Editing Falcon 1

The [[SpaceX]] ''' Falcon 1''' is a semi-reuseable launch vehicle. It made it's first (and so far only) launch 24th March, 2006, and was destroyed shortly afterwards.

The first stage is powered by one [[Merlin]] engine and the second stage uses a single [[Kestrel]] engine.

First Stage. The primary structure is made of a space grade aluminum alloy in a patent pending, graduated monocoque, common bulkhead, flight pressure stabilized architecture developed by SpaceX. A single SpaceX Merlin-1A engine powers the Falcon -I first stage. After engine start, Falcon is held down until all vehicle systems are verified to be functioning normally before release for liftoff. The first stage returns by parachute to a water landing, where it is picked up by ship in a procedure similar to that of the Space Shuttle solid rocket boosters.
Second Stage. The tank structure is made of aluminum-lithium, an alloy possessing the highest strength to weight ratio of any aluminum and currently used by the Space Shuttle External Tank. A single SpaceX Kestrel engine powers the Falcon -I upper stage. For added reliability of restart, the engine has dual redundant torch igniters. Helium pressurization is again provided by composite over wrapped inconel tanks from Arde. However, in this case the helium is also used in cold gas thrusters for attitude control and propellant settling when a restart is needed.

SpaceX Merlin Engine. The main engine, called Merlin-1A, 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. With a vacuum specific impulse of 304s.
An upgraded version with the regeneratively cooled Merlin-1B engine and increased performance will be introduced in 2009.
SpaceX Kestrel Engine. Kestrel, also built around the pintle architecture, is designed to be a high efficiency, low pressure vacuum engine. It does not have a turbo-pump and is fed only by tank pressure.
Kestrel is ablatively cooled in the chamber and throat and radiatively cooled in the nozzle, which is fabricated from a high strength niobium alloy. As a metal, niobium is highly resistant to cracking compared to carbon-carbon. An impact from orbital debris or during stage separation would simply dent the metal, but have no meaningful effect on engine performance. Helium pressurant efficiency is substantially increased via a titanium heat exchanger on the ablative/niobium boundary.
Thrust vector control is provided by electro-mechanical actuators on the engine dome for pitch and yaw. Roll control (and attitude control during coast phases) is provided by helium cold gas thrusters.
The engine has dual redundant torch igniters, tested in vacuum, to ensure a reliable engine start. Since the igniters use the same propellants as the main engine, they are capable of as many restarts as necessary for a particular mission. In a multi-manifested mission, this allows for drop off at different altitudes and inclinations.



Elon Musk's SpaceX Falcon 1 failed to reach orbit during its second flight on March 21, 2007. Flight control was lost about 2 minutes 10 seconds into the vehicle's second stage burn. It was the second Falcon 1 launch failure.

The 27.526 tonne, two stage launch vehicle rose on 34.92 tonnes of lift-off thrust from its Merlin LOX/Kerosene first stage engine. First stage burnout occurred 168 seconds after lift-off at an altitude of 75 km and a velocity of 2,600 meters per second. The second stage pressure-fed LOX/Kerosene 3.175 tonne thrust Kestrel engine ignited five seconds after first stage cutoff, beginning a planned burned of about 415 seconds duration intended to insert the stage into an initial 330 x 685 km x 9 deg initial orbit about 585 seconds after lift-off. 
As it turned out, the second stage only achieved suborbital velocity (probably less than 4,000 meters per second), reaching a 300 km apogee before falling back into the Pacific Ocean east of the Marshalls.