Outsider Posted January 19, 2004 Report Share Posted January 19, 2004 Is it 40% by 0.5 C? dang! I thought it grew -much- more slowly until up around 0.9 C, where it really took off. Quote Link to comment Share on other sites More sharing options...
Victor Posted January 19, 2004 Report Share Posted January 19, 2004 Propelling us Towards the Future is another link that might be of interest. It doesn't deal so much with alternative propulsions, as with alternative fuels for conventional rockets. Still a good read for a low-rubber setting. Quote Link to comment Share on other sites More sharing options...
Snarf Posted January 19, 2004 Report Share Posted January 19, 2004 Originally posted by L. Marcus I've been fiddling with this for a SF-campaign, and technobabbled it as a result of deflector screen technology. Really rubbery, you know . . . Well, the technology is rubbery, but the theory is real. In that way, it's no more rubber science than fusion drives. Quote Link to comment Share on other sites More sharing options...
megaplayboy Posted January 19, 2004 Report Share Posted January 19, 2004 Originally posted by Outsider Is it 40% by 0.5 C? dang! I thought it grew -much- more slowly until up around 0.9 C, where it really took off. well, opening up the creaky part of my brain that contains my physics knowledge, and dusting off the book marked "relativity equations": M®= M(0)/SQRT((1-(v^2/c^2)) so, m(0) divided by the square root of .75(about .85)--oops, my bad, actually about a 15-20% increase in relative mass(and the amount of propellant). There's also a slight time dilation, as well. Quote Link to comment Share on other sites More sharing options...
SSJ Archon Posted January 19, 2004 Report Share Posted January 19, 2004 Megaplayboy beat me to the Special Realtivity Formula, however here is the conversion factor for time dilation: SQRT(1-(v^2/c^2)) Therefore if your onboard clock says you travel for 1 year, and you have maintained 50% c, the equation is: SQRT(1-((299,792,458/2)^2/299,792,458^2)) SQRT(1-(22468879468420441/89875517873681764)) SQRT(1-1.6678204759907602478778835723746e-9) 0.99999999916608976165691673325435 Thusly, you will not have moved .5 Lightyears, you will have moved 0.50000000041695511951924477646966 Lightyears. Stupid big numbers. You all can do other numbers for your freaking selves! (I don't believe in rounding by the way.) Unfortunately, this all assumes that your V is constant. You can not take the average of your starting V and ending V either, because that is a linear system, and this is an exponential system. I'll look up how to do acceleration dilation. On the matter of Kernals, the energy is in the ergosphere, I'll admit that, however how are you going to get an appropirately sized black hole? Quote Link to comment Share on other sites More sharing options...
McCoy Posted January 19, 2004 Report Share Posted January 19, 2004 Originally posted by megaplayboy umm, has anyone factored in the relativistic effects? In this case, relavistic effects can pretty much be ignored under .75 c, and time dialation effect on the crew can be totally ignored as the crew is going to be in suspended animation anyway. Quote Link to comment Share on other sites More sharing options...
Vondy Posted January 19, 2004 Author Report Share Posted January 19, 2004 For those of us who consider relativism a post-modern ethical conundrum and didn't take a great deal of physics courses in college (I'm good at math (at least through calc), but my main area of emphasis is the humanities!) let's start talking in plain languange Math is indeed a language, but its not a very effective one when you want to communicate in simply, easily understood terms. When we apply relativism to subluminal travel we are saying what? They get there sooner? They get their later (obviously not)? They get there in the same amount of time, but its perceived as being sooner by the people at their starting point? Help the Crim J major who is going back to school to study history and english comprehend this strange and magical language you are all communicating in Quote Link to comment Share on other sites More sharing options...
Dr. Anomaly Posted January 20, 2004 Report Share Posted January 20, 2004 The time dialation effect happens to the crew. In other words, suppose it takes 10 years to reach someplace with a near-lightspeed velocity. To the rest of the universe, it takes the ship 10 years to get there...for the crew, if they're moving close to c, then it will take less than 10 years; how much less depends on their inverse tau factor, which doesn't begin to climb drastically until you pass .96c, which is darn hard to do. Quote Link to comment Share on other sites More sharing options...
McCoy Posted January 20, 2004 Report Share Posted January 20, 2004 Originally posted by Von D-Man For those of us who consider relativism a post-modern ethical conundrum and didn't take a great deal of physics courses in college (I'm good at math (at least through calc), but my main area of emphasis is the humanities!) let's start talking in plain languange Math is indeed a language, but its not a very effective one when you want to communicate in simply, easily understood terms. When we apply relativism to subluminal travel we are saying what? They get there sooner? They get their later (obviously not)? They get there in the same amount of time, but its perceived as being sooner by the people at their starting point? Help the Crim J major who is going back to school to study history and english comprehend this strange and magical language you are all communicating in The closer you get to light speed, the slower time seems to pass. So to the crew, the trip would be shorter than to the folks back home. At .5 c, the effect is very small. difference to the crew and the folks back home would be a matter of weeks, not years. But it doesn't matter, because your crew is going to be in suspended animation. For them, the trip takes no subjective time, relavistic time dialation or not. Quote Link to comment Share on other sites More sharing options...
Outsider Posted January 20, 2004 Report Share Posted January 20, 2004 Ah, I was remembering the time dilation not being anything to really worry about until right near lightspeed. The mass increase starts getting significant a lot earlier than I thought though. Constant accelleration is so much easier to deal with in a quickie table with minimal calculating. If you're going for constant thrust, things get tedious. More tedious than I want to work out my hand, anyway. Maybe Lemming could modify his code But then, if he wanted to be really accurate, he'd need to know how fast the ship loses reaction mass, if it uses a reaction drive of some sort. Quote Link to comment Share on other sites More sharing options...
Farkling Posted January 25, 2004 Report Share Posted January 25, 2004 If you are already postulating magnetic field control, then I would go with a linear accelerator launch platform in free space, with a conventional onboard reaction mass engine for further acceleration and for landing at the destination, with a Bussard Ramjet. The major holdup on the usage of a Bussard Ramjet is the stabilization and control of the HUGE magnetic field needed to scoop in the feul. Bussard ramscoops will not funnel to the engine at sufficient speeds below 6% lightspeed (rubber science exception might be in dense cloud areas, those same clouds mitigate and require monitoring and contraction of the field at speeds over 10% lightspeed. 1) Launch platform: Linear accelerator near asteroid belt or pumped laser installation above the solar ecliptic 2) Onboard reaction motor for maneuvering / possible landing. A colony would want the ship intact and down for the resources. If travelling to a known area, ship requires manuevering motors only, and can be decelerated with linear accelerator or solar sail. 3) Ramjet comes online at 6% c and provides interstellar acceleration. They accelerate for half the trip, flip the ship (not the fields) and decelerate for the latter half of the trip. Footnote:: Ramjets can (theoretically) approach .99c given sufficient space and runtime...leading to a flying dutchman arrangement (there is an old Niven story about that, I think) Quote Link to comment Share on other sites More sharing options...
Outsider Posted January 25, 2004 Report Share Posted January 25, 2004 Are you thinking of Tau Zero by Poul Andersen? Quote Link to comment Share on other sites More sharing options...
Farkling Posted January 25, 2004 Report Share Posted January 25, 2004 Maybe. But I swear I remember a Niven story about someone taking a Bussard ramjet out to the edges of the galaxy...I'm sure Louis Wu makes a reference to it in a short story... Quote Link to comment Share on other sites More sharing options...
Intrope Posted January 25, 2004 Report Share Posted January 25, 2004 Originally posted by Farkling Maybe. But I swear I remember a Niven story about someone taking a Bussard ramjet out to the edges of the galaxy...I'm sure Louis Wu makes a reference to it in a short story... Probably 'The Ethics of Madness' (short story), involving a paranoiac who ends up leaving the galaxy entirely in a ramjet. He used Bussard Ramjets a lot; they play a part in Protector, The Gift from Earth, A World out of Time, and the Ringworld Trilogy. Quote Link to comment Share on other sites More sharing options...
xanatos Posted January 26, 2004 Report Share Posted January 26, 2004 Another possibility for low-rubber propulsion would be using kernels (Kerr-Newman black holes) as your power/propulsion source. Well, it's low-rubber if you concede the possibility of substellar-mass singularities... How much energy do you need to move this small black hole? You told that it's mass is in the hundreds of millions of tons... How much big will the engine be? --- bye Quote Link to comment Share on other sites More sharing options...
Dr. Anomaly Posted January 26, 2004 Report Share Posted January 26, 2004 Honestly, I'm not sure. It's been a while since I read The McAndrew Chronicles and I don't know if that was ever explicitly stated or not. Since you're most likely going to make an engine by accelerating a very small number of particles past the black hole and then shooting them out to propel the ship, probably not that big. Yes, that does mean you have to carry some ordinary matter for reaction mass, but you can get just as good an effect by accelerating a tiny amount of mass to ridiculous speeds as you can by accelerating much larger masses of matter to much lower speeds, this won't be a drop in the bucket compared to the mass of the hole itself. In any case, no matter your source of fuel and/or power, you're going to have to expend energy to move it; apart from matter/antimatter annihilation reactions, a black hole that can give up one half of its effective mass is probably the most efficient energy source you're going to find. And considering that it's very compact and self-containing (unlike bulk antimatter and matter reactants), it's going to be a LOT easier to handle (relatively speaking). There is a slight problem with radiation ( ) but since there's a similar problem with matter-antimatter, I don't think that weighs in as support for either one of those ideas. In any case, realisticlly speaking, if substellar black holes can and do exist (and that's a big 'if') they're probably much more usable as an interstellar engine/power source than a matter/antimatter reactor (as long as you're confining yourself to some kind of reaction drive vessel and not invoking 'warp drive' or some kind of reactionless drive that works directly on the fabric of spacetime itself). Quote Link to comment Share on other sites More sharing options...
Farkling Posted January 27, 2004 Report Share Posted January 27, 2004 James Hogan's old Ganymede Trilogy posited a drive involving two miniature black holes in a stable orbit within the engine mass. The rubber science includes gravity control though... Quote Link to comment Share on other sites More sharing options...
Dr. Anomaly Posted January 28, 2004 Report Share Posted January 28, 2004 Hmmm...I was under the impression that there were a LOT of micro black holes circulating at near lightspeed inside a magnetic confinement torus, not just two. It's been a while since I read The Gentle Giants of Ganymede, though, so I could be mistaken. And you're right, it does include not just gravity control, but gravity generation as well, which definitely makes it 'rubber'. Quote Link to comment Share on other sites More sharing options...
Guest Champsguy Posted January 28, 2004 Report Share Posted January 28, 2004 This is a suggestion primarily for D-Man. The rest of you can feel free to ignore the idiot with the History degree who never took any math past Pre-Calculus. I've read that NASA has been experimenting with superconductors to create what might be a field of reduced gravity. As of the last I'd heard, it was still hotly debated as to whether gravity was actually being reduced or if something else was happening. If your sci-fi setting features room-temperature superconductors, then perhaps you could incorporate a gravity drive extrapolated from this style. The idea would be to reverse the process that decreases gravity, with the engine located at one end of the ship. The rest of the ship is affected by the gravity, grows heavy, and "falls" towards the front of the ship (and whichever direction it's pointing). Voila, reactionless drive, and you can set your G acceleration at whatever you want (by increasing the field), limited only by the energy your fusion drive can produce. It's kinda rubbery, and I'm sure everyone else on this thread could give you a dozen reasons why it won't quite work, but to a social science guy like me, it works fine. Quote Link to comment Share on other sites More sharing options...
Dr. Anomaly Posted January 28, 2004 Report Share Posted January 28, 2004 Champsguy, I know (sort of) about the project you're talking about. I last read something about it over a year ago, and the details are more than a bit blurry. I *do* recall it had something to do with a disk made of one of those complex rare-earth ceramics that superconducts "only" at around -72 degrees. I seem to recall the (then) current theory behind it had something to do with causing all the spin of the particles in the plate to align, *somewhat* in the same fashion as happens in an Einstein-Bose condensate. And I seem to recall the person researching it was a professor at a university in either Alabama or George...I *think*. Like I said, kinda blurry. Is this the thing you're talking about? Quote Link to comment Share on other sites More sharing options...
Guest Champsguy Posted January 28, 2004 Report Share Posted January 28, 2004 Yeah, that's the one. The details are hazy for me, too. I think it's on Popular Mechanics' web page archive (or maybe it was Popular Science), but I can't remember. I know it involved discs of rotating superconductors, but that's about all I remember of it. Anyway, I figure in a future where that technology moves beyond the experimental phase, they'll find all sorts of nifty uses for it. Quote Link to comment Share on other sites More sharing options...
DrTemp Posted January 29, 2004 Report Share Posted January 29, 2004 Originally posted by Champsguy I figure in a future where that technology moves beyond the experimental phase, they'll find all sorts of nifty uses for it. [/b] You are talking about http://www.americanantigravity.com/podkletnov.html ? Well, NASA failed to reproduce the described effects. This does not mean it's bogus, but it's just not clear if this works at all. I don't think that the said scientists just throw away all their career just for a joke or out of laziness to check the results, but they still could err. (And of course, this all could be just a hoax.) Funny sidenote: The experiment described, which was first undertaken in 1996, describes a method that looks pretty related to the inner workings of the Star Trek artificial gravity generators, as described in the Enterprise Tech Manual - which was written in 1991. Quote Link to comment Share on other sites More sharing options...
Dr. Anomaly Posted January 29, 2004 Report Share Posted January 29, 2004 The photo of Ning Li & company is the photo I remember, which indicates it must have been the Popular Mechanics article I'm remembering. They're even in Alabama (which IIRC I said either Alabama or Georgia). Quote Link to comment Share on other sites More sharing options...
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