Will SPARC demonstrate a fusion gain Q above 1 before 31 December 2027?
deadline 2027-12-31
confidence medium
tier 4 evidence
14%PolySignal estimate
Resolution criterion
Yes if CFS announces, and a paper or scientific presentation documents, a SPARC discharge with fusion power greater than the injected heating power.
Verified starting state
SPARC targets Q of roughly 11 and 140 MW on 10-second discharges, with a public target of scientific breakeven in 2027. First plasma had not occurred as of 17 September 2026. Ramping up to deuterium-tritium typically takes more than a year of campaign.
What pushes it up
- Commonwealth Fusion Systems (CFS) is well-funded, having raised $1 billion to accelerate SPARC and ARC development [0, tier 4].
- The official public target for scientific breakeven remains 2027 [Starting State, tier 1].
What pushes it down
- First plasma had not occurred as of September 17, 2026, leaving only 15 months to reach the deadline [Starting State, tier 1].
- Ramping up to a deuterium-tritium (DT) campaign, which is required for Q > 1, typically takes more than a year after first plasma [Starting State, tier 1].
- The remaining timeline provides almost no margin for technical errors or commissioning delays common in fusion energy [General Knowledge].
What would move this number most
The exact date of first plasma; if it does not occur by late 2026, the subsequent year-long ramp-up to DT makes a 2027 Q > 1 demonstration mathematically improbable.
How this number is built
| Deadline | 2027-12-31 |
| Base rate | 20% |
| Best evidence | tier 4 · 1 article(s) used |
| Independent runs | 12 · 15 (spread 3 pts) |
| Confidence | medium |
| Evidence cap | not triggered |
| Last revised | 2026-09-22 00:34 |
| Model | gemini-3-flash-preview |
Sources consulted