This week in rocket history is once again a story from last week, but given how packed last week was, we decided to bump it to today.
On May 5, 1961, Alan Shepard entered his Mercury capsule dubbed “Freedom 7” at 5:15 am local time in Cape Canaveral or 10:15 UTC. After two hours of preparation, about an hour of waiting for the clouds to clear, and almost another hour waiting for Goddard Space Center to sort out some computer issues, the Mercury Redstone Launch Vehicle finally fired and pushed Shepard and the Freedom 7 upwards.
At T+45 seconds, the capsule and the rocket began shaking violently as Shepard went supersonic, and the shaking worsened when Shepard reached the point of maximum dynamic pressure, or Max Q, at 88 seconds. Fortunately, those vibrations went away shortly afterward.
Two minutes into the flight, Shepard reported “all systems go” while he was experiencing six Gs of force! As a quick aside: to give you some idea of how much force he experienced, if you were to ride one of those rotor rides that spin around so you stick to the wall at a carnival or amusement park, you would experience about three Gs of force. Double that, and that’s what Shepard felt during his flight.
Anyway, back to his flight. At T+142, the Redstone engines shut off, and the rocket was promptly jettisoned. About ten seconds later, the capsule’s systems automatically turned it around to have its heat shield facing the direction of travel, a position known as prograde.
During its ascent, the capsule passed an altitude of 100 kilometers, the Kármán line, putting Freedom 7 officially in outer space and making Alan Shepard the first American in space! Unlike Yuri Gagarin almost a month before him, however, Shepard did not go into orbit, but rather went on a suborbital trajectory, meaning that while he did go into space, he came back down almost immediately, unlike his Soviet counterpart who stayed up there for almost 108 minutes.
While in space, Shepard had two missions.
Shepard’s primary mission was to determine whether a space capsule could be controlled manually by an astronaut; to demonstrate this, he switched off the automated flight systems that were controlling the craft and switched to manual mode. He started by trying to control each axis one at a time and letting the automated systems control the rest, but he eventually did manage to take control of all three axes.
His secondary mission was to attempt to observe the Earth using a periscope. He reported being able to see the west coast of Florida and the Gulf of Mexico, the Bahamas, and even Lake Okeechobee, but he couldn’t see any cities.
At T+4 minutes and 44 seconds, Shepard put the capsule in “fly-by-wire” mode, in which the ship’s avionics are controlled not by mechanical transmissions but rather by electronic signals. He oriented the craft manually for the reentry maneuver in which the retro-rockets attached to the heat shield would fire to slow the capsule down. Shortly after reaching the peak of his suborbital trajectory at T+5 minutes and 14 seconds and an altitude of 187.5 kilometers, the rockets fired successfully and Freedom 7 began its descent.
It was then that Shepard started feeling gravitational forces kicking in again, but to Shepard’s surprise, that happened about a minute before it was supposed to according to his training. Still in fly-by-wire mode, he fought to stabilize the spacecraft as the G-forces were building up — reaching a peak of 11.6 Gs! — but as soon as the point of peak G passed, the spacecraft stabilized enough for Shepard to go back to automatic control.
Still, the capsule was falling at a much higher-than-anticipated speed. Shepard stopped relaying his instrument readings to mission control so he could listen for the deployment of the drogue chutes, which deployed successfully at T+9 minutes and 38 seconds. They slowed the craft down enough for the main chute to deploy at an altitude of three kilometers at T+10 minutes, 15 seconds.
Freedom 7 then continued parachuting down towards the North Atlantic at a speed of about 38 kilometers an hour, and at T+15:22 splashed down successfully in the Atlantic Ocean, where it was promptly recovered by the USS Lake Champlain. Safely back on the ground after four hours of waiting and nearly fifteen and a half minutes of flight, Alan Shepard, the first American in space, became a national hero.
Last-Minute Qualms (NASA History)
Shepard’s Ride (NASA History)