The crew mission to the International Space Station, which will depart from the Kennedy Space Center on Halloween, has been postponed for at least a few weeks as NASA and SpaceX investigate the issue with the company’s Merlin rocket engine. But the problem in question was not really found on the booster that is preparing to take the four new crew members to the rotating outpost. The story resumes on October 2, when the computer sitting on the Falcon 9 set to launch the next-generation GPS III satellite into orbit for the US Space Force stopped the engine with just two seconds to go before the liftoff.
The fact that SpaceX and NASA have decided to launch a separate Falcon 9 is a clear indication that the issue is not limited to a specific booster, and that there should be a problem with the design of the Merlin engine or its design. . While both companies have been relatively tight-lipped about the current situation, a tweet from CEO Elon Musk a few hours after the GPS III abortion problem hinted at a problem with the engine’s gas generator:
As we discussed earlier, the Merlin is what is known as the “open cycle” rocket engine. In this classical design, which belongs to WWII’s German V-2, small and less efficient rocket engines are used primarily to generate the power required to pump propellants into the combustion chamber. The expected pressure in the gas generator could lead to the catastrophic failure of the turbine driving it, so the Falcon 9’s onboard systems determined that the abortion was in order.
Grounding the entire fleet of rockets because a potentially serious defect has been found in one of them is a reasonable precaution, and this has been done many times before. Engineers need time to investigate the issue and determine whether the change should be made before the flight can safely return to the remaining vehicles. But things get interesting in this regard.
SpaceX has not built a full fleet of their Falcon 9 rockets. In fact, the company has flown many of them since the unveiling of the October 2nd October. So why are some of these boosters stuck in their hangs, while others continue to fly their scheduled missions?
Certified pre-flight boosters
Since 2018, a growing number of SpaceX missions have used previously flying boosters. Thanks to the introduction of new, and ultimate research into rockets known as blockchains, after gaining valuable flight experience with earlier versions of the booster, SpaceX engineers were able to identify the parts that suffered the most damage during the flight. , Re-enter Earth’s atmosphere and landing.
Given these vulnerabilities in Block 5, SpaceX believes the Falcon 9 should be able to fly at least 10 missions with only minor improvements. With occasional overhauls, each fuselage could potentially make as many as 100 flights, although that would be years or decades before the theory was put to the test. To date, no Falcon 9 has made more than six flights.
Of the 18 successful launches made by SpaceX so far in 2020, all but two have been reused on the Block 5 booster. Most of these rockets, and their engines, were originally built in 2018 or 2019. Newly manufactured boosters are usually used at the customer’s request at this time, and two companies that are said to fly continuously on fresh rockets, do so. Become NASA and the Space Force.
As a result, the rockets that were scheduled to launch the crew dragon Resilience October 31 and on GPS III Satellite Sakagavia The two were built at the same time on October 2nd earlier this year. In fact they also have serial numbers, known by SpaceX as B1061 and B1062, respectively.
In light of this, it has become clear why SpaceX could not ground the entire fleet. We are not focusing on the issues that affect the Falcon 9, only the issues that have been produced in 2020.
Experience year after year
The design of the Falcon 9 Block 5 and Merlin engine has been stabilized since 2018 to facilitate human-rating of the vehicle by NASA, so we know that no new or redesigned components have been introduced. But that doesn’t mean that SpaceX can’t get a bad batch of components from the supplier that got into the B1061 and B1062. Such a scenario would not exist without a precedent.
In 2015, a high-pressure helium bottle fell loose inside the second phase of the Falcon 9 when the CRS-7 mission ended two minutes after Fana with complete vehicle damage. An investigation of stainless steel eye bolts used to hold the bottle in place found that despite being rated by the manufacturer for a load of 10,000 pounds, some failed at just 2,000 pounds. A later investigation by NASA determined that the crash was ultimately on SpaceX because they could not independently verify the manufacturers’ claims before the flight.
Pre-flight testing is of course important, while there is no substitute for the real thing. SpaceX has always maintained that a rocket designed for reusability would be even more reliable than one designed for a single flight. With each subsequent flight and inspection, the company believes the overall reliability of the vehicle has improved.
The accessories that appear to be worn have been replaced, while the main vehicle systems that have proven their reliability remain in place. SpaceX said the goal is to implement a maintenance schedule for their rocket as opposed to what happens with a commercial aircraft, and finally, try to return an individual booster to flight within a few days or even hours.
Rather than requesting a new fresh rocket for their mission, NASA and the Space Force believe they are getting a more reliable vehicle, but these facts seem to contradict each other. To date, the new and reusable Falcon 9 Block 5 rockets have a 100% success rate. While there is no evidence to support this confirmation that one is inherently more reliable than the other, the current situation suggests that the use of flight-proof boosters could have prevented delays. Resilience And Sakagavia Mission.
Test as you fly
Of course, delay is more appropriate than failure. When human life is in danger, it is always better to take extra time to make sure everything is working perfectly. According to Kathy Luders, Associate Administrator, NASA’s Directorate of Human Research and Mission Operations, SpaceX is currently replacing one engine The ISS-bound Falcon 9 exhibits the same gas generator behavior as the 2nd October October discrepancy. They will also replace the engine of the next rocket that came out of the assembly line, serial number B1063, which is currently due to launch the joint NASA / ESA Earth observation satellite before the end of the year.
Which brings up an interesting point. Using a certified booster for all payloads, whether it is goods for a space station, communications satellites or human settlements, allows for more opportunities to catch potential errors made by NASA during the space shuttle era.
If the crew mission was not set to fly on a rocket that was virtually identical to the one carrying it Sakagavia GPS III satellite, gas generator issue could not be found in time. While the crew dragon booster rocket is capable and capable of pulling its human inhabitants to safety when it should fail, it is no accident, no one is particularly keen to use it.
Between post-flight tests and maintaining the same vehicle configuration regardless of payload, the Falcon 9 is rapidly moving toward becoming one of the most reliable orbital boosters in history. Which is likely because NASA has decided to allow crew flights on the flight-proven Falcon 9 booster next year. The agreement clarifies that the agency will only allow astronauts to fly A little Rocket used, but at least it’s a start.
