Thomas Joseph O'Malley (October 15, 1915 – November 6, 2009) was an Irish-American aerospace engineer who, as chief test conductor for the Convair division of General Dynamics, was responsible for pushing the button on February 20, 1962, launching the Mercury-Atlas 6 space flight carrying astronaut John Glenn, the first American in orbit.

[3] In 1961, the Atlas was the only rocket in the United States' inventory with sufficient thrust to launch a crewed Mercury space capsule into orbit,[5] and Convair was contracted to adapt it for this purpose.

[5] On the morning of February 20, 1962, O'Malley was directing the General Dynamics launch team from the windowless blockhouse just a few hundred yards from Pad 14 at Cape Canaveral where John Glenn sat atop the Atlas rocket in Friendship 7.

O'Malley methodically worked through the checklist, finally announcing over the intercom, "T-minus 18 seconds and counting, engine start", as he pressed the black button on his console that began the firing sequence of the Atlas rocket.

[6] In response, his boss, astronautics base manager Byron MacNabb, seated in Mercury Control, said, "May the wee ones be with you, Thomas", a good luck reference to the leprechauns of Irish mythology.

[5] On January 27, 1967, the Apollo 1 command module fire at Launch Complex 34 killed astronauts Gus Grissom, Ed White and Roger B. Chaffee.