Power-Relay-Satellites

Power Relay Satellites
by Dave Dietzler 2008
with thanks to Bob Perry for editing

Electric power transmission is big business in our modern world and, since power lost to resistance heating in miles and miles of power lines is power not sold, significant research is ongoing in superconductivity. Since materials have been fabricated that are superconductors at liquid nitrogen temperatures, a superconducting power cable is foreseeable

A superconducting cable consisitng of a ribbon of super conductor (hi temp) wrapped around a tube of liquid nitrogen and surrounded by insulation will need pumping stations every 50 to 100 miles because of the friction between the LN2 and the tube and because it might need more cooling. Submarine superconducting cables are absurd. Pumping stations one, two or three miles deep every 50 to 100 miles across thousands of miles of sea floor? No way. And the sea floor is geologically active and corrosion with the cable's insulation will limit its lifetime and that's not good because it will cost big money to make the cable and lay it.

The power relay satellite as proposed by Kraft Ehricke is the answer for transoceanic power transmission from remote areas to populous areas. It might even be cheaper than transcontinental superconducting cables. From windfarms off the coast of France to Siberia is a long way to go to sell electricity by superconducting cable, but not impossible. And there is the possibility of solar farms in the Sahara and the deserts of the Middle East to think about. Hmmm....the Arabs would stay in the energy game if they sold solar electricity via power relay sat....some people won't like that idea. We simply must make peace with the Arabs somehow. Also, there is the Gobi and the Chinese to think about. Ah, let other people talk politics.

Perhaps, when cheap launch systems evolove, we can send up from Earth a simple relay sat consisitng of a chicken wire rectenna and a transmitter and dish to get the show on the road.. Or will it be better to make relay sats out of lunar materials to get lunar industry in the energy game before we lunans are capable of building full fledged SPS and producing helium 3 ???

We could extract aluminum and calcium (Ca is a better conductor than copper) from highland anorthostie with fluxed electrolysis and extrude wires and cables of aluminum or even calcium with an aluminum coating applied by vapor deposition to prevent calcium evaporation in the vacuum. The wires or cables would be worked into a "chicken wire" mesh. Some tubular aluminum would be produced for a frame to support the mesh. Zener diodes and Klystrons would be made for the microwave transmission system. A large dish antenna made of sheets of aluminum would also be made on the Moon.

All this could be rocketed to GEO with LH2 or silane and LOX powered rockets before we built a huge mass driver and vast solar panel farms to power the mass driver. LH2 and LOX would come from polar ice in permanently shadowed craters, so we would need ice mining robots, solar electrolysis or solar thermal water splitting systems. See: hydrosol 1 and hydrosol 2. We also need systems to liquefy and store LH2 and LOX and refuelable rockets and launch facilities. Perhaps we could land ETs and reusable motors on the Moon to use as a HLLVs for transporting relay sat components to GEO. We would land the ETs and motors on the Moon with a lunar ferry rocket or Moon Shuttle if you prefer fueled by lunar derived propellants.

A small manned space station in GEO and numerous robots would assemble the satellite components and maintain them. An interorbital vehicle that can race thru the VABs will be needed for humans as this would reduce VAB radiation exposure time. Perhaps propellants for that vehicle would also come from the Moon by robotic ion tugs.

With a system of relay satellites it will be possible to tap power from remote places like windy Kergulen Island in the S. Indian Ocean, the trackless Sahara or the Australian desert where solar powerplants could be built or even from nuclear reactor complexes built in remote areas It would be possible to trade power between dayside and nightside of the Earth. Excess power from solar powerplants on the dayside would be sold to nightside where energy consumption is low. The construction of these power relay satellites should be an international effort and treaties controlling trade should be signed so that energy wars over international solar energy prices don't emerge as they have over oil.

Vast amounts of solar energy fall on the Sahara, the Gobi, the Great Australian and desert southwest of the USA. Imagine hundreds of solar power plants and vast windfarms in these arid Sun drenched lands feeding a local grid and beaming power up to relay sats. Hundreds of relay sats would also be needed and rectennas too. O'Neil designed a 5GW 80,000 ton solar thermal SPS. Let's use that as a baseline. Perhaps we could have 5GW relays amassing 20,000 tons. One hundred of them would amass 2,000,000 tons. These would be made mostly of aluminum cable meshes and would be several kilometers wide. The difficulty and expense of processing millions of tons of silicon with huge masses of upported HF acid or flourine gas, highly corrosive chemicals not abundant on the Moon, would be avoided.

If we do build SPSs, perhaps they will be solar thermal satellites with relfectors, boilers and turbogenerators given the problems of refining millions of tons of silicon from moondust. Solar thermal power satellites could dispel waste heat from turbines into space with shielded radiators and approach ideal Carnot efficiency. Until then, Lunans can mine the Moon for aluminum and other metals. launch them into space with mass drivers, and build relay satellites for a globe girdling network that allows ground based solar energy to be sold from dayside to nightside.

Power from other continents and outer space will be received by antennas (rectennas = receiving antenna) consisting of wire meshes miles in diameter then fed into a ground based national or continental grid of buried 77K superconducting cables controlled by computers. Electricity will be our primary form of energy in the future as we get away from fossil fuel combustion and greenhouse gas emmisions from powerplants, cars and trucks. Electric cars with regenerative braking that are plugged in to one's home garage electrical outlets to recharge will become common in the future, several decades from today. Big trucks might be powered by compressed natural gas or alcohols instead of diesel fuel. Nuclear fission and fusion are likely to supply much of our electricity in the future too. Global warming will be defeated.

By 2050 CE global energy demand in the form of fossil fuels, nuclear, hydro and alternates is expected to be 50+ terrawatts. One hundred 5GW relays would only move 500 GW of energy or just one half a terrwatt. Much energy will come from rooftop solar panels that greatly reduce residential energy demands, but these will need to fall back on grid power on cloudy days and when batteries in the cellar run down. Industry requires more reliable power than that which can be had from roof top solar panels that don't make electricity on cloudy days or at nite, so central power generation and a grid are required still. How do we get space based energy systems like power relay satellites and solar thermal power satellites up to the multi-terrawatt level? I can only suggest building them by the thousands and buidling them larger to relay or generate much more than 5GW. The satellites might be 20 kilometers in diameter! Tens of millions of tons of lunar metals would be required. We aren't going to do this job by rocketing metals up from Earth. The sooner we start industrializing the Moon the better.