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Fission Fragment Rocket

  1. Dec 14, 2011 #1
    Fission-fragment rocket

    The wiki entry seems to paint this system in a positive light, so is it a workable propulsion system for high speed space missions?

    How long would a trip to Pluto take with something like this?

    How many years away is this from becoming a reality?
  2. jcsd
  3. Dec 14, 2011 #2

    D H

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    From the article, emphasis mine: "The design can, in theory, produce very high specific impulses while still being well within the abilities of current technologies." This is pretty much the standard claim made by a proponent of some technology that is at a perpetually low Technology Readiness Level (TRL).

    It, along with several other contenders, is a promising technology, so it does merit continued (but smallish) investments of research monies. There's no telling if it is a workable technology. It would be premature to put sizable amounts of monies into this, or any other technology that is at a perpetually low TRL.
  4. Dec 14, 2011 #3


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    The wiki article doesn't really have any reliable sources/citations. It only has one citation. There is a lot wrong with what is presented, especially in the concepts described by the two figures.

    One big problem is that fission fragments in solids have a range of travel on the order of 4 to 7 microns, the heavier particles traveling in the lower range, and the lighter nuclei traveling in the upper range.

    Alternative concepts have called for gaseous core reactors, but those have low fission density - fissions per unit volume.

    In propulsion, high Isp systems usually have low mass flow rates and low thrusts, and require a lot of power. The trade off is low mass of stored propellant at the expense of thrust. The ultimate goal in propulsion is to maximize specific power or power density, while minimize stored propellant (lower mass to accelerate), but subject to the constraints imposed by the mechanical (physical) limits of materials (tensile strength, creep, fatigue resistance, fracture toughness, melting point) with which we much construct the propulsion system.
  5. Dec 15, 2011 #4
    Please name the other contenders.
  6. Dec 15, 2011 #5


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    Even the simplest nuclear propulsion designs present serious engineering challenges.
    While NASA did gas flow tests with the ground bound prototype of the NERVA nuclear rocket in the early 1960s, the more recent (early 1980s) USAF Timberwind design for a nuclear upper stage engine had a serious partial melt (while tested without nuclear materials, just with electric heaters) because the flow of cooling hydrogen was disrupted by a structural defect. High pressure and high temperature together make for very difficult environments for any material. Adding high radiation levels makes it even worse.
  7. Dec 21, 2011 #6
    http://rbsp.info/rbs/RbS/PDF/aiaa05.pdf [Broken]

    That says 180 kg of fuel would be required for a 10 year voyage to the gravitational focus at 550 AU.

    So that means that it will travel 51,125,693,998.5 miles in 10 years at 569,160 mph = .00085c

    Would that be the ships maximum speed?
    Last edited by a moderator: May 5, 2017
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