Well, there they are! My logbooks containing years of research into how rocket exhaust blows soil.
2/ Remembering the strange things I looked into, so long ago... Analyzing the sandblasting on the Surveyor 3 landing strut, which was clipped off the Surveyor by Apollo 12 astronauts who visited its landing site 2.5 years later.
This is the one that went to a volcano for a field testing with a rocket thruster blowing volcanic ash. Poor notebook had a rough go of it!
4/ Trying to figure out which directions the soil flows in and around a growing crater under the rocket exhaust. (This is for Mars.) We made good progress but still trying to solve it. Will be supporting @mastenspace on some exciting experiments over the next year and a half.
5/ A tangent into granular physics theory. This equation is an early version of the Boltzmann collision integral extended to multiple time dimensions with time symmetry in each. *Believe it or not*, this correctly solves the micromechanical forces in sand. journals.aps.org/pre/abstract/1…
6/ Ah, I recall this. If 3 sand grains are touching, they can’t rotate since they can’t alternate clockwise/counterclockwise around the loop. But loops of 4 grains can rotate. Put that info into a matrix and it predicts some cool things about sand piles. aip.scitation.org/doi/pdf/10.106…
7/ It predicted that every little frustrated loop of “gears” can preserve a quantum of locked-in stress inside the loop. The loop stresses are independent of the external stress applied to the sand pile. They are fossilized thermal vibrations from before the pile became static.
8/ A granular jamming diagram and below that a sketch of an alligator claw print. This is when we were founding the KSC Swamp Works and trying to decide how to brand it. The robot alligator beat out the claw print.
9/ Kind of ridiculous. About 9 years ago, I was listing technologies that needed developing for the Moon, Mars, Ceres (😆), and...comets??? 😅 And for some reason I decided to use their astronomical symbols instead of writing the names, lol.🙄 I think I just liked Ceres’ symbol.
10/ Oh, and then there was the next page, where “Roadmap” and “Dust Mitigation” for some reason turned into Lord of the Rings 🙄😂
11/ AHA!!! Here’s an idea to speed up 3D printing of lunar soil. Just melt the darned soil into lava and pour it into moulds. Brute force method! (I’m showing this since it can’t be patented and I have no plans to pursue the idea further. Have at it.)
12/ I remember doing this during a layover in the Charlotte airport. I had to develop a 2D axisymmetric version of the Crank Nicolson method of integrating the heat flow equation. This predicts how heat flows around a lunar drill. Did this for the Resource Prospector mission.
13/ But some days you can’t write down a decent equation.
14/ Some elvish, and a sketch from a talk I saw @JeffGreason give at a conference: how to hold down a giant pressurized dome in low lunar gravity.
15/15 Some sketches while analyzing experiments of gas jets blasting craters in various granular materials. We saw a lot of really weird phenomena. This part of the research was started by @LauraForczyk when she interned with me at NASA, and is still ongoing with @mastenspace.

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More from @DrPhiltill

24 Oct
I was in Home Depot and saw the Farmer’s Almanac in the checkout line so I snapped this. Almanacs since the 1600s have been publishing lists of planets. It is a fascinating window into culture’s evolving ideas about planets. Astronomy textbooks don’t tell the true story. 1/N
2/ For example, in this 2020 almanac, the list is almost identical those going back to 1800 with only a few changes. 1) It includes Pluto. 2) It avoids calling the objects “planets”. It lumps them together with the lunar nodes and calls them “Celestial Symbols”. I was surprised!
3/ In the early 1800s, the public had *only just* converted to heliocentrism. It took 200 years after Galileo to be convinced. So in 1800 the public’s idea of “planets” was still the “Old Geocentric 7” including the Sun as a planet. Here are lists from almanacs in 1803 & 1806.
Read 26 tweets
5 Oct
Saw a gorgeous ant pile this morning. Because the soil particles were wet they had cohesion, and as the ants dropped them the normal distance from the hole they did not avalanche down the sides as usual. Instead, they built a vertical wall with an overhang. So fascinating!
Also noticed water droplets glistening on the large Elephant Ear leaves. Some leaves had droplets while others had none at all! I assume the older leaves lose their hydrophobic, waxy coatings so the water runs off, but that’s just a guess.
Also, check out the shape of the new Elephant Ear leaves as they are just beginning to unfurl. So interesting!
Read 10 tweets
18 Sep
Three scenarios how industry may develop in space. "Civilization Fully Revolutionized" means offloading industrial footprint from Earth to save the planet, all humans benefit from developed economies (health care, etc..."Post Scarcity"), vastly greater horizons for science...1 Image
2/...reaching to the stars. The Slow Growth Scenario means only government space agencies like NASA invest pre-economically in off-Earth industry, and we leave commercial businesses to slowly develop profitability and new business cases. Because space is hard, this is slow.
3/ The Rapid Bootstrapping Scenario means there are actors motivated to make it happen faster than the market forces will do. They may be visionary individuals with means, citizen-led movements, or governments that see the long-term benefit of getting beyond our planetary limit.
Read 9 tweets
12 Sep
Except if it was a 6-Earth-mass hamburger, gravity would immediately pull it into a sphere, the heat would melt it, it would differentiate, the metals from the meat going to the center to form a very tiny core. The main elements would be oxygen, carbon, hydrogen & nitrogen.../1
2/...in that order. They would form carbon dioxide (30.1%), water (45.5%), and methane (31.7%). There would be 1% nitrogen. Like Pluto the nitrogen would be in the atmosphere and surface ice. Maybe nitrogen glaciers would glow, like on Pluto!
3/ This “hamburger” would be quite hot, since it collapsed into a sphere all at once. Doubtless it would have liquid water oceans in the mantle. It would likely have a methane atmosphere like a Titan, but thicker with higher pressure since this is a 5-Earth mass burger.
Read 16 tweets
10 Sep
Some say, “This is the best idea for the future of humanity EVER!” Others say “This is colonialism that will destroy the Moon and enslave the poor!” IMO, both sides are seeing some real truth, and there’s a way that they fit together...(short thread) /1
2/ (Dives into this briar patch)

First, there is no risk of companies strip mining the Moon and ruining it until closer to the year 2100, because there are no valuable resources on the Moon that you can sell on Earth. You can get everything on Earth a million times cheaper.
3/ Second, we don’t have the technology to mine the Moon large-scale. The tech development *alone* will likely take 30 to 40 years to make a large-scale lunar mining venture economically viable. The key will be reducing the need for humans to stand around repairing broken robots.
Read 46 tweets
1 Sep
A visit from @deneigebroom @WFTV interviewing Gigi about her #breastcancer and running the virtual @bostonmarathon Sept 12. Gigi’s story is inspiring and we hope people will come cheer her race, making a comeback from chemo & raising funds for a great charity...
Gigi is supporting the Sisters Network, Orlando chapter, which is raising awareness of breast cancer among African American women and supporting women who have been diagnosed. gofundme.com/f/gigis-marath…
3/ Her ordeal was storybook amazing. She tried to run her 1st marathon in Feb. 2018 but at 20 miles she hit the wall HARD. A friend & I happened to be right where she passed out, holding her up her as she fell. She was incoherent but refused to stop trying. An ambulance took her.
Read 25 tweets

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