After launch from the earth, the 85 000-kg spaceshuttle orbiter is in the elliptical orb...

After launch from the earth, the 85 000-kg spaceshuttle orbiter is in the elliptical orbit shown. If the orbit is to be circularized at the apogee altitude of 320 km, determine the necessary time duration Δt during which its two orbital-maneuveringsystem (OMS) engines, each of which has a thrust of 30 kN, must be fired when the apogee position C is reached.