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Futuristic space travel between star systems 
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#1
Feb2012, 07:37 PM

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I am a writer of science fiction and I need to know some basics about space travel. I've read that it would take a ship 40 years to travel 1 parsec (3.26 light years) if the ship moved at 10% the speed of light. Does that sound right? Given that a futuristic ship could travel at this speed, how many kilometers would the ship travel in one hour? Should a ship slow down when cruising through a solar system or approaching an asteroid where, in this case, it needs to land at a port. This said asteroid is traveling in an orbit about 3.26 light years out of the Centuari system.



#2
Feb2012, 08:17 PM

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The speed of light is 299,792,458 m/s. I'm going to round that to 300,000,000 m/s for simplicity. 10% of that is 30,000,000 m/s. There are 60 seconds in a minute so at that speed you would go (60)(30,000,000)= 1,800,000,000 m/min. There are then 60 minutes in an hour so that would be (60)(1,800,000,000)= 108,000,000,000= 1.08 x 10^{11} m/h or 108 x 10^{8} km per hour.
A parsec is 3.1 x 10^{16} m. At 108,000,000,000 m/h, it would take 3.1 x 10^{16}/1.08 x 10^{11}= (3.1/1.08) x10^{1611}= 2.87x 10^{5}= 287,000 which is approximately 287,000/24= 11958 days or 11958/365.25= 39.75 years (39 years 9 months). Yes, that's pretty close to 40 years. If the ship wants to land, yes, I would recommend it slow down! Otherwise, there is going to be a really big kaboom! 


#3
Feb2012, 09:00 PM

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yeah, which is why, if you want the ship to accelerate and decelerate so that it actually starts and stops at your two places, then it's going to take a bit more than 40 years.
If you want the ship to accelerate at a comfortable rate like 1.0g, which is to say 9.8 m/s^{2}, then we'd do this: 10% of c is 30,000,000 m/s, v = at, so (30,000,000 m/s) = (9.8 m/s^{2})t so t = (30,000,000 m/s)/(9.8 m/s^{2}) = 3061224.5 seconds, or about 35 and a half days. Deceleration would take the same amount of time. 


#4
Feb2112, 11:00 AM

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Futuristic space travel between star systems
Okay, thanks for the reply. Now, let me ask this. Say my space ship left the Centauri system, needs to land on an asteroid that is in the ships direct path. After 40 years of traveling at the said speed (10% light year), HOW would the ship slow down in space in order to achieve the decelerated velocity it needs to land? How do objects slow down in a vacuum? And how long would it take, in other words, from that 40 year period of traveling that fast from the point where it could dock. Looking for ideas, since I am a molecular biologist and the theories of this for my story should be based on fact.



#5
Feb2112, 11:02 AM

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Thanks!



#6
Feb2112, 11:18 AM

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To decelerate, it turns around, pointing its propulsion straight forward, and turns its propulsion on until its velocity is zero again. 


#7
Feb2112, 11:54 AM

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#8
Feb2212, 07:03 AM

P: 118

http://www.physicsforums.com/showthread.php?t=575567
If you want to write SF, maybe you would find this one interesting also. Well I would add gravity assist to the list, to use the gravity and orbit of planets and stars to your advantage, to reduce fuel costs. I also read a solution, where magnetic sails were driven by giant particle beams, although it is doubtful, that you dont need independant engines for interstellar travel. But again, reducing fuel costs is good. To build a realistic interstellar ship... that would a bit like to a tiny artifical planet. 


#9
Feb2212, 08:06 AM

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Stellar gravity assist won't work because the gravitational body needs to be in motion relative to you to give you an assist. We start off stationary wrt the solar system, so no boost. 


#10
Feb2212, 08:32 AM

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#11
Feb2212, 09:33 AM

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With regards to long space voyages, propulsion may be one of the easier hurdles to overcome! 


#12
Feb2212, 01:42 PM

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You may want to check out this website http://www.projectrho.com/rocket/ It's designed to help people write realistic science fiction. Check out the index for all the articles covered. 


#13
Feb2212, 04:52 PM

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#14
Feb2312, 04:09 AM

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I correct myself.
So after you decelerated to a lower speed, than you can use gravity assist for further deceleration, to reach low orbit of an alien planet. I guess such a giant ship wont be able to land, they will have to use many shuttles, maybe space elevators, skyhooks. Otherwise it would be interesting to read about the artifical biosphere of an interstellar ship. :) 


#15
Feb2312, 08:10 AM

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2] If you have technology advanced enough for interstellar travel, why try to save gas on maneuvering in the driveway? 


#16
Feb2812, 02:18 AM

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I see.
Well it can be a dramatic plot, that you (almost) run out of fuel, and you have to return to such outdated concept. Otherwise, i wondered on the following since Middle School : a ship reaches relativistic speeds. It's mass is growing. The fuel's mass also growing. In case of antimatter, full mass is turned into energy. How can it affect the ship's acceleration? Or just maybe mass growing is because electromagnetic interactions become weaker and weaker, that is why acceleration becomes harder? That idea was given to me by this article : http://en.wikipedia.org/wiki/Time_dilation Bookmark : Simple inference of time dilation due to relative velocity I dont know if it is right, but sure made me understand, how to derive Lorentz factor. 


#17
Feb2812, 05:10 AM

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#18
Feb2812, 06:39 AM

P: 118

I also wondered on the following thing : a hungarian scientist had the idea, that IF we could somehow control gravity, we could build galaxy railways that accelerate with gravity, we could reach big acceleration as we would freefall.
Can we reach ANY speed we want in this way? I mean, in case of black holes acceleration of gravity even stronger than light, am I wrong? 


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