Can we simulate Earth's gravity in space?

Simulating gravity in space basically means simulating weight, which requires acceleration. So basically, the question is, how do we create acceleration in space.

The easiest method for simulating gravity in space is by spinning the space station. In this case, the reaction force to centripetal force substitutes the force of gravity, which pushes the inner contents to be pushed against the outer edge, giving a sensation of weight. This method is theoretically sound and can be used to simulate gravity.

The problem with doing this in ISS boils down to two things- size and shape.

The best shape for a space station having a simulated gravity is something like a doughnut spinning about its axis, so that the occupants are pushed against the outer wall. The shape of ISS is nowhere near this.

If one excludes the solar panels and the truss structure, the ISS is around 45m along the axis of the habitable modules, if we spin along the axis of the truss structure, this gives a radial distance of ~22.5m.

For simulating earth's gravity in ISS, we will require,

$omega^{2} r = g$

$omega = sqrt{frac{g}{r}}$

For g = 9.8 $ms^{-2}$,

$omega = sqrt{frac{9.8}{22.5}} = 0.66 rad/sec = 6.3 rpm$

The problem is that at this rotational speed, the head and foot of the astronomer will have different linear velocities. The head of a 1.5m tall astronaut will be moving at 13.86 $ms^{-1}$, while the foot will be moving at 14.85 $ms^{-1}$, never mind they are standing at the bottom of a barrel. This will lead to Coriolis effect, which will be uncomfortable.

So, while earth's gravity cannot be simulated in ISS due to various constraints, we can settle for reduced gravity (with reduced, ~2 rpm) in an ISS sized spacecraft.