, either would be a trivial detection issue.

Without magic there is no stealth in space...
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Re: Stealth and fusion plant exhaust

Postby Galadrion » Tue Aug 24, 2021 11:27 pm

Condottiere wrote:
Tue Aug 24, 2021 9:42 pm
Looping it would make it perpetual motion.
And? Reactionless thrusters already violate Newton's Laws... and imply at least one way to create perpetual motion. Looping the helium byproduct back into the system is actually a bit less of a problem, being somewhat akin to turbo- and super-chargers on a combustion engine (recycling waste products rather than simply venting them immediately).
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Re: Stealth and fusion plant exhaust

Postby Geir » Wed Aug 25, 2021 12:10 am

The question was just about the helium byproduct of fusion, a minor problem.
The 'physics truth' that most Traveller ships would melt or at least have hulls as hot as stars under their own waste heat even if the fusion was 99% efficient is an entirely different issue. And one that I have no answer for, except to ignore. If the drives were fusion rockets, at least I could *mumble, mumble* something about throwing all the waste heat into the exhaust (expelled from radiators that could somehow withstand temperatures in the hundreds of thousands of degrees), but they're not.

Maybe the heat goes where the gravitons for the M-drives come from... add a dimension here and there and mumble about string theory.
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Re: Stealth and fusion plant exhaust

Postby Arkathan » Wed Aug 25, 2021 1:57 am

Geir wrote:
Wed Aug 25, 2021 12:10 am
The question was just about the helium byproduct of fusion, a minor problem.
The 'physics truth' that most Traveller ships would melt or at least have hulls as hot as stars under their own waste heat even if the fusion was 99% efficient is an entirely different issue. And one that I have no answer for, except to ignore. If the drives were fusion rockets, at least I could *mumble, mumble* something about throwing all the waste heat into the exhaust (expelled from radiators that could somehow withstand temperatures in the hundreds of thousands of degrees), but they're not.

Maybe the heat goes where the gravitons for the M-drives come from... add a dimension here and there and mumble about string theory.
Actually, mumble mumble about the heat from the power plant being converted with relative efficiency directly into electricity. The US Navy was playing with that sort of thing with TL 6 gear, and no, not the dissimilar metals bending under heat to power space probes.
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Re: Stealth and fusion plant exhaust

Postby Sigtrygg » Wed Aug 25, 2021 8:52 am

Let's see:
100 GW fusion reactor, 99% efficient - that's only 1GW of waste heat to get rid of.

Next problem - the 99 GW have to go somewhere, every electrical device emits waste heat, every mechanical device produces waste heat etc

Even if we assume the 99GW gets converted into 'magical gravdrive thrust' that is removed from the ship you are still going to cook the ship.
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Re: Stealth and fusion plant exhaust

Postby Condottiere » Wed Aug 25, 2021 11:56 am

This stuff is all magic, but the rules have to be consistent.

I have no objection in improving the reactionary rockets, as the current edition's are hard to justify in using beyond trying to squeeze out better initial capital investment.
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Re: Stealth and fusion plant exhaust

Postby NOLATrav » Wed Aug 25, 2021 2:23 pm

How quickly does all the waste heat dissipate into background noise once it’s exhausted out of the nozzles?

If you play RAW many sensor packages have a -DM imposed on basic tasks. DM-4 for Civilian sensors can be hard to overcome. Stealth hulls are simply tech that can defeat a couple components of your sensor array, applying more negativity to your DMs.

IMTU I allow for Engineering to shut down certain components to use less Power and have a little table of even more DMs based on the amount of Power being used. So you can shrink your heat/fusion signature a bit and make yourself harder to identify - or look like a smaller vessel than you actually are.

All those DMs add up to not knowing if it’s friend or foe until it might be too late. So the meaningful choice isn’t “Oh crap where did they come from?! What do we do?” but rather “Is that a local patrol cutter off our bow or is it something we should be worried about?”
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Re: Stealth and fusion plant exhaust

Postby DickTurpin » Fri Aug 27, 2021 6:09 am

Helium can be fused, just like hydrogen but it yields less energy making the power plant a tiny bit less efficient. The same goes for other fusion products until you get to iron which takes more energy to fuse into heavier elements than it yields. Iron and heavier elements might just coat inside of the fusion chamber until it gets scraped out as part of that monthly maintenance cost. There is no need to vent anything into space.

Large amounts of heat get generated, so what? Heat is energy, capture it and convert it into a more useful form. How? I don't know but a society that has figured out how to propel a starship faster than light speed must have developed other technologies we do not currently have. Leftover heat after teh conversion does not matter, it can be lumped in with newly generated heat and run through the conversion process again. The efficiency of the conversion does not matter so long as it can keep up with heat production. Since it has been pointed out that star travel would be impossible without dealing with excess heat and the game features star travel as a central theme, it must have been figured out by then.

Saying that something is impossible just means we don't know how to do it. In fact we may never figure out how to do some things but the game supposes that the inhabitants of the game universe have. Requiring every technology in the game to be developed into a useable form is going to put an unbearable load on the GM and probably delay the next game for several thousand years, far longer than most players are willing to wait between sessions. Either accept the game parameters or play a game that does not require suspension of disbelief, like D&D.
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Re: Stealth and fusion plant exhaust

Postby Sigtrygg » Fri Aug 27, 2021 8:45 am

Energy can not be created or destroyed
Heat flows from hot to cold
You can never achieve absolute zero

The Imperium is run by perpetual motion
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Re: Stealth and fusion plant exhaust

Postby Condottiere » Fri Aug 27, 2021 10:18 am

You dump the heat in hyperspace.
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Re: Stealth and fusion plant exhaust

Postby Garran » Fri Aug 27, 2021 4:28 pm

Given the amount of hydrogen used to generate power, and how much that would actually represent if you were to fuse it all, it's entirely reasonable to suppose that most of that hydrogen is actually being used to create a mini jump-bubble (or series of mini jump-bubbles) that you vent all of the excess heat into and never need to worry about again.

And when you're actually <i>in</i> a jump bubble you can just vent it out there.
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Re: Stealth and fusion plant exhaust

Postby GamingGlen » Fri Aug 27, 2021 9:09 pm

Condottiere wrote:
Fri Aug 27, 2021 10:18 am
You dump the heat in hyperspace.
So contribute to the speeding up of the heat death of our universe? ;)

What if some other dimensional beings are dumping their waste heat into our dimension. Climate change?

Wait... that would make for a great conspiracy... I need to write a book, go on a lecture tour, rake in millions from the suckers. :D

Or it might make for a decent sci-fi novel: polar bears from Dimension-X are invading to stop our heating up of their universe.
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Re: Stealth and fusion plant exhaust

Postby Tea Rex » Tue Aug 31, 2021 8:20 pm

Geir wrote:
Tue Aug 24, 2021 9:33 pm
Well, you could take the helium and push it back into the fuel tank.
This is a very elegant solution. Thank you :)
Sigtrygg wrote:
Tue Aug 24, 2021 11:23 pm
Even if there is a magical solution there is still the issue of the ship being maintained at 300K-ish for its occupants, this produces a healthy glow easily detectable by today's IR sensors, and no you can't insulate the ship to prevent this heat signature without cooking the crew.
...
Without magic there is no stealth in space...
That is a problem I had not even considered. And it is a big one!
Yeah, a magical..eh .. technical solutions for dumping the excess heat into jump space could work. But this would only work when the jump drive is active? Or an entropy inverted converting heat back into some other form of energy? ;)
Ok, I stop thinking about it and forget that I started this thread. :D

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