Timeline for Stealth in Space: How realistic is it?
Current License: CC BY-SA 3.0
10 events
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| Dec 4, 2016 at 20:58 | comment | added | Physicist137 | Let us continue this discussion in chat. | |
| Dec 4, 2016 at 20:56 | comment | added | Daerdemandt | If you surround your emitter with mirrors, leaving only small exhaust then it will be surrounded with images of emitters of the same temperature. Your emitter is in equilibrium with those emitters and no exchange happens (well, more precisely in = out - with ideal mirrors). Emission only happens to the part of the sky your emitter sees, so if you don't use curved mirrors your efficiency won't exceed what your emission cone makes of a full sphere. Also, remember this. | |
| Dec 4, 2016 at 20:40 | comment | added | Physicist137 | @Daerdemandt Oh. Well. I was thinking in something more like this: (1) Heat of ship interior is pumped to some place, which is used to heat up some object. (2) Temperature of that object will rise (maybe ~2500K) and will emit black body radiation (in all directions). (3) Then, mirrors will concentrate the radiation in single spot, and another mirror will make it a unidirectional beam, and plane mirrors will direct beam away from ship. Of course, from each step 1-->2-->3 there will be loss of efficiency. I haven't made the calculations (specially the efficiencies). But intuitively, might work. | |
| Dec 4, 2016 at 20:11 | comment | added | Daerdemandt | 60-degree-cone radiator is 10% efficient. With tighter cones, it gets ridiculously inefficient pretty fast (cone angle twice smaller - 4 times less efficient). Something that's effectively a beam would be effectively not working at all. And, of course, you will have to run one more heat pump to run this thing. | |
| Dec 4, 2016 at 19:54 | comment | added | Physicist137 | @Daerdemandt I said "unidirectional beam" in (7.3) which by definition has your "cone angle" of 0 degree, and yes, its a line. Of course, you won't have exactly 0, but very near. And this ensures enemy only will know a line-location (if there happen to be a platform in front of your beam (you won't aim in a plataform!!)). Its like a laser. | |
| Dec 4, 2016 at 19:50 | comment | added | Daerdemandt | It's not the area that matters, but a cone. If extremely-hot 1mm^2 spot radiates to half of the outer universe (180-degrees cone), you are going to be detected by sensors in that half. You can aim for 60-degrees cone as reasonably narrow, but even then spamming space with detecting drones could be cheap enough to make that pointless. As for enemy having only a line of where you are - no, with platforms enemy can know the location too. Even if the enemy knews trajectory of his own platform and observes your ship for some time, there's much more info than just a direction. | |
| Dec 4, 2016 at 19:46 | comment | added | Physicist137 | @Daerdemandt Yes. Something like that. Perhaps (also) insulating hull from inside. Time constants of heat diffusion in insulators can be made in days range. Perhaps even months in special cases. As for emission of heat and sensor platforms, space is vaaast. Very vaast. All you need to do is release your heat with extreme power density (compress full beam in, say, $1mm^2$ of area). Furthermore, with platforms, enemy cannot have your position, rather, only a oriented line of where you are. | |
| Dec 4, 2016 at 19:28 | comment | added | Daerdemandt | As for controlled emission of heat, it can be done if you have a safe direction to emit to, and that depends on what economic tradeoffs are. If sensor platforms are cheap then they're abundant and you don't have safe directions if you're close to anything of interest. Otherwise, you might have a chance. Take a look at link in the beginning of the accepted answer, there are some options. | |
| Dec 4, 2016 at 19:08 | comment | added | Daerdemandt | > If you have hypothetical material that nicely does (7.2), then it will not heat up It will be heated up from the inside to the temperature you maintain inside (~290K) unless you continiously burn energy to maintain temperature gradient. Well, if you have layered outer hull with layers separated by vacuum and refrigerated it can be tolerable, but you would be pretty limited in outwards-looking sensors. | |
| Dec 3, 2016 at 17:19 | history | answered | Physicist137 | CC BY-SA 3.0 |