SPS & Beamed Energy Propulsion

>
> Right now, and for the foreseeable future, chemical rockets are
the
> cheapest and most reliable way to put any payload in space.
>
> If we wanted to build SPS today then the best launch systems would
> deposable rockets.
>

Doing it that way is prohibitively expensive.

SPS will only become viable if we use exterrestrial resources to
build them, e.g. from the Moon and asteroids. Out there, chemical
rockets are not the only option. And shipping chemical propellants
up from Earth is prohibitive.

Mass drivers have been demonstrated in laboratories, no breakthoughs
are required, it is simply a matter of scaling up the lab prototypes.

Best regards,

Charles R.