ARTEMIS UPDATE: NASA to Roll Rocket and Spacecraft Back to Vehicle Assembly Building to Prepare for Next Launch Attempt

View a list of launch windows

BREVARD COUNTY • KENNEDY SPACE CENTER • NASA – After standing down on Saturday’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, mission managers met and decided they will forego additional launch attempts in early September.

NASA was targeting Saturday at 2:17 p.m. EDT, the beginning of a two-hour window, for the launch of Artemis I, the first integrated test of NASA’s Orion spacecraft, Space Launch System (SLS) rocket, and the ground systems at the agency’s Kennedy Space Center in Florida.

Over the next several days, teams will establish access to the area of the leak at Launch Pad 39B, and in parallel 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.

To meet the requirement by the Eastern Range for the certification on the flight termination system, currently set at 25 days, NASA will need to roll the rocket and spacecraft back to the VAB before the next launch attempt to reset the system’s batteries.

The flight termination system is required on all rockets to protect public safety.

During today’s launch attempt, engineers saw 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 at reseating the seal were unsuccessful. While in an early phase of hydrogen loading operations 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, an inadvertent command was sent that temporarily raised the pressure in the system.

While the rocket remained safe and it is too early 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, Sept. 6 as part of the current launch period.

View a list of launch windows:

When Artemis I is ready to launch, a range of personnel from NASA, industry, and several international partners will be poised 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.

To determine potential launch dates, engineers identified key constraints required to accomplish the mission and keep the spacecraft safe. The resulting launch periods are the days or weeks where the spacecraft and rocket can meet 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.

There are four primary parameters that 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. The more powerful Exploration Upper Stage on future configurations of the rocket 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 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, as well as 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 use 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 and on future missions 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 to initially assist recovery personnel when they locate, secure, and retrieve the spacecraft from the Pacific Ocean.

The periods below 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.

September 19 – October 4 

■ 14 launch opportunities

■ No launch availability on Sept. 29 and Sept. 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 calendar also designates whether a launch on a particular date will be shorter in duration, of between 26 and 28 days, or longer in duration, of between 38 and 42 days.

The mission duration is varied by performing either a half lap or one and a half laps around the Moon in the distant retrograde orbit before returning to Earth and increases the number of days the mission can launch and meet the above constraints

In addition to the launch opportunities based on orbital mechanics and performance requirements, there also is an operational constraint driven by infrastructure at NASA’s Kennedy Space Center in Florida.

Because of their size, the sphere-shaped tanks used to store cryogenic propellant at the launch pad can only supply a limited number of launch attempts depending on the type of propellant. Liquid oxygen and liquid hydrogen are loaded in the rocket’s core stage and upper stage on the day of launch.

Should the launch subsequently be called off, there is a minimum of 48 hours until a second launch attempt can be made. There is then a 72-hour minimum before a third attempt can be made, due to the need to resupply the cryogenic storage sphere with more propellant from nearby sources. In any given week, no more than three launch attempts that include core stage tanking can occur.

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