insert_name Posted January 6, 2016 Share Posted January 6, 2016 Which has a higher isp for ion engines, xenon or argon, I thought argon would because its lighter. Quote Link to comment Share on other sites More sharing options...
peadar1987 Posted January 6, 2016 Share Posted January 6, 2016 I believe Argon gives the higher Isp, but Xenon is easier to ionise, so using it will reduce the power requirements Quote Link to comment Share on other sites More sharing options...
Elukka Posted January 7, 2016 Share Posted January 7, 2016 On 1/6/2016 at 0:28 PM, RainDreamer said: This thread should be pinned. So hard to find it. Anyway, my question right now is: is there any significant increase in explosive yield when you launch a nuke with faster speed (by, say, a rail gun)? One of the game I was playing has a space ship launching nukes using railgun to accelerate it to hyper velocity, and I wonder if it makes the nuke any more explody. There'd be no difference. The nuke has to detonate before it hits the target (otherwise it won't detonate at all) and it doesn't care how fast it's going relative to it. Quote Link to comment Share on other sites More sharing options...
shynung Posted January 12, 2016 Share Posted January 12, 2016 (edited) If one were to bolt SABRE's precooler (from the engine that powers the Skylon SSTO concept) onto the intake of a typical turbojet engine, how much improvement can be expected from the engine, assuming constant exhaust temperatures? Edited January 12, 2016 by shynung Quote Link to comment Share on other sites More sharing options...
RainDreamer Posted February 11, 2016 Share Posted February 11, 2016 While I don't have an answer to the above (that question also seem to warrant a thread) I have another question to bump this thread up: How does Range Safety officer blows up failed rockets? Do they have planted explosives on the rocket itself, or is there a way to just detonate the fuel reliably? Quote Link to comment Share on other sites More sharing options...
DerekL1963 Posted February 11, 2016 Share Posted February 11, 2016 19 minutes ago, RainDreamer said: How does Range Safety officer blows up failed rockets? Do they have planted explosives on the rocket itself There are explosives on the rocket itself. Usually some kind of linear charge to cut holes in the fuel tank and disperse the fuel. Quote Link to comment Share on other sites More sharing options...
p1t1o Posted February 11, 2016 Share Posted February 11, 2016 On 1/12/2016 at 2:17 PM, shynung said: If one were to bolt SABRE's precooler (from the engine that powers the Skylon SSTO concept) onto the intake of a typical turbojet engine, how much improvement can be expected from the engine, assuming constant exhaust temperatures? I'm not sure of the exact thermodynamic maths, but some important points: Typical turbojet engines power their compressor with a downstream turbine which scavenges its energy from the exhaust, reducing thrust. SABRE's compressor is powered by the heat recovered by the pre-cooler. A typical turbojet is built to withstand high temperatures using heavy/expensive/advanced alloys/ceramics, the higher temperatures it can withstand (at the compressor face, within the combustion chamber, the exhaust turbine etc) the higher its thermodynamic efficiency. One of the main advantages of SABRE is engine components don't have to withstand such high temperatures, meaning cheaper and lighter alloys can be used, the weight savings are a significant here. Any gas turbine engine will be specifically designed to operate under certain conditions, though bolting a precooler onto a typical turbojet might increase its performance, it may not be the most efficient thing to do (eg: your fancy high temperature alloys in your turbojet are now so much dead weight, precooler not providing power to compressor, thermodynamic cycles not tuned to operating temperature regimes) and may have unforseen consequences (brittle failure of compressor blades operating in -150C conditions?). Oh and typical turbojets tun on hydrocarbon fuel, whereas SABRE uses liquid hydrogen. The liquid hydrogen fuel is what is used as the heatsink for all the heat that the precooler removes from incoming compressed air. Bolting a precooler onto a typical jet means you have to lug around tons of LH2 AND tons of kerosene, and the H2 ends up just being dumped overboard (along with all that energy that could be powering your compressor, instead of your nice heavy exhaust turbine). Its not outside the bounds of possibility to build a turbojet that runs on hydrogen, but then its not a "typical" turbojet anymore and you're basically constructing a SABRE So best case, you could get an incremental increase in efficiency and thrust (whether this will be enough to justify the [large amount of] extra weight is debatable - see my opener about maths), worst case, catastrophic engine disassembly. IMHO Quote Link to comment Share on other sites More sharing options...
monophonic Posted February 11, 2016 Share Posted February 11, 2016 Allow me to continue. Could a rigid ringworld, that had a very uneven mass distribution, stay stable around it's parent body without active measures? If yes, how one-sided would the mass distribution have to be? I.E. would having the center of mass halfway between the center and the circumference of the ring be enough? Quote Link to comment Share on other sites More sharing options...
fredinno Posted February 11, 2016 Share Posted February 11, 2016 8 hours ago, monophonic said: Allow me to continue. Could a rigid ringworld, that had a very uneven mass distribution, stay stable around it's parent body without active measures? If yes, how one-sided would the mass distribution have to be? I.E. would having the center of mass halfway between the center and the circumference of the ring be enough? no. Quote Link to comment Share on other sites More sharing options...
KerbonautInTraining Posted March 2, 2016 Share Posted March 2, 2016 What's the difference between =/= and != I see them used pretty much interchangeably (Pls quote me in your response so I get a notification) Quote Link to comment Share on other sites More sharing options...
Spaceception Posted March 2, 2016 Share Posted March 2, 2016 (edited) 1 hour ago, KerbonautInTraining said: What's the difference between =/= and != I see them used pretty much interchangeably (Pls quote me in your response so I get a notification) =/= it isn't the same (At least in the times I've seen it being used) No flipping clue. Edited March 2, 2016 by Spaceception Quote Link to comment Share on other sites More sharing options...
SuperFastJellyfish Posted March 2, 2016 Share Posted March 2, 2016 (edited) 1 hour ago, KerbonautInTraining said: What's the difference between =/= and != I see them used pretty much interchangeably (Pls quote me in your response so I get a notification) They are both forms of 'not equal to' https://en.wikipedia.org/wiki/Equals_sign Edited March 2, 2016 by SuperFastJellyfish Quote Link to comment Share on other sites More sharing options...
Nibb31 Posted March 8, 2016 Share Posted March 8, 2016 On 2/3/2016 at 5:22 PM, KerbonautInTraining said: What's the difference between =/= and != I see them used pretty much interchangeably (Pls quote me in your response so I get a notification) There is also <>. It depends on the language you're using. Quote Link to comment Share on other sites More sharing options...
Atlas2342 Posted March 9, 2016 Share Posted March 9, 2016 Can an object/particle have a Schwarzschild radius smaller than the Planck length? Quote Link to comment Share on other sites More sharing options...
peadar1987 Posted March 9, 2016 Share Posted March 9, 2016 2 hours ago, Atlas2342 said: Can an object/particle have a Schwarzschild radius smaller than the Planck length? The neutrino has a Schwarzschild Radius of 8.46*10-61m (http://www.wolframalpha.com/input/?i=(2*(G)*(5.7E-34kg))%2F(c%5E2)). The Planck length is 16*10-36m. So yes, completely possible. Quote Link to comment Share on other sites More sharing options...
Wjolcz Posted March 9, 2016 Share Posted March 9, 2016 Can we have this thread pinned, please? Quote Link to comment Share on other sites More sharing options...
kunok Posted March 9, 2016 Share Posted March 9, 2016 4 hours ago, Veeltch said: Can we have this thread pinned, please? Thanks to our lovely mods, eternal thanks. I don't even know why wasn't already pinned Quote Link to comment Share on other sites More sharing options...
Wjolcz Posted March 9, 2016 Share Posted March 9, 2016 (edited) Thanks a ton to our lovely mods for doing this. Now, because I don't want to pollute the thread I should ask something I'm curious about: What happens when neutron stars lose their spin momentum? Can they become black holes? What happens then? Do they go supernova, or sth? Edited March 10, 2016 by Veeltch Quote Link to comment Share on other sites More sharing options...
fredinno Posted March 10, 2016 Share Posted March 10, 2016 11 hours ago, Veeltch said: Thanks a ton to our lovely mods for doing this. Now, because I don't want to pollute the thread I should ask something I'm curious about: What happens when neutron stars lose their spin momentum (radial velocity?)? Can they become black holes? What happens then? Do they go supernova, or sth? They stop emitting as much radiation. They still end up spinning though, just more and more slowly. Quote Link to comment Share on other sites More sharing options...
ment18 Posted March 10, 2016 Share Posted March 10, 2016 How is the thrust/ISP of NTR's calculated? I'm trying to calculate the size of the reactor for the RD-0410. Is ISP based on temperature of the fuel and thrust based on the total power of the reactor divided by the ISP? Quote Link to comment Share on other sites More sharing options...
fredinno Posted March 10, 2016 Share Posted March 10, 2016 5 hours ago, ment18 said: How is the thrust/ISP of NTR's calculated? I'm trying to calculate the size of the reactor for the RD-0410. Is ISP based on temperature of the fuel and thrust based on the total power of the reactor divided by the ISP? Dude, that link literally says the ISP. Quote Link to comment Share on other sites More sharing options...
ment18 Posted March 10, 2016 Share Posted March 10, 2016 Just now, fredinno said: Dude, that link literally says the ISP. I understand that, I am trying to work backwards to find the size of the reactor and would like to know the formula because I can't find it. Quote Link to comment Share on other sites More sharing options...
nohelmet Posted March 11, 2016 Share Posted March 11, 2016 (edited) On 2/11/2016 at 2:33 AM, monophonic said: Could a rigid ringworld, that had a very uneven mass distribution, stay stable around it's parent body without active measures? If yes, how one-sided would the mass distribution have to be? I.E. would having the center of mass halfway between the center and the circumference of the ring be enough? Yes, if you spin it.. Consider the moon: it is an extreme case of uneven ringworld. Edited March 11, 2016 by nohelmet Quote Link to comment Share on other sites More sharing options...
andrewas Posted March 11, 2016 Share Posted March 11, 2016 The problem is that the ring won't tidal lock, because the band of the ring will overpower any tidal effects on the mass concentration. Which means the band will eventually hit the planet. Quote Link to comment Share on other sites More sharing options...
nohelmet Posted March 12, 2016 Share Posted March 12, 2016 17 hours ago, andrewas said: The problem is that the ring won't tidal lock, because the band of the ring will overpower any tidal effects on the mass concentration. Which means the band will eventually hit the planet. Assuming that is true, it would mean we need the ring's center of mass nearer the planet than the ring. Since the ring spins around its CoM, then they won't collide. More precisely, we need the distance from CoM to planet + planet radius to be smaller than the distance from CoM to nearest ring point. Quote Link to comment Share on other sites More sharing options...
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