VC02 Satellite power management and distribution
Depth of coverage
At its target depth of L3. What the depth levels mean.
What this layer covers
DC bus, conversion, cabling, protection, harness mass, on-board storage
Where it ends
Ends at the DC input terminals of the transmit chain
Deep area
This layer is studied in more depth than most. It belongs to the deep area Power electronics and ground segment.
Power distribution: where it stands
Power distribution carries electricity from the solar cells to the transmitter. No tested hardware appears in these records: three describe one 1978 US design for a 5 GW satellite, and one a 2025 Chinese design. The 1978 design planned to carry power at 40 kV DC, but its own report said the 40 to 50 kV switchgear and cable insulation still needed development (CLM-0210). In that design, power distribution and control hardware was about 19.2 per cent of the 30.47 million kg dry mass (CLM-0212). A 12.186 MWh nickel-hydrogen battery would serve only the heaters of the klystrons, the microwave power tubes, during eclipse, when the Earth shades the satellite (CLM-0211). The Chinese 1 GW design uses a 5 kV main power bus. Its masses add up to its stated total, and its 12.3 per cent efficiency is a design target (CLM-0692).
Scope. Power from the solar array must reach the transmitter. That takes a main power line (the bus), voltage conversion, cables, switchgear (switches and breakers that connect and protect circuits), the harness (the cabling) and any on-board battery. It ends where the transmitter's own equipment begins.
What is settled. No tested hardware appears in these records. The sources describe two designs on paper: a 1978 US design for a 5 GW satellite (CLM-0210), and a 2025 Chinese design for 1 GW (CLM-0692).
The 1978 design planned to carry power at 40 kV (40,000 volts) direct current (DC). Its authors chose this over alternating current (AC) because it would save mass in the conductors and in the conditioning equipment, which converts and regulates the power. The same report lists 40 to 50 kV DC switchgear and cable insulation as items that still needed development (CLM-0210). Power distribution and control hardware was estimated at 5.863 million kg. That is about 19.2 per cent of the 30.47 million kg dry mass (mass without propellant), before the 25 per cent growth margin (an allowance for mass added as a design matures) used elsewhere in the same table (CLM-0212).
What is uncertain. The two designs differ widely in bus voltage. The 1978 design used 40 kV (CLM-0210). The Chinese design states a 5 kV main bus and 100 rotary joints, which carry power across turning parts of the structure (CLM-0692). The Chinese paper gives a reason for the lower voltage: the design is made of 50 modules, and each sends its power only about 310 metres (CLM-0888).
The Chinese design's four subsystem masses sum to its stated 9,160 t, including 1,360 t for power transmission and management (CLM-0692). Each of its 50 modules sends 48 MW down its cables to an antenna subpanel, which radiates 32 MW as microwaves (CLM-0888).
The 1978 design's battery stores 12.186 MWh in nickel-hydrogen cells. Its only job is to supply the heaters of the klystrons, the microwave power tubes, for up to 2 hours during eclipse, when the Earth shades the satellite. It is not a store for the main power, and it is not a storage requirement for space solar power in general (CLM-0211).
What is missing. No breakdown of switchgear, harness or converter mass for a current concept appears in these records. The 2025 Chinese design's summary table gives only a 1,360 t total for power transmission and management (CLM-0692). The 1978 report said high-voltage DC switchgear and cable insulation still needed development (CLM-0210). Nothing in these records says whether they have since been developed or tested in space. Useful sources would be a component test report for high-voltage DC switchgear, or a power-system mass breakdown from a current design team.
Read next. Efficiency of power beaming at range. Which assumption drives the cost spread. From direct current to beam, for the transmitter that receives this power. Getting rid of the waste heat, for the heat that power conversion makes.
Records
13 of the 16 records tagged to this layer are published. The rest are not yet published. A record is published only after a second reader has checked it and it has passed every publication check. What the gate checks.
| Record | In plain language | Tier | Confidence |
|---|---|---|---|
| CLM-0210 | A 1978 US government design for a solar power satellite planned to move its power around at 40,000 volts DC because it judged that this would save weight compared with AC, but the same report lists the high-voltage DC switches and cable insulation needed to do this as still to be developed. | T3 | HIGH |
| CLM-0211 | The 1978 design includes a small backup battery, but its only job is to keep the microwave tubes' heaters warm during the brief periods each year when the Earth blocks the sun from the satellite. It is not a battery for storing the satellite's main power output. | T3 | HIGH |
| CLM-0212 | In the 1978 design, the equipment that moves and controls electrical power on board makes up about one fifth of the satellite's total dry weight. | T3 | HIGH |
| CLM-0539 | A UK consultancy, working for the European Space Agency and using the same design as its reference point, actually published a full weight breakdown -- something the original 2019 paper never did. It comes out lower than the headline claim, at about 0.70 kilowatts per kilogram rather than 1, even though it leaves out several categories of weight altogether. It also rates one of the satellite's power-conversion stages as barely more than an idea on paper, and its input notes say the lightest case for the radio equipment is an expert's judgement, not something anyone has measured or built. | T4 | MED |
| CLM-0692 | The Chinese design's own summary table adds up: the parts weigh what the total says they weigh. Its claimed 12.3 per cent efficiency is sunlight-to-grid, which checks out against the area of the panels and the strength of sunlight in space. The antenna is a long thin strip, 100 metres by 10.5 kilometres, at 5.8 gigahertz. | T2 | HIGH |
| CLM-0879 | The only two full satellite designs here that say what voltage they run at disagree eight-fold, and the newer, smaller one runs at the lower voltage. The newer design's paper says its modular layout keeps the cables short, about 310 metres, and that this allows the lower voltage. | T3 | MED |
| CLM-0880 | The Chinese design runs its solar panels at about 500 volts and steps up to a 5,000 volt main bus. It is the only modern satellite power distribution architecture recorded here. | T2 | MED |
| CLM-0881 | Above roughly 55 volts, a spacecraft power system in low orbit can charge enough to arc and damage itself. NASA has a design standard for it, and the standard says the exact thresholds are not well known and have to be tested for. | T3 | HIGH |
| CLM-0882 | For low Earth orbit NASA gives a voltage above which a power system may arc. For geostationary orbit it gives no equivalent voltage at all - the limits are set on how many electrons accumulate in a material and how strong the electric field inside it gets. The two orbits are not constrained in the same terms. | T3 | HIGH |
| CLM-0883 | NASA puts the level at which internal charging starts causing failures at twenty billion electrons per square centimetre over ten hours, and designs to half that. It says no safety margin beyond that is specified. | T3 | MED |
| CLM-0888 | Cable mass rises with the square of distance and falls with the square of voltage. The Chinese design says it can use a low five thousand volts because it is built as fifty modules, each sending its power only about 310 metres. The 1978 design sends all five gigawatts across the satellite as one system, and its report says it chose forty thousand volts to save conductor and equipment mass. | T0 | MED |
| CLM-0895 | Twice a year, for about six weeks around each equinox, a satellite in geostationary orbit passes through the Earth's shadow once a night, for up to about seventy minutes. Keeping two gigawatts flowing through that would need roughly two and a third gigawatt-hours of batteries. The 1978 design carried about a two-hundredth of that, and only to keep its transmitter tubes warm. Over a year the shadow costs about one per cent of the time. | T0 | HIGH |
| CLM-0923 | The 2001 committee says a solar power satellite several square kilometres across would need tens to hundreds of kilometres of cable in total, and that cable mass is one of the costs of using less efficient cells. | T3 | MED |