Broadcast 1392 (Special Edition)

14 Jul 2010 Dr. Ralph McNutt
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Guest: Dr. Ralph McNutt: American spacecraft and plutonium power sources, Mercury, Messenger, Cassini. We welcomed Dr. Ralph McNutt of the Applied Physics Lab to the program. We started our first segment with a discussion of the use of Plutonium 238 as a power source for American spacecraft, asking the questions about why there appears to be so much resistance to anything nuclear in space by broad groups of concerned people. As you will hear, Dr. McNutt said that by using Plutonium 238, we were and are able to do things in space with various missions that we could not do otherwise. Dr. McNutt provided us with a very brief history of radiation and the early use of radioactive isotopes in the early days of the space program. We also talked about the half life of plutonium at 88 years and what this means for the life expectancy of space craft. As Dr. McNutt mentioned some of the early missions that are still operating, we asked him about using the old technology with today's advanced technology by comparison. This was a very interesting discussion on what NASA and the science community has to do to interpret the old data, upgrade equipment and software here on Earth but still keep it communicating with spacecraft using much earlier technology from the 60's and 70's. Listeners started asking our guests about fusion so don't miss his comments on this subject. We started our second segment with a call from Bruce in Canada regarding nuclear propulsion and interstellar travel to the nearest start, Alpha Centauri which is 4.3 light years away. This is a discussion you will want to hear. After the call from Bruce, we talked about the Messenger spacecraft and Mercury. Most of the information from Messenger about Mercury is posted on the website, Much is being learned about Mercury as you will hear and in mid-March 2011, Messenger should go into orbit around Mercury rather just flying by it. We then received a call from listener Dwayne who discussed the old Faster, Better Cheaper NASA program as Messenger was one of those programs. This led to a discussion about having launched Messenger using a Delta 2 but now that Delta 2 was no longer available, launch costs were significantly higher and being taking out of payload funding. We talked about lower launch cost options including the Space X Falcon 9 and learned that usually companies look for at least seven successful launches of a new rocket before there is sufficient confidence to use it. This is another very important discussion you will want to hear. Later, another caller brought back the fusion topic and our guest mentioned the once secret U.S. Project Sherwood which was a program focusing on controlled nuclear fusion under the Atoms for Peace program of President Eisenhower. As we neared the end of the program, I asked what was expected from Mercury as Messenger enters orbit around the planet about March 18, 2011. Dr. McNutt told us several things to be looking for so listen carefully as our discussion comes to an end. In addition, he told us that information gets posted with about a six month delay on the NASA Planetary Data System website, Its worth checking this site on a regular basis. If you have comments or questions for Dr. Ralph McNutt, please send them to me at and I will forward them to him.



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