Broadcast 1304 (Special Edition)

The Space Foundation Conference

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Guests: Classroom guest panelist Paul Breed with co-hosts Dr. Livingston, Dr. John Jurist, Dr. Jim Logan. Topics: The Rocket Equation and why it matters. Welcome to Lesson 2 The Rocket Equation in our Space Show Classroom series. This nearly two hour program focused on The Rocket Equation, how to understand it, use it, and why we build and launch rockets the way we do. In the first of two segments, Paul Breed began our discussion using his presentation materials posted on The Space Show Classroom blog, This is a very comprehensive discussion and explanation of the rocket equation and the physics and engineering governing the launching of chemical rockets. Paul and our co-hosts talked at length about the difference between suborbital and orbital, the amount of energetic differences in the two and why going to orbit is 25 times harder than suborbital flight. We talked about fuel, mass rations for the rocket full of fuel and payload as well as the rocket's dry weight mass ratios. We talked about the need to accelerate to a minimum of 17,000 mph and the 1,000 mph boost the rocket gets from launching west to east at the equator which diminishes to only about a 300 mph if you launch from a polar site. The Classroom rocket equation team also described and explained the penalty for launching east to west and used Israel as the example for this type of launch. Comparisons were made to the Saturn V rocket and jets. We talked about why a big rocket has less of a launch penalty than a small rocket, the SSTO was examined so that all of us would understand why it is so difficult and illusive to build. We talked about why wings, landing gear and reusable robustness work against the orbital vehicle but are better for the suborbital vehicles. Air-breathing rocket engines were discussed along with jet engines, and toward the end of this segment, we got into the rocket' equation significance for costs. In our second segment, Paul took us through the rocket characteristics, mass, and costs for the typical Lunar Lander Challenger rocket. Listen carefully to what he says about this and how the rocket equation dictates the scaling up for this type of vehicle to orbital status. Paul said such a vehicle would have a gross takeoff mass of 3,000,000 pounds! Air drag was discussed in both segments of the show but again applied to small rockets in this segment, thus within certain limits, an air launch of a smaller rocket is useful. Paul explained why in his opinion the ramjets, scramjets, and hypersonics don't make sense other than for the military or only for upper atmospheric operation because at best they can only produce about 16% of the needed energy for orbit. But again, for suborbital, its a different story. During this segment, we explained rocket staging. As you will hear, each stage is planned and designed using the rocket equation but builds upon the performance of the preceding stage. Later in this segment, Dr. Logan used the Space Shuttle and the SMEs as an example of mass ratios for payload. We had support on what Jim was saying with a Space Shuttle scientist from Houston who offered many comments and facts regarding the Space Shuttle example. This example dramatically describes what Paul, John, and Jim talked about during this rocket equation program. Near the end of Lesson 2, we discussed possible propulsion and space access from other means that would allow significantly better performance given the rocket equation constraints or even not be subject to the rocket equation including nuclear, the space elevator, fusion, and non-chemical rockets. We also talked about the difference in fantasy and reality and all our participants said that the fantasy while important, does not work for space exploration. Space exploration requires reality and reality is not interchangeable with fantasy. The issue of changing orbits came up, carrying more fuel on an emergency Space Shuttle flight, and why its not practical or doable and even insignificant given the ratios for the shuttle. If you have a comment or question for any of the participants on this Classroom program, please post it on the blog. E-mail addresses for the three co-hosts are listed on the blog. For Paul Breed please use



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08 Feb 2010 Paul Breed, Dr. John Jurist, Dr. David Livingston, Dr. Jim Logan
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  • The Space Foundation Conference

  • The Space Foundation Conference