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Space Exploration Technologies
Falcon 1

Falcon 9 Overview


The Falcon launch vehicle family is designed to provide breakthrough advances in reliability, cost, flight environment and time to launch. The primary design driver is and will remain reliability, as described in more detail below. We recognize that nothing is more important than getting our customer’s spacecraft safely to its intended destination.

Like Falcon 1, Falcon 9 is a two stage, liquid oxygen and rocket grade kerosene (RP-1) powered launch vehicle. It uses the same engines, structural architecture (with a wider diameter), avionics and launch system.

Length: 53 m (174 ft)
Width: 3.6 m (12 ft)
Mass: 352,400 kg (777 klb)
Thrust on liftoff: 4.08 MN (918 klbf)
Falcon 9
Falcon 9

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First Stage


The Falcon 9 tank walls and domes are made from aluminum 2219, the same alloy used by the Saturn V. However, we make use of an all friction stir welded tank, the highest strength and most reliable welding technique available. Like Falcon 1, the interstage, which connects the upper and lower stage for Falcon 9, is a carbon fiber honeycomb structure. The separation system is a larger version of what is used on Falcon 1 – pneumatic pushers with pyrotechnic release bolts.

Nine SpaceX Merlin engines power the Falcon 9 first stage with 101,900 lbs-f sea level thrust per engine for a total thrust on liftoff of just under 1 Million lbs-f. After engine start, Falcon is held down until all vehicle systems are verified to be functioning normally before release for liftoff. Although in-flight failures are very rarely explosive, a Kevlar shield protects each engine from debris in the event of its neighbor failing.

Falcon 9 Engine Close Up
Falcon 9 Engines Close Up

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Second Stage


The second stage tank of Falcon 9 is simply a shorter version of the first stage tank and uses most of the same tooling, material and manufacturing techniques. This results in significant cost savings in vehicle production.

A single Merlin engine powers the Falcon 9 upper stage with an expansion ratio of 120 and burn time of 265 seconds. For added reliability of restart, the engine has dual redundant hypergolic igniters (TEA-TEB) with four injection ports.


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SpaceX Merlin Engine


Merlin Engine

The main engine, called Merlin, was developed internally at SpaceX, but draws upon a long heritage of space proven engines. The pintle style injector at the heart of Merlin was first used in the Apollo Moon program for the lunar module landing engine, one of the most critical phases of the mission.

Propellant is fed via a single shaft, dual impeller turbo-pump operating on a gas generator cycle. The turbo-pump also provides the high pressure kerosene for the hydraulic actuators, which then recycles into the low pressure inlet. This eliminates the need for a separate hydraulic power system and means that thrust vector control failure by running out of hydraulic fluid is not possible. A third use of the turbo-pump is to provide roll control by actuating the turbine exhaust nozzle.

Combining the above three functions into one device that we know is functioning before the vehicle is allowed to lift off means a significant improvement in system level reliability.

Sea Level Thrust : 102,000 lb
Vacuum Thrust: 115,000 lb
Sea Level Isp: 255s
Vacuum Isp: 304s
Thrust to weight (fully accounted): 96

With a vacuum specific impulse of 304s, Merlin is the highest performance gas generator cycle kerosene engine ever built, exceeding the Boeing Delta II main engine, the Lockheed Atlas II main engine and the Saturn V F-1.



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Designed for Maximum Reliability


The vast majority of launch vehicle failures in the past two decades can be attributed to three causes: engine, stage separation and, to a much lesser degree, avionics failures. An analysis of launch failure history between 1980 and 1999 by Aerospace Corporation showed that 91% of known failures can be attributed to those subsystems.


Engine Reliability


Falcon 9 has nine Merlin engines clustered together. This vehicle will be capable of sustaining an engine failure at any point in flight and still successfully completing its mission. This actually results in an even higher level of reliability than a single engine stage. The SpaceX nine engine architecture is an improved version of the architecture employed by the Saturn V and Saturn I rockets of the Apollo Program, which had flawless flight records despite losing engines on a number of mission.

Another notable point is the SpaceX hold-before-release system – a capability required by commercial airplanes, but rarely seen on launch vehicles. After first stage engine start, the Falcon is held down and not released for flight until all propulsion and vehicle systems are confirmed to be operating normally. An automatic safe shut-down and unloading of propellant occurs if any off nominal conditions are detected.


Stage Separation Reliability


Here Falcon takes advantage of simplicity by having two stages and therefore only one stage separation event – the minimum practical number. Moreover, the stage separation bolts are all dual initiated, fully space qualified and have a zero failure track record in prior launch vehicles.


Avionics Reliability


Falcon 9 will have triple redundant flight computers and inertial navigation, with a GPS overlay for additional orbit insertion accuracy. We have gone the extra mile in building a first class avionics system to provide small and medium class satellites with the same avionics quality enjoyed by multi-billion dollar large satellites.


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Fairing Volume


Below are the standard fairing dimensions for Falcon 9. Dimensions are in meters and in inches inside the parentheses. Drawings are not to scale in relation to one another. Custom fairings in larger lengths and diameters are available at incremental cost.

Falcon 9 - 3.6 m fairing
Falcon 9 - 3.6 m fairing
Falcon 9 - 5.2 m fairing
Falcon 9 - 5.2 m fairing

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Pricing and Performance


SpaceX offers open and fixed pricing that is the same for all customers, including a best price guarantee. Modest discounts are available for contractually committed, multi-launch purchases.

Falcon 9 will offer the lowest cost per pound/kilogram to orbit, despite providing breakthrough improvements in reliability. A half bay flight of Falcon 9 is available to accommodate customers with payloads in between Falcon 1 and 9.

A user's guide will also be available for Falcon 9 later this year.  We would be glad to run a customized trajectory analysis for your spacecraft at no charge, simply email us at FalconGuide@spacex.com.


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