PdQSat: budget energy and test peak power

PdQSat is a UFMG experimental CubeSat project supported by AEB. Its name refers to pão de queijo, the cheese bread associated with Minas Gerais. UFMG describes planned flight experiments involving a lithium-sulfur battery and a supercapacitor — open definition, alongside training in space engineering. AEB’s 2025 report records completion of preliminary design and continued detailed development, with integration and environmental testing planned for 2026. Those records establish development work, not successful orbital validation.

A technology experiment asks a narrower question than whether every future spacecraft should use the device. It needs to specify the tested unit, load, temperature, measurement method and success criteria. The spacecraft must also remain able to operate and return the experiment’s data. A promising storage technology cannot be judged only by its name or a single headline comparison; the relevant performance depends on the task and test conditions.

Energy is the amount available for work, while power — open definition is the rate at which energy is transferred. A watt is a joule per second. In an original example, an ideal load drawing two watts for thirty minutes uses one watt-hour — open definition, equivalent to 3,600 joules. That calculation ignores conversion losses and other loads so the distinction is clear. It is not a PdQSat battery capacity or an operating specification.

Now imagine a transmitter needing ten watts for six seconds. It uses sixty joules, much less total energy than the half-hour load, but demands a higher delivery rate during that short interval. A storage system can have enough energy and still fail to supply the required peak current or maintain voltage. Batteries and supercapacitors can serve different roles in a design; comparing them requires compatible conditions and both energy and power requirements.

Budget duration and delivery rate

A useful test records voltage, current and temperature over time, identifies the load sequence and states how the device was charged. Repeating a cycle can reveal changes that a single successful pulse misses. Environmental tests can investigate behavior under specified temperatures and pressures, while later flight data would address an actual mission environment. These are complementary steps, and a planned flight experiment should remain a plan until its results are documented.

The accompanying PREFIRE photograph provides a comparison with a different spacecraft’s visible solar arrays. Solar generation and storage are connected but distinct: arrays gather energy in suitable illumination, while storage can supply loads when generation is insufficient. Their visible area alone cannot reveal battery capacity or guaranteed available power. For a final design exercise, list the average loads, short peaks, losses and reserve, then specify the measurements needed to verify each part of the energy budget.