K^2

And what do these "other" titanians feed on? Any food chain on Titan will start with acetylene. That means any life will be found where acetylene is plentiful.

I don't think kerbal's mass is added to the rocket when he's inside. When on EVA, however, you can get a rough idea of the kerbal's mass by using rocket pack to get some speed, and colliding head on with capsule, or some other light object, and seeing how the speeds of the two change after collision. Having tried the "get out and push" solution to trajectory correction after running out of fuel in orbit, I can definitely say that a kerbal is considerably lighter than even the Mk I capsule. But I have not done the math to try and find the exact value.

That would be pointless. Acetylene, which is going to be primary nourishment for these things, is going to be concentrated on surface and in methane pools. Most of the life, if any, is likely to be found in these methane pools. Some might live on rocks and in the sand in "humid" valleys as a thin layer of organic slime.

If that doesn't become an in-joke easter egg in some form, the world will be a little bit less than it could be.

I only understand the effect qualitatively, so I can't tell for sure. But dimensions of the lattice might make a difference. The biggest problem is that I don't know how you'd get rid of all the other emission modes, so it's kind of hard to tell what sort of side effects the non-existing technique would have.

Nope. We are dealing with hard gamma radiation. Can't manipulate that with magnetic field like you can with particle exhaust of any other type of rocket. The only field that can deflect hard gamma radiation significantly is the gravitational field. A gravitational nozzle would certainly help. Ball's back in your field, Stochasty. But in terms of any sort of science we understand, that's basically the absolute limit for a matter-antimatter photon drive. Ok, I can think of one possibility. There might be a way to utilize Mössbauer Effect. That would let you receive recoil from annihilation event by an entire lattice, minimizing heat production. If you can figure out how to emit photons exclusively with this zero-phonon recoil, you can make 100% (or near enough) efficient photon drive of legend. That would be the most efficient reaction drive physically possible. Unfortunately, our current understanding of relevant physics is akin to understanding of aerodynamics available to a caveman who is running in the field flapping two animal skins and wondering why he isn't flying like the birds. Either way, we are missing some very important fundamental science background in order to even approach the engineering problem of practical matter-antimatter engine. But I am surprised to see that some sort of not-entire-useless device could be built with 1960's tech, have we had sufficient stock of antimatter.

Dual-strand provides no real protection against mutation. On the contrary, twice as many places for something to go wrong. RNA, on the other hand, has stronger bonds in the backbone, if memory serves.

"Lighter" won't do you any good. Thickness is determined by absorption, and absorption, at these energies, is pretty much determined by density. So TWR does not depend on how light-weight the material is. Melting point is the only factor. If you could increase that, you'd have more thrust. But alloys always have lower melting point than any constituent, and the only pure material with higher melting point is graphite. The melting point for graphite is only a little higher, and it tends to evaporate away quite easily at high T. So Tungsten is pretty much as good as it gets.

Nah. Looking at accelerations we can get, magnetic confinement of anti-hydrogen will do just fine. I did some estimates on mission times, by the way. 1,500 years to the nearest star. 2% of ship's mass will have to be fuel, with about 95% being the tungsten dome for the engine. That leaves 3% for payload, confinement, and the ion guns. I would propose using pellets of magnetically-confined anti-hydrogen placed in the center of the dome. Pellets will have to be microscopic, so that they don't overheat from their own radiation. But it shouldn't be a problem if we bombard these using an ion gun. So now, the only unsolved challenge is getting enough anti-hydrogen. If we want to get 300kg of equipment to Alpha Centauri, we'll need 200kg of antimatter. Which is slightly more than 309 atoms of hydrogen that made up the largest batch ever made.

[Accidental double-post. Sorry.]

Hm. That leads me down an interesting thought path. I've always considered "ideal" photon drive. One that converts energy into momentum. That assumes you have a "perfect" mirror handy, and none of the heat dissipation factors are a problem. Instead, suppose that we burn matter-antimatter in the middle of a hemisphere. No reflection, pure absorption, so we don't need to worry about parabolic shape. We get À/4À = 1/4 of maximum thrust. That brings us up to 1.2GW / 1N of actual thrust. Now, what are we going to make the "engine" shell out of? It's going to be hot. Really hot. I'm going with Tungsten. We'll need about 1cm thick shell to block all the radiation. Stuff will melt at 3695K, so lets set temperature at 3690K. We'll also be losing heat from 3ÀR² of the surface. (2À from outer surface, À from inner.) Mass will also scale as R², which tells us that TWR of this engine will be a constant regardless of the size. Converting all of this to metric, and introducing density of Tngsten and Stefan-Boltzmann constant, we have the following. Mass: 1.194x103 R² kg. Max power: 99.1x106 R² W. So that's 6.92x10-5 N/kg, or TWR of 7.6x10-6. And that's actually not all that horrible. It is comparable to modern ion thrusters. And while ion thrusters will probably improve significantly in TWR department, the fact that scientists found uses for them even with that TWR suggests that matter-antimatter engines might actually be plausible propulsion method for future space probes. Because Isp of gc/4 is really good if you want to cross interstellar voids.

Depends on how fast you want to go. Each atom/ion you capture is going to impart -γvm of momentum. If you then use matter-antimatter reaction to power an ideal photon drive, you can get at most 2mc of momentum out of it. In other words, you are going to reach terminal velocity when 2c = γv. That's v = 2c/Sqrt(5) = 0.894c. Realistically, of course, your photon drive is not going to be perfect, and your limiting velocity is going to be even lower. In contrast, photon drive that carries its own matter and antimatter follows relativistic rocket formula. It can travel much, much faster. Edit: It might not seem like a big deal. 90% is already almost as fast as you can go. True, from perspective of these remaining on Earth, travel time is not going to be much different if you go 90% or 99% of the speed of light. From perspective of ship's clock, however, this is more than 3x difference. Whether that matters or not depends on application. So again, it's all about how fast you want to go. For an even slower ship, one might consider capturing interstellar medium and using it as fuel for an ion drive powered by matter-antimatter reactor. Then a very small amount of antimatter can go a very long way. Of course, if you do that, you might get away with hydrogen fusion as your power source and then you don't need to bring any fuel.

It's not even just about leaks. Air will diffuse out if there are no leaks. And even metal of which the craft is built will eventually evaporate away. But like Awaras said, these things take really, really long time.

Frozen hydrogen would make a crappy material for magnetic suspension. It is diamagnetic, so it's possible, at least, but its susceptibility is less (by magnitude) than that of water. So against even 1g of acceleration the field strength required would be enormous. Considering the catastrophe that containment failure would result in, I would not pick H2. Unless, of course, you manage to create it in the hypothetical MSMH state. That one should be superconductive, and then it would be fantastic for storage. Of course, existence of MSMH would have so many other applications, it's not even funny. If it does, indeed, exist, I wouldn't be surprised if we one day end up mining comets for it. Out of known materials, for magnetic confinement, the best options are either a superconductor, or at least, some ordinary conductor. For a superconductor, Aluminum is probably the best choice. For conductor, I'd go with Lithium.

Good to know. Thanks. If you ever figure out relationship with lift, let us know.

Yeah... Until we figure out superluminal travel, interstellar conflicts are pointless. Either one civilization outguns the other by so much that it'd be like declaring a war on one of the newly discovered tribes in the Amazon, or warships one side sends will become outdated by the time they reach the other.

Real f(AoA) is also smooth for most surfaces, because separation doesn't happen throughout the entire wing all at once. The stall is just the place where lift starts to decrease rapidly. But yes, it's more abrupt for real wings than in KSP. What about drag, by the way? Does it depend on AoA at all?

Yes. It only gives a short burst of air at these speeds. No idea how long exactly, though.

This extra energy will be stored as extra mass energy, so it won't go to waste. And if you figured out how to make anti-matter efficiently, you can probably fuse stuff efficiently too.

Life doesn't have to be exactly like ours, but there are several key elements we can pin down. Most importantly, energy flow is critical for maintaining low entropy, which you can't have life without. So we only need to look for life either on planets/moons that orbit a hot enough star, or these that give off its own thermal energy. We also know that some form of phase transitions will be required. You cannot manipulate entropy otherwise. This puts upper limits on temperatures. Id est, surface of a star itself is not a good place to look for life. Finally, and this is more of an extrapolation, we assume that evolution takes its time. That means the stable environment should exist for a long period of time. This effectively leaves us with planets orbiting stars or their moons as the only places to look for life. As that, in itself, places constraints on types of environments we deal with, we can make further statements on the types of life possible. Long story short, while the habitable zones, as currently defined, are somewhat anthropocentric, reasonable limits for where we should look for life aren't that far out from there. Of course, all of this assumes life that has naturally evolved in that environment. If we consider pan spermia or artificial life, a lot of these restrictions disappear. We are suddenly looking at any number of asteroids, comets, gas giants, rogue planets, and maybe even some dwarf stars as potential safe harbors for some kind of life. But that life got there from somewhere else, so looking for potential cradles of life is still a very good strategy. We might know two. If we confirm methanophiles on Titan, it'd be a huge breakthrough in our understanding of life in this universe. It'd take us from total uncertainty about life elsewhere and bring us to an almost absolute certainty that universe is filled with life. Forget Mars. This is where we should be looking for life. Even if we find evidence that life existed on Mars, big whoop. It could have come from Earth. Or Terrestrial life could have found its origin on Mars. We have chunks of rock filled with organic materials being bounced between these two planets all the time, and possibility of one of these bringing in some archaea bacteria is far from remote. Titan is in different category all together, however. Life there would be unlike anything on Earth. We find life there and we have two planets in one solar system with very diverse environments given rise to life. That would be the end of any kind of discussion about whether or not Earth is special in the universe. We'd know with certainty that it is not.

Nu should have been one of the metric prefix symbols. Then I could claim that Newton is a unit of mass. νT.

A mach 15+ wind tunnel?

Yes. I've adjusted it slightly since taking that screenshot, though. I moved the hard point onto the actual jet tank in the middle and got rid of the line between hard point and jet tank. It wasn't pulling fuel quit right otherwise. But yes. You can take the lines directly to engines so that they all feed from the same point. Makes managing fuel much easier.

I wouldn't know how to film that even if that was the specific goal. There is no way to actually get up close, and tracking something going that fast from that far away with a telescope? Sounds very tricky. Theoretically, I would expect most of the glow coming from ship itself, plus additional glow coming from atmosphere where it becomes ionized. The later is most likely to happen in the shock wave, so it should be a bit closer to the second set of images you link, but not quite right on any of them.

There are basically two things you need to understand about SSTO. 1) Don't try to design it as a plane. Design it as a rocket. Fly it like a normal rocket. You simply use the first stage that's air breathing and you don't separate it out when you switch to second stage. This is the lightest SSTO I've ever built. As you can see, it does not have any wings. The fins are just for extra stability. And while it has separators, it cannot actually drop the tanks, since the rocket fuel tanks are on the outside. It does separate to land. This is just experimental craft, and I didn't want to add weight with parachutes big enough to lower the whole thing. All you need to make this work is about 1.5 - 2.0 TWR and about 3 ram intakes per jet engine to get sufficient altitude. You should also do gravity turn a bit earlier than with the normal rocket. It increases time you spend in atmo, but that just lets you get more work out of your jet engines. And don't forget to close them intakes when you switch to rocket power. 2) If you want to actually land it as a space plane, you'll need to make sure your SSTO is well-balanced regardless of how much fuel it used up. This is an illustration of how I usually do this. Since CoM is aligned with centers of tanks, as the tanks drains, CoM stays put. That means that CoM is always just a touch ahead of Center of Lift, and that lets you aircraft stay well-balanced throughout the flight. This particular design, while still being a work in progress, has been successful at taking off from the runway, climbing near vertically at full jet thrust, performing gravity turn, switching to rocket power, establishing orbit, doing a turn around Kerbin, perform de-orbiting burn, and use jet power to land at KSC landing strip. Note also the long "neck" of the ship. I'm using that to counter-balance the engines, so that the center of mass is where I want it. Naturally, you don't want to waste this space, but if you need such a bit ship, you probably have the payload to put there.