This article examines, special case of the law for conservation the motion of the center of the mass of а closed inertial system - device from two bodies (two hulls). Like in this special case, we obtain uncompensated moment for one of the hull of the device. As conditionally named first hull is standard rigid body. While on the second hull are connected two discs, which have equal masses and they can rotate free to the second hull. As when we apply the third law of Newton, between the two hulls, it’s uses the inertial of the two discusses. Like this way, because the kinetic energy is additive magnitude, it’s the hull with the discusses distribute the itself energy and for rotary motion of the discusses and for translational motion of the second hull. While for the first hull total kinetic energy, as a result of the applied third law is in the form of translational motion. As a result of the distribute of the energy of the second hull we obtain uncompensated moment for first hull. As a result of which is obtains and the special case of the law conservation motion of center of the mass of closed system — device from two bodies (two hulls). Like this way we have possibility for specific propulsion without propellant of the device in the cosmic space. Despite some shortcomings of the resulting specific propulsion, this is one of the possible ways of propulsion in cosmic space without "ejection" of propellant, and as only uses electrical energy from photovoltaics or nuclear energy.