After scrubbing yesterday’s Artemis I launch attempt when engineers could not overcome a hydrogen leak in a quick disconnect, an interface between the liquid hydrogen fuel feed line and the Space Launch System (SLS) rocket, NASA mission managers met and decided they will stand down on additional launch attempts in early September.
Over the next several days, teams will establish access to the area of the leak at Launch Pad 39B. In parallel, teams will also conduct a schedule assessment to provide additional data that will inform a decision on whether to perform work to replace a seal either at the pad, where it can be tested under cryogenic conditions, or inside the Vehicle Assembly Building (VAB).
NASA will need to roll the rocket and spacecraft back to the VAB before the next launch attempt to reset the system’s batteries in order to meet the requirement by the Eastern Range for the certification on the flight termination system, which is currently set at 25 days. The flight termination system is required on all rockets to protect public safety.
During yesterday’s launch attempt, engineers detected a leak in a cavity between the ground side and rocket side plates surrounding an 8-inch line used to fill and drain liquid hydrogen from the SLS rocket. Three attempts were made at reseating the seal, but all were unsuccessful.
An early phase of hydrogen loading operations is called chilldown, when launch controllers cool down the lines and propulsion system prior to flowing super cold liquid hydrogen into the rocket’s tank at minus 423 degrees F. During chilldown an inadvertent command was sent that temporarily raised the pressure in the system. While the rocket remained safe and it is too soon to tell whether the bump in pressurization contributed to the cause of the leaky seal, engineers are examining the issue.
Because of the complex orbital mechanics involved in launching to the Moon, NASA would have had to launch Artemis I by Tuesday, September 6 as part of the current launch period. View a list of launch windows here:
August 23 – September 6
- 12 launch opportunities
- No launch availability on August 30, 31, and September 1
September 19 – October 4
- 14 launch opportunities
- No launch availability on September 29 and September 30
October 17 – October 31
- 11 launch opportunities
- No launch availability on October 24, 25, 26, and 28
November 12 – November 27 (preliminary)
- 12 launch opportunities
- No launch availability on November 20, 21, and 26
December 9 – December 23 (preliminary)
- 11 launch opportunities
- No launch availability on December 10, 14, 18, and 23
The periods above show launch availability through the end of 2022. Mission planners refine the periods based on updated analysis approximately two months before they begin and are subject to change.
When Artemis I is ready to launch, a range of personnel from NASA, industry, and several international partners will be on hand to support the mission. Before they get to launch day, the alignment of the Earth and Moon will determine when the Space Launch System (SLS) rocket with the uncrewed Orion spacecraft atop it can launch, along with several criteria for rocket and spacecraft performance.
Engineers identified key constraints required to accomplish the mission and keep the spacecraft safe in order to determine potential launch dates. The resulting launch periods are the days or weeks when the spacecraft and rocket can meet all mission objectives. These launch periods account for the complex orbital mechanics involved in launching on a precise trajectory toward the Moon while the Earth is rotating on its axis and the Moon is orbiting Earth each month in its lunar cycle. This results in a pattern of approximately two weeks of launch opportunities, followed by two weeks without launch opportunities.
Four primary parameters dictate launch availability within these periods. These key constraints are unique to the Artemis I mission and future launch availability beyond this flight will be determined based on capabilities and trajectories unique to each mission.
- The launch day must account for the Moon’s position in its lunar cycle so that the SLS rocket’s upper stage can time the trans-lunar injection burn with enough performance to successfully intercept the “on ramp” for the lunar distant retrograde orbit. Future configurations of the rocket, with the more powerful Exploration Upper Stage, will enable daily, or near-daily, launch opportunities to the Moon, depending on the orbit desired.
- The resulting trajectory for a given day must ensure Orion is not in darkness for more than 90 minutes at a time. This is required so that the solar array wings can receive and convert sunlight to electricity and the spacecraft can maintain an optimal temperature range. Mission planners eliminate potential launch dates that would send Orion into extended eclipses during the flight. This constraint requires knowledge of the Earth, Moon, and Sun along the planned mission trajectory path before the mission ever occurs. It also requires an understanding of the Orion spacecraft’s battery state of charge before entering an eclipse.
- The launch date must support a trajectory that allows for the skip entry technique planned during Orion’s return to Earth. A skip entry is a maneuver in which the spacecraft dips into the upper part of Earth’s atmosphere and uses that atmosphere, along with the lift of the capsule, to simultaneously slow down and skip back out of the atmosphere, then reenter for final descent and splashdown. The technique allows engineers to pinpoint Orion’s splashdown location. Also, on future missions it will help lower the aerodynamic breaking loads astronauts inside the spacecraft will experience, and maintain the spacecraft’s structural loads within design limits.
- The launch date must support daylight conditions for Orion’s splashdown. This is to initially assist recovery personnel when they locate, secure, and retrieve the spacecraft from the Pacific Ocean.