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The Soviet R-27 SLMB propulsion
pattern for the
Iranian Safir IRILV and North-Korean Unha-2 second stages ?
Norbert Brügge, Germany
Update: 16.02.2010
It
is believed that the propulsion of the second stage of the Iranian Safir IRILV
was built on base the R-27 SLBM technology and comes now secundary from North-Korea
(or China ?). In fact, there are similarities between the R-27 and the Safir
IRILV. The nature of the turbopump and its placement into the tank and the
attachment of the two small engines on the outside of highly curved bulk are
striking. The shape of the vernier engines of the R-27 are very similar to
the Safir IRILV, but they have only a thrust of 31 kN. That is not enough
for the Safir IRILV.
Presumably, North Korea has acquired the technology from the R-27, but this
is changed dramatically. This particularly applies to the turbopump of the
R-27 and their arrangement. However, it is likely that the turbopump is also
located within the tank as in the R-27. The two small Soviet engines 4D10
has been significantly upgraded in its performance.
North Korea has probably the changed technology used in its new second stage
for the Unha-1. The Unha-1 (not the Paektusan / Taepodong-1) was tested only
once without success and is now successful in Iran as Safir IRILV in use.
North-Korea is now focused on the development of the Unha-2. The Unha-2 used
a larger version of the second stage, with about 400% more fuel. But now probably
are needed now two new engines
like for the Iranian Simorgh.
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R-27 SLBM
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The Soviet R-27
submarine-launched ballistic missile is a single-stage, storable liquid-propellant
missile. The missile was first seen publicly in a Moscow parade in 1967.
Development work resulted from a proposal by SKB-385 in late 1961 for the
development of a launch system with a light single-stage missile for strikes
against strategic land targets.
In 1962 the project was officially authorized.
One distinctive innovation in this design was the placement of the rocket
engines within the fuel tank in order to reduce the external dimensions of
the vehicle. The missile body was made of aluminium alloys, and the fuel and
two oxidizer tanks had common bottoms. The propulsion system has a single-chamber
sustainer and a dual-chamber control engine. The thrust chambers of the attitude
control engine were oriented at an angle of 45 degrees from the stabilization
axis of the missile.
| Engine |
Thrust (s.l.) |
Isp (s.l.) |
Thrust (vac) |
Isp (vac) |
Propellant |
Mass (t) |
Burn time
(sec) |
Flow rate
(t/sec) |
Total Impulse
(vac) |
| 1x Isayev |
225,6 |
2687 |
238,7 |
2844 |
UDMH/N2O4 |
12,176 |
~132 |
0,0840 |
34,6 MN*s |
| 2x Vernier 4D10 |
29,4 |
2687 |
31,1 |
~2844 |
~100 |
0,0110 |
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R-27 SLBM with 1,50 m diameter
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R-27 propulsion arrangement
R-27 Vernier engine (15 kN thrust ongly)
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Allegedly a R-27 Turbopump aggregat
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Safir IRILV
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| Engines |
Thrust (s.l.) |
Isp (s.l.) |
Thrust (vac) |
Isp (vac) |
Propellant |
Mass (t) |
Burn time
(sec) |
Flow rate
(t/sec) |
Total Impulse
(vac) |
| n.n. (2) |
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73,5 |
~2844 |
UDMH/AK-27S |
~3,876 |
150 |
0,02584 |
11,0 MN*s |
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Safir IRILV engine without nozzle extension
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Engine without and with nozzle extension
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Safir IRILV engine with nozzle extension
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Safir IRILV second stage tail
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Comparison between Unha-2, Simorgh and
Safir IRILV dimensions
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Similarities between elements of the
allegedly R-27 and the Safir turbopump units
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