HY-2

The Shang You or SY-series (Chinese: 上游; pinyin: shàngyóu; literally: "Upstream"), and the Hai Ying or HY-series (Chinese: 海鹰; pinyin: hǎiyīng; literally: "Sea Eagle") were early Chinese anti-ship missiles. They were derived from the Soviet P-15 Termit missile.

The HY-1 and HY-2 received the NATO reporting name Silkworm. However, to confuse matters, Western media also referred to the SY-series, and its export derivatives, the Fei Long or FL-series (Chinese: 飞龙; pinyin: fēilónɡ; literally: "Flying Dragon"), as Silkworms.

The SY-series were developed from the Soviet P-15 Termit. They were used on small missile boats with limited electronics. The Chinese encountered difficulties making the missile compatible with the more complex systems of larger warships. This could have resulted in premature launches or detonations when the electronics were placed on full power. In response, the HY-series was designed for warships and to replace the SY-series.

The SY-series was initially produced concurrently with the HY-series to arm missile boats and to provide an inexpensive alternative for export.

This is the original Chinese version of Soviet P-15 Termit missile, and the first was SY-1, produced at Factory 320 (the Nanchang Aircraft Factory [南昌飞机制造厂]);; Chinese sources identify the designers as Li Tongli and Lu Lin. The main difference between P-15 Termit and SY-1 missiles is that the unreliable aneroid altimeter of P-15 Termit was replaced by a much more reliable radar altimeter in SY-1. The successor of SY-1, designed by Peng Lisheng (彭历生) and designated as SY-1A, had a mono-pulse terminal guidance radar seeker replacing the original conical scanning radar seeker. The missile received a NATO reporting name CSS-N-1 Scrubbrush.

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Wikipedia