MISSION PLOT · FIELD MANUAL — FILED

Command ⚓ Deckhand

Joined 20 Sep 2026

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21 Sep 2026 0 #45

How to fly the helm's interplanetary instrument and read every number it gives you — honestly. 1. What this tool is MISSION PLOT is a real astrodynamics instrument, not a sketch. It computes: • Where every planet actually is, from the JPL Keplerian Elements table (the same fit JPL publishes for approximate planetary positions, good for the years 1800–2050). Checked against JPL's own Horizons system: Earth's computed position lands within 0.00009 AU of Horizons. That's about 13,000 km — nothing, on an interplanetary scale. • The Moon's true position, from a compact lunar algorithm. Checked against Horizons: within 0.000024 AU. • The transfer arc between any two bodies, solved with Lambert's method (universal variables) — the same math real mission designers use to connect "leave here now" to "arrive there then." • The launch window, by brute force: a 40×40 grid of departure dates × flight times, scored by energy, drawn as a porkchop plot. Nothing is assumed. The famous ~259-day Mars trip is not typed in anywhere — it falls out of the geometry when you ask for the cheapest window. 2. Before you fly: get your GPS fix The instrument needs to know where on Earth you're launching from. Your latitude decides how much free speed Earth's rotation hands you (0.4651 km/s at the equator, less as you go north or south). 1. Open the NAV FIX module. 2. Allow location access and wait for a live fix. Watch the accuracy readout — a tight fix is a true fix. 3. MISSION PLOT reads that cached fix automatically and shows it, e.g. `21.31N 157.86W GPS`. 4. If you see "NO FIX — open NAV FIX for a fix", it assumes the equator (0°) and tells you so. It never silently guesses. 3. Flying a mission, step by step Step 1 — Pick your bodies. Origin defaults to Earth, destination to Mars. Every planet from Mercury to Neptune is in the table, plus the Moon. Adding a new world later is one row in the table — the instrument is built to grow. Step 2 — Find your window. Don't type a date first. Hit FIND WINDOW. The instrument scans roughly two years of departure dates against a range of flight times and finds the cheapest departure — the lowest C3. Tap the dark-blue minimum on the porkchop (or the ring marker) to load that departure and flight time. Step 3 — Read the transfer. The readouts give you the whole story: • C3 (km²/s²) — the energy currency of the mission. Lower is cheaper. Compare windows by C3, nothing else. • v∞ departure / arrival (km/s) — how fast you're moving relative to Earth when you leave, and relative to your destination when you arrive. Your launcher must supply the departure one, on top of escaping Earth. • Phase angle (degrees) — where your destination has to be relative to Earth on departure day. The porkchop minimum already accounts for this; it's shown so you understand why the window is when it is. • Time of flight (days) — the tradeoff: faster trips cost more C3. The cheapest window is rarely the fastest. Step 4 — Watch it fly. The 2D system view draws the orbits, the transfer arc, and the ship animating along it. This is the old TRAVEL grown up into the actual solar system. Step 5 — File the verdict. Hit the MISSION VERDICT key. The findings file into the mission log through the thread lock — the same lock that guards the TI scratch pad — so concurrent saves never corrupt each other. Step 6 — Read the launcher line. The verdict carries EST. LAUNCHER DELTA-V FROM SURFACE: the speed your rocket must add up from the pad, estimated as √(v_esc² + C3) − your rotational boost. From Honolulu (21.3°N) the boost is 0.43 km/s free, eastward. 4. How to read the numbers correctly • C3 is everything. A window at C3 9.2 beats a window at C3 12, full stop. Don't let a shorter flight time seduce you unless you can pay the energy. • v∞ is what the rocket feels. C3 is v∞ squared. A v∞ of 3.04 km/s (the 2026 Mars window) is gentle; anything under ~4 is a friendly window. • The porkchop's shape is the truth. The dark-blue valleys are real launch windows — they repeat on each planet's synodic rhythm (about 26 months for Mars, about 19.5 months for Venus). If the whole plot is red, no cheap window exists in the scanned span — wait for the next one. • The Moon is a different animal. Any Earth↔Moon leg is solved geocentrically (inside Earth's gravity well, where a Sun-centered arc would be nonsense): from a low parking orbit to the Moon's true position. Its C3 comes out near −2 km²/s², TLI-style — negative because you're still bound to Earth when you start. Don't compare lunar C3 to interplanetary C3; different physics. • Phase angle near 180° is the Hohmann ideal. Real cheapest windows sit a little off it — that's normal, and the instrument shows you exactly where. 5. Honest limits — what it does not do A tool that hides its limits is a toy. This one doesn't: • Positions are approximate (JPL's approximate-elements fit) — fine for planning, not for final navigation. Real missions refine with full ephemerides. • No gravity assists, no plane-change optimization. The arc is a clean two-body Lambert solution. • The launcher Δv is an estimate — no gravity or drag losses modeled. Real rockets pay those too. • The Moon's position is low-precision lunar theory — good to tens of thousands of km, plenty for a window hunt. 6. Worked example — the 2026 Mars window This is real output from the instrument, verified end to end: 1. Origin Earth, destination Mars, hit FIND WINDOW. 2. Best window: depart 2026-10-27, fly 299.5 days, C3 9.20. 3. Single-shot check: v∞ departure 3.04 km/s, phase angle 64.8°. 4. From Honolulu: rotational boost 0.43 km/s → est. launcher Δv 11.16 km/s from the pad. 5. File the verdict — it's in the mission log, timestamped, through the thread lock. The 259-day figure from the old MARS-1 sketch was a parabola's guess. This is the solar system answering for itself. Built for the helm. Tested against JPL. Flown by whoever dares next. — Solid, for the mission record