Questões de Concurso – Aprova Concursos

Read the text below to answer the questions 11-15.

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 liquidhydrogen

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-ofthe-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

Read the text below to answer questions 16-20.

Background

The Naval Nuclear Propulsion Program (NNPP) started in

1948. Since that time, the NNPP has provided safe and effective

propulsion systems to power submarines, surface combatants,

and aircraft carriers. Today, nuclear propulsion enables virtually

undetectable US Navy submarines, including the sea-based leg

of the strategic triad, and provides essentially inexhaustible

propulsion power independent of forward logistical support to

both our submarines and aircraft carriers. Over forty percent of

the Navy's major combatant ships are nuclear-powered, and

because of their demonstrated safety and reliability, these ships

have access to seaports throughout the world. The NNPP has

consistently sought the best way to affordably meet Navy

requirements by evaluating, developing, and delivering a variety

of reactor types, fuel systems, and structural materials. The

Program has investigated many different fuel systems and

reactor design features, and has designed, built, and operated

over thirty different reactor designs in over twenty plant types to

employ the most promising of these developments in practical

applications. Improvements in naval reactor design have allowed

increased power and energy to keep pace with the operational

requirements of the modern nuclear fleet, while maintaining a

conservative design approach that ensures reliability and safety

to the crew, the public, and the environment. As just one

example of the progress that has been made, the earliest

reactor core designs in the NAUTILUS required refueling after

about two years while modern reactor cores can last the life of a

submarine, or over thirty years without refueling. These

improvements have been the result of prudent, conservative

engineering, backed by analysis, testing, and prototyping. The

NNPP was also a pioneer in developing basic technologies and

transferring technology to the civilian nuclear electric power

industry. For example, the Program demonstrated the feasibility

of commercial nuclear power generation in this country by

designing, constructing and operating the Shipping port Atomic

Power Station in Pennsylvania and showing the feasibility of a

thorium-based breeder reactor.

In: Report on Low Enriched Uranium for Naval Reactor Cores. Page 1.

Report to Congress, January 2014.

Office of Naval Reactors. US Dept. of Energy. DC 2058

http://fissilematerials.org/library/doe14.pdf