Megawatt solar-electric propulsion is used on several missions a year

Electric thrusters push gently but use a tenth of the propellant of a chemical rocket, and fed by large enough solar arrays they can keep pushing for months. Missions today run on kilowatts to tens of kilowatts; at a megawatt of thruster power, a solar-electric ship could carry a useful payload to the asteroid belt in about a year without a reactor. Megawatt solar spacecraft are already being built for orbital computing, which is where the arrays could come from. This is the solar route to fast transit, beside nuclear propulsion.

The test: what counts as it having happened

In one calendar year, at least three separate missions beyond low Earth orbit use solar-electric propulsion with at least one megawatt of electrical power delivered to the thrusters for their main transfer, meaning the burns that supply most of the mission's velocity change beyond low Earth orbit, confirmed by the operators and independent tracking.

Settled by: Operators' mission records and independent tracking

The odds, by how long I live

baselineto 2071 ± 8	moderateto 2080	strongto 2095	radicalto 2136	openno deadline
50%	60%	73%	84%	88%

Each column is a different guess at how long I live, from current trends (baseline) to open-ended. The number is the chance this happens before that deadline, assuming everything it depends on happens first. As of 2026-10-02.

Why these numbers: First estimate of 2026-09-25 raised at John's ruling on 2026-10-02: solar-electric is further along than nuclear propulsion and needs no reactor approvals, so it now sits above routine nuclear propulsion in the near windows rather than level with it; in the two longest windows it stays just under, because it weakens with distance from the Sun. The reasoning of the first estimate follows, and its last sentence describes the earlier setting. The parts exist: electric thrusters are flown every day, and megawatt solar spacecraft are funded for the late 2020s. What is missing is thrusters clustered to a megawatt and a customer who needs three heavy transfers a year beyond low Earth orbit, such as cargo tugs to the Moon or beyond. Set level with routine nuclear propulsion's own number: solar-electric is further along and needs no reactor politics, but weakens with distance from the Sun.

What this one is worth

If this happened tomorrow and nothing else changed, the chance that I live and work off Earth by 2071 goes from 0.5% to 0.6% (+0.1 points). If it turned out no, the same number goes to 0.3% (−0.1 points).

Longevity scenario	baseline2071 ± 8	moderate2080	strong2095	radical2136	openno deadline
The headline as it stands	0.5%	1.2%	3.8%	11%	15%
If this settled yes now	0.6%	1.3%	3.9%	11%	15%
If this settled no now	0.3%	1.1%	3.3%	10.0%	14%

This is what the site says in advance, before the thing happens. When it does, the ledger entry that records it quotes this figure beside what actually followed, so a reader can see whether the prediction held. Worked out at the run 2026-10-11-scan by holding this step at each outcome in turn and playing the whole tree out again, 20,000 times per scenario. That is a throw of the dice, so a move smaller than about 0.10 points is inside the noise rather than a finding.

What the ledger says about this step

• Megawatt solar-electric propulsion becoming routine was raised at John's ruling: it is further along than nuclear propulsion and needs no reactor approvals 2026-10-02 Changed my mind

The last check

Once a week the tree is read against the news, node by node, against the test above. Open a line to see what that week held. Every check ever made on this node is on the Radar page.

• 2026-10-04 Nothing new

  No megawatt-class solar-electric mission flew in the window; the PPE is about 60 kilowatts and NASA's lithium MPD thruster work (120 kilowatts, February 2026) is ground testing.

Revisions

Date	Field	From	To	Why
2026-10-02	probability	0.40 / 0.52 / 0.68 / 0.82 / 0.87	0.50 / 0.60 / 0.73 / 0.84 / 0.88	Ruling on the first estimates of the function-over-route pass (pull request 29). Claude, reviewing the first estimate, proposed 0.50 by 2071 on the ground that solar-electric is further along than nuclear propulsion and needs no reactor approvals; John accepted on 2026-10-02. The figures for the four longer windows are Claude's, scaled to keep the same shape.

Notes

Added 2026-09-25 as a route under D-fast-transit-in-routine-use (candidate 6 of docs/proposal-function-over-route-2026-09-25.md, approved by John 2026-09-25). Written to match D-nuclear-propulsion-in-routine-use (three missions beyond low Earth orbit in a year, main transfer defined the same way) so the two routes are like for like. E-megawatt-spacecraft-operates-in-orbit is a sibling rather than a dependency: a megawatt solar-electric ship running for a month resolves that step by construction.

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Think this is wrong, missing something it depends on, or badly estimated? Open an issue about it, or read how feedback gets folded into the tree. The record itself is data/D-drive.toml in the public repository.