DELTA-SIERRA MARS TOOL
Availability and spares calculator
Do not confuse intrinsic availability with real operational availability.
Essential answer
A system can have good intrinsic availability but poor operational availability if spares, diagnostics, or logistics delays are weak. Availability boundaries must therefore be named.
Every value is editable. Scenario values are not an official NASA architecture.
Calculator
Method and limitations
Aᵢ = MTBF/(MTBF+MTTR) ignores logistics delay, diagnostics, preventive maintenance, and real failure distributions. The spare estimate also assumes a stationary rate: it is an order-of-magnitude model, not a probabilistic guarantee.
Primary sources and evidence status
The calculation distinguishes physical relation, demonstrated value, standard, educational assumption, and Delta-Sierra scenario.
- NASA — Reliability and Maintainability
NASA R&M discipline page and current NASA-STD-8729.1A context. The tool uses a simple intrinsic-availability approximation and a constant-rate spare-demand model.
Sources and further reading
Downloadable scenario data
Dataset v1.1 documents every prefilled value: unit, system boundary, time basis, evidence status, and source when one exists.
Entry, descent and landing (EDL)
- Mars entry, descent and landing: understanding the full EDL chain
- Mars atmospheric entry: heat shield, entry corridor and guidance
- Mars parachutes and supersonic retropropulsion: where architecture changes
- Terrain-relative navigation, hazards and Mars landing-site selection
- Terminal descent, engine plumes and the Mars landing zone
- Human Mars lander: the EDL problem above 20 tonnes
Survive: ECLSS, health and resilience
- Mars habitat ECLSS: complete architecture of survival loops
- Mars habitat air: oxygen, CO₂, humidity and contaminants
- Mars water: 98% recovery, storage, quality and make-up
- Fire, depressurization and refuge: surviving habitat emergencies
- Mars radiation: shielding, dose and storm shelter
- Spacesuits, EVA and dust: working outside without contaminating the base
- Food, crops and medicine: biological and medical autonomy on Mars
- Psychology, fatigue and multiple failures: human resilience of a Mars base
Operations, industry, reliability and team
- Choosing a site and deploying a Mars base
- Mars surface mobility, robotics and logistics
- Mars ISRU industry, construction and local manufacturing
- Reliability, redundancy and common causes in a Mars base
- Durability, tightness, electronics and FDIR on Mars
- Mars maintenance, spares, qualification and configuration
- Crew operations, procedures and Earth-Mars communications
- Human factors, anomalies and training for a Mars team