▁Since ▁there ▁are ▁no ▁over fl ight ▁issues ▁and ▁the ▁facilities ▁can ▁fit ▁in ▁a ▁one - mile ▁circle , ▁they ▁can ▁be ▁located ▁far ▁in land , ▁allowing ▁many ▁in land ▁locations ▁( such ▁as ▁Ohio ▁or ▁Switzerland ▁for ▁example ) ▁to ▁run ▁their ▁own ▁launch ▁facilities . ▁ ▁R eli ability ▁The ▁R L - 6 0 ▁ro cket ▁is ▁a ▁closed - cycle ▁exp ander ▁engine , ▁and ▁is ▁a ▁scale d - up ▁version ▁of ▁the ▁R L - 1 0 , ▁one ▁of ▁the ▁most ▁reliable ▁engines ▁ever ▁built . ▁Though ▁this ▁type ▁of ▁engine ▁is ▁not ▁as ▁capable ▁of ▁generating ▁the ▁same ▁power ▁as ▁the ▁SS ME , ▁it ▁is ▁much ▁less ▁complex ▁and ▁much ▁more ▁reliable . ▁Exp ander ▁cycle ▁engines ▁do ▁not ▁need ▁computer ▁controllers ▁to ▁merely ▁function . ▁The ▁fuel ▁coming ▁out ▁of ▁the ▁engine ▁bell ▁cool ing ▁system ▁is ▁also ▁not ▁much ▁hot ter ▁than ▁room ▁temperature , ▁and ▁hence ▁does ▁not ▁cause ▁nearly ▁so ▁much ▁damage ▁as ▁pre burn ers ▁( read ▁' min i ▁ro cket ▁engines ) ▁do . ▁ ▁Current ▁material ▁technology ▁is ▁not ▁up ▁to ▁building ▁a ▁single - stage ▁vehicle ▁that ▁can ▁go ▁into ▁orbit , ▁and ▁carry ▁a ▁useful ▁payload , ▁and ▁return ▁to ▁earth ▁in ▁a ▁condition ▁to ▁launch ▁again . ▁The ▁D H - 1 ▁gets ▁around ▁this ▁problem ▁by ▁splitting ▁the ▁task ▁between ▁the ▁two ▁stages , ▁allowing ▁both ▁to ▁operate ▁safely ▁within ▁known ▁material ▁limits , ▁and ▁known ▁operating ▁methods . ▁A