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How NASA Engineered the Enduring Apollo Flags

A lot of thought went into designing the flags Apollo astronauts planted on the Moon.
August 1, 2012, 2:00pm

Apollo conspiracy theorists love pointing to the flags as proof that we didn't land on the Moon. "The flags look like they're blowing in the wind!" they cry. "There's no wind on the Moon so it's conclusive proof we never went." Not only is that a really weak argument (I'll explain why a little later on), but NASA now has conclusive proof that the flags are still standing at the Apollo landing sites. The agency's Lunar Reconnaissance Orbiter (LRO) has imaged not one but five Apollo flags on the surface.

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There's no wind on the Moon, nor is there any atmosphere. That means there's nothing to keep a flag from just falling limply against its pole. So, NASA devised a way to fake the look of a flag blowing in the wind.

About three months before Apollo 11 launched, NASA addressed the flag problem. The lack of atmosphere to support the flag was considered an "engineering constraint" and a minor one at that. Jack Kinzler, Chief of Technical Services Division at the Manned Spacecraft Centre, came up with the elegant solution: add a rod through the top of the flag so it would hang and show the stars and stripes in all their glory.

The Apollo 17 site. Via

The flag was a standard 3 × 5 foot nylon flag obtained through the government supply catalog. A hem sewn along the top housed the rod while a loop sewn around the bottom corner secured it to the pole.

Building the rig was a bigger challenge. Adding hardware to the mission meant stowing something that would add weight.

A team of engineers designed the flag assembly to be as lightweight and compact as possible. They managed to keep it small by developing a two-part telescoping pole apparatus with a telescoping crossbar. It stretched out to full size for easy stowage during the trip to the Moon. This design also took into consideration the astronauts' limited dexterity wearing their bulky Moon suits and matching gloves. Suits for the lunar EVAs were pressurized to about 3.7 pounds per square inch, which also limited how much force they could apply by squeezing their hands. Engineers also achieved the lightweight goal; the finished rig weighed just 9 pounds and 7 ounces.

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The flag was stored mounted on the left-hand side of the Lunar Module's ladder, the one astronauts crawled down to reach the surface. The advantage to storing it outside the LM was that it was one less thing to store inside the crowded spacecraft. The downside was that the flag would be exposed to the 250°F heat generated by the LM's descent engines. During the 13 seconds of the actual touchdown phase, the ladder was expected to experience temperatures up to 2,000ºF.

Apollo 16. Via

Pre-launch tests revealed the flag could sustain temperatures up to 300ºF, so a protective shroud was added to the list of necessary hardware. The Manned Spaceflight Centre's Structures and Mechanics Division developed a stainless steel outer case separated from an aluminum casing by a layer of Thermoflex insulation. Adding multiple layers of a thermal blanketing between the shroud and the flag did the trick. With all this protection, the flag wouldn't experience temperatures any hotter than 180ºF during the LM's landing.

Once on the Moon, an astronaut unfurled the flag by extending the telescoping crossbar and angling up past horizontal. As he lowered into a position perpendicular to the pole, a catch prevented it from slipping further. This upper portion then slipped into the base of the pole that he had previously driven into the ground using a geology hammer. A red ring around the base of the assembly 18 inches from the bottom told him when it was far enough into the ground to stay steady.

Six men have assembled and planted flags on the Moon. It's the force of driving this rig into the ground gave the flag the illusion of blowing in a breeze. The flag picked up momentum from the astronaut, and without any air particles to stop that momentum it kept "waving" after the astronauts released it to salute and pose for a photo op.

Once planted, the flag sat there looking patriotic while astronauts completed their surface objective, packed up the LM, and left the Moon. And they're still there. NASA's LRO has captured images of five of the six. Apollo 11's is the one flag that isn't still standing. Neil Armstrong and Buzz Aldrin put their flag a little too close to the LM. When they launched in the ascent module, the exhaust from the engine beat the flag up pretty good, knocking it over. LRO captured the lack of standing flag at the Apollo 11 site as proof.

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