Space power and solar arrays

This category covers solar cells and arrays, deployment mechanisms, power conditioning and distribution units and batteries for spacecraft. The bus that carries them is a separate guide, and the launch that delivers them is another. The buyer here is sizing a power system against a mission, and the discipline is in being precise about the conditions behind every number.

Beginning of life is a sales figure

Ask for power at end of life, at the mission's worst-case sun angle and temperature, after the radiation environment of your orbit and duration. Ask what degradation model was used and what the assumed fluence was. Ask for cell efficiency, packing factor, and the array's mass and stowed volume, and ask which of those was optimised at the expense of the others. Ask what the deployment mechanism is, how many deployments have flown, and what the single point failures are in it. Ask what the array does under partial shadowing and during eclipse transitions, and what the string architecture is when a string fails. For the electronics, ask about radiation tolerance of the power conditioning and distribution, and ask for test data rather than a family claim.

The evidence a serious supplier already has

NASA publishes its technical standards openly, so the workmanship and process documents a supplier says it works to can be read rather than assumed.¹ For parts, the NASA Electronic Parts and Packaging Program publishes technical knowledge and recommendations about electronic parts, and hosts the Goddard radiation test database and its publication lookup, which is where a buyer can check what has actually been tested.² Ask which parts grade the bill of materials is built to, ask for the radiation test reports on the specific part types and lots, and ask what the derating policy is. Ask for the qualification test matrix: thermal cycling in vacuum, deployment at temperature extremes, vibration and shock, and how many cycles were run relative to your mission life.

Export classification comes before the technical exchange

Spacecraft and their specially designed parts are enumerated on the munitions list by capability, and the list points onward to the commerce control list for items it does not describe.³ The Bureau of Industry and Security publishes the export regulations, classification tools, country guidance and the Consolidated Screening List.⁴ Ask for the classification of the exact article, who determined it and on what basis, before the first detailed technical exchange with a foreign supplier or customer.

Schedule is a materials problem

Ask what the lead time is on cells, on coverglass and on the interconnects, and when it was last quoted rather than last published. Ask what the supplier's throughput is in square metres per month and how much of it is already committed. Ask what happens to your delivery if a cell lot fails qualification, and who carries that risk in the contract.

Questions that sort suppliers

Ask for end of life power with the assumptions written down. Ask for radiation test reports on the actual parts. Ask for the deployment mechanism's flight heritage, by mission. Ask what the longest lead item is and what it is doing today.