# Asteroid Impact Simulator - Energy, Airburst, Crater Size and Blast Radius

> Asteroid impact calculator (Collins et al. 2005): energy in Mt TNT, airburst or crater, crater size, fireball, earthquake, blast radius and tsunami.

- URL: https://qilingtools.com/en/physics/asteroid-impact
- Category: Physics Tools (https://qilingtools.com/en/physics)
- Tags: [Physics](https://qilingtools.com/en/tags/physics), [Education](https://qilingtools.com/en/tags/education)
- Last updated: 2026-10-29
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

Set the impactor's diameter, composition (ice, rock or iron), entry speed, angle and target (land or ocean). Following the Earth Impact Effects Program equations of Collins, Melosh and Marcus (2005), the tool works out atmospheric breakup and airburst, impact speed, transient and final crater size, fireball and thermal radiation, seismic magnitude, blast overpressure and wind, ejecta thickness and, for ocean impacts, a rough tsunami height. Results are shown as concentric effect rings and a true-scale crater cross-section.

## How to use

1. Pick a preset (Chelyabinsk, Tunguska, Meteor Crater, Chicxulub, an Apophis-sized what-if and more) or set diameter, density, speed and angle yourself
2. Choose a land or ocean impact, and the water depth for the ocean
3. Read the energy, whether it airbursts, the crater size, fireball radius and seismic magnitude
4. Drag the observer distance to see thermal radiation, overpressure, wind, shaking, ejecta and tsunami there, and compare with the effect rings

## Features

- Atmospheric entry with the pancake breakup model: airburst or ground impact, breakup and burst altitude, remaining speed
- Pi-scaled transient and final crater diameter and depth, simple or complex, drawn in cross-section
- Fireball radius, burn and ignition distances, blast overpressure and wind, effective seismic magnitude and intensity
- Ocean impacts: water cavity, speed at the sea floor, rough tsunami amplitude and arrival time
- Seven historical and hypothetical presets and an impact frequency vs size chart
- Plain-language explanation of every Torino scale level

## FAQ

### Why did Chelyabinsk and Tunguska leave no crater?

A stony asteroid tens of metres across hitting the air at 15–20 km/s meets a ram pressure far above the rock's strength, so it starts breaking apart tens of kilometres up. The fragments spread sideways, the cross-section grows rapidly, and within seconds most of the kinetic energy goes into the air as an airburst. Chelyabinsk burst about 30 km up and the blast that reached the ground mainly broke windows; Tunguska burst at roughly 5–10 km and flattened about 2,000 km² of forest. Neither delivered a large intact mass to the ground. Much stronger iron bodies of similar size can reach the surface, as at Meteor Crater.

### How is impact energy converted to TNT equivalent?

Kinetic energy is E = ½mv² with m = (π/6)ρL³. One tonne of TNT is defined as 4.184×10⁹ J, so one megaton is 4.184×10¹⁵ J. Because speed enters squared and diameter cubed, a 20 m rock at 19 km/s already carries about 0.5 Mt, over thirty Hiroshima bombs; ten times the diameter means a thousand times the energy, and the 10 km class Chicxulub impactor delivered about 10⁸ Mt.

### Why is the crater so much larger than the impactor?

The impactor stops almost instantly, and its kinetic energy drives a shock wave that excavates and throws out far more rock than its own volume. Under pi-scaling the transient crater diameter grows roughly as L^0.78 v^0.44, typically 10–20 times the impactor size. Small craters stay bowl-shaped (simple craters, about 1.25 times the transient diameter); above about 3 km on Earth the walls slump and the floor rebounds into a central peak, giving a wide, shallow complex crater.

### How often do impacts like this happen, and what is the Torino scale?

Frequency falls steeply with energy: Collins et al. give a mean interval of about 109 × E^0.78 years for impacts of at least E megatons. That means a Chelyabinsk-class event every few decades, Tunguska-class every few hundred to a thousand years, kilometre-sized bodies every few hundred thousand years and dinosaur-killer impacts roughly every 100 million years. The Torino scale (0–10) rates a specific object by combining its impact probability with its energy; every currently known near-Earth object is at level 0.

### How reliable are these numbers?

The tool uses widely cited semi-empirical scaling laws that are good for orders of magnitude and for comparing scenarios, usually within a factor of two, with the tsunami estimate much rougher. Real outcomes also depend on the impactor's shape and structure, local geology and terrain, population and Earth's curvature, which makes flat-Earth estimates unreliable beyond about 1,000 km. It does not model global climate effects and is not an impact warning; the Apophis and Dimorphos presets are hypothetical.

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