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Zero and lift off the delta rocket with Mars Pathfinder
and the vehicle has cleared the tower.
It wasn't always this easy.
The Delta II has become a workhorse of NASA's Launch Services Program.
Thanks to a history of reliability and efficiency,
it has proven itself dozens of times.
Delta began as an improved version of the Thor,
and recorded its first successful mission August 12, 1960.
The payload then was the Echo I communications satellite,
which weighed about the same as an average adult male.
A gradual list of improvements gave the Delta I models better engines
and bigger fuel tanks.
With each change came a greater load the rocket could place into orbit.
That meant launching communications satellites that were more capable of
transmitting signals around the world, and a chance to launch probes
to nearby planets.
It didn't take long before engineers started attaching small booster rockets
to the side of the first stage to give an extra kick at liftoff.
It's a practice we still use today, although the booster rockets are considerably
stronger and somewhat larger than those early models.
By 1975, the Delta rocket could shoot a ton of cargo into high earth orbit.
That was about 11 times more than the first Delta could carry.
Delta production was temporarily halted when the space shuttle program began
in the early 1980s.
Manufacturing returned after 1986 as part of NASA’s mixed fleet manifest
and the changes began again.
Improved several times in recent years, the Delta II is still a reliable element
in NASA's launch fleet.
The rocket regularly dispatches planetary probes, GPS satellites
and groundbreaking missions that have proven new technologies.