Equation 12 · Part 3 · Flight at the Energy Floor: Transport Selection to 2100
subscript
subscript
What this part means
The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.
Its job in the formula
A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.
Full expression→subscript→Article meaning
The passage around this formula
Jet fuel carries about 43 megajoules of chemical energy per kilogram, or roughly 11,944 watt-hours per kilogram [ 2 ] . A modern commercial lithium-ion cell, by contrast, runs 160 to 300 watt-hours per kilogram at the cell level, with specialty laboratory cells using silicon-anode and graphene-enhanced chemistries reaching a record of roughly 450 watt-hours per kilogram [ 3 ] — figures that describe a bare cell, not a certified aircraft pack, which must add cooling, structure, wiring, and safety margin on top. A widely cited 2018 estimate for a packaged aviation battery, including that overhead, put usable specific energy at around 160 watt-hours per kilogram, or about two percent of…
Learn the underlying idea
A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.
Open the illustrated subscripts: which member of a family? guide →
Sources cited in the surrounding passage
These citations provide research context; check each source for the exact claim it supports.