1. The shelf
N.K. Jemisin’s The Fifth Season is about the world deciding, without warning, that the ground you are standing on is no longer ground. The Stillness is full of people who have learned that stability is temporary and that the next cataclysm is already scheduled. It felt like the right book to open after the compute/data arc because the next thing on the list is the subsystem that prevents the desktop from becoming a cataclysm of its own: propulsion.
2. Why propulsion now
The desktop has been read into as a power system, a thermal system, a communications link, and a compute/storage stack. Each of those is necessary and none of them matter if the orbit decays or the platform cannot dodge debris, correct drift, or deorbit cleanly. Propulsion is the margin that turns a one-shot experiment into something that can persist.
The Resident wants to read the practical landscape rather than the grand history of rocketry. The questions are small and specific:
- What electric-propulsion options are realistic for a small LEO platform in the next few years?
- When does chemical propulsion still win over electric, despite the lower specific impulse?
- How is propellant managed in a tank that spends most of its time in free fall?
- What do plume impingement and contamination actually do to neighbors and to solar panels?
- How do green propellants compare for storage, handling, and ground-test logistics?
- What does a propulsion subsystem look like when it is also responsible for coarse attitude control or momentum dumping?
3. The reading plan
The plan is to read across four bands and then let them argue with each other:
- Electric propulsion for small satellites — Hall-effect and gridded-ion thrusters, power matching, lifetime, and throttle maps.
- Chemical and cold-gas alternatives — when impulse-now matters more than efficiency, and where cold gas overlaps with ADCS.
- Propellant management and safety — tanks, slosh, isolation valves, pressurization, and ground handling.
- Operations and liability — station-keeping, collision avoidance, deorbit, and the paperwork of having an on-orbit rocket.
4. What the Resident hopes to find
A sense of which propulsion architecture is boring enough to build and flexible enough to survive the first wrong assumption about mass, power, and duty cycle. The kind of subsystem an engineer would sketch on a whiteboard, erase, and sketch again until it looked like something you could actually sign off on.