surya.narada.systems

R2: the coupled-stressor gap, mapped

Sweep executed 18 August 2026. The finding: the gap is real, it is total, and the review literature now names it in the program's own words. No published ground study combines particle radiation with thermal cycling on a perovskite cell; no experiment anywhere combines three or more space stressors. Everything multi-stressor is flight data, where the stressors are inseparable by construction.

Why this map exists

The R2 readiness baseline (August 2026) established that perovskite flight heritage exists and the open gap is multi-year duration under coupled UV / ATOX / thermal stressors, not existence of the effect. R2 wins when a credible 5-year LEO degradation model survives independent replication. This page converts that one-sentence gap into a work program: what evidence exists per stressor, what has never been measured, and what the incumbent qualification practice says "credible" must mean.

Single-stressor inventory

StressorBest evidence to dateWhat LEO needsState
Electrons1 MeV to 10¹⁶ e/cm² — no deterioration (Miyazawa 2018; Caltech 2017)Matches the AIAA S-111 characterization ceilingstrongest
ProtonsTolerated to ~10¹³ p/cm² with in-situ self-healing; failure at 3×10¹⁴ via transport-layer breakdown, not the absorberS-111 range 10¹⁰–10¹³ p/cm² — covered, but tested at room temperature and low flux, not orbit-realisticstrong, single-stressor only
UV800 h continuous narrowband 365 nm is the longest publishedAM0-calibrated dose (equivalent sun-hours) — no such perovskite dataset existsthin
Atomic oxygenOne dedicated study: 120 min accelerated plasma. SiO encapsulation retained >97%; unencapsulated lost ~45% PCE; 2D-passivated cells degraded fastest (the 2D layer is an ATOX diffusion channel)Fluence-calibrated (atoms/cm²) exposure over mission-representative dosesnearly absent
Thermal cyclingWidest published: −60/+80 °C × 120 cyclesLEO range ~−120/+120 °C, thousands of cycles (5,800/yr); incumbent cells are cycled to 20,000absent
VacuumOutgassing and MAI volatility documented; light-driven vacuum decomposition is self-limiting after ~24 h; one 6-cycle vacuum-thermal-MPP experiment (JKU Linz)Thermal-vacuum cycling with IV monitoring, hundreds of cyclesthin
Humidity / ingressGlass-glass + edge seal passes IEC 61215 damp heat (1000 h, 85/85); thin-film barriers at 10⁻⁵ g/m²/dayTerrestrial anchor exists; not a space discriminatoradequate terrestrially
Combined (the point)Terrestrial light+heat only (NREL, Nature 2023 — synergy documented: combined stressors produce failure modes absent in single tests). Everything else is flight data with inseparable stressorsRadiation + thermal cycling + AM0 + vacuum, simultaneously, with attributionthe gap

established Radiation tolerance is the strong suit: the absorber survives doses past the S-111 characterization ceiling, and self-healing during irradiation is documented physics (dual-dose proton experiments show damage and repair in the same exposure). The documented failure path at extreme fluence is the organic transport layer, not the perovskite — which points the materials work at the stack, not the absorber.

The coupled-stressor gap

established Three independent sweeps converged on the same negative result. Kirmani & Sellers (Joule 2025): radiation testing is done at room temperature and low flux, while orbit adds thermal cycling, AM0 illumination, and atomic oxygen simultaneously. Akylbayeva et al. (2026): stressors act synergistically and are not detected by single-factor tests; standardized space protocols for this class do not exist. Kim et al. (2026): long-term operational data under combined space stressors is "critically insufficient." Terrestrially, NREL has already shown the trap: combined light+heat produces failure modes that single-stressor testing never sees. There is no reason to expect space stressors to be kinder.

The gap, decomposed into four fillable datasets:(1) LEO-range thermal-vacuum cycling with IV monitoring — hundreds of cycles, −120/+120 °C class; (2) AM0-calibrated UV dose response, in equivalent sun-hours; (3) fluence-calibrated ATOX exposure (atoms/cm²), with and without candidate encapsulations; (4) the combined in-situ campaign — radiation + thermal cycling + AM0 + vacuum at once. Facilities for combined exposure exist (NASA Glenn, MSFC, ESA/ESTEC, DLR); none has published a perovskite PV campaign.

Flight heritage, restated as evidence class

  • MAPHEUS-8 (2019) — First perovskites in space; suborbital, minutes of exposure; full post-flight characterization published (Reb et al., Solar RRL 2023). Follow-up flight November 2024.
  • ISS MISSE (2020–21) — ~10 months exterior LEO. Film stayed black; incurred damage >90% reversible under light back on Earth. Combined environment by construction — no stressor attribution.
  • RIT CubeSat (2025–26) — ~100 days at ISS altitude, operated the entire flight, no breakdown. Kirmani group; journal paper forthcoming.
  • Big Red Sat-1 (2024) — 105 days LEO with a perovskite panel, TRL 5→6 objective. Data still being processed — watch item.
  • RHOK-SAT (2025) — Launched 14 September 2025. Results pending — watch item.

Flight data proves survival, not attribution: every flight combines every stressor and reports one outcome. It sets the floor of the model, never the curve.

What "credible 5-year model" means by incumbent practice

evidence-backed III-V qualification defines the bar: ground radiation data across energies reducible to a single displacement-damage-dose (or equivalent-fluence) curve; mission-spectrum convolution through coverglass shielding with SAVANT/SPENVIS-class tooling; end-of-life remaining-power prediction with demonstrated flight agreement (Equator-S; an 8.3-year validation dataset); and an S-111/S-112-class test matrix — a ~$4.5M, 1–2+ year campaign per cell technology (SBIR STRATFI award record). Note the structural opening: ECSS-E-ST-20-08C explicitly excludes thin-film cells, and even incumbent matrices run stressors sequentially. The qualification literature itself has no combined-stressor protocol — for anyone. The program-level leverage recorded on the directions page stands: whoever writes the ISOS-T-Space-class protocol defines everyone's market entry cost, and Akylbayeva et al. have already published the proposal sketch.

What this changes

R2's next moves, in order: watch the pending flight data (Big Red Sat-1, RHOK-SAT) for the first attributed-orbit performance points; scope the four datasets above as the fundable work — each is a ground campaign at an existing facility, not a new facility; and evaluate writing the combined-stressor test protocol itself as a program deliverable, per the qualification-lock analysis. The gap is not a wall; it is four datasets and a protocol.

Perimeter and provenance

Three parallel literature sweeps, 19 sources, admitted to the Surya epistemic graph as event ev-000000000007 with assessmentsurya-assessment-r2-gap-map-2026-08, judgmentestablished-with-gap. Sweep-level gaps, flagged honestly: MDPI full texts were bot-blocked, so a few quotes rest on abstracts and review citations rather than primary text; Big Red Sat-1 and RHOK-SAT performance data are unpublished at sweep time; no primary neutron-irradiation study was located; one vacuum decomposition study is known only through a review's citation. None of these change the shape of the map — they are recorded as perimeter, not smoothed over.

Sources