Wet dress rehearsal

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A Falcon 9 rocket during a Wet Dress Rehearsal on 1 March 2012

A wet dress rehearsal (WDR), and a more extensive static fire, are system tests of a fully integrated space launch vehicle and its associated ground support equipment (GSE) prior to launch. The spacecraft or payload may or may not be attached to the launch vehicle during the WDR or static fire, but sufficient elements of the rocket are in place to help verify that the rocket is ready for flight, allowing problems to be seen prior to the actual launch.

Wet dress rehearsal[edit]

A wet dress rehearsal is called "wet" because the liquid propellant components (such as liquid oxygen, liquid hydrogen, etc.) are loaded into the rocket during the test.[1]

Static fire[edit]

A static fire test comprises a wet dress rehearsal and goes one step farther: actually firing the engines at full thrust. The engine (or engines) is fired, while the launch vehicle is held firmly attached to the launch mount, with or without payload attached, for a few seconds in order to test engine startup while measuring pressure, temperature and propellant-flow gradients. The data gathered in such tests may be used to form a basis, upon analysis, for a unique (rocket- and engine-specific) set of criteria that will form a part of the go/nogo decision tree in the automated launch software that is used on the actual launch day, typically a few days later. Some static fire tests have fired the engines for up to seven seconds,[2] although shorter firings are more typical.

Rocket anomolies during launch pad tests[edit]

Wet rehearsal and static fire tests can fail catastrophically, as with the 1 Sep 2016 SpaceX Falcon 9 explosion,[3] which resulted from a major breach of the cryogenic helium system of the second stage rocket during the propellant-loading operations, well-prior to the planned ignition of the engines for a static fire test sequence[4][5]

References[edit]

  1. ^ "GPS IIF-2 Wet Dress Rehearsal – SpacePod 2011.06.09". Retrieved 6 July 2011. 
  2. ^ Chris Gebhardt (12 January 2016). "SpaceX Falcon 9 v1.1 conducts static fire test ahead of Jason-3 mission". NASASpaceFlight.com. Retrieved 12 January 2016. 
  3. ^ Elon Musk: Launch pad explosion is 'most difficult and complex' failure in SpaceX's 14 years LA Times September 9, 2016
  4. ^ Etherington, Darrell. "SpaceX investigation suggests helium breach caused its Falcon 9 explosion". TechCrunch. Retrieved 2016-09-26. 
  5. ^ Hull, Dana (2016-09-23). "SpaceX Sees Clue to Rocket Blast in Super-Chilled Helium Breach". Bloomberg.com. Retrieved 2016-09-26. 

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