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07-30-2015, 06:14 AM   #31
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QuoteOriginally posted by WPRESTO Quote
And when those people arrive and find nothing habitable, they'll have to make a U-turn and head home, if anyone remembers where that is.
Kinda takes all the fun out of it :-(

07-30-2015, 08:18 AM   #32
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QuoteOriginally posted by Not a Number Quote
If they turned around immediately and returned to Earth the travelers would have aged about 26 years while about 1003.8 years would have passed on Earth.
Maybe there will be a Pentax Full-Frame when the travelers return!

That is quite an interesting fact though.

---------- Post added 30-07-15 at 09:26 ----------

QuoteOriginally posted by WPRESTO Quote
[snip] The nearest star is roughly 4 light years away. [snip]
Technically the nearest star (to us) is just over 8 light minutes (0.0000158553... light years) away.
07-30-2015, 08:29 AM   #33
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Always fun to talk about, but so many others have written about over the decades, it seems like a topic where I would just reference links and books... There have been stories about 'generation ships' for decades now. Some of them were more about the ships, some more about the societies within them. Some spanned a few centuries, one that I just finished reading is 7900 years into a 10,000 year voyage (part 2 of 3...).

Then there are the Bussard ramjet stories, or going back before that, the 'torch ship' that carried its onboard fuel. Or solar sails powered by launch lasers in the Solar system. Or 'seedships' that carry genetic material and robots to raise the humans after building a starter colony. Or drives powered by Casimir(?) "vacuum energy". Or the stories where someone finds a way to cheat the Universe and go FTL, of course. Or...

Jim
07-30-2015, 09:05 AM   #34
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QuoteOriginally posted by bertwert Quote
Maybe there will be a Pentax Full-Frame when the travelers return!

That is quite an interesting fact though.

---------- Post added 30-07-15 at 09:26 ----------


Technically the nearest star (to us) is just over 8 light minutes (0.0000158553... light years) away.
Sure, technically correct. So we can get to that one much quicker. Let's load up all the politicians.

BTW: Thinking about a ship that can be accelerated to near the speed of light, let's say 75% the SOL. When the ship arrives it must be decelerated from that velocity which will require approximately the same amount of energy as it took to accelerate it. That's quite a bit of extra fuel or energy of some kind that must not only be carried along, but must be accelerated to that velocity to get going. Problems, problems, actually reality, reality that gets in the way of "dreamers" who like to dismiss such things along the lines of "technology will solve that." Might as well say "technology will beam us there instantaneously."

07-30-2015, 09:12 AM   #35
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It is tough to imagine traveling outside of our solar system with current methods of propulsion. I can't really even imagine starting a colony on Mars or some other planet inside our solar system. Feels like there are more details that would have to be taken care before you could even contemplate such a mission. I can't imagine (barring some miraculous scientific breakthrough -- "hyperspace or whatever") being able to do such a mission in the next one hundred years.
07-30-2015, 09:36 AM   #36
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QuoteOriginally posted by Rondec Quote
I can't really even imagine starting a colony on Mars or some other planet inside our solar system.
Mars One
07-30-2015, 09:48 AM   #37
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QuoteOriginally posted by WPRESTO Quote
BTW: Thinking about a ship that can be accelerated to near the speed of light, let's say 75% the SOL. When the ship arrives it must be decelerated from that velocity which will require approximately the same amount of energy as it took to accelerate it. That's quite a bit of extra fuel or energy of some kind that must not only be carried along, but must be accelerated to that velocity to get going.
A constant 1 g ship would run it's main propulsion constantly to accelerate/decelerate at one gravity. Half of the trip is spent accelerating. The other half is spent decelerating. So maximum velocity would occur at the turn around point. The advantage of such a ship is that the passengers would have earth-like gravity for almost the entire trip out (or back).
07-30-2015, 10:21 AM   #38
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Here's another bit of reality check on traveling to the stars (other than the Sun).
1) let's try to get our spaceship up to 10% the speed of light. A one-way trip to the Alpha-Proxima Centauri system would take about 40 years.
2) light speed is about 300,000,000 meters/sec, so we want to get our ship up to 30,000,000 m/sec*
3) let's assume the human body can withstand about 10g acceleration for a prolonged time**
4) 10g translates to an acceleration of about 100 m/sec/sec (it's actually 98 m/sec/sec but let's give bit more than 10g)
5) At that acceleration it would take 300,000 seconds to get to 10% the speed of light, or about 5,000 minutes, or about 83 hours, or about 3.5 days of continuously experiencing an acceleration about twice as great as the fastest roller coasters
6) problem is, it isn't clear whether any human body can withstand 10g for more than a few minutes much less a full hour, and the only people who can must be in the prime of life & health, preferable male (stronger neck muscles required) and wearing a g-suit; and during during the 3.5 days of acceleration you cannot do anything, such as eat or drink.
7) If we come down to a leisurely one-g acceleration, it would of course take 10 times as long, or accelerating for 35 days.

*The highest velocity attainable by a rocket's own engine is currently about 2,000 m/sec. The New Horizons spacecraft, with a gravity boost from Jupiter, raced by Pluto at about 14,000 m/sec, but to reach 10% the speed of light it would have to go more than 200 times faster than that.
**Maximum g-force for a trained fighter pilot in a "g-suit" to maintain consciousness is given as 9g but only for a very brief time, perhaps a few minutes, not for an hour much less several days.


Last edited by WPRESTO; 07-30-2015 at 10:40 AM.
07-30-2015, 11:05 AM - 2 Likes   #39
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We ain't goin' anyplace, folks.
Sorry about that.
07-30-2015, 11:14 AM   #40
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QuoteOriginally posted by Auzzie-Phoenix Quote
what would be needed for interstellar travel.
Another 10000 years of technological development.
07-30-2015, 11:48 AM   #41
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Maybe we could build spaceships like Xenu had? They look like some type of Boeing airliner...

Last edited by SpecialK; 07-30-2015 at 08:34 PM.
07-30-2015, 06:14 PM   #42
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If some massive solar event was to render all of the inner solar system uninhabitable (just about nothing else at this point would justify such a project) then there are 3 different probable ways of making such a trip. A multigenerational ship, a sleeper ship and a genomic ship. All 3 would need to use a nuclear pulse engine like the proposed Orion spacecraft.

All of the ships would be slow boats and as such would not only be extremely expensive but could quite possibly be overtaken by advances in science and technology. It would then be equallypossible that the people getting off of the ships at the end of their trip would find out that their world is already populated by people who left after them.

The multigenerational ship would have to be much bigger than most people would envision. Think of something like the O’Neil L5 colonies. You would basically take everything you need and remanufacture items when these items wear out using the raw materials they bring with them. This could possibly get you out to some star system 20 to 40 ly away. But even then you would be talking between 10 and 30 generations. That is approaching the length of all of written history.

The sleeper ship would have everything and everyone in suspended animation frozen solid. This is not that far of a leap of the current technology. We are getting to the point of being able to freeze and transplant human organs it would just be a matter of time before we could freeze and revive an entire person. You would still need to take your basic tools/materials with you and manufacture all the items that you would need at your destination. With such a ship it might be possible to stretch out the distance to maybe 100 to 200 ly.

With the genomic ship you would not take any people or animals. You would essentially just take the genetic material frozen (sperm and eggs) and grow babies when you reached the destination. Computers and robots would need to raise the 1st generation. A ship like this might conceivably get you out to 1000 light years.


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07-30-2015, 07:03 PM   #43
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QuoteOriginally posted by DAZ Quote
If some massive solar event was to render all of the inner solar system uninhabitable (just about nothing else at this point would justify such a project) then there are 3 different probable ways of making such a trip. A multigenerational ship, a sleeper ship and a genomic ship. All 3 would need to use a nuclear pulse engine like the proposed Orion spacecraft.

All of the ships would be slow boats and as such would not only be extremely expensive but could quite possibly be overtaken by advances in science and technology. It would then be equallypossible that the people getting off of the ships at the end of their trip would find out that their world is already populated by people who left after them.

The multigenerational ship would have to be much bigger than most people would envision. Think of something like the O’Neil L5 colonies. You would basically take everything you need and remanufacture items when these items wear out using the raw materials they bring with them. This could possibly get you out to some star system 20 to 40 ly away. But even then you would be talking between 10 and 30 generations. That is approaching the length of all of written history.

The sleeper ship would have everything and everyone in suspended animation frozen solid. This is not that far of a leap of the current technology. We are getting to the point of being able to freeze and transplant human organs it would just be a matter of time before we could freeze and revive an entire person. You would still need to take your basic tools/materials with you and manufacture all the items that you would need at your destination. With such a ship it might be possible to stretch out the distance to maybe 100 to 200 ly.

With the genomic ship you would not take any people or animals. You would essentially just take the genetic material frozen (sperm and eggs) and grow babies when you reached the destination. Computers and robots would need to raise the 1st generation. A ship like this might conceivably get you out to 1000 light years.


DAZ
30 generations @ 25yr/generation = 750 years in transit. To get to a star 30ly away in 750 years would require a velocity of 4% the speed of light which is 12,000,000 meter/sec. The New Horizons with a boost from Jupiter attained about 14,000 m/sec at Pluto. So we need to increase speed 850 times. Nothing to it.

---------- Post added 07-30-15 at 10:20 PM ----------

Did a little quick research on cryogenics. A dog has been successfully revived after freezing to "clinical death" for about 3 hours, but it was necessary to drain much/most of its blood and replace it with a hypersaline solution. Somewhat similar experiments on pigs. A major unsolved problem with very deep freezing (in, for example, liquid nitrogen), is that water within cells freezes, crystallizes, and ruptures the cell membranes. Before humans are deep frozen for a 750 year trip to a star system 30 ly away, we better demonstrate that it's possible to freeze a few hamburgers for 20 years and thaw them with no sign of "freezer burn."
07-30-2015, 07:55 PM   #44
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I was assuming with the increases in longevity something more akin to 75 to 100 year generations. Although I can see how you might have chosen the more traditional 25 year generation. So the trip times I would be talking about would be in the 2500 to 3000 year time frame. Although it might be technically possible for more than 3000 years it would be extremely difficult to conceive of a civilization that is must last essentially unchanged for 3000 years.

Using a nuclear pulse engine you might, admittedly with a lot of effort, be able to get up to between 1 and 2% of the speed of light and slow back down again. It could quite possibly take 20 to 30 years to mine and produce the required amount of nuclear material. All the material that was produced during the Cold War would only be a fraction of what was needed. Again this would be a massive undertaking on almost all conceivable scales.

The 1st part of the process would be very similar to what they did with the dog. They have been doing some experiments with essentially entirely different chemicals that have been used before. The process would start by draining all the blood than using another chemical to draw as much of the water as possible out from all the cells. They would then remove these chemicals and replace what is essentially a prune with another chemical that doesn’t really freeze until you get down to almost liquid nitrogen temperatures. At room temperature it looks like water but it extremely low temperatures it looks like Jell-O. At this point with some of the advances in technology it might actually be possible to suspend people in liquid nitrogen. They have conducted some experiments that they have taken some biological materials down to liquid nitrogen temperatures and done this. So yes this would have to be much better than freezing some hamburgers and would definitely require no signs of freezer burn. All of this is probably 20 to 30 years away but it quite possibly could be within the realm of the sciences. It would probably take you at least that long to build the ship.

DAZ.
07-30-2015, 09:07 PM   #45
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Technology cannot bypass the laws of nature. Nature, to be commanded, must be obeyed. Humans evolved for a certain environment that exists on earth. We would be like a fish out of water in interstellar space. There is only so much one can do to replicate earth-like conditions, and those shortfalls would add up over time. We would not be healthy reproducers for long. The sun has about 4 billion years left before engulfing the earth in it's death throes; then one would truly speak of global warming. I doubt humanity will escape that end as beings, although other non living methods of emigration may be discovered.
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