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Launch vehicle system tests assess the readiness of a launch system to safely reach orbit. Launch vehicles undergo system tests before they launch. A wet dress rehearsal (WDR) and a more extensive static fire tests a fully assembled
launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...
and its associated
ground support equipment File:Qatar Airways Airbus A380-800 at Heathrow Airport Terminal 4 before Flying to Doha, 6 Jan 2015.jpg, Qatar Airways Airbus A380-800 on apron outside Heathrow Terminal 4 with a wide range of ground handling equipment around such as aircraft con ...
(GSE) prior to launch. The spacecraft/payload may or may not be attached to the launch vehicle during the WDR or static fire, but sufficient elements of the rocket and all relevant ground support equipment are in place to help
verify CONFIG.SYS is the primary configuration file for the DOS and OS/2 operating systems. It is a special ASCII text file that contains user-accessible setup or configuration directives evaluated by the operating system's DOS BIOS (typically residing ...
that the rocket is ready for flight. Propellant load tests and static fire tests may also be done on
prototype A prototype is an early sample, model, or release of a product built to test a concept or process. It is a term used in a variety of contexts, including semantics, design, electronics, and Software prototyping, software programming. A prototyp ...
rocket stages as well, in which case no fully assembled launch vehicle is involved.


Wet dress rehearsal

A wet dress rehearsal is called "wet" because the liquid
propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...
components (such as
liquid oxygen Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an applica ...
,
liquid hydrogen Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33  K. However, for it to be in a fully li ...
, etc.) are loaded into the rocket during the test. In a pure wet dress rehearsal the rocket engines are not ignited. Wet dress rehearsals may be used on production launch vehicles before each flight or on prototypes under
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.


Static fire

A static fire test includes a wet dress rehearsal and adds the step of firing the engines at full thrust. The engine(s) are fired for a few seconds while the
launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...
is held firmly attached to the launch mount. This tests engine startup while measuring pressure, temperature and propellant-flow gradients, and can be performed with or without payload. The data gathered in such tests may be used to form a unique (rocket- and engine-specific) set of criteria as part of the
go/no-go A go/no go test is a two-step verification process that uses two boundary conditions, or a binary classification. The test is passed only when the ''go'' condition has been met and also the ''no go'' condition has been failed. The test gives no in ...
decision tree A decision tree is a decision support tool that uses a tree-like model of decisions and their possible consequences, including chance event outcomes, resource costs, and utility. It is one way to display an algorithm that only contains condit ...
in the launch software that is used on launch day. Some static fire tests have fired the engines for twelve and even twenty seconds, although shorter firings are more typical.


Use

Many
launch service provider A launch service provider (LSP) is a type of company which specialises in launching spacecraft. In 2018, the launch services sector accounted for $5.5 billion out of a total $344.5 billion "global space economy". It is responsible for the ordering ...
s do not regularly perform wet dress rehearsals on new launch vehicles; some regularly perform wet dress rehearsals or even full static fire tests on the launch mount. For example,
SpaceX Space Exploration Technologies Corp. (SpaceX) is an American spacecraft manufacturer, launcher, and a satellite communications corporation headquartered in Hawthorne, California. It was founded in 2002 by Elon Musk with the stated goal of ...
typically performs a full static fire on every new booster and also on each reflown booster before every launch, sometimes more than once. In January 2018, SpaceX did two wet dress rehearsals on the Zuma
Falcon 9 Falcon 9 is a partially reusable medium lift launch vehicle that can carry cargo and crew into Earth orbit, produced by American aerospace company SpaceX. The rocket has two stages. The first (booster) stage carries the second stage and payl ...
mission, and conducted multiple wet dress rehearsals on the
Falcon Heavy Falcon Heavy is a partially reusable heavy-lift launch vehicle that is produced by SpaceX, an American aerospace manufacturer. The rocket consists of two strap-on boosters made from Falcon 9 first stages, a center core also made from a Falc ...
launch vehicle which had its maiden launch on 6 February 2018. Both were explicitly booked as wet dress rehearsals, but with the option to proceed to a static fire test. The second wet dress rehearsal on 24 January 2018 led to a full 12-second static fire test of the 27 engines of the Falcon Heavy — a much longer static fire test than the typical 3–7 second duration tests SpaceX uses for the Falcon 9.


Anomalies

Wet rehearsal and static fire tests can fail catastrophically, as with a pad explosion of a SpaceX Falcon 9 on 1 September 2016.Elon Musk: Launch pad explosion is 'most difficult and complex' failure in SpaceX's 14 years
LA Times September 9, 2016
The failure resulted from a major breach of the cryogenic helium system of the
second stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own engines and propellant. A ''tandem'' or ''serial'' stage is mounted on top of another stage; a ''parallel'' stage i ...
during propellant-loading operations. The explosion destroyed the
rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...
and its payload - the
AMOS-6 AMOS-6 was an Israeli communications satellite, one of the Spacecom AMOS series, that was built by Israel Aerospace Industries (IAI), a defense and aerospace company. AMOS-6 was intended to be launched on flight 29 of a SpaceX Falcon 9 to ...
satellite. Furthermore, due to extensive fire, the
SLC-40 Space Launch Complex 40 (SLC-40), previously Launch Complex 40 (LC-40) is a launch pad for rockets located at the north end of Cape Canaveral Space Force Station, Florida. The launch pad was used by the United States Air Force for 55 Titan III ...
launch pad A launch pad is an above-ground facility from which a rocket-powered missile or space vehicle is vertically launched. The term ''launch pad'' can be used to describe just the central launch platform (mobile launcher platform), or the entire ...
was heavily damaged and had to be rebuilt.


References

{{Reflist, 30em


External links


SpaceX Systems Engineering presentation from CASE 2012
28 September 2012. Includes description of SpaceX approach to fifth-level hardware-software integration testing during their wet dress rehearsal and/or static fire testing. Aerospace system testing Spaceflight concepts Tests