( CNN ) -- Astronaut Scott Carpenter , the second American to orbit Earth , died Thursday , NASA said . He was 88 . `` We have lost a true pioneer . I shall long remember him not only for his smarts and courage but his incredible humor . He kept us all grounded , '' said NASA Administrator Charlie Bolden . `` We will miss him greatly . '' Carpenter was one of the original Mercury 7 astronauts chosen by NASA , which said he died from complications after a stroke . He was a backup pilot for John Glenn ahead of America 's first manned orbital space flight in February 1962 . Carpenter flew the second American manned orbital flight in May of that year . Flight time was four hours and 54 minutes , according to a NASA biography . Carpenter 's spacecraft overshot its landing target by some 250 nautical miles , giving rise to fears about his fate . With Carpenter 's death , Glenn is the lone survivor of the Mercury 7 , which included Carpenter , Glenn , L. Gordon Cooper , Virgil `` Gus '' Grissom , Walter Schirra , Alan Shepard and Donald `` Deke '' Slayton . Soviet cosmonaut Yuri Gagarin was the first person to orbit Earth in April 1961 . 'Pioneer ' of inner and outer space . Carpenter was born in Boulder , Colorado , and attended the University of Colorado , where he studied aeronautical engineering . He retired from the Navy in 1969 , after some two decades of service . Post-NASA , Carpenter explored underwater environments as an aquanaut in the Navy 's Man in the Sea Project -- at one point living and working on the ocean floor for 30 days straight . He later served as director of the Navy 's aquanaut operations . `` I still ca n't make up my mind whether I like outer or inner space better , '' Carpenter said last year -- adding with a smile , `` But there 's a difference in glory . '' Carpenter 's memoir , `` For Spacious Skies : The Uncommon Journey of a Mercury Astronaut , '' was published in 2003 . He also wrote two novels . `` He was one of the good guys and a good friend , a pioneer who made significant contributions to our country , '' said Dick Gordon , command module pilot for Apollo 12 . People we 've lost in 2013 . CNN 's John Zarrella contributed to this report .
Carpenter suffered complications after a stroke . John Glenn is the lone survivor of the Mercury Seven . `` We have lost a true pioneer , '' says NASA administrator . Carpenter was the second American to orbit Earth .