After three rehearsals, the first flight of the new generation of moon landing rocket has no date

Do you remember NASA's new generation manned lunar rocket SLS (Space Launch System) that was vertically transferred from the final assembly workshop to the launch position in mid-March?

It was the debut of the heavy-lift rocket, intended for final testing before launch, known as a "wet dress rehearsal."

The so-called "wet" test, as the name implies, involves injecting more than 2.6 million liters, about 1,000 tons of liquid oxygen, liquid hydrogen and other liquid propellants and protective gases into each stage of the rocket, simulating all processes except the launch on the ground. Afterwards, all the propellants must be discharged and the rocket must be returned to a safe state. The difficulty and total cost of the entire test can be imagined.

The SLS lunar rocket made its debut with great fanfare | NASA

As a space killer that NASA has been planning for more than 20 years, with a budget of more than 23 billion US dollars and a single launch cost of no less than 2 billion US dollars, the SLS heavy rocket was originally expected to only conduct the most comprehensive wet rehearsal. After the success, it will immediately start its first launch in May to complete the first Artemis mission to return to the moon.

However, the SLS wet rehearsal went rather poorly and was essentially a failure.

Wet rehearsal has twists and turns

On March 18, Beijing time, SLS was successfully transferred to the LC-39B launch platform in Cape Canaveral. After about two weeks of comprehensive testing on the launch pad, NASA officially began the scheduled wet rehearsal on April 2.

However, the rehearsal got off to a bad start when two large fans responsible for providing pressure in the enclosed area of ​​the mobile launch platform failed. This is the core area for filling propellants, which must be pressurized to prevent the accumulation of harmful gases and maximize the safety of testing and launch. In this case, the wet rehearsal had to be terminated immediately.

Before the first wet rehearsal, the mobile launch pad was struck by lightning, but this was not related to the subsequent failure | NASA

Fortunately, it was not a problem with the rocket itself, and the fan failure was easy to eliminate. NASA rescheduled the wet rehearsal the next day (April 4). To make matters worse, an exhaust valve on the mobile launch platform got stuck, causing the liquid hydrogen filling to fail. Although the liquid oxygen filling was 50% complete at the time, the second wet rehearsal had to be abandoned halfway.

On April 7, after replacing a regulating device on the mobile launch platform, technicians discovered that a valve inside the ICPS of the SLS rocket upper stage also failed. This failure could not be solved on the launch platform site, and the rocket had to be transported back to the final assembly workshop and disassembled for repair.

In order not to waste more time, NASA had to change the "wet rehearsal" plan and canceled the test of refueling the rocket's upper stage, trying 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

On April 15, NASA launched the third "reduced" wet dress rehearsal of SLS. This time the start was much smoother, and the core stage of SLS began to inject liquid hydrogen propellant. For this type of rocket, liquid hydrogen, as a reducing agent, is the most difficult part to handle because it has extremely low density, large volume, extremely low temperature, is easily volatile, and has the highest risk factor.

However, problems soon emerged: a large amount of rocket propellant began to leak from the bottom of the launch pad, which was an irreversible fatal injury. Because a large amount of liquid hydrogen will quickly turn into gas after entering the air, forming a natural super "bomb" with the oxygen commonly present in the air. Once a danger occurs, the consequences can be imagined. NASA had no choice but to stop the third test immediately.

After another 10 days of comprehensive inspection, the engineers discovered other potential problems and unanimously agreed that the last failure was completely irreversible. This series of wet rehearsals had to come to an end.

On April 26, SLS returned to the final assembly workshop along the same route.

The SLS rocket was transported back to the assembly workshop overnight. Behind it, the brightly lit Falcon 9 rocket is ready to launch a new batch of astronauts to the International Space Station | Stephen Clark

The rocket of "New Pigeon King" is postponed again

The emergence of these problems just shows that wet rehearsals are extremely important for the development of new rockets. They can detect potential risks in advance and minimize catastrophic consequences during launch.

But it is obvious that the first launch of the SLS rocket cannot be carried out in May this year as previously planned.

In a conference call on May 5, NASA said the cause of the valve failure inside the rocket's upper stage had been identified. It was stuck by some rubber debris, but the source of the debris still needed to be investigated.

If all goes well, the SLS rocket will return to the LC-39B launch platform before the end of this month, and is expected to start a fourth comprehensive "wet rehearsal" test in early June.

If the next "wet rehearsal" is completed successfully, NASA will determine the launch time of the first launch mission of the Artemis program.

The SLS maiden flight was originally scheduled for May this year, and the launch time is currently to be determined | NASA/MSFC

Behind the rocket launch countdown, which seems to be the most exciting, there are too many supporting links, such as engine test, rocket overall design, processing and manufacturing, transfer assembly and transportation, and launch site system. If any shortcoming appears, the result will be a complete failure.

We must be extremely cautious when it comes to SLS, a NASA killer rocket that combines the efforts of the entire country, takes decades and tens of billions of dollars, requires a return to the moon, has extremely high single-launch costs, and is a manned rocket.

However, this also disappointed many aerospace enthusiasts who were paying attention to the development of SLS: What? After decades of working on this thing, even wet rehearsals have problems?

After all, SLS is not a disruptive new rocket technology; it is basically a “rocket version” of the space shuttle, a mature project that has been going on for 40 years.

Just from the appearance, you can see that SLS and the space shuttle have obvious generational inheritance | NASA

The four core engines of SLS, RS-25D (and the upgraded version RS-25E), are the main engines of the space shuttle. They have long been verified to have excellent reliability and reusability, and have almost never had major problems. They are the ceiling of human liquid hydrogen and 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. Each space shuttle uses three engines repeatedly, but SLS throws four engines at a time without even looking back.

The core stage of the SLS is a standard orange tank, which is so rustic that it has no paint at all, only the natural color of the insulation material. This instantly reminds people of the orange tank of the space shuttle. Yes, these two are from the same company.

Its core thrust comes from two solid boosters, which are also upgraded versions of the space shuttle boosters. It weighs 725 tons, but has a thrust of 1,600 tons. One booster can propel a Long March 5 (takeoff weight is about 870 tons), which is indeed a violent monster.

So, the wet rehearsal turned out like this, which really made people feel "wet" and embarrassing.

No comparison, no harm

What is even more striking is that during the wet rehearsal of SLS in LC-39B, SpaceX's Falcon 9 rocket was standing upright in LC-39A next door, so that the two could be photographed in the same frame.

SLS and Falcon 9 in the same frame, the scene is quite classic | daytonews

The Falcon 9 rocket in the picture has carried out its fifth launch mission and its second manned space flight. This mission, Axiom-1, is also the first purely private manned space mission to the International Space Station in the history of human manned space flight. From the launch of this Falcon 9 on April 8 to the successful return of the Axiom-1 astronauts on April 25, the SLS has been watching quietly next door.

It was really quiet, because none of its three wet rehearsals were successful.

What's even more ironic is that shortly after the SLS was pulled back to the final assembly and testing workshop, on April 29, the recovered Falcon 9 rocket was launched for the sixth time, carrying 53 Starlink satellites into space, setting a record for the shortest time for the Falcon 9 rocket to be launched again, just 21 days.

Falcon 9 launches Axiom 1, with the SLS standing quietly on the right | Max Evans

Although it is not fair to compare SLS with Falcon 9, which has far less transportation capacity, it is really disrespectful that SpaceX's Falcon Heavy rocket previously snatched the "Europa Clipper" order from SLS.

As NASA's new generation flagship Jupiter exploration mission, Europa Clipper has a very high budget and was not so sensitive to the high launch cost of SLS. However, it could not bear the continuous delays of SLS and the serious shortage of launch frequency. More importantly, Falcon Heavy is too attractive. SpaceX's offer of $178 million is almost one-tenth of SLS. What can't be done with more than $1 billion saved?

The Starship, which has the same low-Earth orbit capacity as the SLS, has been waiting for the Federal Aviation Administration (FAA) to issue its airworthiness certificate for its first flight. Whichever of the two will fly first will be the most powerful in the world in the past 20 years, so naturally everyone wants to take the lead.

Now that SLS has failed again, it remains to be seen how long the FAA, which has postponed the release of its report four times, can hold back the Starship.

On March 18, when the SLS was transferred, the Starship had already conducted a propellant filling test | SpaceX

Someone will definitely ask, if SLS is so ineffective, why does NASA spend so much effort on its development? This is another story, enough to write another article.

In short, despite this, SLS still represents the highest aerospace technology and is of great significance to the long-term development of the three major military industry giants, Lockheed Martin, Boeing and Northrop Grumman. And in the next version of SLS after it matures, the three giants will practice a series of cutting-edge technologies on it, such as new upper stages, new solid boosters, new composite tanks, etc. These are not technologies that SpaceX can afford.

This article is limited in length, so we can discuss it in detail when we have time. Guokr will also continue to pay attention to the progress of the test flights of SLS and Starship, so stay tuned.

Author: Space Craft

Editor: Steed

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