SomeGuy12 Posted October 2, 2015 Author Share Posted October 2, 2015 What if instead of trying to go stealth by cooling things down you do it the other way around by deploying a swarm of thermal decoys that blind the enemy's sensors?This is about the same as Rune's laser idea. You overcome it a similar way. You use filtered sensors that have extremely narrow fields of view, and they scan across the sky very rapidly, and you correlate the inputs from several such sensors to search the sky in 3 dimensions. You probably do this digitally with massive sensor arrays that are sensitive to the phase of incoming light. You can then digitally focus on different areas of the input and thus filter out the bright decoys. You reduce gain and use high dynamic range sensors so you don't get blinded. Link to comment Share on other sites More sharing options...
andrewas Posted October 2, 2015 Share Posted October 2, 2015 You're also advertising that you have something to hide, so everything you have will be under greater scrutiny. And given the travel times for any spacecraft that doesn't have a drive exhaust you could see from alpha centauri, there will be plenty of time for the enemy to locate the craft who's departure your decoys masked. The only time stealth in space is viable is when the enemy has no idea that there are hostile spacecraft to look for. Link to comment Share on other sites More sharing options...
KerikBalm Posted October 2, 2015 Share Posted October 2, 2015 By the way, as to the idea of cold, high pressure gas...When you cool a gas and compress it, it ceases to be a gas... it liquifies and/or freezes.hydrogen and helium would be the best candidates... but even they liquify at temperatures above CBR at 1 atmosphere.You can even freeze helium at pressures above 29 atmospheres.You simply can't get any reasonable Isp from expelling cold gas.Increase the pressure, and you increase the temperature you need to keep it a gas.A high pressure cold(just above the boiling point) hydrogen gas thruster would have horrible Isp.Understanding the rocket equation should mean understanding why this isn't viable.When you dV is so low... it might as well be a weapons platform, and then you might as well remove the propulsion system altogether. Link to comment Share on other sites More sharing options...
SomeGuy12 Posted October 2, 2015 Author Share Posted October 2, 2015 (edited) Yeah. This is why I wanted Wedge to actually do the math. It's one thing to say "it's gonna be low". It's another thing to actually find out the mean velocity for, say, hydrogen gas at 4 Kelvin and calculate the ISP for it. There is a point at which ISP is so low you don't really have a maneuvering engine, just a way to waste expensive propellant and be on basically the same course you were before.v = √(3RT/M). T is 4. R is 8.314. M is 1. ISP is about 1. Yeah, you aren't going anywhere. Edited October 2, 2015 by SomeGuy12 Link to comment Share on other sites More sharing options...
GeneralVeers Posted October 4, 2015 Share Posted October 4, 2015 I think this is a good quote: "the brightest minds in the world have been wrong many"They have been wrong, and you most certainly are in this case.Prove that I'm wrong. The only way to do that is with a test. Very few things in this thread can be proved either right or wrong. The whole thread is definite maybe's.Even though we can't test X, from what we know now, stealth in space is not possible.And that's exactly the kind of thinking I was referring to when I said "the world's brightest minds have been wrong many, many times". Literally millions of scientists in the past have said the same thing you just said here. Based on things that they "knew". Many of them turned out to be wrong.You simply call yourself right and the otherside ignorant.As the old saying goes: call a spade a spade.What if instead of trying to go stealth by cooling things down you do it the other way around by deploying a swarm of thermal decoys that blind the enemy's sensors?We'll definitely see that tactic used. A lot. (well, maybe not to BLIND enemy sensors, but certainly to keep the Other Side guessing as to which blips are real ships.....) Problem is, that's a definite, so there's nothing to argue about, so most other people in here find the topic boring.By the way, as to the idea of cold, high pressure gas...When you cool a gas and compress it, it ceases to be a gas... it liquifies and/or freezes.Which is an easy problem to avoid by keeping it above the critical temperature. Take helium, for example: apparently it's IMPOSSIBLE to liquify helium at any temperature above four degrees Kelvin, no matter the pressure.v = √(3RT/M). T is 4. R is 8.314. M is 1. ISP is about 1. Yeah, you aren't going anywhere.Simple observation of real-world gases ("real gas"? har har) proves your formula is missing a variable. V is directly related to the pressure inside the storage vessel. When you open the valve and the gas starts hissing out, the velocity slows down as the tank empties. When the storage pressure drops to one atmosphere? (or zero atmospheres if you're in space?) V = zero.#FormulaHazProblem(ten minutes after I wrote the above) I think I found the problem: you used the wrong formula. The above is the "root-mean-square" formula for finding the average velocity of an individual gas molecule in a static system (i.e. a tank with the valve CLOSED). The total velocity of all the molecules in a closed tank is obviously zero, but the molecules are still moving around. That's what the above formula is for. Link to comment Share on other sites More sharing options...
KerikBalm Posted October 4, 2015 Share Posted October 4, 2015 (edited) Prove that I'm wrong.Prove that you are right... you are doing more than taking the point of view that both sides are unproven, you are asserting that it definitely is possible.Literally millions of scientists in the past have said the same thing you just said here. Based on things that they "knew". Many of them turned out to be wrong.Many out of millions were wrong (I think several qualifies as many, no?)...Therefore you are right....That has got to be one of the biggest logical fallacies ever.As the old saying goes: call a spade a spade.Well then... if that's not a personall attack, then I don't know what is... you just called most of us on this thread ignorant.I'll call a spade a spade...You are conceited, arrogant, ignorant, unintelligent, and wrong.Now, lets close the thread shall we?Take helium, for example: apparently it's IMPOSSIBLE to liquify helium at any temperature above four degrees Kelvin, no matter the pressure.Citation, or just more baseless assertions that you regard as right until someone else proves you wrong?ok, here you go...You get to at least 5 K before the liquid/gas distinction breaks down and it becomes a supercritical fluid, at which point its not really behaving like a gas either - which is the important part.Then your Isp is basically the velocity of the liquid you're squirting out of your nozzle, and its F=MA, and you need to look at the pressure per unit area, and density of the liquid.Hint: Isp is still terrible. Edited October 4, 2015 by KerikBalm Link to comment Share on other sites More sharing options...
Vanamonde Posted October 4, 2015 Share Posted October 4, 2015 The discussion in this thread has turned personal. It's time to set it aside and move on to other subjects. Please keep in mind that people who disagree with you are not your enemies. Link to comment Share on other sites More sharing options...
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