quote:

ORIGINAL: zzodr

quote:

ORIGINAL: mdiehl


Well, but does it have to? If a solar sail generated some small amount of thrust constantly out to the heliopause, wouldn't the spaceship-beastie be moving pretty fast?

Fast in race car terms, yes, very. Fast as in travelling to another star system? No.
Voyager 1 is now entering this area where the solar energy from our Sun is negligible.

In 100 days a sail could reach 16,000 kilometers per hour (10,000 miles per hour); in one year it could reach 58,000 kilometers per hour (36,000 miles per hour). In just three years, a solar sail could reach a speed of over 160,000 kilometers per hour (100,000 miles per hour). At that speed you could reach Pluto in less than five years. In comparison, the New Horizons misson to Pluto, using chemical propulsion and a gravity-assist from Jupiter, is planned to take nine years to reach its target.

Still, 160,000 kilometers per hour (100,000 miles per hour) is still only 0.00015 the speed of light. It would take about 1,000 years for a solar sail to reach one-tenth the speed of light, even with light shining on it continuously. This emphasizes just how hard interstellar flight is.

http://www.discoversolarenergy.com/solar/sails.htm

quote:

ORIGINAL: Bullwinkle58
I assume you presume the craft begins at rest? That need not be the case. Disposable strap-on engines would work well to boost it to the speeds you end up at, with the sails continuing the acceleration from there.

quote:

ORIGINAL: JWE

quote:

ORIGINAL: Bullwinkle58
I assume you presume the craft begins at rest? That need not be the case. Disposable strap-on engines would work well to boost it to the speeds you end up at, with the sails continuing the acceleration from there.

The mass penalties for the fuel are insane, self limiting actually. Assuming even a 1g boost, for any appreciable time sufficient to move zzodr's decimal point even one place to the right, the fuel mass would be rather large. Conservation of momentum. That's why many sci-fi writers assume a Bussard configuration.

quote:

ORIGINAL: LoBaron
I always wondered if far in the future a long range continuousely operating engine comparable to scramjets would be able to tap free hydrogen or energies of the vacuum.
Stanislav Lem described such an propulsion method in Fiasko. Is that similar to a Bussard configuration? I think Bussard is a fusion reactor type?

quote:

ORIGINAL: JWE

The wierd thing is trying to explain physics in words. It's so much easier in math, but then most people haven't learned to speak that language, so Woof !!

It's like trying to explain to an orchestra how to play a Beethoven symphony, when nobody knows how to read music. One can use words, but oh my, the horror , the misunderstandings, and the decades. Just a simple example, and it's on-topic, too (imagine that).

One space ship (traveling E at speed .9c) sends a radio signal to andother space ship (traveling SW at speed .9c). Propagation time of the signal is d'/c. Doppler will have an effect with respect to the receiving ship in so far as her v stretches out (or shortens) the wavelength of the signal. The receiver will get the signal at t'=d'/c but it must be processed to account for v.

Everything that happens, every single little thing the happens, is evaluated on the basis of 2 inertial reference frames - Mr .9c E and Mr .9c SW. An observer who is not aboard either one of the ships can evaluate these things for himself (we have), but the observer must, simply must, be in an inertial reference frame of his own (our's were) that is relative to the two ships. That's why it's called relativity.

There is no such thing as an observer sitting outside the system with stopwatches and such. Being outside the system means solutions are utterly irrelevant. That's one of the many reasons that I and many of my colleagues believe.

quote:

ORIGINAL: JWE

quote:

ORIGINAL: Bullwinkle58
I assume you presume the craft begins at rest? That need not be the case. Disposable strap-on engines would work well to boost it to the speeds you end up at, with the sails continuing the acceleration from there.

The mass penalties for the fuel are insane, self limiting actually. Assuming even a 1g boost, for any appreciable time sufficient to move zzodr's decimal point even one place to the right, the fuel mass would be rather large. Conservation of momentum. That's why many sci-fi writers assume a Bussard configuration.

quote:

ORIGINAL: Nikademus
John, your making my head hurt.

No wonder Roddenberry went for Warp Drive. Easier to technospeak it.

quote:

ORIGINAL: JWE

quote:

ORIGINAL: Nikademus
John, your making my head hurt.

No wonder Roddenberry went for Warp Drive. Easier to technospeak it.

You think so? Just take a peek at Miguel Alcubierre's metric tensor; and the idea of Constant Velocity Bubbles from Brendan McMonigal, Geraint lewis, and Philip O'Byrne; or The Matter of Matter, E. Birkhauser, J. Crayne, and J. Eldredge; and "Mass Denisty Profiles of Stuff", Block/Bosma.

Woof !! It's a wonder Roddenberry's head didn't explode.

quote:

ORIGINAL: Kwik E Mart
string theory always makes my head hurt...and i majored in physics! [&:]

quote:

ORIGINAL: Kwik E Mart
string theory always makes my head hurt...and i majored in physics! [&:]

quote:

ORIGINAL: JWE

quote:

ORIGINAL: Kwik E Mart
string theory always makes my head hurt...and i majored in physics! [&:]

Mine too ... and so did I.

If you really care, I take the Philosophy of Science courses at USC/Arizona every couple years or so. Now I am in Alabama, I'm signed up at UA Huntsville.

These are not your caring and sharing, Govt sponsored, girlie, useless, filosofy courses. These are real courses, taught by real people, who speak math. If you think about it, you can see that the windows and limitations of our understanding are defined by our philosophy. Take a good PoS course and many things will become clear.

quote:

ORIGINAL: USS America

quote:

ORIGINAL: JWE

quote:

ORIGINAL: Kwik E Mart
string theory always makes my head hurt...and i majored in physics! [&:]

Mine too ... and so did I.

If you really care, I take the Philosophy of Science courses at USC/Arizona every couple years or so. Now I am in Alabama, I'm signed up at UA Huntsville.

These are not your caring and sharing, Govt sponsored, girlie, useless, filosofy courses. These are real courses, taught by real people, who speak math. If you think about it, you can see that the windows and limitations of our understanding are defined by our philosophy. Take a good PoS course and many things will become clear.

That sounds rather twisted, John, and rather fun! I might have to look for one of those classes when there is once again free time in my life. [8D]

quote:

ORIGINAL: USS America

quote:

ORIGINAL: JWE

quote:

ORIGINAL: Kwik E Mart
string theory always makes my head hurt...and i majored in physics! [&:]

Mine too ... and so did I.

If you really care, I take the Philosophy of Science courses at USC/Arizona every couple years or so. Now I am in Alabama, I'm signed up at UA Huntsville.

These are not your caring and sharing, Govt sponsored, girlie, useless, filosofy courses. These are real courses, taught by real people, who speak math. If you think about it, you can see that the windows and limitations of our understanding are defined by our philosophy. Take a good PoS course and many things will become clear.

That sounds rather twisted, John, and rather fun! I might have to look for one of those classes when there is once again free time in my life. [8D]

quote:

ORIGINAL: wdolson

If you were traveling at the speed of light, time would essentially stop and you would hear nothing. Another way to look at it would be the radio waves would be traveling exactly the same speed you were.

If you were traveling a little less than the speed of light, you would pick up radio, but it would be stuff broadcast after you left (you would be going slower than the radio waves), but it would be dramatically downshifted in frequency to a point where you would probably need a computer to speed it back up again, and collecting an hour's worth of programming would take a few years.

If you were able to exceed the speed of light, with some kind of drive only known to science fiction today, you would outrun the radio and most likely hear nothing while you were traveling, but when you stopped, you would be able to pick up broadcasts from many years ago, depending on how far away you were. The radio waves would also be very diffuse, the strength of the signal declines at the cube of the distance (the signal is radiating out from Earth in a sphere), so you would need a super sophisticated receiver to be able to pick up anything. Radio noise put out by our sun would probably drown out much of the signal after some distance. You might be able to pick up a bit of a radio hot spot where Earth was when the broadcasts you are picking up were sent, but all you would be able to do is pick up that something was transmitted.

SETI tries to pick up coherent radio patterns in signals from other stars. So far they haven't found anything definitive. They do have some pretty sophisticated receiver arrays (and would like to build even more sophisticated arrays). I doubt you'd be able to pick up anything coherent with commercially available equipment even if planets around nearby stars were broadcasting.

And always remember 285,000 miles per second, it's not only a good idea, it's the law. [:D]

Bill

quote:

ORIGINAL: Ddog

quote:

ORIGINAL: wdolson

If you were traveling at the speed of light, time would essentially stop and you would hear nothing. Another way to look at it would be the radio waves would be traveling exactly the same speed you were.

If you were traveling a little less than the speed of light, you would pick up radio, but it would be stuff broadcast after you left (you would be going slower than the radio waves), but it would be dramatically downshifted in frequency to a point where you would probably need a computer to speed it back up again, and collecting an hour's worth of programming would take a few years.

If you were able to exceed the speed of light, with some kind of drive only known to science fiction today, you would outrun the radio and most likely hear nothing while you were traveling, but when you stopped, you would be able to pick up broadcasts from many years ago, depending on how far away you were. The radio waves would also be very diffuse, the strength of the signal declines at the cube of the distance (the signal is radiating out from Earth in a sphere), so you would need a super sophisticated receiver to be able to pick up anything. Radio noise put out by our sun would probably drown out much of the signal after some distance. You might be able to pick up a bit of a radio hot spot where Earth was when the broadcasts you are picking up were sent, but all you would be able to do is pick up that something was transmitted.

SETI tries to pick up coherent radio patterns in signals from other stars. So far they haven't found anything definitive. They do have some pretty sophisticated receiver arrays (and would like to build even more sophisticated arrays). I doubt you'd be able to pick up anything coherent with commercially available equipment even if planets around nearby stars were broadcasting.

And always remember 285,000 miles per second, it's not only a good idea, it's the law. [:D]

Bill

Bill,

I think you may be wrong about the speed of light, but not the radio lol A friend I grew up with (the guy who actually got me playing wargames such as Tobruk, Squad Leader, Luftwaffe, etc.) teaches at the University of Minn. Deluth. He has been working on a project involving neutrinos for about 20 years. If you seen the movie 2012, nuetrinos destroy the earth lol but at least the movie got the reciever deep in the ground in India correct. There are 2 recievers that my freind worked at, one buried deep in the Alps in Italy, and the other deep in some mountain in Japan. Anyway, these neutrinos pass thru the earth and never slow down, so the mountains act as a filter. I was in the Marines, so I won't pretend to know a whole lot about Astrophysics. But last year they fired nuetrinos from from some sort of generator to a receiver and they traveled faster than light. Then there was speculation about if Einstien was correct they would of had to of received the neutrinos before they were fired.

I'll include an article, and you can do your own research if you are interested.....it hurts my brain [&:]

http://www.nytimes.com/2011/09/30/opinion/30iht-eddas30.html

quote:

ORIGINAL: koniu

quote:

ORIGINAL: Ddog

quote:

ORIGINAL: wdolson

If you were traveling at the speed of light, time would essentially stop and you would hear nothing. Another way to look at it would be the radio waves would be traveling exactly the same speed you were.

If you were traveling a little less than the speed of light, you would pick up radio, but it would be stuff broadcast after you left (you would be going slower than the radio waves), but it would be dramatically downshifted in frequency to a point where you would probably need a computer to speed it back up again, and collecting an hour's worth of programming would take a few years.

If you were able to exceed the speed of light, with some kind of drive only known to science fiction today, you would outrun the radio and most likely hear nothing while you were traveling, but when you stopped, you would be able to pick up broadcasts from many years ago, depending on how far away you were. The radio waves would also be very diffuse, the strength of the signal declines at the cube of the distance (the signal is radiating out from Earth in a sphere), so you would need a super sophisticated receiver to be able to pick up anything. Radio noise put out by our sun would probably drown out much of the signal after some distance. You might be able to pick up a bit of a radio hot spot where Earth was when the broadcasts you are picking up were sent, but all you would be able to do is pick up that something was transmitted.

SETI tries to pick up coherent radio patterns in signals from other stars. So far they haven't found anything definitive. They do have some pretty sophisticated receiver arrays (and would like to build even more sophisticated arrays). I doubt you'd be able to pick up anything coherent with commercially available equipment even if planets around nearby stars were broadcasting.

And always remember 285,000 miles per second, it's not only a good idea, it's the law. [:D]

Bill

Bill,

I think you may be wrong about the speed of light, but not the radio lol A friend I grew up with (the guy who actually got me playing wargames such as Tobruk, Squad Leader, Luftwaffe, etc.) teaches at the University of Minn. Deluth. He has been working on a project involving neutrinos for about 20 years. If you seen the movie 2012, nuetrinos destroy the earth lol but at least the movie got the reciever deep in the ground in India correct. There are 2 recievers that my freind worked at, one buried deep in the Alps in Italy, and the other deep in some mountain in Japan. Anyway, these neutrinos pass thru the earth and never slow down, so the mountains act as a filter. I was in the Marines, so I won't pretend to know a whole lot about Astrophysics. But last year they fired nuetrinos from from some sort of generator to a receiver and they traveled faster than light. Then there was speculation about if Einstien was correct they would of had to of received the neutrinos before they were fired.

I'll include an article, and you can do your own research if you are interested.....it hurts my brain [&:]

http://www.nytimes.com/2011/09/30/opinion/30iht-eddas30.html

I must find source of that but i hear in TV that after they check everything again they found some kind on technical multifunction and neutrinos where traveling with speed of light. It was lose cable or something like that.:)

EDIT. It was lose cable between computer and GPS module used to measure travel time of neutrinos between point A and B.
They suspecting also that synchronization between computers where corrupted

quote:

ORIGINAL: Knavey

Ummm...even with all the deep thought going on in this thread, it is still easier to figure out astrophysics and neutrinos than it is to understand the air and ground combat routines of WitP - AE. Obviously BORKED.[:D]

quote:

ORIGINAL: Knavey
Ummm...even with all the deep thought going on in this thread, it is still easier to figure out astrophysics and neutrinos than it is to understand the air and ground combat routines of WitP - AE. Obviously BORKED.[:D]

quote:

ORIGINAL: zzodr

Yes, sadly, we won't be going anywhere beyond our solar system with manned spacecraft. As much as discovery of other planets intrigues and excites us.