M ▁and ▁SL B M ▁S 2 . 2 5 3 ▁( 8 D 5 1 1 ): ▁A ▁k eros ene / AK 2 0 ▁burning ▁engine ▁in ▁the ▁pressure ▁fed ▁cycle . ▁Development ▁years : ▁ 1 9 5 1 - 1 9 5 5 ▁. ▁For ▁use ▁in ▁first ▁versions ▁of ▁Sc ud - A . ▁Ign ition ▁by ▁hyper g ol ic ▁start ▁fuel ▁T G - 0 2 . ▁S 2 . 2 5 3 A : ▁A ▁k eros ene / AK - 2 0 ▁ ▁burning ▁engine ▁in ▁the ▁pressure ▁fed ▁cycle . ▁Development ▁years : ▁ 1 9 5 3 - 1 9 5 9 ▁. ▁For ▁use ▁in ▁the ▁R SM - 1 1 FM . ▁Ign ition ▁by ▁hyper g ol ic ▁start ▁fuel ▁T G - 0 2 . ▁S 2 . 7 1 3 : ▁A ▁T G - 0 2 / AK 2 7 I ▁burning ▁engine ▁in ▁the ▁gas ▁generator ▁cycle . ▁Development ▁years : ▁ 1 9 5 6 - 1 9 6 1 ▁. ▁For ▁use ▁in ▁the ▁R - 1 3 . ▁It ▁included ▁a ▁fixed ▁no zz le ▁and ▁four ▁vern iers . ▁S 5 . 2 ▁( 9 D 2 1 ): ▁A ▁T M - 1 8 5 / AK - 2 7 I ▁ ▁burning ▁engine ▁in ▁the ▁gas ▁generator ▁cycle . ▁Development ▁years : ▁ 1 9 5 9 - 1 9 6 2 ▁. ▁For ▁use ▁in ▁the ▁R -