Luna Ye-8 series, 1969-1976
The Ye-8 series were much heavier and more complex, and were launched on the powerful new Proton rocket. The design centered on four large spherical propellant
Figure 5.2 Luna 17 Yc-8 lander with Lunokhod I aboard.
Figure 5.3 Luna 19 Ye-8LS orbiler in flight configuration including external drop tanks (courtesy NrO-Lavochkin).
tanks connected in a square using cylindrical inter-tank sections. The landing system and engine were mounted on the underside of this assembly and the lander payload on the upper side.
The principal goals of these spacecraft were first to deploy a lunar rover on the surface (the Ye-8 model) and second to return samples of the lunar surface to Earth (the Ye-8-5 model). Three Ye-8 lunar lander rover spacecraft were launched, two of which, Luna 17 and Luna 21. were successful. Of a total of eleven Ye-8-5 sample return spacecraft launched, only three were successful, Luna 16, 20 and 24. In fact, Luna 20 and 24 were advanced Yc-8-5M models. Two additional Ye-8 models were modified as Yc-8LS lunar orbiters and both flown successfully as Luna 19 and 22. The overall record for the Yc-8 was therefore seven successes of sixteen attempts.