Where does ablation collide?

In aerospace engineering, ablation is the deliberate, controlled erosion of a sacrificial material on a spacecraft's heat shield, which chars, melts, and vaporises during atmospheric reentry so that the departing mass carries away the intense frictional heat and keeps the vehicle beneath cool. Adams's 1959 Recent advances in ablation reviewed how such ablative materials trade their own loss for thermal protection and how that loss is engineered and predicted. The referent is the designed consumption of a protective material to reject heat, quantified by recession rate and heat absorbed per unit mass, and it is a different thing from destroying heart tissue with a catheter or a glacier losing ice in summer.[1]

Unit

The mass or thickness of shield material lost per unit of heat carried away

Recovery means

Not applicable

Measured by

Characterised by surface recession rate, mass loss, and the effective heat of ablation in arc-jet and flight tests

In glaciology, ablation is the sum of all the processes that remove mass from a glacier or snowpack, chiefly surface and basal melting, sublimation, wind erosion, and the calving of icebergs, set against the accumulation of new snow. Cuffey and Paterson's The Physics of Glaciers defines ablation within the mass balance that decides whether a glacier grows or shrinks and links it to the surface energy budget that drives melt. The referent is the loss term in a glacier's mass budget, measured over a season with stakes and energy-balance models, and it has nothing to do with an engineered heat shield or the destruction of tissue in a patient.[2]

Unit

The mass of ice and snow lost per unit area over a season, in water equivalent

Recovery means

Accumulation of snow in the cold season offsets ablation; their balance sets whether the glacier advances or retreats

Measured by

Measured with ablation stakes, snow pits, and surface energy-balance models over the melt season

In clinical medicine, ablation is the intentional destruction of a small, targeted volume of tissue, most familiarly the heart tissue that generates an arrhythmia, using energy such as radiofrequency heat or freezing delivered through a catheter. Haïssaguerre and colleagues' 1998 Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins located the triggers of atrial fibrillation and showed they could be abolished by ablating them, founding modern catheter ablation. The referent is the precise, therapeutic removal of a defined tissue focus in a patient, judged by whether the abnormal activity stops, and it is unrelated to a spacecraft's heat shield or a melting glacier.[3]

Unit

The volume of target tissue destroyed to abolish an abnormal focus

Recovery means

Not applicable

Measured by

Judged by loss of the target electrical activity and by freedom from the arrhythmia on follow-up