I believe I have read that in space keeping a particle beam together is harder than a laser. in an atmosphere the bloom of a particle beam is partly mitigated by the surrounding atoms and molecules of the atmosphere. in space the electrical charges of the particles in the beam will repel each other and the beam will spread out. However i have also read an article some time back about a lab successfully creating a magnetically jacketed plasma in which case the particle beam could conceivably be kept together by such a jacket.http://www.sciencedaily.com/releases/2013/04/130416151931.htm
Even if this is very interesting, I thing that solving constant 1G acceleration for interplanetary transport need to be solved before talking of 1G constant acceleration for interstellar transport
I was thinking of a few ideas like this. Perhaps the goal should not be to create a plasma ring that remains compact across from projector to ship but instead a very faint, very large plasma lens halfway between the projector and the ship. One thing you will have in abundance is space! My guess is that at best the particles would not converge back to a single point but more of a line along the axis, but a collector extended along an axis would be far less massive than a collector disk of similar scale. (I haven't thought much about what configuration such a lens would require, let alone its shape evolving correctly during the ships entire flight.)
Quote from: KelvinZero on 06/22/2014 02:05 am 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.That involves quite a few assumptions...-maybe most intelligent species are in environments where developing spaceflight tech is unlikely (say, the majority of living worlds are Europa/Enceladus type, under ice, and they never even learn that space exists) or lack hands (say, dolphins or ravens or parrots become sapient instead of primates)-or, maybe developing significant technology is simply rare (most of the human race's history was spent as hunter-gatherers)-or, maybe most intelligent species don't have a 'drive to explore' and never get beyond the continent they originated on, much less into spaceIMO we don't even know enough for the "Fermi Paradox" to be a meaningful problem.EDIT: also, I don't think having the technology for interstellar travel implies exponential expansion through the galaxy, by a long shot. We aren't really colonizing the oceans or turning them into giant farms (eg Arthur C Clarke's "The Deep Range") though we totally could, or trying to turn the deserts into farmland, etc. --- because agricultural technology has more than kept pace with population growth*, and population densities are becoming higher with urbanization. We don't really need more room. Moon or Mars colonization will be driven "because it's there" if it happens IMO, by people like Elon Musk who are visionaries, rather than by pure economics.*And most first world nations have below replacement birthrates, the 'demographic transition'. So assuming exponential growth for high tech civilizations doesn't seem supported by the one example we have - ourselves.EDIT x2: Also, the universe is huge. Even if we really are the only sapient species in the galaxy or the Local Group, there could still be a huge number total (universe-wide). At say 1% of c there might not have been time to colonize from distant galaxy clusters.
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.
Quote from: luinil on 07/03/2014 07:10 amEven if this is very interesting, I thing that solving constant 1G acceleration for interplanetary transport need to be solved before talking of 1G constant acceleration for interstellar transport Very rough math I tried to do in what's left of my brain, but, at closest approach, I'm getting a little less than two days to Mars (including slowing back down) at 1g.
Also, fusion and anti-matter is not "unproven physics" rather as methods of propulsion and power generation they are unproven engineering. Mag-sails actually work they just aren't as efficient as we would like them to be for the purposes of "mag-beam" propulsion. On the other hand we don't even have a working fusion reactor yet and if we had one it would still be more efficient in terms of thrust to mass ratio for interstellar travel to probably use something like Focus Fusion to generate a charged particle beam for beam propulsion purposes. Fusion is great for interplanetary distances but you need to stretch your fuel paycheck even more for interstellar distances. We could build a probe sized vehicle powered by an anti-matter sail but the costs to produce enough antimatter for an interstellar flight of such a vehicle would be pretty high.(although, perhaps not insurmountably so)
There are magnetic and electric ion and electron lenses. But the designs I've seen are sensitive to particle charge/mass ratio and energy. Making a system that can focus the ion and electron components of a plasma beam to a common point strikes me as likely non-trivial.
well i read an article a few months ago about a new record of antimatter production and a scheme to provide antimatter samples to (off the production site) labs around the world as a result. it turns out the "trillions of dollars per gram" thing is bunkum. one of these production machines can do a gram a year. and these things are small. like nearly refrigerator sized. so there is no reason not to have hundreds or thousands of them.
Quote from: Stormbringer on 07/03/2014 08:12 pm well i read an article a few months ago about a new record of antimatter production and a scheme to provide antimatter samples to (off the production site) labs around the world as a result. it turns out the "trillions of dollars per gram" thing is bunkum. one of these production machines can do a gram a year. and these things are small. like nearly refrigerator sized. so there is no reason not to have hundreds or thousands of them. Nonsense. Nothing on the boards could even dream of producing a gram of anti-matter.
Holy Poop! i don't know how i missed the most significant implication of this whole story! the number of positrons made per shot? 6 orders of magnitude more antimatter production than the previous record. back of the napkin calculations seem to indicate that with the extremely short pulse lasers you could potentially create over a gram a year with just one machine. EDIT! actually thats not a year! it a little over a minute to make a gram and just short of a year to make enough to power up an alcubierre warp drive. now that assumes that a quadrillionth of a second laser pulse would produce the same number as the pulses they used in this experiment. but if so... you know... there are some antimatter propulsion schemes that can do an entire mission on as little as one nanogram. for example AIMSTAR and ICAN proposals for hybrid systems. these schemes have been proposed for trips to the outer planets and as far out as the Oort cloud on a nanogram or a microgram of antimatter. Last edited by Darkblade; May 21st, 2014 at 7:00 pm.
here is the article:http://phys.org/news/2014-05-scientists-year-quest.htmland what i said about it in another forum will follow. now i probably cannot find where the 1 gram figure came from because i don't remember the forum where the discussion was held (its different from where i am posting the bellow quote) but elsewhere some thread participants posted calculations showing the quantities that could be produced.Quote Holy Poop! i don't know how i missed the most significant implication of this whole story! the number of positrons made per shot? 6 orders of magnitude more antimatter production than the previous record. back of the napkin calculations seem to indicate that with the extremely short pulse lasers you could potentially create over a gram a year with just one machine. EDIT! actually thats not a year! it a little over a minute to make a gram and just short of a year to make enough to power up an alcubierre warp drive. now that assumes that a quadrillionth of a second laser pulse would produce the same number as the pulses they used in this experiment. but if so... you know... there are some antimatter propulsion schemes that can do an entire mission on as little as one nanogram. for example AIMSTAR and ICAN proposals for hybrid systems. these schemes have been proposed for trips to the outer planets and as far out as the Oort cloud on a nanogram or a microgram of antimatter. Last edited by Darkblade; May 21st, 2014 at 7:00 pm.
Physicists Dr. Ryan Weed and Joshua Machacek conceived of a company that would enhance positron production and storage technologies during their doctoral research at the Australian National University. Bala Ramamurthy, Dr. Sean Casey and Mike Barrucco – engineers with experience in aerospace engineering projects, scientific equipment development and project management joined the Positron Dynamics team in 2012. Breakout Labs, part of the Thiel foundation, provided initial funding for their efforts in 2012. Positron Dynamics has patents in positron moderation techniques.
Producing anti-matter at 1 gram per minute would allow you to create a 43 kiloton bomb every minute.At least 6×10^12 W of power would be required to do this assuming 100% conversion efficiency. That's 6 TW!I can't imagine this to be feasible.Well, I certainly hope it's not feasible for all our sakes...