Broadcast 3576 Dr. Les Johnson

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  • The Space Foundation Conference

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The Space Foundation Conference

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Guest:  Dr. Les Johnson; Topics:  Solar sail propulsion and missions plus his science fiction and his new edited book "Stellaris: People of the Stars" which speculates as to what humans will be like when we go to the stars. 

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We welcomed Dr. Les Johnson back to the program to discuss solar sail propulsion, missions, and in science fiction.  In addition,  Les told us about his new edited book, "Stellaris: People of the Stars which draws upon both science fiction authors and scientists to speculate on what humans will be like and the changes we might have to make to fly to the stars which is just out in paperback.  We started the nearly 90 minute discussion with Les talking about solar sails which lasted about half the program.  A quick way to summarize a few of the key points made by our guest and in response to listener calls and questions is to follow the tags/key words.  Thus, as I have done before, I am repeating the tags and key words here in the body of this summary.

Tags/Key Words:  solar sail propulsion, Near-Earth Asteroid Scout, Solar Cruiser, interstellar flight, interstellar propulsion, private sector new technology development, human spaceflight solar sail propulsion, light reflection, sail material, lightweight reflector, low mass, solar orbit over the poles, dust grains and the solar sail, solar sail development at Marshall and Langley, solar sail "tacking" in space, light thrust on the solar sail, interstellar research, fusion, Breakthrough Propulsion, laser propulsion, solar winds, lack of consistency, Carrington Effect, solar wind charged particles, propulsion through sunlight, electric solar system, solar sail and protons/electrons, effective distance from the sun for solar sail, Jupiter as the useful limit, solar sail costs, solar sail to Venus, solar sails in science fiction, "Mission to Methone," solar sail thrust mass ratios, exoplanets, interstellar flight long timelines, Mars, is spaceflight to the stars inevitable, "", "Space: It's cold. It's boring. It's not our concern" by Bonnie Kristian, cultural & physical changes for long term human spaceflight, human modification for spaceflight & settlement, "Stellaris: People of the Stars," what humans will be like in long term spaceflight, civil liberties in long term spaceflight, space settlement, historical timeline intersections for advanced life occurring at the same time, Venus probes, gravity and orbiting the sun, "Saving Proxima," planetary protection law, "The Andromeda Strain," sample return, human contamination on the celestial body, worth the risk, Radiation Theory

Highlights to the discussion came as a result of listener emails and phone calls plus a few of my own questions.  For instance, early in the discussion, I asked Les why it was taking so long to develop solar sail missions if solar sail propulsion was so great.  Don't miss his response to my question which caused me to ask another question, My subsequent question asked if robust private sector investment and development could reduce the long time for R&D, risk mitigation, plus the other factors cited by our guest when he responded to my initial question.  You will want to hear this entire mini-discussion regarding the private sector with solar sail development.  Another question I liked inquired as to when solar sail propulsion would be applicable to human spaceflight, then later on for interstellar spaceflight.  The interstellar aspect of the discussion expanded into a substantial discussion topic which we addressed throughout the entire discussion.  As for being applicable to human spaceflight, don't count on it anytime soon.

Another listener asked Les if one could "tack" for navigation with a solar sail as in taking on the ocean with a sailing vessel.  The answer was a modified yes but "tacking" in space, while similar to what happens on the ocean, is quite different but with some similarities.  Les explained how one maneuvers the solar sail plus he talked about the solar sail materials, construction, size needed, and the ratios of mass/thrust.  Don't miss his calculations, formulas and explanations.  If you have questions, post them on our blog for this program as I will be letting our guest know about blog posts. 

Other types of propulsion were mentioned such as laser and solar energy against a dark material which would not be the same as reflected light with the solar sail.  In this part of the discussion, we also talked about the cost of solar sail propulsion as compared to other forms of propulsion along with a short discussion on pros and cons plus the materials used to make a solar sail.  Les briefly mentioned fusion along with electric solar systems.  Also discussed was the behavior of  protons and electrons as he explained Radiation Theory. Another listener asked Les for the effective distance from the sun for solar sail missions.  He said Jupiter was the useful limit but he added to that so listen for the rest of the story.  Before moving to Les the author (see we talked with Les about visiting Venus with solar sails.  You will want to hear this discussion as the questions were good, dealt with orbiting the sun and much more. 

As we moved to talking with our guest about his books, I asked about solar sails in the science fiction literature.  Les mentioned a few key examples but said that so far it was not a widespread sci-fi topic.  He then talked about his 2018 book, "Mission to Methone" published by Baen Books.  Les then mentioned his recently released edited book in paperback form, "Stellaris: People of The Stars."  This book is edited with both science fiction and science articles focusing on what humans may be like when we fly to the stars.  Our guest talked about some of the chapters and told us about his favorites.  He mentioned the exoplanets but said it would be unlikely that we find a planet that we can land on it and it will be ideal for humans without our needing to make adjustments to be on the planet.  Don't miss this discussion which later on included Ft. Worth John.  At one point in the discussion he suggested an interstellar timeline was way off in the future, maybe 300 years or more. However, he added that we were moving toward humans going to Mars in the near future. 

Will in Miami sent in a question asking Les if we humans could screw up our opportunities to fly to the stars.  He wanted to know if Les thought it was inevitable that we would go to the stars.  Don't miss all of what Les said in response to Will but he told Will he was optimistic, he thought that someday we would go to the stars but that it was not inevitable.  Don't miss all of this important discussion.  In the context of this particular question, I asked Les if he had read the article in The Week by Bonnie Kristian.  The article, "Space: It's cold. It's boring. It's not our concern" is exactly about what the title says it is about.  Les had read the article as had and he offered us his commentary on the article.  I have also reached out to the author to invite her to be a guest on TSS to discuss her perspective.  You can find the article at

I asked our guest for his favorite articles.  He referenced two of them. After doing so, we took a call from Ft. Worth John.  John started off commenting on earlier comments made by Les about unidentified areal phenomena plus Tic Tac and ET maybe even coming here with advanced technology.  Les did not think it likely, then he talked about two advanced cultures coming into contact with one another at the same time.  Be sure you listen to Les talk about this concept. John and Les talked about the possibility of a government actually keeping this subject secret for decades.  If you want to comment, please do so on our blog.  Les mentioned an old book he said that was particular good on this subject. He was talking about a biography of J Allen Hynek though he did not have the specific book reference available for us. 

Our next discussion topic was space settlement.  Les said that hotels in orbit, tourism, settlement and the like were key to being about to someday go to the stars.  He talked about life support from the ISS, government advances that help the private sector lead the way to space.  He included radiation protection and microgravity mitigation.

Our next caller was Ajay from the Astrox Corp.  He wanted to talk with Les about the possibility of two advanced cultures intersecting at the same time (contrary to what Les said earlier) given how long the time window had been for the universe so far and then how long until the expectation was to  the end of the universe.  This was an interesting conversation so be sure to hear it as it referred to what Les said earlier about time lines even including dinosaurs.  Les did agree with Ajay that he had raised some good issues on the subject. 

In summary, Les provided his contact information and shared with us some of his future book plans.  He then took a last minute question from Todd wanting to know what he thought about planetary protection.  As you will hear, Les had given this topic serious attention.  Listen to what he said about humans contaminating a planet we visit, then compare and contrast that with sample return risks.  While he advocated caution and the need to be careful, listen to his conclusion.  How about posting your thoughts on our blog regarding  his conclusions.

Please post your comments/questions on TSS blog for this show.  You can reach Dr. Les Johnson through me or his website,




A new edited book by our guest "Stellaris:People of the Stars." Featured are "stories and mind-bending speculation" from top space and science leaders around the world.

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22 Sep 2020 Les Johnson
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