▁NASA ' s ▁first ▁space ▁pro be ▁intended ▁to ▁reach ▁the ▁Moon . ▁A ▁partial ▁failure ▁caused ▁it ▁to ▁instead ▁follow ▁a ▁sub orb ital ▁traject ory ▁to ▁an ▁alt itude ▁of ▁ ▁before ▁re ent ering ▁the ▁Earth ' s ▁atmosphere ▁ 4 3 ▁hours ▁after ▁launch . ▁ ▁The ▁most ▁generally ▁recognized ▁boundary ▁of ▁space ▁is ▁the ▁K á rm án ▁line ▁ 1 0 0   km ▁above ▁sea ▁level . ▁( N AS A ▁altern atively ▁defines ▁an ▁astr onaut ▁as ▁someone ▁who ▁has ▁flow n ▁more ▁than ▁ ▁above ▁sea ▁level .) ▁It ▁is ▁not ▁generally ▁recognized ▁by ▁the ▁public ▁that ▁the ▁increase ▁in ▁potential ▁energy ▁required ▁to ▁pass ▁the ▁K á rm án ▁line ▁is ▁only ▁about ▁ 3 % ▁of ▁the ▁orb ital ▁energy ▁( pot ential ▁plus ▁kin etic ▁energy ) ▁required ▁by ▁the ▁lowest ▁possible ▁Earth ▁orbit ▁( a ▁circular ▁orbit ▁just ▁above ▁the ▁K á rm án ▁line .) ▁In ▁other ▁words , ▁it ▁is ▁far ▁easier ▁to ▁reach ▁space ▁than ▁to ▁stay ▁there . ▁On ▁May ▁ 1 7 , ▁ 2 0 0 4 , ▁Civil ian ▁Space ▁e X pl oration ▁Team ▁launched ▁the ▁Go F ast ▁Ro cket ▁on ▁a ▁sub orb ital ▁flight , ▁the ▁first ▁amateur ▁space fl ight . ▁On ▁June ▁ 2 1 , ▁ 2 0 0 4 , ▁Space Sh ip One ▁was ▁used ▁for ▁the ▁first ▁priv ately ▁fund ed ▁human ▁space fl ight . ▁ ▁Point - to - point ▁