How fast can we go?

Shrykull · Post by **Shrykull** » 2007-09-29 05:53pm

How long do you think it will be before we can start launching Von-Neumann probes that fly at near, say 99% lightspeed?

According to this, it would take vast amounts of fuel, even antimatter to make something as big as bus (though probes would be smaller) to make a 900 year trip.

Also, I have this from Cern http://public.web.cern.ch/public/Conten ... dD-en.html

I was hoping antimatter would be the future answer to our energy needs. It seems more research is needed for this to happen.

No, the true answer is that it will never happen simply because of the entropy problem. Creating antimatter out of energy via E=mc2 unfortunately always produces equal amounts of normal matter and antimatter. This is fundamentally built into the universe. For any given amount E of energy you will get m/2 grams of antimatter and m/2 grams of matter. Putting these two amounts back together and annihilating them gives back E. But the process is not without loss: today the loss is enormous, but even if we could make the process very efficient, we would still not have any net gain!

So, we can't ever use it as an energy source, and it would take a lot more energy to produce to make it then what we'd get back, wouldn't it be more feasible to propel a ship some other way?

Shrykull · Post by **Shrykull** » 2007-09-29 05:54pm

here's the other thing I forgot to put the link to, the propulsion needs.

http://www.nasa.gov/centers/glenn/research/warp/scales.

Zablorg · Post by **Zablorg** » 2007-09-29 06:30pm

The NASA link is dead, I'm afraid.

How big a probe are we talking about here? Like that SW probe on hoth?

Lisa · Post by **Lisa** » 2007-09-29 07:57pm

http://www.grc.nasa.gov/WWW/bpp/ there is an interesting article on high speed space travel.

Lisa · Post by **Lisa** » 2007-09-29 07:58pm

oh and i think http://www.nasa.gov/centers/glenn/resea ... cales.html is what shrykull meant to post

Shrykull · Post by **Shrykull** » 2007-10-01 06:34pm

yes, it is, thanks Lisa

Grog · Post by **Grog** » 2007-10-02 05:06pm

Well this will be quite simplicial but the relativistic kinetic energy for something travelling at 0.99c is:
E_k=(1/(1-(v/c)^2)^(1/2)-1)mc^2
v=0.99c
Gives approximately:
E_k=6mc^2
So you will need more than 3 times the mass of the bus, probe or whatever in antimatter and as much matter.
If you store the fuel onboard you will need even more etc.

I think it will be a long time, hundreds of years if we will ever be capable of doing something like this.