[Ludi]

$this->bbcode_second_pass_quote('Sixstrings', ' ')But oh well, I guess our Republican president is right in his view that everything's best left to the private sector.

[hillsidedigger]

At 25,000 miles per hour, the fastest people have ever flown, it would take 550,000 years to get there and consume more energy even for a small spacecraft carrying a couple of breeding pairs (inbreeding?) than mankind has yet consumed on Earth.

[Sixstrings]

$this->bbcode_second_pass_quote('hillsidedigger', 'A')t 25,000 miles per hour, the fastest people have ever flown, it would take 550,000 years to get there and consume more energy even for a small spacecraft carrying a couple of breeding pairs (inbreeding?) than mankind has yet consumed on Earth.

[dissident]

As noted above even at half the speed of light the amount energy required is immense.

E=gamma*m*c^2, gamma=1/(sqrt(1-(v/c)^2))

dE=E(v)-E(0) so for v=c/2 and a 100,000 ton space ship (a colony ship may have to be much heavier) we have

(1.155-1)*m*c^2=0.155*1e8*(299,792,458)^2=1.39e24 J

The 2008 world energy consumption was 4.74e20 J. Dividing this into dE we get 2939 years.
But, of course, the world was not consuming at 2008 levels throughout its history.

Instead of dreaming about moving our locust culture to destroy another world we are going to have to adapt or die out.

[EnergyUnlimited]

$this->bbcode_second_pass_quote('dissident', 'A')s noted above even at half the speed of light the amount energy required is immense.

E=gamma*m*c^2, gamma=1/(sqrt(1-(v/c)^2))

dE=E(v)-E(0) so for v=c/2 and a 100,000 ton space ship (a colony ship may have to be much heavier) we have

(1.155-1)*m*c^2=0.155*1e8*(299,792,458)^2=1.39e24 J

The 2008 world energy consumption was 4.74e20 J. Dividing this into dE we get 2939 years.
But, of course, the world was not consuming at 2008 levels throughout its history.

Instead of dreaming about moving our locust culture to destroy another world we are going to have to adapt or die out.

[Sixstrings]

$this->bbcode_second_pass_quote('EnergyUnlimited', 'I')nstead of dreaming about moving our locust culture to destroy another world we are going to have to adapt or die out.

If you also take into account that the craft would have to carry its fuel used for acceleration and deceleration, and also consider specific impulse in your calculations, then you may rest reassured that we are not traveling anywhere.

Scotty must stay at home... Sorry...

[Ludi]

"Voyager 1 is currently more than 17 billion kilometers from the Sun."

http://voyager.jpl.nasa.gov/

[EnergyUnlimited]

$this->bbcode_second_pass_quote('Sixstrings', '')$this->bbcode_second_pass_quote('EnergyUnlimited', 'I')nstead of dreaming about moving our locust culture to destroy another world we are going to have to adapt or die out.

If you also take into account that the craft would have to carry its fuel used for acceleration and deceleration, and also consider specific impulse in your calculations, then you may rest reassured that we are not traveling anywhere.

Scotty must stay at home... Sorry...

[Sixstrings]

$this->bbcode_second_pass_quote('EnergyUnlimited', 'L')aws of physics are the same at least across visible Universe.
Nothing unexpected would happen to laws of physics once we have left Solar System or even Galaxy.
We have impeccable record based on astronomical observations to prove that.

[EnergyUnlimited]

$this->bbcode_second_pass_quote('Sixstrings', '')$this->bbcode_second_pass_quote('EnergyUnlimited', 'L')aws of physics are the same at least across visible Universe.
Nothing unexpected would happen to laws of physics once we have left Solar System or even Galaxy.
We have impeccable record based on astronomical observations to prove that.

[Tanada]

Odds are by the time we are ready to try such a journey we will have developed Bussard Ramjets to power our flights, which over such a range would allow us to reach a respectable percentage of light speed before turnover and deceleration back down to average interstellar speed of the target star on the end of the journey.

http://www.google.com/search?q=bussard+ ... =firefox-a

[Golgo13]

Then you hit a nickel-sized piece of space debris at ludicrous speeds and your entire ship and crew are gone.

[Ludi]

Why not just develop the Universal Will To Become drive ships?

[Sixstrings]

$this->bbcode_second_pass_quote('Ludi', '')$this->bbcode_second_pass_quote('Golgo13', 'T')hen you hit a nickel-sized piece of space debris at ludicrous speeds and your entire ship and crew are gone.

[EnergyUnlimited]

$this->bbcode_second_pass_quote('Tanada', 'O')dds are by the time we are ready to try such a journey we will have developed Bussard Ramjets to power our flights, which over such a range would allow us to reach a respectable percentage of light speed before turnover and deceleration back down to average interstellar speed of the target star on the end of the journey.

http://www.google.com/search?q=bussard+ ... =firefox-a

[Sixstrings]

$this->bbcode_second_pass_quote('EnergyUnlimited', 'T')here are some calculations done by dr Robert Zubrin showing that these ramjets would generate more drag than thrust.

[Tanada]

Interstellar dust and gas, on the order of one molecule per cubic meter, adds up too lots and lots of teeny tiny impact events that slow your craft down as you collide with them and ricochet off of them. The faster you go the more of them you run into during a set period of time and as you approach half light speed it becomes more like flying a plane than coasting through empty vacuum. The purpose of a Bussard ramjet is to use this interstellar gas as fuel and burn it to maintain your velocity.

[EnergyUnlimited]

$this->bbcode_second_pass_quote('Sixstrings', '')$this->bbcode_second_pass_quote('EnergyUnlimited', 'T')here are some calculations done by dr Robert Zubrin showing that these ramjets would generate more drag than thrust.

[Tyler_JC]

My physics is a little rusty but I found a simple calculator online for the kinetic energy formula.

To move a one kilogram object at 10% the speed of light would require the energy equivalent of ~98,000 barrels of diesel. But, of course, you have to account for the weight of the fuel. Obviously we wouldn't use diesel fuel in space but it gives you a sense of how much energy we're talking about here.

The space shuttle, a craft FAR too small for anything even approaching interstellar travel, weighs more than 100,000kg.

A more realistic interstellar space craft might be 50 times heavier (after all, we have to take care of a crew of people for decades). That means we're talking about a five thousand metric ton craft that has a magic fuel source which weighs nothing.

Amount of energy required to move a 5,000,000kg object at 10% the speed of light?

2.25E+25 Joule

Amount of energy that hits the Earth every year from the sun?

5.5E+24 Joule

So our space ship would need to use 4 times more energy than hits the earth every year just to accelerate to 10% the speed of light. If we also wanted to slow our ship down to zero again (you know, rather than just collide with the planet and create a massive freaking crater), we would actually need 8 times as much energy as hits the Earth every year.

That is several orders of magnitude more energy than humanity has used during its entire existence.

We cannot and will not devote that much energy to interstellar space travel.

[Sixstrings]

I've been watching Star Trek: Enterprise on DVD lately. In one of the early episodes, they mention Earth finding a planet just 20 lightyears away and it being "too close not to colonize." So they sent a colony ship which took years to get there and then the colony was lost and the story went on from there.

Anyway, was just ironic about the perfect planet 20 lightyears away part, this show was produced before Gliese 581g was discovered.