Tsiolkovsky says otherwise, by a factor of over 10^663 (not even counting relativity):
https://www.wolframalpha.com/input?i=1%2Fe%5E%2874900km%2Fs%...
…Seriously. I tried to figure out just how much xenon you'd need to make that work. But you'd need to be able to store it in something like 15-dimensional space to even fit it within the diameter of the observable universe. And even if your ion engine and Hubble-scale fuel tank weighed less than the mass of the lightest quarks, the amount of propellant you'd need for it to reach 0.25c is still well over 10^600 times the combined mass of the entire observable universe, and would also collapse somewhere around 10^600 times the diameter of the observable universe into a single black hole:
https://www.wolframalpha.com/input?i=2G%282.2MeV%2Fc%C2%B2%2...
Of course, this also shows the intent of my original comment: Energy density matters, and somebody packing enough to casually cross interstellar densities isn't going to struggle with a planetary gravity well unless Idk they're doing like a low-tech off-grid trend or something.
Also, skyhooks!
