A Drake Equation for Alien Artifacts

“I propose a version of the Drake Equation for Lurkers on near-Earth objects. By using it, one can compare a Search for Extraterrestrial Artifacts (SETA) strategy of exploring for artifacts to the conventional listening-to-stars SETI strategy, which has thus far found no artificial signals of technological origin. In contrast, SETA offers a new perspective, a new opportunity: discovering past and present visits to the near-Earth vicinity by ET space probes.”

—Paul Gilster, “A Drake Equation for Alien Artifacts.” Centauri-Dreams.org. April 20, 2021.

Imagine an alien civilization finding the Voyager space probes a billion years in the future. Over the span of cosmic time, how many other civilizations managed the same? What is the typical civilizational life span of those civilizations capable of doing it?

Then, there is the question of how many would have survived and developed far enough to place probes in nearby stars with environments conducive to life?

The Space Resource Report: 2020

China dominates. Asteroid mining dies but attends its own funeral. Reusable rockets lower the cost and increase access to space. The Moon, Mars, and asteroids all get new survey maps for water resources. Water-based thrusters perform well in orbit. Asteroids are blasted and samples collected. Space mining gets more legal scaffolding. The Moon gets one new rover and two new craters.

The aim of this document is to highlight the major developments surrounding space resources in 2019, with an eye towards following these developments through 2020 and beyond. Let’s get down to the science, business, policy, and real technology developments that will invigorate humanity’s expansion into space.

-David Rich, Joshua Schertz and Adam Hugo, “The Space Resource Report: 2020.” spaceresource.com. Janurary 24, 2020.

Fairly comprehensive overview. Worth checking out if you have any interest in this topic.

Aerospike Engines

“[A rocket engine] is a heat and pressure machine whose end goal is to convert…heat and pressure into workable thrust. The more that gets converted the better. This conversion is usually done by a large bell nozzle…

The further down the nozzle you go, the lower the pressure and temperature of the exhaust gets and the more it’s exchanged for higher and higher exhaust velocities. So in general, you want this nozzle to be as big as possible in order for it to convert as much of that energy as possible. 

Only one problem. When the exhaust pressure at the end of the nozzle gets below the pressure of the outside ambient air surrounding, the ambient air actually starts to squeeze in on the exhaust gas. Lower the pressure too much and the ambient air will squeeze in on the exhaust so much that it will actually start to peel the exhaust off the nozzle walls and form random shock waves and spikes that will tear apart the engine. So what if you turned an engine inside out and made it so the ambient air pressure is actually pushing the exhaust IN against the nozzle instead of squeezing the exhaust away from the nozzle.”

—Tim Dodd, “Are Aerospike Engines Better than Traditional Rocket Engines?” Everyday Astronaut. October 18, 2019.

I’d never heard of aerospike engines before. This seems like a good introduction.

NASA Image and Video Library

You can browse NASA’s Image and Video Library online; you can also access it via NASA’s API. Through that interface, you can search by caption, keyword, location, photographer, year created, and other fields; in return, you get structured data on each media file. The library was launched two years ago, bringing together more than 140,000 images, videos, and audio files that had previously been spread across dozens of separate collections.


Peace Privilege

“She describes it as ‘peace privilege,’ approaching the world from a stability that allows for simplifications.

There’s always a lot of denial going on when trauma interrupts our safe outlook on life. We know that people in general don’t want to see horror except in comfortable contexts (like fiction) so seeing human beings systematically torturing, starving and hurting others makes us feel vulnerable, impotent or responsible. It makes us question the comfortable assumptions of our own lives and why have we grown in a safe environment (could it have been by chance?).”

—Manuel Llorens, “‘Peace privilege’ Also Means Disgust for Someone Else’s Suffering.” Caracas Chronicles. May 3, 2019.

And if it is by chance, will the dice roll differently, for me, sometime soon? Fix space and flow across time and we all live in a Caracas, It’s just not Caracas today.

Example: gun control is trying to reduce the systemic risk of individual violence while, at the same time, increasing the systemic risk of organizational and state violence. Are people in Caracas safer when all the guns are in the hands of the colectivos, police and military? What happens when the place you make your home becomes Caracas?