Remember the SLS (Space Launch System) of NASA's next-generation manned lunar rocket in mid-March when the scenery was vertically transferred from the assembly hall to the launch station?
It was the first appearance of the heavy rocket for the final test before launch, the "wet rehearsal.".
The so-called "wet", as the name suggests, rockets at all levels will inject more than 2.6 million liters, about 1,000 tons of liquid oxygen liquid hydrogen and other liquid propellants and protective gases, simulating the entire process except for launch and liftoff on the ground. Afterwards, all the propellants must be discharged and ensure that the rocket returns to a safe state, and the difficulty and total cost of the entire test can be imagined.
The debut of the SLS lunar rocket can be described as an infinite scenery | NASA
As a space mass killer that NASA has been brewing for more than 20 years, has a budget of more than $23 billion, and costs no less than $2 billion per launch, the SLS Heavy rocket was originally expected to conduct only the most comprehensive wet rehearsal this time. Immediately after its success, the first launch began in May, completing Artemis' first mission back to the moon.
However, the wet rehearsal for the SLS was rather unsmooth and largely a failure.
Wet rehearsals are full of twists and turns
On March 18, Beijing time, SLS successfully transferred to the LC-39B launch platform in Kajiao, and after about two weeks of comprehensive testing on the launcher, NASA officially began the scheduled plan of wet rehearsal on April 2.
However, the start was uneventful, with two large fans responsible for supplying pressure to the enclosed area of the mobile transmitter failing. This is the core area of the propellant filling, and it is necessary to prevent the accumulation of harmful gases by pressurizing it to maximize the safety of testing and launch. In this case, the wet rehearsal can only be aborted immediately.
Before the first wet rehearsal, the mobile launch pad was struck by lightning, but this had nothing to do with the glitch that followed| NASA
Fortunately, this is not a problem with the rocket itself, and the fan failure is easy to troubleshoot, and the next day (April 4), NASA rearranged the wet rehearsal. This time, another exhaust valve on the mobile launch pad was stuck, resulting in the inability to start the liquid hydrogen refueling. Although liquid oxygen filling was 50% complete at that time, the second wet rehearsal could only be abandoned halfway.
On April 7, after replacing a regulator on the mobile launch pad, technicians discovered that a valve inside the ICPS, the upper stage of the SLS rocket, had also failed. This failure could not be solved at the launch platform site and had to be transported back to the final assembly workshop to disassemble the rocket before it could be repaired.
In order not to delay more time, NASA had to change the "wet rehearsal" scheme, cancel the test of refueling the rocket's upper stage, and try to bypass the faulty valve inside the ICPS, hoping to complete other tests involved in the "wet rehearsal".
As the sun sets, SLS waits on the launch pad for the next wet rehearsal | NASA
The timeline was advanced to April 15, and NASA opened the "shrinkage" wet rehearsal of SLS for the third time. This time the start was much smoother, and the core stage of SLS began to be injected with liquid hydrogen propellant. For such rockets, liquid hydrogen, as a reducing agent, has a very low density, a very large volume, a very low temperature, is easy to volatilize, and has the highest risk factor, is the most difficult part to deal with.
Soon, however, the problem was revealed: the bottom of the launch pad began to leak a lot of rocket propellant, which was an irreparable fatal injury. Because a large amount of liquid hydrogen into the air, will quickly become gas, and the ubiquitous oxygen in the air to form a natural super "bomb", once the danger occurs, the consequences can be imagined. NASA could only immediately call off the third test.
After another 10 days of thorough inspection, the engineers also identified other potential problems and agreed that the last failure was completely irreparable, and the series of wet rehearsals with mud and water could only be declared over.
On April 26, SLS returned to the final assembly workshop.
SLS rockets shipped back to the final assembly workshop overnight. Behind it was the Falcon 9 rocket | ready to launch a new group of astronauts to rotate on the International Space Station Stephen Clark
The "New Ace Pigeon" rocket was postponed again
These problems show that wet rehearsals are extremely important for the development of new rockets, which can detect potential risks in advance and avoid catastrophic consequences at launch to the greatest extent.
But it is clear that the first launch of the SLS rocket will not be able to take place in May this year, as previously planned.
In a may 5 conference call, NASA said that the cause of the valve failure inside the rocket's upper stage had been identified, and it was stuck by some rubber debris, but the source of the debris still needs to be investigated.
If all goes well, the SLS rocket will return to the LC-39B launch platform by the end of this month, with the fourth full "wet rehearsal" test expected in early June.
If the next "wet rehearsal" can be successfully completed, NASA will determine the launch time of artemis's first launch mission.
The first flight of the SLS was scheduled for May this year, and the launch time is currently to be determined | NASA/MSFC
Behind the most enthusiastic rocket launch countdown on the surface, there are still too many support links, such as engine commissioning, overall rocket design, processing and manufacturing, transfer final assembly transfer and launch site system. Any shortcoming will result in outright failure.
For the SLS, a NASA mass killer that combines elements such as national strength, decades, tens of billions of dollars, return to the moon, extremely high cost of a single launch, and manned rockets, it must be cautious.
However, this also makes many space enthusiasts who pay attention to SLS research and development quite disappointed: What, this cargo that has been engaged in for decades, even wet rehearsals are frequent?
After all, SLS is not a disruptive new rocket technology, but basically a "rocket version" of the mature project space shuttle that lasted for 40 years.
Just from the outside, you can see that SLS and the space shuttle have a clear intergenerational inheritance | NASA
SLS's 4 core engines, RS-25D (and an upgraded version of RS-25E), are the main engines of the space shuttle, have long verified excellent reliability and reusability, and have almost never had major problems, which is the ceiling of human liquid hydrogen liquid oxygen rocket engine technology. The cost is naturally very high, and the cost of a single engine itself is as high as about 100 million US dollars. The shuttle used 3 engines repeatedly, but the SLS threw 4 at a time without looking back.
The core grade of SLS, the standard large orange jar, is soiled to no coating, only the natural color of the insulation material. This is instantly reminiscent of the big orange can of the space shuttle. That's right, these two are ben out of the family.
Its core thrust comes from two solid boosters, which are also upgraded versions of the space shuttle booster. Weighing 725 tons and thrusting up to 1600 tons, a booster can push a round of five (takeoff weight of about 870 tons), which is indeed a violent monster.
Therefore, the wet dress rehearsal is made like this, which is indeed a mess that makes people feel "wet".
No contrast, no harm
In contrast, during the SLS wet rehearsal on the LC-39B, SpaceX's Falcon 9 rocket was erected on the LC-39A next door, so that the two could take a clear group photo in the same frame.
SLS and Falcon 9 are in the same frame, and the scene is quite classic | daytonews
The Falcon 9 rocket in the picture is the fifth launch mission and the second manned spaceflight. Axiom-1 is also the first purely private mission to the International Space Station in the history of human manned spaceflight. From the launch of the Falcon 9 on April 8 to the successful return of the Axiom I astronauts on April 25, SLS has been quietly watching from the next door.
It's really quiet, because none of its three wet rehearsals have been done.
Even more ironically, on April 29, shortly after the SLS was pulled back into the final assembly test hall, the recovered Falcon 9 rocket launched for the sixth time, transporting 53 Starlink satellites into space, setting a record for the shortest time for the Falcon 9 rocket to launch again in just 21 days.
Falcon 9 launches Axiom 1, and SLS stands quietly on the right | Max Evans
Although it is not fair to compare SLS with the Falcon 9, which is far less capable of transporting than its Falcon 9, SpaceX's Falcon Heavy rocket has really not given face after snatching the SLS's "Europa Clipper" order before.
As NASA's new flagship Jupiter exploration mission, Europa Clipper has a very high budget and was not so sensitive to the high launch cost of SLS, but it really can't withstand the continuous postponement of SLS and the serious shortage of launch frequency, and more importantly, the heavy falcon is too fragrant. SpaceX's $178 million offer, almost one-tenth of SLS, saves more than a billion dollars, what's not to like?
Satellites with low-Earth orbit capacity of the same class as SLS have been waiting for the Federal Aviation Administration (FAA) to issue airworthiness permits for their first flight. Whoever makes the first flight will be the strongest in the world in the past 20 years, and naturally everyone wants to take advantage of this opportunity.
Now the SLS has collapsed again, depending on how long the FAA, which has postponed the release of the report four times, can hold the starship.
On March 18, the SLS transshipment, the starship had already conducted a propellant refueling test | SpaceX
Some people will ask, SLS is so weak, why does NASA spend so much energy on research and development? That's another story, enough to write another article.
In short, SLS, despite this, still represents the most technological technology in aerospace and is of great significance to the long-term development of loma, Boeing and Noegger, the three major military giants. And in the next version of SLS after maturity, the three giants will practice a series of cutting-edge technologies on it, such as new upper grades, new solid boosters, new composite storage tanks, etc., which are not technologies that SpaceX can undertake.
The length of this article is limited, so we have time to talk about it. Fruit Shell will also continue to follow the progress of test flights of SLS and starships, so stay tuned.
Author: Space Craft Brew
Edit: Steed
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