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PaperclipPerfector  10mo ago (text post)   2195 thread views

Friday Fun Thread for January 5, 2024

Be advised: this thread is not for serious in-depth discussion of weighty topics (we have a link for that), this thread is not for anything Culture War related. This thread is for Fun. You got jokes? Share 'em. You got silly questions? Ask 'em.

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Maybe in principle it's possible, but in this setting they're using multi-thousand tonne ships with nuclear fusion powerplants that get up to 1% lightspeed (imagine the exhaust), in a region that really ought to be heavily watched since it's a militarized treasure trove, in the rather highly populated Sol system. They use some tricks such as covering one's burn but really...

As of 2013, the Voyager 1 space probe is about 18 billion kilometers away from Terra and its radio signal is a pathetic 20 watts (or about as dim as the light bulb in your refrigerator). But as faint as it is, the Green Bank telescope can pick it out from the background noise in one second flat.

Also, how can you use a laser as a radiator? Isn't the rule that they always make more heat than they release in energy?

IMO stealth in space needs FTL to make sense. When you're moving faster than light, you can be stealthy since they can't see you coming. You could have picket ships, scouts, messenger drones, all moving superluminally.

Ah, yeah that sounds like something not particularly stealthy, unless there is some very fancy nozzle tech going on.

The Voyager example is cited alot as some sort of definitive proof, but misses the obvious point that emissions controls (EMCON) on radio frequency emissions have been a means of avoiding detection since shortly after the first RDF equipment was invented, and the navies and air forces of the world have practiced its use for nearly a century at this point. A 20 watt RF emission is infinitely stonger than a non-existent one after all. The great thing about a vaccum is there are no pesky particles to scatter lasers, which means laser LOS communication is quite easy, and i would imagine become the default for military operations.

RE lasers as radiators- the basic recipe for a laser is to convert an incoherent form of radiation to a coherent form, with some transformation losses of energy. These tranaformation losses are usually waste heat, but if you are beaming a massive amount of IR radiation away, your thermal energy delta is negative. Gas dynamic lasers are a good example- they can arc weld quarter inch steel plate at a hundred miles in a fraction of a second, and the lasing mechanism itself becomes only slightly warm to the touch. There is definitely no free lunch in terms of energy generation, but since the problem you are trying to solve is an energy surplus rather than a defecit, thats not a particularly big deal. The simplest setup would involve a a solid state IR laser enveloped by a cooling mechanism which is in turn coupled to some form of thermionic converter that is the actual power source for the laser. This makes for what is effectively a laser refrigerator of not particularly great efficiency, but still capable of cooling a spacecraft while emitting only coherent radiation.

There is not a whole lot of literature on the subject, mostly because lasers dont make very efficient radiators and the only immediately plausible applications are all military in nature, but there is no thermodynamic prohibition on it. See: https://ntrs.nasa.gov/citations/19660023147 for the genral efficiency calculations.

The FTL interaction with stealth is definitely an interesting one, I find the way its portrayed in the Honor Harrington series to be good, essentially concluding that in a universe with relatavistic ships and weaponry anything moving in classical mechanic terms is stealthy because the light cone of detection is slow relative to the application of deadly force.

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