DDE Posted February 5, 2020 Share Posted February 5, 2020 20 minutes ago, ARS said: If that's the case, then it is possible to obtain similar or higher power density than LBCFR with an added advantage of better cooling due to high-temp gas cooled reactor allowing a larger coolant fraction in the core (due to the low number density of gas coolant) It seems like an unexploited niche. Apparently there are advantages to a DC electric motor, at least in azipod design, and handily, an MHD produces DC while also achieving much higher efficiency. At least on paper. And it's not a big step. Aside from the French, it is my understanding that even the Yasens have a turboelectric mode for silent running. Quote Link to comment Share on other sites More sharing options...
ARS Posted February 6, 2020 Share Posted February 6, 2020 Is it possible for a planet that's formed outside of goldilocks zone (either closer or farther towards the sun compared to earth) to contain Oxygen as one of the main component of it's atmosphere (doesn't have to be at breathable concentration) from the gases that forms the atmosphere of the planet (as in, a planet with oxygen content in it's atmosphere with no plants whatsoever)? Quote Link to comment Share on other sites More sharing options...
DDE Posted February 6, 2020 Share Posted February 6, 2020 1 hour ago, ARS said: Is it possible for a planet that's formed outside of goldilocks zone (either closer or farther towards the sun compared to earth) to contain Oxygen as one of the main component of it's atmosphere (doesn't have to be at breathable concentration) from the gases that forms the atmosphere of the planet (as in, a planet with oxygen content in it's atmosphere with no plants whatsoever)? Yes and no. Oxygen is very reactive and can't stay around for long without constant replenishment. On the other hand, every icy body in the outer Solar System has a thin 'atmosphere' of oxygen from water-dissociated water. Including Pluto. Quote Link to comment Share on other sites More sharing options...
magnemoe Posted February 6, 2020 Share Posted February 6, 2020 1 hour ago, ARS said: Is it possible for a planet that's formed outside of goldilocks zone (either closer or farther towards the sun compared to earth) to contain Oxygen as one of the main component of it's atmosphere (doesn't have to be at breathable concentration) from the gases that forms the atmosphere of the planet (as in, a planet with oxygen content in it's atmosphere with no plants whatsoever)? One option is an atmosphere with mostly oxygen. This require water and solar radiation who split the water molecules into hydrogen and oxygen, hydrogen escapes. Think this require an large and hot star? Or did this happen on Venus? An large and hot star will not live long, but might live long enough to produce life who produce oxygen. This is an reason why O2, is not an perfect bio signature. Quote Link to comment Share on other sites More sharing options...
mikegarrison Posted February 7, 2020 Share Posted February 7, 2020 (edited) https://xkcd.com/2264/ Edited February 7, 2020 by mikegarrison Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted February 7, 2020 Share Posted February 7, 2020 (edited) 8 hours ago, DDE said: Oxygen is very reactive and can't stay around for long without constant replenishment. You frighten me... (Starts gathering empty PET cans to store the oxygen while it's around.) *** Afaik, iron deoxidation in the upper layers of the planet core will cause massive flow of oxygen, which will raise to the surface (because the underlying minerals are already oxidized, mostly). And hundreds millions of years later, at the end of the gravitational differentiation, when all original iron oxides split into iron (core) and this oxygen, this will cause significant raise of oxygen concentration in atmosphere, killing primitive remains of life on the Earth. (Just in case: this doesn't relate to the water and UV in any form, it's reduction of the iron oxides). So, probably any Earth-like rocky planet enough massive to hold the atmosphere will have some period of oxygen-rich atmosphere. Lesser ones will loose this oxygen as any other gas. Bigger ones have a lot of hydrocarbons and so on to fully oxidize it with this oxygen, and turn it into the water and carbon dioxide. Edited February 7, 2020 by kerbiloid Quote Link to comment Share on other sites More sharing options...
ARS Posted February 8, 2020 Share Posted February 8, 2020 Weather condition plays a vital role in aviation where it determines the flight of aircraft, whether it's safe to fly or not. What about spaceflight? Does the weather plays a vital role too? Especially during the ascent phase (even if it's brief). What's the weather parameters that must be checked before declaring it's safe for launch? I am particularly interested with space shuttles, since it's arrangement and assembly is different than regular rockets (being a plane strapped to giant fuel tanks with strap-on boosters instead of towers of stacked fuel tanks and engines of regular rockets) Quote Link to comment Share on other sites More sharing options...
razark Posted February 8, 2020 Share Posted February 8, 2020 (edited) 24 minutes ago, ARS said: What's the weather parameters that must be checked before declaring it's safe for launch? I am particularly interested with space shuttles... https://www.nasa.gov/centers/kennedy/news/releases/2003/release-20030128.html Post Columbia, there may have been additional rules to visibility. Edited February 8, 2020 by razark Quote Link to comment Share on other sites More sharing options...
DDE Posted February 8, 2020 Share Posted February 8, 2020 3 hours ago, ARS said: Weather condition plays a vital role in aviation where it determines the flight of aircraft, whether it's safe to fly or not. What about spaceflight? Does the weather plays a vital role too? Especially during the ascent phase (even if it's brief). What's the weather parameters that must be checked before declaring it's safe for launch? I am particularly interested with space shuttles, since it's arrangement and assembly is different than regular rockets (being a plane strapped to giant fuel tanks with strap-on boosters instead of towers of stacked fuel tanks and engines of regular rockets) SpaceX fandom has a meme for that scrub reason. Quote Link to comment Share on other sites More sharing options...
magnemoe Posted February 9, 2020 Share Posted February 9, 2020 5 hours ago, DDE said: SpaceX fandom has a meme for that scrub reason. First stage recovery makes weather much more of an issue. If you don't plan to land its more like artillery than aviation. Quote Link to comment Share on other sites More sharing options...
DDE Posted February 9, 2020 Share Posted February 9, 2020 9 hours ago, magnemoe said: more like artillery than aviation Ah, the big internal battle that cost the Soviets the Moon. Quote Link to comment Share on other sites More sharing options...
zeilden Posted February 11, 2020 Share Posted February 11, 2020 Is a generation ship ethical? Quote Link to comment Share on other sites More sharing options...
DDE Posted February 11, 2020 Share Posted February 11, 2020 2 hours ago, zeilden said: Is a generation ship ethical? No, it is technological. What you should have asked is whether it's moral. At which point you end ho walking in circles because morals, as studied by the science of ethics, are a very disagreeable subject. Welcome to the forum anyway! Quote Link to comment Share on other sites More sharing options...
p1t1o Posted February 11, 2020 Share Posted February 11, 2020 1 hour ago, zeilden said: Is a generation ship ethical? Short answer: In their currently imagined form (ie: severe restrictions, deficits and difficulties of many different kinds, even in the most optimistic of scenarios, when compared to living on Earth)? No. With near-infinite resources (see: Shkadov thruster) maybe. But it may be relatively ethical compared to say, allowing humanity to become extinct. Or if living conditions changed on Earth, the balance of morals/ethics could change. I think everyone would agree that generation ships are among the the least desirable forms of space travel. By some significant definitions, it cannot even be regarded as "travel", in a human sense, since nobody who boards the ship gets off, and nobody that arrives at the destination has ever existed at the origin. Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted February 11, 2020 Share Posted February 11, 2020 Spoiler 5 suicidal maniacs vs 1 ? And what is that man with a vacuum cleaner doing near the rails? He is not sure to which party join? Quote Link to comment Share on other sites More sharing options...
p1t1o Posted February 13, 2020 Share Posted February 13, 2020 (edited) I have a question: Why does/did it say "United States" on the side of NASA rockets and also airforce ICBMs? (actually, especially ICBMs, since basically nobody ever really saw them apart from the staff who physically built them and delivered them to the silos) I cant think of a single reason. I mean, theres no reason why not....but its a bit like tattooing my own name into my armpit. Edited February 13, 2020 by p1t1o Quote Link to comment Share on other sites More sharing options...
mikegarrison Posted February 13, 2020 Share Posted February 13, 2020 28 minutes ago, p1t1o said: Why does/did it say "United States" on the side of NASA rockets and also airforce ICBMs? https://en.wikipedia.org/wiki/Brand Quote Link to comment Share on other sites More sharing options...
magnemoe Posted February 13, 2020 Share Posted February 13, 2020 19 minutes ago, p1t1o said: I have a question: Why does/did it say "United States" on the side of NASA rockets and also airforce ICBMs? (actually, especially ICBMs, since basically nobody ever really saw them apart from the staff who physically built them and delivered them to the silos) I cant think of a single reason. I mean, theres no reason why not....but its a bit like tattooing my own name into my armpit. On orbital rockets it makes some sense at least during the cold war, SpaceX rockets has spaceX on them. However it don't looks like its painted on ICBM, they tend to have the US Air Force on them, and this tend to be either test launches or static displays both are seen. Goggled this and it don't looks like missiles in silos has it. They might have the air force emblem because tradition. it might also be to mark them as US rockets because warplanes has to be marked as so. No its not very relevant for an ICBM and tactical rockets are not marked as I know Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted February 13, 2020 Share Posted February 13, 2020 Maybe there is "Property of the Government of the" written with smaller and darker font. And "All rights reserved" after that. Quote Link to comment Share on other sites More sharing options...
razark Posted February 13, 2020 Share Posted February 13, 2020 23 minutes ago, kerbiloid said: Maybe there is "Property of the Government of the" written with smaller and darker font. Nah, that's a one-inch round sticker, printed blue on a silver background. Quote Link to comment Share on other sites More sharing options...
ARS Posted February 13, 2020 Share Posted February 13, 2020 So... I had a few questions. I found this formula for converting the relative humidity into absolute humidity. The problem is, it only shows the T (temperature), and rh (relative humidity). What's the number represents for? Is it constants? Can anyone explain? source: https://carnotcycle.wordpress.com/2012/08/04/how-to-convert-relative-humidity-to-absolute-humidity/ Quote Link to comment Share on other sites More sharing options...
mikegarrison Posted February 14, 2020 Share Posted February 14, 2020 1 hour ago, ARS said: So... I had a few questions. I found this formula for converting the relative humidity into absolute humidity. The problem is, it only shows the T (temperature), and rh (relative humidity). What's the number represents for? Is it constants? Can anyone explain? source: https://carnotcycle.wordpress.com/2012/08/04/how-to-convert-relative-humidity-to-absolute-humidity/ Why is that a problem? Those are the most important variables. Atmospheric pressure also has a smaller effect. If you are talking about an atmosphere other than Earth's, then those constants would be different. Quote Link to comment Share on other sites More sharing options...
ARS Posted February 14, 2020 Share Posted February 14, 2020 33 minutes ago, mikegarrison said: Why is that a problem? Those are the most important variables. Atmospheric pressure also has a smaller effect. If you are talking about an atmosphere other than Earth's, then those constants would be different. No, I just want to know what the numbers represents Quote Link to comment Share on other sites More sharing options...
mikegarrison Posted February 14, 2020 Share Posted February 14, 2020 (edited) 37 minutes ago, ARS said: No, I just want to know what the numbers represents 273.15 is a conversion to Kelvin temperature, so it implies T is supposed to be in deg C for that equation. I am pretty sure the rest are derived from the ideal gas laws and physical constants associated with water and dry air. I mean, you know what relative humidity is, right? It's a measure of the saturation pressure of water vapor compared to the partial pressure of water in the air. When the partial pressure of water exceeds the saturation pressure, then water will start to condense as liquid. That is 100% relative humidity. If you want a full derivation, I'm sure you can look this up just as easily as I can. Edited February 14, 2020 by mikegarrison Quote Link to comment Share on other sites More sharing options...
ARS Posted February 14, 2020 Share Posted February 14, 2020 10 minutes ago, mikegarrison said: 273.15 is a conversion to Kelvin temperature, so it implies T is supposed to be in deg C for that equation. I am pretty sure the rest are derived from the ideal gas laws and physical constants associated with water and dry air. I mean, you know what relative humidity is, right? It's a measure of the saturation pressure of water vapor compared to the partial pressure of water in the air. When the partial pressure of water exceeds the saturation pressure, then water will start to condense as liquid. That is 100% relative humidity. If you want a full derivation, I'm sure you can look this up just as easily as I can. Thanks! now that clears something up. I just getting some school project that involves measuring absolute air humidity, which makes me confused since I'm not familiar with this matter before before Quote Link to comment Share on other sites More sharing options...
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