John Honeycutt, chair of NASA’s Artemis II mission management team, said the decision to relax safety limits between Artemis I and Artemis II was based on test data.
“The SLS program, they came up with a test campaign that actually looked at that cavity, the characteristics of the cavity, the purification in the cavity … and they introduced hydrogen to see when you could actually ignite it, and at 16 percent, you couldn’t,” said Honeycutt, who served as NASA’s SLS program manager before moving to his new job.
Hydrogen is explosive in high concentrations when mixed with air. This is what makes hydrogen a powerful rocket fuel. But it is also very difficult to control. Molecular hydrogen is the smallest molecule, meaning it can easily escape leakage paths, and poses a material challenge for seals as liquid hydrogen is cooled to minus 423 degrees Fahrenheit (minus 253 degrees Celsius).
So, it turns out that NASA used the three-year gap between Artemis I and Artemis II to get comfortable with the more significant hydrogen leak, rather than fixing the leaks themselves. Isaacman said this will change before Artemis III, which is likely at least three years away.
“I would say almost conclusively for Artemis III, we will cryoproof the vehicle before it reaches the pad, and the propellant loading interface we are troubleshooting will be redesigned,” Isaacman wrote.
Isaacman took over as NASA Administrator in December and has criticized the high costs of the SLS program.-Estimated by NASA’s Inspector General at more than $2 billion per rocket -along with the slow flight rate of the launch vehicle.
NASA’s expenses for the rocket’s ground systems at Kennedy Space Center are similarly enormous. NASA will spend approximately $900 million on Artemis ground support infrastructure in 2024 alone. Most of the money was spent building a new launch platform for an advanced version of the Space Launch System that would probably never fly.
All this makes each SLS rocket a golden egg, a unique specimen that must be treated carefully because it is very expensive to replace. NASA and Boeing, the prime contractors for the SLS core stage, never built a full-size test model of the core stage. There is currently no way to fully test the cryogenic interplay between the core stage and ground equipment until the fully assembled rocket is on the launch pad.
Existing law requires NASA to continue flying the SLS rocket through the Artemis V missions. Isaacman wrote that the Artemis architecture “will continue to evolve as we learn more and as industry capabilities mature.” In other words, NASA will incorporate new, cheap, reusable rockets into the Artemis program.
The next series of launch opportunities for the Artemis II mission will begin on March 3. If the mission does not launch in March, NASA will need to return the rocket to the Vehicle Assembly Building to refresh its flight termination system. More launch dates are available in April and May.
“There is still much work to be done to prepare for this historic mission,” Isaacman wrote. “We will not launch until we are ready and the safety of our astronauts remains the top priority. We will keep everyone informed as NASA prepares to return to the Moon.”
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