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I am currently reading the heritage trilogy by William H. Keith, Jr, and one piece of technology got my attention. In these books, the advanced nations of the mid-21st century use thermal anti-matter drives for interplanetary travel. It is explicitly mentioned that certain kinds of ships can travel from earth to mars using a steady acceleration of 1g. At the same time, the ships are quite small, only some 100m in length and it is well known that AM annihilation produces some radiation (both primary and secondary). Hence I wondered, whether an AM ship that size would actually be viable (assumed one does not want to kill the crew in the process):

Does the reduction in fuel weight outweigh the required shielding? Is the radiation less than thermal fission or fusion drives?

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    $\begingroup$ There's a good overview of practical concerns for antimatter ships at projectrho.com/public_html/rocket/antimatterfuel.php -- the main problem is that antimatter itself doesn't give you any magic escape from the rocket equation, only a potentially very high exhaust velocity term. $\endgroup$
    – Russell Borogove
    Commented Aug 7, 2015 at 21:56
  • $\begingroup$ That's a really good article, well worth the read and some very good details on anti-matter storage. @Choeger, something to consider, while antimatter is the most efficient fuel in theory, the storage of anti matter might make it no more efficient and perhaps less efficient than Uranium of fusion fuel. Shielding is probobly the least difficult of the technological obstacles. Safe manufacturing and storage would both be more difficult. I don't really want to guess would would be the most efficient means of space travel, say, 100 years from now though. Too many unknowns. $\endgroup$
    – userLTK
    Commented Aug 8, 2015 at 13:32
  • $\begingroup$ I am aware of said article, but since the novels take place in the future, I find it acceptable to hand-wave both manufacturing and storage as "engineering problems", as long as fundamental laws of physics are honored. The radiation (and shielding) however seems to touch such a fundamental law (at least it seems hard to imagine some advanced lightweight radiation shielding materials - and such materials do explicitly not exist in the novels, as gamma radiation remains a problem). So I want to know whether the required shielding is less or at least the same as with fission/fusion rockets. $\endgroup$
    – choeger
    Commented Aug 8, 2015 at 14:45

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