Qiao Hui, Tencent Technology
At about 6:20 Beijing time on May 6, 2021, the SpaceX prototype (code name sn15) successfully conducted a high-altitude flight test in Boca Chica, Texas. This is the fifth time that the SpaceX prototype has challenged the altitude of 10km and the first perfect landing without explosion.
Note: sn15 returned to the ground successfully.
This flight procedure is similar to the previous four times: first, the Starship flies to the highest point, then the attitude is adjusted to make the abdomen rush down, with the help of the abdomen to increase the contact area with the air and increase the resistance of the air to the starship, and then the Starship slowly falls to the ground. At a certain height from the ground, the engine ignites again to make the Starship stand up again (commonly known as “dragon wags its tail”), Soft landing by engine thrust.
Before this test, on December 10, 2020, February 3, 2021, March 4, 2021 and March 27, 2021, the prototypes SN8, sn9, Sn10 and sn11 of the Starship carried out the test flight at the altitude of 10km respectively, and the early stage of launch and return was very successful, in which SN8 and sn9 had ground explosions at the last landing stage. It’s a pity that Sn10 exploded a few minutes after landing steadily, blowing up the whole starship. Sn11 was even more tragic. It was foggy that day, and the ground camera could not see the star ship clearly. The camera inside the star ship showed that sn11 took off normally and lost its signal when it was about to land. Through the fog, we first saw a red light, and then a loud noise. We saw debris scattered around and a crushing explosion occurred.
Note: from left to right are the flight test attitude and trajectory of SN8, sn9 and Sn10 respectively.
Among them, the reason why SN8 failed to land was that the pressure of the fuel tank of the spacecraft was insufficient and the thrust of the engine was not enough, so the spacecraft failed to make a successful soft landing; In the landing stage, only one of sn9’s three engines ignited, and the thrust was not enough, resulting in a crushing explosion crash; It is said that Sn10 is also due to insufficient engine thrust. Although it stands still, it can be seen from the playback picture that it rebounds on the ground after standing still. This kind of rebound may cause damage to internal pipelines and fuel leakage. After standing for a few minutes, it still ignites and explodes. Through the playback of the screen, we can also see that three of the six landing legs of Sn10 are not fully extended, which indicates that the structural design of Sn10 still needs to be continuously optimized. The reason for sn11’s failure is speculated to be that a slight methane leak caused a fire that damaged electronic equipment and eventually led to the explosion of the entire starship.
Photo note: This is the smashed debris from the previous sn11 explosion.
Was the Sn10 tested on March 4 a success? According to the official statement of SpaceX, it is a success, which is also reasonable, because the purpose of these “test arrows” of the starship is to carry out technical verification step by step. From launching to reaching the height of 10km, Sn10 will adjust its posture, then rush down its abdomen, and finally re adjust its posture to stand on the ground. All these are normal, which verifies all aspects of the process.
Of course, many experts and media think that Sn10 is not successful, because after landing, the internal structure was damaged unexpectedly, and finally exploded. In fact, it’s not very important whether we are successful or not. Today, sn15’s perfect landing (no explosion) really conquered everyone. Musk’s fast iterative mode of making Internet products has been brought to the field of rocket R & D, which is refreshing.
As early as July this year, the integrated orbit entry flight of the Starship was carried out
The purpose of SpaceX can be seen from the name it gives to the spacecraft, which is a reusable, two-stage orbit heavy rocket launch system. The goal is to be able to carry large quantities of materials to and from the earth and space, the earth and the moon, and even between the earth and Mars. The ultimate vision even supports the colonization of Mars.
Caption: Overweight rockets and starships.
At present, when we refer to the name “starship”, we specifically refer to the second stage spaceship, which is currently being tested. The spacecraft is 50 meters high, 9 meters in diameter and weighs about 1300 tons. It is equipped with three vacuum version Raptor engines and three sea level version engines. Holding the spacecraft is a more powerful super heavy rocket, which is 72 meters high, 9 meters in diameter, weighs 3500 tons and is equipped with 28 Raptor engines. The total height of the spaceship plus the overweight rocket is 120 meters, and the low earth orbit carrying capacity is more than 100 tons, which can send 100 passengers to space at one time.
According to the official, if all goes well, the combination of starship spaceship and overweight rocket will make a suborbital flight in July this year, which will be another amazing work produced by SpaceX after the heavy falcon.
According to the plan, July’s star ship number is SN20, and the overweight rocket part number is bn3. To put it simply, Sn is the abbreviation of starship number, which means starship serial number. BN is the abbreviation of booster number, which means booster serial number. However, according to experience, the possibility of orbital flight in July is not great.
Japanese tycoon yosuo Maezawa waits to fly around the moon by starship
Note: musk and Yoshizawa.
On September 18, 2018, space X announced that Yusaku Maezawa, the first private passenger to travel around the moon, had purchased a ticket for a star ship in advance. If successful, he would become the first commercial space passenger to go beyond Earth orbit.
Information shows that Yoshiro Maezawa, born in 1975, is a Japanese collector and entrepreneur. He is the founder of start today, a Japanese online fashion retail platform, and Zozo (the latter was founded by Yahoo! In 2019)! Japan acquisition). As of January 2020, Forbes estimates that it has a wealth of $2 billion, ranking 22nd on Japan’s rich list.
On March 2, 2021, Japan’s billionaire youzuo Maezawa announced the dynamic update of the “Dear moon” plan, inviting eight people from all over the world to take a free round the moon trip with him on a star ship in 2023. The deadline for application was on March 14.
A friend of mine was lucky enough to successfully apply for the event and received an official email. He said that although the possibility of eventually flying around the moon with Mr. Maezawa is very small, it is not without. If he could choose to fly to the moon, even if he risked his life, he would rather be reduced to ashes in the starry sky and wander in the sky for hundreds of millions of years than stay on the earth and turn it into a pile of fertilizer to participate in the next cycle of the biosphere.
The most powerful liquid oxygen methane engine in the world
As for the liquid oxygen methane “Raptor” engine used by the starship, we have detailed popular science in the previous article “SpaceX starship falls from a height of 10000 meters and explodes after standing steadily for a few minutes”. Here is a brief introduction.
The Starship uses a high thrust engine fueled by liquid oxygen and methane. The maximum thrust of a single engine can reach more than 2000 kn, which can be converted into intuitive understanding, that is, it can lift more than 200 tons of weight, equivalent to four railway cars with 50 tons of goods. Three such engines were used in this test. As mentioned above, the complete version of the Starship will be equipped with six such engines, and the overweight rocket will be equipped with 28 engines. You can estimate the total thrust by yourself. It’s amazing.
At present, the Raptor rocket engine of SpaceX, be4 rocket engine of Bezos blue origin company and tianque rocket engine of blue arrow aerospace, a private enterprise in China, are all liquid oxygen methane engines.
What are the advantages of lox-m engine? First of all, the specific impulse of lox-ch4 engine is larger than that of LOX-KEROSENE engine. The specific impulse is a commonly used measurement index of rocket engine. Its physical meaning is the amount of momentum the rocket can obtain per unit mass of fuel consumed. Obviously, the larger the number, the better. Secondly, methane is easy to burn, not easy to produce carbon deposition, which is conducive to the reuse of rockets. Compared with liquid hydrogen, liquid oxygen methane engine is easy to design and maintain, and its quality and price are cheap, which is very popular with commercial aerospace companies. It is worth mentioning that methane is stored in the kitchen gas tank.
Important node events of starship test
On July 26, 2019, SpaceX conducted a 20 meter free suspension test on the earliest starship prototype starhopper.
On August 27, 2019, SpaceX tested the “starworm” again, successfully flew to an altitude of 150 meters and landed safely.
On August 5, 2020, the prototype SN5 completed the free suspension test at an altitude of 150 meters. Because there is no head vertebra installed, SN5 looks like a 30 meter high cylindrical stainless steel water tower.
On August 25, 2020, the prototype SN6 also completed the free suspension test at an altitude of 150 meters.
On December 10, 2020, the prototype SN8 of the Starship made a test flight at an altitude of 12.5km, and crashed and exploded when it finally landed.
On February 3, 2021, the prototype sn9 of the Starship made another test flight at an altitude of 10 km. It still crashed and exploded when it finally landed.
On March 4, 2021, the prototype Sn10 made its third test flight at an altitude of 10km and landed steadily. However, a few minutes after landing, an explosion occurred.
On March 27, 2021, the prototype sn11 made its fourth test flight at an altitude of 10 km. The failure was even worse, and the rocket body exploded to pieces.
Other starship prototypes either blow up in ground tests or complete historical missions and leave the stage of history. At present, the prototype of the Starship to be built has reached SN20.