Space travel

In My Humble Opinion
21

3d circuitry. Lower clock speeds. Both would reduce the power requirements and size immensely. No smaller silicon patterns needed.

In any case, a starship would have plenty of power - lithium or boron fusing with hydrogen gives you charged particles at several % of the speed of light you can convert directly to electricity.

Uploading is a misnomer. Again, it’s firmware theft through reverse engineering. You only need an approximate synaptic map of a human brain to do this, and the resulting AI would use a simplified model for each synapse. It would produce an intelligence that might have certain “personality” traits from the original but would differ immensely from the original and would probably be unable to access the original’s memories.

22

3D circuitry would have the same amount of chip surface, just spread over a smaller footprint (and increasing the difficulty of cooling it.) Lower clock speeds means slower calculations means more chips needed to perform a certain task (if speed is essential-- maybe the “uploaded” people won’t mind running at a small fraction of realtime.)
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That’s more hand-waving from you–just have fusion! And the output of a fusion reactor wouldn’t be “converted directly to electricity”, it would be used to boil water, which will turn a turbine, which will generate electricity.

Assuming that consciousness works that simply. And it might. But it might not. And trying to reproduce consciousness merely by simulating a pattern of neural connections might be as effective as Pacific Islanders building bamboo “control towers” to try to attract cargo. We simply do not don’t know yet.

23

Some previously threads on the topic of interstellar space travel:

[THREAD=538092]is interstellar travel by embodied humans even possible?[/THREAD]
[THREAD=711782]If cost were no object: Interstellar travel[/THREAD]
[THREAD=719753]Do you think humanity will ever become a interstellar civilization[/THREAD]
[THREAD=18253699]Is there ANY realistic mode of interstellar travel?[/THREAD]
[THREAD=596543]What will the first interstellar probe be like?[/THREAD]

Setting aside the issues about the biological and social issues of “generation ark” concepts, there are two basic problems with propulsive space travel by embodied humans with any foreseeable technology, addressed in some depth below.

One is energy; we simply have no way to produce sufficient energy for a closed system for the required durations of many thousands of years. Even if we posit some advanced very high specific impulse propulsion system (I[SUB]sp[/SUB]>100,000 seconds, which is about half an order of magnitude beyond all but the most speculative proposed technologies, and two orders of magnitude beyond any currently workable propulsion system) we’d still be looking at a transit duration of hundreds of years to the nearest star systems. Setting aside whatever energy would be needed to power the propulsion system, the amount of fuel we would need to maintain a closed agricultural and hydrological cycle to sustain something like an Earth-like environment would be an enormous payload, and the required reliability of power generation and the associatiated environmental control and life support would be almost incalculable. We don’t typically think of the power needed for basic life systems as being all that important because for short space ventures to Earth orbit or to the Moon we eat prepackaged food, recycle or expend waste water, and have solar power readily available for heating and cooling (the latter actually being the more significant problem) but for a journey of more than a few months prepared foods and not completely recycling vital resources like water and bioactive minerals is not practical, and in interstellar (or even distant interplanetary) space, the solar energy that powers nearly all processes on Earth (other than the atomic decay powering most geological processes and nuclear fission using processed fissile fuels) is just not available.

The other problem is related, albeit so prosaic most people–even scientists and engineers–don’t really think about it at first; even if we could produce all of the needed energy to drive hydrological cycles, grow crops, provide a comfortable environment, et cetera, we’d be left with the problem of excess waste heat. All work-performing and power generation processes produce “waste heat” (thermal energy that cannot be made to do useful work and that has to be rejected into a cold temperature reservoir in order to maintain thermodynamic equilibrium in a closed system). That may not seem like it should be a big deal because space is ‘cold’; that is to say, the temperature of the cosmic microwave background is ~2.7 Kelvin (just above absolute zero) and in deep space there are essentially no sources of external heating. However, because there is no medium to carry away heat as their is on Earth–no rivers, lakes, oceans, or virtually unlimited sources of water to use in evaporative cooling–all heat rejection has to be done via radiation, and radiation can only be done with outward facing surfaces. This means that for an energetic system you need very large radiative surfaces and all of the associated heat exchange systems to convey excess interior heat to the radiators. For any practical closed lifesystem which is internally powered by something like nuclear fission or any foreseeable form of nuclear fusion this would become an enormous amount of mass. Even if you put the power generation system outside the vehicle it still has to be cooled, or else it will accumulate enough excess heat that it will disrupt the thermal cycle or exceed material limits.

So, in order to send human animals to another star system, we’d need some kind of propulsion system that is leaps and bounds ahead of the best systems we currently believe may be practicable in the foreseeable future, and a power production and waste heat management system that is thermodynamically more efficient than anything we can conceive of even in the wet dreams of thermyodynamicists. Practically speaking, without some kind of technomagical “warp drive” or space-folding wormholes or some other conceit of science fiction, the notion of sending people to explore and colonize other worlds is beyond any plausibility. There are, of course, theoretical possibilities for the above, or at least, they aren’t fundamentally prohibited by physics as we currently understand it (provided we are willing to accept the existence of some kind of “exotic matter” with no current basis in empirical science), but we have no way to even begin to develop such technologies at this point even if we had access to virtually limitless technology.

On the other hand, sending autonomous probes to investigate the outer vestiges of our solar system (the Kuiper Belt and the Oort Cloud) and even flybys to nearby star systems is not beyond conception. With advances in machine intelligence and self-repairing biological-like systems (perhaps even incoroporating elements of Earth biology) it is just plausible that we might be able to launch exploratory missions to stars in the immediate interstellar neighborhood within the time frame of a century or perhaps even sooner. Such missions will still take hundreds of years to complete, and the required reliability and power to transmit telemetry back to Earth are daunting issues, but one can propose a development path to support such a capability.

As for needing to go to other star systems, there are vastly more resources in our system than we could use now, and even positing a major expansion of humanity into space we could spend hundreds of years of development before running into the kind of resource limits we are currently experiencing in mining the top few kilometers of the Earth’s surface. If we could just bore down deeper into the crust, or extract minerals from the mantle, we would have a virtually limitless supply of every industrially useful metal, but that is almost as science fiction as going to another star system, whereas extracting resources from Near Earth Asteroids and other periodic solar-orbiting objects is only very, very challenging. Both the material wealth and opportunities for scientific exploration in our own solar system are vast; even with only eight planets, we could spend millions of person-years of effort in exploration and still only scratch the surface of the fascinating things about our solar system while awaiting revolutions in physics that might permit some kind of practical interstellar transit, or developments in biological technology which make humanity (or a post-human civilization) capable of surviving interstellar journeys of thousands of years.

Stranger

24

Ooh, chronogami! I want a swan, please.

[sub]You have now seen the full extent of my knowledge on any of tis stuff…[/sub]

25

**

That’s more hand-waving from you-- And the output of a fusion reactor wouldn’t be “converted directly to electricity”, it would be used to boil water, which will turn a turbine, which will generate electricity.

Assuming that consciousness works that simply. And it might. And trying to reproduce consciousness merely by simulating a pattern of neural connections might be as effective as Pacific Islanders building bamboo “control towers” to try to attract cargo. We simply do not don’t know yet.
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Humans run at a clock speed of 1000 Hz. So that’s what you’d shoot for in an AI designed to save power and run in realtime. There is a nonlinear relationship between clock speed and waste heat - running at 1 khz instead of 4 ghz saves an immense amount of power and thus reduces waste heat. The AI would need just as many equivalent circuits as a human has synapses in the brain. So there would need to be thousands of square meters of chip area - the processor would be basically a cylinder or cube with thousands of layers to get that kind of area.

Don’t accuse someone of handwaving when you’re unfamiliar with something. I was talking about aneutronic fusion. It requires hotter, higher pressure plasma, but the products are almost exclusively charged particles. I am sure that Stranger will no doubt agree with me it’s the way to go if you want a high ISP engine with any thrust - because the output of the reaction is almost exclusively charged particles, it is possible to arrange the magnets in your engine to send all of them away from the walls of your engine.

That in turn greatly reduces impingement and damage to the engine and waste heat produced. Less waste heat means you can run the engine at a higher burn rate, increasing thrust. (probably by orders of magnitude for the same amount of radiators)

Charged particles can be converted to electricity directly, as mentioned above, through direct conversion. No steam, no boiler.

The difference between current results - AIs that are built on simplified architectures borrowed from biology - and the pacific islanders - is that we are getting results. The islanders never got so much as a Cessna to land. We’ve gotten AI to recognize images and beat human judgement on some tasks. To say we can’t eventually use the same techniques to reach whatever “consciousness” is is a tenuous bit of logic. The evidence says that it’s just a form of higher level processing done by sending the outputs of lower level neural networks that produce more abstract outputs to higher level networks. Or, to use an example you are familiar with, the language of “consciousness” is just another Chinese Room. There are rules. An abstract idea comes in, and a different abstract idea comes out by a set of rules encoded on the slips of paper in the room. And the brain is a few thousand of these Chinese Rooms cascaded on each other. Copy all the rooms and you definitely get consciousness.

Simplify each room, but build them of higher quality circuitry than the brain uses, and give them the equivalent of thousands of years of experience, when humans develop consciousness in a few years, mostly spent sleeping, and it’s actually reasonable to expect behavior comparable to “consciousness” from an AI. (just like the Chinese room - the AI may not actually be conscious, but it would be able to give the same responses as if it were, so…)

26

Yep, a mere 6.6 billion degrees C. Only 440 times the temperature at the core of the sun. And you think that humans will build a device that can produce those conditions and keep it running for the hundreds or thousands of years it would take a generation ship to travel interstellar distances. That isn’t handwaving at all.

Can I have your phone number? I’m actually a Nigerian prince, and I think that you can assist me in getting some money out of a bank account.

27

Credible physicists, which you are not, think it can be done. It’s about 1000 times hotter than existing fusion research reactors, which is a challenge but not what you are making it sound like.

And i’m not talking about generation ships. Obviously, those are stupid.

And it is abundantly obvious that you would need a technology that allows you to take any component of your starship (there would need to be redundancy obviously, so you can do this), convert it to plasma, and rebuilt it atom by atom. There are ways to do this and the human body actually does this (with the help of other organisms in the environment for some steps), so this is solid, credible science. I could explain in detail precisely how, but I doubt you would listen.

So the starship would be perpetually rebuilding itself, as things fail, robots would be retrieving the failed modules and reconstructing them. So at any given time, no part of the ship would be more than a decade old or so.

This is why the crew must be AI and not humans - the computers the AI uses would fail like everything else. (gradually and with error correction). So the computers get rebuilt from scratch periodically, module by module. No knowledge is lost.

It’s only speculative in that we can’t currently do it today, but all evidence says it is achievable. It’s not the same kind of speculation as something like “warp drive”, where no evidence says you can do this.

28

Yes, and it is always 20 years in the future. (For the “easy” fusion, not the much, much harder kind you are talking about.)

Generation ships are the least stupid of the ideas for interstellar ships. If you are talking about fast ships–ships that are capable of traveling interstellar distances in less than a generation–then you are beyond delusional.

29

Oh, the near term attempt to reach that goal : Tri Alpha energy istrying it. Now, they may fail. And they probably won’t commercialize it by 2027 even if they succeed. But as I understand it, the math checks out. The apparatus they are building will reach the 4 billion degree target on paper. Maybe the plasma will develop a new, previously known instability, or maybe that mountain of high end equipment will just cost too much. But since it already works at temperatures for D-T fusion (which is uneconomical due to producing it’s energy as heat), there is reason to think this is going to work.

And at this point I’m just going to stop arguing with you, all you are doing is repeating ignorant cliches.

30

Oh, I agree that each of us is arguing with someone that the other believes to be deeply ignorant about the real world.

31

Ok, so your arguments assume :

Static technology. Humans will not develop anything that we know is possible now if we haven’t made any significant progress on it over your lifetime.

Specifically, :

a. Fusion
Over your lifetime, the last 30-50 years, we have not made much progress towards fusion. We goddamn know it works - all forms of it, including the aneutronic kind, and it works great in small lab devices for a neutron source and of course in bombs.

But you believe that over the 200+ years it will probably take to develop starships, no further progress will be made.

b. Artificial Intelligence
Over your lifetime, we have made enormous progress towards AI. But, it turns out, it’s a much bigger problem than people thought it was in the 1960s. So even though computers can now recognize speech, images, drive cars (thought impossible just a decade ago), and predictively access most of human knowledge instantly, well, AI or consciousness…that’s too advanced.

And even though we have a biological example of a computer that uses 10 watts and weighs a kilogram and is sentient, there’s just no way in 200 years we’ll find a way to make a computer in the same specs that is sentient we can cram on a starship.

c. Mammalian Life Extension

Admittedly, over your life, the progress in this area towards adults is essentially zero. We don’t know exactly what is wrong. We decoded the genome and can make arbitrary peptides in the lab now, but it turns out there may be additional levels of data storage in cells we can’t quite decode yet. Until we read all the memory in cells and can really compare human cell samples taken at different ages from the same organ, we won’t be able to figure out what aging even is.

Now, we did figure out that it’s just programming. We’ve taken cells from adult humans and rolled them right back to stem cells, and they are young again. So we know it’s possible, but we probably will not achieve any feasible way to do this while you are alive.

Also, we know that since other mammals live a lot shorter lives, reprogramming us to live much longer lives is probably possible.

Conclusion : you think you’re going to be dead before any of the stuff we’re talking about matters. So in a way, you’re right. In the reality you will live to see, none of these things are real.

32

Sadly, we’re still mostly the angry, hateful, spiteful, covetous and greedy hairless apes that we’ve always been.

Until that changes, the global effort required for interstellar travel is probably not going to happen. Too busy trying to figure out better ways of killing each other.

33

IMHO, God did not leave us stranded, and we will be ‘spaceborne’ as in Rev 12:1-5, the birth of the body of Christ into the heavens (outer space) as us parts of the body of Jesus (1 Cor 12:27).

Warp drive of some sort (hyper, jump, improbability, etc.) is our destiny.

34

I thought you were going to give it up? All I’m seeing is angry space cadet is angry.

35

Keep the snarky comments out of here.

36

I’d say technically no depending on point of view

It is a non return mission, if you find no place that is livable, well eventually the trip is over. you can not live in a space ship forever, eventually you have recycled everything so much there is nothing left.
Also, it’s one of those “If anything breaks you’re F’d” things
Make it out past the solar system and lose engines, “Say good night Gracie”
Have any kind of major mechanical or structural failure and game over, no intergalactic tow truck to come tow you home.
We know moving objects in our own little corner of space, out there though? You could get plowed by a chunk of something that comes out of no where, or get blasted by some
burst of radiation making its way across the universe etc.

And lots of other things.

So yea i would say most people will call it suicidal for a very very long time.
Going to the moon was a suicide mission to most people at the time.
You asked would it be considered suicidal, not would it be impossible.

37

I for one highly doubt it, we are stuck on this planet a long long time. The distances to travel are incomprehensible, the energy required is immense beyond belief.

38

Isn’t it speculated that if the em drive works as advertised, that we can make it to Alpha Centauri in about 100 years?

39

Well, playing with some numbers, to get to Alpha Centauri in 100 years by accelerating all the way to the midway point, flipping over, and decelerating the rest of the way, the drive would have to provide 0.00167 Gs of thrust (or around 0.0164 m/s[sup]2[/sup]. Maximum speed at the midway point would be 25,752 kilometers per second (around 57.6 million miles per hour.) **

A Newton is the force needed to accelerate 1 kilogram by 1 meter per second squared. The Alpha Centauri ship would need to provide 0.0164 Newtons per kilogram of mass. The NASA experiment with the emdrive showed a thrust of 0.0012 Newtons per kilogram of mass per kilowatt of **electricity used. So if these results are real and not experimental error, maybe 10 to 15 kilowatts per kilogram to reach that level of acceleration? Call it 10 for ease of math.

I have no idea what the minimum mass for a manned ship traveling 4.3 light years and for 100 years would be, so I’m just grabbing the estimated mass of the completed ISS (which is probably **far, far **too small.) That is 419,600 kilograms. So to accelerate the ISS at .00167 Gs would take around 4.2 gigawatts of electricity. That’s 3 and a half Delorians worth, and more than the biggest nuclear power station in the US.

tl;dr: Probably no need to hold your breath.

(Disclaimer, I acknowledge that I could have utterly screwed up my math at some point along the way.)

40

You might as well speculate about the propulsive efficacy of flying monkeys. To date, the EmDrive concept has not been irrefutably shown to actually work (yes, I’ve read the updated NASA Eagleworks AIAA paper, and I am still of the opinion that there are substantial methodological errors that could produce the observed effect), and even if it does represent a new loophole in our understanding of momentum that would allow propellantless thrust, the specific power requirements may be prohibitive for anything beyond satellite stationkeeping. The other issues with maintaining a closed system for decades and the fundamental thermodynamics problem of dealing with waste heat still remains.

Stranger