EzinX

Again, we know certain things are physically possible. We know to get to those things, we need to do other things on a vast scale or those things will remain unobtainable. In the two examples I gave : for nanotechnology/APM, we know that we need equipment that can move individual atoms around and detect the positions of individual atoms before we can even think about developing the tech. We also know that any "nanofactory" would need thousands of unique designs for all the intricate molecular parts such a factory would need. Finally, we know that until a complete factory is assembled, you get no real benefit from the technology. There is no rational way giving a 1 million dollar grant to a PI and a few grad students will result in these kind of results. It would require a coordinated effort between thousands of people. For scanning human brains, we know that if you don't scan an entire brain, or at least the majority of it, you have not captured enough neural circuitry to even theoretically mimic what that brain does. Similarly, if you do not pay for a big enough supercomputer to emulate the whole thing as a single integrated system, you do not have any chance of ever mimicking human sentience via emulation. Look, the Manhattan project wasn't unexpected, either. Everyone who planned and executed it knew they needed to pay for enough fissionable materials for a critical mass, or they would not have a bomb.

I strongly disagree. Finding low hanging fruit is certainly breadth first - low hanging fruit being defined as a breakthrough idea or technology that can be developed cheaply and quickly by a small team with a small budget. However, at this point, the low hanging fruit pluckers have already been searching for decades. There's a raft of ideas that all known, accepted theories of science say will work. Atomically precise manufacturing, human brain emulation, etc. All these ideas have 2 elements in common : 1. All accepted theories of science say that if the technology is constructed and works, it will lead to revolutionary increases in human capabilities 2. A rough development plan for how to develop the ideas into working form requires billions or trillions of dollars Instead of going for the low hanging fruit that can only result in marginal benefit to extant humanity, maybe moonshots are a better use of resources. Conquering death itself, or getting the technology that would let us tear apart entire planets with self replicating factories are a lot more useful than finding a marginally better material for making a cell phone screen.

Please don't fight the topic. I acknowledge that due to all the problems that known physics would have if the Woodward Effect is real, the measured force probably is caused by an interaction with the external environment whenever tests are performed. Neverthless, if it were a real thing, what kind of performance would you get from a spacecraft? Wikipedia provides a big nasty equation predicting a transient mass fluctuation. http://en.wikipedia.org/wiki/Woodward_effect Help me translate this into theoretical thruster force : mass ratios based upon the best known real world materials that exist today for the capacitor parts. I would assume the actual space drive apparatus would suspend this variable mass object between large superconducting magnets and oscillate it back and forth as rapidly as possible. What kind of force production could you get relative to the mass of all this equipment? What would be the power demands? As the spacecraft accelerates and has a higher relative velocity to the average velocity of the external universe it is actually interacting with, what would that do to your acceleration?

One nasty problem is that anything that will kill an extrophile for certain will probably damage the sensitive parts on the probe - the plastics, circuit boards, etc.

It matters, but I don't think it's the important factors for designing a heat shield. I think the important factors are : 1. Thermal Conductivity 2. Melting point 3. General all around durability to shock, air pressure, temperature extremes, etc. Specific heat doesn't affect anything other than it affects how much heat is stored in the shield at touchdown..

Apollo wasn't done at all costs, and it wasn't an effort that involved 100% of available resources. NASA had institutional reasons to avoid losing astronauts, and it took the time to develop computerized flight control for the lander (from scratch, essentially) when a riskier landing without computers was probably possible. I think you need to look farther back in history at the scale of Von Braun's efforts and his planned missions for exploring Mars. I think you're simply misunderstanding what a parallel effort means, and I think you need to read more ww2 history books. Your arguments have little merit except that the absolute bare minimum serial time may be a little over 4 years. Double the time in a scenario like this (8 years) doesn't mean double the progress, it means exponentially more progress. For instance, if we have 10,000 aerospace engineers today with the right skillset, you could get 10 million, easily, with a total mobilization effort and a full 8 years. You could build a large number of nuclear reactors, probably thousands, to create the plutonium you need for more bombs. And so on. The ww2 war fleets that were built certainly dwarfed the scale of this project in tonnage, although of course they were a much lower quality product than an Orion spacecraft, which must be carefully balanced and wired with complex control systems.

So, I'm off by a factor of 8 regarding the bombs. Well, the next question is, how many years is the bare minimum. 8 years? 16? The reason 4 years isn't enough time is because the critical path for the slowest step - probably designing and prototyping the spacecraft - exceeds the time available. That's why if you can build one Orion spacecraft, you can also build 4000 of them with just a small increase in the linear time taken. You do realize that all steps can be done in parallel, even if you have to crash train the engineers to do those steps from people who are the closest match to the skills you actually need. (suppose that 10 parallel tasks need engineers from your same limited pool of engineering talent. You could put your engineering talent onto the longest tasks from those parallel tasks and crash train new people who have related skills to perform the rest) Even if you're training MIT grade engineers, for someone who has the proper support structure and works 16 hours a day, you could probably finish the training in 18 months instead of 4 years. You could probably get through the state school aerospace engineering curriculum in about a year from scratch. If you started with people who already had experience in some of the skills needed - aerospace engineering technicians, math and physics majors, etc, you could train them in less time than it would take for the smartest people you could find right out of high school. The next problem is experience, though. Book learning isn't sufficient to make a skilled engineer, they need to build actual systems and test them, then refine their abilities. That might take another couple years even going flat out. I see what you mean, 4 years may just be too little time, especially since at the very beginning, a lot of that time would be wasted setting things up.

1. The specific heat doesn't matter if you're talking about a thin layer. This is also the reason why real life heat shields apparently don't contain that much heat energy after reentry, because the material did not conduct heat and it did not ablate away. Instead, the surface layer got incredibly hot and conducted that heat to the cooler air once the craft is on the parachute phase. With that said, most of the energy that was in the craft (KE + PE) would have been carried away by the air striking the heat shield and flowing around it during the hot part of reentry.

Well, how many people can we bring? If 100 nukes gets us 10,000 people, and we have 40,000 or so, that's 4 million people. That's 400 ships the size of a naval warship, and since you have 10x redundancy, you are building roughly 4000 total vehicles and only plan to launch 400. (the extras are for the less successful designs) Honestly, the 100% essential people leave a lot of empty seats. As you yourself pointed out, there's only so many aerospace engineering grads who are also young and who also have practical experience, just like there's only so many life support and ecology experts who also meet the criteria. Got any delta V tables? How many bombs does ground to orbit take, and does it take more bombs once in space since you don't get the benefit of the atmosphere to increase the mass of the shockwaves? Look, please don't misunderstand. The problems here are immense. I'm not going to claim it would definitely work, or even that the chances are particularly good. With that said, I think it's mind numbing and stupid to just declare it to be impossible without even thinking about how you might solve the problem despite the issues involved.

You give all the people who help a nonzero chance at a seat. You use a weighted lottery system, where youth, useful skills, positive attitudes, gender, genetics, fitness, and your productivity all change the "weight" that affects how likely you are to be selected, but everyone has a nonzero chance. You pick people up until the very last launch.

Does China not have the resources to do all 3 simultaneously? They do have a billion people after all, and the industry to build almost all of the equipment for the space missions for low cost in their own factories.

If the heat shield is an extremely poor conductor, then the outer surface of the shield will remain red hot and will conduct it's heat directly to the cooler air flowing over it once the spacecraft gets to a lower altitude. Interestingly, there's a paradox here. Imagine the heat shield has a conductivity of 0. No heat at all flows through it. Then, the outer surface atoms of the heat shield will soak up all of the heat from the air pushed aside by your craft on reentry. Since only a layer of atoms just 1 thick has absorbed any heat, once the spacecraft slows to reasonable speeds, you could EVA out and possibly put your bare hand on the heat shield because a 1 layer thick atomic layer, no matter how high the temperature, has very low actual heat stored in it. This is the same reason you can grab wax paper used in baking in the oven with your bare hands, even if the oven temp is 500 Fahrenheit. It would also cool itself off very rapidly. Now, there's another interesting paradox. If the heat shield has zero conductivity, when it heats up enough, the outer layer will be so incredibly hot that atoms start ablating off. So your heat shield needs a very high melting point - ideally, a higher melting point than the temperature of the plasma that flows against the heat shield. So Deadly reentry is dead wrong in it's heatshield model, huh. What would really happen if you reenter too hot is that your heat shield would begin sublimating to gas (not to mention the structural stress on the spacecraft and crew) but it would not do this unless you are entering much hotter than a "typical" reentry on Earth.

If you have telemetry from the cycler and it reports all the systems work, and your intercept craft looks good as well, I'm trying to imagine a scenario where if you were in a larger, more capable spacecraft you would survive when you would be dead in the cycler scenario. I suppose if you had a mishap similar to what befell Apollo 13, where you have a tank explode and kill your entire service module while making the burns to intercept the cycler, you'd be up the creek. You would be hundreds of m/s short of ever meeting the cycler, and you would not be able to return to earth. While, on the other hand, if you were in a massive spacecraft like the proposed Mars Colonial Transporter (yes, I know that thing is unlikely to ever be built, but if it were...) you would probably have additional stages you could use to return to Earth with, similar to Apollo 13. With all that said, there's going to be a large number of potential failures that could kill everyone no matter how you do it. That's just the reality of what you're trying to do. The marginal risk increase of missing your cycler intercept might not matter much in the grand scheme of things.

That "reusable" nature of the cyclers means that the science fiction cliche of them is that they are kind of ramshackle and smelly inside after a few decades of use. That's the real problem with the Cycler concept - how many cycles could that reactor, those ion engines, etc continue to operate before wearing out? It might be difficult to replace integral components of the spacecraft when the next supply shuttle from earth rendezvous with it.

My point is that an orion spacecraft is a massive piece of metal and some shock absorbers. I'm saying that if you had 4 years, you could get as many orion craft as you have bombs for built. To solve the issue that you don't know which designs will work, you might build 10 or so independent series of craft separate from each other and only commit the bombs to the craft that have the higher success rate. "designing a life support system". You know you need lots of coolant compressors, lots of fans, lots of grow lights, lots of plants, lots of solar panels, lots of wire - you just throw mountains of all that onboard and have a rough sketch of a working system that might work. You'd have your technicians on the Moon redesigning and rebuilding the life support system as the base is being built. Human losses mean nothing in a scenario where everyone who doesn't make it to the Moon is dead anyways.

This is where you have redundancy. You have a dozen different ways to refine lunar ore. You have many many machine shops worth of basic equipment. You have hundreds of thousands of the best "problem solving" technicians and engineers you can choose from on Earth. Orion nukes can do that, can they not? The bigger versions of the craft use much larger yield bombs and can have thousands of passengers onboard. They are a more efficient use of your limited fissionable materials, which I suspect would be the ultimate limiting factor in this scenario. You don't have to make everything right at first. Certain things are too many steps down the tech tree to make realistically on the Moon without many years of work to figure out a way. Computer chips, sensors, that kind of thing - you could probably fit millions of general purpose ICs (like the system on a chips used in cell phones/Rasberry Pis) into a few crates crammed onto some of the orion craft. I don't think it's almost certain to fail. The key is you need enough parallel paths to do any critical step - expanding your infrastructure or just keeping the air recycled - many different ways so when things fail unexpectedly you have another way to do things. You also would need a population on the order of thousands to millions of people, depending on your technical limitations in transport. You don't sit there in boardrooms and pontificate ways to design things. You do stuff like come up with the requirements for a system you need, and then announce it publicly that any team of people who solves your problem gets a seat on one of the launches. Need a lunar bulldozer? Get hundreds of teams working on a design in parallel, and then have them compete with each other in a Darpa style competition to find out which designs work. Need designs for lightweight industrial equipment that is multi-purpose? Ditto. And of course, anyone who publicly speaks out about the project or says it's "almost certain to fail" you summarily execute. You need positive thinkers only.

I suspect the way these spacecraft would be designed is that they'd have an orion pusher plate stage used to get from the ground on earth, and you'd probably eject the pusher plate once you complete the deorbiting burn for a lunar touchdown. You'd use some kind of cheaply built rocket engine for the actual lunar lander stage. You could shield your "chosen people" (presumably most of the seats would go to young people distributed among your critical skillsets) from the fallout from all the Orion launches by keeping them in training camps a continent away from the Orion launch sites until it's time to go, and you'd bring them to the launch sites in hermetically sealed vehicles, since you don't want any fallout exposure to future mothers, etc. The failure rate for these Orion vehicles could easily be 10-50% and that would be acceptable losses. You wouldn't hold endless hearings and recriminations if one blew up, you'd try to make quick and dirty rapid repairs to future vehicles to stop whatever mishap took out the last ones. I suspect with 100% of industry put into building the Orion vehicles, which would be these overbuilt monstrosities of steel probably, sort of a higher tech version of a Liberty ship, the limiting factor would probably be bombs. There's 20-30k or so warheads that could be scrounged from the global arsenal, and the propulsion warheads are smaller than the strategic ones, so when you rebuild each warhead for propulsion you would use less weapons grade plutonium. You could rapidly build crude and cheap nuclear reactors based on the design used at Chernobyl to make more plutonium, but you obviously are limited in how much more could be produced in the remaining time. How many devices would be needed for liftoff to lunar insertion? 100 per ship?

Check your history, friend. First of all, WW2 had numerous examples of this kind of rushing, took place over a similar time period, and most of the projects ultimately worked. In order to solve some of the bottlenecks associated with an engineering project on the scale of Orion spaceships, there's a lot of mitigating methods you could try that enormously increase the cost but that's irrelevant. One of the methods is that whenever you come to a crossroads, where there's debate on the engineering staff as to which of several approaches will solve the problem, you simple spend the resources and implement all of the solutions. The Manhattan project did this : there was debate over which method of enrichment, and which fissionable material to use. They ended up using them both. You would build the propulsion bombs by ripping the guts out of the world's nuclear arsenal and using strategic reserves of weapons grade plutonium that both the USA and Russia have. You'd probably try several orion designs and build them in parallel by the hundreds, possibly thousands (I suspect the problem might still be a lack of nukes and not ship hulls). Taxes towards this project would be essentially 100%. Seats on the ships would be competitively awarded to those individuals who made the most useful contributions. It doesn't really matter if several of the orion designs turn out to be failures and blow up on liftoff. You would simply launch the hulls that do work. If you have to rip the titanium needed out of existing jets or wherever else the metal is used, you do it. If you have to start open pit strip mines, you do it. If you have to demolish the buildings in major cities to get the copper you need, you do it. If you have to shoot anyone who protests or refuses to work, you do it.

The problem with in-orbit is simple. You only have the raw materials you brought with you, and the only way to get any more requires using technology that you brought with you. If you, say, had to wait a century for the earth to cool down (literally! from all the volcanic activity!) you'd be returning with century old reentry vehicles. If you're on the moon, it takes more delta-V, but you can in principle continue to expand your civilization and build new tools with the lunar ore. It's still a precarious situation - run out of spare parts for a critical system and everyone dies before you can develop the infrastructure to build new spare parts. However, in theory, if you bring enough equipment and machine shops and furnaces and so on along you could mine lunar ore and turn it into almost anything you needed. Certain things would be incredibly tough to make in this situation, microchips and imaging sensors seem like obvious examples. However, maybe there's a crude way you could keep your civilization running with cruder mechanical and vacuum tube based electronic systems in order to control the various compressors you need to run your life support systems. I wonder what you would do when your lunar solar panels begin to die, making them in-situ sounds incredibly difficult. You could build horizontal centrifuges to expose your population to a full gravity at least some of the time.

Why not build orion drive spacecraft and move to the moon? 4 years is enough time to develop them if there's no expense spared, is it not? And you could carefully select a group of enough people to have every skill covered, and then pack enough equipment and supplies to actually build a self-sufficient industrial infrastructure using lunar ore.

From the slug's reference frame, their encounters with the air molecules take the same amount of time as always to resolve, converting the slugs to gas and then probably subatomic particles. But from the earth's reference frame, the slugs take longer to break up.

Presumably you could adjust the slug speeds so that time dilation keeps them cohesive until they reach the lower atmosphere.

Suppose a group of beings with advanced technology decided to bombard earth. Rather than using fission/fusion bombs, they use a mass driver so long and powerful that the projectiles exiting it travel at 0.99c . The projectiles are iron slugs. Since any object made of matter traveling above 86% of the speed of light has more energy than the equivalent mass in antimatter, how would this terrible energy be expressed upon impact? Would it cause spontaneous fusion or fission between the matter it impacts? Would the neutrons released cause enough neutron activation to be significant? To throw in some numbers, each projectile has 100 megatons of kinetic energy relative to the earth.

Ok. So you need a place to live. Bonus points if that place has raw materials that you didn't have to launch. And it needs to be safe from Pallas. There's actually only 2 possibilities if a redirect isn't physically possible. You can either build an underground or underwater protected habitat (how much devastation are we talking about here? Will we know in advance which side of the planet it will impact?) or you can build one on the moon. Advantage of the earth habitat is that even post-impact, some of the plants and animals might survive the ice age and you would need a lot less technology to survive even in this hostile environment. The moon habitat's only advantage is that the impact shocks won't affect it. I need more data on the effects of the Pallas impact, but, I suspect that building 3 massive equidistant earth habitats along the equator (since you probably don't know where they will impact), each stocked with years of supplies and essentially an entire Noah's ark worth of plants and animals (well, whatever you can reasonably store, you'd probably have to store most plants and animals as DNA samples and hope to be able to restore them many years later) would have the best chance of species survival.

What's this 1/R potential? At any given point along a spacecraft's trajectory, it's subject to forces from gravity and from it's own engine. Those forces always sum to an acceleration vector. That vector varies over time. You have a starting position, and you want to know the new velocity and new position. Boom, you just invented Euler's method. You then use a fancier method to compensate for some of the changes of acceleration over the timestep and you end up sampling at several past states and you end up with 4th order symplectic. Mathematically proving it or studying effects of the integrator and it's error over time is a whole field of study, but, regardless, you have something that works pretty well. I take it this 1/R problem is some change in energy from close approaches to planets? How big of a change are we talking about here? With a game, you can cheat in several ways that scientists running simulations cannot. For one thing, you can simply declare that the planets obey a pre-baked solution like VSOP87. Even the longest KSP campaign is realistically not more than a century anyway, so some of the numerical integration methods are probably good enough that you won't have them crashing into each other or drifting too far from their orbits. You only really care about N-body effects on a spacecraft and so your numerical simulation does not have to be infinitely accurate.