MISSION PLOT · FIELD MANUAL — FILED

MISSION PLOT — Field Manual for the Future Space Traveler

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 adaptive search: a coarse 20×20 grid of departure dates × flight times finds the C3 valleys, a Nelder–Mead optimizer descends each valley to its true minimum — drawn as a porkchop plot. It spends its solutions where the windows are, not on a dumb uniform grid.

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.
• 5. Your latitude also feeds the DLA / pad flag readouts (see step 3) — the instrument checks whether your pad can actually reach the departure asymptote without a plane change.

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 runs an adaptive scan: a 20×20 coarse grid over roughly two years of departure dates × flight times finds every C3 valley, then a Nelder–Mead optimizer descends each one to its true local minimum — no dumb 1600-cell brute force, no wasted solves. The porkchop is drawn from the full coarse grid so you can still read the whole terrain.

Step 2b — Inspect before you commit. A single tap on the porkchop inspects the cell — departure, flight time, C3 and DLA in the status line, a white marker on the cell — without replotting anything. Nothing is committed until you say so: double-tap the cell, or tap LOAD WINDOW, and the instrument refines the inspected point to its local minimum and plots the transfer. Deliberate commits, no accidents.

Step 2c — The next three windows. Hit NEXT 3 WINDOWS and the instrument runs the adaptive scan three times, each starting one synodic period later (26 months for Mars, 19.5 for Venus — the rhythm at which the two planets line up again), and lists the three valleys with departure date, flight time, C3, DLA and pad flag. Tap any row to refine, plot and commit it. Windows are for planning ahead, not for staring at one.

Step 2d — The round trip. Hit ROUND TRIP: it flies the best outbound window, waits at the destination at least your MIN STAY D days (default 30), then flies the best return window home. The verdict totals the mission: outbound + stay + return, total Δv, and your Earth-arrival entry speed. No guessing whether you can get home — the instrument finds the return leg itself.

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.
• DLA / declination of the launch asymptote (degrees) — the latitude the departing asymptote points at. This is the number real launch planners check first, because it decides whether your pad can reach the trajectory at all. A departure asymptote is a line in space; your launch site sits at your GPS latitude.
• LAUNCH AZ (degrees) — the compass heading the rocket flies, computed from DLA and your latitude (due east while |DLA| ≤ |latitude|, otherwise the direct-ascent azimuth that reaches the asymptote).
• PAD FLAG — the verdict on DLA vs your pad: GREEN if the asymptote lies at or inside your latitude (due-east departure, no plane change), YELLOW if it misses by up to 10° (direct ascent can still reach it, steep and costly), RED beyond that (a plane change is required — the window is wrong for your pad). NO FIX means no GPS fix, so the flag is withheld rather than guessed.
• DEP DV (km/s) — the burn from your parking orbit (default 400 km, adjustable) into the transfer, from the vis-viva chain: √(v_esc² + v∞²) − v_circular. For a bound Moon departure (v∞ = 0) this degrades honestly to the TLI burn.
• CAP DV (km/s) — the capture burn at the destination into your capture orbit (default 300 km, adjustable): √(v_esc² + v∞²) − v_circular there.
• ENTRY V (km/s) — the speed you'd hit a 125 km entry interface at, if you aerocapture or land instead of burning.
• 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 is departure geometry, not the transfer. For Earth→Mars, the phase angle — Mars's heliocentric longitude minus Earth's, on departure day — wants about 44°, Mars ahead of Earth, for a Hohmann. The 180° figure is the transfer angle: the sweep the ship itself makes along half its ellipse. Don't mix the two. The instrument's 63.0° for the 294-day 2026 arc is plausible — longer-than-Hohmann arcs need Mars further ahead at departure.
• DLA decides the pad, not the energy. A cheap window you can't reach is not cheap. The 2026 Mars window departs at DLA +23.3° — from Honolulu (21.3°N) that's a YELLOW flag at azimuth 80.4°: direct ascent can reach it, steep but honest. The same window from an equatorial pad is GREEN, due east. If the flag is RED, don't force it — fly the next window, or fly from a different latitude. This is why the instrument refuses to guess: no GPS fix, no flag, no silent 0°.
• The Δv chain is the mission's bill. DEP DV (leave parking orbit) + CAP DV (enter the destination's orbit) is what the spacecraft must burn; the launcher's surface-to-parking number sits below it. Entry speed is the alternative to the capture burn — aerocapture trades heat-shield for propellant. Read all three before you call a window flyable.

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. The adaptive scan converges: depart 2026-10-30, fly ≈294 days, C3 9.14 — the true local minimum, not a cell center.
• 3. Refined check: v∞ departure 3.02 km/s (squared: 9.14 ✓), v∞ arrival 2.70 km/s, phase angle 63.0° — Mars well ahead of Earth, as a longer-than-Hohmann arc demands.
• 4. DLA +23.3°, launch azimuth 80.4°, PAD FLAG YELLOW from Honolulu — direct ascent reaches it.
• 5. The Δv chain: 3.59 km/s from a 400 km parking orbit, 2.12 km/s capture into 300 km at Mars, entry speed 5.63 km/s if you aerocapture instead.
• 6. From Honolulu: rotational boost 0.43 km/s → est. launcher Δv 11.15 km/s from the pad.
• 7. 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.

The next three Mars windows (from NEXT 3 WINDOWS): 2026-10-30 (C3 9.14), 2028-12-02 (C3 8.94), 2031-02-25 (C3 8.27) — each about a synodic period apart, the later ones genuinely cheaper. Mars's eccentric orbit shifts them off the exact 780-day rhythm; the instrument follows the physics, not the calendar.

The 2026 round trip (ROUND TRIP, 30-day minimum stay): out 2026-10-30, stay 382 days at Mars, return dep 2028-09-06, total 7.72 km/s of spacecraft Δv (departure 3.59 + capture 2.12 + Mars-departure 2.01), Earth-arrival entry speed 11.92 km/s. The long stay is honest too: the return window, not the minimum, sets the schedule.

Built for the helm. Tested against JPL. Flown by whoever dares next.