Skip to content
Beta
Open Skalnav
Schematic render of a generic, fictional launch vehicle
Schematic · generic launcher

Less structural mass through reliable stability prediction.

Skalnav predicts the buckling knockdown of your own shell from its geometry and imperfection quality, so the wall is only as thick as it needs to be.

Peer-reviewed science, built for industry.

Open Skalnav — free Watch the film · 79 s

No login for cylinder axial & bending · Sample report (PDF)

“What is Skalnav?” has moved: Product → What is Skalnav?

“The Problem” has moved: Product → The Problem

“The MDC Shift” has moved: Product → The MDC Shift

“How it works” has moved: Product → How it works

“Capabilities” has moved: Product → Capabilities

“Feature deep-dive” has moved: Product → Features

“Method comparison” has moved: Validation → Method comparison

“MDC coverage” has moved: Validation → Coverage matrix

“MDC Levels” have moved: Engineering Services → MDC Levels

“Proof of Value” has moved: Pricing → Proof of Value

The Startup Program has moved: Pricing → Startup Program

“For large organisations” has moved: Enterprise

“For large organisations” has moved: Enterprise

“Scientific foundation” has moved: About → Team

The questions have moved: FAQ — all questions

One mechanistic method. Three shell families.

Schematic buckling pattern in a thin-walled cylinder under axial load

Cylinder

Axial compression, bending, external pressure, torsion and transverse shear, all with plasticity; combined loads and internal pressure too.

Learn more about the cylinder coverage
Schematic buckling pattern in a conical shell

Cone

Axial compression, bending and external pressure via the equivalent-cylinder approach, with plasticity; combined loads and internal pressure too.

Learn more about the cone coverage
The product

From geometry to audit-ready proof.

Skalnav with MDC as the active method and the demo barrel from the film: an unstiffened cylinder under axial compression, its dimensions in the input tree on the left, the MDC knockdown curve against Batdorf Z in the chart, and the MDC A-Basis result next to NASA SP-8007 below

  1. Define

    Enter geometry, load case and material. Cylinder, cone, sphere or torispherical head.

  2. Imperfection

    Set the imperfection amplitude w/t: the MDC knockdown and design load follow it, NASA SP-8007 does not change.

  3. Document

    Export a verification report with the full experimental evidence trail behind every number.

More than a knockdown factor.

The two limits for the demo barrel: the largest allowable shape deviation in mm and the minimum wall thickness, each shown against its design value

Fabrication tolerance

How far may the built shell deviate and still carry the load? Skalnav returns the largest shape deviation in mm and the thinnest wall that still pass.

Sizing over five mission load cases: the proposed wall thickness, the minimum reserve factor against the target, the load-case coverage and the governing case

Sizing over the whole mission

The lightest wall that carries every load case of the mission, with a reserve-factor table and what-if checks for load, imperfection and under-thickness.

The FE load import's plausibility check: a warning about one load case with negative axial force, and the shell declared in the file matching the model on screen

FE load import

Section forces or element fluxes exported from Ansys, Abaqus or Nastran as CSV, checked for frame, sign and plausibility before anything is computed.

The design, drawn as a ring, among the nearest collapse tests in a chart of knockdown factor against Batdorf Z; one test that buckled below the prediction is marked in orange

Validation Hub and Heritage Check

Your design beside real collapse tests: the nearest experiments, how similar they are, and a flag where a test buckled below the prediction.

All features See the product Sample report: the barrel from the film (PDF)
Why MDC

Three things the classical methods don’t tell you.

  • Knockdown versus imperfection amplitude, schematicNASA SP-8007 gives one knockdown factor whatever the imperfection. The MDC knockdown falls steadily as the imperfection amplitude w/t grows: well above SP-8007 for a well-made shell, down to or below it for a poorly made one.imperfection w/t →knockdownMDCSP-8007well madepoorly made

    Imperfection Sensitivity

    Small geometric deviations (weld distortion, out-of-roundness, dent) drive shells far below their classical buckling limit. SP-8007 uses one knockdown whatever the fabrication; MDC follows the imperfection you actually have.

    Learn more
  • Knockdown versus shell length, schematicThe SP-8007 knockdown factor depends on the radius-to-thickness ratio only, not on the length. The MDC knockdown changes with the Batdorf slenderness Z: short shells keep more of their classical strength, long shells less.shell length (Batdorf Z) →knockdownMDCSP-8007shortlong

    Regime Analysis

    Short, intermediate, long — the slenderness Z decides whether a shell buckles over its whole length or locally. SP-8007’s knockdown factor depends on R/t only; MDC reads it at your Z.

    Learn more
  • Collapse stress from stocky to slender walls, schematicBoth methods end at the yield stress for a stocky wall. SP-8007 applies plasticity as a separate factor, independent of the imperfection; MDC couples yielding with the imperfection, so its curve rounds the transition where both act together.wall: stocky ← → slendercollapse stressyieldMDCSP-8007transition

    Plasticity Correction

    Stocky walls yield before they buckle. SP-8007 applies plasticity as a separate factor; MDC couples it with the imperfection, where both act together.

    Learn more
MDC beside the classical routes
CriterionMDCNASA SP-8007GMNIA / FEM
Time to resultSecondsMinutesDays to weeks
Knockdown fromFE Monte-Carlo fitOne empirical curveAnalyst’s model
ImperfectionYour fabrication class1960s test articlesAnalyst-defined
Checked againstCurated collapse tests1930s–60s testsPer project
ExpertiseDesign engineerChart lookupNonlinear-FE specialist
Full method comparison
Industries

Built for shell buckling across industries.

Schematic · deformation ×80

Aerospace

Launcher tanks and interstages under axial compression + bending.

Explore aerospace
Schematic · deformation ×20

Wind Energy

Suction-bucket skirts under installation suction, with bedded end support.

Explore wind energy
Schematic · deformation ×20

Civil Engineering

Steel silos and tanks under self-weight, bulk-solid and vacuum loads.

Explore civil engineering
Schematic buckling patterns

Pressure Vessels

Cylindrical and spherical vessels under internal / external pressure.

Explore pressure vessels
Explore all industries
The film

Skalnav in action.

79 seconds, no sound — why imperfections decide the buckling load, what Skalnav does with them, and what that can mean for the wall.

Download the sample report for this barrel (PDF)
Evidence

Checked against 1,500+ collapse tests.

Where the database holds matching tests, MDC curves are overlaid against real collapse measurements — and every record is traceable to its source publication.

  • 400+of them check the plasticity correction, which is fitted to FE campaigns
  • 60+ yearsof published collapse experiments behind the records
  • A · B · Meanstatistical design bases on every result
The Validation Hub coverage map for cylinder, cone, sphere and torisphere: the load cases with curated collapse-test data, and those still planned
Peer-reviewed methodology

H. N. R. Wagner, C. Hühne, R. Khakimova, S. Niemann, M. Wang, J. Zhang. “Structured chaos: redefining the design of buckling-critical cylindrical shells.” Proceedings of the Royal Society A, 481(2321), 2025.

DOI: 10.1098/rspa.2025.0196
Founder

Dr.-Ing. Heinz Wagner

Founder & Technical Lead

Structural engineer with 15+ years of shell-buckling research and regulated-industry validation. Doctorate awarded by TU Braunschweig (2018). Lead author of the MDC methodology paper in Proceedings of the Royal Society A (2025).

Meet the team

See the validation

Pricing

Priced for engineering value, not calculation count.

Every commercial licence runs the same released engineering core. Prices are per year, excl. VAT.

Explorer

Free

No login

First look at Skalnav: cylinder axial and bending in your browser.

Try now

Professional

€9,900 / year

excl. VAT · 1 named user

For structural engineers and specialist consultants who use shell-buckling analysis as part of professional design work.

Evaluate Skalnav

Team

€29,900 / year

excl. VAT · up to 5 named users

For engineering teams that want one shared basis for shell-buckling decisions.

Evaluate Skalnav for your team
Compare all plans Academic · Enterprise · Proof of Value · Startup Program
Engineering Services

Independent review, verification and method development for critical shell-buckling decisions — led by Dr.-Ing. Heinz Wagner.

See Engineering Services
Get started

Quantify the margin your structures really have.

Size each wall with a knockdown for its own shell, with full traceability. Start in the free Preview mode — no commitment, no credit card.

Open Skalnav — free Book a technical walkthrough
Read the publication — Proc. R. Soc. A, 2025