-Velocity-

Yea, I have used empty fuel tanks before. But they are not very durable... go above like 20 m/s through water, and they're destroyed. So you need a VTOL aircraft in order to make use of them.

Yes, but it wouldn't deposit ALL of its energy if it re-escaped into space. It might actually retain most of its energy, and only lose like a tenth of it to Earth's atmosphere, if this hypothetical super-durable asteroid were large enough. Still, 1/10th of 100,000,000 atomic bombs is still a lot Still, it's never gonna happen.

You might have to slam the Moon into Venus at the same time it approaches Earth. That might slow down/speed up Venus enough for Earth and Venus to capture each other... Considering that this requires just about the power of God, I don't imagine it will ever be done... and I agree that any civilization that would be capable of this probably wouldn't need a planet to live on in the first place. Unless they become so powerful that they do it just because they can...

I always have part-clipping enabled, but I never use it to do anything blatant, like putting parts very far inside each other. Most often, I have to turn on part clipping simply because the game won't let me put parts in places where there is *nothing at all* blocking the parts from being placed. The VAB is just buggy and my parts are "clipping" with something that is non-existent.

That's OK. I first read about Earth tidally locking with the Moon probably back in like, 1999ish in an article by Bob Berman in Astronomy magazine, and he was claiming that it would actually happen. (He even went further, claiming that after tidal locking had occurred, the process would begin to reverse as the Earth slowly tried to tidally lock with the Sun, and that eventually, the Moon would crash into Earth!). So, not everything you read is true. Perhaps with a long enough time scale, Bob Berman would be proven right (as long as the Moon doesn't escape first as SargeRho suggested could happen), BUT our Sun is not a red dwarf. I hear that in some textbooks, they STILL claim that glass slowly and measurably flows at room temperature, and that's why old stained glass windows are thicker at the bottom- even though this has been repeatedly shown to be false!!! Anyway, this brings to mind an idea for a thread we could start- "Common Science Myths". We could cover the flowing glass myth, the myth that airplane wings get their lift from Bernoulli's principle, the Earth-Moon tidal locking, etc. It would be interesting to see how many of them there are, and what they are.

Interesting- so the Moon would have to move so far away from Earth to absorb enough rotational energy to tidally lock that it would be beyond Earth's Hill sphere? I haven't found the scientific source, but this article matches what I remember hearing before- that geologists had studied rocks laid down in tidal areas and determined that around 2 billion years ago, the days were only 18 hours long. If that represented a linear change- if the Moon were NOT actually moving further away from the Earth- it would mean that the day lengthens by 3 hours every 1 billion years. In actuality, the Moon is getting further away as it absorbs Earth's rotational angular momentum, so the effect is getting weaker and weaker as time goes by. But, just assuming that it WASN'T getting weaker and weaker, then it would still take around (27.3*24 - 24)/3 = 210 BILLION YEARS for the Earth to tidally lock with the Moon. As a more realistic number, I think I remember reading many years ago that it would take well over a trillion years for the Earth to tidally lock with the Moon. But, this is the first time I ever remember hearing that the Moon would actually escape from Earth before it would tidally lock. I'll see if I can look into it further when I get the chance. If it turns out to be true, thank you very much SargeRho for teaching me something new! Not like it's actually useful information though, since it will (probably) not happen anyway (as the Earth is currently predicted to be consumed by the red giant Sun)

Incorrect. I've heard that myth before, but the fact is that the length of time it would take to tidally lock the Earth to the Moon is FAR beyond the lifetime of the Sun. So the Earth will be destroyed by the red giant Sun long, long long before it ever gets a chance to tidally lock with the Moon.

It's all a silly, unrealistic discussion. Venus will simply never be moved in its orbit, because of Earth. Moving Venus out to a point where it no longer receives too much solar radiation would destabilize the orbits of both Earth AND Venus. Earth, however, could be reasonably moved outward a bit in its orbit, if there is anyone around in 500 million or a billion years who is interested in keeping Earth habitable a bit longer. (If there is still a flourishing biosphere on Earth at that time, I think there will be someone around, because over the last few hundred million years, the overall trend has been that animals have continuously gotten smarter and smarter. No species, at least that I know of, have evolved towards greater stupidity.) As many people already know, the Sun is slowly brightening, and that will probably render Earth uninhabitable before other vital processes like plate tectonics and the carbon cycle are "scheduled" to shut down. So maybe if you "just" move Earth outward by another 5-10 million km, you can extend the habitability of Earth by like, a billion years.

No, ion engines are now terribly overpowered. IRL, ion engines (moreso related technologies like VASIMIR that the KSP ion engines actually more closely resemble) are only viable for a moderate or high acceleration propulsion plant of a large interplanetary spacecraft IF you pair them with nuclear reactors. Now, in KSP, they are viable as a high thrust propulsion plant of an interplanetary manned spacecraft using just photovoltaic panels! Furthermore, as Jouni notes above, it's now possible to use them as LANDER engine. That is going WAY too far. With the previous ion engines, it was similar to real life- **if you got a parts pack that included a nuclear reactor**- then ion engines suddenly became a viable choice for high impulse, large spacecraft propulsion. They were not a viable choice for a lander engine because any electrical system that provided enough power for them would be too heavy to land. Previously in KSP, with only solar panels, you could only use them to propel relatively small spacecraft, or get extremely slow accelerations with larger spacecraft. This is correct to real life. Not that the previous ion engines were perfect- they worked in an atmosphere, which led to ridiculous things like ion-engine propelled aircraft. IRL, ion engines *REQUIRE* a hard vacuum to operate! Furthermore, the utility of the previous ion engines was greatly reduced by the lack of a nuclear reactor part. IRL, we have been launching nuclear fission reactors into space since the 1960s (the U.S. launched one, the Soviets launched like a dozen). The CORRECT way to fix this problem was to: 1) Provide a nuclear reactor part (really, a heating/cooling system would also need to be modeled, as IRL, nuclear reactors in space require large heat radiator panels. To do work, you have to have a heat difference, basic thermodynamics...) 2) Provide larger, higher thrust ion engines 3) Provide large xenon tanks. The INCORRECT way to fix the ion engines is to do what Squad did in fact do- reduce the required power hugely, and increase the thrust hugely. Now, we're going to see ridiculous creations like ion-powered landers (no ion engine or even higher-thrust related technology could EVER land a spacecraft on another body, except maybe on a ***SMALL*** asteroid), and a huge surge of ion-powered aircraft. (The correct way to enable electric-powered aircraft would be to add an electric motor-driven propeller part). Not that *I* truly care how others play the game, but now I have to go back and mod the ion engines back to a believable balance level. And if you DO care about game balance and are unwilling to rebalance the stock parts yourself, God forbid Squad ever implements larger xenon tanks and nuclear reactors- then NO ONE in their right mind would ever use an LV-N again. So while I DO understand Squad's desire- make the ion engine a viable option- the solution to that is to add additional parts, NOT make the ion engine ridiculously overpowered, enabling it to be used in situations it can never be used in IRL.

The new ion engine provides about 700 times more thrust than the most powerful ion engine ever created (2000 N in KSP vs. 3 N IRL)!!! Even though the older ion engines were still vastly overpowered, their balance was fine IF Squad had JUST provided a nuclear reactor part, and had they provided larger ion engines and larger, realistic-capacity xenon fuel tanks (a Jumbo 64 fuel tank, filled with liquid xenon instead of regular rocket fuel, would hold around 900,000 (ish) units of xenon fuel- 90 tons! Liquid xenon is around 3X heavier than rocket fuel).

Why? People laughed at the idea of flying to the Moon, and then, we did it. 80% nitrogen, 20% oxygen is a LIFTING gas on Venus: CO2 = molecular weight: 12*2 + 16 = 40 80% N2 + 20% O2 (roughly the composition of air) = avg molecular weight: 0.8*(14*2) + 0.2*(16*2) = 28.8. So you only need to fill your habitat with breathable air and it will float. If there is not breathable air in it, then everyone is dead anyway. The hard part of it is that there are not accessible raw materials to build a habitat out of on Venus. That might eventually be possible to overcome, although that's unlikely for a long time. As to the rest of your ideas, they are not feasible. Yes, you could move Venus if you slammed ENOUGH rocks into it. However, if you're going to use each rock only once, I doubt there are enough asteroids in the entire solar system to move Venus' orbit enough to make it habitable. The total combined mass of all the asteroids is VERY SMALL. For example, the entire combined mass of the asteroid belt is only 4% of the mass of the Moon. However, if you re-use your asteroids, then you can move Venus over a long enough period. If you send enough asteroids past Venus, using Venus' gravity to gravitationally brake the asteroids into lower orbits, you WILL eventually boost Venus to a significantly higher orbit. Your problems do not end there, though. First off, Venus is well very far outside the habitable zone. Earth is inside the habitable zone, near the inner edge. So what are you going to do with Earth? You'd have to move Earth, too. I doubt that Sol's habitable zone is large enough to fit two Earth mass planets in stable orbits, but I could be wrong. Even if it is possible to fit two plants, your problems are more than doubled, because not only will you need to move two planets, not one, but you'll radically change Earth's environment, too. Oh and finally, Venus lacks a magnetic field, and it has an extremely slow, retrograde spin... not ideal. By far, the best way to terraform Venus is to use solar shades to reduce the apparent brightness of the Sun. This effectively allows you to ignore habitable zone concerns and make the temperature on Venus whatever you desire it to be, without having to move it at all. And considering that your solar shades probably only need to be a few dozen microns thick (if that!), it will take very little physical matter and resources (at least compared to some huge asteroid redirecting scheme) to affect this change.

Yes, if was ACTUALLY drilling, but no, because in REALITY a melt-probe melts its way through, and there is no hole because the hole gets filled in behind it with re-frozen water. So there is nothing to "shoot" the probe up into.

Well, if it's true, then... FINALLY SO damn sick of not having anything but quick save, especially with all the weird bugs in this game. I can't count the number of times I've pressed quick save, only to discover in the minutes that followed that, like, the Kraken had disconnected parts of my ship and now my whole mission was totally hosed because there was no save system to speak of and I forgot to backup my files I understand that there are going to be bugs in the game as it is a major W.I.P., but not having a save system to help alleviate the pain was inexcusable. Have a small file system with the ability to have multiple saves is NOT a hard thing to add.

Wouldn't the hole freeze back in behind you? You're not actually drilling a hole and removing the material off to the side; you're melting your way through, and leaving a cable behind you. So your question would be moot. That said, if you removed the ice and left an actual drill hole, I believe the answer to your question would be that the pressure at the bottom of the hole needs to equal the pressure of the sea you're drilling into. Well, that much is obvious. So, to equalize the pressure, I believe that the ratio between the length of the hole that is flooded vs. the total length of the hole will equal the ratio of the density of ice over the density of water. So, if the hole is 40 km deep and ice is 0.8 times as dense as the ocean water, then the water will only rise up 0.8*40 km = 32 km- stopping 8 km short of the surface. A simple way to visualize why I think this is the correct answer is to imagine a straight sided hole of uniform width. To equalize the pressure, the weight of the water filling the hole must equal the weight of the ice that was removed to make the hole in the first place. I think. Someone who is more familiar with fluid dynamics correct me if I am wrong.

No, the chances of that are small enough to be ignored. However, there is a chance that the detonation circuits could operate correctly, but just at the incorrect time. This would occur through extreme human incompetence, carelessness, or poor engineering.- like, maybe they accidentally left a safety switch in the "arm" position, maybe they accidentally dropped the weapon, and maybe some other safety switch was designed incorrectly. There are rumors (confirmed with recently declassified documents) that something like this nearly DID happen with a multi-megaton weapon over North Carolina back in 1961- http://www.theguardian.com/world/2013/sep/27/atomic-bomb-north-carolina-video An excerpt - All that said, this applies to implosion-type nuclear weapons. Implosion-type weapons are not going to detonate unless exactly-timed signals are delivered to the detonators of the explosive lenses. So you could blow up implosion-type nuclear weapons without fear of them detonating. However, nuclear weapons that assemble a supercritical mass that is supercritical at regular pressures (like the gun-type design used in the Little Boy bomb) are very unsafe and COULD detonate if they were subjected to an explosive blast. Modern nuclear powers do not use any of these weapons, however.

If you're using air pressure, you likely can't just have a plunger on the back that is not sealed against the inside of the barrel. Otherwise, the pressures on the back of the plunger will quickly equalize with those in front, and the plunger will not move. What you might want to try is placing something (like a thin, breakable and breathable membrane) across the muzzle of the paint ball gun. You would place the ignition switch of the rocket on the NOSE of the rocket. It would be some kind of latched push-button. When the nose of the rocket strikes the membrane, it latches the switch closed. As the rocket continues out the tube, it breaks the membrane, and continues on its way, igniting the engine shortly thereafter. The membrane must be breathable, otherwise the air pressure ahead of the rocket could break it before the rocket gets there. Instead of a membrane, you could try a plastic cap with a bunch of holes in it. It fits snugly over the end of the barrel, snugly enough to stay on until the nose of the rocket strikes it. Also, tie a string to it, and tie the other end of the string to your gun. This way, you can easily recover the cap after firing. An issue with the plastic cap however is the possibility it could get caught around the nose of your rocket and wrench the rocket into a spin. To solve this, instead of a cap, you could use simple some kind of plastic plate that locks in place over the barrel and just levers/flips back after the rocket strikes it. Another safety issue is pushing the rocket down the barrel when the ignition switch is on the front. But this whole thing is highly unsafe. Just makes sure you don't LOOK down the barrel while your pushing the rocket down it. Another idea I head was to use a photoresistor or photodiode as a sensor to detect when the rocket was outside of the dark barrel and into the brighter outside. You could even use an infrared photodiode that is only triggered by an array of IR LEDs at the end of your barrel (through bright sunlight would probably also be sufficient). But these ideas all require more electronics know-how than you probably possess. At the very least, the photoresistor/photodiode would need to be in a circuit that feeds a current/voltage into the base/gate of a BJT/MOSFET, with the transistor being used as a switch that conducts the comparatively high current required to ignite the igniter. If you're not an electrical engineer or electronics hobbyist, this stuff is probably beyond you.

I started equipping my still-unnamed "Large Ion Cruiser" for a mission to the Jool system (I'll probably visit Duna and Dres too). All the panels at the back are the reactor section (10 nuclear reactors with total charge generation of 3000 charge units/sec... need them for powering the ion engines...).

I had a big heavy lifter (maybe about 3000 tons) that could deliver about 500 to maybe 700 tons to LKO. Unfortunately, 0.23 brought part incompatibilities that broke it. I replaced it with a smaller but MUCH simpler rocket that masses like 2200 tons (sans payload), and can deliver 400 tons to a 250 km X 250 km orbit. I don't really care that the payload is smaller, as the new rocket has less than HALF the parts as the old one (1600 parts with the old rocket vs. only 750 with the new one), and most of my big payloads in the past were like 70% fuel by mass. Now that we can launch empty fuel tanks, I can send up spacecraft that will be like 2000 tons when fully fueled, in a single launch! EDIT: And this was why I gave up on the super-big rockets, and am sticking with heavy lifters <= 3000 tons. Here is my attempt to make a 5000 ton heavy lift rocket (design goal- ~1000 tons to LKO). I DID make it stop exploding, but I could never get the fuel to flow correctly, so it would always get out of balance and crash. I really, REALLY hate the fuel flow system in KSP. If we ever get a better fuel flow system, it will be much, much easier to build asparagus-staged rockets. Come to think of it though, I could always make a custom fuel tank mod. All I would need to do is like, rescale the largest KW rocketry or Novapunch fuel tanks by a factor of 2, increasing their volume by 8, and increasing their empty mass by 8. What limits me most is the small sizes of even the biggest fuel tanks available in KW rocketry and Novapunch. It's really tough to make an asparagus-staged rocket where there are lots and lots of fuel tanks in each asparagus stage. The fuel just refuses to flow in an asparagus fashion.

How will the rocket maintain stable flight? You need some kind of fins or sticks off the back to keep it going straight. Otherwise, it could just turn around and hit you in the face. If it's going a few hundred miles per hour and has a pointy tip, that could be very, very bad for you. What you need to do is first test your rocket design external to the gun, and make sure the design of the rocket itself is sound, and that it flies straight. The easiest way to test the stability of a rocket design is to tie the rocket on a string so that it's balanced about the point where it is tied. Then, spin the rocket around your head rapidly. If the rocket is stable, it will point into the direction of its spin. Next, you should test the rocket in the gun without igniting the engine, several times. Make sure that the rocket maintains a straight flight after leaving the barrel!!!! Only last should you combine the two... still not a safe idea though. Anyway, as far as engine ignition, why not go simple? Maybe just use a fuse. Light the fuse, drop the rocket down the barrel, and then fire. If you time it right, then the engine will ignite while the rocket is still in the air. Just make sure to point it UP, so that the rocket is still pointing up when the engine ignites.

Yes and no. Yes, if you're only willing to accept an efficient explosion. You wouldn't want an inefficient bomb if you're trying to propel a spacecraft. And no, not if you're willing to accept a low efficiency. You can make a nuclear weapon "fizzle" more easily than you can make it explode efficiently with a high yield, just ask North Korea (this is especially true if you're using implosion-type weapons). But at any specific efficiency, you do have a minimum practical yield you can achieve. This is caused by the fact that everything has to be kicked off by a supercritical mass of plutonium 239 or uranium 235. There are ways to reduce that critical mass (such as explosive compression, neutron reflectors, or a combination of the two), but those can only take you so far. At some point, if you desire a lower yield, you'll have to accept a lower efficiency. Notice I ignore the hydrogen bomb in this discussion. That is because the hydrogen bomb has to be triggered by a fission weapon. Secondly, many (most?) nuclear weapons that incorporate nuclear fusion- thermonuclear weapons- get most of their energy from fission anyway, as they work by using the neutrons produced by fusion to boost the efficiency of the fission reactions.

Umm... you have no idea what you are talking about. I've actually worked on thermal imaging in real life for the US Army. Only black bodies emit black body radiation by definition. Now, while a lot of things approach black body emission and are effectively black bodies, on a whole, treating an entire spacecraft as a black body is stupid. By cooling some sections of a spacecraft, a spacecraft can anisotropically emit its heat, so that in some directions it looks a lot cooler than its overall average temperature and heat production would otherwise force it to be. That is the whole idea behind the thermal panels idea. Making your spacecraft the temperature of the background is the best way to hide it in the infrared. If you emit nothing, then you'd be slightly more visible, as you would appear to be a shadow against a brighter background. However, the background is so faint in space that emitting nothing at all (being at absolute zero) would be almost as good as being at like, 4 kelvins. However, being at 0 degrees K is ALOT harder than being at like, 4 degrees K, so your idea to "emit nothing at all" would not ever be done, because it is much harder and actually worse than matching the background apparent temperature. One problem with hiding in space would be when you occulted a bright star from the point of view of the enemy, but that's where the high velocities and long distances of space come to your advantage. Your spacecraft will be very distant from the enemy, and the chances of blocking a bright point source will be near to nil.

Incorrect. While your science is correct in terms of black bodies, you are forgetting that not everything is a black body. So you are incorrect, because you are thinking far too isotropically. If you know what direction an enemy observer will be observing you from, then you can hide yourself using a thermal shade/panel. What you do to hide is deploy some large, flat panel on the side of your spacecraft that faces the enemy. The side of the panel facing the enemy is cooled to the temperature of the space background. The other side of the panel is not temperature controlled. So now, in the direction that the enemy lies, you are the same temperature as the space background, and you are invisible to infrared detection. In other directions, you are whatever temperature to need to be to reach thermal equilibrium, but you don't care, because the enemy isn't there to see you. You could make the panel radar stealthy too, so you couldn't be easily seen with radar, either. You could deploy multiple panels too, and make yourself stealthy in multiple directions. Heck, it is probably possible to beam all your thermal energy out in one narrow direction, and be stealthy from almost all, or at least most, observation directions.

What kind of war? Limited? Total war?- are civilians a target? Is Mars terraformed or not? Are the asteroid inhabitants tied to a specific rock or can they easily move? Your question is far too broad to know the answer to. The total war scenario is perhaps the easiest to answer though. In a total war, the asteroid inhabitants would have an enormous advantage, so big that Mars would be doomed and it would be insane to start a war, especially if Mars is terraformed and the Martian populace is dependent on a stable environment to survive. The asteroid folks could redirect swarms of rocks into Mars collisions. They only have one target to hit, and it's a big one. The asteroidal inhabitants have a huge supply of heavy elements (read "nuclear weapons") too, as they are living on undifferentiated bodies. Meanwhile, the Martians could not easily retaliate against the asteroidal inhabitants, as there would be too many civilian asteroidal targets, and each one would be completely or mostly self-sustaining. The asteriod inhabitants could possibly not even be tied to specific rocks, making them even harder to wipe out. So in a total war of a planet against a large decentralized group of space settlers, the planet would be completely screwed.

Why are there people who put more than one nuke on their ships? If you're actually wondering this, then I've got a question for you- Why are there people who think I want to wait 14 hours to make a 2000 m/s delta-V change while a single LV-N producing 60kN of thrust accelerates my 1500+ ton interplanetary supertanker at 0.04 m/s^2 (0.004 g)? Oh and, 14 hours would be a best-case scenario; in reality, the sim slows down to 1/3 speed so that it would really take around 2 days real time to make just a 2000 m/s delta-V change. No thanks. I just put four NovaPunch 2.5 meter NTRs (1.2 MN, acceleration = 0.8 m/s^2). It can still take hours to do some maneuvers, but at least it's doable. I can go read a book or work on a paper or programming project while making my burn to whatever planet needs more fuel, a fresh crew, and new equipment

To "solve" the asparagus center section problem, I've actually used some extra engine "nacelles" that attach to the top of the asparagus center section, and are above the other asparagus sections. When the last of the side sections are jettisoned, the extra engine nacelles on the center section start firing. On the pad: Just after lift-off (notice, the top engine nacelles that aren't firing- they would, of course, destroy the rocket if they did): In orbit, the center asparagus section separating from the payload (and the payload jettisoning the ascent attitude control engines): Now, I know it's not technically a true asparagus rocket anymore, as the upper set of engines do not fire until the last "stage", but it's one solution to the problem.