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,[when?] an additional function on some flights has been to maintain the cleanroom environment for precision instruments.[clarification needed] Once outside the atmosphere the fairing is jettisoned, exposing the payload to the space environment.
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.
Traditionally, payload fairings have been expendable—fairings have either burned up in the atmosphere or were destroyed upon impacting the ocean—but this has begun to change after the mid-2010s. On March 30, 2017, SpaceX successfully retrieved a fairing intact for the first time in history. For a second time on June 25, 2019, SpaceX was able to catch a fairing from the Falcon Heavy STP-2 launch. SpaceX has said that they intend to begin reusing the fairings, that were manufactured at a cost of US$6 million per orbital launch.
Mission failures caused by payload fairingsEdit
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 crewed 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.
On February 24, 2009, NASA's Orbiting Carbon Observatory satellite failed to reach orbit after liftoff presumably because the fairing on the Taurus XL launch vehicle failed to separate, causing the vehicle to retain too much mass and subsequently fall back to Earth and land in the Indian Ocean near Antarctica.
The same happened to the Naro-1, South Korea's first carrier rocket, launched on August 25, 2009. During the launch half of the payload's fairing failed to separate, and as a result, the rocket was thrown off course. The satellite did not reach a stable orbit.
On March 4, 2011, NASA's Glory satellite launch failed to reach orbit after liftoff due to a fairing separation failure on the Orbital Sciences Taurus XL launch vehicle, ending up in the Indian Ocean. This failure represented the second consecutive failure of a fairing on an Orbital Sciences Taurus XL vehicle. NASA subsequently decided to switch the launch vehicle for the Orbiting Carbon Observatory's replacement, OCO-2, from a Taurus to a Delta II rocket.
On August 31, 2017, ISRO's IRNSS-1H satellite failed to deploy after the payload fairing of the rocket PSLV-C39 failed to separate. As a result of extra mass, the rocket could not reach the desired orbit despite each stage's performance being nominal. The payload separated internally, but got stuck within the heat shield.
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