David (Hop) Hollister

David Hollister (Hop) Bio:

My sister, brother and I publish a weekly newspaper, the Ajo Copper News. It serves the small town of Ajo, Arizona. I wear a lot of hats but am mostly a graphics guy.

I studied art at Arizona State University.  A big influence was M.C. Escher. I blame Escher for my obsession with geometry. I've taught myself math by buying textbooks at yard sales, Googling, and participating in internet forums.

Johannes Kepler did a lot of visually stunning geometry. Through Kepler I became interested in conic sections and orbital mechanics. Also I've always been an avid science fiction fan. I remain hopeful that our solar system will be the next great frontier.

Dover Publications has used my geometrical art in their Creative Haven line of coloring books and I've self published a coloring book.

Two of my efforts:

Geoscapes — includes tessellations, polyhedra, spirals and other geometry inspired art.

http://www.amazon.com/Creative-Haven-GeoScapes-Coloring-Books/dp/048649…

Conic Sections and Celestial Mechanics — includes various ways of looking at conic sections an examination of Kepler's laws.

http://www.amazon.com/Conic-Sections-Celestial-Mechanics-Coloring/dp/19…

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Regarding Hop's blog:

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It was Tom Murphy's Why Not Space and Stranded Resources that got my blog started. In various forums Murphy's fans would proclaim "Dr. Murphy has a Ph.D. in physics and he shows space settlement is a fool's errand." I would point out Murphy doesn't patch conics correctly. That there are many asteroids much closer than 5 kilometers/second. As well as rebuttals to other flawed arguments Dr. Murphy tossed out to demonstrate his preconceived notion. For convenience I collected these rebuttals in my first blog post.

And most of the following blog posts look at the same question: Is it doable to settle space? This remains an open question, in my opinion. Is it a goal worth pursuing? Tearing down our prison walls is one of most worthwhile goals our species could pursue.

A few key posts:

http://hopsblog-hop.blogspot.com/2013/12/who-needs-humans.html

Entities like British Petroleum demonstrate we can use robots to build infrastructure in remote places humans can't reach, like the sea floor. Advances in robotics might enable construction of infrastructure on near earth asteroids or lunar poles. Does that eliminate the need for humans? I argue it gives humans a reason to visit. Proximity gives better bandwidth and less light lag latency. Also human maintenance extends a robot's lifetime.

http://hopsblog-hop.blogspot.com/2012/08/mf-is-mofo-tyranny-of-rocket-e…

Big delta V budgets shrink a rocket's dry mass fraction to a tiny shred. We meet this difficult mass fraction by throwing away dry mass enroute. With smaller delta V budgets we could have rockets more robust than egg shells and reuse becomes doable. When we ditch disposable rockets, cost of spaceflight is no longer cost prohibitive. Extra terrestrial propellent sources are a way to break big delta V budgets into smaller chunks. Two possible propellent sources: 1) volatiles in the lunar cold traps 2) hydrated clays in some near earth asteroids.

http://hopsblog-hop.blogspot.com/2015/05/have-your-ion-isp-and-eat-ober…

Ion rockets have great ISP but tiny thrust. With tiny thrust, these rockets can't enjoy much Oberth benefit. But a tether could use an ion engine to build up momentum gradually. When a tether releases a payload, the "burn" is even more sudden than a chemical burn. Also tethers can exchange momentum. Making catches from higher orbits adds orbital momentum while throwing to higher orbits subtracts. By balancing momentum hits with boosts, a tether's orbit might be maintained with little reaction mass.