Questões de Concursos CETRO

NASA Researchers Studying Advanced Nuclear Rocket Technologies

January 9, 2013

By using an innovative test facility at NASA’s Marshall Space Flight Center in Huntsville, Ala., researchers are able to use non-nuclear materials to simulate nuclear thermal rocket fuels - ones capable of propelling bold new exploration missions to the Red Planet and beyond. The Nuclear Cryogenic Propulsion Stage team is tackling a three-year project to demonstrate the viability of nuclear propulsion system technologies. A nuclear rocket engine uses a nuclear reactor to heat hydrogen to very high temperatures, which expands through a nozzle to generate thrust. Nuclear rocket engines generate higher thrust and are more than twice as efficient as conventional chemical rocket engines.

The team recently used Marshall’s Nuclear Thermal Rocket Element Environmental Simulator, or NTREES, to perform realistic, non-nuclear testing of various materials for nuclear thermal rocket fuel elements. In an actual reactor, the fuel elements would contain uranium, but no radioactive materials are used during the NTREES tests. Among the fuel options are a graphite composite and a “cermet” composite - a blend of ceramics and metals. Both materials were investigated in previous NASA and U.S. Department of Energy research efforts.

Nuclear-powered rocket concepts are not new; the United States conducted studies and significant ground testing from 1955 to 1973 to determine the viability of nuclear propulsion systems, but ceased testing when plans for a crewed Mars mission were deferred.

The NTREES facility is designed to test fuel elements and materials in hot flowing hydrogen, reaching pressures up to 1,000 pounds per square inch and temperatures of nearly 5,000 degrees Fahrenheit - conditions that simulate space-based nuclear propulsion systems to provide baseline data critical to the research team.

“This is vital testing, helping us reduce risks and costs associated with advanced propulsion technologies and ensuring excellent performance and results as we progress toward further system development and testing,” said Mike Houts, project manager for nuclear systems at Marshall.

A first-generation nuclear cryogenic propulsion system could propel human explorers to Mars more efficiently than conventional spacecraft, reducing crews’ exposure to harmful space radiation and other effects of long-term space missions. It could also transport heavy cargo and science payloads. Further development and use of a first-generation nuclear system could also provide the foundation for developing extremely advanced propulsion technologies and systems in the future - ones that could take human crews even farther into the solar system.

Building on previous, successful research and using the NTREES facility, NASA can safely and thoroughly test simulated nuclear fuel elements of various sizes, providing important test data to support the design of a future Nuclear Cryogenic Propulsion Stage. A nuclear cryogenic upper stage - its liquid- hydrogen propellant chilled to super-cold temperatures for launch - would be designed to be safe during all mission phases and would not be started until the spacecraft had reached a safe orbit and was ready to begin its journey to a distant destination. Prior to startup in a safe orbit, the nuclear system would be cold, with no fission products generated from nuclear operations, and with radiation below significant levels.

“The information we gain using this test facility will permit engineers to design rugged, efficient fuel elements and nuclear propulsion systems,” said NASA researcher Bill Emrich, who manages the NTREES facility at Marshall. “It’s our hope that it will enable us to develop a reliable, cost-effective nuclear rocket engine in the not-too-distant future."

The Nuclear Cryogenic Propulsion Stage project is part of the Advanced Exploration Systems program, which is managed by NASA’s Human Exploration and Operations Mission Directorate and includes participation by the U.S. Department of Energy. The program, which focuses on crew safety and mission operations in deep space, seeks to pioneer new approaches for rapidly developing prototype systems, demonstrating key capabilities and validating operational concepts for future vehicle development and human missions beyond Earth orbit.

Marshall researchers are partnering on the project with NASA’s Glenn Research Center in Cleveland, Ohio; NASA’s Johnson Space Center in Houston; Idaho National Laboratory in Idaho Falls; Los Alamos National Laboratory in Los Alamos, N.M.; and Oak Ridge National Laboratory in Oak Ridge, Tenn.

The Marshall Center leads development of the Space Launch System for NASA. The Science & Technology Office at Marshall strives to apply advanced concepts and capabilities to the research, development and management of a broad spectrum of NASA programs, projects and activities that fall at the very intersection of science and exploration, where every discovery and achievement furthers scientific knowledge and understanding, and supports the agency’s ambitious mission to expand humanity’s reach across the solar system. The NTREES test facility is just one of numerous cutting-edge space propulsion and science research facilities housed in the state-of- the-art Propulsion Research & Development Laboratory at Marshall, contributing to development of the Space Launch System and a variety of other NASA programs and missions.

Available in: http://www.nasa.gov

                                     Autoritarismo benigno 

      SÃO PAULO – O título não esconde as intenções da autora: “Contra a Autonomia – Justificando o Paternalismo Coercitivo”. A obra da filósofa Sarah Conly, disponível só em inglês, bate de frente com o virtual consenso de que as escolhas das pessoas devem ser respeitadas. Mas, ao contrário do que se poderia imaginar, não é um texto irremediavelmente autoritário. Embora Conly defenda a proibição do fumo, ela é simpática à legalização da maconha. 
      O ponto central da autora, que pretende refutar os argumentos libertários de John Stuart Mill, é o de que a psicologia reuniu uma catarata de evidências que provam que o ser humano é “intratavelmente irracional” e que isso não pode ser consertado por campanhas educativas. 
      Não é tanto que não saibamos o que queremos. A maioria de nós não tem dúvida de que deseja manter a saúde, guardar dinheiro para a aposentadoria etc.. A questão é que, devido a uma série de vieses cognitivos, fracassamos miseravelmente em seguir uma estratégia para chegar a esses fins. É só sob essas circunstâncias, diz Conly, que o paternalismo deve entrar para dar uma mãozinha. 
      Até aqui eu acompanho os raciocínios da autora. Ela não me convenceu, entretanto, de que o paternalismo coercitivo, isto é, imposto por meio de normas restritivas, é superior ao paternalismo libertário proposto por Richard Thaler e Cass Sunstein, em que o poder público tenta induzir o cidadão a fazer as melhores escolhas, sem, contudo, obrigá-lo a elas. 
      Minha impressão é que Conly não considerou como deveria o problema da informação incompleta que, em alguma medida, afeta todas as éticas consequencialistas. Nós simplesmente não temos como calcular o valor subjetivo que o fumante atribui a suas baforadas para proclamar que elas valem menos que a sua saúde. 
      O livro de Conly é bom e nos faz pensar, mas continuo com Mill: “Sobre si mesmo, o seu corpo e sua mente, o indivíduo é soberano”. 
  
 
SCHWARTSMAN, H. Folha de S. Paulo, São Paulo, p. A2, 17 mar. 2013.