The need for reducing the cost of injecting payload mass into orbit is the main stimulating factor for further modifications and creation of new launch vehicles.

降低将有效载荷送入轨道的成本的需求是刺激现有运载火箭进一步改型和新型运载火箭研制的主要因素。

youdao

Having initially connected the ornithopter using a DC power source, they realized that the device could lift 1.5 grams of payload, which was roughly the mass of the batteries required for flight.

起初给扑翼机接上一个直流电源之后，他们发现这个装置的有效载荷为1.5 g，这大概可以勉强提起飞行所需的电池。

youdao

But chemical-based systems are severely limited by the fact that the vehicle mass must be made mostly of propellant, which leaves little room for the payload.

但是基于化学的推进系统被严重限制了，因为机器的质量的大部分用来给了推进剂，结果就是没怎么留下空间给装载量。

youdao

By launching closer to the equator, the rocket receives a bigger boost from the Earth's rotation, meaning it can lift nearly double the mass of a normal Baikonur payload - a maximum of three tonnes, as opposed to 1.7 tonnes, into a geosynchronous orbit 36, 000km above the Earth.

BBC: A rocket abroad - Soyuz in French Guiana