Spacecraft Mass Budget Calculator
Subsystem-level mass rollup with Current Best Estimate (CBE), contingency margins, and Maximum Expected Value (MEV). Follows AIAA S-120 and NASA-STD-1001 margin practice.
Subsystems (CBE dry mass)
Propellant
Mass rollup
| Subsystem | CBE (kg) | Margin | MEV (kg) |
|---|---|---|---|
| Structure | 45.00 | 15% | 51.75 |
| Power (EPS) | 25.00 | 15% | 28.75 |
| Comms | 8.00 | 15% | 9.20 |
| ADCS | 12.00 | 15% | 13.80 |
| Thermal | 6.00 | 15% | 6.90 |
| CDH / OBC | 4.00 | 15% | 4.60 |
| Propulsion (dry) | 10.00 | 15% | 11.50 |
| Harness | 5.00 | 20% | 6.00 |
| Payload | 35.00 | 10% | 38.50 |
| Dry mass (CBE) | 150.00 | 171.00 | |
| Propellant | 15.00 | 10% | 16.50 |
| Wet mass | 165.00 | 187.50 |
Track mass growth over time, link to requirements, export for PDR/CDR?
Sign up →Frequently asked questions
What margins should I apply at each lifecycle phase?
Industry practice: 30% at concept (before SRR), 20% pre-PDR, 15% at PDR, 10% at CDR, 5% for flight spare post-qualification. These are per-subsystem contingencies, not a blanket system margin. Reference: AIAA S-120A and NASA Mass Growth Allowance Policy (JSC 23303).
What's the difference between CBE and MEV?
CBE (Current Best Estimate) is what you believe the subsystem masses are today. MEV (Maximum Expected Value) applies contingency margins to each line. Launch vehicles quote capacity in MEV because it bounds the worst case.
Should propellant get a margin too?
Separate from dry-mass margins, propellant typically carries an 8-10% reserve for residuals, leaks, and mission extension. This tool treats propellant reserve independently.
Need more than this?
- Real-time mass tracking from component BOM
- Bi-directional traceability to requirements and ICDs
- Mass growth history and phase-gate deltas
- Export to PDR/CDR deliverable templates
- Integrated with power, thermal, and link budgets