Falcon X

Falcon X is was a proposed spaceflight launch system that uses rockets designed and manufactured by SpaceX. Like the Falcon 1 and Falcon 9 the first stage of this two-stage-to-orbit vehicle would of used liquid oxygen (LOX) and rocket-grade kerosene (RP-1) propellants and was intended to be reusable.^[4] The second stage would use liquid oxygen (LOX) and liquid Hydrogen (LH2) and be powered by the Raptor engine.

Falcon X

Function	Re-usable orbital launch vehicle
Manufacturer	SpaceX
Country of origin	United States
Size
Height	55 m (180 ft)
Diameter	6.0 m (19.7 ft)
Stages	2
Capacity
Payload to LEO	Normal: 38,000 kg (84,000 lb) Heavy:125,000 kg (276,000 lb)
Launch history
Status	Proposed
Boosters (Falcon X Heavy)
No. boosters	2
Engines	3 x Merlin 2
Thrust	3,600,000 lbf (16,000 kN)(sl) [1]
Specific impulse	Sea level: 285 sec (- kN/kg) Vacuum: 321 sec (- kN/kg)[2]
Burn time	Unknown
Propellant	LOX/RP-1
First stage
Engines	3 x Merlin 2
Thrust	3,600,000 lbf (16,000 kN)(sl)[1]
Propellant	LOX/RP-1
Second stage
Engines	1 Raptor
Thrust	150,000 lbf (670 kN) [2]
Specific impulse	Vacuum: 470.1 sec (- kN/kg)[3]
Burn time	345 seconds[citation needed]
Propellant	LOX/LH2

Multiple variants were planned with payloads to low Earth orbit of up to 38,000 kilograms (84,000 lb) for the basic version and up to 125,000 kilograms (276,000 lb) for the 3 core heavy, placing the Falcon X design in the heavy-lift to super heavy-lift range of launch systems.^[3]

Design

The proposed base Falcon X would of been a two stage, LOX/RP-1, LOX/LH2, fueled launch vehicle. Its first stage would be powered by 3 SpaceX Merlin 2 rocket engines with 5.3 MN (1.2M lbf) sea-level thrust per engine for a total thrust on liftoff of approximately 16 MN (3.6 million lbf).^[5] The Falcon X first stage would likely of used a pyrophoric mixture of triethylaluminum-triethylborane (TEA-TEB) as a first-stage ignitor, as does the Falcon 9.^[6]

The cancelled Falcon X Heavy configuration consists of a standard Falcon X with two additional Falcon X first stages acting as liquid strap-on boosters,^[3] which is conceptually similar to EELV launchers such as the Delta IV Heavy and the future Atlas V HLV, and also to the Russian Angara carrier rocket.

The upper stage would be powered by a single Raptor engine which would use LOX/LH2, with an expansion ratio of 250:1 and throttle range of 50-100%. For added reliability of restart, the engine has dual redundant pyrophoric igniters (TEA-TEB).^[5] SpaceX had expressed hopes that both stages will eventually be reusable.^[4]

Initial descriptions

At an appearance in May 2004 before the U.S. Senate Committee on Commerce, Science and Transportation, Elon Musk testified, "Long term plans call for development of a heavy lift product and even a super-heavy, if there is customer demand. [...] Ultimately, I believe $500 per pound [of payload delivered to orbit] or less is very achievable."^[7]

SpaceX formally announced the Falcon X on 2010-07-28. A Falcon X medium was described as being capable of launching approximately 38,000 lb (17,000 kg) to low Earth orbit.

See also

• Kestrel
• Merlin
• Raptor
• Falcon 1
• Falcon 5
• Falcon 9
• Falcon XX