Launch
Overview
Launch (發射) refers to the act of propelling an object in a desired direction and at a desired speed using propulsion obtained from an external source, such as the explosive force of gunpowder, compressed gas, or rocket propulsion. It is a concept applied broadly, from placing launch vehicles into orbit to the firing of missiles and guns and the staging of fireworks, and today it has become a core process of the space industry and military technology. The success or failure of a launch is determined by the interplay of the propulsion system, structural design, launch pad environment, weather conditions, and control software.
Key Content
Etymology and Concept
'Launch' (發射) is a Sino-Korean word meaning "to shoot out and send forth," and in English it is distinguished by context as launch (launch vehicles, missiles), firing (guns), discharge (electrical discharge, emission), and so on. In Korean, the "launch" of the space field and the "launch" of the military field are used as the same word, but the engineering requirements differ greatly: the former centers on orbital insertion and payload protection, while the latter centers on hit probability and survivability.
Physics of Propulsion
The basic principle of all launches is Newton's third law, action and reaction. A rocket expels combustion gases rapidly backward and is pushed forward by the reaction. The velocity required varies with the mission: the first cosmic velocity for entering low Earth orbit is about 7.9 km/s, and the escape velocity for fully breaking free of Earth's gravity reaches about 11.2 km/s. In the lower atmosphere, air resistance and the maximum dynamic pressure (Max Q) region impose structural loads, so a launch vehicle precisely controls its thrust direction and attitude while passing through this region.
Composition of a Launch Vehicle
A launch vehicle generally consists of a payload, propulsion engines, propellant tanks, guidance and control devices, and separation devices. The standard approach is the multistage rocket, which stacks several stages, in order to increase fuel efficiency by discarding stages whose combustion has ended and thereby reducing mass. Propellants are divided into liquid (liquid hydrogen, kerosene, methane, etc.) and solid; liquids are advantageous for thrust control and restarting, while solids excel in readiness and storability.
Launch Procedure
1. Assembly and inspection: Assemble the launch vehicle and payload, and verify the electrical and mechanical systems.
2. Propellant loading: Fill the tanks with cryogenic propellant while monitoring temperature and pressure.
3. Countdown: Perform a final check of each system's status and automatically hold if anything is abnormal.
4. Ignition and liftoff: After the main engine ignites, the vehicle lifts off once thrust exceeds its own weight.
5. Stage separation: Separate each stage at the end of its burn and ignite the next stage.
6. Orbital insertion or reentry: Eject the payload into the target orbit, or have a recoverable first stage perform a landing procedure.
If an anomaly occurs, a flight termination system (FTS) activates to prevent damage on the ground.
Major Launch Sites
Representative sites include South Korea's Naro Space Center, the United States' Kennedy Space Center, Kazakhstan's Baikonur, the Guiana Space Centre in French Guiana, China's Jiuquan and Wenchang launch sites, and Japan's Tanegashima Space Center. The lower a launch site's latitude, the more it can take advantage of Earth's rotation speed, allowing a heavier payload to be launched with the same propellant. However, because the optimal latitude varies with the satellite's orbital inclination, high-latitude launch sites are used for Antarctic and polar-orbit missions.
Launch in the Military and Industrial Fields
In the military field, launch includes ballistic missiles, cruise missiles, air-defense missiles, and naval and field artillery fire. Range, accuracy, and survivability are the key metrics, and in recent years hypersonic glide vehicles and multiple-warhead technology have become axes of competition. In the industrial and leisure fields, fireworks, firefighting launch equipment, drone launch pads, and ejection seats apply the principles of launch.
Latest Trends
The biggest topics in the launch field in 2024–2025 are reusability and the explosive growth in launch frequency. SpaceX's Falcon 9 commercialized first-stage recovery and pushed annual launch counts to an all-time high, while Starship, a large fully reusable system, is repeatedly conducting test flights to verify orbital-class flight and recovery technology. As new launch vehicles such as Blue Origin's New Glenn, Europe's Ariane 6, and Japan's H3 take flight one after another, competition in the heavy satellite launch market has heated up again.
Based on the successive successful launches of Nuri (누리호), South Korea is expanding private-led launch vehicle development and research into reusable technology, pursuing a next-generation launch vehicle project alongside the creation of a small launch vehicle ecosystem. Meanwhile, as demand for low Earth orbit satellite internet surges — Starlink, OneWeb, and CubeSat constellations — the market for small, dedicated launch vehicles and rideshare launches has grown rapidly. Sea launch platforms and mobile launch pads are also drawing attention as ways to relieve launch site bottlenecks.
In the military field, the operational deployment of hypersonic missiles, multiple independently targetable reentry vehicles, and interceptor missile systems is expanding, and space surveillance and launch early-warning capabilities have emerged as key variables in national security. At the same time, the problem of launch vehicle debris and space debris, and the need to establish launch licensing and space traffic management norms, have emerged as international tasks.
Related Topics
- [[Launch vehicle]]
- [[Rocket]]
- [[Nuri (rocket)]]
- [[SpaceX]]
- [[Missile]]
- [[Satellite]]
- [[Naro Space Center]]
- [[Reusable launch vehicle]]