How do you FTL?

[TheBigDog]

Why not just use brute force? If we cannot go as fast as light, lets just go as fast as we can. How fast can current technologies accellerate something in space? Could we hit .5c or better?

 

Bill

[Pyrotex]

...How fast can current technologies accellerate something in space? Could we hit .5c or better?

There are two answers: (1) using internal reaction mass (2) using external propulsion technique.

 

(1) Back of the envelope calculations assuming a "rocket" that spits out "reaction mass". Max speed is determined by propellent fraction of total vehicle and "specific impulse" of engine, Isp. The latter is essentially the efficiency of the engine--think of how many pounds of thrust do you get by expending 1 pound per second of reaction mass. Chemicals give up to Isp=450. Atomic thermal engines up to Isp=2000. Ion engines up to Isp=10,000. A big ship with 70% reaction mass and Isp=10,000 could perhaps get 30%-50% C, but it would take many years. And then you would have no fuel to slow down!! But maybe you don't want to.

 

(2) Using terawatt infrared lasers, powered by solar radiation around, say, the planet Mercury--and LOTS of them!--you could accelerate a solar sail up to about 80%+ C, in a year or two. You have to do it fast because your laser beams do fuzz out over less than a light year. Slowing down, however, is another big, big problem! :singer: Robert Forward the physicist (still living) solved this, sort of, by having the solar sail separate into outer ring and central sail. Light from the launching lasers would bounce off the outer ring which would act like a reflecting concave mirror and SLOW the inner central sail. To get sufficient resolution in the laser light many light years away, however, he needed infrared focusing systems built out around the orbit of Neptune--they would be over 10,000 miles across!! And made of ultra-thin film imprinted with a holographic "lens". That's right, an imaging system larger than the planet Earth. Piece of cake. :eek2:

[TheFaithfulStone]

Why not just use brute force? If we cannot go as fast as light, lets just go as fast as we can. How fast can current technologies accellerate something in space? Could we hit .5c or better?

 

Hey, this thread isn't about things that are possible!

 

I'd say current technologies make interstellar travel impossible. Period. Slightly advanced technologies make it LESS impossible, but still improbable.

 

You need super-advanced technologies or breakthrough physics to make it work.

 

TFS

[Jay-qu]

I like the slightly adv. tech ideas, because it gives me hope that it could work in my lifetime - either that or I have to come up with a way to extened my lifetime..

 

who wants to help me design a theoretical ship? we can start a thread about it, discuss everything from its propulsion system to cup holders :phones: we can name it the hypo-express.. maybe the name needs a little work, but let me know if your interested;)

[TheFaithfulStone]

sounds like fun.

 

i've always wondered what the bathroom would be like in a space ship...

 

but i can't imagine anything pleasant.

[CraigD]

I rather liked the scheme in Norman Spinrad’s 1983 novel, The Void Captain’s Tale http://www.amazon.com/gp/product/0312868251, which involved a sort of electromechanically enhanced female orgasm so intense it renders the Pilot perpetually dysfunctional for ordinary sex.

 

The psychotopic “fish eggs” in Tom Dehaven’s “Freaks Amore”, though not actually travel, but instantaneous communication, were remarkable, and arguable one of the most obscure books of ca. 1980. My post in 4501 appears to be the only sensible hit for it on all of googledom!

[TheFaithfulStone]

which involved a sort of electromechanically enhanced female orgasm

 

EVERYONE wants to get assigned to engineering on that ship.

 

TFS

[Pyrotex]

...who wants to help me design a theoretical ship? ...

I would love to. It's been kind of a hobby of mine for 50 years. :hyper:

[Jay-qu]

cool well I will start a thread shortly - but right now I have to knick off to university and learn some more :D

[Qfwfq]

Slowing down, however, is another big, big problem! ;) Robert Forward the physicist (still living) solved this, sort of, by having the solar sail separate into outer ring and central sail. Light from the launching lasers would bounce off the outer ring which would act like a reflecting concave mirror and SLOW the inner central sail.

Even with enough resolution, how do you get the third law of motion kicked out the window? It sounds like blowing on the sail of the boat that you're on.

[Jay-qu]

Even with enough resolution, how do you get the third law of motion kicked out the window? It sounds like blowing on the sail of the boat that you're on.

lol i thought exactly the same thing.. at best it will only cancel out its own impulse

[TheFaithfulStone]

I think it would work. The Outer Ring is separate from the central part. The light bounces off of it, and then hits the center from the other side. The Outer Ring continues to accelerate, while the center part slows down.

 

Of course... you still have to build a lens the size of a planet in interplanetary space and keep it from getting scratched by a passing comet or something.

 

TFS

[betrayer_of_hope]

It must be the determinist in me, but I dont see how you can affect something physically just by measuring it.

 

By measuring it, you become a part of it. We are not independent observers. I'll have to look through Tao of Physics again to give you a proper answer though.

 

As for FTL travel, I think our thoughts at least travel faster than light. BTW can anyone shed some some light on a report I readsome time ago, about some Australian scientist who proposed that the speed of light is slowing down? I would help if I could remember where I read it:doh:

[Pyrotex]

...some Australian scientist who proposed that the speed of light is slowing down? I would help if I could remember where I read it:doh:

I may be wrong, but I think the "scientist" is part of a Creation Science group that is trying to convince segments of the christian community that physics and cosmology have it all wrong, and that the universe is only 8,372 years old. (Or some such number, approximately).

 

Until I hear some other voices on this subject, I won't take it very seriously.

[Jay-qu]

I do also remember the report you are talking of.. my teacher told us about it last year, but I also do not remember where it was :shrug:

[Qfwfq]

The Outer Ring continues to accelerate, while the center part slows down.

Except that it wouldn't last long.

[Pyrotex]

I do also remember the report you are talking of.. my teacher told us about it last year, but I also do not remember where it was :surprise:

I found it. Below is a link that will tell you all about the Australian who claims to have a theory that the speed of light use to be much faster than it is today, and therefore, the universe may be only 6-7 thousand years old.

 

http://www.talkorigins.org/faqs/c-decay.html

 

Two points: this person claims up front that his theory was invented to support the Genesis version of creation; and there are so many holes in the theory that even the Creation Science Institute has distanced itself from this "c-decay" theory.