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25.03.2015
International Space Company (ISC) Kosmotras is set to launch its Russian Dnepr rocket from Dombarovsky on Wednesday, carrying the Kompsat-3A satellite for the Korea Aerospace Research Institute (KARI). The launch – which nearly fell foul of a proposed shutdown of Dnepr utilization – is scheduled for 22:08 UTC.
Dnepr Launch:
Earlier in the year, Russian media reported ongoing evaluations within the Russian space industry threatened the shutdown of the Dnepr rocket.
However, ISC Kosmotras CEO Alexander Serkin later confirmed the company would fulfill all of its commitments on launches of Dnepr carrier rockets with foreign spacecraft under currently under contract. That will result in three more launches of the rocket this year, opening with the Kompsat-3A mission.
Kompsat-3A will be a sister spacecraft to the previously launched Kompsat-3 (Arirang-3), both of which were developed by the Korea Aerospace Research Institute (KARI).
The goal of the KOMPSAT-3 project is to develop and mature the hardware using the technology obtained through the KOMPSAT-1 project and the KOMPSAT-2 project.
It aims to meet Korean satellite demand and form a technology infrastructure that will “make inroads into the world space industry at a stage when the industry is improving the capability to develop and design highly advanced remote sensing satellites,” according to KARI.
Kompsat-3 is operating at an altitude of 685 km in a sun-synchronous orbit using a payload capable of submeter class resolution.
It is expected to have a four year lifespan, following its launch on a Japanese H-2A (H-IIA) rocket in May, 2012.
The mission objectives of the KOMPSAT-3 fleet including meeting the needs for high-resolution EO (Electro-Optical) images required for GIS (Geographical Information Systems) and other environmental, agricultural and oceanographic monitoring applications.
The Dnepr rocket is a converted R-36M UTTKh missile; modified to carry satellites into orbit rather than to deploy nuclear warheads. It was developed in the 1960s as a two-stage intercontinental ballistic missile initially capable of delivering an 18 megaton nuclear warhead.
Later versions increased this capacity to a 25 megaton warhead or up to ten smaller bombs in Multiple Independently-Targetable Reentry Vehicles (MIRVs).
One variant, the R-36O, was designed as part of the Fractional Orbital Bombardment System (FOBS) to place a warhead into low Earth orbit and then deorbit it onto a target during the first revolution. FOBS-type weapons were subsequently banned under international treaty in 1979.
The specific variant of which the Dnepr is based is the R-36MUTTH. Named the “SS-18 Mod.4″ or “Satan” by Western intelligence it is also known as the RS-20B. The type was introduced in 1979 and scheduled to leave service in 2009, although some may still be operational.
The R-36MUTTH was replaced by the R-36M2, which remains in service. Dnepr rockets use the two-stage R-36MUTTH almost unmodified, with the missile’s post-boost stage – used to target the warheads – serving as the third stage of the orbital launch system.
The rocket first flew in April 1999 carrying the British UoSAT-12 satellite.
It has only suffered one failure during its career; a launch in July 2006, which came down in Kazakhstan around 74 seconds after lifting off from the Baikonur Cosmodrome with the loss of 18 satellites, after a hydraulic failure caused the vehicle to lose thrust vectoring in one of its first stage engine nozzles.
The Dnepr will launch from Site 370/13 at Dombarovsky in south-west Russia. Near the town of Yasny, Dombarovsky is located close to Russia’s border with Kazakhstan. During the Cold War the site was a major missile base with sixty four silos for the R-36. Two interceptor squadrons were also based at the facility.
Dnepr launches occur from minimally-modified R-36 silos; in addition to 370/13, two other facilities have been used by the Dnepr: Site 109/95 at the Baikonur Cosmodrome and Site 370/11 at Dombarovsky.
Once the countdown reaches zero a hot gas generator is fired, ejecting the rocket from the silo.
Once the Dnepr has left its silo the gas generator will separate from the aft end of the rocket, with a small motor mounted on one side firing to prevent it damaging the silo.
The first stage’s four RD-263 engines will ignite with the rocket in mid-air at around 20 metres (66 feet) altitude.
On at least one R-36 test flight the first stage failed to ignite, resulting in the rocket falling back into the silo and exploding.
Once the engines are burning a set of rings which attach to the outside of the vehicle will break into halves and separate.
The first stage will burn for around 98 seconds before staging. Approximately six seconds later the second stage will ignite, burning its RD-0255 engine for 168 seconds.
The forward section of the payload fairing will separate during this burn. Once the second stage burns out it will be jettisoned, with the third stage then reorienting itself to fly backwards.
The third stage of the Dnepr was derived from the Post-Boost Module developed for the R-36 missile.
Originally designed to fine-tune the trajectories of multiple independently-targeted warheads, the unit has its engines mounted facing forwards.
To protect the satellites from the exhaust of the RD-869 engine, the rocket is fitted with a Gas Dynamic Shield, which covers the payloads until shortly before spacecraft separation.
The third stage is not restartable, so to avoid leaving debris in the same orbit as the payload spacecraft separation occurs while the engine is still burning, with the payload ejected from the back of the stage.
Dependant on the type of payloads flying on the rocket, the fairing can be split into three segments; the upper section separating into two halves during the ascent to orbit, while the lower half then separated along with the upper payload platform shortly before the satellites – as is sometimes the situation with numerous micro-satellites are riding along with the primary payload – on the lower platform began to be deployed.
Once the payload has been separated the upper stage continues to burn to depletion, leaving it in a higher orbit and minimising the risk of collision with one of the payloads.
Quelle: NS
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Update: 26.03.2015
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Quelle: Arirang
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