Subsystem Mass Budget & Principal Inertia Calculator
Track Current Best Estimate (CBE) subsystem masses, ECSS 12% system margin, deployer reserve, and principal moments of inertia.
DETERMINISTIC PHYSICS & DATA METHODOLOGY
How This Calculator Works
Source modules: components/lab/v3-tools.tsx, lib/physics/structures.ts
Sums Current Best Estimate (CBE) subsystem masses, applies a 12% system-level ECSS preliminary design maturity margin against deployer mass limits, and estimates 50 mm 1P cube principal inertia alongside Rayleigh/Leissa baseplate modal benchmarks.
Governing Equations & Physical Model
m_sys = 1.12 · Σ m_CBE,i, m_res = m_limit − m_sysApplies 12% system contingency to the six subsystem allocations (structure, EPS, OBC/comms, ADCS, payload, harness).
I_xx = I_yy = m_sys · (L² + L²) / 12 = m_sys · L² / 6Evaluated at L = 0.050 m; companion structural solver lib/physics/structures.ts gives f₁ = 1,997 Hz for a 1.6 mm Al 7075-T6 backplate carrying a 38 g stack.
Inputs, Parameters & Units
| Parameter | Unit | Physical definition |
|---|---|---|
| m_struct .. m_harn | g | Six subsystem Current Best Estimate (CBE) dry masses. |
| m_limit | g | Deployer ICD maximum allowable mass (250 g 1P AlbaPod; 1,330–2,000 g 1U CubeSat). |
Assumptions & Validity Limits
- Applies a uniform 12% maturity margin across all subsystems; ECSS-E-ST-10-02C hardware-category margins (5% COTS, 20% new development) should be itemized at CDR.
- Principal inertia assumes a 50 mm cubic envelope; elongated 2P/3P stacks scale axial/transverse inertia via /lab/comparator/.
Worked Default Reference Case
Six subsystem CBEs total 220 g; adding 12% margin yields 246.4 g (+3.6 g positive reserve below 250 g) and principal inertia I = 1.03×10⁻⁴ kg·m².
- Total dry mass (CBE)
- 220 g
- With 12% ECSS margin
- 246.4 g (+3.6 g reserve)
- Principal inertia I_xx
- 1.03×10⁻⁴ kg·m²
- 1.6 mm Al 7075 baseplate f₁
- 1,997 Hz (> 200 Hz PASS)