During a remarkable congressional hearing, former American intelligence official David Grusch revealed that the US government conducted a "multi-decade" programme aimed at collecting and reverse-engineering crashed unidentified flying objects (UFOs).
Grusch, who was in charge of investigating unexplained anomalous phenomena within a US Department of Defence agency until 2023, spoke before the House oversight committee in Washington, shedding light on the issue of alien life and technology, as reported by the Guardian.
Those effects only occur from the perspective of, for example, Earth. If you could exert force upon a space ship traveling away from you, it would require more energy to continue to accelerate it as its speed increases relative to you. But from the reference frame of the ship, this does not hold. Now, of course it will still require an insane amount of energy to maintain a constant acceleration, but from the spaceship’s perspective energy expenditure is constant (assuming the mass of the ship isn’t changing due to fuel loss).
If I remember it correctly from the point of view of the ship it looks like the propulsion becomes less effective, tough I confess my recolection of what I learned about the General Theory Of Relativity in my Physics degree almost 3 decades ago (which I never completed, by the way, so I’m an EE not a Physicist) breaks at around this point so I might be completelly off on this.