ar ▁module , ▁and ▁thus ▁had ▁no ▁prov isions ▁for ▁dock ing ▁with ▁another ▁space craft . ▁This , ▁plus ▁other ▁required ▁design ▁changes , ▁led ▁to ▁the ▁decision ▁to ▁design ▁two ▁versions ▁of ▁the ▁C SM : ▁Block ▁I ▁was ▁to ▁be ▁used ▁for ▁un cre wed ▁miss ions ▁and ▁a ▁single ▁cre wed ▁Earth ▁orbit ▁flight ▁( A pol lo ▁ 1 ), ▁while ▁the ▁more ▁advanced ▁Block ▁II ▁was ▁designed ▁for ▁use ▁with ▁the ▁lun ar ▁module . ▁The ▁Apol lo ▁ 1 ▁flight ▁was ▁cancel led ▁after ▁a ▁cabin ▁fire ▁killed ▁the ▁crew ▁and ▁destroyed ▁their ▁command ▁module ▁during ▁a ▁launch ▁re he ars al ▁test . ▁Cor re ctions ▁of ▁the ▁problems ▁which ▁caused ▁the ▁fire ▁were ▁applied ▁to ▁the ▁Block ▁II ▁space craft , ▁which ▁was ▁used ▁for ▁all ▁cre wed ▁space fl ights . ▁ ▁Nin ete en ▁C SM s ▁were ▁launched ▁into ▁space . ▁Of ▁these , ▁nine ▁fle w ▁humans ▁to ▁the ▁Moon ▁between ▁ 1 9 6 8 ▁and ▁ 1 9 7 2 , ▁and ▁another ▁two ▁performed ▁cre wed ▁test ▁fl ights ▁in ▁low ▁Earth ▁orbit , ▁all ▁as ▁part ▁of ▁the ▁Apol lo ▁program . ▁Before ▁these , ▁another ▁four ▁C SM s ▁had ▁flow n ▁as ▁un cre wed ▁Apol lo ▁tests , ▁of ▁which ▁two ▁were ▁sub orb ital ▁fl ights ▁and ▁another ▁two ▁were ▁orb ital ▁fl ights . ▁Following ▁the ▁conclusion ▁of ▁the ▁Apol lo ▁program ▁and ▁during ▁ 1 9 7 3 – 1