Zoom / The Space Launch System rocket leaves the vehicle assembly building in mid-March 2022.
Trevor Mulman
After three attempts to complete a critical test for refueling the Space Launch System rocket, NASA decided to take a break.
On Saturday night, the space agency announced plans to transfer the large SLS rocket from the launch pad at the Kennedy Space Center to the vehicle assembly building in the coming days. This marks a remarkable step back for the program, which has been trying to complete a “wet rehearsal” test since April 1, during which the rocket is loaded and brought to 10 seconds after launch.
The decision comes after three attempts in the last two weeks. Any attempt to refuel was thwarted by one or more technical problems with the rocket, its mobile launch tower, or ground systems that deliver propellants and gases. During the latest experiment, on Thursday, April 14, NASA was able to fill 49 percent of the liquid oxygen tank in the ground stage and 5 percent of the liquid hydrogen tank.
Although this is an improvement, it does not include the most dynamic part of the test, during which the rocket is fully refueled and pressurized; namely, terrestrial systems and computer systems are placed in a terminal countdown when each variable is closely monitored. NASA had hoped to complete this wet dress rehearsal test to remove the curves in the complex launch system, so that when the rocket is launched later this year for its actual launch, the countdown will be relatively smooth.
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NASA said this, and the agency’s contractors will use the next few weeks when the SLS rocket returns to the large vehicle assembly building to resolve issues that arose during refueling tests. For example, the supplier of the nitrogen gas system Air Liquide will upgrade its capabilities. NASA will also replace a defective non-return valve on the upper stage of the rocket, as well as eliminate a leak on the “tail service mast of the umbilical tower” of the mobile launch tower, a 10-meter structure that provides fuel and power lines to the rocket pad.
The space agency’s announcement did not provide any information on the effects of the schedule. It looks like it will take about a week to prepare and return the SLS missile back to the vehicle assembly building. Then the rocket work there will probably take most of May, at least.
Then NASA will have to make some difficult decisions. He may choose to drop the rocket and its mobile launch tower at the site a second time and try to complete the wet dress rehearsal test again. Then, following its normal procedure, NASA would return the rocket back to its assembly building to arm the “flight safety system” before moving a third time to launch. It seems that the earliest launch of the SLS rocket in such a scenario will be August, but take-off in a fall may be more likely.
Another possibility that NASA could pursue is to launch, complete a test for wet clothing on the pad, and then, if successful, continue and launch within a few days. In such a scenario, NASA may be able to launch the SLS rocket in June or July. However, this would be risky due to the flight safety system.
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During a teleconference on Friday, Artemis flight director Charlie Blackwell-Thompson confirmed that there is a 20-day schedule after the flight safety system is activated. (This is a safety mechanism used by all orbital missiles that destroys the accelerator in case it deviates from the course). Once the system is activated, it will take about a week to make final preparations in the vehicle assembly building, and one week to roll to the launch site and make preparations there. This will leave only one week for a refueling and recycling test and maybe one or two attempts to start before closing the 20-day window.
In other words, this means that the test for wet clothing must pass almost flawlessly, and then the start-up attempt will also pass flawlessly. It would also mean that the summer weather in Florida – when there are many thunderstorms and other adverse conditions – will also have to cooperate.
Finally, NASA engineers must also weigh a number of other factors, such as the wear and tear of the rocket and its side-mounted accelerators on display, as well as seemingly countless considerations for the life of the hardware. For example, agency officials are closely monitoring the health of the fuel in the solid-fuel rocket boosters, which were deployed about 16 months ago, among other issues.
However, NASA seems confident that it will go through this painful process of teething for the SLS rocket; a program that is now 11 years old and in which NASA has invested more than $ 30 billion in missile and ground systems that are now being tested.
“There is no doubt that we will complete this test campaign and listen to the hardware and the data will take us to the next step,” Blackwell-Thompson said on Friday. “And we will take the appropriate steps and launch this vehicle. I don’t know exactly what that date is, but I have no doubt that we will complete the test campaign and be ready to fly. “
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