Is it possible to build a vehicle that can accelerate to .99 C?How would we go about doing something like this?If at all possible, how many centuries or millennia is it before this can be accomplished? Could a Bussard scramjet do it?How large would a laser/maser/gaser have to be to get the craft up to such speed?How long would it take from the crew's perspective to cross the galaxy?How big would the craft be? I imagine a lot of fuel would be required even if you could gather propellant along the way - Bussard scramjet. What kind of fuel would be needed?Would such a vessel help establish a galactic civilization? Or would time dilation make implausible?What would it look like?Are any sort of warp drives completely impossible? If so, which of the following would best for interstellar travel: beamed propulsion, matter/antimatter reaction, Bussard scramjet, or something else?This very fascinating for me.
...teleporting consciousness should be easy by that time.
At 0.99c, gamma = 1/sqrt(1-(v/c)^2) ~=~ 7, so 100k light years for the galactic diameter would take about 100k years and would be perceived as 14k years passage of time for those onboard.
That's right, its the accelration not the velocity that does it. And remember, you don't need to accelerate in a straight line, you can go in a circle.Unstable particles moving at relativistic speeds in particle accelerators increase their lab-frame half life and so they don't decay as quickly as you might expect.
I reckon we've got a good chance in 2173-74 season
We are about theoretically .05c, so we would be lucky to get 1 percent speed of light. Without some quantum leap in physics (no pun intenteded).RegardsRobert
Can someone remind me again. To date, what is the largest thing that has been accelerated to that speed? Heavy Atomic Nuclei?Just to put this in perspective...
That's right, its the accelration not the velocity that does it. And remember, you don't need to accelerate in a straight line, you can go in a circle.
This refers to the "twins paradox".AIUI, in special relativity (ie if not accelerating), then a crew member looking back at Earth would see it receding at high speed, and therefore it's clocks running slowly. (It's all "relative", you see.) Thus the paradox - each sees the other's clocks as running slow.It is the acceleration undertaken by the ship which means duration is shorter for the twin in the ship's crew than the one left behind on Earth. Apparently. (I never did quite grasp the reason myself.)cheers, Martin
I don't see how interstellar micro space probes could work, every atom they collided with would be a cosmic ray.
This refers to the "twins paradox".AIUI, in special relativity (ie if not accelerating), then a crew member looking back at Earth would see it receding at high speed, and therefore it's clocks running slowly. (It's all "relative", you see.) Thus the paradox - each sees the other's clocks as running slow. It is the acceleration undertaken by the ship which means duration is shorter for the twin in the ship's crew than the one left behind on Earth. Apparently. (I never did quite grasp the reason myself.)cheers, Martin
Quote from: alexw on 08/03/2011 04:51 am At 0.99c, gamma = 1/sqrt(1-(v/c)^2) ~=~ 7, so 100k light years for the galactic diameter would take about 100k years and would be perceived as 14k years passage of time for those onboard. This always messes with my head So would they only age 14 years, over those 100 years? And if - dismissing the slowing down time etc - they carried out the return trip, they'd arrive back on Earth 28 years older than when they set out, but 200 years would have passed on Earth?
but if we are to colonize the galactic it will be one planet at a time. If we can find a planet with in 15 LY then we could get there in 26 years ship time at 0.5c.
Magsail deceleration has disadvantages. It doesn't take long to go from, say, 0.5c to 0.1c, but the deceleration from 0.1 to 0.001c or so takes ages.
Quote from: DLR on 08/30/2011 07:20 amMagsail deceleration has disadvantages. It doesn't take long to go from, say, 0.5c to 0.1c, but the deceleration from 0.1 to 0.001c or so takes ages. I wonder if you could use the magsail to collect propellant during deceleration so that once the speed was too slow for the magsail to be effective you would have full tanks to complete the deceleration by more conventional electric propulsion.
That's a Bussard ramjet, but with the drag as a desireable characteristic rather than something to work around.It could work, perhaps, if you could burn protium in a fusion reactor (Bussard et al. claimed they had found a way to catalyze p-p fusion, but the description was ambiguous and no one is quite sure what it was...).
Quote from: 93143 on 08/30/2011 07:26 pmThat's a Bussard ramjet, but with the drag as a desireable characteristic rather than something to work around.It could work, perhaps, if you could burn protium in a fusion reactor (Bussard et al. claimed they had found a way to catalyze p-p fusion, but the description was ambiguous and no one is quite sure what it was...).It's not ambiguous at all. Bussard meant CNO Cycle catalyzed fusion, as described in Daniel Whitmire's paper back in 1975..."Relativistic Spaceflight and the Catalytic Nuclear Ramjet", Acta Astronautica, 2, 497 (1975). Available from Askmar.com... Catalytic Nuclear RamjetWe discussed this a few years ago and Askmar.com put it up in the mean time, with updated formatting.
I once read that compressing the entire column of interstellar medium between the Sun and Alpha Centauri to a normal density (air I presume), you would get a layer only a micrometer or so thick ...
All you guys do realize that any solid object travelling at that speed is also the most deadly weapon of mass destruction in the known universe, right?The R-bomb. More effective than antimatter. And by the time you see it coming, it's almost on top of you. Impossible to intercept (due to light lag you never see it where it really is), and even if you do blow it up, the particle/vapor cloud is still there travelling at nearly the same velocity and with nearly the same kinetic energy.Charles Pellegrino (I think it was) wrote a novel some years back called "Killing Star" where Earth's population is wiped out through relativistic bombardment by a hostile alien species. One of the few survivors is later captured by the invaders who tell him the reason for the attack: Once humans had developped relativistic travel they became too dangerous to have as neighbours because every relativistic starship is simultaneously an undetectable and unstoppable WMD. So they struck first in the ultimate preemtive attack...Something to think about.Unfortunately, the book is almost impossible to find nowadays. Too bad, because Pellegrino actually had an excellent concept study of what such a vessel might look like ("Valkyrie", google it up. It was also used in the Avatar movie. Tho I think Valkyrie was limited to .92c).
Magsails should have a magnetic field the size of the moon, tho this will vary depending on velocity and local interstellar magnetic flux density.So using the 21cm radio line suggest seven times higher density than the Lyman alpha measurement that qraal bases his calcs on.
Unfortunately, the book is almost impossible to find nowadays.
Looking at the prices, a bit of a collectors item though.
The R-bomb. More effective than antimatter. And by the time you see it coming, it's almost on top of you. Impossible to intercept (due to light lag you never see it where it really is)
and even if you do blow it up, the particle/vapor cloud is still there travelling at nearly the same velocity and with nearly the same kinetic energy.
Just to illustrate the point that any relativistic vehicle is also an RKV (relativistic kill vehicle or R-bomb) and simultaneously the most destructive WMD known:1 kg of matter accelerated to .99c impacting Earth has a TNT equivalent of 132 Megatons (almost 2.5 times the Tsar Bomba, the largest nuke ever detonated).Compare this to 1 kg of matter-antimatter annihilation, which has a TNT equivalent of "only" 21.5 Megatons...And yes, any relativistic Starship is also an RKV. Infact, an RKV is much easier to build, since it doesn't have to carry fuel to slow down at the end of the voyage...
An interesting addition to the discussion could be this article in the New York Times:http://www.nytimes.com/aponline/2011/09/22/world/europe/AP-EU-Breaking-Light-Speed.html?hpThey are reporting from CERN that they have recorded nuetrinos going faster than the speed of light. Maybe c is not the speed limit everyone thought it was.