Review: “The Seventh Landing: Going Back to the Moon, This Time to Stay”

“The Seventh Landing” written and illustrated by Michael Carroll. Published in 2009 by Springer Science+Business Media, it weighs in at 174 pages all in. About a half-dozen editing errors noted, including the rather unusual “tikonauts” for “taikonauts” (the name for Chinese astronauts, like the Russian cosmonaut or French spationaute).

One way that NASA’s Constellation program was sold to the public was that it would provide a return to the Moon, which became conflated in the media and public’s minds as Constellation = Back to the Moon. Never mind that the rockets were named after the Greek god of war, Ares, better known by his Roman name – Mars. In “The Seventh Landing”, the author attempts to explain the broader context of the Constellation effort, but once again it is couched in terms of a return to the Moon.

The book opens with acknowledgements, a brief background on the author’s extensive background in science writing and space art, and a foreword from the go-to guy for Apollo quotes, John Logsdon. The introduction is subtitled “Doing it Right”, and provides a brief on the transition from Apollo to Constellation and the basic elements of the program. After some inspirational quotes, we dive into the main body of the work.

The first chapter is a summary of what has gone before, from the first robotic probes to crewed missions to the surface of the Moon, with a fair amount of detail on the equipment and crews. The backgrounder takes up the first 20% of the content. The next chapter looks at getting there the second time around. It touches on existing launch vehicles, the Evolved Expendable Launch Vehicles, or EELVs, better know as Delta IV and Atlas V, but through extensive quoting of NASA sources dismisses them as viable, especially when compared with the certain success of the Ares I and Ares V rockets, which the author covers extensively.

So we’re 40% of the way through the book before we start focusing on the Moon. Chapter three looks at Shackleton crater at the Lunar south pole, NASA’s designated baseline go-to site for Lunar return architecture design. The author looks at the various advantages offered by a location at the south pole, although one comment did throw me – “The Moon’s axis is tilted 5 degrees off the Earth-Moon line of sight”.

Orbital mechanics is a tricky thing, a weird combination of geometry and calculus. Basically, the Earth orbits around the Sun and that creates the two dimensional Plane of the Ecliptic. It is called the ecliptic because eclipses only occur when the Moon crosses this plane. Relative to this plane, the Moon’s rotational axis is inclined about 1.5 degrees, or basically straight up and down compared with the Sun. This is what allows for there to be everdark craters at the Lunar poles – the Moon isn’t tilted enough for the Sun to shine down in there.

The Earth is tilted relative to the plane of the ecliptic by about 23.5 degrees. This much greater tilt is what creates the six months of light/dark in the polar reaches. So the two dimensional plane created by the Earth’s equator extended out to infinity, the Equatorial Plane, is inclined 23.5 degrees to the Plane of the Ecliptic.

The two dimensional plane created by the orbit of the Moon around the Earth is inclined a bit over 5 degrees relative to the Ecliptic Plane. Sometimes the orbit is above the Ecliptic Plane, and sometimes below it, which means that relative to the Plane of the Equator that inclination ranges from a max of about 28.5 degrees (23.5 + 5 when above the ecliptic plane), which is about the latitude of Kennedy Space Center which makes it an excellent launch site for direct-to-the-Moon mission architectures and easy launch window calculations, to a min of about 18.5 degrees (23.5 – 5 when below the ecliptic plane). [Edit: corrected the backward ecliptic/equatorial]


Not from the book

Things are further complicated by the fact that “line of sight’ is also a function of where one is on the surface of the Earth. Far northern or southern latitudes have a different view from equatorial locales, and Moon on the eastern horizon offers a different view from the Moon on the western horizon (also known as the ‘librations’ that allow us to peek around the edges)

So the Moon’s axis is tilted X degrees off the Earth-Moon line of sight, where X is a function of where the Moon is in it’s orbit relative to the plane of the equator (23.5 ± 5 degrees relative to the Plane of the Ecliptic) and the Moon’s axial tilt (± 1.5 degrees from the Plane of the Ecliptic) and a fudge factor for where one is on the Earth. Oh, and how far away the Moon is from the Earth, as the about 5% eccentricity in the Moon’s orbit gives it a perigee of about 354,000 km and an apogee of about 404,000 km (only averaging 384,404 km, the number ususally seen for the distance of the Moon).

Then of course you also have to allow for the perturbations which nudge the Moon from where it would be in its orbit in an isolated system. The two biggest perturbers are the Sun and Jupiter, by virtue of their huge masses, but all of the planets have a minor affect, and even the pudginess of the Earth around its middle. Calculations of where the Moon is going to be in its orbit involve over 150 variables. Which only highlights how important a solid knowledge of math is if you want to be into orbital mechanics.

Back to the book, the chapter spends the last half looking at the kinds of spacesuits NASA is thinking about for surface operations. Chapter four looks at the tools that humans will use in their return to the Moon, the robots, as well as basic habitats and sorties out on the surface. Chapter five looks at the scientific rationales for a Lunar return, but doesn’t really go deeply enough into why they’re important.

Why do we want to study the impact record on the Moon? Sure it will give us insight into the history of impacts here on Earth, but we already know that rocks have struck Earth throughout history, so it’s easy to assume that they will continue to strike the Earth in the future.

One example of why we want to study the impact record is to look for cyclicality in the impact record. Why? Well, there’s one scientific theory that in the course of the Sun’s orbit around the galactic core, a trip of roughly some 225 million years, very very roughly, the sun bobs up and down like a carousel horse through the galactic plane and whatever cosmic debris is in that galactic plane. The crater record here on Earth is giving off strong hints of minor big impacts every 30-odd million years, and major big impacts every 60-odd million years. The widely acknowledged (but not yet ‘proven’) dinosaur-killing impact was about 65 million years ago, and the one that gave rise to the dinosaurs was about 4x as long ago at about 250 million years.

So, is there cyclicality in the impact record (and if so, where are we in that cycle?) is a valid scientific question, and upon consideration a reasonably important one. The dynamic processes of Earth make reading the past difficult, while the Moon’s largely static nature has preserved a history of impacts. When we go back to the Moon we can start analysing craters – when they were made, how big they are, what was the impactor made of, and so on, and start filling in the impact record with much better data, and from that derive better scientific theories for the impact history.

Here’s another one – the Sun is vitally important to the health of the Earth. During its functioning, the Sun blows off a constant stream of lighter particles (basically everything up to oxygen in decreasing amounts) into the Solar system called the Solar wind. In the vicinity of Earth these particles either flow around the magnetosphere, or get bound up in the Van Allen belts giving us pretty aurorae. The Moon lacks a global magnetic field, and so the Solar wind goes barreling into the Moon’s surface at full speed and gets trapped in the regolith. These Solar Wind Implanted Elements, or SWIEs, are foreseen as an industrial by-product of things like oxygen-extraction, but they also provide a history of what the Sun’s output was over the course of its history. It will be very important to understand the impact record (see above) to understand which layer of regolith was exposed when to the Sun’s rays, but the benefit will be a much better ‘medical history’ of the single most important factor of life on on Earth.

But the reader doesn’t get that kind of reasoned rationales for the science, they get the usual ‘scientists are looking for insights into basic questions’ gloss that has become so common in space books. So even at 20 pages, it’s a rather superficial treatment of the topic.


The last chapter spends the last 20% of the book talking about “THE GOAL”, going to Mars. It covers the history of dreams of travel to the red planet, as well as current rationales. This is followed by an afterword from Chris McKay of NASA Ames, chapter notes, a gallery of some beautiful paintings by the author, a list of all of the Moon missions through Chandrayaan 1, Mars and asteroid/comet missions through Rosetta, and an index.

The book is squarely positioned for the lay person market, and is suitable down to about the middle school level. Overall, I was disappointed in the book, as it could have been so much more.

Like Erik Seedhouse’s “Lunar Outpost“, it focuses too much on the Ares launch vehicles, which dates the book even though it’s fairly fresh off the presses. The book also relies heavily on quotes from NASA people involved with the Constellation program, which at times gave the text the feel of a press release, or a propaganda exercise. For a book about going to the Moon to stay, spending less than 40% of the text on the Moon itself seems a bit disjointed. Why is so much time spent on Mars (1/5th of the text) in a book ostensibly about going to the Moon permanently?

In its favor, the art is wonderful. There are a number of pieces by the author reproduced throughout the book, and I would love to get an original of one for the Lunar Library. Additionally, given the overall educational level most people in the U.S. have regarding space (basically middle school level, unless they took astronomy in college), it is in fact informative and will give a better perspective on the reasons to do Lunar activities.

Ultimately, though, I can’t do better than a half Moon for “The Seventh Landing”.

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