Hello, and a special welcome to new subscribers. Each month I pick one short topic that is a treat for brains to think about.
Luna 13 a Solid Success
As we celebrate the 50th anniversary of Apollo, I thought I’d devote this Science Snack to some little-known lunar science performed by Soviet scientists in preparation for their own planned human landings on the Moon. The following is mostly an excerpt from my new book, Welcome to the Moon, which will be released June 17 from the Aldrin Family Foundation. (See book ordering information below.)
Buzz Aldrin tested soil hardness with this boot print. The length of the shadows reveal this print is less than an inch deep. Credit: NASA/B. Aldrin
One of the first questions that scientists had to answer is How Hard is it? “It” being the lunar surface! How strong do the legs of a lunar lander need to be? Will the foot pads sink deep into fluffy powder, break rocks into glasslike shards, or smack into solid stone? To find out, Russian engineers devised an experiment for Luna 13 to test the hardness of the lunar surface.
Like its predecessors, at an altitude of 46 miles, Luna 13 inflated airbags and fired its landing rockets. When it was 16 feet above the surface, the engines shut down as a sensor contacted the ground (a method still employed by Soyuz capsules). The landing capsule, in its airbag cocoon, was ejected and bounced several times before coming to rest in the Ocean of Storms.
After bouncing to a stop, Luna 13’s airbag deflated, and two booms sprang out from the body of the spacecraft. One boom contained a small solid rocket, pointed down. The rocket shot a titanium cone penetrator (with a diameter of 1.4”) into the ground. A pin slid along a groove in the side of the casing to measure how deep it went. The engineers had tested this penetrator on 14 different surfaces on Earth, including dust and concrete, and in a vacuum chamber ahead of time. Depending on the surface material, the penetrator could drill down two inches.
On Christmas Eve of 1966, the engineers got the gift of data from the Moon. The penetrator dove in 1.7 inches. The team concluded that the surface was volcanic rock (basalt) covered by a layer of powder.
Spacecraft cameras revealed rocks scattered on the surface. Of 181 rocks counted, most were pebbles. Only three were larger than four inches and all less than eight inches in diameter. The experiment gave the engineers confidence they could safely land a cosmonaut on this surface.
To learn more about the historical and current science of the Moon in "layman's" terms (written for gifted middle-school students), order your copy of Welcome to the Moon via my Book Orders page. (And Thank You!)
Writing about Space
To share what the first journey to the Moon was like, Buzz and I teamed up with pop-up artist Bruce Foster to create To the Moon and Back: my Apollo 11 Adventure. We hope you’ll get a copy to share this historical American story with the whole family.
I’m pleased to announce that my fact article, In Defense of the Planet, won the AnLab Readers’ poll! It is available FREE on the Analog website.
Speaking about Space
I offer programs appropriate for school-aged children up through senior citizens, as well as science workshops for students and teachers. See my list of programs on the Author Visits tab of my website.
Friday May 31, WriteFest Weekend Festival, Anderson-Clarke Center (6100 S. Main St. Houston, 77005), Rice University. The weekend festival includes panels, presentations, agent pitch sessions, and a book fair. Look for me on panels at 2:45 and 4 pm.
See my website’s contact page for a complete appearance schedule.