Blok D
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Blok D is an upper stage used on Soviet and later Russian expendable launch systems, including the N1, Proton-K and Zenit.
The stage has been included in more than 320 launched rockets as of 2015. Wikipedia
Diameter: 3.70 m (12.1 ft)
Empty mass: 2,140 kg (4,720 lb)
Maximum thrust: 83.61 kN (18,800 lbf)
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