Describe a beamed power solution. ( Digest Number 135)

The 90% was for the conversion of microwaves to electricity at the
rectenna, and didn't include the conversion of electricity to
microwaves at the transmitting antenna. That said, 37% still sounds a
bit low to me.
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61% efficiency at the spacecraft is unacceptably low.

We simply cannot feasibly dissipate that much waste heat.

We must have efficiencies in the 90's for the space segment to be
feasible.
The high 90's.

Otherwise, our only hope would be to look at microwave reflectors rather
than re-transmitters. This doubles the path length, which makes the
geometry even more difficult, the rectenna would have to be double the
diameter.