Jump to content

ARS

Members
  • Posts

    1,291
  • Joined

  • Last visited

Posts posted by ARS

  1. Is it possible for a planet that's formed outside of goldilocks zone (either closer or farther towards the sun compared to earth) to contain Oxygen as one of the main component of it's atmosphere (doesn't have to be at breathable concentration) from the gases that forms the atmosphere of the planet (as in, a planet with oxygen content in it's atmosphere with no plants whatsoever)?

  2. 37 minutes ago, DDE said:

    Usually it's you asking the miltech questions here. Nice role reversal )

    Well, being a graduate from naval engineering, I knew better about ships than tanks or aircraft :)

    37 minutes ago, DDE said:

    Do the power density assumptions and the noise stem from a mechanical turbine? I was thinking about electrical transmission anyway - same as on the French boomers - and with gas-cooled it's possible to switch to a pure MHD with no moving parts.

    If that's the case, then it is possible to obtain similar or higher power density than LBCFR with an added advantage of better cooling due to high-temp gas cooled reactor allowing a larger coolant fraction in the core (due to the low number density of gas coolant)

    37 minutes ago, DDE said:

    Isn't the 'fueled-for-life' concept recent for US submarines?

    The concept of 'fueled-for-life' isn't something new, it's already been around since the idea of putting nuclear reactors on ships, it's just that the nature of LBCFR's operation that makes it's lifespan shorter than other nuclear reactors for submarines. The use of lead has a benefit of higher boiling point, which provides safety advantages as it can cool the reactor efficiently even if it reaches several hundred degrees Celsius above normal operating conditions. However, because lead has a high melting point and a high vapor pressure, it is very difficult to refuel and service a lead cooled reactor. The melting point can be lowered by alloying the lead with bismuth, but lead-bismuth eutectic is highly corrosive to most metals used for structural materials, shortening their lifetime. All of these factors contributes to the reason why Soviets go for 'replace it like battery' approach

  3. 2 hours ago, DDE said:

    What reactor design would I be using to maximize power density? Is PBi-cooled fast reactor still unbeatable? What about high-temp gas-cooled systems?

    For submarine use, Lead-Bismuth cooled fast reactor (LBCFR) is currently still the best option. High-temperature gas cooled system might get power density equal to the LBCFR, but it has more drawbacks that makes it unsuitable for submarines, mainly because of high vibration and noise. While LBCFR that's used on Alfa-Class submarines is also noisy, it should be noted that this noise is only noticeable when operating at top speed (Alfa is one of the fastest submarines). At cruising speed, Alfas weren't any louder than other nuclear sub of her generation. LBCFR's drawbacks when used in submarines includes: inability to be turned off (doing so would solidify the core), cannot be refueled (the entire reactor is replaced like a battery at the end of it's life, which, while more expensive than refueling, in theory it allows quick reactor replacement), and short lifespan (15 years, compared to around 33 years for US submarines)

  4. In theory, if the temperature of surrounding air decreases, does it also decrease the air's absolute humidity? Based from the experiment that I did to determine the fluctuations of absolute humidity of air cooled by ice (until the ice completely melts), it results in this curve: 

    8Ii2yAt.png

    Here's the timeline of the air temperature and relative humidity (from the moment it's cooled inside the cooling box with ice until the ice completely melts), compared with outside the box:

    2OlHGnC.png

     

    X4Fpx7x.png

    I am confused. Realistically speaking, if the temperature drops, then the surrounding air should be condensating (thus, raising the humidity of air and in turn, the curve should point upwards, not downwards), but the data that I obtained results in a completely different value. The data that I obtained from the experiment is temperature and relative humidity, and I'm using that to determine the value of absolute humidity. Am I mistaken the meaning of absolute and relative humidity? Because it's very confusing for me to differentiate between the two. Can someone explain to me how the fluctuations of temperature affect the absolute humidity?

  5. Does the mass of the vehicle affect the G-force strain inflicted on the human body? For example, let's take a 2-ton car and 60-ton tank going at 200km/h (don't ask how the tank got that fast in the first place). If both vehicles suddenly pulled a sharp turn (without flipping over), does the bulk of tank's mass causing more strain on human body compared to the car?

  6. What I'm gonna do? Since there's around 330 million people in US alone, just gather all of the infinite batteries, connect all of them into a a network of cold temperature superconductive power line, which then connects into a field of high-energy supercapacitors to power a mass driver for sending things to space in one shot (idk the power requirements for that, someone please double check it with laptop battery power output x US population before putting the result into railgun formula of lorentz force that provides propulsion for the payload (assume 1 ton), and ignore the rails getting disintegrated during use, we do it for the lolz)

  7. Is there any method to determine nuclear bomb's yield based on the depth of the crater it forms at ground zero? More specifically a crater depth of 600 m (assuming that it forms a perfect hemispherical-shaped crater with a diameter of 1200 m), the blast takes place on ground level, not airburst, location of ground zero is large city, soil condition is typical soil of large cities

  8. Submarines use passive sonar to find other surface ships and submarines by the noise they make. Could a modern-day submarine find wooden age of sail ships on the surface solely by passive sonar? (No periscope, no active sonar, no raising radar mast) Especially considering age of sail ships don't have propellers. Going further, here's some variation:

    1. Age of sail ship does not move, is it more difficult to detect using passive sonar? Assuming the crew also stays quiet and doesn't act like Black Pearl crew. Does moving without propellers (only sails) could make the noise that's high enough to be detected by passive sonar?

    2. Could the modern submarine detect it using active sonar? If it raises the periscope, how visible the submarine is for the age of sail observer when it's observing the age of sail ship from minimum distance for direct visual contact? Assuming the observer only use age of sail era telescope

    3. If the crew of age of sail ship DOES act like black pearl crew, aka being noisy pirates, could it be detected by passive sonar?

  9. Does big-caliber guns still have place in current day naval warfare? Like 200mm caliber guns of heavy cruisers and above, up until battleship-caliber gun of 300mm-400mm, or does the missiles have taken their place in naval warfare that they become insignificant today? What's the maximum caliber of modern naval guns (as in the one intended to be used on ship-to-ship combat) that's in service today?

  10. 2 hours ago, DDE said:

    You're missing the very important part: the entire structure of the ship that transfers the load from the gun's trunnions to the water. Which typically is quite considerable. Without water, the recoil only faces the inertia of the ship itself, requiring much less bracing than a "wet" warship would need; lack of gravity has zero effect.

    The induced rotational moment would, however, be an issue.

    Ah yes I forget about that. Thanks for reminding me

  11. While we're talking about space combat, let's take a look on capital ships. A lot of capital ships in sci-fi has main battery weapons that mirrors naval combat, which isn't surprising since many of the naval terms is applied to spaceflight (port, starboard, hatch, -nauts in astronaut, etc.). Most of these sci-fi main battery guns are either firing physical or energy shots. If we're looking at the one with physical projectiles (shells, railguns, coilguns, mass accelerator), realistically speaking, if such a weapon with capital-ship grade caliber (300mm and above) are mounted on capital ships for space combat, should it also include some mechanism to counteract recoil? Since at that caliber, those cannons are basically reaction engine, and the effect of recoil/ kickback is much more pronounced in space, probably enough to rip the whole turret off of it's mounting when they are fired full salvo (on earth, cannon recoil are absorbed by water on the opposite side of the ship). I am thinking a counter-thrusters that'll be fired at the same time the cannon is fired (one scene on Expelled From Paradise is a good example, firing giant linear cannon in orbit requires all of the back thrusters to fire in unison at full power for a few miliseconds the moment the cannon is fired), or reinforcing the barbette of the turret in order to handle the recoil, or compensators with reciprocating barrel for minimizing recoil

  12. 1 hour ago, Spacescifi said:

    Which do you think is superior, given similar tech for both opponents?

    If one opponent nation went all in for mass produced cheap space vehicles, would that not beat one that produced a limited number of heavily armed spacecraft?

    Scenario is a space battle only, from deep interplanetary space to orbital battle.

    No planetary bonbardment

    This is basically a repeat of a Soviet vs German in world war 2, but in space, which is more like Kushan vs Kadeshi in Homeworld. The first thing is, depending on what you describe as superior, it could mean superior general quality (better guns, armor, thrusters), in which quantity will win by overwhelming it or specific superiority, such as being superior in dealing with swarm attacks (multiguns, multi-target tracking) in which quality will win.

    I'll reiterate the battle between Kushan and Kadeshi in Homeworld, which is basically this situation. The Kadeshi uses swarms of cheap strike fighters to overwhelm the Kushan, they are very fast and armed with rapid fire energy weapon that can tear off opposing strike fighters with ease, and they outnumber Kushan by a factor of 10. However, their small size and cheap nature also means they have practically nothing else, so they are only good against strike fighters, and need time to destroy anything corvette-sized or larger, which is where their multibeam frigate comes in, appearing in much fewer numbers but can destroy capital ships.

    Now this scenario depends on the player how it turns out. If you're a newbie and think that their strike fighters can't reliably damage anything larger than corvette, and focus on building that, you'll definitely lose since Kadeshi can pump out fighters faster than you can produce frigate-class ship or larger. By the time you attempt to brute force your way by forcing your fleet to push through the swarm, you'll either:

    1. Managed to destroy their mothership, at the cost of heavy damage to your fleet and immense resource drain on your side

    2. Gets obliterated and cannot build replacement forces in time to defend your mothership before being overwhelmed

    That's the definition of when it's just "superior", which is not very cost effective in terms of resources for Kushan. Now let's see the "specific superior". Experienced players will instantly knows that fighting the swarm is futile, and going straight to their mothership is risky. In general, there are 2 main intended ways of completing this mission:

    1. Players will notice that Kadeshi swarm fighters still needs refueling (you can't fire that breakneck thrusters forever) and noticed that they always come in squadrons that accompany a fuel tanker ship. Destroying or capturing this ship will cripple several squadrons at once as they floats aimlessly in space once their fuel is depleted, making it much easier to push through into their mothership

    2. Alternatively, if player pays attention to the battle chatter as it drags long enough they'll notice that Kushan has finished enemy analysis to build a multigun corvette, which is hard to destroy by Kadeshi swarm fighters and posses enough guns to multi target several fighters at once. This corvette allows you to tear your way through their swarm

    While their rarer but much more powerful multi beam frigate poses credible threat to your mothership, and sometimes hard to find (which is neat, because it reflects their doctrine, overwhelming their enemies with fighters while the frigate moves to kill the mothership, which is why they disguised the frigate to look like their fighters, albeit slightly larger and slower, which means they can't afford to lose it, since it's limited in number and isn't spammable, so they had to make it hard for the enemy to find it amidst their swarm fighters), savvy commander can spot them easily not by visual, but by movement (they fly straight instead of doing maneuvers) and either destroy it before it's reaching the mothership or hijack it for their own use

    This is just an example of quantity vs quality in space battle. In the end it's not only numbers of units that matters, but also the strategic decision of cunning field commanders that makes the day

  13. Is it possible for human to survive atmospheric reentry in free-fall? Most manned reentry capsule in use has blunt body shape with heat shield, with the crew inside seated in specific position in order for them to survive the massive G-force during reentry. Now here's the scenario:

    1. Assume that the person is wearing a space suit/ space marine/ power armor/ whatever that's strong enough to survive atmospheric reentry

    2. There's no joint lock on the suit, the limbs are free to move during the reentry. There's no main thrusters in the suit, but there's RCS thrusters like those found in the space suit

    3. There's parachute and airbrake flaps that could be used once in-atmosphere at safe altitude and velocity

    Now assuming that this guy starts at suborbital trajectory and just about to enter the atmosphere, assuming this guy only have this suit and nothing else (reentry angle at 45°), would it be better to position his body with arms tucked back like those in skydiving? Or spread his arms and legs like flying squirrel? What's the effect of G-force from reentry on human body on positions like that, especially when not seated like those in proper reentry capsules

    Oh and the last, this is unrelated, but assuming we have the suit like this, does the KSP stunt of "strap the heat shield on your back and pray to god you'll make it through" possible to do in real life?

  14. So... imagine a scenario like this:

    Country A and Country B is separated by ocean. They are in conflict. Country B invades country A, ending with nukes that pretty much renders country A no longer existed, the last of the people on that country gets vaporized. Unfortunately, country A has SSBN fleet hidden in the ocean, with enough nukes to render country B no longer exist too. Assuming that:

    1. Country B has no knowledge that country A has SSBN, and both countries has no anti ballistic missile technology, how much of a threat that SSBN presents? (Even if it's just a single sub) And if it does wipes the country B, following the counterattack by dead man's protocol of non-existent government, what's the  status of the sub's crew in the eyes of other countries? Hunted by the rest of the world? Does nothing since it's the dead man's protocol of a fallen nation (and well deserved revenge)? Or judged as war criminal? Or what?

    2. In real life, if there's a scenario like this, after the war is over, assuming they didn't fire the nukes, and the war ends with intervention from third party, considering that the crew of the sub no longer have a country, where they'll go? Does the sub belongs to them, or they hand it over to allied country or what? Especially considering that they have nowhere to return, yet still possess SSBN's worth of nukes

  15. I have 2 questions:

    1. If we build a hypersonic aircraft with specially made cockpit that allows full liquid immersion with breathable liquid, does it allows the pilot to withstand more G-force?

    2. Is it possible to build a high altitude glider that glides infinitely? Aka it doesn't use engines at all and only relying on adjusting the control surfaces to glide forever

×
×
  • Create New...