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Neither horses nor cars are propelled by the physics of the rocket equation. The rocket equation is an exponential (or a logarithm, depending on which way you arrange it). It provides a hard limit on performance that cannot be hand-waved away. You say, rightly, that future technologies can perform better. This is true. How much better? What are the numbers that we can plug into the rocket equation in order to compare to the other numbers that we can plug into the rocket equation? It is only then that we can really get a sense for the scale of how much better future technologies can be.
Ironically enough quiet_NaN doesn't actually do that, he just gives general exposition about the difficulties of spaceflight. Misleading, in my view, since energy density is vital, that's the fundamental essence of the entirety of rocketry. Nuclear fusion based rocketry would not just 'help a bit' but provide enormously greater capabilities.
We all agree that nuclear rockets are far more effective. Trying to plug in numbers to the equation is useless at this phase because we don't know how heavy a fusion rocket will be, nor what kind of exhaust velocity can be achieved. We don't have any such rockets. But we do know that chemical rockets are extremely slow and inefficient. They're unsuitable for serious space colonization (as are human bodies in my view).
Stepping back and taking a very broad view, there are several steps to the research, development, and engineering of a system. Generally, one begins with physical principles. With those physical principles, one can compute theoretical limits. One can also sketch a concept of operation based on those physical principles. Often times, at that point, one can still handwave away many practical concerns and compute how close a concept could, in theory, get to the raw theoretical limits. As one progresses, one may include an increasing number of more real-world difficulties.
For nuclear rocketry, we are not building on a blank slate, as though no one has ever started down this path at all, as though we simply have no idea what the theoretical limits are or what the concept-based performance could look like (still handwaving away many practical considerations). People have been doing this work and publishing it for half a century.
Do you agree or disagree with this general picture?
I'm not agreeing or disagreeing, it's just not relevant.
I am saying these things:
Quiet_Nan was saying
Neither point matters in relation to my argument. I think we all know that fusion rocketry is difficult.
You are asking in response:
But that also doesn't really matter to my point. As long as it's significantly better than chemical rocketry, which it is, then that makes it a better option for long-range spaceflight, since it can do the work and chemical rockets can't.
I don't understand your somewhat patronizing approach of asking about concept-based performance. I don't need to cite a specific fusion design to know that fusion designs can provide much more capable rocketry. That's inherent given the nature of fusion vs chemical rocketry. We already know this. There is plenty of variance between designs and some may just not end up being workable.
Trying to explain specific impulse, thrust vs delta v to me is wholly irrelevant to the substance of what I'm saying!
Lets use another one of your examples. Cars are much better than horses. Does that imply that cars are a better option for long-range spaceflight? If you think this statement doesn't quite make sense, try to explain without reference to any first principles, conceptual designs, concepts like specific impulse, thrust, and delta-v, etc.
Alternatively, to hone in really narrow:
How do you know that it can do the particular type of work you're asking it to do? Wouldn't it be nice if you had some reasoning, from first principles and/or conceptually, which could inform you as to whether it is plausibly up to the type of task you're asking of it? Some sort of check to see if you're accidentally expecting a car to go to the moon, just because it's better than a horse?
You know what's even better than first principles reasoning? Already knowing the answer. I already know that fusion rocketry designs can perform long-range spaceflight, to the edge of the solar system at least without being restricted to tiny payloads. You can do a quick internet search if this is new information to you.
Ah, so you think that there is something to be looked at in terms of designs, and at least something about distances/payloads, yes? And you think that this information can be found and understood with just a quick internet search? You just think that these internet sources don't use first principles reasoning, conceptual designs, concepts like specific impulse, thrust, and delta-v, etc., I guess. Those things are wholly irrelevant to your point. Am I understanding you correctly?
What are you even saying? Instead of taking the experts at their word, we should debate the physics of fusion rocketry as amateurs (a technology that doesn't even exist yet)? The whole point of having experts is to establish facts so I don't have to.
What are you even disagreeing with me about? Do you think fusion rockets can't reach the outer planets, can't provide significantly more utility than chemical rockets? If so, then you're wrong. If not, then you're wasting time nitpicking.
Frankly, I was saying that your prior comments are basically incoherent.
...lol, you don't know what my profession is.
Look, I didn't want to wave credentials around, but the reason why I got into this discussion is because you were showing that you are ignorant of the physics involved. What I'm arguing is that you need to learn a little bit about it before you make claims about it. Especially before you make dismissive claims where you say that we don't even need to consider the physics involved. That we don't even need to think about concepts like the rocket equation, specific impulse, thrust, delta-v, etc.
My claim was that we already had pretty decent published literature on various not-yet-existing propulsive methods, that this literature uses the standard physics and the standard methods of analysis and standardized performance metrics. You were saying that we should just ignore all that. That it was wholly irrelevant.
Nah, dawg. You need to have a basic understanding of the domain you want to speak on. If you're going to now agree that we can go look at the published literature (at least I think this is what you want to go for; you just called out an "internet search", so maybe you're going to crackpot sites) and that doing so is not wholly irrelevant, then one requires a sufficient understanding of the basic physics and terminology to have any clue what it is, and is not, saying.
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