Value chain · CLM-0204
In plain terms
In this 1978 design, heat from the power-conversion tubes, not the RF electronics themselves, set the top limit on how much power the transmitting antenna could handle per square metre.
The claim as recorded
In the 1978 US DOE/NASA reference 5 GW satellite power system design, the transmit antenna's power capability was set by a thermal limit of 22 kW/m2 at the center of the array, arising from waste heat generated by the DC-to-RF power conversion tubes; this limit, combined with an ionospheric power-density limit, sized the array at 1 km diameter for about 5 GW of DC power delivered on the ground per antenna.
Scope and limits
This is a 1978 ASSUMED point-design engineering limit, not a measured achieved flux from any built or flown hardware. It bounds the transmit array only, not the collector array or ground segment. The report gives the cause as tube waste heat but prints the value as RF power density at the array centre, "22 kw/m2rf" (PDF p.281); read as converter waste heat at the report's 0.85 conversion efficiency, the same design point is about 3.9 kW/m2 (CLM-0891).
What it assumes
The reference design's specific klystron-based DC-to-RF conversion technology and its assumed thermal-rejection hardware (see CLM-0205); no allowance for later, more efficient amplifier technologies is included.
Where it comes from
"The power capability of the SPS system was sized by: (1) thermal limitations of 22 kW/m2 in the transmit array due to waste heat from the DC to RF power converter tubes; (2) a peak power density limitation in the ionosphere of 23 mW/cm2" (SRC-085, PDF page 37). Corroborated on PDF page 281: "The thermal loading in the center of the array (22 kw/m2rf) permits a design for a 1 km diameter array which provides roughly 5 GW of dc power on the ground per antenna."
Basis: kW/m2 of RF power density at the center of the microwave transmit array, which the report calls its thermal limit and attributes to DC-to-RF converter tube waste heat; reference 5 GW photovoltaic point design
Related records
- Answers question
- QST-002 not published in this release
Cite this
energyaperture.com/c/clm-0204
CLM-0204, Energy Aperture, as of 1978.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-085
- CLM-0013The paper that modern UK studies rely on for the beam figure calls anything below 1 kilowatt per square metre safe, with 230 watts per...CLM-0020The original 1978 design set the beam at 230 watts per square metre in the middle of the receiving site, about one twenty-third of that at...CLM-0023In the 1978 reference design, two limits set the size of the transmitter and the receiving site: how much heat the transmitter can shed...CLM-0039The 1978 report set the figure to protect radio and navigation systems from a disturbed ionosphere, called the number theoretical and...CLM-0045The apparent conflict between 12 and 23 was not an error. The underlying study gave a range, and the figure adopted sits near the top of it.CLM-0101The 1978 contract required the researchers to report fixes if ionospheric disturbance pushed the pilot-beam phase error past 2 to 3...CLM-0137In four major space solar power studies from 1978 to 2007, none put a number on how much of the beam's energy would be lost if the beam...CLM-0138The original 1978 government design for beaming power down from space adds up all the expected energy losses to get 63% overall efficiency...More on the source page.
- Contradicted by
- CLM-1057The safety study's own picture of the system: about $13 billion of hardware per satellite in 1978 money, 640 people in orbit for six months...