Entropian Posted September 25, 2020 Share Posted September 25, 2020 Darn, got ninja'd 33 minutes ago, JoeSchmuckatelli said: Okay - new question: what are the vertical - steeply angled tips on aircraft wings called? (first saw them on SW Airlines upgraded planes, and starting to see them on smaller jets) How do they affect performance /economy? This is a winglet: And a split-tip: As far as I know they are meant to recover some of the wingtip vortices' energy, increase the aspect ratio of the wing, and make the aircraft easier to handle. Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted September 25, 2020 Share Posted September 25, 2020 (edited) went to the Wikipedia page about these - and they've been around a long time. Why am I just noticing them recently? (i.e., I don't remember old SW airlines, or most passenger jets having them) Edited September 25, 2020 by JoeSchmuckatelli Quote Link to comment Share on other sites More sharing options...
magnemoe Posted September 25, 2020 Share Posted September 25, 2020 24 minutes ago, JoeSchmuckatelli said: went to the Wikipedia page about these - and they've been around a long time. Why am I just noticing them recently? (i.e., I don't remember old SW airlines, or most passenger jets having them) Its an process to upgrade to them, you only upgrade on refit, also benefit is smaller for short distance flights. Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted September 25, 2020 Share Posted September 25, 2020 Zero-g running Spoiler Quote Link to comment Share on other sites More sharing options...
TheSaint Posted September 25, 2020 Share Posted September 25, 2020 2 hours ago, kerbiloid said: Zero-g running Hide contents Proving once and for all that no matter how hard you try to get away, the bureaucrats will still have you running in circles. Quote Link to comment Share on other sites More sharing options...
K^2 Posted September 25, 2020 Share Posted September 25, 2020 I always enjoy watching conspiracy nuts try to explain Skylab. I don't think we ever had anything besides Saturn V that could have put it in orbit. 4 hours ago, magnemoe said: Its an process to upgrade to them, you only upgrade on refit, also benefit is smaller for short distance flights. I'm actually pretty sure winglets are an even greater boost to efficiency in takeoff and landing than in cruise, but yeah, since fuel is a much smaller fraction of operating cost on short hops, it probably doesn't make as much difference. It's also worth noting that while some types of winglets can be added in retrofit, some of the fancier ones, with these swooping curves, are both a more recent invention and are much harder to retrofit a plane with, so they only show up on new planes. Quote Link to comment Share on other sites More sharing options...
mikegarrison Posted September 25, 2020 Share Posted September 25, 2020 Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted September 26, 2020 Share Posted September 26, 2020 (edited) I thought this control scheme was unique to SpaceX... Looks like there are others using it as well https://en.m.wikipedia.org/wiki/GBU-43/B_MOAB#/media/File%3AMOABAFAM.JPG I wondered if SpaceX found this as an 'off the shelf' solution or if they licensed it to the USAF supplier... But then I learned they've been around for years https://en.m.wikipedia.org/wiki/Grid_fin Spoiler Spoiler Edited September 26, 2020 by JoeSchmuckatelli Can't eliminate the empty Spoiler Quote Link to comment Share on other sites More sharing options...
SOXBLOX Posted September 26, 2020 Share Posted September 26, 2020 Yeah, Russia used them on the AMRAAMski, and other missiles, like the Poplar ICBM. They do better than normal control surfaces at supersonic speeds. Also part of Soyuz's LES, and on the N-1, so not new to space launch, either. Quote Link to comment Share on other sites More sharing options...
ARS Posted September 27, 2020 Share Posted September 27, 2020 (edited) Does this moon system possible? A planet has 7 moons in total (It's not earth or any other planet in solar system), consisting of 1 medium-sized moon (roughly half the size of our moon) and 6 smaller moons (each roughly 10% the size of the first moon). All moons have their own orbit, and there's a period where all moons are visible in the same sky together. The moons are waxing and waning at different rate due to their different rotation and revolution period relative to the planet, resulting in different phases. Let's mark the main moon as A while smaller moons as number 1-6 (observer is at the same spot to be able to see all 7 moons together. A is tidally locked, but 1-6 are not) The phases are as follows: Monday: all 7 are present, A is at full moon Tuesday: 1 is invisible Wednesday: 1,2 is invisible Thursday: 1,2,3 is invisible Friday: 1,2,3,4 is invisible Saturday: 1,2,3,4,5 is invisible Sunday: all small moons invisible, A is at crescent moon Monday: all small moons invisible, A is at new moon Around every 3 months, all moons are always visible at the same sky at least once Note: invisible as in "not in the same sky with A" Edited September 27, 2020 by ARS Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted September 28, 2020 Share Posted September 28, 2020 On 9/7/2020 at 6:03 PM, K^2 said: Which isn't actually correct. Closed timelike curve (CTC) is a feature of GR. Albeit, there is CTC conjecture stating that stable metric allowing for CTC cannot arise from positive definte energy density. Meaning, you need at least some negative energy to go back in time. Two notable pounts here are that it is a conjecture, meaning no complete proof exists, and that it only applies to stable solutions. Unstable solutions to Einstein Field Equations allowing for CTC are known. Naked singularity case of Kerr metric is best known example. So while we're pretty sure you can't create anything stable that permanently allows time travel, catastrophic events allowing for brief window are a definite possibility. Parameters for such hypothetical event are not known, but if Kerr case is anything to go by, something like black hole collision at a minimum. So, several days ago - in response to a question of mine about time k^2 dropped the CTC info quoted above. This kind of info always kind of percolates as I try to improve my understanding of the concepts. Interestingly I'll often run into other info on the topic, but rarely do I find a new paper purporting a change in the current understanding. This one does: https://iopscience.iop.org/article/10.1088/1361-6382/aba4bc Spoiler Previous research has proposed a framework for deterministic, reversible, dynamics compatible with non-trivial time travel, where observers in distinct regions of spacetime can perform arbitrary local operations with no contradiction arising. However, only scenarios with up to three regions have been fully characterised, revealing only one type of process where the observers can verify to both be in the past and future of each other. Here we extend this characterisation to an arbitrary number of regions and find that there exist several inequivalent processes that can only arise due to non-trivial time travel. This supports the view that complex dynamics is possible in the presence of CTCs, compatible with free choice of local operations and free of inconsistencies I'm still grinding through it - but I thought I would share this to anyone interested Quote Link to comment Share on other sites More sharing options...
DDE Posted September 29, 2020 Share Posted September 29, 2020 https://science.sciencemag.org/content/369/6511/1626 So, were the Norse the wisest of us all? Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted September 30, 2020 Share Posted September 30, 2020 8 hours ago, DDE said: So, were the Norse the wisest of us all? Of course. Spoiler Quote Link to comment Share on other sites More sharing options...
wumpus Posted September 30, 2020 Share Posted September 30, 2020 20 hours ago, DDE said: https://science.sciencemag.org/content/369/6511/1626 So, were the Norse the wisest of us all? Just one? Is the other out on reconnaissance? Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted October 2, 2020 Share Posted October 2, 2020 On 9/30/2020 at 12:48 AM, kerbiloid said: Of course. Hide contents Personification of Loki in that series. Now for something completely different. Spaaaaace Toilet: https://m.huffpost.com/us/entry/us_5f764f76c5b6dd94f1e8090f Now new and improved Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted October 2, 2020 Share Posted October 2, 2020 So, was that an easter egg from NASA or a source of inspiration for them? Spoiler Quote Link to comment Share on other sites More sharing options...
ARS Posted October 5, 2020 Share Posted October 5, 2020 Is it possible for a planet to have atmospheric cloud so thick that even orbital radar imaging cannot map it's surface feature (or at least obscure it's high resolution image)? With the only way to observe it is by sending probe down there? Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted October 5, 2020 Share Posted October 5, 2020 Yes, when they become so thick that turn into ice or metallic hydrogen. Quote Link to comment Share on other sites More sharing options...
DDE Posted October 5, 2020 Share Posted October 5, 2020 4 hours ago, ARS said: Is it possible for a planet to have atmospheric cloud so thick that even orbital radar imaging cannot map it's surface feature (or at least obscure it's high resolution image)? With the only way to observe it is by sending probe down there? Hm. I think we should go the oblique way. You see, some radio waves are actually quite sensitive to atmospheric moisture, but we've long since learnt to solve that problem. The Soviets worked on using ionized particles in air or vacuum as a short-term shield against radar and lasers. If you're somehow able to arrange for carbon nanoparticles, you might have a workable "stealth planet". https://www.thespacereview.com/article/3536/1 Quote Link to comment Share on other sites More sharing options...
ARS Posted October 5, 2020 Share Posted October 5, 2020 5 minutes ago, DDE said: The Soviets worked on using ionized particles in air or vacuum as a short-term shield against radar and lasers. If you're somehow able to arrange for carbon nanoparticles, you might have a workable "stealth planet". That's what I'm thinking: A planet with atmospheric condition that renders it impenetrable by radio waves and optical sensors, essentially creating a stealth planet where any orbital observation of it's surface feature is impossible Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted October 5, 2020 Share Posted October 5, 2020 A planet hidden behind the ion cloud from Firefly / Serenity and Lexx (Potato-Ho). But if the ion cloud is a thin layer next to surface, you can research the landscape by measuring the cloud currents. Quote Link to comment Share on other sites More sharing options...
Gargamel Posted October 5, 2020 Share Posted October 5, 2020 Wasn't the one planet in The Hitchhiker's series surrounded by such a cloud? The planet was the one they built the great cricket (Oh yeah the planet was Krikkit!) gate to keep it isolated cause they tried to conquer obliterate the universe. Quote Link to comment Share on other sites More sharing options...
Clamp-o-Tron Posted October 5, 2020 Share Posted October 5, 2020 Does this check out? https://www.improbable.com/airchives/paperair/volume21/v21i2/Influence of Coriolis Force.pdf Website is basically the ig nobel archives, but nothing "UFO"-like. Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted October 5, 2020 Share Posted October 5, 2020 (edited) Perhaps if you were at the correct latitude and strapped into a chair that restricted head movement for 10 years... Maybe... But given that you are constantly reorienting throughout the day... Nah. That's one of those 'when you hear hoofbeats think horses not zebras things' (iow - there are much more plausible causes - like the same process that drives fingerprints) Edited October 5, 2020 by JoeSchmuckatelli Quote Link to comment Share on other sites More sharing options...
K^2 Posted October 6, 2020 Share Posted October 6, 2020 3 hours ago, Clamp-o-Tron said: Does this check out? https://www.improbable.com/airchives/paperair/volume21/v21i2/Influence of Coriolis Force.pdf Website is basically the ig nobel archives, but nothing "UFO"-like. That is very clearly a joke article. Quote Link to comment Share on other sites More sharing options...
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