NASA will likely retest the hot fire of the Space Launch System’s primary stage
distance Unsuccessful completion From the hot test fire of the Space Launch System, NASA will likely conduct a second „Green Run“ launch in February.
On Tuesday, three days after the first hot firing test attempt, NASA Summary released From its initial analysis of data from the test launch for 67.2 seconds. The report highlights three cases, none of which appear to be extremely serious but which require further investigation.
The agency found that the test, conducted at the Stennis Space Center in Mississippi, was automatically switched off by an out-of-limit reading of the hydraulic pressure in the thrust vector control mechanism used to move or steer the engines. In 64 seconds of testing, the missile started a pre-programmed sequence to move its engines as if it were in flight. Soon after, the pump return pressure dropped below the red line of 50 pounds per square on the gauge, to 49.6. The agency said this pressure limit was stricter than the actual flight red line and was set to protect against potential damage on the test stand.
Another problem is the „Main Component Failure“ in Motor 4, and it appears to be a relatively minor issue where the overload sensor has failed. This is fine, as it means that NASA will likely not have to switch this motor from the primary stage. There are four main engines of the Space Shuttle used in the SLS rocket.
Finally, the „flash“ observed in the engine section appears to be somewhat normal. A visual inspection of the thermal blankets between the motors shows some combustion, but this is to be expected. There were no indications of a fire, leak, or other problem.
To repeat or not to repeat?
The published NASA summary does not discuss whether the agency will proceed with a second primary phase test. Before the test, NASA had hoped to run the motors for at least 250 seconds to get a full set of data on the performance of the base stage. They’ve apparently only been running the engines for a quarter of that time.
According to agency sources, program managers are actually leaning towards running a second test shooting in Mississippi. Given the need to get more propellant at the test site, a minor vehicle overhaul, and possibly an irregular sensor change in the engine 4, the agency estimates it will require about three to four weeks before another test can be done.
NASA and the main contractor for the primary stage, Boeing, have collected a lot of data about the test. Of the 23 test targets, the agency said, 15 had been completed with 100 percent of the required data. Four others obtained most of the required data, while three of them had partial data, and one of them had no data. (This was a test of how the pressure of the liquid oxygen tank would respond when liquid oxygen was largely used and the tank emptied.)
NASA engineers are now studying the data in more detail and will soon conduct a risk assessment to determine the risks of skipping the second test. Since it is standard practice to retest in such circumstances, a second test is highly likely.
It remains difficult to determine what this means for the schedule for the start of this primary stage as part of the Artemis I. Prior to this delay, NASA was already struggling to achieve its goal of launching an unmanned Orion spacecraft around the moon before the end of 2021. There was no margin. Big on the schedule, and assume the launch this year has seamless heaping and integration processes – big assumption. Now it looks likely that NASA will lose at least a month.
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