welshbairn Posted August 30, 2022 Share Posted August 30, 2022 (edited) The thing that confuses me about this is they have to cool the engines to close to 20 degrees above absolute zero, minus 250 c, to cope with a huge flow of very cold hydrogen and oxygen for lift off so they don't shatter or whatever from the rapid temperature change, but then the oxygen and hydrogen almost immediately join to explode in a massive increase in temperature so the engine casings very rapidly become red hot. Any material scientists on P&B who can tell me why a rapid reduction of temperature is more harmful than a rapid increase? Edited August 30, 2022 by welshbairn 0 Quote Link to comment Share on other sites More sharing options...
parsforlife Posted August 30, 2022 Share Posted August 30, 2022 6 minutes ago, welshbairn said: The thing that confuses me about this is they have to cool the engines to close to 20 degrees above absolute zero, minus 250 c, to cope with huge flow of very cold hydrogen and oxygen for lift off so they don't shatter or whatever from the rapid temperature change, but then the oxygen and hydrogen almost immediately join to explode in a massive increase in temperature so the engine casings very rapidly become red hot. Any material scientists on P&B who can tell me why a rapid reduction of temperature is more harmful than a rapid increase? With nothing but unused physics behind me I would guess its the materials being better at handling expansion vs contraction. 0 Quote Link to comment Share on other sites More sharing options...
welshbairn Posted August 30, 2022 Share Posted August 30, 2022 (edited) 20 minutes ago, parsforlife said: With nothing but unused physics behind me I would guess its the materials being better at handling expansion vs contraction. Aye, maybe it's about molecules moving closer together being more traumatic to structural integrity than moving apart. Or something about the speed of atoms bombing about, slowing down making the materials more rigid, speeding up making them more flexible. @Melanius Mullarkay might have a clue, despite what people say... Edited August 30, 2022 by welshbairn 0 Quote Link to comment Share on other sites More sharing options...
Bairnardo Posted August 31, 2022 Share Posted August 31, 2022 Aye, maybe it's about molecules moving closer together being more traumatic to structural integrity than moving apart. Or something about the speed of atoms bombing about, slowing down making the materials more rigid, speeding up making them more flexible. [mention=70922]Melanius Mullarkay[/mention] might have a clue, despite what people say...I'm going to guess that the metals are designed to handle either, but the temperature shock of the combustion is a neccessary one, whereas the cold shock can be avoided by taking some time. Even if a metal is designed to handle the stress of extremes, doesn't mean its not prudent to avoid it where possible. 0 Quote Link to comment Share on other sites More sharing options...
welshbairn Posted August 31, 2022 Share Posted August 31, 2022 6 hours ago, Bairnardo said: 14 hours ago, welshbairn said: Aye, maybe it's about molecules moving closer together being more traumatic to structural integrity than moving apart. Or something about the speed of atoms bombing about, slowing down making the materials more rigid, speeding up making them more flexible. [mention=70922]Melanius Mullarkay[/mention] might have a clue, despite what people say... I'm going to guess that the metals are designed to handle either, but the temperature shock of the combustion is a neccessary one, whereas the cold shock can be avoided by taking some time. Even if a metal is designed to handle the stress of extremes, doesn't mean its not prudent to avoid it where possible. Yeah and having an engine switching from ambient environment to minus 250c and then up to 3000c, all in a few seconds, would be hugely and unnecessarily stressful, as you say 0 Quote Link to comment Share on other sites More sharing options...
welshbairn Posted September 1, 2022 Share Posted September 1, 2022 James Webb snaps first direct images of a planet outside the solar system. https://www.theguardian.com/science/2022/sep/01/historic-james-webb-images-show-exoplanet-unprecedented-detail 1 Quote Link to comment Share on other sites More sharing options...
jamieson87 Posted September 1, 2022 Share Posted September 1, 2022 An expansive look into why the Fermi paradox may not be asking the right questions. https://thedebrief.org/the-paradox-of-fermis-paradox/ 0 Quote Link to comment Share on other sites More sharing options...
welshbairn Posted September 3, 2022 Share Posted September 3, 2022 Boo. 0 Quote Link to comment Share on other sites More sharing options...
welshbairn Posted September 3, 2022 Share Posted September 3, 2022 Sounds like this scrub was due to a gasket on a quick disconnect valve that allows a fuel line to separate from the rocket when it takes off. It's unlikely they'll be able to try again before the second half of October as there are batteries that likely need replacing which means going back to the shed, then SpaceX are launching early October. 0 Quote Link to comment Share on other sites More sharing options...
Newbornbairn Posted September 5, 2022 Share Posted September 5, 2022 0 Quote Link to comment Share on other sites More sharing options...
welshbairn Posted September 8, 2022 Share Posted September 8, 2022 This would have been unimaginable 10 years ago but it's happening every few weeks with SpaceX. Imagine what it would cost to fly to Malaga if they had to build a new plane every trip. It's not incredibly complex technology or patented techniques, anybody could copy it, and China probably will, but the only reason Artemis 1 will cost $4 billion just to launch is that only a tiny part of it will return to Earth, and that's down to pork barrel politics. 0 Quote Link to comment Share on other sites More sharing options...
dorlomin Posted September 15, 2022 Share Posted September 15, 2022 (edited) I am pretty sure north of Glasgow is not the north west coast. That aside seems to have been quite the site. Most likely not big enough to have reached the ground, but who knows. Edited September 15, 2022 by dorlomin 0 Quote Link to comment Share on other sites More sharing options...
Gnash Posted September 15, 2022 Share Posted September 15, 2022 11 minutes ago, dorlomin said: I am pretty sure north of Glasgow is not the north west coast. That aside seems to have been quite the site. Most likely not big enough to have reached the ground, but who knows. Very exciting, but I think you need to brush up on your geography if you don't think the northwestern coast of Scotland is north of Glasgow. 1 Quote Link to comment Share on other sites More sharing options...
Utdtillidie2 Posted September 15, 2022 Share Posted September 15, 2022 It was heading west when it passed over us in Ayr last night. 0 Quote Link to comment Share on other sites More sharing options...
topcat(The most tip top) Posted September 15, 2022 Share Posted September 15, 2022 57 minutes ago, Gnash said: Very exciting, but I think you need to brush up on your geography if you don't think the northwestern coast of Scotland is north of Glasgow. I'm not a qualified Geographer but I'd have thought that as there's basically a sharp angle between the North coast and the West coast we don't really have a Northwestern coast 0 Quote Link to comment Share on other sites More sharing options...
Florentine_Pogen Posted September 15, 2022 Share Posted September 15, 2022 https://www.theguardian.com/science/2022/sep/15/incredible-fireball-crosses-sky-over-scotland-and-northern-ireland 0 Quote Link to comment Share on other sites More sharing options...
Newbornbairn Posted September 15, 2022 Share Posted September 15, 2022 9 hours ago, Florentine_Pogen said: https://www.theguardian.com/science/2022/sep/15/incredible-fireball-crosses-sky-over-scotland-and-northern-ireland Quote UK Fireball Alliance Wait, the what? 0 Quote Link to comment Share on other sites More sharing options...
Florentine_Pogen Posted September 15, 2022 Share Posted September 15, 2022 4 minutes ago, Newbornbairn said: Wait, the what? 0 Quote Link to comment Share on other sites More sharing options...
tamthebam Posted September 15, 2022 Share Posted September 15, 2022 2 hours ago, Florentine_Pogen said: I'm sure there were football fans (maybe an English club) who adopted the Fireball XL5 song. I can't remember which team though 0 Quote Link to comment Share on other sites More sharing options...
welshbairn Posted September 15, 2022 Share Posted September 15, 2022 Bezos's million dollar fairground ride has experienced an "off nominal situation". 0 Quote Link to comment Share on other sites More sharing options...
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