Lets assume we have a starship which is flying from Earth to star XY which is in distance for example 100 lightyears. The computer of that ship is programmed that way, that it maintains acceleration 1 g. After some time the speed of ship reaches some significant part of speed of light and to maintain the acceleration, the engins must burn more and more fuel to maintain 1 g. But there is also the effect of time dilation, contraction and increase of mass. Lets say the ship reaches 87%of speed of light, which would mean that there are some significant relativistic effects for example the relativistic mass would double compared to original rest mass of the ship. Now Im getting to the question: Would the astronaut inside the ship feel that he weights 160 kilograms when his original weight was 80 kilograms? What I know, the accepted consensus is that he would not feel the increase of weight, because he is in his own reference frame inside the ship. But is this view hardwired in quotations of SR and GR or is this just a philosophical point of view which was never confirmed by any experiment?