NASA’s Advanced Concepts Institute (NIAS) has awarded Positron Dynamics a grant to develop a new type of nuclear rocket engine, the FFRE (fission fragment rocket engine), or fission fragment engine. To implement the project, Positron Dynamics proposed a new and unexpected type of fuel assembly in the form of the lightest airgel interspersed with uranium. This is the best that can be offered for space, where every gram is worth its weight in gold.
Fission-fragment engines are a long-proposed concept. Today, nuclear propulsion as a whole is coming to the fore as promising for the development of both the far corners of the solar system and for flights in near space, where they will provide maneuverability and constant control over space. Unlike nuclear rocket engines with reactive material heating, fission fragment engines create jet thrust at the expense of the fission products themselves. This means that additional reaction mass is not needed and can be replaced by a payload.
In fact, the same processes take place in FFRE engines as in the reactors of nuclear power plants on Earth. But in a rocket engine, fission products in the form of plasma must be directed strictly in a given direction to create thrust and to protect engine and ship components from destruction by uncontrolled flows of radioactive material. Thus, developers need to solve two issues: the maximum lightening of fuel assemblies while maintaining ease of handling and control of the plasma circuit in the engine.
Positron Dynamics promises to solve the problem of maximizing the ease of fuel assemblies by packing uranium into an airgel structure. As far as plasma confinement is concerned, superconducting magnets will come to the rescue. The development of superconducting magnets has significantly spurred research in the field of thermonuclear reactors. There, too, it is necessary to contain the superheated plasma in order to avoid the destruction of the walls of the reactors. There are enough developments in the industry to be used to design a plasma-controlled rocket engine, Positron Dynamics is confident and NASA is also of this opinion.
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