Rocket launch

The rocket launch is the first phase of the flight of a rocket. While rocket launches do not require great preparation for sounding rockets or fireworks and limited short-range missiles during military essentially on the precise alignment, they must in space consuming tests and calculations precede. This is due to

• Aspects of security, because launchers for satellites or spaceships have a very large take-off mass and highly explosive fuels,
• The high cost of payload that is lost in a false start i A.
• The even higher security of manned spaceflight.

Less elaborate preparations to start, but similar control technology require far-reaching missile weapons such as medium-and long -range missiles - see there.

• 3.1 rockets and security
• 3.2 trajectory and attitude control
• 3.3 history

Principle of a rocket launch

Missiles operate on the principle of repulsion, ie by the ejection of hot gases which are formed upon ignition of the fuel and the oxidant and escape at high pressure through the Laval nozzle in Raketenfuß. In contrast to a rocket aerodynamic missile operates independently of the gas of the atmosphere, but it is affected in the piercing of the resistance of which depends mainly on the speed and the decreasing upward air density.

The rocket thrust must be greater than the starting weight; the greater the difference, the more rapid the missile altitude gains. The burning time of the rocket used for space ( the first of which types of military ICBMs were ) or the individual rocket stages is a few minutes. With increasing speed, the aerodynamic load of the missile structure increases. The point at which the load is at its maximum is denoted by Q Max. In the further course of flight aerodynamic load decreases again, because the air pressure is reduced in the higher layers of the atmosphere.

After piercing the dense layers of the atmosphere the rocket in the horizontal direction must be deflected as to achieve an orbit a horizontal speed of at least 7.8 km / s is required ( first cosmic or circular velocity, usually referred to as v0 ). To reach another celestial body is at least the second cosmic velocity required ( v2), the / s is 200 km above the Earth ( lowest possible orbit ) at 11 km. Overall, however, the missile has a few km / s speed more because of air resistance and the earth's gravitational field have a braking effect.

A rocket launch should take place as close to the equator, and to the east, there is then the speed advantage through the Earth's rotation is the greatest.

Speeds above 4 km / s are not directly obtainable with conventional fuels, but only with stage rocket. The second stage sits on top of the first and represents their payload, which continues accelerated after the end of firing the lower level and shedding their flight. Here, the rates of the individual steps add up according to the Rocket Equation.

The top (second or third) stage rocket carrying the payload - the / to starting earth satellites, interplanetary spacecraft (each protected by a shell ) or the capsule with the crew. , The load reaches its intended final speed, it is separated from the upper stage; then both fly on an almost identical path, but the burnt- missile envelope strongly slowed by the particles of the upper atmosphere as the ( compact ) payload, so it gets into a lower orbit, and the latter, " overtaken " from the bottom and after a few weeks or months in the lower atmosphere burns up. The trajectory of the payload is, however, precisely measured (see orbit determination and parking orbit ) and - brought by targeted small orbital maneuvers exactly to the planned orbit or on a transfer orbit to another celestial body - if it has control rockets.

Among the physical and technical processes in design, construction and operation of rockets see rocketry.

Launch preparations in space (Simplified)

A suitable for space rocket has thousands of individual components depends on the reliability of the success of a rocket launch. Whereas the purely technical power units and pumps of the rocket motor, the refueling of fuel and oxygen tanks, the holding device on the launch pad, etc. are numerous radio and measuring instruments required for the precise control gyro stabilization and much more. All of these systems need to start ( and beyond) are monitored in order to be interrupted in their possible failure of the launch. To this end, the count down begins a few days before the start and the last hours is becoming increasingly intense serves.

The most important sub-tasks before the rocket launch and the countdown are:

• Predicting the best launch window - ie that period, in which the spatial position of the missile base for planned path is energetically as favorable as possible (eg for the orbital inclination and perigee, extensive exploitation of the earth's rotation ). Further complicating matters is in interplanetary flights: here also the mutual position of the earth and the planet is included in the calculation, the time of day, the possible near the Moon or other celestial bodies, etc. is delayed the launch by a few days, so can " the Start close Window ".
• Weather forecast - because considerable cloudiness, precipitation or winds can threaten a start. For short-duration space flights and the weather conditions at the time of the return and landing must be suitable.
• Adjustment of fuel and other supplies to the estimated start and flight conditions
• Gentle transport of the carrier rocket to the launch pad
• Attachment to the holding device (start frame )
• Control of the payload capsule, making all connections
• The beginning of the countdown: Ongoing technical control of all rocket parts, the launch pad, etc.
• Control of energy and security systems
• Beginning and ongoing monitoring of refueling
• Leakage current, vibration and temperature tests of various kinds
• Ongoing review of radio, telemetry, instrumentation and navigation instruments
• Loading of the capsule with fragile or perishable material ( test materials, living things )
• Entry the spaceman and the beginning of their checks
• When functioning and positive review of all elements:
• Ramp-up of missile units ( pumps, etc.) and auxiliary power unit
• Push away the holding device
• Ignition and final test of the rocket motors ( throttle control )

Number of rocket launches

As of 2007 are held annually about 40-70 launches of missiles, bringing the payloads in a stable orbit or beyond. During the Cold War, the number of these launches was higher.