A debris fragment population produced by the NASA Standard Satellite Breakup
Model (SSBM), EVOLVE 4.0 revision.
Instances are never constructed directly — use
BreakupEvent.explosion
or BreakupEvent.collision, which invoke the model inside the
wasm-engine and copy the resulting population out of the module heap.
Every quantity on this class is derived by the model from the published equations: the fragment count comes from the power-law size distribution, area-to-mass ratios from the bimodal log-normal distributions (with distinct spacecraft and rocket-body branches), areas and masses from the A/M relation, and the ejection velocity from the log-normal ΔV distribution conditioned on A/M. Nothing here is tuned for appearance, and no consumer may substitute an invented fragment count, A/M, or ΔV.
Frames and units. The model is frame-agnostic — it adds an isotropic ΔV to whatever parent state it is given. Fragment states are therefore expressed in the same frame as the parent state supplied to the factory, and that frame must be inertial for the resulting velocities to be physical. All lengths are metres, masses kilograms, velocities metres per second, areas square metres, and area-to-mass ratios square metres per kilogram.
Members
See:
See:
Per-fragment cross-sectional area, in square metres.
Per-fragment area-to-mass ratio, in square metres per kilogram.
Per-fragment characteristic length Lc, in metres.
Number of fragments in the population.
Packed per-fragment ejection ΔV vectors
[dvx0, dvy0, dvz0, dvx1, ...], in metres per second.
readonly epoch : JulianDate|undefined
The instant the breakup occurred, when supplied to the factory.
Which fragmentation mechanism produced this population.
The mass budget the model was asked to fragment, in kilograms.
Whether the event was catastrophic. Explosions always are; a collision is
catastrophic when the projectile's specific kinetic energy on the target
exceeds the model's 40 J/g threshold, which selects a different size
distribution and fragments the combined mass rather than only the
excavated mass.
Per-fragment mass, in kilograms.
The lower characteristic-length cutoff applied to the size distribution,
in metres.
The parent object class whose area-to-mass branch was sampled.
The mass actually carried by the generated population, in kilograms.
Packed per-fragment position vectors, in metres, in
BreakupEvent#referenceFrame.
readonly referenceFrame : ReferenceFrame
The frame the parent state was expressed in, and therefore the frame every
fragment state is expressed in.
The seed that made this population reproducible, or
undefined
when the model was allowed to draw its own entropy.
Packed per-fragment velocity vectors (parent velocity plus ejection
ΔV), in metres per second, in
BreakupEvent#referenceFrame.
Methods
static Cesium.BreakupEvent.collision(options) → BreakupEvent
Generate the fragment population for a collision between a target and a
projectile, using the NASA Standard Satellite Breakup Model.
The model classifies the impact itself: when the projectile's specific
kinetic energy on the target exceeds 40 J/g the collision is catastrophic
and the combined mass fragments; otherwise only the mass the projectile
excavates fragments, and the cratered target remainder is carried as a
fragment. Inspect
BreakupEvent#isCatastrophic on the result — never
assume which regime a given encounter falls in.
| Name | Type | Description | ||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
options |
object |
Object with the following properties:
|
Returns:
The generated fragment population.
Throws:
-
DeveloperError : The wasm-engine must be initialized on the SDK artifact path.
Example:
const event = Cesium.BreakupEvent.collision({
target: {
characteristicLength: 4.0, mass: 900.0,
position: targetPositionInertial, velocity: targetVelocityInertial,
},
projectile: {
characteristicLength: 0.4, mass: 6.0,
position: targetPositionInertial, velocity: impactorVelocityInertial,
},
epoch: impactTime,
seed: 20260729,
});static Cesium.BreakupEvent.explosion(options) → BreakupEvent
Generate the fragment population for an anomalous or deliberate explosion of
a single parent body, using the NASA Standard Satellite Breakup Model.
| Name | Type | Description | ||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
options |
object |
Object with the following properties:
|
Returns:
The generated fragment population.
Throws:
-
DeveloperError : The wasm-engine must be initialized on the SDK artifact path.
Example:
const event = Cesium.BreakupEvent.explosion({
characteristicLength: 3.0,
mass: 1500.0,
objectClass: Cesium.BreakupEvent.ObjectClass.ROCKET_BODY,
position: parentPositionInertial,
velocity: parentVelocityInertial,
epoch: breakupTime,
minimumCharacteristicLength: 0.2,
seed: 20260729,
});
console.log(`${event.count} fragments, ${event.outputMass} kg`);
Whether the loaded wasm-engine artifact exposes the breakup model. The model
is only present on the SDK artifact path.
Returns:
Read one fragment out of the population.
| Name | Type | Description |
|---|---|---|
index |
number |
Fragment index, in [0, count). |
result |
object | optional Object to store the result in. |
Returns:
The fragment:
index,
characteristicLength (m), areaToMassRatio
(m²/kg), area (m²), mass (kg),
position and velocity (m, m/s, in
BreakupEvent#referenceFrame) and deltaVelocity
(m/s).
Indices of the population ordered by descending fragment mass, optionally
truncated.
Note that truncating this list keeps only the heaviest fragments, which is a
biased view of a debris cloud: fragment mass and area-to-mass ratio
are inversely related, so the heavy tail all shares a similar low A/M and the
high-A/M fragments that dominate the cloud's later evolution are exactly the
ones dropped. Prefer BreakupEvent#stratifiedIndicesByMass when
choosing a subset to display.
| Name | Type | Description |
|---|---|---|
maximumCount |
number | optional Keep at most this many indices. |
Returns:
Fragment indices, largest mass first.
A subset of the population that spans its full mass range: the fragments are
ordered by descending mass and then sampled at even intervals, so the subset
covers the heavy low-A/M tail and the light high-A/M tail alike.
This is the honest way to display a bounded number of fragments. It is a
display choice only — the population itself is never resampled or thinned,
and BreakupEvent#count remains the number the model generated.
| Name | Type | Description |
|---|---|---|
maximumCount |
number | optional Keep at most this many indices. Omit to get the whole population, largest mass first. |
Returns:
Fragment indices, largest mass first.