To increase the efficiency of KSC and promote the mini size laythe travelling crafts, we decide to develop an engine replace unit. By replace R.A.P.I.E.R. Engine with LV-N Atomic Rocket Motor on orbit, we could highly increase the endurance of mini size SSTO and Space Plane. This is our test plane, mini size space plane, full capability of LKO travel. But to fly to laythe, even with refuel, it is impossible. 1st, docking; 2nd, engine picker pick R.A.P.I.E.R. Engine and dock it on the engine holder; 3rd, engine picker pick LV-N and mount it on the craft. 4th, engine picker return to position, craft is ready to go. With LV-N engine and refuel, this mini-size plane has a ÃŽâ€V more than 2600m/s, full capability of laythe travel. Further development for airfoil replacement will coming soon.