China's Space Program Thread II
- Thread starter Blitzo
- Start date
Yes succesfully entered lunar orbit, now just to wait for optimal conditions to land.Anyone know the current location of Chang'e 6? It shold have completed its slingshot gravity assisted maneuver by now.
Edit. iantsai just posted the answer a few seconds before me.
Do not listen to the stories fabricated by fans of Elon Musk in China. The story you mentioned never actually occurred.
The upper echelons of China's space program have always been very focused on the technology of reusable launch vehicles. This interest began before the year 2000, but due to China's insufficient economic strength at the time, the focus was on following the technological research and reserve efforts of the United States, Europe, and Japan, without drawing much attention. In reality, China has conducted research on various types of space shuttles, including the American and Russian space shuttles (side-mounted), the European space shuttle (top-mounted), the X-33 (single-stage to orbit with an expander cycle hydrogen-oxygen engine), and the K-1 rocket (parachute recovery for both stages). Around the turn of the millennium, there was in-depth research based on the K-1 and European space shuttle technology pathways.
Before the CZ-5 project was initiated, there was an exploratory study on the technology of reusable launch vehicles within the Chinese space sector. This study aimed to thoroughly understand the associated requirements. Around 2005-2006, research on reusable launch vehicles began, which was divided into two parts: one for the second-stage reusability and the other for the first-stage reusability, with the goal of achieving both by the year 2020. The first-stage plan was officially shifted into development around 2010 and completed two test flights (AT-1b) between 2021-2023. This AT-1b was benchmarked against the American Boeing XS-1. The outcome was that Boeing abandoned the project, while China's was successful. The second-stage plan, which was benchmarked against the X-37, also completed two flights.
Therefore, between 2010 and 2020, China has been consistently working on the development of reusable launch vehicles (VTHL configuration scheme).
SpaceX's Falcon 9 is a VTVL (Vertical Takeoff, Vertical Landing) reusable launch vehicle, which primarily requires deep throttling and the parallel operation of multiple engines (with thrust within a hundred tons). It must also use hydrocarbon fuel, with China and Russia being the main countries developing hydrocarbon fuels. Meanwhile, the United States, Europe, and Japan have been focusing on high-thrust hydrogen-oxygen propulsion. As a result, VTVL has not seen widespread development. Once SpaceX and Blue Origin began working on VTVL, China promptly started a 10:1 deep throttling research for the YF-100 engine in 2014. The slower emergence of China's VTVL is not due to other reasons but because the thrust of the YF-100 is too high, and the minimum thrust required for landing does not match the YF-100's minimum thrust capability. Therefore, it was necessary to domestically develop new engines (with a thrust of 60-100 tons) and large-diameter rocket bodies (3.8-4.2 meters). The core goal was to ensure that the engine thrust and mass required for landing would be compatible.
In fact, SpaceX mainly benefited from the appropriate thrust of the Merlin 1 engine. It took them about a decade (from 2006 to 2015) to go from the initial development of the Falcon 9 to the reusability of its first stage. China's decision to move forward with VTVL was around 2017-2018, primarily for the purpose of near-Earth small satellite constellations, which is why there are now 5-6 Falcon 9 competitive rockets on the market.
SpaceX is not as crucial or impressive as you might think. In fact, its lead is due to the need to redevelop rocket engines and airframes at this scale. The engines and airframe of SpaceX's Falcon 9 were more suitable for this task from the outset.
The engines on the shelves of other companies are too powerful. Starting from scratch is also very time-consuming (the normal engine development cycle is 5 years, and the rocket is another 5 years, adding up to 8-10 years to produce an entirely new rocket). Before proposing a brand-new VTVL (Vertical Takeoff, Vertical Landing) route in 2017-2018, China also proposed two plans, CZ-6X and CZ-8R. The CZ-6X was considered to have too little payload capacity to be of practical value (as stated by exhibitors at the 2018 Zhuhai Airshow), and the CZ-8R faced significant difficulties in engine throttling (the YF-100 engine's thrust is too high when throttled down by 50%), so the CZ-8R is still in development. I hope you recognize that before 2017-2018, the Chinese space industry was thinking about how to quickly modify a VTVL rocket from off-the-shelf technology. After 2017-2018, the Chinese space industry essentially abandoned this technological route. Apart from the CZ-10, it mainly involves new engines and new rocket airframes.
Now, SpaceX's Starship has a multitude of issues and has completely undermined the Artemis program. It is, in fact, a very flawed design. China's CZ-9 did not make the same mistakes as SpaceX's Starship. Of course, the average person does not understand this and will only think that the CZ-9 is copying the Starship. Just as many people believe that the J-10 copied the Lavi/F-16, the J-20 copied the F-22, and the J-35 copied the F-35. They do not understand the differences in technology and design philosophy, especially the significant differences in technology and parameter design caused by different design philosophies.
What is left of the Starship besides its boastful payload capacity, maximum takeoff mass, and thrust? Look at how the payload coefficient has become such a poor parameter.
The Starship V1's low Earth orbit (LEO) payload capacity is not even as much as that of the Falcon Heavy. One has a takeoff mass of 5000 tons, and the other is 1200 tons. What is there to learn from this?
The real reason for the CZ-8R's issue is that the minimum thrust of the YF-100 engine is too high. The original version of the YF-100 has a stable throttling capability of 65%. This results in a minimum thrust of 78 tons for a single-engine rocket. In the case of the CZ-8R, the mass of the recoverable rocket body is approximately 14 + 8 + 8 = 30 tons. The minimum thrust of the engine is much greater than the mass of the recoverable rocket body.
The engine's excessive thrust causes too rapid deceleration, making it difficult to precisely control the landing speed. The scientific issues involved here could fill thousands of words, but the problem is that most people do not have the capacity to understand complex mechanical and physical space problems.
The YF-100 engine with a 10:1 deep throttling capability was specifically designed for the CZ-8R. The issue is that it has not yet been developed.
by78
General
The maiden flight of Long March 6C was a success, which inserted four satellites into orbit.
by78
General
An update on the Sino-French Space-based Multi-band Astronomical Variable Objects Monitor (SVOM) satellite. The assembled satellite has passed expert review. The launch is officially scheduled for June of 2024.
The Sino-French SVOM satellite has been packed and shipped to the Xichang center. Launch date is June 24th.
by78
General
An update on the AZSpace/Ziwei's Dier-1 technology demonstrator cargo craft. Dier-1 has been operating smoothly since launch and has met all performance expectations. The valuable data collected from this mission will pave the way for the upcoming B300 unmanned cargo spacecraft.
Ziwei's Dier-1 satellite is equipped with a micro-pulsed plasma thruster developed by students of Beijing Institute of Technology. The thruster was ignited on April 16 and has so far operated for a total of 21 hours. Its performance has met all design parameters.
China has done studies on reusable space vehicles since basically the start of its rocket and space programs. Qian Xuesen had already worked on spaceplanes when he was still in the US. It just wasn't pursued for practical reasons i.e. lack of technology and budget.
It was the right thing to do in my opinion.
VTVLs are a lot more efficient than VTHLs. Because they have lower empty mass. You can get more payload. But you need deep throttling of engines and you need automated control with low latency. The latter was only available with the introduction of fly by wire in the late 1970s/early 1980s. For example in the X-33 they adapted the avionics software of the F-15 to control the rocket.
You could argue that the US had deep throttling engines since the late 1960s with the RL-10.
In my opinion the only use for VTHLs if you want to have similar capabilities to the Shuttle where you want to have huge crossrange capability. i.e. the rocket will land in a base a long distance away from the staging area. SpaceX ended up dispensing with this because of the floating barge recovery landing.
The less deep throttling the engines have the more engines you will need to put in the rocket. It is as simple as that.
Actually SpaceX has redesigned the Merlin engine at least two times. You had the version used in the Falcon 1, the one used in the initial Falcon 9, and the one in the Falcon 9 FT. Each of the "redesigns" was essentially a new engine.
No, SpaceX did a lot of things right. They designed engines which are cheap and easy to manufacture yet reliable and powerful enough. Their rocket is pretty lightweight, they dispensed with isogrid construction like most of the industry today uses. So their rockets should be a lot cheaper to manufacture. They made the Falcon 9 a modular rocket with the Falcon Heavy. And they got reusability working. Now, the thing is, basically none of these ideas were new, and all of them had been tested before. It is just that no one put them all in the same rocket.
It is the second stage reusability. Each pound you put into the second stage for reuse, is one less pound of payload you have. Second stage reusability is a lot more penalizing than first stage one. They could vastly increase the payload if they just made the second stage expendable.
The Merlin 1 series engines used by the Falcon 9 don't really have any secrets. The way they are improved is by increasing the maximum fuel flow on a basic engine configuration to achieve the greatest increase in thrust, but the basic engine's thrust is always retained as the lower limit for throttling. The Merlin 1 engine does not have throttling capabilities; the maximum thrust of this engine is the thrust at which the engine variants, Merlin 1C/1D/1D+, are throttled down.
When SpaceX was first established, its capabilities were very limited. Therefore, the designs of the Falcon 1, Falcon 5, and Falcon 9 (versions 0.9/1.0) were quite conventional, and their capabilities were average. The performance of the Merlin 1 engine was also low. This was not because their ideas were particularly good or ingenious, but rather because their actual technical capabilities were insufficient. As a result, the products could only be made to that extent. The design of the Falcon 9 has been around for nearly 20 years (the design of the Falcon 5 began in 2005, which was then quickly changed to the Falcon 9). Over a decade ago, a group of rocket enthusiasts started to follow and study this rocket. Before the Falcon 9 achieved reusable launch vehicle technology, it was a very ordinary and even backward rocket technology. In fact, it remains the same today.
It is precisely because the technological level of the Falcon 9 is not high that you can see that second and third-tier technical teams in the Chinese space industry can replicate this rocket within a few years without any difficulty.
Both SpaceX's rockets, the Falcon 9 and the Starship, have many issues. They are merely overshadowed by the halo of being the first reusable rockets.
The issue with the Starship's payload capacity is related to its stainless steel structure. Three years ago, in the WeChat group I was part of, someone calculated that the structural mass of the rocket is overweight, resulting in a LEO (Low Earth Orbit) payload capacity of only 40-60 tons. This is something that people who care about the subject are closely watching, and it is frequently mentioned on the NASA Space Flight (NSF) forum. Elon Musk has consistently avoided mentioning this issue, but when the maiden flight takes place, everyone will be watching. Not just me, but also Americans, such as those in the space industry and a former SpaceX launch site chief engineer, have brought this up.
Putting aside the structural quality issues, the biggest problem with the Starship is the design of its second stage. All its problems stem from this design, which will prevent the Starship from effectively aiding the development of the U.S. space industry before 2030.
The payload bay of its second stage is a closed design, and the currently feasible hatch opening solutions (which will only be available after 2030) have a maximum opening of 8 by 6 meters. This allows for the release of a maximum payload of 8-10 tons in a single go (which is the payload capacity of the Falcon 9).
As a result, SpaceX can only propose the integrated fueling HLS (Human Landing System) solution. NASA required SpaceX to provide a launcher similar to the CZ-9, but after discussions, SpaceX rejected (ignored) this requirement. The current unreliable HLS design has led to the Artemis 3 mission being reoriented.
The Starship is a huge gamble. Elon Musk is not infallible, as evidenced by his mistakes at Tesla. Have you ever considered that SpaceX's errors (failures) could lie in the misplanned Starship?