AHHans Posted December 16, 2020 Share Posted December 16, 2020 9 minutes ago, kerbiloid said: Confused the "Oberth effect" and the "Oberth maneuver". [copy ... Wikipedia ... paste] Oh, that's a thing? Well, the "Oberth maneuver" is one special application of the "Oberth effect". Quote Link to comment Share on other sites More sharing options...
DDE Posted December 16, 2020 Share Posted December 16, 2020 (edited) 4 hours ago, AHHans said: Wasn't there a probe recently that was something like two thirds heat-shield and burned away most of that while entering Jupiter's atmosphere? I wouldn't exactly call Galileo recent. Edited December 16, 2020 by DDE Quote Link to comment Share on other sites More sharing options...
AHHans Posted December 16, 2020 Share Posted December 16, 2020 24 minutes ago, DDE said: I wouldn't exactly call Galileo recent. Thanks for the link! And well, maybe not so recent... Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted December 17, 2020 Share Posted December 17, 2020 7 hours ago, AHHans said: Thanks for the link! And well, maybe not so recent... Hey - the late 80s/early 90s was like yesterday, right? ... Feels like it, at least Quote Link to comment Share on other sites More sharing options...
TheSaint Posted December 17, 2020 Share Posted December 17, 2020 1 hour ago, JoeSchmuckatelli said: Hey - the late 80s/early 90s was like yesterday, right? ... Feels like it, at least It certainly wasn't thirty years ago, because that would mean I was getting old. And that's just not possible. Quote Link to comment Share on other sites More sharing options...
Snark Posted December 18, 2020 Share Posted December 18, 2020 Moderator's note: @ARS asked an interesting question about calculating interatomic distances in metals, and the ensuing discussion became quite lengthy, so it has been split off into a separate thread (including the original question). The new thread is located here: We now return you to your original thread, already in progress. Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted December 22, 2020 Share Posted December 22, 2020 Jupiter and Saturn conjunction: any good pics coming out of Hubble or other big observatories? I've not found much Quote Link to comment Share on other sites More sharing options...
Brotoro Posted December 22, 2020 Share Posted December 22, 2020 This isn't a question, but here's a picture I took today of the Jupiter/Saturn conjunction. The picture of the Moon is taken today at the same scale. Taken through 127mm Maksutov-Cassegrain telescope, 17mm eyepiece, iPhone 11 focal setup. *afocal setup Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted December 22, 2020 Share Posted December 22, 2020 (edited) @BrotoroFantastic! ...Takes me back to when I was in college looking through the University telescope (albeit at each, individually) . Great pic! Okay - So --- I'm still hoping for links to images from the Saturn / Jupiter conjugation; but I can't resist posting this: Japan space agency reveals what's inside capsule brought back from asteroid - CBS News You can see the regolith that Hayabusa2 brought back -- but the crazy thing: why is the guy carrying the sample container in (effectively) a bomb-hazmat suit? Edited December 22, 2020 by JoeSchmuckatelli Quote Link to comment Share on other sites More sharing options...
Reactordrone Posted December 22, 2020 Share Posted December 22, 2020 (edited) The clouds parted for about an hour around sunset so managed to get a shot of the conjunction, https://imgur.com/gallery/pcDp20S Edited December 22, 2020 by Reactordrone Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted December 22, 2020 Share Posted December 22, 2020 37 minutes ago, Reactordrone said: The clouds parted for about an hour around sunset so managed to get a shot of the conjunction, https://imgur.com/gallery/pcDp20S That's cool too: you can see the banding on Jupiter and the rings! Quote Link to comment Share on other sites More sharing options...
Entropian Posted December 22, 2020 Share Posted December 22, 2020 (edited) 14 hours ago, Brotoro said: This isn't a question, but here's a picture I took today of the Jupiter/Saturn conjunction. The picture of the Moon is taken today at the same scale. Taken through 127mm Maksutov-Cassegrain telescope, 17mm eyepiece, iPhone 11 focal setup. Amazing photo. I went out with my Maksutov-Cassegrain (convergent evolution, ) last night but clouds rolled in right as I was getting set up. Edited December 22, 2020 by Entropian Quote Link to comment Share on other sites More sharing options...
magnemoe Posted December 22, 2020 Share Posted December 22, 2020 12 hours ago, JoeSchmuckatelli said: @BrotoroFantastic! ...Takes me back to when I was in college looking through the University telescope (albeit at each, individually) Great pic! Okay - So --- I'm still hoping for links to images from the Saturn / Jupiter conjugation; but I can't resist posting this: Japan space agency reveals what's inside capsule brought back from asteroid - CBS News You can see the regolith that Hayabusa2 brought back -- but the crazy thing: why is the guy carrying the sample container in (effectively) a bomb-hazmat suit? Yes, its looks like an bomb protection suit, who make little sense, the reason for that suits is giving you protection if something explodes. Now I assume nothing on the return capsule can explode. Perhaps it was to protect from the wildlife Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted December 22, 2020 Share Posted December 22, 2020 1 hour ago, magnemoe said: Yes, its looks like an bomb protection suit, who make little sense, the reason for that suits is giving you protection if something explodes. Now I assume nothing on the return capsule can explode. Perhaps it was to protect from the wildlife Well, it’s possible that there were unfired (redundant) pyrotechnics on the craft Quote Link to comment Share on other sites More sharing options...
AHHans Posted December 22, 2020 Share Posted December 22, 2020 Another possibility is that they feared that the samples from the comet might react rather violently with the oxygen in our atmosphere. IIRC there is quite a bit of carbon in that material. Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted December 22, 2020 Share Posted December 22, 2020 2 hours ago, magnemoe said: Yes, its looks like an bomb protection suit, who make little sense, the reason for that suits is giving you protection if something explodes. Now I assume nothing on the return capsule can explode. Perhaps it was to protect from the wildlife Drop bears? Quote Link to comment Share on other sites More sharing options...
TheSaint Posted December 22, 2020 Share Posted December 22, 2020 3 hours ago, StrandedonEarth said: Well, it’s possible that there were unfired (redundant) pyrotechnics on the craft That's what I was thinking. Either redundant or misfired. Quote Link to comment Share on other sites More sharing options...
RCgothic Posted December 22, 2020 Share Posted December 22, 2020 Random musing I think probably doesn't deserve its own thread: Space Shuttle would have been better with Kerolox Main Engines. My reasoning: 1. No insulation foam. 2. RP1 up top would prevent falling ice. 3. Extreme reusability of Kerolox engines have been demonstrated. 4. It doesn't need to go BLEO so low ISP isn't a handicap. 5. Smaller External Tank. Yes it would be about 700t heavier on the pad, but it'd still be lighter than Saturn. Quote Link to comment Share on other sites More sharing options...
magnemoe Posted December 22, 2020 Share Posted December 22, 2020 5 hours ago, JoeSchmuckatelli said: Drop bears? They are an problem, I would be more scared of kangaroos with manpads https://www.snopes.com/fact-check/shoot-me-kangaroo-down-sport/ Still the real nightmare is the snakes and the primates who are better armed than the kangaroos Quote Link to comment Share on other sites More sharing options...
DDE Posted December 23, 2020 Share Posted December 23, 2020 11 hours ago, RCgothic said: Extreme reusability of Kerolox engines have been demonstrated. Was it, though? I believe the coking is the reason for the rush to methalox. Quote Link to comment Share on other sites More sharing options...
RCgothic Posted December 23, 2020 Share Posted December 23, 2020 2 hours ago, DDE said: Was it, though? I believe the coking is the reason for the rush to methalox. Whilst I'm not sure if individual Merlins have flown/fired more times than SSMEs, I believe the SSMEs were completely overhauled between flights whereas Merlins apparently needs little more than cleaning fluid. Quote Link to comment Share on other sites More sharing options...
ARS Posted December 23, 2020 Share Posted December 23, 2020 Does this situation possible considering how light reflects off a reflective surface? 2 Snipers are hunting each other. They are elite soldiers expert in camouflage. At one point, while both are under camouflage, and facing each other (they're not aware they are staring at each other), the sun is positioned in such a way that the sunlight glints from the scope's lens of both of them (basically they see the scope glint of each other, not just only one of them) Also, since lasers can reflect off reflective surface, is it possible for sufficiently powerful laser to not reflect off reflective surface at all simply by burning through it from the sheer amount of heat at the moment of contact? Basically a laser that melts through the mirror it's supposed to reflect off Quote Link to comment Share on other sites More sharing options...
lrd.Helmet Posted December 23, 2020 Share Posted December 23, 2020 (edited) 1 hour ago, ARS said: 2 Snipers are hunting each other. They are elite soldiers expert in camouflage. At one point, while both are under camouflage, and facing each other (they're not aware they are staring at each other), the sun is positioned in such a way that the sunlight glints from the scope's lens of both of them (basically they see the scope glint of each other, not just only one of them) That would only work when the front element (the glass) of the scope extends beyond the hood of the scope and the sun is perpendicular to both snipers. Or when the sunlight bounces of something else into the scope. However I don't think scopes have extending front elements, because a lens hood prevents flaring and other visual artefacts. 1 hour ago, ARS said: Also, since lasers can reflect off reflective surface, is it possible for sufficiently powerful laser to not reflect off reflective surface at all simply by burning through it from the sheer amount of heat at the moment of contact? Basically a laser that melts through the mirror it's supposed to reflect off A mirror will still reflect some of the light. So if there is a insanely powerful laser there is a reflection of that laser. However if the laser is powerful enough to instantly melt/vapourize the mirror the reflection might last too short to notice. Assuming a mirror reflects 99% of the laser something else is going to receive 99% of that laser too and that something is going to get burned too. Edited December 23, 2020 by lrd.Helmet more stuff Quote Link to comment Share on other sites More sharing options...
tater Posted December 23, 2020 Share Posted December 23, 2020 Interesting. https://www.technologyreview.com/2019/10/26/132171/a-neural-net-solves-the-three-body-problem-100-million-times-faster/ Quote Link to comment Share on other sites More sharing options...
tater Posted December 23, 2020 Share Posted December 23, 2020 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.