X Minus Zero


Sixty years ago today

“T minus one minute and counting.”   The term “T minus” seems as old as the space age.  But there was a time, sixty years ago, when the call was “X minus.”

That was the call this day, January 31, 1958, as the count drained towards zero for the launch of Explorer I atop an Army Jupiter-C missile.  After two days of delays due to high upper-atmospheric winds, this was the last crack at launching Explorer at the first U.S. satellite, an orbital feat the Soviet Union had achieved nearly four months before.  If the launch didn’t go, the Army would have to turn Cape Canaveral launch range over to the Navy and the rival Vanguard satellite program that had failed in December.

Upper level winds held within acceptable levels as the evening X time approached.  The tiny cylindrical Explorer satellite, itself 33 inches long and weighing 14 lbs., would stay attached to the solid-fueled Sargent upper stage, the combination in orbit weighing 30.8 lbs.

X minus 90 seconds.  Clear to launch.

X minus zero.  “Firing command.”

Valves open, propellant tanks pressurize.

X plus 14 seconds.  Ignition.

Ignition, followed 1.75 seconds later by liftoff at 10:47:56 p.m. EST.  The Jupiter C made a perfect climb, one which would take 6 min. 56 sec. to achieve orbit.  That is, if it achieved orbit.  That fact would only be confirmed if its signal was received over California nearly two hours after launch, after midnight, February 1, on the East Coast.   Where they waited for word.

These days, the end of January is remembered for space disasters — Apollo 1 on January 27, 1967; Challenger on January 28, 1986; Columbia on February 1, 2003.

But sixty years ago, this date marked success.  “California tracking “has acquired the bird.”




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