Bolide Reentry: Visualisation · Signals from the Periphery

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Event

DECAYING STAGE

Speed

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Altitude

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Angular rate

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BOLIDE REENTRY · FIREBALL OR CRAFT
drag, ablation, fragmentation · no thrust term
a witness sky, an integrator, six discriminators
the airship effect, computed on demand
speed bands: 11.2-72.8 km/s or ~7.8 km/s
click the lights · scrub the night · run the story

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Evidence

fact ⇄ what kind of claim · live

Drag, ablation and fragmentation govern every luminous entry

single-body meteor physics (Ceplecha et al. 1998) · integrated as written

MEASURED

Entries hold one of two speed bands: 11.2-72.8 or ~7.8 km/s

escape speed to parabolic limit; orbital decay · textbook bounds

MEASURED

Breakup altitude reads the material: stone ~44 km, a stage ~77 km

q = ρv² against strength · three orders of magnitude apart

MEASURED

1968: the Zond IV train reported as a craft with lighted windows

Hartmann's Condon analysis · the airship effect's type case

REPORTED

Chelyabinsk 2013: 19.16 km/s, peak radiance 29.7 km, ~500 kt

Popova et al. 2013; Borovička et al. 2013 · the instrumented benchmark

MEASURED

1972: a fireball crossed the sky for ~100 s and left the atmosphere

satellite-tracked grazer, perigee 57-58 km · orbit solved twice

MEASURED

A witness records angles only; distance, size and speed are assumed

the assumed-distance dial · this bench's witness scene is a drawing

MODELLED

Whether any given report was a reentry is a per-case reading

the bench computes the bounds; the file stays open

READING

View

Event

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The body

Entry speed7.9 km/s

7.8 is a decaying orbit; 11.2-72.8 is the meteoroid band. The gap between them is empty on purpose.

Entry angle1.0°

Below horizontal. Steep is seconds and violence; shallow is minutes, or a grazer that leaves.

Diameter2.5 m

With the material's density this sets the mass; mass against area decides how deep it survives.

Material

The witness

Assumed distance2.0 km

The one number no eye can measure. It alone decides whether the same track is an airliner or a bolide.

Playbackslow events play at 4x

Rate

Witness sketchthe airship the reports drew, MODELLED

Labels

Trailsafterglow along the past path

Sound-lag readoutthe free rangefinder

Two worlds · the cheats

Thrust: level offneeds a force the equations lack

Pull up / turnbreaks the straight track

Hoverbreaks the clock

Readout · live from the integrator

Event in force

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Entry speed

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Speed band

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Breakup

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Peak brightness

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Ends as

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Luminous duration

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Mass surviving

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What is measured vs modelled here

Measured: the entry equations, the speed bands, the q-against-strength breakup rule, and the 1972 and 2013 events end to end. Reported: the 1913 procession, the 1968 Zond IV letters, the 2021 evening's reports. Modelled: the witness scene, the fragment-train masses, the fireball colours, and the entire piloted panel, which is a labelled sketch. Reading: whether any particular sighting in any particular file was a reentry. The bench computes the bounds and stops there.

The entry model

Classical single-body meteor physics: drag m·dv/dt = -½CdρAv², ablation dm/dt = -ΛρAv³/2Q, luminosity I = -τ(v²/2)dm/dt, an exponential atmosphere, and the curvature term that lets shallow entries skip out. Fragmentation begins where dynamic pressure q = ρv² crosses the material's strength; after breakup the debris cloud spreads as a pancake, which is what makes the airburst flare. Dialled to Chelyabinsk's numbers it reproduces breakup near 44 km and peak brightness near 32 km against the measured 29.7.

Where this drawing takes liberties

The witness scene, ridge and house lights are drawings. The fragment train uses log-spaced masses, not a fragmentation spectrum. Colours and glow radii are display choices. The piloted panel is deliberately not integrated physics: it is the sketch the ledger breaks against. The equations, the bands, the breakup altitudes and the case quotations take no liberties.

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the witness view: play, scrub, click the lights