China's aerospace technology continues to make breakthroughs, and some private enterprises have successfully verified rocket reuse technology twice by the end of 2023, which is not only catching up with SpaceX in the United States, but is also expected to reduce the cost of rocket launch by 50% in the long run. How can rockets be recycled and reused?
The cost of the first stage rocket is high
The complete design of Hyperbola-2 adopts a two-stage rocket tandem structure, and the first and second stages use 15-ton liquid oxygen methane liquid rocket engines in the same state, but only the first stage rocket is used for verification and recovery.
To send spacecraft, satellites and other spacecraft into space, it is necessary to use carrier rockets, and the vast majority of launch vehicles are currently "disposable", which will be abandoned after launch, and the wreckage will fall to the ground or the sea after being ablated by the atmosphere.
The advantage of discarding the rocket is that the design is relatively simple, and problems such as materials are easier to solve. But it also has its own drawbacks, the most prominent of which is the high cost.
The launch cost of the US SpaceX Falcon 9 rocket is reported to be more than $60 million. Chinese rockets may be a little lower, but they are not cheap either. The proportion of fuel in the launch cost is very low, less than 0.5% for the Falcon 9, and more than 80% for rocket hardware, of which the first stage rocket accounts for the largest proportion.
Many launch vehicles are composed of several stages of rockets, starting from the first stage at the bottom, each stage falls off after the fuel is used up to reduce its own weight, while the next stage rocket engine starts to work and continues to accelerate into the sky.
The premise of reuse is recycling
The first stage rocket has the highest cost and the most reusable value. The picture shows the recovery process of the first stage rocket.
Because of the high cost of rocket hardware, aerospace experts have been looking for ways to make it recyclable and reusable, with the first stage rocket, which accounts for the largest proportion of the cost.
According to Falcon 9, the cost of the first stage of the rocket for post-recovery and repair inspection is about $9.1 million, which is much cheaper than the first stage of the rocket that is used up and discarded.
Having said that, rockets are to be reused, and the premise is naturally to be able to recycle. At present, there are roughly three ways for countries to study rocket recovery: parachute recovery, winged recovery and vertical recovery.
Parachute recovery is roughly a deceleration landing with a parachute at low altitude after the first stage rocket has been detached, or a helicopter hooked in mid-air and brought back to the ground. This approach is not yet fully implemented.
Vertical recycling is the mainstream practice
Although the Hyperbola 2 used for verification only has the first stage, it is also a full-size design.
Wing recovery simply means adding a wing booster to the first stage of the rocket, allowing it to glide and land like an airplane after it has been detached. This method is not too difficult, but because of the need to increase the wings, landing gear and other structures, the associated weight will cause the rocket to lose about 40% of its carrying capacity.
Vertical recycling is currently the most mainstream approach, and the "Blue Origin" and "SpaceX" of the United States are taking this route.
Specifically, after the first-stage rocket falls off, it must be ignited again to adjust the attitude and trajectory, and finally ignited and thrust reverser to slow down, and realize landing in a vertical attitude on an onshore or offshore platform.
The advantages of this method are high landing accuracy, minimal changes to the rocket structure, and the most economical benefits.
It is very difficult for China's aerospace industry to be involved in control and other issues
However, it is also extremely technically difficult, involving ballistics, aerodynamics, controls, engine materials, and multiple ignition, which very few people can master.
In December 2015, SpaceX launched 11 small communication satellites on a Falcon-9 rocket after several tests, and successfully recovered them vertically, which was the world's first practical recovery case. As of September 2022, it has successfully recovered more than 130 first-stage rockets, one of which has been reused 14 times.
The Blue Origin practical recovery rocket was about a month earlier than SpaceX (November 2015), but its rocket is a suborbital rocket that does not have the ability to put spacecraft into orbit, and its subsequent development is also slow.
As for the small verification rocket "Hyperbola-2" of the Chinese private enterprise "Interstellar Glory", it made its first flight in Jiuquan on November 2, 2023, and was vertically recovered, which is the first time that China has successfully conducted a similar test.
China Aerospace flies 178 meters high and translates 50 meters
In this test, the Hyperbola-2 used only the full-size first-stage rocket (about 17 meters high and 3.35 meters in diameter), without the second stage and other vehicles, and flew at an altitude of 178.42 meters.
By December 10, the recovered "hyperbola-2" was re-launched after trimming and testing, with a height of 343.12 meters, lasting 63.15 seconds, and moving laterally by 50 meters, with a landing speed of 1.1 meters per second and an accuracy of about 0.295 meters.
These two tests verified a series of technologies such as take-off, engine thrust change, landing, and recovery.
Of course, this cannot be compared with the practical operation of the "Falcon-9", but it must be known that the "Grasshopper" rocket, which was used by "SpaceX" to verify the reuse technology, only rose 1.8 meters in the first successful test in 2012, and only flew 17.7 meters in the second test in the same year. In contrast, the "hyperbola II" started not low.
China Aerospace can be reused up to 30 times
The "hyperbola-2" verification rocket took off for the second time, and in addition to flying more than 300 meters high, it also translated 50 meters before landing.
Incidentally, the Hyperbola-2 uses an engine fueled by liquid oxygen methane, which is the most suitable engine for reusable rockets.
In an interview with the media, He Guanghui, commander-in-chief of the "Hyperbola-2" model, pointed out that the success of these two verifications is equivalent to getting the basic "admission ticket" for reusable rockets. The rocket will be followed by repeated test flights in preparation for future launches into orbit (into space orbit).
He said the goal set by the R&D team is that the rocket can be reused 20 to 30 times, and the best economic benefits will be 8 to 10 times. He predicted that in the future, after the rocket is recovered and reweighted, the launch price will be about 50% lower than the current market price.
In fact, there are many institutions or companies that develop reusable rockets, in the case of China, the world's first liquid oxygen methane rocket ("Suzaku 2") is one of the private enterprises Blue Arrow Aerospace, and the national team's "Long March 8" rocket will also achieve the goal of first-stage reuse in the future.