Celestia Forums

Ladies and gentlemen, beware the person with high iq that has way to much time on his hands. <my favorite history profs statement when i turned in a term paper.

During the last few weeks, after my loving, thoughtful, wonderful wife decided upon finding the discarded manuscript of a science fiction novel and told "do something with it"

Well i have, and in the process, stumbled across some research i had done some years ago while in college.

So, if anyone is interested, lets look at economic viable interplanetary transportation. (which will open the door to plausable FTL drive theories)

Arthur C. Clarke invisioned a nuclear powered spacecraft that used a plasma exhaust to provide thrust to make the transit to Jupiter. When he wrote the book, we had nuclear powered ships, so the idea was plausable, and within reason to build. The problem at the time was the simple fact of history that the United States was fighting a war in Vietnam that the politicians were not gonna let us win. (Alright, I'm ex army and lost 18 realitives in that fiasco)

The orbting space station, the Aries space craft, the moon base, all feasable and all within reach, at least in theory.

Jump to the present, scientists have managed to harness nuclear fusion, granted not on a substantial level, but it has been done. So, the next step, would be to put that reactor on a spacecraft and see if it really works.

What is needed for fuel? Deutritium, or heavy water. Ok, where we gonna come up with that?

Well, if someone can come up with a way to catch comets, that is one solution, or how about mining Europa? (Shell or Exxon will love that idea)

Okay, we have a supply of heavy water, now a ship to use it.

Well, Jerry Pournelle wrote short story in which just such a craft was used.
Basically it was a spinning cylinder with a large tank on one end, a reactor somewhere in the middle, and a charged screen at the other end to create charged ions to propel the ship.

Okay, so we have a ship that is capable of accelerating at one gee, or to keep it simple, say boosts at half a gee, that still makes a transit from earth to jupiter in less than 3 months. Not quite rapid transit, more along the wagon trains of the old west, but at this point, remember, the industrial revolution was fueled by sea travel using sails.

So we have mining colonies in the asteroid belt, probably on some of the outer planets, and the moons of saturn and jupiter. Raw material shipped back to earth on glorified barges, people transiting out bound on the same ships, and we have a nice little economy going. What next?

Well, some bright eyed, bushy tailed engineer, (never trust an engineer, they design something and then leave it to the rest of us to make it work) comes in to work one day at ACME SPACECRAFT Inc. and announces, "Hey, why not just build a ship, have it boost at one gee and go to Alpha Centauri!" and promptly designs the ship.

Now that is where things get interesting.

Consider that after a year of accelerating at one gravity, the ship will be travelling at 99.9 percent c. Ok, the crew has long been subjected to realitivistic time dialiatio, so they aint aging as fast as the rest of us, but there is something that hasn't been considered in most of the science fiction that uses this idea.... realitivistic mass.

You get something travelling that fast, and the mass of said object increases expotentially. At somepoint the realitivistic mass is going to equal that of a blackhole, and that is going to be the kicker. That kind of gravity well warps spacetime. So what happens?

Three possibilities under the present thoughts on physics.
1. The craft drops into subspace and blasts along for a bit then pops back out who knows where. (I think lost in space had this plot)

2. A short lived worm hole opens, the ship jumps from point a to point b in a straight line.

3. The craft simply goes "poof" and we never see it or the crew again.

As soon as i get all the math, theories and references gathered up to add to this post, this is a start.

Oh, anyone think they can write a new version of Celestia to try and model this to see what would happen in a computer?

Seems like a good topic for discussion, who knows, this forum might just design the first working FTL drive, or at the very least, a new flavour for coca cola.... and pepsi just introduced vanilla pepsi...

Don't forget to protect your relativistic ships and passengers from the incoming flux of X and gamma rays, extremely high energy cosmic rays, relativistic dust particles, and that last, fatal, but Oh! So Bright! collision with a tiny (or maybe not so tiny) planetoid that they can't maneuver fast enough to avoid.

Nobody ever said getting to the stars would be easy.

Ad astra per aspera!

I was considering cloning my ex wives and have em sit on the nose cone and shoo away such things with fly swatters.

Okay, well seldon, looks like you were the first, okay, how bout this idea for the radiation, dust particles and the little things

Considering if using nuclear fusion, there should be, and probably will be an excessive amount of energy produced, so why not an electromagnetic field? Should be an easy thing to generate, and should handle most particles, even a strong enough magnectic field effects even non magnetic particles.

Just a thought, though it would be a good use for ex wives.

No comment.

I really don't have an adequate (i.e. don't have any formal) engineering physics background to know how that'd be done. One can always handwave (not the wives' ) about room-temperature superconductors and shaping the magnetic field to prevent disasterous side effects on the organics inside the vessel and stuff like that, I suppose.

I'd suggest doing some research on the prior studies done on these topics, to start. The extent of such research would depend on how believable a solution you want to provide. A brief Web search located an introductory article at http://www.setileague.org/articles/probes.htm.

(But I fear it may be overly optimistic about the density of matter in interstellar space. It varies a lot in different places and adds up over the length of the trip.)

Adelvunegv_waya wrote:Jump to the present, scientists have managed to harness nuclear fusion, granted not on a substantial level, but it has been done. So, the next step, would be to put that reactor on a spacecraft and see if it really works.

Surely not. Currently, the fusion reaction only proceeds for a short (but gradually increasing) time before the containment fails. The next step is to contain it for long enough to produce significant amounts of energy.

What is needed for fuel? Deutritium, or heavy water. Ok, where we gonna come up with that?

The fuel depends on the particular fusion reaction chosen. Different reactions generate different amounts of radioactivity, and require different temperatures to occur. But the fuel will likely be some variant on hydrogen (deuterium, tritium) or helium (helium-3) or both. These vary from very widely available (hydrogen) to pretty uncommon (helium-3, tritium).

Well, if someone can come up with a way to catch comets, that is one solution, or how about mining Europa? (Shell or Exxon will love that idea)

Mining of Jupiter's atmosphere for He-3 has been suggested; it would obviously require very large facilities.

Consider that after a year of accelerating at one gravity, the ship will be travelling at 99.9 percent c. Ok, the crew has long been subjected to realitivistic time dialiatio, so they aint aging as fast as the rest of us, but there is something that hasn't been considered in most of the science fiction that uses this idea.... realitivistic mass.

You get something travelling that fast, and the mass of said object increases expotentially. At somepoint the realitivistic mass is going to equal that of a blackhole, and that is going to be the kicker. That kind of gravity well warps spacetime. So what happens?

Nothing will happen. The object cannot become a black hole by travelling at a very high speed. What matters is the rest-mass, or invariant mass. Imagine that you travel at the same speed as this object at the end of its burn - you would think it stationary, so its mass is whatever it started out with minus the fuel expended - no mass increase. It's not a black hole according to you. Now, imagine that the crew threw me out before they started accelerating. Would I see a rocket or a black hole after the burn is complete? If I see a black hole, then why are you seeing a rocket? Answer: I don't see a black hole, I see a rocket.

Okay seldon, granted you have posted some interesting points.

And as far as having an engineering degree, well, my chosen fields of study were history, philosophy, anthropology, with a lot of courses in computer technology since it always has been a hobby.

However, if i may point out, some of the biggest advances in science and technology came not from people with college degrees in the fields, but average joes with a question and looked for a solution.

So, who is to say that the combined input of so many people such as the users of this forum, will not provide some answers?

Anyway, back to the math and a few other things dealing with this topic...


And what is wrong with using ex wives? you dont know mine.... wouldnt wish em on my worst enemy.

Adelvunegv_waya wrote:Considering if using nuclear fusion, there should be, and probably will be an excessive amount of energy produced, so why not an electromagnetic field? Should be an easy thing to generate, and should handle most particles, even a strong enough magnectic field effects even non magnetic particles.

Incoming particles will be travelling at extremely high speeds as far as the magnetic field is concerned. Even deflecting charged particles will be difficult, and uncharged particles will be nigh-on-impossible to deflect sufficiently. Interestingly, if you travel at sufficient speed the cosmic microwave background in the direction you're travelling will be blue-shifted to a degree that could make it hazardous, and even fatal.

From a paper written by Michael Fowler, who points out a few facts on the subject of mass and acceleration.

A unique phenomanon is often observed in particle accelerators, a dramatic shift in gravity field around the particle in motion, and the fact that the measured mass does increase, which, by all standards means that the following is true, m*c=infinate mass, or in simple terms, the energy required to boost to light speed would have to be infinate.

But we still have to consider the other little phenonomon observed, the distortion of the gravity field around the particles, thus the speculation that at near light speed, the realitivistic mass would have the same distorting effect on gravity around it.

Which then introduces the question, once again, once that mass hits a critical point, what happens next?

Also, have to point out, (from my training as army sniper) that a 7.62 round cant do much when it is thrown, because its mass aint too much, but fire it from a rifle, that mass is amplified....

A unique phenomanon is often observed in particle accelerators, a dramatic shift in gravity field around the particle in motion, and the fact that the measured mass does increase, which, by all standards means that the following is true, m*c=infinate mass, or in simple terms, the energy required to boost to light speed would have to be infinate.

But we still have to consider the other little phenonomon observed, the distortion of the gravity field around the particles, thus the speculation that at near light speed, the realitivistic mass would have the same distorting effect on gravity around it.

How do they detect gravitational distortion due to a subatomic particle? it sounds difficult...
I have read that current theory postulates that a relativistic object will dissipate its kinetic energy by emitting gravitational waves (which would presumably propagate out much like the waves from a motorboat). This would account for the distortions.

Also, have to point out, (from my training as army sniper) that a 7.62 round cant do much when it is thrown, because its mass aint too much, but fire it from a rifle, that mass is amplified....

No, the mass is unchanged, the kinetic energy is greater. This from the physics they teach at high-school... well, high school in Australia, anyway

Cheers,
Paul

As Paul stated, the mass of a 7.62 mm projectile isn't muiltiplied, it's energy is greater: e=mv^2, each doubling of velocity gives it four times the energy.

Accelerating a space ship to near C speeds? If the mass of an object increases as it approaches C as you are stating, then to keep the same acceleration we would also require an increase in the thrust. This would surely then limit the final velocity.

Space isn't a pure vacuum as far as i'm aware. At high speeds it would cause drag the same way as air resistance does here on earth. It would also follow a squared relationship w.r.t the speed. I'm not qualified enough to state what the relationship is at relativistic speeds. I'm an engineer so I'll let someone else work that out

All up I'd say that the amount of fuel required to acheive what you are proposing would be huge. This would of course make initial acceleration a problem. Must think about slowing down too!


I like your idea about the ex-wives and the fly squatter but if you really want to sheild against space debris then have some of my ex's as crew members, their personalities would repel almost anything. Hmm, doesn't say much for me though!

Alright, here is something i knew i had read about at somepoint, and after emailing an old physics prof who happens to love star trek, he reminded me of this one.

Granted, it aint ftl but it is pretty quick, about 25 years to alpha centauri.

to qoute "it would scoop up fuel from the space that it travelled through. It had a funnel out the front, about 2,000 kilometres across. This funnel was not made of solid stuff, but of electromagnetic fields that were generated by an enormous magnetic solenoid. Particles would be trapped by the funnel, fed to the fusion reactor, burnt and thrown out of the back of the Bussard Ramjet"

Then of course there is zero point energy, again a quote "vacuum is not nothing - no, it's made up of a strange sea of particles and anti-particles that wink into existence, and almost instantly, wink out again. Their coming and going creates their strange energy called the Zero Point Energy. This energy is huge - up to 1054 joules in each cubic metre. To put that into Plain English, there's enough Zero Point Energy in the vacuum in our tiny metal box to boil all of the oceans on our planet!
In 1997, scientists were able to measure, for the first time, the Zero Point Energy pushing two metal plates together."

http://www.abc.net.au/science/k2/moments/gmis9808.htm is the source of the information. so much for the fuel problem, kinda sorta.

food for thought.

and im still looking for the essays by clarke on some of this.
wish my last ex hadnt burned or trashed a lot of my books.

Adelvunegv_waya wrote:From a paper written by Michael Fowler, who points out a few facts on the subject of mass and acceleration.

A unique phenomanon is often observed in particle accelerators, a dramatic shift in gravity field around the particle in motion, and the fact that the measured mass does increase, which, by all standards means that the following is true, m*c=infinate mass, or in simple terms, the energy required to boost to light speed would have to be infinate.

But we still have to consider the other little phenonomon observed, the distortion of the gravity field around the particles, thus the speculation that at near light speed, the realitivistic mass would have the same distorting effect on gravity around it.

Which then introduces the question, once again, once that mass hits a critical point, what happens next?

I'd be very interested to know how Mr Fowler managed to measure the gravitational field around the sort of elementary particles you find in accelerators. They have tiny masses, and even at gamma factors of 1000 (about 99.99995% of light speed) they'd have a relativistic mass of only around only 10^-18kg. So even if the relativistic mass mattered to the gravitational field (it doesn't, directly) I don't see how it's possible to measure the field.

The relativistic mass is an artifact of the teaching of relativity. It used to be used to help people across to relativity from Newtonian mechanics, but it's ambiguous in special relativity and outright irrelevant in general relativity (which is what matters when gravity is involved).

An infinite amount of energy would be required to accelerate an object to light speed, but it's better understood in terms of proper time intervals than relativistic mass.

Also, have to point out, (from my training as army sniper) that a 7.62 round cant do much when it is thrown, because its mass aint too much, but fire it from a rifle, that mass is amplified....

It's the momentum (mass x velocity) and kinetic energy (half x mass x velocity-squared) that increase, not the mass. Relativistic mass has nothing to do with that.

I once read somewhere that a science fiction story is allowed one major implausability. (I know most have several, but thats what I read).

In the case of my own stories (generally developed for prospective RPG backgrounds), the implausability is usually a workable method of FTL.

Science Fiction has generated many fictional methods of getting from A to B very fast. (There was one particularly nasty story where mankind actually breaks through into Hyperspace, and discovers that its actually slower than normal space).

Greg Bear came up with a nice method in 'Moving Mars', where a scientist discovers the descriptor particle that defines an object's location in space, and then works out a means of re-writing it!

A personal favourite is known as 'Stutterwarp'. This was developed for the semi-hard-science fiction RPG '2300 AD'. It employed a drive that used a macroscale quantum tunnelling concept. The ship only travels a few hundred yards with every drive cycle, but the drive could be cycled VERY fast, thus producing effective FTL travel.

My current line of thought is that, if we ever discover a means to travel faster than light, the method will be a lot weirder than we think. It may even involve organic processes (I don't mean any organic processes on Earth, btw).

Right now, however, I don't think anyone has postulated a real-world method that would be workable, given current knowledge.

From a story perspective, here's a thought. When a character in a novel talks about driving a car, they generally don't explain the workings of the internal combustion engine. The fact that it occurs is a given, even to people who don't understand engines. The wheels go round and the car moves. With FTL, the same idea can apply, UNLESS the method of FTL IS the story.

I won't even mention my re-write of Flash Gordon where Mongo is a Psuedo-Dyson Sphere, that we call Jupiter. (That wasn't one of my hard-science fiction ideas )

Ah, the curse of a wild imagination

Moral of the story: Never let science get in the way of a good plotline, IF you can tell it well enough that people don't notice the bad science.

Cheers,

Cormoran

The Alistair Reynolds version of FTL (in Redemption Ark):

Vacuum state zero: normal
Vacuum state one: inertia suppression
Vacuum state two: zero mass
Vacuum state three: imaginary mass

Therefore in state three you could in theory go faster than the speed of light.

What actually happens is that the causality violation this would cause gives the universe massive problems and you cease to ever have existed.

Personally, I don't think a physical "ship" will ever reach FTL speeds, at least not in *our* physical universe. Einstein's work has already been mentioned -- as an object approaches the speed of light, it's mass becomes infinate, thus requiring infinate+1 power to move the object even faster. Since we can't create infinate+1 power this means the object *must* have zero mass, which is not possible in our physical universe, that I know of.

And no, anti-gravity, super-conductors, or any other kind of "levitation" won't work because they do not change an object's mass to zero. They merely manipulate gravity, of which there is very little of to be manipulated in outer space.

Rather, I think a ship will remain stationary (above the object it is leaving), open a "doorway" that positions the ship at it's destination, then land. The "doorway" could be another dimension, warped time-space, hyper-space, or whatever. Personally, I think it will be something we haven't even imagined yet, like thought itself.

I've always had a little trouble with the causality violation aspect of FTL travel. It implies (to me, a layman) that reality only travels at the speed of light, and stuff we haven't seen hasn't technically happened yet. I wonder if thats a manifestation of the Observer effect from Quantum Physics?

Our knowledge of physics is theory applied to observed phenomena, and underpinned with mathematical proofs. We have a few more proofs to find, more stuff to observe, and therefore more theories to generate. Hidden away in these three related aspects may be the key to infinity.

150 years ago, heavier than air flight was impossible. It would never happen. 50 years ago, there'd be a future market for perhaps 10 good computers in the entire world (some guy from IBM said that).

In 1960 or thereabouts, some scientist said spaceflight was impossible (please note that this was AFTER Sputnik).

Any workable method of FTL travel will require a large number of large books to be thrown away. New ones will be written. In time they'll be thrown away too, ad infinitum....

In the meantime, FTL is just Science-fiction's way of moving the plot along. I hope it doesn't remain that way. It offends my sense of the rightness of the universe to think FTL is impossible.

Cormoran

I, too, am a layman, with very little knowledge of relativity other than what I get from my science fiction library. I see where you are coming from with the causality violation statement, but from my perspective, we aren't saying that reality only travels at the speed of light, but that the _effects_ of reality travel at the speed of light. There are innumerable things that have already happened, say, 6 billion light years away, that cannot possibly have any effect on us until 6 billion years from now. That doesn't mean they haven't happened. Shoot, for all we know, the entire universe more than 1 million light years away ceased to exist yesterday, but we won't find out until August 21, 1,002,003 AD.

Tim

Cormoran wrote:It offends my sense of the rightness of the universe to think FTL is impossible.

Oh, FTL travel is certainly possible, as tachyons do it all the time, if the theory behind their existence is correct. The question really is, how much mass, if any at all, can exceed the speed of light?

Aside from this, would the object traveling at FTL speeds start going backwards in time? This is thought to be one possibility.

Cormoran wrote:150 years ago, heavier than air flight was impossible. It would never happen. 50 years ago, there'd be a future market for perhaps 10 good computers in the entire world (some guy from IBM said that).

One assertion was based on engineering (there are no steam-powered aircraft - we had to wait for the internal combustion engine) the other on economic assessment (how many companies predict future economic conditions correctly, in a consistent manner?) Neither of these examples are relevant to FTL. The assertion that FTL is impossible is not based on engineering problems nor on economic predictions.

In 1960 or thereabouts, some scientist said spaceflight was impossible (please note that this was AFTER Sputnik).

This scientist couldn't have been very good at his/her job, then. Can you provide a name?

In the meantime, FTL is just Science-fiction's way of moving the plot along. I hope it doesn't remain that way. It offends my sense of the rightness of the universe to think FTL is impossible.

I don't see any reason why the universe should be constructed so that other stars are accessible within a fraction of a human lifetime. If it were to be so constructed, we'd just complain that getting to our nearest neighbour galaxy was so much more difficult than just getting to the nearest star.

don wrote:Oh, FTL travel is certainly possible, as tachyons do it all the time, if the theory behind their existence is correct.

"Things can travel FTL if particles defined to be able to travel FTL exist"?
The trouble with tachyons, apart from the lack of evidence for their existence, is that

a) There's no reason to believe that they interact with tardyons (slower-than-light) particles, so there's no reason to believe that converting a ship into them or sending a message using them is possible.

b) Even if you could send a message or ship through converting it into tachyons, the message/ship would not travel FTL. There is a technical demonstration of this at

http://www.morleysoft.freeserve.co.uk/p ... hyons.html

Although the carrier particles (tachyons) are FTL, the modulated wave they carry (the message) is not. An example from practical experience would be the slowing down of light in a transparent material - although the carrier particles, photons, always travel at the speed of light, the combined disturbance they carry does not travel at this speed through the material.

c) There are some causality violation issues, but these seem very unpopular.

The question really is, how much mass, if any at all, can exceed the speed of light?

Tachyons have imaginary mass (fittingly).

Aside from this, would the object traveling at FTL speeds start going backwards in time? This is thought to be one possibility.

It would be in the volume of spacetime diagrams normally marked as "elsewhere" (outside the light cone of an observer). In other words, it's completely arbitrary as to whether the tachyonic object is travelling forwards or backwards in time.