Lunar Lava Tubes Larger than Expected

We knew there were lava tubes on the moon and Mars.  But we thought the ones on the moon were no more than 500 meters in diameter.  A recent study of gravity data shows two voids larger than that, and an engineering study shows the tunnels can be up to 5 km across - large enough for a substantial city.

Lava tubes are caves formed when lava from a volcano flows underground, then leaves behind a cylindrical tunnel. Caves like this on earth can be up to 30 meters across. Gravity surveys of the moon indicate much larger voids under the surface. A new study indicates that A) tubes over 1 km in diameter may have been detected under the surface by the GRAIL orbiter, and B) a natural lava tube of up to 5 km may be stable under lunar conditions. Earlier estimates were 500 meters maximum, but this assumed a softer material for lunar basalt. The 5 km estimate for a maximum void is based on ideal conditions and a natural arch geometry that is mathematically close to those of earth lava tubes (which given the variation in gravity, may or may not be true). But it would account for the 1000 meter voids that appear to have been detected by GRAIL.

The two largest tubes detected are at Vallis Schroteri and Rima Sharp. The problem is that GRAIL data would be identical if the voids are 3 centimeters or several hundred meters below the surface. For reference, a tube would have to be at least 5 meters below the surface to block cosmic rays, and more is better. The temperature below ground would be consistently – 20 degrees C, or -5 degrees F. This is far better than the dramatic variation at the surface, although this variation is less extreme near the poles. Lava tubes are generally found near the edges of lunar mares and highlands.

After finding three apparent pits or skylight caves from earlier probes, LRO found an additional 150 candidate holes in the surface. Even a simple pit (with no useful lava tube) would provide cosmic ray and meteor impact shrapnel (ejecta) protection from the sides for a small outpost.

PROBLEM:  The lunar surface is exposed to extreme temperature changes between night and day, cosmic radiation, solar flares, and micro-meteor "rain".   The trouble is finding these caves, determining their size and determining how large and accessible they are.  This study does a lot of work in that direction.

OPPORTUNITY:  Being able to drop under the surface without having to dig for it removes a substantial engineering task from the earliest outposts, by simply lowering the base habitat into a skylight cave and connecting it to the surface. Lava tubes under the surface could theoretically be lined, sealed, and pressurized into vast habitat spaces with minimal excavation.

Further Reading:  
Original Source Paper.  
Next Big Future Blog Article.  
Science News Article.

EM-Drive, Cannae, and The Implications for Propellantless Rockets

​While much fuss is made over the possibility of EM-Drive, there are actually two propellant-less, low trust concepts being evaluated. Cannae has similar properties, but depends on superconductors to operate. There are plans to do a demonstration satellite in the next few years.

In the near term, these rockets could make extensive surveys of the asteroid belt and outer solar system possible for light spacecraft.  They would provide another strong incentive to build space-rated nuclear reactors. Finally, we could get beautiful images of the planets around the Alpha/Proxima Centari system - by flying a probe in the exact opposite direction.

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Introducing MacroInvent

Sunrise at Mars Desert Research Station during Greenhouse Construction Project

This site is devoted to teaching the fundamentals of becoming an inventor and entrepreneur. You may have heard Elon Musk refer to Platonic ideals with regard to Tesla car design, or discuss First Principles when reducing costs at Space-X. He understands that you must have a clear focus on ideals when building the best products. Those principles date back thousands of years. We’ll dig into the deeper history of how humans solve problems.

The motto of this site is “A million mini-Musks”.

That said, I don’t expect you to read this site, then immediately work eighty-hour weeks and become a billionaire by age 40.

But what if a few hundred or a few thousand people understood how to solve problems like the greatest inventors and entrepreneurs throughout history, including Elon Musk? What would the cumulative impact of all that creativity and focus be, particularly on those who could do so?

I’d like to find out. I’d like you to be one of those success stories.

The first book’s core content is completed under Invention and Mind. The next will be started in the coming months, and Invention and Mind will be expanded and published to Kindle.

Kent Nebergall

Elon Musk Creates Massive Opportunity for Entrepreneurship

“The goal of Space-X is really to build the transport system. It’s like building the Union Pacific Railroad. And once that transport system is built, then there’s a tremendous opportunity for anyone who wants to go to Mars and create something new, or build the foundations of a new planet. So, who wants to be among the founding members of a new planet, and like I said, build everything from iron refineries to the first pizza joint? We’ll want them all. And then there’s things on Mars that people can’t even imagine today, that might be unique, or would be unique, to Mars.
That’s really where a tremendous amount of entrepreneurship and talent would flourish. Just as happened in California when the Union Pacific Railroad was completed. When they were building the Union Pacific, a lot of people said that was a super dumb idea because hardly anybody lives in California. But today, we’ve got the US epicenter of technology developments, and entertainment, and it’s the biggest state in the nation. But you need that transport link. If you can’t get there, none of those opportunities exist. So our goal is just to make sure you can get there.” – Elon Musk

And the goal of is to create that very talent and opportunity for space settlement. I’m so happy to hear him say this. I was concerned (the term in business planning is threat analysis) that his announcement would include a fully designed space settlement, not just the rocket. But he’s leaving that to the rest of us. Thanks Space-X!!!