IICSM satellite and Proxima Centauri design scripts
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Run in the webpage forms, or download space-design-core.js and use Node.js:

  const model = require('./space-design-core.js');
  const sat = model.satellite({...model.satelliteDefaults,
    ...model.presets.geo, dryMass: 50, sunPower: 60});
  console.log(sat.orbit.period, sat.batteryWh, sat.area);

  const trip = model.star({...model.starDefaults,
    mode: 'symmetric', acceleration: 1});
  console.log(trip.time/model.constants.YEAR,
    trip.properTime/model.constants.YEAR, trip.beta);

No dependencies or network access. CommonJS module export in Node; SpaceDesign
global in browsers. Copy defaults before changing parameters. Presets fill hp,
ha and inclination only. Browser JSON exports contain inputs, results, units
implied by the schema below, constants and version. CSV exports contain chart
samples with units in the column headings. Inputs are not sent to a server.

Satellite inputs
hp, ha: perigee/apogee ALTITUDE above mean Earth surface, km (100 to 400000).
inclination: degrees, 0 to 180. beta: Sun elevation over orbit plane, -90 to 90.
sunLongitude: projected Sun direction from periapsis, degrees (-180 to 180).
dryMass: kg (hardware including tanks, excluding usable propellant).
dv: ideal maneuver budget in m/s. isp: effective specific impulse, seconds.
sunPower, eclipsePower: segment-average bus load in watts.
cellEfficiency, degradation, busEfficiency, chargeEfficiency,
dischargeEfficiency, dod, capacity: PERCENT, not fractions. Degradation and
capacity mean percent REMAINING. Incidence is mean sunlit cosine (0 < x <= 1).
heat: total watts assigned to radiator. temperature: kelvin. emissivity: fraction.
dataRate: compressed payload Mbit/s while acquiring.
acquisitionMinutes: acquisition minutes/orbit. downlinkRate: usable Mbit/s.
contactMinutes: entered contact minutes/orbit, not calculated ground visibility.

Satellite outputs
orbit.a/rp/ra: centre-to-centre km; orbit.e: dimensionless eccentricity.
orbit.period/eclipse/sunlight/resolution: seconds; vPeri/vApo: m/s.
orbit.nodeRate: degrees/day, first-order orbit-averaged J2.
orbit.points: orbit-plane x/y km and cylindrical-shadow boolean.
eclipseWh and batteryWh: Wh. arrayPower: W. area and radiator: m^2.
propellant and wetMass: kg. generated/downlinked/dataBalance: bits per orbit.
Circular eclipse is analytical; elliptical eclipse uses 4096 uniform-time
midpoint samples. Step size is reported; total boundary uncertainty is roughly
two steps. Orbital plane position chart samples every eighth integration point.

Star inputs
mode: 'cruise', 'symmetric', or 'capped'.
distance: fixed target distance, light-years (default rounded Proxima 4.25).
beta: speed / c, 0 < beta < 1; ignored for 'symmetric'.
acceleration: constant proper acceleration in Earth g; ignored for 'cruise'.
mass: fixed vehicle rest mass, kg. efficiency: PERCENT for an acceleration
kinetic-energy conversion estimate, not a complete propulsion budget.

Star outputs
time and properTime: seconds; beta: peak speed/c; gamma: peak Lorentz factor.
kinetic and energyInput: J. lightYears: one-way light travel years, numerically
equal to input distance in light-years. arrivalSignalYears: Earth-frame years
after launch when a signal emitted on arrival reaches the fixed Earth origin.
acceleration: m/s^2 (zero in cruise model). phases: distance in metres, time and
proper time in seconds. points: Earth years, light-years travelled and beta.
The rest-to-rest profiles brake to zero speed relative to the fixed target.
The flyby omits acceleration and braking and arrives at its cruise speed.

Model scope
Earth: spherical two-body geometry, fixed Sun direction, no atmospheric decay,
launch, ground track, thermal view factors or operational mission verification.
J2 rate is a separate first-order diagnostic, not integrated into the orbit.
Proxima: straight-line special-relativistic kinematics, no stellar ephemerides,
target motion, gravity, propulsion system, changing mass or navigation solution.
Peak kinetic energy must be removed during braking for a rest-to-rest trip;
no fuel requirement or recovery assumption is inferred from that energy.

Reference pages and full derivations:
https://iicsm.org/physicalmodeling/satellite-design.html
https://iicsm.org/physicalmodeling/trajectory-calculation.html
https://www.nasa.gov/smallsat-institute/sst-soa/
https://science.nasa.gov/asset/hubble/proxima-centauri/