Today's word is ... "frangible"

Frangible items are designed to break into fragments, rather than deforming and remaining a single piece.

The space program makes wide use of frangible nuts and bolts as connectors that hold items together until an exact moment when they have to be separated quickly. This quick separation is accomplished with an explosive charge, referred to as a "pyro" (for pyrotechnic device) or an NSD ("NASA Standard Detonator"). The astronaut (or the computer system) throws a switch to activate a certain sequence; the pyro blows and the frangible nuts and bolts that held the item together shatter, allowing the items to separate.

Examples of this in action would be separating the spent solid rocket boosters from the Space Shuttle, releasing a satellite from the Shuttle's payload bay, or even deploying the spring-loaded solar panels on the MER Mars rovers. The frangible nuts and bolts in the picture above are from the Space Shuttle program.

In my mind, the most famous film depiction of pyros was in 2001: A Space Odyssey, when the explosive bolts were used to blow off the EVA pod's door so that Dave Bowman could quickly enter the emergency airlock.

Gemini VI and VII rendezvous

Gemini VI, commanded by Wally Schirra with Tom Stafford flying as Pilot, was launched on December 15, 1966. In what was perhaps the most significant "space first" of the US to that date, it was the first time two piloted vehicles had successfully rendezvoused in orbit.

The mission of Gemini VI changed substantially from its initial concept. Originally, Gemini VI was to have docked with an Agena target vehicle in October 1966. However, the Agena failed during launch and never reached orbit. The Gemini VI vehicle lacked the fuel cells needed for a long-duration space flight like Gemini VII, but NASA worked out a quick mission that would demonstrate rendezvous capability.

I remember the excitement of seeing the photos from the mission, which quickly became available just after Gemini VI landed the next day. There was no TV from spacecraft at that point, so we couldn't see the event as it happened, and we had to settle for still photos in the newspapers and magazines. It was so cool to see a photo of an actual capsule in orbit. It was the first time the general public had ever seen something like that...our views of spaceflight up to that point had only been launch, recovery, and pictures taken out the window. Now, we got to see the full Gemini spacecraft, with its contrasting black capsule and white adapter sections, and the surprise of the gold foil tendrils snaking out the back of the ship.

These two items from my collection are an access badge to the Gemini VI spacecraft, from the collection of a former ground crew worker at KSC, and a small fragment of the heat shield from Gemini VI.

Challenger on the Moon

Gene Cernan and Jack Schmitt landed "Challenger" in the Moon's Taurus-Littrow valley on December 11, 1972. They spent three days exploring the hills and valley, sending back the clearest TV pictures yet from the surface of the Moon.

On board the LM, like every spacecraft, was the equivalent of a car's "owner's manual," describing all the systems in case something needed troubleshooting when 240,000 miles away from home. This diagram is a page taken from Gene Cernan's actual Flight Data File for the Apollo 17 mission. It went with him to the surface of the Moon, and it is perhaps the prize of my collection. Cernan signed it for me when I met him at the National Air and Space Museum on November 3, 2006. This particular page of the Flight Data File deals with overcoming trouble with the Abort Guidance System (AGS), one of the two navigation systems on the LM.

The Flight Data Files were kept in pouches behind the Commander's station. This photo, taken in the LM after the conclusion of the third and final moonwalk of the mission, shows the astronauts' helmets and space suits piled on the cover of the ascent engine. The pouches on the wall on the right side of the photo contain the Flight Data Files. I get chills every time that I think that I have a page of one of the notebooks inside those pouches, something that went to the Moon and back!

Skylab Rescue Mission (SL-R)

Skylab is considered the least-remembered part of the Apollo program. If people do recall Skylab, it is likely because of the "sky is falling" fears it evoked in 1979 when it was about to re-enter the Earth's atmosphere. Because it was an uncontrolled re-entry, no one knew how much of it would survive re-entry, or even where or when it would come down. I remember "Skylab pools" with people betting on the date it would come back to Earth.

Those who were really paying attention may remember that the entire Skylab project was in serious jeopardy starting 63 seconds after the station's launch, when the meteoroid shield ripped off of the space station and tore off one of the station's two key solar panel wings. The heroic efforts of the first crew to man the station, led by Pete Conrad, led to Skylab becoming habitable and useful for its three long-duration crew stays.

The second crew to visit Skylab, commanded by Al Bean, encountered difficulties with their Apollo spacecraft prior to docking, when one of the four quads of reaction control system (RCS) thrusters on the Service Module developed a leak and had to be shut down. A second RCS quad also developed a leak and also had to be disabled. There was deep concern that the Apollo spacecraft, which the crew would need for return to Earth, could not be controlled adequately with half of the RCS thrusters out of action.

The 1969 movie "Marooned", followed by the 1970 Apollo 13 near-disaster, were still fresh in people's minds. We didn't want to contemplate a crew of astronauts stranded in orbit.

NASA decided to prepare a spacecraft for a potential rescue mission, should it become necessary. A Command Module was adapted to hold five crewmen instead of three. Astronauts Vance Brand and Don Lind were selected as the crew for SL-R, the Skylab Rescue mission. NASA ultimately determined that the Skylab crew would be able to get home safely. Nonetheless, they retained the idea of using a modified ship as a contingency rescue vehicle for the last Skylab crew.

The vehicle was rolled out to the launch pad on December 3, 1973. It was ultimately not needed, so it was rolled back to the Vehicle Assembly Building after the conclusion of the last Skylab mission. This CM became the backup CM for the Apollo-Soyuz Test Project (ASTP). It is on display in the visitors center at the Kennedy Space Center.

Vance Brand got to fly on the ASTP mission in July 1975. Don Lind wouldn't get his first flight for 11 years, on Space Shuttle mission STS-51-B in 1985.

Apollo 17 special crew commemorative patches

The Apollo 17 crew commissioned a special set of patches from AB Emblem. These were larger than the 'standard' crew patches, and they were marked with initials of each crew member sewn into the background between Apollo's shoulder and the galaxy. There were reportedly about 150 of these patches made for each crewman's initials. The star above Apollo's shoulder also distinguishes these from other embroidered patches. It's there on the Beta cloth patch and the original artwork, but on neither AB's standard patch nor the Lion Brothers version.

Two of the patches in my collection are still in their original plastic wrappers, making it somewhat hard to see the initials in this scan. Ron Evan's patch is at the upper left, Gene Cernan's in the middle, and Harrison Schmitt's is at the lower left.

These patches were not available to collectors at the time of the flights. They only started coming onto the market in the 1990s

Launch of the last Moon mission

December 7, 1972 opened with a spectacular nighttime launch of Apollo 17. It was the first launch of an American manned mission at night, and the only night launch of the Apollo program. The next night launch of an American manned mission would not be until 1983.

This was the first Apollo launch that I wasn't able to hear on the radio or watch on TV, as I was in the hospital. I was back home in time to catch some of the lunar EVAs, but the networks were no longer covering them in toto.

This cover is from Apollo 17 Commander Gene Cernan's collection. He had it autographed by his crewmates, and it was postmarked on the 25th and 30th anniversary of the launch. I find it somewhat unusual in that Harrison Schmitt signed this as "Jack" Schmitt. I have not seen any other signed items where he used his nickname. Perhaps it was because he was signing for his crewmate rather than for the general public. This is also the only item I have that is signed by Ron Evans, who died in 1990.

Race for the Moon

Forty years ago today, Time magazine's cover story was about the final sprint to the Moon, as the US and USSR raced to be the first country to send people there. The cover art accurately portrayed the feeling of the time, that this was indeed a high-stakes race. We had been beaten by the Russians in so many 'firsts' that we were constantly wondering what they would and could do to trump us, always unexpectedly.

The US had publicly announced plans to send Apollo 8 to orbit the Moon in December. The earliest we could send a mission was to launch on December 21, 1968. The launch window was dictated by the need to get to the Moon when it was at the same phase for the planned landing attempts in 1969, and also to time the mission so that splashdown back on Earth would be in 'friendly' waters.

We did not know what the Russian plans were, but we could guess. The Soviet launch window was earlier in the month, and there was a real fear that the Russians would send men to the Moon before us. Indeed, the Russians had sent up circumlunar spacecraft in September and November that year. It wasn't publicly known in the US at the time, but these two spacecraft were not just Moon probes - they could have carried a manned crew. Had the USSR been willing to take the risk, they could have beaten us to the Moon by at least a month. They could not have made a landing in 1969, but their having sent men to the Moon before the US would certainly have lessened our feeling of accomplishment.

As it turned out, the decision not to send men on the November flight was the correct one. The 'crew' of biological specimens perished when a faulty O-ring gasket caused the cabin to depressurize before reentry, and a parachute deployed early, causing the capsule to crash. Either failure would have killed a human crew. The Soviets were not able to fix the design faults in time to make an early December launch, which enabled the US to be the first to send men around the Moon.