Throw-weight is a measure of the effective weight of ballistic missile
payloads. It is measured in
kilograms or
tonnes. Throw-weight equals the total weight of a missile's
warheads,
reentry vehicles, self-contained dispensing mechanisms,
penetration aids, and any other components that are part of the delivered payload, and not of the rocket itself (such as the launch
rocket booster and launch fuel). Throw-weight may refer to any type of warhead, but in normal modern usage, it refers almost exclusively to
nuclear or
thermonuclear payloads. It was once also a consideration in the design of naval ships and the number and size of their guns. Throw-weight was used as a criterion in classifying different types of missiles during
Strategic Arms Limitation Talks between the
Soviet Union and the
United States. The term became politically controversial during debates over the arms control accord, as critics of the treaty alleged that Soviet missiles were able to carry larger payloads and so enabled the Soviets to maintain higher throw-weight than an American force with a roughly comparable number of lower-payload missiles. The missiles with the world's heaviest payloads are the Russian
SS-18 and Chinese
CSS-4 and , Russia was developing a new heavy-lift, liquid-propellant ICBM called the
Sarmat. By reducing the payload weight, different trajectories can be selected, which can either increase the nominal range or decrease the total time in flight. A depressed trajectory is non-optimal, as a lower and flatter trajectory takes less time between launch and impact but has a lower throw-weight. The primary reasons to choose a depressed trajectory are to evade
anti-ballistic missile systems by reducing the time available to shoot down the attacking vehicle (especially during the vulnerable burn-phase against space-based ABM systems) or a nuclear
first-strike scenario. An alternate, non-military purpose for a depressed trajectory is in conjunction with the
spaceplane concept with use of
airbreathing jet engines, which requires the ballistic missile to remain low enough inside the atmosphere for air-breathing engines to function. In contrast, a "lofted" trajectory is frequently used for testing purposes, as it reduces the range of the missile (allowing for a controlled and observed impact), as well as signals a lack of hostile intention with the test. == Combat use ==