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Guest: Dr. John Hunter. Topics: Quicklaunch, LLC, hydrogen gas guns, propellant depots, Mars exploration. You are invited to comment, ask questions, and discuss the Space Show program/guest(s) on the Space Show blog, http://thespaceshow.wordpress.com. Comments, questions, and any discussion must be relevant and applicable to Space Show programming. Transcripts of Space Show programs are not permitted without prior written consent from The Space Show (even if for personal use) & are a violation of the Space Show copyright. We welcomed back Dr. John Hunter, co-founder of Quicklaunch, LLC to update us on the progress of his hydrogen gas gun for launching cargo to space, including propellant. Among the goals he talked about were Mars exploration & propellant depot supply. For more information about Quicklaunch, LLC, visit www.quicklaunchinc.com. Dr. Hunter gave us a brief introduction to hydrogen gas guns and Quicklaunch. As you will hear throughout this discussion, lots of numbers and technical terms are used so I recommend you listen to the discussion with pencil and paper in hand if that is possible. As we moved forward in the first segment, we talked about why use hydrogen, the cost of hydrogen as a fuel, and how it is used as a propellant. We talked about using the gas gun for sea launch but also demo shots from White Sands and the role Adak, Alaska will play for going to the ISS. In response to listener Paul, Dr. Hunter said they were hoping for costs under $500/lb. to LEO. Dr. Hunter spoke a lot about big dumb boosters, Space X, Falcon 9, and Falcon Heavy. He was encouraged by the progress being made by Space X and said everyone wins with competing launch programs. Later in the program he thought it might take five more years or so to determine which system is more cost effective, the hydrogen gas gun or a Space X Falcon rocket. Dr. Hunter described the "sweet spot" for cargo at between 100 and 1,000 lbs. Harry asked about the differences in his approach and magnetic rail guns. We talked about the differences, including the need for large amounts of real estate with the magnetic gun. Dr. Hunter then introduced us to the need for downrange safety for these systems. John then mentioned that Quicklaunch now had a Facebook page so for those of you on Facebook, search for Quicklaunch and befriend the company. They will be sending out weekly update reports and will be using Facebook for some of their correspondence. John then talked about impulse launch, & sonic booms over water as compared to land. Marshall asked about escape velocity and the rocket assist. We started the second segment with an email from Charles stating that the gas gun would not work. He said basic physics made it impossible on 3 ground so don't miss what he said: This email produced a detailed back and forth with John and Charles. John urged him to run the numbers and check out http://www.jhuapl.edu/techdigest/td/td2003/gilreath.pdf. Since the show aired, others have contacted me & have been crunching numbers getting similar results to what Charles said. I have encouraged everyone doing this analysis to post their work on the blog. Don't miss the discussion on these issues during this segment. We also talked about drag which our guest said for simplicity was composed of is composed of form drag, skin drag & base drag. I asked Dr. Hunter for his top challenges & he listed two in this segment. John Hunt from Atlanta called in, we talked about the Delta V with the rocket motor, the choice for liquid rather than a solid, and the front loading of the gun. Marshall sent in another note about the work by Gerald Bull. As the program was nearing completion, we talked about the funding for Quicklaunch, conference presentations, and more. If you have comments or questions for Dr. Hunter, post them on the blog URL. If you are using Facebook, befriend the Quicklaunch page. Dr. Hunter's email address is email@example.com.