"The CH-5 may come in at less than half of the price," said Wang, who was deputy chief designer of a Chinese military drone but not directly involved in the Rainbow project.
The Rainbow series, ranging from the tiny model 1 to the three-tonne model 5, was developed and produced by the China Aerospace Science and Technology Corporation, the company behind the space programme. Rainbows have been sold to more than a dozen countries, with annual production exceeding 200 units, and are the "most popular military drones in the world", according to the company's website.
However, the initial output of the CH-5 would be relatively small, Wang said. It could be more than 10 units a year, but was unlikely to exceed 20 due to the size and sophistication of the aircraft.
"This should meet the early demand," Wang said.
The Rainbows are mainly for the overseas market.
In 2015, the Iraqi Ministry of Defence released a video showing a missile attack on an Islamic State target by a CH-4B drone, which is just a third of the size of the CH-5.
The CH-5 can carry up to 16 air-to-ground missiles and stay in the air for nearly two days, said Shi Wen, the chief designer of the drone, in an interview with Global Timeslast year.
After being modified for certain missions, it can fly for up to 120 hours, giving it a range of more than 10,000km.
This endurance enabled the drone to fly to a target 3,000km away and stay overhead for up to 20 hours, Shi told the state-run newspaper.
Such performance "leaves the Predator series in the dust", he added.
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The CH-5 has other advantages. For instance, it could be operated by an undergraduate student with basic knowledge of aviation after only one or two days of training, according to state media reports. This was because of the simplicity of its user interface, and the fact that operations like take-off and landing could be automated.
The drone can also be modified to be a low-cost airborne early warning system, or equipped with high-tech sensors such as wall and ground-penetrating radars developed by China.
However, Wang said the Chinese drone had a weakness compared to its American counterparts. The Reaper can climb to a height of between 12,000 and 15,000 metres. This allows the US drone to stay above the reach of most ground fire.
The CH-5, on the other hand, cannot operate at more than 9,000 metres, which makes it vulnerable to some anti-aircraft weaponry.
The limited ceiling of the Rainbow is a by-product of its relatively weak engine, according to Wang, who noted that China still lagged behind the West in aircraft engine technology.
"This is in fact the weakness of all China-made aeroplanes," he said.