Might be going rather off topic, but despite the mind boggling difficulty of interstellar travel when viewed in a single human lifetime, When considering the search for extraterrestrials the troubling problem is how mindboggly easy it appears.Even at a thousandth of c. an exponentially growing civilization should have been able to colonize every star in the galaxy about a hundred times over. The time to stop and colonize each world become irrelevant due to the rapidly growing number of worlds willing to engage in the next wave. It strongly suggests we are entirely alone, or worse, the unknown hurdle is still before us and our chances of surviving to achieve 1000th of c. are very slim indeed.
I think constant acceleration at 1g is a nice well defined problem despite the various reasons we probably wouldnt attempt it.On topic, it could be worth noting that constant 1g acceleration would be pretty easy for a standard chemical rocket if there where depots strung out at just the right positions and velocities ahead of it.. of course that just pushes the problem onto how to get the depots there, but perhaps you have more options for unmanned depots than for a crewed ship. They could be shot with massive acceleration or take centuries to align.
Absolutely correct, sadly. Even assuming a wholly robotic, Von Neuman machine civilisation or post-Singularity ex-biological one (is there a difference?), it takes a reasonably short time to colonise an entire galaxy with rather slow ships. If you can colonise a galaxy, then you almost certainly manipulate the environment, increasing dust, decreasing dust, changing the percentage of stars with high metallicity, altering stellar rotation rates, emitting gravity wave signals and so forth.
What if it's only mankind's arrogance to assume that we can predict what a more advanced civilization's signatures would be? they'd have to do this and this and this and have this or that... how in the heck do we know that?
Quote from: KelvinZero on 06/24/2014 09:02 amI think constant acceleration at 1g is a nice well defined problem despite the various reasons we probably wouldnt attempt it.On topic, it could be worth noting that constant 1g acceleration would be pretty easy for a standard chemical rocket if there where depots strung out at just the right positions and velocities ahead of it.. of course that just pushes the problem onto how to get the depots there, but perhaps you have more options for unmanned depots than for a crewed ship. They could be shot with massive acceleration or take centuries to align.Isp is WAY too low.The total mass of chem depots needed even for a small craft to reach any sort of interstellar-class speed is not feasible. Billions of tons.
one reason this may be a false paradox is we might not even be able to perceive or recognize the signatures of such civilizations. for example; what if such civilizations use slightly larger than plank length wormholes to spy on planets rather than go to all of them? there are cosmic ray signals that would be the only signature of such virtual probes. according to Dr Kramer there are cosmic ray events that would match the signature of such probes. this would not ordinarily bring to mind alien activity. how would we know the difference between natural cosmic ray signals and wormholes spying on us? What if it's only mankind's arrogance to assume that we can predict what a more advanced civilization's signatures would be? they'd have to do this and this and this and have this or that... how in the heck do we know that?
Quote from: gospacex on 06/24/2014 09:53 amQuote from: KelvinZero on 06/24/2014 09:02 amI think constant acceleration at 1g is a nice well defined problem despite the various reasons we probably wouldnt attempt it.On topic, it could be worth noting that constant 1g acceleration would be pretty easy for a standard chemical rocket if there where depots strung out at just the right positions and velocities ahead of it.. of course that just pushes the problem onto how to get the depots there, but perhaps you have more options for unmanned depots than for a crewed ship. They could be shot with massive acceleration or take centuries to align.Isp is WAY too low.The total mass of chem depots needed even for a small craft to reach any sort of interstellar-class speed is not feasible. Billions of tons.No ISP is not relevant in this example. The catch is that you have gotten all these depots up to speed ahead of you somehow. Thats where you have to put all your energy in. The chemical rocket becomes just a way of taking this energy from the depot and putting it into the vehicle. You could just bounce off each depot and steal their kinetic energy that way, but that would be a rough trip.
Nah, I was clear that the depot was not launched by the same means, or by explained means at all. It was just to give ideas, not a solution.
Quote from: KelvinZero on 06/25/2014 10:59 amNah, I was clear that the depot was not launched by the same means, or by explained means at all. It was just to give ideas, not a solution.So what is "chemical" about this scheme?
And what if there are lots of altered galaxies? Would we recognize them as artificial rather than just a different type of galaxy? We could have already seen them and they are simply not recognized.
Quote from: Stormbringer on 06/24/2014 06:00 pmone reason this may be a false paradox is we might not even be able to perceive or recognize the signatures of such civilizations. for example; what if such civilizations use slightly larger than plank length wormholes to spy on planets rather than go to all of them? there are cosmic ray signals that would be the only signature of such virtual probes. according to Dr Kramer there are cosmic ray events that would match the signature of such probes. this would not ordinarily bring to mind alien activity. how would we know the difference between natural cosmic ray signals and wormholes spying on us? What if it's only mankind's arrogance to assume that we can predict what a more advanced civilization's signatures would be? they'd have to do this and this and this and have this or that... how in the heck do we know that?Maybe you are in a vat with neural feed sending you fake picture of the virtual reality. How in the heck can you know that?See? Not a useful position.
Since no one else seems to have run the numbers, let me do that. <SNIP>Now suppose you want to go exactly 27,000 light-years to the galactic core. I'll only do the 1g figuresShip time: 19.8 yearsEarth time: 27,002 yearsPeak velocity about 77 cm/sec less than c.Assuming a perfect anti-matter drive (exhaust is light-speed and all in the right direction), then the mass fraction for the 1g trip is 39.5. That is, for every kilo of payload delivered to Alpha Centuri, you would need 38.5 kilos of fuel (half matter and half antimatter). For the 0.1g trip, that falls to 3.7 and it's only 1.5 for the 0.01g trip.For the trip to the galactic core, it's about 777 million, so funding may be difficult. :-)Source for formulas: http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html
Quote from: Greg Hullender on 06/22/2014 12:19 amSince no one else seems to have run the numbers, let me do that. <SNIP>Now suppose you want to go exactly 27,000 light-years to the galactic core. I'll only do the 1g figuresShip time: 19.8 yearsEarth time: 27,002 yearsPeak velocity about 77 cm/sec less than c.Assuming a perfect anti-matter drive (exhaust is light-speed and all in the right direction), then the mass fraction for the 1g trip is 39.5. That is, for every kilo of payload delivered to Alpha Centuri, you would need 38.5 kilos of fuel (half matter and half antimatter). For the 0.1g trip, that falls to 3.7 and it's only 1.5 for the 0.01g trip.For the trip to the galactic core, it's about 777 million, so funding may be difficult. :-)Source for formulas: http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.htmlI assume that you're talking constant acceleration without midpoint turn over and deceleration. In the case of the 1g acceleration, I would figure that it would take about 4 as long objectively, as you'd never reach peak velocity, but only about half of that. Unfortunately, I don't have the formula to figure out the time dilation subjective for the ship. I figure at best, they'd reach about .5c in velocity.
well, the borehole however was a straight drilled hole downwards. If we mine like an inverted pyramid, we could go much further, without the rock pressure problems (although atmospheric pressure itself will get stronger.
... You are pushing directly against the moon for the whole trip......The big problem I see is what sort of beam you can focus on that range?