Author Topic: Interstellar Spaceflight: Is It Possible?  (Read 22662 times)

Offline Martin FL

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Offline Justin Space

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #1 on: 12/07/2005 02:43 pm »
What a great read. There must be a way around Einstein's boundaries of travelling faster than the speed of light?

Offline Rocket Ronnie

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #2 on: 12/07/2005 02:58 pm »
Looks like the speed is not going to be impossible, but don't you simply lose acceleration, regardless how much power you throw at it, as you get closer to light speed, before never actually breaching it?

Offline To The Stars

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #3 on: 12/07/2005 06:41 pm »
Quote
Rocket Ronnie - 7/12/2005  9:58 AM

Looks like the speed is not going to be impossible, but don't you simply lose acceleration, regardless how much power you throw at it, as you get closer to light speed, before never actually breaching it?

Well yes, but I've never believed anything is impossible.

Offline publiusr

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #4 on: 12/07/2005 07:39 pm »

We could have a  starship soon. A launch vehicle like Sea Dragon that can loft 550 tons to LEO would be fueled by water broken down at sea by the reactor of an ARKTIKA type icebreaker. The payload would be a nuclear salt water rocket which would also require water. Such a craft would give steady 1g thrust and be more smooth than an Orion type starship.

So a super-HLLV/NSWR combination is what we should strive for after standard HLLV/NERVA type interplanetary ships.

Offline braddock

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #5 on: 12/07/2005 08:25 pm »
It's interesting reading up on some of this.

The isp of NERVA was apparently only around 1000 isp, while the calculated isp of Orion was 10,000 to 1 MILLION isp.  Apparently a controlled nuclear reactor like NERVA has to be throttled back to keep it from melting, so it's only about twice the isp of a chemical.
Here is an interesting site with these figures: http://www.astronautix.com/articles/probirth.htm

Does anyone know where to find worked Tsiolkovsky equations for an interstellar flight?  Like an Isp/Mass ratio/travel time graph for Alpha Centauri?  It would be interesting to see.

Offline Avron

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #6 on: 12/08/2005 03:56 am »
Quote
Justin Space - 7/12/2005  10:43 AM

What a great read. There must be a way around Einstein's boundaries of travelling faster than the speed of light?

Yes .. have no mass to start with.. as you go faster mass increases F=ma good luck with the 'F' as the mass approaches infinity..

Offline CuddlyRocket

Re: Interstellar Spaceflight: Is It Possible?
« Reply #7 on: 12/08/2005 11:35 am »
Quote
Justin Space - 7/12/2005  3:43 PM

There must be a way around Einstein's boundaries of travelling faster than the speed of light?
Do you want to travel faster than light? Or do you want to get somewhere faster than light can? These are not the same.

One way to achieve the latter is to simultaneously travel back in time (or travel forward in time less than you would otherwise). Providing you limit the time travel so that you can't arrive at your starting point before you left, there's no problems with causality.

Time travel is not against the laws of physics as currently understood. (Neither is FTL, although Einstein's special theory of relativity implies that doing so involves Imaginary quantities.) The details I'll leave as an engineering exercise for the interested student. :)

Offline darkenfast

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #8 on: 12/08/2005 04:51 pm »
It would only provide that thrust for a very short time.  While it would be an improvement over chemical propellants, it wouldn't be even a thousandth of what is required for a reasonable travel time to another star.
I believe that if nuclear-thermal rockets are ever used, it will be to lift a deep-space craft from Low Earth Orbit to either a high orbit or escape velocity to avoid the Van Allen belts.  Then, far more efficient (but lower acceleration) nuclear-electric propulsion will take over.  The same would probably be required on return as well.
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Offline nacnud

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #9 on: 12/08/2005 05:21 pm »
Quote
Looks like the speed is not going to be impossible, but don't yousimply lose acceleration, regardless how much power you throw at it, asyou get closer to light speed, before never actually breaching it?

No accelleration stays the same, its time that gets all weird. (as well as mass and lenght)


Offline Avron

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #11 on: 12/09/2005 04:45 am »
Quote
nacnud - 8/12/2005  1:21 PM

Quote
Looks like the speed is not going to be impossible, but don't yousimply lose acceleration, regardless how much power you throw at it, asyou get closer to light speed, before never actually breaching it?

No accelleration stays the same, its time that gets all weird. (as well as mass and lenght)

Wierd like the warping of space-time... small engineering challange...:) Humm from our view on earth, what would a spacecraft look like moving away from us at light speed?

Offline braddock

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #12 on: 12/09/2005 11:53 am »
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Avron - 9/12/2005  12:45 AM

Wierd like the warping of space-time... small engineering challange...:) Humm from our view on earth, what would a spacecraft look like moving away from us at light speed?

It couldn't move AT light speed, because that would require infinite energy.  But if it was moving away from you at a hair under light speed, I believe the light and other RF from the spacecraft would be red-shifted down to the extremely low frequency radio spectrum, so you wouldn't really be able to "see" it except with a radio telescope.

Perhaps it would be an interesting SETI test someday to look at extrasolar planet spectra and see if we see light/radio sources rapidly red and blue shifting in the spectrum, as high-speed spacecraft presumably buzz around.  :)


Offline CuddlyRocket

Re: Interstellar Spaceflight: Is It Possible?
« Reply #13 on: 12/10/2005 09:48 am »
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braddock - 9/12/2005  12:53 PM

It couldn't move AT light speed, because that would require infinite energy.
Not to be picky, but to be strictly accurate (OK, picky! :)), Einstein's equations don't apply at v=c and therefore say nothing at all about the energy of an object with non-zero rest mass travelling at c.

True, for all v less than c, as v approaches c, the energy becomes arbitrarily large, but is at all times finite and therefore never becomes anywhere near infinite.

Offline mikorangester

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #14 on: 03/25/2011 04:37 am »
No

Offline Downix

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #15 on: 03/25/2011 04:44 am »
No
Wrong.

Holy necro-thread batman!
« Last Edit: 03/25/2011 04:45 am by Downix »
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline Joris

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #16 on: 03/25/2011 06:06 am »
No

The whole point of project Deadalus was to show that interstellar spaceflight was possible. Even though it is unaffordable now, in one or two centuries the economy will have grown enough to afford a Deadalus.

But at that time there will probably have been a breakthrough. General relativity is really only an approximation of how gravity works. So there might be *glitches* that we will be able to use.

Lastly, as the biological singularity comes near, interstellar spaceflight becomes possible within a lifetime for a very simple reason.
JIMO would have been the first proper spaceship.

Offline Downix

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #17 on: 03/25/2011 06:13 am »
No

The whole point of project Deadalus was to show that interstellar spaceflight was possible. Even though it is unaffordable now, in one or two centuries the economy will have grown enough to afford a Deadalus.

But at that time there will probably have been a breakthrough. General relativity is really only an approximation of how gravity works. So there might be *glitches* that we will be able to use.

Lastly, as the biological singularity comes near, interstellar spaceflight becomes possible within a lifetime for a very simple reason.
You don't even need to be so advanced as Daedalus, a Project Orion would fill the job fine.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline RanulfC

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #18 on: 03/28/2011 07:44 pm »
You don't even need to be so advanced as Daedalus, a Project Orion would fill the job fine.
Oh heck we've already started on "Interstellar" space flight and without even using an "Orion-Boom-Boom" vehicle! We used a couple of Titan-III/Centaurs in fact!
http://en.wikipedia.org/wiki/Voyager_1

Now if you want to get anywhere in less than a geological time frame....

Randy
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Offline mlorrey

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Re: Interstellar Spaceflight: Is It Possible?
« Reply #19 on: 03/31/2011 05:23 am »
You don't even need to be so advanced as Daedalus, a Project Orion would fill the job fine.
Oh heck we've already started on "Interstellar" space flight and without even using an "Orion-Boom-Boom" vehicle! We used a couple of Titan-III/Centaurs in fact!
http://en.wikipedia.org/wiki/Voyager_1

Now if you want to get anywhere in less than a geological time frame....

Randy

Starwisp is the interstellar space flight on the cheap that is affordable now, falls within current known physics, though it depends on its ultimate utility on the idea that humans will eventually either learn to upload their minds onto computers (which obviously means we can then have our minds beamed on laser or radio beams to interstellar distances with no subjective travel time, since no time passes at light speed) or we are replaced by artificial intelligence.

Starwisp is a small interstellar ship, essentially a laser powered solar sail that carries as its cargo a communications system, lots of memory storage, and an ability to manufacture either robots, or artificial wombs and DNA sequencers, when it arrives at a habitable world. On arrival, it beams a message back to earth that its arrived, and people start beaming their minds and memories (if they were not preloaded on a starwisps memory at launch) to the destination for reception and installation in either a robot body, or a clone of their original body....

The propulsion concept is entirely doable at present. The cargo side of things, obviously is not, but given our current technological singularity, will likely be doable within the next few decades.
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