Christopher Wanjek




Date Reviewed:

January 1, 2021

he complete title for this book is Spacefarers: How Humans Will Settle the Moon, Mars and Beyond. This book, published in 2020, it is an up to date synopsis of mankind's next ventures into space. The opening chapters are explain some history (it's been 50 years since anyone last walked on the moon!) and describes the challenges of visiting space. Basically, it is both dangerous and expensive to boost any payload out of our deep gravity well, and once you get to space, humans are vulnerable to weightlessness and radiation. Living in space is hard. Providing food, water, air, pressure, shielding - all of these things are difficult. There needs to be a good reason to travel to space.

The presence of water on the moon makes a return to the lunar surface more attractive. By now, most readers will have already heard of the discovery of ancient ice in the deep craters at the moon's poles. The axis of the moon tilts only 1.5% (as opposed to the 23% tilt of the Earth), so sunlight never reaches the depths of the polar craters, which means that literally tons of water could be extracted. I did not realize how hard it would be to extract this frozen ice, it exists at temperatures so cold that chiseling the ice out would require a feat of engineering. I did not know that radiation danger is so great on the airless surface that a permanent base would require a layer of regolith 15 feet(!) thick to protect the shelter from cosmic rays. The moon rotates slowly, it takes a month to complete one rotation, which means its days and nights are two weeks long. Temperatures soar during the two week day, and then plunge to frigid lows during the night. I had not known that the Apollo missions were carefully timed to be on the lunar surface during the transition from night to day, the astronauts were only there at the dawn hours. If they had stayed longer, they would have roasted. I was also unaware of just how deadly the lunar dust is. It is statically charged, so it clings to everything, and because there is never any erosion due to wind or rain, the edges of the dust are sharp and corrosive.

So why go to the moon? The biggest lure is the molecules of He3 that have been embedded in the lunar surface by the sun over billions of years. He3 is ideal for powering fusion reactors. Unfortunately, we are still a decade away from being a decade away of having commercial fusion power. The second best incentive for returning to the moon is to extract water and materials. Once infrastructure is in place, it would be cheaper to send materials from the low-gravity lunar surface to Earth orbit, than it would be to lift those same materials up from the deep gravity well of Earth. The key, of course, is "once the infrastructure is in place". I wish that Wanjek had spent a lot more time discussing how mining robots would function and then the lunar base would transport the extracted resources to Low Earth Orbit.

The asteroids are the most intriguing. Wanjek says that there is enough material in the asteroid belt to support 10 trillion humans. I don't know that humanity could or should expand to such numbers, but that does indicate how much raw material is available to a future space faring civilization. There are three types of asteroids: C-type (Carbonaceous or primarily carbon based) which make up 75% of the total rocks, S-type (Silicaceous or primarily silicon based) which are another 20%, and remainder are M-type (Metal). Near Earth Asteroid UW158 is about 300 meters long but is estimated to contain billions of dollars worth of platinum (How do they know the composition of an asteroid we have never visited?). NASA had a plan, called the Asteroid Redirect Mission to visit an asteroid and retrieve a boulder for study, until the Trump White House killed it. I wish Wanjek had talked more about how to mine asteroids, and how to change their orbits. It seems to me that asteroids are the way to go - platinum, gold, titanium, cobalt and rare earth in incredible abundance is too juicy a target to pass up. Maybe use all those asteroid resources to build vast L-5 style colonies to house recreated ecosystems - could we build a forest, jungle or alpine wilderness in space, and stock it with endangered species, while humans lived beside them?

The case for Mars didn't sound too convincing to me - unless the goal is scientific research and the quest for life. Mars is so far away that astronauts would need to travel in a rotating ship to create artificial gravity, and if we can build rotating ships, we can colonize near space by building habitats with materials from the Moon and asteroids. Terraforming Mars by bombarding it with comets is theoretically possible, but currently way beyond our present technology.

The end of the book discusses the more exotic destinations: Mercury, the clouds of Venus, the moons of the gas giants, and colonizing comets. Given the huge amount of resources available in the asteroids, it would seem unnecessary for humans to travel to such challenging and distant locations, except perhaps on missions of science. There is no talk about destinations beyond our solar system. Did you know that the Oort Cloud doesn't begin until 10,000 AU? I had no idea it was so remote. The Oort Cloud extends from 0.8 to 3 light years from the sun. If we ever run out of asteroids to mine, we can send self-replicating robots out to those empty depths to tow home more rare materials, in some distant century hence...

Wanjek is an optimistic guy. At the end of the chapters, he predicts dates when mankind will achieve certain milestones. The first space hotels will open in 2025 (remember, this book was published in 2020, so that is very optimistic!). The first orbital ring station becomes operational early in the 22nd century. Humans back on the lunar surface in the 2020s, permanent lunar presence starting in the 2030s. Robot mining of asteroids commences in the 2030s. He predicts a Chinese / US race to Mars in the 2040s, with permanent presence in the 2050s. Humans will have solar sails and ion rockets and use them to visit the clouds of Venus and moons of Jupiter by the end of the 21st century. In the beginning of the book, Wanjek details the fifty years of frustration and inaction since the Apollo mission, so it is a surprise to see such hopeful predictions. People alive today could live to see these adventures come true. If only it were so.