Accelerating to the speed of light

[Mmmmyum]

So last night I was lying in bed (mostly trying to not think of the chemistry paper I was going to fail today) and a thought struck me. So if you want to go to a star 200 million light years away, and you could get past the speed of light, how would you go about accelerating to that speed? I'm gonna reckon that for a long (order of months, maybe years) burn, 2Gs would be the maximum limit normally.

However that still means you can only accelerate at 19.62m/s^s. And that's accelerating to way past 299 792 458m/s (quite a few orders of magnitude). Now if we wanted to get to that place within, lets say, a year (FTL travel being possible) how would we deal with the g-forces that are going to want to plaster us into a pinkish smear on the rear wall of the cockpit?

I thought of a system that converts the velocity into angular momentum for the crew compartment leaving the crew compartment spinning at a very fast speed (which would slow down over the course of the journey), having brakes of some sort to slow down the angular acceleration.

Edited November 22, 2013 by Mmmmyum

[Chrisd857]

Well, the real problem is that, when relativistic effects become significant, your increasing mass, decreasing ship length, and dilating time will prevent you from reaching light speed (since your mass will be infinite and the ship will have zero-length). Faster than light, imaginary numbers start popping up all over the place.

So, you need some trickery like the theorectical Alcubierre drive to manage this.

[kahlzun]

If you've got access to an energy source that allows you to maintain that acceleration, then you've probably got the technology to diminish G-forces.

Keep in mind an engine can only accelerate something to the speed of its exhaust (give or take), so to get to lightspeed, you need to be firing out light-speed particles.

If you were trying to get to something 200M LY away, the months or years it takes you to accelerate to C would be trivial compared to total flight time.

[ZetaX]

Keep in mind an engine can only accelerate something to the speed of its exhaust (give or take), so to get to lightspeed, you need to be firing out light-speed particles.

No, just no! Don't think that rocket engine exhaust travels at orbital velocity or higher, because it doesn't, and it doesn't need to. You get faster by Newton's laws if you eject some mass with any speed backwards, however miniscule. More speed of the ejected mass just means you accelerate more at once, i.e. you are more efficient in regard to mass spent as exhaust (-> specific impulse).

Light speed being impossible to achieve for anything of positive mass is a purely relativistic problem and has othing to do with such matters of Newtonian physics.

[Mmmmyum]

I looked up how long it would take to accelerate to c at 1G, and that's just over a year ignoring the annoyances of relativity. I'm mostly just wondering about a way to dampen massive g forces with somewhat current day tech (ignoring, again, relativistic effects)

[Starwhip]

You see, you guys keep saying NEWTONIAN physics. Not everything obeys these laws. Go on google and look up "superconductor", find the Ted talk on it. Here's some quick facts about them:

They have ZERO electrical resistance.

They can lock themselves in 3-DIMENSIONAL SPACE around a magnetic field.

They can carry over 70,000 times their weight.

They, most importantly, have ZERO ENERGY LOSS.

We are dealing with QUANTUM physics here, not Newtonian. With more research in this field we could find a way to make a FTL spacecraft.

[Neil1993]

I don't think there is any current-day tech that can mess with physics like that. However, a craft using the warp drive proposed by Miguel Alcubierre would not feel any acceleration, because it is not (technically) accelerating.

If you're interested in learning more on this, you can consult his original paper: http://iopscience.iop.org/0264-9381/11/5/001

[K^2]

We are dealing with QUANTUM physics here, not Newtonian. With more research in this field we could find a way to make a FTL spacecraft.

We already have relativistic quantum physics. It still says that speed of light is the local limit. Without warping space-time, there is no way to travel FTL. Warp drive and wormholes are the only known ways around it.

In terms of normal space-travel, however, there is something called proper velocity. It's the map distance covered in unit proper time. From perspective of the crew of the ship, that's the true velocity. And that can go as fast as you like. Better yet, once you are going fast enough, it becomes easier to speed up. At proper acceleration of 1G, it's possible to make a round trip to Andromeda in a little over 50 years of ship time. So speed of light isn't that big of a problem for crew of the ship. On Earth, however, millions of years will pass, which might be a problem depending on what the goals of the voyage are.

[Jim DiGriz]

You see, you guys keep saying NEWTONIAN physics. Not everything obeys these laws. Go on google and look up "superconductor", find the Ted talk on it. Here's some quick facts about them:

They have ZERO electrical resistance.

They can lock themselves in 3-DIMENSIONAL SPACE around a magnetic field.

They can carry over 70,000 times their weight.

They, most importantly, have ZERO ENERGY LOSS.

We are dealing with QUANTUM physics here, not Newtonian. With more research in this field we could find a way to make a FTL spacecraft.

Special Relativity is very deeply 'baked in' to QM. So QM doesn't get you out of SR, it actually requires it. If it weren't that way, we'd be accelerating protons to FTL in the LHC.

[Psycix]

If your spaceship is very heavy and very dense, it will have gravity. (It could just be as big as a moon or planet, but you'd need less mass if it was denser, like a neutron star or black hole)

The crew habs would position themselves behind this mass and be pulled by its gravity, while the mass is accelerating away from the crew at the same rate it attracts them.

The crew would be weightless, yet accelerating because they are falling towards the ship while the ship moves away.

As an added bonus, gravity slows down time, making your trip seem shorter.

Edited November 22, 2013 by Psycix

[ZetaX]

You see, you guys keep saying NEWTONIAN physics. Not everything obeys these laws. Go on google and look up "superconductor", find the Ted talk on it. Here's some quick facts about them:

They have ZERO electrical resistance.

They can lock themselves in 3-DIMENSIONAL SPACE around a magnetic field.

They can carry over 70,000 times their weight.

They, most importantly, have ZERO ENERGY LOSS.

We are dealing with QUANTUM physics here, not Newtonian. With more research in this field we could find a way to make a FTL spacecraft.

Adding in to what the others said:

a) Superconductors are perfectly viable in a Newtonian universe (matter not being infinitely reducible is what causes friction and similiarily electrical resistance).

You imply that several persons that (judging from what they post) have a very good grasp of actual physics don't know what they are talking about.

c) You seem to imply you do, or at least do to a higher degree than those mentioned in .

Please, learn some actuall physics instead, which is not the same as reading some popular science book.

[WestAir]

If your spaceship is very heavy and very dense, it will have gravity. (It could just be as big as a moon or planet, but you'd need less mass if it was denser, like a neutron star or black hole)

The crew habs would position themselves behind this mass and be pulled by its gravity, while the mass is accelerating away from the crew at the same rate it attracts them.

The crew would be weightless, yet accelerating because they are falling towards the ship while the ship moves away.

As an added bonus, gravity slows down time, making your trip seem shorter.

Wouldn't this require exactly as much Dv or energy as it would to constantly levitate the crew via a permanently firing rocket engine? Like if you held a Satellite above Earth at 0 km/s velocity by just blasting the thrusters directly at Kerbins CoM to maintain your altitude. Sounds like a waste of fuel and energy.

[K^2]

Wouldn't this require exactly as much Dv or energy as it would to constantly levitate the crew via a permanently firing rocket engine? Like if you held a Satellite above Earth at 0 km/s velocity by just blasting the thrusters directly at Kerbins CoM to maintain your altitude. Sounds like a waste of fuel and energy.

The point isn't just to accelerate the crew, but to accelerate the crew without killing everyone with over-G. Gravity would do the trick, indeed. But yeah, it would be extremely wasteful for many reasons.

a) Superconductors are perfectly viable in a Newtonian universe (matter not being infinitely reducible is what causes friction and similiarily electrical resistance).

No. In fact, electric resistance is also a purely quantum effect.

[ZetaX]

K^2: isn't that exactly what I said, namely that an ideal Newtonian universe is not having any¿

[Mmmmyum]

Psycix had a very good idea actually, again that's mostly within the realm of current tech (hey who's got a few quintillion dollars lying around?) and doesn't the Alcubierre drive heat everything up in it's bubble of space to the point that anything is impractical? (theoretically speaking of course).

Honestly sometimes I feel sad because nothing truly in the realm of science fiction will come in the 80 or so years I've got left

[ZetaX]

I find the current stand of technology rather SciFi-ic from a perspective of 80 years ago. We have nukes, computers, pretty huge planes, can send stuff throughout the solar system, ...