5 ms·
Good advice: 1. Never invade Russia in winter. 2. Make sure your robotic lunar lander has a low center of gravity.
by dreamcompiler 2y ago
Good advice:
1. Never invade Russia in winter.
2. Make sure your robotic lunar lander has a low center of gravity.
- BugsJustFindMe 2y ago> Never invade Russia in winter. I thought it was never get involved in a land war in Asia.
- analog31 2y agoEspecially never invade the part of Russia that's in Asia, in winter.
- marcosdumay 2y agoThe thing about the more generalized form is that on most of the cases people remember, the invasion started on spring or summer.
- analog31 2y agoIndeed, and there are two fields where "when will the project be finished" is recognized as a logical fallacy: Software development, and warfare.
- bluGill 2y agoThere are been lot of land wars in Asia over history. Sometimes it goes well for the defender, sometimes the attacker. Never get involved in a war is good advice, but sometimes impossible to keep.
- mannyv 2y agoUnless you're Asian, then you'll win.
- jordanb 2y agoTell that to the Japanese.
- thaumasiotes 2y agoWhat are you referring to? They had a failed invasion of Korea; they had a very successful invasion of China that ended when they were defeated in a naval war well outside of Asia.
- jordanb 2y agoThe invasion of China wasn't successful. It was a quagmire. Japan didn't have the men or resources to conquer China and Chiang could just retreat whenever he had to.
- thaumasiotes 2y ago> Japan didn't have the men or resources to conquer China Historically that doesn't take much. Having almost no men or resources didn't stop Nurhaci. What was going wrong with the occupation?
- jordanb 2y agoI recommend reading Eri Hotta's Japan 1941: Countdown to Infamy It's a book about how Japan decided to go to war with the united states. It details how China was a quagmire for Japan that was sucking up all the empire's resources. They could conquer land but they couldn't hold it. They could achieve tactical victories against Chiang but could not erode his ability to stay in the field and fight. The story of how the leaders in Tokyo decided to double down on a war they were slowly losing in China, by starting a war they would more quickly and apocalypticly lose against the United States is a fascinating one.
- dr_orpheus 2y agoNever go in against a Sicilian when death (of a spacecraft) is on the line
- BugsJustFindMe 2y agoOnly slightly less well known.
- dr_orpheus 2y agoI spent the last few years building up an immunity to lunar dust powder
- bitwize 2y ago"And guess what? Ground up moon rocks are pure poison. I am deathly ill."
- arccy 2y agowhen gravity is 1/6, a lower centre of gravity might not do as much as you think
- doormatt 2y agoSurely it just needs to be 6 times lower? ;)
- JoeAltmaier 2y agoI think that is entirely irrelevant. It just changes the speed of the topple. Does not affect at all the tendency to tip over?
- mathgeek 2y agoIt's been a while, but IIRC when we assume all other variables as constant, a lower center of mass (a) will decrease the denominator and thus increase the resulting necessary tipping force. Fₜ = (m × g × cos(θ) × b) / (a + b)
- hansvm 2y agoAdding to the sibling @mathgeek's comment, that's only true when there are no outside forces other than gravity. You can see that by taking the counter-argument to its extreme: with gravity of epsilon, even a gentle prod at the top of the object will topple it over.
- ForOldHack 2y agoPhysics 1A: the center of mass does not change. It is irrelevent. The tendancy to tip over is how wide the base is: look at the LEM. Big wide base. Did not tip over. None of them tipped over. They tip over faster on earth due to larger Earth's gravity and mass.
- hansvm 2y agoA big wide base with a center of mass magically very high off the ground would still be tippy though.
- cameldrv 2y ago> Make sure your robotic lunar lander has a low center of gravity. Hmm. https://en.wikipedia.org/wiki/Starship_HLS https://en.wikipedia.org/wiki/Starship_HLS
- ncallaway 2y agoDon't worry, there will be people inside! Oh, wait, hrm...
- jimbokun 2y agoWell that’s a big improvement because the humans can climb out and push the rocket upright again!
- somenameforme 2y agoHey, no mocking Jeb and Bill. They brought many a scientific advancement to humanity.
- ncallaway 2y agoI’m a be honest: Jeb and Bill have done great work for us, but when it comes to getting a tipped over rocket upright… they haven’t always come through for me.
- ceejayoz 2y agoHumans - and the mostly empty space they require - up top. Fuel, engines, and water will be at the bottom. (For practical examples, look at the F9 first stage, or the Starship prototypes they've already tested.)
- dakr 2y agoFuel will be a huge percentage of the weight, and won't that be mostly exhausted after taking off and then doing a powered descent? The center of gravity will move quite a bit upwards.
- croisillon 2y agoTrump could have followed Zelenskyy's example and not let Russia invade his country in winter
- Jun8 2y agoFor (1): except, of course, if you’re the Mongol army. They preferred attacking in the winter (swamps and rivers are frozen so easily passable). https://en.m.wikipedia.org/wiki/Mongol_invasion_of_Kievan_Rus%27 https://en.m.wikipedia.org/wiki/Mongol_invasion_of_Kievan_Ru...
- gcanyon 2y agoWell the Mongols are the exception: https://www.youtube.com/watch?v=PqcVro-3f4I https://www.youtube.com/watch?v=PqcVro-3f4I
- anigbrowl 2y agoI think the fact that they were coming out of rather than heading into the steppe was a major factor.
- dredmorbius 2y agoFamiliar territory / home ground, also well-practiced in foraging within that type of terrain.
- HenryBemis 2y agoYes, this is why they did a similar thing with Ukraine (Feb/everything is frozen - for those who haven't been in frozen countries in the Winter, the earth/ground/dirt (pick your word) becomes hard like cement)).
- bell-cot 2y agoTo paraphrase one of my favorite historians - Every sweeping historical generalization has a "probably doesn't apply to the Monguls" exception. If you don't expect your professor to waste chalk writing this over and over, then he won't grade you down for omitting it from your test answers and term paper.
- chrsig 2y agoThis is a great perspective on pedantry
- adolph 2y ago> 2. Make sure your robotic lunar lander has a low center of gravity. Also, make sure your robotic private spacecraft doesn't land on the edge of a crater. Or partly on a big rock. Or where a rock or ledge is high enough between the legs to reach the rest of the craft.
- ForOldHack 2y agoThanks. I'll be sure to put that in the mission logs. Also do not park next to a space bar.
- deleted 2y ago[deleted]
- somenameforme 2y agoIt's not just the center of gravity. I think people really underestimate how hard landing on the Moon is, because counter-intuitively, the lack of an atmosphere makes things harder, not easier. Landing on Mars (or even Venus (!!) - which is the first other planet we ever landed on) is easy mode by comparison. With the lack of atmosphere is that there is no 'natural' attitude/orientation correction. If you're tilted 5 degrees then you'll stay that way. With an atmosphere drag and aerodynamic forces can be used to ensure a proper orientation. 'Just make sure you come down straight' isn't so easy because when you enter the Moon's 'orbit' (not necessary, speaking colloquially) you're traveling extremely fast. And so to land you need to zero out your horizontal and vertical velocities. You do this by literally turning around the opposite direction and thrusting. And then you need to simultaneously also ensure your vertical velocity stays near zero as you approach the surface. And then finally you need to come down with your vertical velocity at near zero, your horizontal velocity at zero, and perfectly orientated. This is really friggin hard. If you have even a hair of velocity you're going to bounce, skid, and otherwise do nasty things - which is why so many landers end up on their side, if not upside down. And then there's the Moon's surface itself. Come in on an even slightly unlevel terrain and again you're in for a wild ride.
- lou1306 2y agoA bit of Kerbal Space Program really makes you appreciate what an ordeal a satellite landing is. And that is a much simplified setting with e.g., no control lag (even on unmanned crafts), a much closer satellite, etc. Even just designing a craft that will not topple once landed is punishing.
- sfblah 2y agoSo are you saying that landing the lunar lander in 1969 was substantially harder than SpaceX landing its boosters back on Earth?
- weebull 2y agoIn 1969 they used a pilot, and a very good one too. Surveyor 1 in 1966 is a much better comparison.