Main engine of Rosatom-Antonov K37-TNTRL can produce up to 750kN of thrust. This is way more than required within the Ring, yet it allows fully loaded K37 to accelerate near comfortable 1G – allowing reaching Earth in 4 to 9 days, depending on orbital position.
Layout of the crew cabin allows earth-like gravity experience on entire trip, excluding brief midpoint thrust reversal. With full fuel tank Rosatom-Antonov can maintain continuous full thrust for period of 9 days total. Exhausted gas doubles up as cooling system, carrying excessive heat outside the vessel body. Main reactor also supplies electrical power to the whole system by hybrid turbine and supplementary TEG system.