FALCON USER’S GUIDE Structurally, the plus y-axis and minus y-axis boosters are identical. The center core consists of thicker tank walls and carries the booster separation system. The z axis points to zenith when the vehicle is horizontal. Figure 2-3: Falcon Heavy first-stage engine layout After engine start, Falcon vehicles are held down until all vehicle systems are verified as functioning normally before release for liftoff. The Falcon vehicles’ interstage, which connects the first and second stages, is a composite structure consisting of an aluminum honeycomb core surrounded by carbon fiber face sheet plies. The interstage is fixed to the forward end of the first-stage tank. The stage separation system is located at the forward end of the interstage and interfaces to the second- stage. The second-stage tank for Falcon vehicles is a shorter version of the first-stage tank and uses most of the same materials, construction, tooling and manufacturing techniques as the first-stage tanks. A single Merlin Vacuum (MVac) engine powers the second stage, using a fixed 165:1 expansion nozzle. For added reliability of restart, the engine contains dual redundant triethylaluminum-triethylborane (TEA-TEB) pyrophoric igniters. In addition, the second stage contains a cold nitrogen gas (GN ) attitude control system (ACS) for pointing and roll control. The GN ACS is more reliable and 2 2 produces less contamination than a propellant-based reaction control system. Table 2-1: Falcon dimensions and characteristics Characteristic First Stage Core Second Stage Structure Height 70 m (229 ft) (including both stages, interstage and fairing) Diameter 3.66 m (12 ft) 3.66 m (12 ft) Type LOX tank – monococque; LOX tank – monococque Fuel tank – skin and stringer Fuel tanks – skin and stringer Material Aluminum lithium skin; aluminum domes Propulsion Engine type Liquid, gas generator Liquid, gas generator Engine designation Merlin 1D (M1D) MVac Engine designer SpaceX SpaceX Engine manufacturer SpaceX SpaceX Number of engines 9 1 Propellant Liquid oxygen/kerosene (RP-1) Liquid oxygen/kerosene (RP-1) Thrust (stage total) 7,686 kN (sea level) (1,710,000 lbf) 981 kN (Vacuum) (220,500 lbf) Propellant feed system Turbopump Turbopump Throttle capability Yes (190,000 lbf to 108,300 lbf sea level) Yes (220,500 lbf to 140,679 lbf) © Space Exploration Technologies Corp. All rights reserved. 7