As evidenced by the Chelyabinsk and Tunguska airburst events in Russia, decameter-scale Near-Earth Objects (NEOs) can pose a hazard to human life and infrastructure from the energy they deposit in the atmosphere as they break up. To understand the potential damage these small NEOs can cause on Earth's surface, it is imperative to be able to model their atmospheric entry quickly and accurately. This thesis investigates different numerical techniques used to model atmospheric entry.

Firstly, three semi-analytical continuous fragmentation airburst models (CFMs), which differ in their description of fragment spreading, are compared. The models are calibrated to the Chelyabinsk event and then upscaled to Tunguska where the results diverge. This inter-model uncertainty compounds the large range of uncertain physical and model parameters that influence meteoroid probabilistic hazard assessment. Secondly, uncertainty quantification of airburst energy deposition was performed for a theoretical impacting object with H-magnitude 27, assuming no prior knowledge of any other impactor or model parameter. Each of the three models produces a different distribution of airburst outcomes, however, the variation attributable to physical parameter uncertainty is far larger than the inter-model differences. To constrain the initial conditions of the Tunguska event, the same uncertainty quantification was performed for a H-magnitude 24 event. Thirdly, the iSALE hydrocode is modified to simulate the atmospheric entry of meteoroids using a ``wind-tunnel’’ approach. Simulations of a Chelyabinsk-scale impactor are performed without strength and then with three different strength models. Results are compared with Chelyabinsk observations and results of other hydrocode simulations, and used as a synthetic data set with which to calibrate CFMs. The results suggest that the pre-entry meteoroid strength is rapidly reduced to zero during fragmentation. Finally, the set-up of the UK Fireball Network as part of the Global Fireball Observatory is described.