The tree · Drive · World event · Mid: 5 to 20 years
A nuclear-powered engine changes a spacecraft's orbit in space for the first time
Nuclear propulsion, whether a reactor heating propellant directly or a reactor driving electric thrusters, has been designed and ground-tested for sixty years and never flown. The first in-space burn that actually moves a vehicle is the step from paper to hardware, and it is what routine nuclear propulsion, the Tier 3 criterion, has to start from.
What counts as it having happened
A spacecraft in space changes its velocity by at least one kilometre per second using propulsion powered by a nuclear reactor, confirmed by the operator and by independent orbital tracking.
Settled by: The operator's mission record and independent orbital tracking
Probability, by longevity scenario
| baseline2071 ± 8 | moderate2080 | strong2095 | radical2136 | openno deadline |
|---|---|---|---|---|
| 60% | 72% | 85% | 93% | 95% |
Each number is the chance this resolves yes before that scenario's window closes, given that everything it depends on resolves first. Estimated 2026-09-19.
Why these numbers: Sixty years of ground tests and no flight, and the most recent flight demonstration program was cancelled in 2025; it needs a mission only nuclear can do.
Notes
Shares a technology base with the lunar surface reactor (an energy node); whether that is a hard dependency is for step 7.
Think this node is wrong, missing a dependency, or estimated badly?
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The record itself is data/D-drive.toml in the public repository.