Better accuracy

src/engine/rocketDesignCalcs.js

@@ -1,6 +1,46 @@
 // Pure calculation functions for rocket vehicle design (no React)
 
+import { STRUCTURAL_MATERIALS } from './knowledgebaseData.js'
+
 const G0 = 9.80665 // m/s² standard gravity
+const R_HE = 2077 // J/kg/K — specific gas constant for helium
+const T_PRESSURANT = 293 // K — standard pressurant storage temperature
+
+/**
+ * Generate nose cone profile points (r vs x) for a given shape.
+ * All shapes share L = 2R.
+ *
+ * @param {string} shape — 'conical' | 'tangentOgive' | 'vonKarman'
+ * @param {number} R — base radius (m)
+ * @param {number} L — nose length (m)
+ * @param {number} n — number of points (default 24)
+ * @returns {Array<{x, r}>} profile points from tip (x=0) to base (x=L)
+ */
+function noseConeProfile(shape, R, L, n = 24) {
+  const points = []
+
+  for (let i = 0; i < n; i++) {
+    const x = (i / (n - 1)) * L
+    let r
+
+    if (shape === 'tangentOgive') {
+      // Tangent ogive: ρ = (R² + L²) / (2R)
+      const rho = (R * R + L * L) / (2 * R)
+      r = Math.sqrt(rho * rho - (L - x) * (L - x)) - (rho - R)
+    } else if (shape === 'vonKarman') {
+      // Von Kármán (LD-Haack): θ = acos(1 − 2x/L), r = (R/√π) * √(θ − sin(2θ)/2)
+      const theta = Math.acos(1 - 2 * x / L)
+      r = (R / Math.sqrt(Math.PI)) * Math.sqrt(theta - Math.sin(2 * theta) / 2)
+    } else {
+      // Default conical: r(x) = R * (x / L)
+      r = R * (x / L)
+    }
+
+    points.push({ x, r: Math.max(0, r) })
+  }
+
+  return points
+}
 
 /**
  * Calculate full rocket geometry and performance from engine data and rocket inputs.
@@ -15,7 +55,13 @@ const G0 = 9.80665 // m/s² standard gravity
  *   rhoOx,               // kg/m³
  *   payloadMass,         // kg
  *   payloadBayLength,    // m
- *   structMassFraction,  // 0–1 (dry mass fraction of propellant mass)
+ *   tankMaterialId,      // 'al_6061_t6' | 'ss_304' | ... (structural material)
+ *   tankSafetyFactor,    // safety factor for hoop stress
+ *   feedSystem,          // 'pressure_fed' | 'pump_fed'
+ *   ullagePercent,       // % extra volume above propellant for gases
+ *   otherStructFraction, // fraction of propellant mass for non-tank structure
+ *   engineDryMass,       // kg (from engine structural results, null if not available)
+ *   noseConeShape,       // 'conical' | 'tangentOgive' | 'vonKarman'
  * }
  * @returns {object|null}
  */
@@ -31,13 +77,20 @@ export function calcRocketGeometry(engineData, rocketInputs) {
     rhoOx,
     payloadMass,
     payloadBayLength,
-    structMassFraction,
+    tankMaterialId,
+    tankSafetyFactor,
+    feedSystem,
+    ullagePercent,
+    otherStructFraction,
+    engineDryMass,
+    noseConeShape,
   } = rocketInputs
 
   const Isp  = engineData?.allThermo?.Isp
   const F    = engineData?.allThermo?.F
   const mdot = engineData?.allThermo?.mdot
   const OF   = engineData?.allThermo?.OF
+  const p0   = engineData?.allThermo?.p0 ?? 6.9e6  // Chamber pressure, default 6.9 MPa
 
   // Flow rates: use direct values if solved, otherwise derive from mdot + OF
   let mdot_f  = engineData?.allThermo?.mdot_f
@@ -65,8 +118,9 @@ export function calcRocketGeometry(engineData, rocketInputs) {
   const V_ox   = m_ox   / rhoOx
   const V_prop = V_fuel + V_ox
 
-  // ── Nose cone (ogive approximation: height = 2R) ────────────────────
+  // ── Nose cone (height = 2R) ───────────────────────────────────────────
   const L_nose = 2 * R
+  const noseProfilePoints = noseConeProfile(noseConeShape ?? 'conical', R, L_nose, 24)
 
   // ── Payload bay ─────────────────────────────────────────────────────
   const L_payload = payloadBayLength ?? 0
@@ -76,33 +130,90 @@ export function calcRocketGeometry(engineData, rocketInputs) {
   const cg = engineData?.chamberGeometry
   const L_engine = (ng?.Ln ?? 0) + (cg?.Lc ?? 0)
 
-  // ── Tank geometry ───────────────────────────────────────────────────
-  let L_tank_fuel, L_tank_ox, L_tank, r_inner
+  // ── Tank geometry with domes and ullage ──────────────────────────────
+  let L_tank_fuel, L_tank_fuel_cyl, L_tank_ox, L_tank_ox_cyl, L_tank, r_inner, m_tank_fuel, m_tank_ox, m_tank_total
+  let t_wall = null
+
+  const ullage = ullagePercent ?? 5
+  const materialId = tankMaterialId ?? 'al_6061_t6'
+  const material = STRUCTURAL_MATERIALS.find(m => m.id === materialId) || STRUCTURAL_MATERIALS[0]
+  const SF = tankSafetyFactor ?? 2.0
+
+  // Tank pressure (Pa)
+  const p_tank = feedSystem === 'pump_fed' ? 2e6 : p0 * 1.2
+
+  // Hoop stress wall thickness (same for all tanks at same pressure and radius)
+  t_wall = (p_tank * R) / (material.yieldStrength / SF)
 
   if (arrangement === 'coaxial') {
-    // Both tanks share the same axial section; total volume in annulus + inner cylinder
-    // Inner tank radius from the smaller propellant volume
-    // Outer tank occupies the remaining annular area
+    // Coaxial: hemispherical domes only on outer tank; inner tank is annular (flat bulkheads)
     const V_inner = innerPropellant === 'fuel' ? V_fuel : V_ox
     const V_outer = innerPropellant === 'fuel' ? V_ox   : V_fuel
 
-    // Solve for tank length using outer volume first (conservative — outer is usually larger)
-    // V_outer = π (R² - r_inner²) L_tank  and  V_inner = π r_inner² L_tank
-    // From V_inner / (V_inner + V_outer) = r_inner² / R²
-    //   → r_inner = R √(V_inner / V_prop_total)
     r_inner = R * Math.sqrt(V_inner / V_prop)
-    // Guard: inner radius must be smaller than outer
     if (r_inner >= R) r_inner = R * 0.7
 
-    L_tank = V_prop / (Math.PI * R * R)
-    L_tank_fuel = arrangement === 'coaxial' ? L_tank : null
-    L_tank_ox   = arrangement === 'coaxial' ? L_tank : null
+    // Outer tank: account for dome volume
+    const V_dome_outer = (4 / 3) * Math.PI * R * R * R
+    const V_eff_outer = V_outer * (1 + ullage / 100)
+    const L_tank_cyl_outer = Math.max(0, (V_eff_outer - V_dome_outer) / (Math.PI * R * R))
+
+    // Inner annular tank (no domes): full volume in cylindrical section
+    const A_annulus = Math.PI * (R * R - r_inner * r_inner)
+    const L_tank_cyl_inner = V_inner / A_annulus
+
+    // Total outer tank length
+    const L_tank_outer = L_tank_cyl_outer + 2 * R
+
+    // Both tanks are coaxial, so effective length is the longer one
+    L_tank = Math.max(L_tank_outer, L_tank_cyl_inner)
+
+    // For compatibility with tandem display
+    L_tank_fuel = L_tank
+    L_tank_fuel_cyl = L_tank_cyl_outer
+    L_tank_ox = L_tank
+    L_tank_ox_cyl = L_tank_cyl_inner
+
+    // Coaxial tank mass: outer tank with domes + inner annular section
+    const m_cyl_outer = 2 * Math.PI * R * t_wall * L_tank_cyl_outer * material.density
+    const m_dome_outer = 4 * Math.PI * R * R * t_wall * material.density
+    const m_tank_outer = m_cyl_outer + m_dome_outer
+
+    const m_cyl_inner = 2 * Math.PI * r_inner * t_wall * L_tank_cyl_inner * material.density
+    const m_tank_inner = m_cyl_inner  // Inner annular tank, no domes
+
+    m_tank_total = m_tank_outer + m_tank_inner
   } else {
-    // Tandem: stacked cylinders
-    L_tank_fuel = V_fuel / (Math.PI * R * R)
-    L_tank_ox   = V_ox   / (Math.PI * R * R)
+    // Tandem: both tanks have hemispherical domes
+    // Effective volumes include ullage
+    const V_eff_fuel = V_fuel * (1 + ullage / 100)
+    const V_eff_ox   = V_ox   * (1 + ullage / 100)
+
+    // Dome volume for each tank
+    const V_dome_one = (4 / 3) * Math.PI * R * R * R
+
+    // Cylindrical sections
+    L_tank_fuel_cyl = Math.max(0, (V_eff_fuel - V_dome_one) / (Math.PI * R * R))
+    L_tank_ox_cyl   = Math.max(0, (V_eff_ox   - V_dome_one) / (Math.PI * R * R))
+
+    // Total tank lengths including domes
+    L_tank_fuel = L_tank_fuel_cyl + 2 * R
+    L_tank_ox   = L_tank_ox_cyl   + 2 * R
     L_tank      = L_tank_fuel + L_tank_ox
     r_inner     = null
+
+    // Tank mass: cylindrical + dome shells (two hemispheres = full sphere surface area)
+    m_tank_fuel = (2 * Math.PI * R * t_wall * L_tank_fuel_cyl * material.density) + (4 * Math.PI * R * R * t_wall * material.density)
+    m_tank_ox   = (2 * Math.PI * R * t_wall * L_tank_ox_cyl   * material.density) + (4 * Math.PI * R * R * t_wall * material.density)
+    m_tank_total = m_tank_fuel + m_tank_ox
+  }
+
+  // ── Pressurant system (pressure-fed only) ─────────────────────────────
+  let m_pressurant = 0
+  if (feedSystem === 'pressure_fed') {
+    const m_He = (p_tank * V_prop) / (R_HE * T_PRESSURANT)
+    const m_bottle = m_He * 4 // Conservative bottle mass estimate
+    m_pressurant = m_He + m_bottle
   }
 
   // ── Total vehicle length ────────────────────────────────────────────
@@ -110,9 +221,11 @@ export function calcRocketGeometry(engineData, rocketInputs) {
 
   // ── Mass budget ─────────────────────────────────────────────────────
   const m_prop = m_fuel + m_ox
-  const m_struct = m_prop * (structMassFraction ?? 0.10)
+  const m_other_struct = m_prop * (otherStructFraction ?? 0.05)
+  const m_struct = m_tank_total + m_other_struct
   const m_payload = payloadMass ?? 0
-  const m_dry = m_struct + m_payload
+  const m_engine = engineDryMass ?? 0
+  const m_dry = m_struct + m_payload + m_engine + m_pressurant
   const m_wet = m_prop + m_dry
 
   const massRatio = m_wet / m_dry
@@ -135,6 +248,8 @@ export function calcRocketGeometry(engineData, rocketInputs) {
     L_tank,
     L_tank_fuel,
     L_tank_ox,
+    L_tank_fuel_cyl,
+    L_tank_ox_cyl,
     L_engine,
     totalLength,
     r_inner,
@@ -146,8 +261,13 @@ export function calcRocketGeometry(engineData, rocketInputs) {
     m_prop,
     m_struct,
     m_payload,
+    m_engine,
     m_dry,
     m_wet,
+    m_tank_total,
+    m_pressurant,
+    // Tank structure
+    t_wall,
     // Performance
     massRatio,
     deltaV,
@@ -160,6 +280,8 @@ export function calcRocketGeometry(engineData, rocketInputs) {
     nozzleThroatRadius: ng?.rt ?? null,
     chamberLength:      cg?.Lc ?? 0,
     nozzleLength:       ng?.Ln ?? 0,
+    // Nose cone profile for 3D model
+    noseProfilePoints,
   }
 }