Gordo (monkey)

Background

Gordo was a South American squirrel monkey, about one foot tall and weighing between 1 and 1.5 kg. The species was selected for space travel because of its similar anatomical and physiological makeup to humans, sensitivity to temperature changes, small size, ease of handling, and ability to tolerate high gravitational forces. He was trained by the U.S. Navy through a structured acclimation process that included mock capsules simulating g-forces, vibration, and confinement, allowing physiological data collection without sedatives. His calm demeanor during conditioning earned him the nickname 'Old Reliable.'

The flight took place at 0353 hours EST on December 13, 1958, from Cape Canaveral. Gordo wore a leather-lined plastic helmet and specially customized space suit, strapped to a contoured rubber bed in a tapered capsule behind the nose-cone. He was fitted with instruments including a thermometer, microphone, and cardiogram. The rocket reached a height of 310 miles and traveled 1,500 lateral miles.

During the 15-minute flight, Gordo was weightless for 8.3 minutes, experiencing 10g during takeoff and 40g upon reentry. Scientists noted his breathing slowed after takeoff and his pulse became slightly irregular, but both returned to normal during weightlessness. Aside from a slight slowing of the pulse, he suffered no ill effects from entry into space or weightlessness.

A technical malfunction prevented the capsule's parachute from opening. After six hours of recovery efforts by the U.S. Army, neither Gordo's body nor the vessel were ever recovered. The Pentagon stated there were no significant adverse physical effects during weightlessness or fall to Earth, and it is believed he was alive at the time of impact.

The Jupiter AM-13 Mission

On December 13, 1958, a small squirrel monkey known as Gordo was placed aboard the Jupiter AM-13 rocket, a vehicle operated by the United States Army. This mission represented one of the more ambitious primate flights of the era, sending its passenger on a trajectory that carried it more than 2,400 kilometers (approximately 1,500 miles) through the upper atmosphere. The rocket reached an altitude of roughly 500 kilometers (310 miles), placing Gordo well beyond the 100-kilometer Kármán line that internationally marks the boundary of space.

The flight was part of a broader American effort to understand how living organisms could endure the physical stresses of rocketry and re-entry, knowledge that would eventually support crewed spaceflight in the 1960s. Gordo's journey thus placed him among the small group of non-human primates who experienced the full arc of a long-duration rocket trajectory before any human astronaut ever did, and his survival of the launch and flight phase marked a genuine milestone in the program's progression.

Did You Know?

• Gordo was not the first U.S. monkey in space; that distinction belongs to Albert II.
• The rocket used was a Jupiter missile, not a PGM-19 Jupiter rocket.