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ARS

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Everything posted by ARS

  1. Since they're green... Soylent green
  2. Interesting. Does using it different (technical-wise) compared to using regular active sonar? Considering the sonar source and receiver is not in the same sub?
  3. Could submarine share targeting data with each other's sonar? Like when two submarines operate together to hunt enemy sub and they know each other's position, if for example, sub A activate sonar pings (and sub B knows that sub A is about to do active pinging), could sub B use A's echo to locate the enemy sub?
  4. So... There's something that makes me curious. During WW2, armor piercing bombs are in widespread use (whether it's actual bomb purpose built for that or AP shell repurposed into a bomb), mainly for attacking hardened targets like capital ships or hardened bunkers. Now, since the bomb is designed to penetrate the target before exploding inside, the bomb relied on kinetic energy from terminal velocity after it's being dropped to achieve penetration. Since terminal velocity is the highest velocity attained by a falling object, assuming the bomb is dropped from the height sufficient enough to achieve maximum terminal velocity purely by falling, does that means bombing from higher altitude than that does no increase in penetration capability? (since the terminal velocity remains the same)
  5. What do you guys think about designing a robot with human-like arm so it could hold weapons? In many sci-fi works, whether it's cyberpunk, futuristic or post-apocalyptic setting, we often see robotic combatants, from small humanoid-sized ones holding infantry-grade firearms (ex: B1 battle droid (Star Wars)) to gigantic ones using upscaled arsenal (ex: Titans (Titanfall)). Compared to simply just forget about human hands and have the weapon being the arm itself (ex: Mechwarrior). On one hand, human-like hands allows the machine to do what human hands could, except in larger scale, offers versatility by allowing it to use different types of weapons and can be used to do more mundane tasks (lifting a person, getting up when knocked over, etc.). On the other hand, a weapon arm is much more simple to build, can get bigger guns and generally easier to maintain Or maybe a middle ground by having a hybrid arm-weapon (lEx: some of Mechwarrior mechs or Gipsy Danger (Pacific Rim))
  6. The landing area is in constant view of the pilot throughout the entire descent to landing. Aircraft descend in a nose down pitch attitude. During the landing itself, the pilot is looking down the runway instead of at it, before the aircraft is pitched nose up just before the touchdown. Any other time during the flight, it is much more important to see what is ahead and above you than it is to see what’s below you (at an appropriate altitude). Where seeing under the fuselage would be useful in some situation, it does not give any significant benefit for the pilot to worth the hassle WW2 era bombers need glass nose for both navigator and gunner. Bombing in WW2 was highly dependent upon visual references due to the lack of GPS guidance. For navigators, bombers need to find navigation references during the run up to what the USAAF termed the “initial point” or the start of the bomb run proper. As anyone who has looked for a ground reference from the air knows, just finding the initial point alone could be challenging. The high visibility offered by the large glass nose was necessary - even if the navigation was accurate (even more so during night bombing). For nose gunners, when defending against head-on pass the gunners could only shoot back during very brief interval when the target is in range. This is both terrifying and difficult, hence why the extensive view of the nose turret is important to spot the enemy planes earlier before they come in range. Once radar technology and GPS for navigation has improved, and defense turrets no longer relevant in modern era, the glass nose becomes obsolete, replaced by much more capable radar and avionics instead of mk1 eyeball Think of it like driving a car. Like an airplane, your car on the highway is moving forward at a great rate of speed. Having a view of what is below the car would allow you to see the pothole you are running over as you are running over it. That view is not very useful compare to the ability to see the pothole well down the road before you ever reach it. That is why cars don’t need transparent floors. Any speed above a fast walk would render it useless
  7. Interesting... Does this also applicable for a situation where there's a sudden tumbling of the object that causes significantly increased drag? (for example, something breaks during reentry and causing the shuttle to tumble in such a way that there are now greater surface area being exposed to drag)
  8. Is there a formula to calculate reentry heating temperature based on object velocity? (assuming the object in question is Space Shuttle, nose-high 40 degree reentry angle and it entered from geostationary orbit)
  9. Yeah, I played Anno 2205 before, and the first time I saw how they gather He3 I'm like... what? seriously?
  10. There is very few hydrogen on the Moon, mainly under the form of some frozen ice in some cold places. There is a natural proportion of deuterium in hydrogen, probably different than Earth’s hydrogen. But the overal quantities are very small Tritium is an unstable isotope of hydrogen, with a short half-life. So that it can exist in nature only when there is an active production process. Save cosmic rays, there is no such process on the Moon, so that the tritium quantities may be counted in atoms. Helium3 was formed in the Big Bang, and it appears from the decay of tritium. It represents a small fraction of natural helium, itself considerably enriched in Helium4 from the radioactivity of rocks. So to start with, Helium in general is very rare on the Moon, and much rarer on the surface. There may be underground pockets of it. But this would require us to find them, and dig hundreds of kilometres down the moon's crust, only for small quantities, and much smaller quantities of Helium3 So I guess catching the solar wind with huge electrostatic traps on orbital satellite platform would be more feasible economically that crushing billions tons of Lunar soil just to get trace amount of it
  11. So does that mean it's only good for low-mass spacecraft?
  12. Is it more efficient to use cold gas thrusters for RCS purpose than using hypergolic rocket fuel? Since cold gas thruster has lower thrust than combustive rocket engines, they are not very good as main propulsion purpose, but could be useful for orienting/ maneuvering purpose Using liquefied gases, the gas pressure output will also remain relatively constant as the liquid gas volatilizes during use, on top of simplified fuel lines since instead of using two tanks of hypergolic fuel, the space onboard the spacecraft can instead accomodate one large tank of liquified gas
  13. Deep sea trench. Location forgot, I just wandered on the seabed with my sub
  14. When you wanna takeoff your new aircraft, but forgot that it's too wide and hit the fuel tanks on the side of the runway
  15. IIRC, the Apollo command module is directly controlling the service module. As soon as the connection is cut off, there's no way to control the service module. The extra fuel needed to make stable orbit is more likely to hamper the actual Lunar mission Also, I'm back
  16. This is some of the space stations that I've made long time ago. Many have the capability to alter their orbit and even goes between celestial bodies to set it as the next celestial body they orbit, allowing flexible placements for interplanetary hub (although unlike spacecraft and regular rockets, the procedure for doing burn is much more complex due to many preparations needed. They can't land on planetary bodies and any resources needed for burns must be brought from external sources or generated in orbit. The burn itself should be done in several instances, as doing one long burn in a single instance could overstress the joint connections between modules)
  17. If you're a mad supervillain with a goal to destroy the world, what's the cheapest way to do it using existing technology? (doesn't have to blow up the whole planet, just rendering it uninhabitable is enough)
  18. So I recently saw a review on Youtube about a movie "The Wandering Earth". In case you don't know, it's a science fiction movie with 'science' part being so bad, it makes "The Core" science looks like "The Expanse". Let's get with the premise in a nutshell: The sun is expanding, we need to save humanity, we built thousands of city- sized rocket engines on Earth's surface and fly the damn planet like a spaceship straight to Proxima Centauri by using Jupiter to do gravity assist, which then goes haywire when one of the engine shuts down, leaving the planet with insufficient thrust and now it's being pulled into Jupiter, and the only way to save the humanity is by igniting Jupiter's atmosphere so the shockwave would throw the Earth out of Jupiter's gravity well But that's not what I'm gonna ask here. Understandably, the movie is being mocked to death, mainly from being ignorant with so many laws of basic physics, astronomy and orbital mechanics. Most of the critics tend to point out about how insane the idea of putting rocket engines on Earth's surface is (and how it would mess up with Earth's geology and atmosphere), but one comment struck my interest: So it's basically using Moon's gravity interacting with Earth, pulling at each other, and use that as a means of manipulating Earth's trajectory. Now I know the scale involved here (especially in terms of engineering) is so mind-bogglingly large, but assuming the moon's orbit could be manipulated (and you really don't care about it's effects on Earth's inhabitants), is this idea makes sense (In terms of physics)? I don't ask "is this possible", I ask "is this (in theory) possible?"
  19. As steady stream of radiation and particles continuously emitted from Black Hole as Hawking radiation, there would be a point in time where black hole's mass loss would eventually caused it to cease to exist and die. However, as black holes also moves through universe, assuming it keeps feeding from stars and planets (devouring their mass), is it theoretically possible for black hole's lifetime being continuously extended? (at least until there's nothing left to devour)
  20. Just wanna ask if you can detect other sub by using that method (active ping far away from the sub)
  21. But the problem is, the defending sub already knew the location of the emitter and already expect a return when they trigger the ping. The defender knew where the location of the emitters, where to look at the moment they trigger a particular ping as well as the underwater topography of the area they defend. On the other hand, the attacking sub is clueless and has no idea about the pingers' placement or even if there's such a thing in the area in the first place and expect there's only defending sub in the area. They are not expecting an active ping, much less a return from pingers they don't even know the location about (they might even mistake a ping from a buoy as defending sub's ping)
  22. Yes, that's what I mean: detecting a target underwater using active ping, except you're not the one doing the ping, but preplaced active pingers placed beforehand (and you already know the locations)
  23. Question: Is it possible for a submarine to do standoff active sonar search by using separate sonar emitters outside of the ship (as in, in the form of buoys, underwater emitters, etc.). Let's say for example submarine A is defending an area, and it already pre-place these emitters around. Then, enemy submarine B is entering A's patrol area. If A knows that B is entering the area, could A detect B simply by staying on passive sonar while periodically pinging the active sonars from the buoys and listening to the echoes to locate B? (could either do sonar pings from the buoys one-by-one or several of them at once)
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