Monday, February 22, 2010

Spacecraft of the Week #15

Long past time for a new Spacecraft of the Week. I've missed several weeks due to job and family responsibilities. So in starting over anew we'll honor an anniversary this week (or, rather, last Saturday) and present the Mercury MA-6 spacecraft flown by Co. John Glenn on February 20, 1962, Friendship 7.

Continuing in the tradition established by Alan Shepard and Gus Grissom, Glenn included the numeral 7 as he chose Friendship as his craft's name. Although born of the Cold War, America's civilian space program was conducted in the name of peace and international goodwill. Friendship 7 finally enabled America to match the Soviet feat of orbiting a man around the Earth. But what was our successful first threatened to come to a fiery end.

First an aside. The Soviets knew as the Americans that a return to Earth from space would produce an incredible array of forces both on the spacecraft and its human occupant. Deceleration could be accomplished with parachutes and/or rockets, but these added weight to the spacecraft. Since the Soviet designers included an ejection seat to safely remove the cosmonaut during a launch mishap, they utilized this to allow the returning traveler to separate himself from his craft and descend by his own parachute, allowing the spacecraft to land with a force greater than a human could bare. Why do this? So that all aspects of flight and landing could occur safely within the confines of the mother country, where stories could be tightly controlled.

NASA, meanwhile, opted to use the vast oceans and its powerful naval forces to recover its astronauts and spacecraft. While water landing reduces the shock of impact, more cusioning was needed. So the capsule was designed with a mechanism to detach the protective heat shield and drop down extending a cylindrical skirt. This skirt would fill with air, and provide a cushion to the craft and it's rider. It was this detachable shield that created the drama.

As Glenn orbited the Earth, ground controllers at mission control in Cape Canaveral saw a disconcerting sight: the light indicating detachment of the shield was illuminated. This could prove catastrophic, as the heat shield protected the craft during re-entry. If detached, it would be torn away and the spaceship and its occupant would disintegrate in a meteoric fireball. A plan was developed, and the message was sent to Glenn to not eject the retro pack. They did not tell Glenn this was meant to hold the head shield in place, hopefully long enough to do its job. Glenn caught on fast and figured out it was something with the heat shield. The resulting reentry was especially spectacular as the retro pack burned away. It was later found the sensor was faulty and there was no danger from a deployed shield, but the experience led to new guidelines in crisis management and communication with the astronaut.

Currently, Friendship 7 is displayed in the National Air & Space Museum under the Wright Flyer. A layer of plexiglas protects it from the thousands of visitors daily. While the plexiglas makes photography difficult, it does allow guests to get very close with this historic craft. It's difficult to imagine a human being sitting inside this small vehicle and hurtling through the heavens. So we salute our first orbiting astronaut and the spacecraft in which he traveled as our Spacecraft of the Week.