This takes you to 0.99C, how feasible is that (thinking materials more than anything)
At speeds about 0.5C a collision with such an atom produces X-rays, and harder gamma rays at higher speeds. They are pretty hard to insulate against, and are actively harmful. For a spaceship of a considerable size, enough collisions would occur to be dangerous. The paper: https://www.scirp.org/journal/PaperInformation.aspx?paperID=...
And then there's the problem of hitting an interstellar grain of sand at 0.5c.
Speculating you'll substantially blue shift the light coming from in front of you, and I suppose that can't be good for materials (or people), but I'm not sure if there is enough to matter. Any dust you collide with is also going to have ridiculous amounts of energy, but you'll be in interstellar space when you're at high speeds so there shouldn't be much of it (even for space) either.
https://www.quora.com/How-much-energy-does-it-take-to-accele...
I don't think that means is unfeasible if the energy source allows for that.
The rocket equation says that the fuel mass of a rocketship is higher than the cargo mass by exp(delta_v/v_exhaust).
When the final velocity is relativistic, delta_v should be replaced with delta_rapidity. In our case this would introduce a factor of 2.65, but the results are so ridiculous that we can ignore that.
So, let's simply say that delta_v is the speed of light, or 300000 km/s.
The exhaust velocity for a nuclear thermal rocket is about 9 km/s.
The ratio between delta_v and the exhaust velocity is about 33000. The exponential of that is roughly speaking 1 followed by 15000 zeros.
There are less than 10^100 atoms in the known universe.
So, even if you want to accelerate just one single atom to 99% of the speed of light, you would need more fuel than the entire universe. Many, many, many times more.
The laws of physics don't change in different frames (Einstein's assumption), but that doesn't mean that all frames are equivalent in other respects.
What does this mean? The CMB is radiation travelling at the speed of light in every direction.
https://www.reddit.com/r/AskPhysics/comments/2va4t6/does_no_...
> You are absolutely right in that the CMB becomes Doppler shifted when you have some relative velocity. But Earth is not in the CMB rest frame: when we observe the CMB from Earth, we observe a dipole component to the CMB caused by the Earth's motion orbiting the Sun, the Sun's orbit around the Milky Way, and any velocity the Milky Way as a whole has. I was at a talk about the new Planck results last week, and saw a plot in which you can clearly see the dipole component in the raw data. You need to correct for this motion before you can even remotely see the anisotropies that are the interesting science goals of Planck.
> There is a rest frame in which the CMB is closest to isotropic (no dipole component), and this rest frame is special but not 'absolute'. This frame is effectively the 'center-of-momentum' frame of the observable universe, in which we expect the total momentum to be zero. We know from classical mechanics that for any system of objects, we can construct such a frame, and that it sometimes has useful properties for solving certain types of problems. But there is nothing 'absolute' about this rest frame, the laws of physics operate entirely the same.
> And so this is fine, because ultimately what relativity requires is that the laws of physics operate the same in every rest frame, not that every rest frame looks the same. Because the CMB is itself physical (made of photons) and was emitted by matter, it is entirely natural that it should be affected by frame transformations, and should look different if you shift to a frame that is moving differently than the emitting medium.