NASA’s Artemis II SLS (Space Launch System) rocket poised to send four astronauts from Earth on a journey around the Moon next year may appear identical to the Artemis I SLS rocket. On closer inspection, though, engineers have upgraded the agency’s Moon rocket inside and out to improve performance, reliability, and safety.
SLS flew a picture perfect first mission on the Artemis I test flight, meeting or exceeding parameters for performance, attitude control, and structural stability to an accuracy of tenths or hundredths of a percent as it sent an uncrewed Orion thousands of miles beyond the Moon. It also returned volumes of invaluable flight data for SLS engineers to analyze to drive improvements.
For Artemis II, the major sections of SLS remain unchanged – a central core stage, four RS-25 main engines, two five-segment solid rocket boosters, the ICPS (interim cryogenic propulsion stage), a launch vehicle stage adapter to hold the ICPS, and an Orion stage adapter connecting SLS to the Orion spacecraft. The difference is in the details.
“While we’re proud of our Artemis I performance, which validated our overall design, we’ve looked at how SLS can give our crews a better ride,” said John Honeycutt, NASA’s SLS Program manager. “Some of our changes respond to specific Artemis II mission requirements while others reflect ongoing analysis and testing, as well as lessons learned from Artemis I.”
Engineers have outfitted the ICPS with optical targets that will serve as visual cues to the astronauts aboard Orion as they manually pilot Orion around the upper stage and practice maneuvers to inform docking operations for Artemis III.
The Artemis II rocket includes an improved navigation system compared to Artemis I. Its communications capability also has been improved by repositioning antennas on the rocket to ensure continuous communications with NASA ground stations and the U.S. Space Force’s Space Launch Delta 45 which controls launches along the Eastern Range.
An emergency detection system on the ICPS allows the rocket to sense and respond to problems and notify the crew. The flight safety system adds a time delay to the self-destruct system to allow time for Orion’s escape system to pull the capsule to safety in event of an abort.
The separation motors that push the solid rocket booster away after the elements are no longer needed were angled an additional 15 degrees to increase separation clearance as the rest of the rocket speeds by.
Additionally, SLS will jettison the spent boosters four seconds earlier during Artemis II ascent than occurred during Artemis I. Dropping the boosters several seconds closer to the end of their burn will give engineers flight data to correlate with projections that shedding the boosters several seconds sooner will yield approximately 1,600 pounds of payload to Earth orbit for future SLS flights.
Engineers have incorporated additional improvements based on lessons learned from Artemis I. During the Artemis I test flight the SLS rocket experienced higher-than-expected vibrations near the solid rocket booster attachment points that was caused by unsteady airflow.
To steady the airflow, a pair of six-foot-long strakes flanking each booster’s forward connection points on the SLS intertank will smooth vibrations induced by airflow during ascent, and the rocket’s electronics system was requalified to endure higher levels of vibrations.
Engineers updated the core stage power distribution control unit, mounted in the intertank, which controls power to the rocket’s other electronics and protects against electrical hazards.
These improvements have led to an enhanced rocket to support crew as part of NASA’s Golden Age of innovation and exploration.
The approximately 10-day Artemis II test flight is the first crewed flight under NASA’s Artemis campaign. It is another step toward new U.S.-crewed missions on the Moon’s surface that will help the agency prepare to send the first astronauts – Americans – to Mars.
Jonathan Deal
Marshall Space Flight Center, Huntsville, Ala.
256.631.9126
jonathan.e.deal@nasa.gov
