K^2

Ions are much heavier than NTR. But yeah. I don't think NTRs have the necessary specific thrust to be useful for SSTOs. And once you're in orbit, SABRE isn't practical. Russians are currently working on an NTR-powered ship. Albeit, with a twist. They have an electrothermal rocket powered by a nuclear reactor. Apparently, they've had some success, but they're still as far from actually flying it as NERVA ever was. And, of course, it's not designed for exiting atmosphere, but rather be delivered to orbit, fueled up, and used for interplanetary exploration. But it's a Russian project, so it might be just vaporware.

Neat. I'll have to try this with my results. (They are inherently parametrized.)

And way more fun.

Ok. Will do.

In either case, the cubesat is deployed with some relative velocity, and its orbit decays much faster than that of a station. So it's not a problem in any case. No propulsion system is strictly necessary.

Found the problem with my code. The β'1 term is wrong. The ∂U/∂r portion of it is right, but ∂U/∂θ term is also non-zero. So I have to add that in. The rest looks good, though. β1 has the strongest impact on position of the satellite along the orbit, but not on the shape itself. So the trajectory matches. Which is good.

We might be able to organize that. I have connections at several universities and High Schools with professors who do various educational programs. I'd rather not, because we'd have more freedom. So if we can pull together enough money for a completely independent launch, that'd be much better. But if we can only raise the funds for the basic hardware, it'd be better than scrubbing the mission.

Essentially. However, the metastable half-life is on the order of decades, while the triggered half-life can be on the order of fraction of a second. So while there is, technically, a half-life limit, in practice, it's short enough that you can get as much power as you need for your application. Some of them are rechargeable, but the only known, practical way to recharge these is with synchrotron radiation. So currently, it's absurdly expensive either way. That said, it's already much more manageable now than it was a decade ago. So we might see practical rechargeable nuclear isomer batteries within our life time.

Nice. Capped throttle. I'm still working on that. What was the lift-off TWR on this run?

All of these problems are fixed with an "Experimental" sticker. (Yes, I know that won't apply to commercial aviation.)

I've never argued against caution. If this is your entire point, we can move on from this discussion.

The general features for total thrust are definitely the same. I was worried about that double-hump, but it seems to persist in all of the optimization results. That's very interesting.

Quick update. I've worked out the EoM for the constants, but I definitely have a math error somewhere along the way. Mathematica version of 2D simulation runs and produces fine orbital motion when no forces are applied, but not all of the constants are correctly updated with a perturbation force. I'm pretty sure energy and angular momentum are correct, but argument of periapsis and time of periapsis passage seem suspect. On the plus side, I have a Hamiltonian dynamics simulation running along side, which I can use to test all of the values. So I should be able to work out all the bugs soon. Then I'll need to move it over to 3D. (That introduces ascending node and Lz.) And then move it all to C++ code and write good integrators for the EoMs. At any rate, getting there. Edit: Poked around at it a bit more. It's starting to look like the errors might actually be purely numerical. I'll have to switch over to C++ sooner than I thought.

By this logic, general population should not have access to cell phones, internet, and probably computers in general. There is rational caution, and then there is paranoya that prevents technological progress. You are firmly in the land of the later. You said that this tech should not be allowed on civilian aircraft. That's pretty binary. The burden of proof is on people who can never prove it? Fantastic. Logic isn't your strong side either. I have studied security. I've worked tech support for content management system, and I do IT consulting on the side. I'm far from an expert, certainly. But the most fundamental principle of security is "sufficient security". Because no security is absolute. Question is, how much resources it would take to misuse the technology, vs how much resource it would take to carry out a similar attack without it. And building a nuke is easier than causing a nuclear isomer battery to do any significant damage. Still want to continue discussion from perspective of security? Yeah, go on, keep splitting hairs and invent unicorns. It's been working so well for you. You are still arguing denying access to revolutionary technology over a phantom threat. One that you refuse to actually support, and one that you have no expertise to support. And your strongest argument is that top researchesrs who were payed to come up with ways to weaponize it were working with theoretical framework. I did not think you can make a weaker argument than you started out with, but you keep surprising me. Another argument from ignorance. Lack of understanding doesn't make your argument stronger. "I don't know" is never a good argument. And that's what you keep falling back on. Never have we had an attack based on sustained power output. And we have nuclear power plants around, power from which could have been rerouted for something like this. Sure, it's not portable, but it is hundreds of GWs of sustainable power. You'd think someone would find a way around portability. But no, it's just enough for you to claim that you don't know any better, right? Except that you are being proven wrong again and again on this point. Why doesn't Iran have nukes, if you claim it is possible to replicate given only the access to information, resources, funding, and general knowledge of technology? Maybe this is about the point where you finally realize that you simply don't understand the complexities of the task involved, and start listening to people who have a somewhat better understanding?

If you bothered to actually read the thread, you'd probably realize how ignorant this statement is. First of all, diseases mutate, and lack of vaccination assits them in doing so. Every once in a while, an otherwise harmless disease becomes deadly. Yes, to healthy individuals with good diets. If you don't vacinate, the next time you have an ordinary flu, you might be actually contributing to deaths of hundreds of thousands in a future outbreak. How do you feel about that? But even if we forget about that, simply the decline in productivity due to mundane flu result in huge amounts of losses to the economy. Losses that can be easily avoided with imunization. Losses that could have otherwise become higher wages. Or more money for research. Or even just longer holidays at work. And we're throwing it all away because?

Key word here is feel. Are you an expert in high energy? Weapons technology? Nuclear physics? Any field related to this at all? I actually understand how the trigger works. And I know quite a few things about high energy physics, because that's the other name for my field of work. So I can tell you, as someone with some degree of expertiese both in particular technology and in terms of applications, that it is safe. Certainly far safer than technologies it's going to replace. What you put against that is that you feel that it's dangerous. And know what? Someone will always feel that some piece of new tech is dangerous. Take a look at the vaccinations topic. There will always be people who will object to new technology without having any idea how it works, because it feels wrong. And if we start listening to people like that, we will have zero progress. So please, stop being part of the problem. Either study the subject, and come up with an actual, plausible security concern, which we can either address or find it to be serious enough to change policy. Or step aside. Don't be one of the ludites. On DARPA budget? Most of them. The most extensive research project was the TRIP experiment. It included questions of production, triggering, and applications of the Hf178m2 isomer for power storage. The research is still partially classified, because it contains potential military applications. They've concluded that it's too expensive to be worth it at the moment. So yeah, we know exactly what dangers are present, and I can tell you that general public has nothing to worry about from the batteries. When this is weaponized, it will be a completely separate, government funded project. It's not something that a band of terrorists can simply built on top of an existing battery. Again, this argument can be made to turn any advance into a potentially dangerous one. In fact, it doesn't even have to be an advance. This argument can be used to label any existing technology as dangerous. But more importantly, we have had ability to produce that sort of power output from portable device for many decades. This is nothing new. Only the sustainability of power output is a new feature, and sustainable power is a mark of peaceful applications. Oh, so a University can do this, so long as it has resources it never can get? Sure. In that case, a bunch of bums off the street can build a nuke. You just have to give them technology, man power, budget, and classified materials access. So again, lets make something clear. Iran can't build a nuke. Despite trying really hard. Despite having fantastic research facilities. Despite sinking enormous amounts of money into it. They can't build one. As a matter of fact, we've seen that in practice, this requires so much resources, that only countries that can do this unopposed and are therefore acting sufficiently responsibly, have managed to build nuclear weapons. Even the most questionable on the list, is still a government that has not risked using these nukes for any military purpose. The scale at which terrorist acts are committed and scale of resoruces required for nuclear weapons manufacturing aren't of the same order of magnitude.

Yup. Who's better to get your satellites to correct orbit than people responsible for Fobos-Grunt?

Entirely possible. Problem with that, Earth hasn't been around long enough. But again, length of longest trajectory from today's Earth to Big Bang is probably what you are looking for. After all, if you follow that trajectory from Earth's formation to now, you do get Earth's age correctly, and that's unambiguous. No argument that it's an estimate. But which assumptions do you believe to be misguided?

First of all, this applies to absolutely every piece of new technology, software, or even idea. By your logic, absolutely all of it should be kept out of public hands. And we'd still be arguing on whether or not that "bow" thing is safe to hand out to our hunters. Secondly, we have had hundreds of experts trying to figure out how to misuse nuclear isomers for at least a couple of decades. Most of it, sponsored by DARPA, but there are a lot of general research projects there as well. A problem that's new to you isn't a problem that's new to scientific community. Limitations are known. And it might be possible to read just the right incantations to open up a portal into another world. But you're talking unicorns again. There is absolutely no plausible way for the system to work differently than expected. If you have a metastable nuclear isomer, it will either decay on its own with predictable probability, or you need to excite it to a higher energy state, which is unstable, so that it decays significantly faster. These are the possibilities. Oh, it could also lase, but also only under very specific, well known conditions. Anything else happening violates basic principles. So we're back to the battery being either a) inert, or releasing energy at the rate governed by the trigger. Could something else happen at all, in principle, with some probability? Sure. Could nucleons in led be rearranged to turn into gold? Of course! But I'm not going to recommend restricting general public's access to led out of fear that someone will ruin economy by floodding world markets with cheap gold. This is the level of paranoia you have to admit to in order to claim a possibility for a misuse. You said a university could do it. Now it needs to be a small country. But the answer is still no. Because you can't move these sort of resources covertly. And if a large corporation or a country will try to develop nukes, they'll be stopped by other world powers. Look at Iran. They really, really want nukes. And they are investing more money than any world's corporation could afford to. And they still don't have a nuke. But if only they knew the secrets that you posses!

You can have influenza, and get away with just cold-like symptoms. Though, usually, if you've had similar strain or been immunized to one before. I'm prepared to bet that you have had flues that you've taken for a bad cold. But yeah. A full on influenza that your system wasn't exposed to before is absolutely not a thing to take lightly. Even if you don't mind two weeks of misery, one of which you're likely to be almost totally incapacitated for, there is a huge risk for all sorts of complications even if you are an otherwise healthy individual. The hell through which it puts your respiratory alone is reason enough to put serious effort into avoiding it.

Not exactly. I think this is a good place to step back a bit and just look at time in Special Relativity. So lets forget gravity and curved space-time for a moment. A specific point in space and time is usually referred to as an event. If you have two events in Special Relativity, there are two possibilities. They can be space-like separated or time-like separated. If the events are time-like separated. a) Their order is fixed. If event A happens before event B from someone's perspective, it happens in that order from every perspective. If A happens first, A message from event A can arrive at event B. c) As consequence of above, A can cause B. d) You can choose coordinate system where A and B are in the same place, just different time. This brings up causality. If A causes B from someone's perspective, then there is no frame of reference in which B causes A. (This is only true locally in GR.) If two events are space-like separated. a) Their order can change, depending on observer. The two events can be simultaneous. c) They are not casually related, and no communication between two events is possible. The simultaneity is the most important bit. In order to define time, there has to be a concept of "right now, somewhere else". But if two events are simultaneous, they are space-like separated, and that means that from someone else's perspective, they are not simultaneous. Which means that they can't both be happening "right now". However, if the two events are time-like separated, you can always define the longest amount of time a message can travel from event A to event B. As it turns out, in Special Relativity, this path is going to be a straight line from A to B. (In GR, it's going to be a geodesic.) What's even more interesting is that as consequence of point d) above, we can choose an observer from whose perspective that message stays in one place, and just has to wait for B to happen. This is the most natural way for us to define time between two events. It's unambiguous. It does not depend on choice of frame of reference. And it's usually what we are talking about anyways. This is what I was talking about with the age of the universe. Big Bang has a special property that it has caused everything. Which means that absolutely every single point in space-time that you can get to is time-like separated from the Big Bang. As such, we can define the age of space near any event by this longest distance from Big Bang. Better yet, we can always define a coordinate system in which the location of Big Bang was "right here", which means, it's only separated from us in time. So again, this kind of definition of the age of the universe is very natural. We just have to figure out what's the longest amount of time something could have aged between Big Bang and right now. And this is completely unambiguous.

First, give me a nefarious task that requires it. You insist that a lot of damage can be done with this. And it simply isn't true. You can do damage with high power output, but you don't need long duration, and I can give you tens of MW for a few seconds with a hand-held device. Including electrical power, if you need it. So any criminal act you can come up with, can already be pulled off with easy to obtain tech. Rice should be banned. It can be used to commit terrible crimes. I don't know how, but you need to start thinking outside the box! Give me an example where you can actually use it to do harm, or you don't have a case. These aren't unicorns. The physics behind them has been understood for well over half a century. We have been doing experiments on stimulated emission for at least a couple of decades. We don't have anything practical yet, but all of the physics is completely known. Again, you are arguing from ignorance, and nothing more. The entirety of United States has managed to build three devices in the 40s. And the technology has not changed much since then. Every single process that was used back then is still used now. The only advantage you get in modern times is better computers, which means that it will be slightly easier to design the shaped charges and lenses. It is still a monumental effort. Israel got a lot of help from United States. They are speculated to have assisted South Africa. North Korea practically had their nukes made by Russians. They certainly got a lot of raw materials for it from Russia. So none of these countries actually managed to build a nuke without help of either United States or Soviet Union nuclear program. Seriously, I'm a particle physicist. Up until May, I was doing research at Center for Nuclear Research at a major State-funded university. I am one of the people you are claiming has capability to build a nuke, or at least, have been presumably working with them. I'm glad to hear that you have so much faith in our capabilities, but it is totally misplaced. I've gone to conferences, spent some time studying theory at Jefferson National Laboratory, and my advisor collaborates with a team from Argon National Laboratory. I can tell you with absolute confidence that no public University has capability to build a nuclear bomb. There are a handful of teams at National Laboratories that can, because it's their job.

"Nearest" isn't the factor. It's about the strongest pull, and Sun's pull becomes dominant much sooner.

Not entirely correct. While you can make a nuclear battery that relies on spontaneous decay, this is boring, and not the focus of research. The whole point of using nuclear isomers is that they have stimulated emission modes, in which they release energy at a far greater rate. We are talking hours instead of decades. This lets you control the rate of power output, or even turn it off almost completely. This is also what makes them far, far safer than RTGs.

You are confusing age of something and time. Time is just a coordinate, and you can measure it any way you like. Age of something is absolute. It's the frame-invariant distance along that something's world line. Also known as proper time. That's what a watch is going to measure. The problem is, two different watches that traveled two different trajectories can end up showing different time. E.g. twin paradox. So you can't use a watch to establish unambiguous coordinate system with unambiguous time. But that doesn't make age of one particular watch any more ambiguous. We can also loosely define age of a particular point in space-time as the longest trajectory from that point to Big Bang. That distance from right here, right now to the Big Bang is what we usually refer to as the age of the universe. Which is very anthropocentric, but given the way space-time is, there isn't really a better way.