Tech Please: Getting up to speed with China's reusable rockets

Editor's note: "Tech Please!" takes a sideways look at all things science and technology in China, revealing trends you won't hear about anywhere else – from cutting-edge developments to the bizarre and whimsical in the world's most exciting tech market.

Reusable rockets, exemplified by the triumphs of Elon Musk's Falcon 9 with its numerous successful recoveries, are the pinnacle pursuit for maximizing cost-effectiveness in commercial space exploration. Their unparalleled cost-effective launches have left competitors setting their eyes on this lucrative domain. 

And China, with significant breakthroughs in December 2023, is emerging as a key player in this sector. First, China now has the world's first methane rocket that can actually deliver the goods; second, vertical takeoff and landing of a Chinese commercial rocket with a recycled first-stage booster has been verified.

Methane propellant is what major global players like SpaceX and Blue Origin dream about at night. For example, Starship's first stage, also known as the Super Heavy booster, is powered by methane and liquid oxygen. So far, it has not made it to orbit. 

Here's a list of the top players in China and the latest reusable rockets they're working on. There are other players who are working solely on reusable rocket engines or reusable rockets, such as JZYJ (Jiu Zhou Yun Jian) and Deep Blue Aerospace. The ones mentioned in the infographic below have other type of launch vehicles that have been put into orbit.

LandSpace's Zhuque-2 became the world's first methane-propelled rocket to fly into orbit in July. It successfully delivered three satellites in early December.

Although it is a single-use rocket, its propulsion system – engines powered by liquid methane and liquid oxygen – is what we're interested in here, because liquid propellant is a must when you start thinking up a reusable rocket. 

Think of it as adding fuel to your car as opposed to lighting up a cart with a bunch of heavy-duty Roman candles. Running on fuel allows you to control speed and even switch on and off when needed, but when it comes to fireworks, "fast" is the only way forward and the thrust stops when they burn up and fall off.

For these liquid propellants, manufacturers can choose from kerosene, methane, or simply liquefied natural gas (LNG); and liquid hydrogen.

SpaceX's Falcon 9 adopts the kerosene-based propulsion system. It is a more matured technique, but methane apparently has more advantages. 

Both methane and kerosene produces carbon dioxide (CO2) and water (H2O), but methane combustion produces fewer greenhouse gas emissions compared to kerosene. 

Additionally, methane has significant reduction of coking – the formation of carbon deposits on the rocket engine components due to the incomplete combustion of fuel. This would come in handy in the cleaning and maintenance of engines for the long-term reliability of reusable rockets.

Methane generally has a higher specific impulse compared to kerosene. This means that, for the same amount of propellant, a rocket using methane can achieve higher speeds or carry more payload.

More importantly, methane can be produced on Mars.

Remember, we're making reusable rockets to cut down costs in the hope that space travel one day will be as easy as international travel (and even that international travel can be done with reusable rockets!). So, fuel costs as well as vehicle cleaning and maintenance all need to be factored in.

Methane is widely recognized as the "most ideal propellant for the reusable launch vehicle," according to Yang Yuguang, the vice chair of space transportation committee at the International Astronautical Federation.

He said that the consecutive successful launches of Zhuque-2 represent "a very important feature" for deploying reusable launch vehicles. 

Meanwhile, there are other technologies critical to reusable rockets such as vertical lift off and landing.

That is something Interstellar Glory, or iSpace, have demonstrated in the past two months. It first recovered the first-stage booster of its Hyperbola-2 methane rocket after a flight of 178 meters. Later on, after some adjustments, the same booster went over 300 meters before being successfully recovered.

"For this process, you see that the control itself is very complex. It requires an engine which can adjust its thrust in a very wide range," Yang said.

He believes that both companies can realize the launch of reusable rocket in the future.

Scriptwriter and host: Zhao Chenchen

Copy editor: Moosa Abbas

Cameraman and post production: Zhang Rongyi

3D designer: Pan Yongzhe

Cover image designer: Liu Shaozhen

Infographics designer: Li Wenyi

Producer: Cao Qingqing

Chief editors: Wen Yaru, Wu Gang

Executive producer: Zhang Shilei