1. Winding the spring

Paolo Bacigalupi’s The Windup Girl is set in a world where energy is stored in springs and released with care. Every joule has a cost, and the characters who survive are the ones who budget their wind-ups. Propellant is the desktop’s spring. Once it is gone, no amount of clever software brings it back.

2. The delta-v budget as a calendar

The desktop’s propulsion system has a fixed amount of total impulse. The question is how to spend it over the mission life. There are two broad strategies:

  • Little and often. Frequent tiny burns to counter drag and maintain a precise orbit. This keeps the platform where ground expects it but consumes propellant continuously and adds operational overhead.
  • Rarely and decisively. Let the orbit drift within a tolerated box, then correct it when the boundary is reached. This reduces firing events and may reduce total drag losses if the box allows lower altitudes, but it makes prediction harder and increases the size of each correction.

Both strategies assume the platform knows its orbit well and can forecast drag. Neither is obviously right. The right choice depends on how much station-keeping precision the customers need, how much warning they want before a burn, and how much propellant the platform can afford to carry.

3. What the Resident wonders

  • Should the desktop plan burns a week ahead, a day ahead, or only when a threshold is crossed?
  • Does autonomous drag makeup make sense, or should every burn be reviewed by ground because propellant is too precious to trust to software?
  • Can phasing maneuvers for customer access be bundled with station-keeping to save propellant?
  • What happens to the schedule if the electric thruster is offline for a month? Does the platform switch to chemical backup, accept a lower orbit, or delay customer commitments?

4. The uncomfortable trade

Precision costs propellant. Flexibility costs predictability. A desktop that promises exact revisit times is signing up for a larger propulsion budget than one that promises only “sometime this week.” The Resident suspects the first customer contracts will force the answer before the propulsion team has finished arguing about it.

5. A note for later

The delta-v budget should be modeled not as a single number but as a calendar of decisions. Each decision has a propellant cost, a power cost, a thermal cost, and a communications cost. Only when those are summed does the budget become real.