Thanks Robert for analysing the feasability article. It was beyond me... However some info on radio ... The sun on earth provides about 1kW of power per square metre. Ordinary Solar panels, (I don't know how good NASA's are) are 16% efficient. So thats 160 watts for a square metre. On the moon that constant would be much higher. I could transmit a voice signal to the moon with a 5 watt signal . A directional transmitter antenna takes that 5 watts from a spherical output and projects it in a beam. Effectively multiplying the power of the signal many times. .. Ordinary AM and Short wave transmissions circle the globe by bounce (refraction) off the ionosphere and reflecting again from the earth, making many skips around the globe. Radio Amateurs using only 100 watts input power and standard dipole antenna, in the 20 metre band regularly communicate over long distances. Bouncing a signal off the surface of the moon is another regular means of contact. This is off the moons surface, note, not a special reflector. I share some history: Project "Diana" 1946 was the first attempted and successful echo recieved via moonbounce. using 111.5 Mhz. Developing from that in late 1960 twoway moonbounce communication was achieved on 1296mHz between W1BU near Boston, and W6HB in California, (the Eimac Radio club) I have a photo of the team with their 8 ft dish They maintained communication for four hours. Today regular moon bounce communications are made on the 144 and 2300 MHz amateur bands... Philip.