Payload shroud

A payload fairing is a nose cone used to protect a spacecraft (launch vehicle payload) against the impact of dynamic pressure and aerodynamic heating during launch through an atmosphere. More recently, an additional function is to maintain the cleanroom environment for precision instruments.

Outside the atmosphere the fairing is jettisoned, exposing the payload. At this moment mechanical shocks and a spike in acceleration might be observed.

The standard payload fairing is typically a cone-cylinder combination, due to aerodynamic considerations; however specialized fairings are in use as well. The type of fairing which separates into two halves upon jettisoning is called a clamshell fairing by way of analogy to the bifurcating shell of a clam.

In some cases the fairing may enclose both the payload and the upper stage of the rocket, such as on Atlas V and Proton M.

If the payload is attached both to the booster's core structures and to the fairing, the payload may still be affected by the fairing's bending loads, as well as inertia loads due to vibrations caused by gusts and buffeting.

Since fairing is an expensive part of a launch vehicle, being able to reuse them will lower the cost of launches. On March 30, 2017, SpaceX successfully retrieved a fairing for the first time in history.

In some cases, the fairing is planned to separate after cutoff of the upper stage, and in others, the separation is to occur before a cutoff, but after the vehicle has transcended the densest part of the atmosphere. Failure of the fairing to separate in these cases may cause the craft to fail to reach orbit, due to the extra mass.

The Augmented Target Docking Adapter, to be used for the Gemini 9A manned mission, was successfully placed into orbit by an Atlas SLV-3 in June 1966. But when the Gemini crew rendezvoused with it, they discovered the fairing had failed to open and separate, making docking impossible. Two lanyards, which should have been removed before flight, were still in place. The cause was determined to be a launch crew error.

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Wikipedia