I'm trying to decide if there is any meaningful difference between and . They both seem to cover the same thing, namely the fuel of a spacecraft. I suppose fuel is slightly more generic, as it could include reactive mass for ion drives and the like, but I would rather see propellants and , for instance.

A quick survey of indicates that any question for that tag could easily be covered under propellant. The propellant also seems to include questions that could be covered with fuel.


There are fuels that aren't [used as] propellants (RTGs, nuclear reactors,...) or they can have double use (as energy storage and/or as reaction mass, e.g. hydrogen in fuel cells and as fuel part of a bipropellant), and there are propellant components that aren't classified as fuels (e.g. oxidizers).

That said, our current use of them and also description "Questions about reaction mass used for spacecraft propulsion" does suggest we could easily merge into and synonymize with without much (if any) damage.

I would still keep tags and separate (only the latter, together with synonimized with ), and we'd need a new description for it that explains the difference and its suggested use.

  • $\begingroup$ This is technically true, but with 90% of the questions allowing either tag, I don't think there needs to be two separate tags. I think you have convinced me that fuel is the better course for now. $\endgroup$
    – PearsonArtPhoto Mod
    Oct 1 '15 at 17:47
  • $\begingroup$ Also in the propellants-but-not-fuels category would be the xenon used in ion thrusters. $\endgroup$ Oct 1 '15 at 23:06
  • $\begingroup$ You have convinced me that fuel should be the primary tag, but I don't think we have enough of a distinction to separate the two for now. LOX is close enough to a fuel for our purposes, and it otherwise seems to cover everything in the realm of space travel. $\endgroup$
    – PearsonArtPhoto Mod
    Oct 2 '15 at 13:13
  • $\begingroup$ BTW, does Xenon count as fuel in ion engines? $\endgroup$
    – SF.
    Nov 23 '15 at 13:03

I've merged into , and changed 's tag wiki to indicate it can be used for propellant, oxidizer, reactive mass, or any other fuel used in spacecraft or rockets. That should cover all of the bases.


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