Twins in Space | This Week In Space History
by dave dooling
Fifty years ago this week a Titan II missile launched the first flight test model of a two-man spacecraft, Gemini 1.
Apollo, the three-man lunar spacecraft, would require two Saturn V launches, one for the spacecraft and a second for a refueling stage to boost it to the Moon. But no one had ever brought two spacecraft together in orbit. Even the Soviets’ two twin-Vostok missions had just put the spacecraft into closely timed orbits.
Even before President Kennedy’s challenge to go to the Moon, NASA had been eying the solution: Mercury Mark II, a two-man spacecraft launched by the Air Force’s new Titan II ballistic missile.
While it outwardly resembled Mercury – a truncated cone covered by black heat-resistant alloy shingles – it sported important differences. The black capsule sat atop a white adapter section that carried batteries – later electrical fuel cells –maneuvering thrusters, electronics, and retrorockets.
Most noticeable, it had no escape tower. The Titan II used burned nasty nitrogen-based propellants that could be stored for long periods and ignite on contact. They were less volatile than the liquid oxygen used on other launchers, and produced a less powerful fireball. This meant the astronauts could bail out in jet fighter-style ejection seats. Since the hatches opened and closed on hinges to let the crew in and out, they could also be opened in orbit to let astronauts venture out of the spacecraft.
But before that, the spacecraft, soon renamed for the constellation Gemini, the twins, had to prove itself. Unlike the many launches that preceded the first primate and then human flights on Mercury, just two Gemini test flights were planned.
At the same time, what might be good enough for a military missile often fell far short for a man-rated rocket. Historians James M. Grimwood and Barton C. Hacker noted that the Titan II needed not only “a fully redundant malfunction detection system but also a backup flight control system; an electrical system with backup circuits for guidance, engine shutdown, and staging; inertial instead of radio guidance; and a new launch tracking system.”
Most disconcerting was that Titan oscillated like a pogo stick during first-stage burn. A “water hammer” effect resonated through the rocket from 90 to 120 seconds after launch. “Bouncing at an extra two and a half gravities (+2.5g) could badly hamper a pilot’s efforts to respond to an emergency, a matter of special concern in Gemini since the crew played so large a role in flying the spacecraft,” Hacker and Grimwood noted. Other problems plagued Titan, and only half its first 20 flights were complete successes. Pogo seemed so intractable that NASA considered using the Saturn I rocket, oversized but reliable. But by early 1964, Martin Marietta and Aerojet had reworked the plumbing and turned the Titan into a more reliable launcher for both NASA and the Air Force. Soon it would grow into the powerful Titan III family of launchers.
In the meantime, Apollo’s design had changed from two Saturn V launches and a single spacecraft to two smaller spacecraft, one a lunar lander, on a single Saturn. Perfecting rendezvous and docking became more crucial.
Meanwhile, Gemini 1 neared completion, or half-completion if you will. It carried ballast in place of many systems needed for a complete spacecraft. Even the heat shield had “Four large holes bored in the ablative material [that] ensured the total destruction of the spacecraft when it plunged back into the atmosphere,” Hacker and Grimwood wrote. On Sept. 30, 1963, the completed spacecraft was accepted by NASA and shipped to Cape Canaveral. Another six months of tests, trouble-shooting, and fixes followed as engineers worked through problems ranging from fitting heat shield shingles to getting the right paperwork.
Gemini 1 was finally mated to its launcher in March 1964. Rocket and spaceship now were an integrated unit. More tests, problems, and solutions followed. As expensive and complex as space missions are, they still resemble a cheap string of Christmas tree lights: Everything works, or nothing lights up. Even the final countdown test was stymied when a motor for switching to emergency power on the launch pad burned out. A replacement was stolen from the blockhouse.
Suddenly, everything seemed to work right. A countdown demonstration, complete with propellant loading on April 2, and then spacecraft tests on April 5, cleared the way. Finally, on April 8, 1964, GT-1 rocketed into orbit. Air Force Maj. Gen. Ben Funk, Space Systems Division, called it “just completely a storybook sort of flight.”
Because this was just a launch test, Gemini 1 wasn’t even equipped to separate from the Titan second stage. NASA monitored the craft for three orbits, then tracked it for four days until its orbit decayed over the South Atlantic.
“But the glow of accomplishment soon faded before the hard work yet to be done,” Hacker and Grimwood wrote. “While the launch vehicle was now qualified for manned missions, the spacecraft was not. Despite the gratifying success of Gemini-Titan 1, and some real progress on troublesome spacecraft systems, there was no time to rest on laurels.”
GT-2, on Jan. 19, 1965, would test the spacecraft’s heat shield and other systems on a suborbital hop. Just two months later would come the Gemini 3, the first of ten successful missions.
This story draws from “Project Gemini Technology and Operations, A Chronology,“ by James M. Grimwood and Barton C. Hacker, and Peter J. Vorzimmer (NASA SP-4002, 1969), and “On the Shoulders of Titans: A History of Project Gemini,” by Barton C. Hacker and James M. Grimwood (NASA SP-4203, 1977).
Dave Dooling is education director at the New Mexico Museum of Space History. He is a former space journalist and past recipient of the National Space Club’s Press Award and Goddard History Essay Award.