K^2

We are going to learn what sort of spending the public is willing to tolerate in the name of political willy-waving.

Odd. Polynomial interpolation through these three points peaks at 0.47 bar with value 2,696. If you are saying that the maximum is above 2,500, but nowhere near as high as this, that excludes this particular possibility. On the other hand, something like Bezier can't exceed maximum key value. So that's me out of ideas. I guess I'll go and dig through the actual code now. Edit: Game uses Unity's AnimationCurve object for interpolation. It does use ClampForever option for end points. So the value at 1 bar is valid for any pressure above 1 bar. Apparently, AnimationCurve can look after tangents, so I tried using interpolating polynomial which has zero slope at the end points as well, but that gave me a maximum value that's even higher - 2,970. And I haven't been able to find more detailed documentation on AnimationCurve to find out exactly what it uses for interpolation. P.S. Here is the actual code from the ModuleEngines. private double RequiredPropellantMass(float throttleAmount) { this.realIsp = this.atmosphereCurve.Evaluate((float)base.vessel.staticPressure); float single = this.realIsp * this.g; this.requestedThrust = Mathf.Lerp(this.minThrust, this.maxThrust, throttleAmount); return (double)(this.requestedThrust / single * TimeWarp.deltaTime); }

Yes. I've posted this before, but let me re-summarize the laws of motion for a Geocentric system, because it's unlikely I'll find them now. In all of this, I'm going to basically treat Sun as barycenter of the system, but this might need corrections for finer computations of orbits. 1) All bodies in heaven attract each other with the force proportional to the product of their masses, and inversely proportional to the distance between them. (Newton's Universal Gravity still holds.) 2) All bodies in heaven are repelled from the Earth's axis of rotation by the force proportional to their mass and distance from that axis. (Centrifugal term for Earth's rotation.) 3) All bodies in heaven are acted on by a force which lies in a plane parallel to the plane of the ecliptic, is perpendicular to the track of the body through that plane, and is proportional to body's mass and component of its velocity through that plane. (Coriolis effect. No easier way of putting it, I'm afraid.) 4) All bodies in heaven are acted on by a force which is directed parallel to the line connecting Sun to Earth, and is proportional to the mass of the body and inversely proportional to the square of the distance between Sun and Earth. (Accounts for Earth's annual track around the Sun.) Each of these has its own "universal constant", which you can actually compute from Earth's orbital parameters in Heliocentric model.

A quote taken completely out of context.

It's relative to you, so long as you experience no acceleration. The key here is inertial frame of reference.

It's just matter of definition. You still get an effective event horizon. It just is't a perfect barrier, which you kind of get from black hole evaporation anyways. This only matters from perspective of information, and has no practical impact on behavior of black holes as astronomic objects. But man, with a sensationalist title like that, I'm sure we all have to brace for hordes of armchair scientists insisting that the very concept of a black hole has been disproved. Sometimes, I hate mass media. P.S. On the topic of singularity, that's a separate question all together. Though, this does weigh in favor of there not being a physical singularity, it's far from conclusive.

The relationship is piecewise-linear. The way it works in code is via the following lines in the engine .cfg file. atmosphereCurve { key = 0 370 key = 1 320 } And the game just uses first order interpolation, which means ISP is 370 at pressure of 0 bar (or bellow, but that's impossible), 320 at pressure of 1 bar or above, and for any pressure x between 0 and 1 bar, it is x*320 + (1-x)*370. This does, of course, have the general features of a sigmoid, but it's not a smooth curve. Similar code is used for ISP and thrust of game's jet engines, but these use more key points. Interpolation is still linear, however. Naturally, knowing thrust and ISP, you can compute fuel consumption. Edit: Small correction. For jet engines, thrust varies with velocity, not pressure. But again, using the same key-value interpolation. ISP varies with pressure, same as rocket engines.

Doesn't matter, either way. Black powder also contains an oxidizer. It uses saltpeter (potassium nitrate). So does every kind of chemical propellant ever devised for a firearm. Firing straight down has so many problems, it's not even funny. Every reasonable project on ballistic bombardment involves firing projectiles retrograde. Besides taking up an enormous amount of energy, the biggest problem with firing straight down is that pesky atmosphere. It almost doesn't matter how fast the round enters the atmosphere. It's going to impact the ground at approximately Mach 10. So you can fire the projectile retrograde, and have it lose less than 3km/s to atmosphere, or you can fire it straight down, and have the projectile lose more than 5km/s to atmosphere. Feel the difference? The projectile is certainly going to. This is a huge amount of extra energy. And while proposed material for the projectile is Tungsten, which is very dense and has a very high melting point, it has its limits. And firing projectiles straight down is going beyond these limits. And yes, almost the entire concept of ODIN has been taken from Project Thor.

We really need more probes heading to Titan. It is the only place in our system with potential for life with conditions that exclude possibility of cross-contamination. If we find life there, it's going to be a very important find. If we don't find life there, it's going to be a very important find. You simply can't go wrong with this one. In contrast, life on Europa or Mars could be of the same origin as terrestrial life, making it a good find, but nowhere near as useful one in the big picture. We already know that life can be carried between planets on asteroids. What we need to know are the odds of life evolving independently in two different environments. And we can't make even the most basic estimate having just one data point.

If they manage to get as much of it reusable as they promise, no, that will pretty much mark the beginning of the end of disposable launchers. No disposable system can compete with what they are promising for 9R. How that goes, though, is another question. Keep also in mind that the project in question has been proposed at about the same time as F9, and 9-R wasn't even thought up yet.

It's not even chamber walls. I'm more worried about LOX being used to cool the nozzle bell. These are small channels at high temperatures that are going to carry one of the most corrosive substances possible? On the other hand, I see no reason why LOX and LH2 can't be simply switched here.

Then we might as well assume they have the protocol and access codes. In fact, I wouldn't be surprised if these things, if not completely open to public, are under such low security that someone who really wants them, can get them. Access to communication hardware is the hard part here. That's the only real obstacle in you taking control of the Voyager spacecraft. Everything else might as well be just given in comparison. Given the amount of junk that's up there? Probably.

Fantasy is fine, but General Relativity yields absolute acceleration and rotation. And seeing how GR itself is a consequence of local symmetries, I don't see how you plan of getting out of that. One can always define an inertial frame, making acceleration and rotation absolute quantities.

Motion is relative. Rotation is absolute. So is acceleration. Which is why an orbit which has a particular orientation of its major axis will maintain that orientation regardless of your choice of observer. P.S. I'm neglecting various sources of precession for simplicity.

And you know a lot of high school students with a total, unsupervised access to a radio telescope, which by now you'd need to pull such a prank?

That seems to be part of the reason why there is a dedicated parking orbit, rather than delivering cargo to destination orbit directly. Debris from failure bellow 200km would decay fast enough to not be long-term concern.

Inflatable shell to contain cargo can be deployed for peanuts compared to launching a pressurized ship with the same amount of cargo. And this shell would only have to be launched once, and it can contain all the docking adapters you need. You are really making it more complicated than it needs to be. Certainly, some amount of work has to be put into all of this, but we are contrasting it to hundreds of millions of dollars worth of cargo launches yearly, and cutting prices on these anywhere from 25% to 75% easily. Put five years of savings from this aside and you can organized a manned mission to the Moon, for crying out loud. And you're worried about docking certification. Bah!

Again you've missed the point and the big picture. The tug can take the 1T payloads to a location near ISS. 100% automatic. No involvement from ISS crew necessary, because no danger to ISS is presented even in an event of an error. When enough cargo is assembled at the nearby location, that same tug can take all of it to the ISS in one bulk. This stage is monitored from station, same as Progress. It will deliver many tons of cargo, same as Progress. The tug will have automatic controls with manual override if something goes wrong, same as Progress. The only difference is that the total cost of getting that cargo to the station is significantly lower. That's after we include all of the additional hassles. You keep insisting that there are downsides, but absolutely none of them are backed up by any numbers. Indeed, numbers contradict your statements time and time again.

I don't think you understand the concept of cost-per-launch. The reason that it's cheaper to move apples by truck is that cost of hiring an operator is comparable to cost of fuel, and cost of equipment is kept low due to it all being very reusable. So your biggest loss on running hundreds of couriers with bicycles is money you'd be paying to couriers. The cost-per-delivery of each apple includes all that and ends up being way cheaper with a truck. But now imagine a situation where you have to throw the truck/bicycles away after single run, and people are poor and work for peanuts. Now it's just a matter of fuel consumption and cost of equipment, and bicycles are just so much cheaper that you'd be a very bad businessman to pay for a truck. All of these considerations are included in the cost-to-launch. When you put it all together, the final price of putting 1kg of cargo by either method is all that matters, and with such cheap launches, the final price does end up lower despite all of the problems you've been talking about. Because, again, all of this is included in the price tag. From perspective of ISS, this doesn't have to be any more complicated either. Tug can be fully autonomous and collect all of the cargo from multiple launches a safe distance from ISS. Then operators at ISS would take that cargo, using the same tug, all at once to the ISS. No different than getting a shipment from one of the Progresses. This can work even better for a fuel depot, because one of these can be 100% autonomous from the start. So who cares how many round trips the tug will have to make, or how many launches you have to make. The final price of fuel in orbit is lower than if you used an expensive, reliable rocket. And that's all that matters in the end.

Depends on range. For maximum range, you need an almost orbital velocity. So that's about 7.8km/s to reach ballistic trajectory, plus about 1.5km/s for aerodynamic losses, which puts you at about 9.3km/s. However, far from all ICBMs are capable of targeting a point clear on the opposite side of the world. A rocket capable of about 7km/s can already put a projectile on a high ballistic trajectory with a target located over 6,500km away, which is definitely intercontinental range. So if you are looking for a minimum, it's about that. Interesting thing to note. While long range missile will have a shallow trajectory, with apogee just high enough above the atmosphere to avoid loosing too much speed on the way, a "short range" ICBM will have a trajectory that's much closer to what you picture a ballistic trajectory to be, with apogee well above 1,000km.

That's not estimating. That's just guessing. Round trip would take less than 300m/s of dV for the tug, which is less than 10% of exhaust velocity of non-cryogenic fuels, which results in dm of under 10%. Even including mass of the tug and the engines, 200kg would be an extremely paranoid upper bound for the fuel you need to use up. So if we look at the worst case scenario, going with 2M/launch, only 800kg usable, and 1/3 rockets going boom, we still get $3,750/kg, which is considerably cheaper than any existing alternative. (F9 is well over $4,000/kg) And this is as bad as it could possibly get, according to all of the information available. Realistically, we are looking at a far more favorable cost/kg.

Which it is, seeing how cost per ton of cargo is much lower. I mean, at the end of the day, that's what you care about. How much it cost you to deliver X amount of cargo. Why don't you do the math on this before making claims like that?

The vertical ascent problem has a number of assumptions in it that might not be fulfilled. 1) Atmospheric density is either constant or drops exponentially. (Exponential in KSP, a little different in real world.) 2) Drag is proportional to mass. (True in KSP, but not in real world.) 3) Gravity is constant. (Not exactly true in either KSP or real world, but very close.) 4) There is no rotation. (Not true, but doesn't make much difference either.) 5) The target is "infinitely" removed. So there is no coasting to reach the necessary altitude. (Depends very much on how you run your tests.) All of these affect a real launch, which is why real TWR for optimal ascent might not be exactly 2. This also doesn't take into account the gravity turn which makes things very different. These are just some general points which may result in you getting something a bit different. As tavert suggested, if you post your code, we can probably say something more specific. But under above assumptions, optimization TWR=2 is exact. It's very simple to derive for constant atmospheric pressure, but takes a bit of work for exponential atmosphere of KSP. Result is exactly the same, though.

Now imagine that you had to buy a new car every time you got groceries, and somebody offered you a car at 1/4 of the price which has 1 in 3 odds of blowing up. Because that's more like what's going on here, and that's, actually, a great deal.

That's why the fact that proposed payload is bulk low cost consumables has been stressed several times.