Guest:  Dr. Christopher (Chris) Limbach; Topics:  Combining laser and particle beams for interstellar travel.  Please direct all comments and questions regarding specific Space Show programs & guest(s) to the Space Show blog which is part of archived program on our website, www.thespaceshow.com.  Comments and questions should be relevant to the specific Space Show program. Written Transcripts of Space Show programs are a violation of our copyright and are not permitted without prior written consent, even if for your own use. We do not permit the commercial use of Space Show programs or any part thereof, nor do we permit editing, YouTube clips, or clips placed on other private channels & websites. Space Show programs can be quoted, but the quote must be cited or referenced using the proper citation format. Contact The Space Show for further information. In addition, please remember that your Amazon purchases can help support The Space Show/OGLF. See www.onegiantleapfoundation.org/amazon.htm.

We welcomed Dr. Chris Limbach to the program to discuss his team's project at Texas A&M regarding the combining of both laser and particle beams for use in interstellar travel.  Please see the article and diagram explaining the concept in Texas A&M Today at https://today.tamu.edu/2018/05/11/combining-laser-and-particle-beams-for-interstellar-travel.  During the second segment of the program, Dr. Limbach took us through the diagram on the title page to help us understand how his concept would work.  Note that he said he was basing his concept on already existing physics.

We started our two segment 1 hour 28 minute discussion with our guest explaining the concept to us in the context of doing interstellar flight along the lines of the Breakthrough Starshot project.  Our guest spent significant time explaining the physics to us for both the laser portion of the project and the particle beam.  A big part of this discussion focused on the problem of diffraction and laser beam spreading as the probe went on its journey.  By combining the laser with the particle beam in space, the diffraction is mitigated and controlled.  Don't miss this discussion as it is crucial to the rest of what we talked about with Dr. Limbach

Other questions and items that came up during the first segment including how to increase the speed of the probe as compared to what Breakthrough says they can get with their laser propulsion on swarms of tiny wafers.  In addition, we talked about the ability to slow down the probe or even stop once the destination was reached, say Proxima B for example.  What would be the challenges to be able to do that. Also, I asked how far out from Earth would the propulsion and particle beam continue before the probe was moving on its own toward the destination.  Listeners also had questions.  For example, Linda in Reno wanted to know about humans going to Proxima B and what it would take to have human interstellar flight instead of just propelling 1 gram to 1 kilo of payload.  James in Tucson asked about weaponizing the laser and if that would prevent its use for interstellar propulsion.  I asked about the availability of funding for these types of R&D projects and I was interested in how that might have changed and improved in recent years.  Timelines came up. Here, you might be surprised by what Dr. Limbach had to say so do listen carefully.

Other first segment topics include a discussion on the high energy neutron particle beam.  Nano material fabrication was discussed as was the need for basic research and the question of needing new physics (physics outside the known realm of physics).  Before the first segment ended, Bob in Atlanta asked our guest about the cost benefit analysis for interstellar research and flight.  Be sure to hear how Chris responded to Bob.  Let us know your thoughts by posting on the blog. 

In the second segment, we focused in on the diagram on the Texas A&M Today article referenced at the top of this summary so please refer to it in the following discussion.  I asked our guest to take us through the diagram to explain the details of how his project would work.  I asked lots of questions about what I was seeing in the document and several listeners emailed in too as they found the article online and also asked our guest questions about the diagram.  There was lots of discussion about the nature of the particle beam and the benefits of using one.  Note what was said about the aperture size and the difference in needing only 1 square meter vs. a 1 kilometer were the particle beam not part of the project.  Another listener asked about navigating the probe, making course corrections and even slowing down or stopping as Proxima B was reached.  Listen to what Chris said in response to these questions.  Our guest was asked if repairs could be made along the way were problems detected.  This too prompted a most interesting response from our guest. 

The location of the laser was a big part of our discussion.  As you will hear, locating the laser on Earth, LEO, on the Moon or perhaps someplace else required study, analysis, and lots of planning.  Locating the laser on Earth seemed most plausible at this time but the particle beam would be in space for a variety of technical reasons.  Don't miss this discussion.

A listener asked Chris how he spent his time, wanting to know if the project consumed all his time or only some of his time.  This question provided an opportunity for Chris to talk about his Co-Investigator and student team members.  Speaking of student team members, our guest got an email from a high school student wanting to know the best educational path to take to be able to do the advanced propulsion type work being done by our guest.  Chris had much to say about academic paths, the types of classes to take and the fact that the field was multi-disciplinary so many paths to this type of work existed.   He said a most important factor was for the student to have an ability to continue learning.  He said this was a skill that needed to be developed. 

Before the program ended, Paula asked if the propulsion system being developed by Chris and his team had applications for faster travel within our solar system, perhaps to explore for life on Enceladus, Europa, Titan and maybe even Ceres.  Don't miss what Chris had to say but the short answer was yes.  One final last minute questioner wanted to know if there was drag in interstellar space of if the spacecraft would just keep going as if it had perpetual motion.  Our guest said there was a tiny amount of interstellar material that would produce minimal amounts of drag but this was an extremely small effect.  For the most part, we could consider the probe as continuing to coast through interstellar space.

Please post your comments/questions for Dr. Limbach on TSS blog for this show.  You can reach our gust through me or his Texas A&M faculty page.