I’m pretty sure it is possible to escape Earth’s light cone at sublight speeds. You can go arbitrarily far from earth (if you’re patient). Eventually, you will get to a point where your distance from Earth*the Hubble constant is greater than the speed of light (you are now a Hubble length from Earth). At this point, a photon you shoot straight towards Earth will not approach Earth, because the distance in between is expanding at the speed of light.
I’m pretty sure it is possible to escape Earth’s light cone at sublight speeds. You can go arbitrarily far from earth (if you’re patient). Eventually, you will get to a point where your distance from Earth*the Hubble constant is greater than the speed of light (you are now a Hubble length from Earth). At this point, a photon you shoot straight towards Earth will not approach Earth, because the distance in between is expanding at the speed of light.