# Glossary

A shared vocabulary across energy, computation, space and coordination.

Type: Reference · Reviewed: 4 October 2026

## Energy

| Term | Meaning |
| --- | --- |
| Watt (W) | Power: one joule per second. |
| Kilowatt-hour (kWh) | Energy: 1 kW sustained for an hour, equal to 3.6 million joules. |
| Terawatt-hour (TWh) | One billion kilowatt-hours. |
| Energy intensity | Energy per defined unit of useful output. |
| PUE | Facility energy divided by IT equipment energy. |
| Carbon intensity | Emissions attributed per electricity unit, dependent on time, place and method. |
| Embodied impact | Impact from producing and deploying hardware, separate from operation. |

Source: [Power Usage Effectiveness](https://www.thegreengrid.org/node/372) — The Green Grid. The definition of facility energy divided by IT equipment energy.

## Computation

| Term | Meaning |
| --- | --- |
| SI | The intelligence theme in SpaceXSI, explored through computation and optimization. |
| Inference | Applying a trained model to new inputs. |
| Quantization | Representing values at reduced precision. |
| Batching | Processing requests together to share execution resources. |
| Utilization | Used capacity as a fraction of available capacity. |
| Quality gate | The acceptance test for an output to count as useful. |
| Attestation | A verifiable statement about an execution or measurement. |

Source: [Quantization schemes](https://docs.nvidia.com/deeplearning/tensorrt/latest/inference-library/quantized-types-schemes.html) — NVIDIA · TensorRT documentation. Lower-precision inference formats and their implementation constraints.

## Space systems

| Term | Meaning |
| --- | --- |
| LEO | Low Earth orbit; behavior depends on altitude, inclination and geometry. |
| Sun-synchronous orbit | An orbit maintaining approximately consistent local solar time at crossings through precession. |
| Eclipse | A period shadowed from direct sunlight. |
| Radiator | A surface engineered to emit heat as radiation. |
| Downlink | Data transfer from spacecraft to Earth. |
| End-of-life performance | Capability expected after mission aging. |
| Lifecycle assessment | Evaluation across production, deployment, operation and disposal. |

Source: [Small spacecraft: power subsystems](https://www.nasa.gov/smallsat-institute/sst-soa/power-subsystems/) — NASA. Solar arrays, storage, eclipses and end-of-life power budgeting.

Source: [Small spacecraft: thermal control](https://www.nasa.gov/smallsat-institute/sst-soa/thermal-control/) — NASA. Heat transfer in vacuum and spacecraft thermal management.

## Coordination

| Term | Meaning |
| --- | --- |
| Proof-of-stake | Consensus whose primary mechanism uses staked assets rather than competitive mining. |
| Onchain | Recorded or executed in shared blockchain state. |
| Offchain | Performed outside that shared state. |
| Commitment | A compact reference binding a participant to data. |
| Settlement | Finalizing an accepted transfer or obligation. |
| Oracle | A mechanism for introducing external information into a blockchain. |

Source: [Ethereum energy consumption](https://ethereum.org/energy-consumption/) — ethereum.org. The energy implications of proof-of-stake; reported estimates have specific dates and boundaries.