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FTL Travel

Fallowfox

Are we moomin, or are we dancer?
That speed is mass glitch is actually more of a fundamental function of where stuff in our universe comes from. Everything is basically a relation of speed, mass, and time. You can't change one without messing up the other, because those are the fundamental components we are made of. You would have to literally remove parts of yourself to move faster, but then what's the point, since you won't be the one moving any more?

More or less, right. I disagree with this point though, by the time you've accelerated a space craft to 99% light speed, chopping off your arms and flinging them out of the window isn't going to make any tangible difference to your velocity. Most of your mass will be concentrated in the immense space craft, rather than your body.

It would be like giving astronauts a haircut, in order to speed up the space shuttle...technically it would work, but you know...sort of pointless.
 

Rassah

Well-Known Member
I meant if we were to imagine you moving just by yourself (your body), and you would have to remove yourself on an atomic level. I.e. you would have to disintegrate yourself. But yeah.
 

RedSavage

Rattlesnake Flavored
Stupid question time.
All this FTL talk...say we have a ship that can. Or, alternatively, near the speed of light.

What happened if it hits a fricken asteroid? Space is frictionless and all and doesn't stop things. No air. But if a rock or something wandered into it's path. Yanno. Ship go boom?

Seems like a rather practical obstacle. Anything at near light spees is stupidly destructive.
 

Rassah

Well-Known Member
I think you'll get a nuclear explosion from the atoms being completely split at that speed. Or, conversely, the two will pass through each other because the atoms are full of empty space, and the atomic force won't have time to react. Maybe a bit of both, where some atoms do hit, and although you won't have a massive explosion, you'll have a massive blast of radiation?

Fallow?
 

Fallowfox

Are we moomin, or are we dancer?
I think you'll get a nuclear explosion from the atoms being completely split at that speed. Or, conversely, the two will pass through each other because the atoms are full of empty space, and the atomic force won't have time to react. Maybe a bit of both, where some atoms do hit, and although you won't have a massive explosion, you'll have a massive blast of radiation?

Fallow?

The atoms wouldn't pass through each other for the same reason you don't fall through your chair when you sit down.

It would be unlikely that you would hit anything significant traveling through interstellar space, maybe fluffy dust grains would be a problem, but if you did, it would probably provide so much energy that your ship would be dashed to pieces. If the ship was made of aluminum, the aluminum would become hot enough to react with the air inside the craft.

This is how missile-defence systems work. The interceptor missiles don't actually have any explosived on board, but they travel at several km/s relative to the incoming missile, so the impact provides enough energy to dash the missile to pieces.


Maybe you could protect your ship from potential impacts with a magnetic field or lasers to vapourise hazardous grit.
 

Rassah

Well-Known Member
At speeds like that, you have to stop thinking of it as a fast traveling object, and start thinking of it as matter traveling in a matter collider. There won't be time for anything to heat up, and I'm pretty sure the impact would be on an atomic rather than molecular level. Every bit of dust could result in a micro nuclear explosion.
 

LazerMaster5

Lost in the Static
I like the idea of FTL travel much better than the alternative, being sealed in cryogenic tubes. Imagine waking crash landed on a planet where the apes are sentient and the humans are hunted. Or even worse, how about being stuck in a ship populated by nasty monsters and a captain gone crazy, like in Pandorum?
 

Astus

Well Known Foxxo
You people have no idea how strangely happy this thread made me; instead of reading and hearing about all of the "Mike doesn't like me anymore!" and about all the ignorant people in the world, I now feel like there are still some people out there who care about understanding things and having intelligent conversation.

Just felt like I had to say that.
 
Closest you're going to get to a relativistic spacecraft is a Bussard ramjet, an Orion that substitutes standard fission shaped charges for pure antimatter or antimatter-catalyzed nuclear fusion shaped charges, or some sort of nigh-magical power source and godlike material sciences that can make a useful photon rocket actually viable for deep interstellar exploration.

All of the aforementioned propulsion systems have a fair number of fundamental flaws, however.

But FTL?

Unsure about that, but we'll see.
 
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Saiko

GTWT Survivor
What we really need to do is figure out how gravity and the Higgs Mechanism work. Then we could hope to do some really badass stuff with warp drives and such. Until we can master gravity, though, I don't think we have much chance at FTL travel.
 

Khaki

AFP's Most Unwanted
Might as well turn the Moon into a penal colony and get the convicts growing grain to drop back to Earth via a electromagnetic acceleration ramp.
 

Fallowfox

Are we moomin, or are we dancer?
Closest you're going to get to a relativistic spacecraft is a Bussard ramjet, an Orion that substitutes standard fission shaped charges for pure antimatter or antimatter-catalyzed nuclear fusion shaped charges, or some sort of nigh-magical power source and godlike material sciences that can make a useful photon rocket actually viable for deep interstellar exploration.

All of the aforementioned propulsion systems have a fair number of fundamental flaws, however.

But FTL?

Unsure about that, but we'll see.

https://en.wikipedia.org/wiki/Alcubierre_drive ?
 

Gryphoneer

20 Quatloos on "disruptive"
There's only two categories of FTL flight: those schemes that are rendered impossible by relativity, and those rendered impossible by every practical reason imaginable. All of the latter need literally astronomical amounts of energy to work, some even more than there is in the observable universe! Where do you get all that juice? How to sustain its generation? The so-called "real-life warp drive" imagined by Doc Alcubierre for fun may not violate known phyics but runs into the same problems. How do you produce all that exotic matter? How do you form it into a bubble? And, since the hypothetical ship inside this deformed local spacetime can't interact with the outisde universe, how does it manipulate the exotic matter sphere and steer or stop? Under scrutiny, FTL in all its forms turns out to be a pipe dream.

Fallow, you majoring/minoring in physics? Then be so kind to get back at this; a few years back I heard on a pop-science show even spaceflight at relativistic speeds is, uh, non-trivial, as you're not only cooked by star light turned into high-energy UV radiation by the Doppler effect (or was it Lorentz contraction..?) but also that your ship's mass increases the closer you get to lightspeed and it collapses into itself once you cross the threshold.
 

Fallowfox

Are we moomin, or are we dancer?
There's only two categories of FTL flight: those schemes that are rendered impossible by relativity, and those rendered impossible by every practical reason imaginable. All of the latter need literally astronomical amounts of energy to work, some even more than there is in the observable universe! Where do you get all that juice? How to sustain its generation? The so-called "real-life warp drive" imagined by Doc Alcubierre for fun may not violate known phyics but runs into the same problems. How do you produce all that exotic matter? How do you form it into a bubble? And, since the hypothetical ship inside this deformed local spacetime can't interact with the outisde universe, how does it manipulate the exotic matter sphere and steer or stop? Under scrutiny, FTL in all its forms turns out to be a pipe dream.

Fallow, you majoring/minoring in physics? Then be so kind to get back at this; a few years back I heard on a pop-science show even spaceflight at relativistic speeds is, uh, non-trivial, as you're not only cooked by star light turned into high-energy UV radiation by the Doppler effect (or was it Lorentz contraction..?) but also that your ship's mass increases the closer you get to lightspeed and it collapses into itself once you cross the threshold.

Geology. Almost all the physics I've studied has been classical, so I've spoken with my brother about this subject, who studies astrophysics.

You're correct that objects traveling at great speed become more massive from the perspective of a bystander in an inertial reference frame.
Inside the spaceship's point of view, however it would appear as if the ship's mass was constant and that the rest of the objects flying by were becoming more massive as you accelerated relative to them.
My brother reasoned that, because from the perspective of the ship, its own mass isn't increasing, that it would not collapse upon itself under its own gravity.


I am not sure about the speculation about the Doppler effect; how fast would you need to go to make the frequency of incoming light high enough to cause damage, and would their concentration ever be high enough to be significant? I don't know.

edit: assuming that space is full of microwave background radiation 3kelvin, and wavelength 0.03m, traveling at 99% light speed would only cause the light to appear to have a wavelength of 42mm, which is still in the microwave region.
[gamma= 1/root(1-(vv/cc))] = 1/root(0.99*0.99/1) ~ lorenz contraction by a factor of 7]
Visible light would shift to UV, and UV would shift to X-Ray.

About 500 photons of the cosmic background radiation occupy each cubic centimetre.
You would need to travel at about 0.99999999995 light speed in order to shift these photons up to a frequency high enough to give you a sun tan.
There would be about 10^5 more photons in each centimetre cubed, because space would contract relative to your ship.
And since you're traveling at light speed 3*10^10 of those parcels hit each square centimetre of your ship each second.

Hence the flux of UV would be about 3*10^10 * 10^5 per square centimetre

UV has about 4eV of energy per photon, or 4*1.6*10^-19J so

3*10^10 *10^5 *10^4 *4*1.6*10^-19 = 19.2watts per square meter, which is about 6 times lower than the amount you need to be sunburnt [120 watts per square meter]

Hence, if you flew through space at 0.99999999995 and there was only microwave background radiation in your way, you wouldn't even be able to get a sunburn.

So I doubt that you could cook a craft by flying it at relativistic speeds.
 
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Sylox

boi...chill out!
a few years back I heard on a pop-science show even spaceflight at relativistic speeds is, uh, non-trivial, as you're not only cooked by star light turned into high-energy UV radiation by the Doppler effect (or was it Lorentz contraction..?) but also that your ship's mass increases the closer you get to lightspeed and it collapses into itself once you cross the threshold.

I've never heard of a ship collapsing in on itself once it were to cross the threshold, but I guess its possible considering the infinite mass you'd be taking on. Yes, the radiation that one will receive from stars will be lethal so any ship wishing to travel at such a speed needs to have some kind of shield which will protect the inhabitants from that. IMO though, the biggest thing to worry about is micro meteorites, which would literally blow a ship apart if it were to strike it while it was traveling at such a high speed.

BTW, pop science shows aren't the best places to get information. Often times the concepts are "dumbed down" so the audience can understand a bit better. That doesn't mean they can't be informative and many of them are its just that a good portion of them implant misconceptions, most notably that the Universe came into existence via an explosion (my biggest pet peeve). If you're interested in learning more about our universe, travel down to you local library and read up on all of the books there that focus on it. I highly recommend A Brief History of Time by Stephen Hawking.
 

Gryphoneer

20 Quatloos on "disruptive"
It was a physicist with the DLR (our space agency) doing a program on Einstein's work at his birthday, and the relativistic spacecraft came up as thought experiment. It wasn't Shark Week level, is what I'm saying. Doesn't rule out the possibility I just misremember or they were wrong; even experts can be, especially if we talk about things that have yet to be build.
 

Fallowfox

Are we moomin, or are we dancer?
I've never heard of a ship collapsing in on itself once it were to cross the threshold, but I guess its possible considering the infinite mass you'd be taking on. Yes, the radiation that one will receive from stars will be lethal so any ship wishing to travel at such a speed needs to have some kind of shield which will protect the inhabitants from that. IMO though, the biggest thing to worry about is micro meteorites, which would literally blow a ship apart if it were to strike it while it was traveling at such a high speed.

BTW, pop science shows aren't the best places to get information. Often times the concepts are "dumbed down" so the audience can understand a bit better. That doesn't mean they can't be informative and many of them are its just that a good portion of them implant misconceptions, most notably that the Universe came into existence via an explosion (my biggest pet peeve). If you're interested in learning more about our universe, travel down to you local library and read up on all of the books there that focus on it. I highly recommend A Brief History of Time by Stephen Hawking.

The mass of the ship would appear to increase from the perspective of a bystander in an inertial reference frame. From the spaceship's perspective, the spaceship's mass does not change.

I agree that little bits of dust in space represent the biggest danger, because they would have an immense energy from the spaceship's perspective.
A lot of those dust particles have charged surfaces though, because of unsatisfied bonds at their surfaces, so I think that a great big magnetic field could deflect them out of the spaceship's way, before they caused a collision.

I was wondering whether merely traveling at high speed through the interstellar medium would be sufficient to generate a great big field, because there are a lot of unbound hydrogen atoms floating around in space, and because they are electrically charged moving them around as they bump off of your space craft will produce a magnetic field.
So the very act of traveling at relativistic speed could be enough to make a slip-stream that guides small pieces of charged dust out of the way of your space craft?

Sort of like a head-shield on a ballistic missile. The flattened nose of the missile pushes the air out of the way, and sets up a flow around the missile, which means that the shocked air, which is incredibly hot, does not touch the missile itself. If the air did touch the missile, it would be so energetic that the missile would be ignited.

inset_HeatShieldSeals_A.jpg


Here's an artist's impression of an ablative heat shield working. The very hot air, which turns into a glowing plasma, is guided around the craft, so that it doesn't destroy it.
 
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Rassah

Well-Known Member
Closest you're going to get to a relativistic spacecraft is a Bussard ramjet

Ah, thanks! I remember those from Microsoft Space Simulator, but did not know what they were called, so couldn't look it up. I kinda wonder if it's possible to accelerate a ship, even if just within our solar system, using a fixed point high energy laser (such as from a satellite floating in space, aimed at an accelerating spacecraft). That way the ship wouldn't have to carry its own energy source. Although propulsion needs an "opposite reaction" involving matter, so it may not be possible, and I doubt using a solar sail with a laser would give you much acceleration. I love the Orion project idea btw. Especially that Coca Cola was tasked with designing a giant "vending machine" that would dispense small nukes out the back of the ship :D Maybe we can still figure out how to make something like that using hydrogen bombs/explosions only. Current hydrogen bombs are ignited by first using regular chemical explosives to set off a dirty plutonium fission nuke, which sets off a clean hydrogen fusion nuke (first creates radioactive dust fallout, second creates helium). If we could set off a hydrogen fusion bomb directly, it would create radiation that won't last, and would be "clean."

Though it still seems our best bet for traveling at the speed of light is to transfer ourselves AS light. Minds as information on radio waves seems like a possibility in this century even, though it would require a receiver where this information can be processed. I wonder how far we are from converting energy back into matter? (we can go matter to energy now, but not the other way).

Fallow, ask your brother about what happens if a micro meteorite or a dust particle is fired at an object at near light speeds.
 
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Rassah

Well-Known Member

Rassah

Well-Known Member
Even without crunching numbers I believe the answer can be correctly summed up as BAM


That's the question. It is BAM, *F*i*z*z*l*e*, or swip...? (impact explosion, nuclear explosion/irradiation, or pass through with little notice by most of the matter)
 

LazerMaster5

Lost in the Static
FTL travel could cause many issues, like a breach in the hull or an unexpected obstruction in the flight path. Boom, everyone's dead. Like driving a supercar at high speeds without brakes. Most Interstellar travel in Sci-fi not only defies physics, but bends space and time itself. How about creating and manipulating wormholes that allow ships to jump large distances in short time without requiring FTL technology? Yeah, the rules of space and time would be told to fuck off, but the jumps could possibly be safer and more efficient than straight up FTL travel.
 
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