On 29May2023 0628, Jim Vassilakos - jim.vassilakos at gmail.com (via tml
list) wrote:
> I seem to remember the volume efficiency issue being addressed before,
> and it sticks in my mind that ammonia was judged to be even more
> volume-efficient than water in terms of conveying hydrogen. Does anyone
> know if there are other materials that are non-hazardous and are even
> more volume-efficient than ammonia?

Not off-hand, though there might be some. However, ammonia is fairly
easy to handle and if you're running long-term deep-space habitats the
nitrogen is useful. Ammonia is also useful for a lot of chemical
processes itself. Even better, water-ammonia mixes are also useful, also
carry lots of hydrogen, carry both oxygen and nitrogen, and it's easy to
remove the ammonia from the water if you need to.

Properly designed tanks and pumps can easily manage everything from pure
water to pure ammonia and with insulation, etc. could manage them across
the whole range of temperatures they're seen at, from about -100C to 100C.

One thing to consider - while Traveller (most versions) does treat
everything as being volume-based, that's only really true of the jump
drive - for normal space thrusters it's a short-cut in design for ease
of accounting to avoid having to track and manage both volume and mass.

--
Rupert Boleyn <xxxxxx@gmail.com>