VERIFICATION & VALIDATION

Solver Verification
& Validation

This page describes what Verixos has validated today, what is only partially validated, and what is still planned. The current evidence base is strongest for lumped-parameter thermal solving itself; it is materially weaker for direct commercial-tool parity, hardware correlation, and thermal-structural truth prediction, and we do not claim those are complete yet.

13implemented benchmark artifacts
2structural handoff formats
1documented heritage reproduction chain
CURRENT POSTURE

What Exists Today

Verixos has real solver verification, a meaningful SAE parity argument, one documented heritage reproduction chain, working structural temperature handoff infrastructure, and real in-app workflow breadth across geometry-native prep, radiation/orbit authoring, saved studies, and correlation review. It does not yet have a published open benchmark pack against Thermal Desktop or ESATAN, and it does not yet have a completed public commercial FEA pilot.

In-App Workflow BreadthAvailable in product

Verixos includes geometry-native import and cleanup, remesh/readiness workflows, orbital/radiation authoring, saved studies, correlation review, and structural temperature handoff surfaces.

Analytical VerificationImplemented today

The solver core is covered by closed-form conduction, radiation, enclosure, convection, heat-pipe, and optics checks documented in the current validation evidence set.

SAE 961452 ParityImplemented today

Verixos matches or exceeds the SINDA/FLUINT analytical benchmark tolerances reported in SAE 961452 across the implemented parity points.

PharmaSat Heritage ChainImplemented today

Verixos reproduces a documented PharmaSat / SatTherm case. This is a heritage reproduction chain, not a direct re-run of raw NASA telemetry in Verixos.

Structural Temperature HandoffImplemented today

NASTRAN and Abaqus temperature artifacts, provenance-aware node mapping, and coupling manifests are available when source structural labels exist.

Published Public-Reference ParityImplemented for named cases

The current public evidence set includes a published Abaqus NAFEMS T3 transient-conduction parity pack and a NASA/NASTRAN washer steady-state parity pack with reproducible artifacts.

TVAC / Flight Correlation ToolingAvailable in product

The platform has test-dataset import, correlation, posterior uncertainty, and flight-telemetry workflows, but no public hardware-correlation benchmark pack is published yet.

Commercial Tool ParityNot yet published

There is no public Verixos-vs-Thermal Desktop or Verixos-vs-ESATAN benchmark pack published today, and no completed commercial FEA pilot artifact set is published.

Regulated Deployment EvidenceFoundation in repo

ITAR workflow controls, data-residency checks, MFA hooks, self-host artifacts, GovCloud Terraform proof records, and air-gapped validation checklists exist; target-environment validation is still required before stronger claims.

IMPLEMENTED CHECKS

Verification Artifacts In Repo

These checks define the current documented validation evidence set. Some are exact analytical comparisons, some are heritage reproductions, and some are interim product benchmarks. They should not all be interpreted as the same level of external credibility.

CHECK 1.1Incropera Ch. 5

Conduction Transient

Single-node lumped capacitance cooling

0.026%RK4 error
CHECK 1.2Cengel Ch. 3

Two-Node Steady State

Coupled conduction to boundary

0.030 Kabsolute error
CHECK 1.3NASA SP-8105

Radiation Equilibrium

Solar flux / deep-space balance (3 cases)

< 1 Kall cases
CHECK 1.4Cengel Ch. 12

Radiation Cool-Down

T⁴ nonlinearity — pure radiative transient

0.0014%RK4 error
CHECK 1.5Incropera Ch. 13

Parallel Plates Radk

Grey-body radiation conductor

0.0000%exact match
CHECK 1.6Howell catalog

Enclosure Closure

View factor sum rule Σ Fᵢⱼ = 1

0.002%row-sum error
CHECK 1.7Incropera radiation shields

Radiation Shield Enclosure

Three-surface diffuse-gray shield equilibrium

< 0.05 Kshield temp error
CHECK B9Repo benchmark

Heat Pipe Conductor Curve

Piecewise-effective conductance benchmark at cold, nominal, and hot points

0.0039%worst ΔT error
CHECK B10Repo benchmark

Monte Carlo View Factors

Parallel disks, perpendicular rectangles, and concentric spheres

0.31%worst current error @ 1e5 rays
CHECK 2BCoating benchmark

Two-Band Optics

Material-driven α_solar / ε_IR equilibrium with coating assumptions

< 1 Kequilibrium error
CHECK V8Incropera forced convection

Forced Convection Flat Plate

Laminar air-flow heat rejection to a fixed-temperature sink

< 0.1 Ksurface temp error
CHECK V18Abaqus NAFEMS T3

Abaqus NAFEMS T3

Refined transient-conduction reproduction against the public NAFEMS T3 target

< 0.1 Krefined RK4 error
PHASE 2

SAE 961452 Parity

SAE Technical Paper 961452 (Keller & Vogel, 1996) is the foundational V&V reference for SINDA/FLUINT — the NASA/DoD standard spacecraft thermal analyzer. SINDA/FLUINT achieved < 0.5% agreement on all cases.

This is legitimate analytical parity evidence for the lumped thermal core. It is not the same thing as published parity against Thermal Desktop, ESATAN-TMS, NASTRAN thermal, or Abaqus thermoelastic cases.

CASESAE-1Conduction transient (t = τ)SINDA< 0.5%VERIXOS0.026%✓ Exceeds
CASESAE-1Conduction transient (t = 5τ)SINDA< 0.5%VERIXOS0.0004%✓ Exceeds
CASESAE-2Two-node steady-state (T₁)SINDA< 0.5%VERIXOS0.030 K abs✓ Exceeds
CASESAE-2Two-node steady-state (T₂)SINDA< 0.5%VERIXOS0.024 K abs✓ Exceeds
CASESAE-3Radiation transient T⁴ (500 s)SINDA< 0.5%VERIXOS0.0014%✓ Exceeds
CASESAE-3Radiation transient T⁴ (1000 s)SINDA< 0.5%VERIXOS0.0011%✓ Exceeds
CASESAE-3Radiation transient T⁴ (2000 s)SINDA< 0.5%VERIXOS0.0006%✓ Exceeds
CASESAE-4Radiation conductor (parallel plates)SINDA< 0.5%VERIXOS0.0000%✓ Exceeds
CASESAE-5Enclosure closure (VF sum)SINDA< 0.5%VERIXOS0.002%✓ Exceeds
PHASE 3

PharmaSat Mission Reproduction

PharmaSat was a NASA 1U CubeSat deployed from the ISS in May 2009 (~400 km, 51.6° inclination). Its thermal behavior was modeled with SatTherm and independently validated against Thermal Desktop and on-orbit telemetry. We reproduce SatTherm’s published orbit-averaged steady-state results using a 3-node Verixos model.

Structure
Verixos18.1 °C
SatTherm17.5 °C
± 0.6 K
PCB / Electronics
Verixos22.1 °C
SatTherm27.5 °C
± 5.4 K
Battery
Verixos18.1 °C
SatTherm20.0 °C
± 1.9 K

This is a documented flight-heritage reproduction chain, not a direct ingest of public raw NASA telemetry into Verixos. SatTherm itself agreed with the flight-validated Thermal Desktop model to within 4 °C, and Verixos falls within 5.4 K of SatTherm’s published midrange values for this simplified model tier.

CLAIM BOUNDARIES

What We Can And Cannot Claim Today

This section defines the boundary between what Verixos can support and substantiate today and what still requires broader external evidence or higher-fidelity validation.

We Can Claim
Strong analytical verification for the lumped thermal core across the implemented benchmark set.
SAE 961452 analytical parity evidence against the SINDA/FLUINT benchmark family.
A documented PharmaSat flight-heritage reproduction chain with explicit assumptions and limitations.
Narrow published-tool parity for named public cases: Abaqus NAFEMS T3 and the NASA/NASTRAN washer conduction problem.
Exact NASTRAN / Abaqus temperature handoff artifacts when imported structural provenance exists.
We Do Not Claim Yet
Broad Thermal Desktop parity across representative spacecraft models.
Direct ESATAN-TMS parity.
Validated thermal-structural deformation or stress truth without external FEA comparison and hardware correlation.
General flight-correlation credibility across multiple public missions.
A completed commercial NASTRAN or Abaqus customer pilot published as validation evidence.
TRANSPARENCY

Known Limitations

We believe transparency builds trust. These are the areas where current product capability, validation maturity, or published external evidence still has meaningful boundaries.

MLI blanket modelingHighVerixos includes MLI blanket abstractions and trade-study foundations, but high-fidelity blanket prediction is not yet externally validated to a production-credible standard.
Fluid loops / pumped coolantHigh*This is outside the intended scope of Verixos. The product is focused on lumped conduction / radiation / convection workflows, not CFD or pumped-fluid thermal control.
Heat pipe physics depthMediumVerixos includes heat-pipe conductance curves and operating-envelope inputs, but not a fully validated two-phase device model with startup, orientation, and detailed transport-limit truth.
Contact conductance certaintyMediumContact conductance is supported as an engineering input, but interface values still depend heavily on assumptions unless they are bracketed by test or hardware correlation.
Full spectral radiation truthLow–MedTwo-band and temperature-aware optics are supported, but full spectral temperature-dependent radiation is not yet validated to a higher-fidelity production standard.
Thermoelastic structural truth predictionMedium–HighThermoelastic summaries and Abaqus / NASTRAN handoff workflows are implemented, but structural displacement / stress truth still requires external FEA comparison and benchmark or hardware correlation.
Broad Thermal Desktop / ESATAN parityMediumNarrow public-reference parity exists for named cases, but broad benchmark packs against Thermal Desktop and ESATAN-TMS are not yet published.
Broad public flight correlation evidenceMed–HighVerixos includes flight-correlation tooling and named review anchors, but multiple public direct-telemetry correlation cases are not yet published as broad external evidence.

*High for mission classes that depend on active thermal control loops rather than lumped conduction / radiation / convection alone. This is a known limitation, it is outside the intended scope of Verixos, and it is not part of the product’s current planned implementation direction.

NEXT EVIDENCE

External Validation Targets

These are the next credibility milestones for Verixos: broader published commercial-tool comparisons, documented hardware-correlation case studies, and additional public flight or heritage evidence that can be reviewed with full technical context.

Thermal Desktop Public BenchmarksPlannedSimple spacecraft box and deployed-array parity cases from published C&R material or equivalent public cases.
Abaqus Thermoelastic BenchmarksUnderwayAbaqus NAFEMS T3 is reproduced in the current evidence set; thermoelastic thermal-expansion artifact and analytical reference are scaffolded next.
NASA / NASTRAN Thermal Sample ProblemsUnderwayThe washer conduction problem from the NASA NASTRAN demonstration manual is reproduced in the current evidence set; structural-deck acceptance is still a later step.
TVAC Correlation ArticlePlannedInstrumented hardware article with mapped channels, residuals, posterior uncertainty, and report traceability.
Public Flight Correlation CasePlannedFASTSAT-HSV01 or similar public mission with enough orbit and temperature context to support a defensible comparison.
REFERENCES

Citations

  1. [1]NASA-STD-7009, Standard for Models and Simulations, credibility assessment framework.
  2. [2]ECSS-E-ST-31C, Thermal Control General Requirements.
  3. [3]Incropera, F.P. et al., Fundamentals of Heat and Mass Transfer, 7th Ed., Wiley, 2011.
  4. [4]Cengel, Y.A., Ghajar, A.J., Heat and Mass Transfer, 5th Ed., McGraw-Hill, 2015.
  5. [5]Howell, J.R. et al., Thermal Radiation Heat Transfer, 7th Ed., CRC Press, 2021.
  6. [6]Gilmore, D.G. (Ed.), Spacecraft Thermal Control Handbook, Vol. 1, 2nd Ed., AIAA, 2002.
  7. [7]NASA SP-8105, Spacecraft Thermal Control, May 1973.
  8. [8]ECSS-E-HB-31-03A, Thermal Analysis Handbook, November 2016.
  9. [9]Keller, J. & Vogel, M., "Validation of the SINDA/FLUINT Thermal Analyzer Code Using Several Analytical Solutions," SAE 961452, 1996.
  10. [10]Allison, J.D., "A Thermal Analysis and Design Tool for Small Spacecraft," SJSU Master's Thesis, 2009.
  11. [11]Allison, J.D. et al., "SatTherm," SSC09-VII-6, 23rd AIAA/USU Small Satellites Conference, 2009.
  12. [12]Dassault Systèmes Abaqus verification and benchmark documentation (public pages).
  13. [13]NASA thermal analyzer sample-problem library and thermal sample-problem reports available via NTRS.
  14. [14]NASA FASTSAT-HSV01 thermal model correlation paper (public NTRS record).

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