Re: starship-design: Genuine STR question

[Steve VanDevender <stevev@efn.org>]

Get a copy of _Spacetime Physics_ and read the later chapters on
relativistic kinematics (chapters 7 and 8, if I recall
correctly).

Energy is mass.  Mass is energy.  A field has mass; if you charge
the field by converting 1 kg of mass to energy in the field, the
field has 1 kg of mass in it, with all the properties that
entails.

Using fields as structural elements in a ship may take a lot less 
mass than using plain old matter, but they will still have mass.

The reason I say that any battery you use to power a starship
must be heavy is that to get the starship to relativistic speeds, 
it takes an amount of energy roughly equal to mass of the
starship (the faster you go, the more you need).  You can't
"hide" that energy in such a way as to eliminate that excess fuel 
mass.