NASA Prepares to Stack Moon Rocket’s Core Stage

The fully stacked twin solid rocket boosters for NASA’s Space Launch System (SLS) rocket are mated atop the mobile launcher at the agency’s Kennedy Space Center in Florida as stacking and assembly activities for NASA’s Artemis I mission are underway. Crews from the spaceport’s Exploration Ground Systems and contractor Jacobs teams are currently preparing to lift the 188,000-pound core stage and place it in between the two solid rocket boosters. Teams will use a specialized crane to lift, place, and secure the core stage on the mobile launcher inside the spaceport’s iconic Vehicle Assembly Building (VAB).

The fully stacked twin solid rocket boosters for NASA’s Space Launch System (SLS) rocket
Credit: NASA

The 212-foot-tall core stage, which will provide more than 2 million pounds of thrust at launch, arrived at Kennedy on April 27. Together with the two solid rocket boosters, the SLS rocket will provide more than 8.8 million pounds of thrust to launch the first of NASA’s next-generation Artemis Moon missions. Soon after the core stage activity, crews will stack and integrate other elements of the rocket needed for launch preparedness testing that occurs inside the VAB before final assembly of the rocket and the addition of the Orion spacecraft. The mobile launcher serves as a platform not just for stacking but as a key supplier of power, communications, coolants, and propellant for the rocket and spacecraft before launch.

With Artemis, NASA will land the first woman and the first person of color on the Moon and establish sustainable exploration in preparation for missions to Mars. SLS and NASA’s Orion spacecraft, along with the commercial human landing system and the Gateway in orbit around the Moon, are NASA’s backbone for deep space exploration. SLS is the only rocket that can send Orion, astronauts, and supplies to the Moon in a single mission.

Orion Spacecraft Adorned with Iconic NASA Worm Logo

The historic worm logo is visible on the Orion spacecraft's crew module adapter inside the Multi-Payload Processing Facility.
NASA’s iconic worm logo has been added to the outward-facing wall of Orion’s crew module adapter (CMA) inside the Multi-Payload Processing Facility (MPPF) at NASA’s Kennedy Space Center in Florida. In the background is the Space Launch System rocket’s Interim Cryogenic Propulsion Stage, undergoing fueling and servicing inside the MPPF alongside the CMA. Photo credit: NASA/Glenn Benson

The Orion spacecraft receives another iconic NASA “worm” logo ahead of the Artemis I mission. On April 28 teams with the agency’s Exploration Ground Systems and lead contractor Jacobs completed painting the retro insignia on the outboard wall of the spacecraft’s crew module adapter (CMA) – the piece of hardware connecting the crew module to the European-built service module – inside the Multi-Payload Processing Facility (MPPF) at NASA’s Kennedy Space Center in Florida.

While a decal of the historic logo was added to the underside of the CMA in September 2020, having it painted on the siding of the spacecraft will make it visible as the spacecraft is poised atop the Space Launch System (SLS) rocket, awaiting liftoff from Kennedy’s Launch Pad 39B.

The worm logo was officially introduced in 1975, retired in 1992, and then made a comeback in 2020, just as NASA entered a new era of human spaceflight. In addition to its appearance on the CMA, the bright red logo also was painted on the SLS twin solid rocket boosters in August 2020.

The Orion spacecraft and Interim Cryogenic Propulsion Stage (ICPS) – the upper stage of the rocket responsible for sending Orion on its journey around the Moon – are currently being fueled and serviced in the MPPF. Once fueling is complete, Orion will move to the Launch Abort System Facility for integration of its launch abort system, while the ICPS will move to the Vehicle Assembly Building to be stacked on the mobile launcher.

Artemis I will be the first integrated test of SLS and Orion and will pave the way for landing the first woman and first person of color on the lunar surface. The mission will be a stepping stone for deep space exploration, leading the agency’s efforts under the Artemis program for a sustainable presence on the Moon and preparing for human missions to Mars.

Click here for a video of the logo being added to the CMA.

Fueling Underway For Artemis I Launch

A view of the Interim Cryogenic Propulsion System in the Multi-Payload Processing Facility at NASA's Kennedy Space Center in Florida.
A view of the Interim Cryogenic Propulsion System in the Multi-Payload Processing Facility at NASA’s Kennedy Space Center in Florida on Feb. 18, 2021. Photo credit: NASA/Glenn Benson

Teams with NASA’s Kennedy Space Center Exploration Ground Systems and primary contractor, Jacobs, are fueling the Orion service module ahead of the Artemis I mission. The spacecraft currently resides in Kennedy’s Multi-Payload Processing Facility alongside the Interim Cryogenic Propulsion System (ICPS), the rocket’s upper stage that will send Orion to the Moon. After servicing, these elements will be integrated with the flight components of the Space Launch System, which are being assembled in the Vehicle Assembly Building.

Technicians began loading Orion’s service module with oxidizer, which will power the Orbital Maneuvering System main engine and auxiliary thrusters on the European-built service module ahead of propellant loading. These auxiliary thrusters stabilize and control the rotation of the spacecraft after it separates from the ICPS. Once the service module is loaded, teams will fuel the crew module to support thermal control of the internal avionics and the reaction control system. These 12 thrusters steady the crew module and control its rotation after separation from the service module.

Once Orion servicing is complete, teams will fill the ICPS. This liquid oxygen/liquid hydrogen-based system will push the spacecraft beyond the Moon for the test flight under the agency’s Artemis program. In several weeks, when fueling is complete, Orion will move to the center’s Launch Abort System Facility to integrate its launch abort system, and the ICPS will move to the Vehicle Assembly Building to be stacked atop the mobile launcher.

Green Run Update: Post-Test Press Briefing at 7 p.m. ET.

Teams from NASA’s Space Launch System (SLS) Program conducted a successful full-duration hot fire test for more than 8 minutes. See press release HERE.

To learn more, tune in to NASA TV for a post-test briefing at 7 p.m. EDT at NASA Live.

Learn more about Green Run, and check back at this blog for updates on the SLS core stage hot fire test. Watch a replay of the test on NASA Television or NASA’s YouTube channel. For all the photos and videos related to the test, visit, the Green Run Album on NASA Images.org.

Video of today’s test can be downloaded there as well.

Green Run Update: Engines Igniting as Hot Fire Gets Underway

The hot fire is underway for the Space Launch System (SLS) rocket core stage at NASA’s Stennis Space Center near Bay St. Louis, Mississippi.

Engine ignition began at approximately six tenths of a second before T-0, beginning with Engine 1, then Engines 3, 4, and 2 ignited in sequence a few hundredths of a second apart. The test is expected to last about 8 minutes and will include three different power levels for the engines, as well as  engine gimballing, or pivoting, movements to simulate flight steering commands. Depending on the rate propellant is burned, the time is estimated to range from 485 to 493 seconds to simulate launch.

core stage RS-25 engines
All four of the Artemis I core stage RS-25 missions served on numerous space shuttle missions. Now they will launch the Artemis I mission to the Moon. Aerojet Rocketdyne is the prime contractor for the engines.

Learn more about Green Run, and check back at this blog for updates on the SLS core stage hot fire test.

Green Run Update: Terminal Countdown Sequence Started

The test conductor polled the team and has approved the decision to proceed with the terminal countdown that includes the final 10 minutes before the hot fire. During the terminal countdown, the team is executing the autonomous launch sequence that simulates the countdown for the Artemis I launch. The test transitions from ground control to on-board software control of the core stage and so the test is fully automated starting at T-30 seconds.

Key milestones during the final count include starting the core stage auxiliary power units (CAPUs) for each engine to provide power for the thrust vector control systems that gimbal, or move, the engines during the test, purging the engines with nitrogen gas to ensure they are completely clean before flowing propellant, moving the engines into position for engine start, and switching the core stage from external test stand power to internal battery power. The engines begin to power up 6 seconds before T-0.

Propellant barges docked near the B-2 Test Stand

Below are the key milestones in the terminal countdown:

  • T-4 minutes: Core Stage Auxiliary Power Unit CAPU Start
  • T-3 minutes: Engine Purge Sequence Start
  • T-2 minutes, 30 seconds: Pre-Ignition Gimbal Sequence Started
  • T-1 minute, 30 seconds: Core Stage to Internal Power
  • T-33 seconds: Automated Launch Sequence (ALS) Start
  • T-6 seconds: Engine Start Commands

The B-2 test stand flame deflector cooling water also will begin flowing to protect the deflector from superheated engine exhaust about a minute and a half before firing up the engines, and test stand acoustic suppression water flow will begin about 65 seconds before hot fire.

Hear the test conductor in the final minutes before the countdown during live coverage underway on NASA Television and the agency’s website.

Learn more about Green Run, and check back at this blog for updates on the SLS core stage hot fire test.

Green Run Update: NASA TV Coverage Underway for Hot Fire Test

Countdown is continuing for the hot fire test of the core stage for NASA’s Space Launch System (SLS) rocket. The test is expected to start soon and last about 8 minutes to simulate launch and ascent of the SLS to orbit.

NASA Television coverage has begun. Watch live: http://www.nasa.gov/live

Teams powered up the core stage’s avionics systems Tuesday, Mar. 16, and began the countdown for the hot fire test earlier today. The team is continuing to closely monitor core stage and facility performance before proceeding into the final phase of the test: the terminal countdown leading to the hot fire.

During this test, the team has repeated many of the major milestones marked during the wet dress rehearsal and the first hot fire test, including chilling the main propulsion system and completely filling both propellant tanks. Coming up at 10 minutes before the test, the test conductor will poll the team who will give the final “go/no go” to proceed with the hot fire test.

Learn more about Green Run, and check back at this blog for updates on the SLS core stage hot fire test.

 

Green Run Update: Tanking Complete for Rocket Hot Fire Test

Engineers have completed tanking for the hot fire test of NASA’s Space Launch System (SLS) rocket core stage at the agency’s Stennis Space Center, and the countdown is proceeding normally.

The liquid hydrogen tank holds 537,000 gallons of liquid hydrogen, cooled to minus 423 degrees Fahrenheit. The liquid oxygen tank holds 196,000 gallons of liquid oxygen, cooled to minus 297 degrees Fahrenheit. After tanking is complete, the team will continue chilling down the liquid oxygen propellant to condition it before the hot fire. While they are conditioning the liquid oxygen, they replenish the liquid hydrogen as it boils off due to temperature fluctuations as the propellant is loaded. The tanks can be loaded up to 22 times for testing and launches.

core stage liquid hydrogen tank
This image shows the core stage liquid hydrogen tank at NASA’s Michoud Assembly Facility in New Orleans where it and the rest of the core stage where built and assembled. The flight core stage for the Artemis I mission is being tested today. Boeing, the prime contractor for the core stage, has already manufactured liquid hydrogen tanks for the Artemis II and Artemis III lunar missions.

This part of the test timeline is also important as it pertains to simulating launch. During a launch, many activities will be happening on the pad at this time, such as loading the crew. The hot fire test provides an opportunity to demonstrate that the core stage can remain in a stable configuration and be replenished as needed before engine firing to launch the rocket.

Learn more about Green Run, and check back at this blog for updates on the SLS core stage hot fire test.

Green Run Update: Test Teams Gives “Go” to Proceed with Tanking 

The test team conducted a pre-test briefing in the Test Control Center at the B test complex at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, and gave a “go” to proceed with testing and to fill the propellant tanks. 

Over the next several hours, the teams will monitor the systems and load more than 700,000 gallons of cryogenic, or supercooled, liquid oxygen and liquid hydrogen that will be fed to the four RS-25 engines during the hot fire test later today. 

The hot fire will last up to 8 minutes and is scheduled to take place during a two-hour window that begins at 3 p.m. EDT. Live coverage will begin 30 minutes before the test on NASA Television and the agency’s website. 

SLS core stage
This infographic provides information on the core stage including its two large propellant tanks.

Learn more about Green Run, and check back at this blog for updates on the SLS core stage hot fire test. 

Green Run Update: Hot Fire Exposes Core Stage to Spaceflight Stresses

During NASA’s Green Run hot fire test, the team will be especially interested in several key operations when testing the Space Launch System (SLS) rocket core stage under conditions it may experience during a variety of deep space missions.

Green Run, an end-to-end system test of the core stage with Artemis I flight hardware, will help validate the core stage design. One of the main questions Green Run will answer is: How does the integrated core stage perform during a series of dynamic operations it may experience during launch and ascent to deep space? The test is not only for environments and operations that the rocket’s core stage will encounter on Artemis I, but also for those it will undergo during future missions.

This video explains more about the operations occurring during the Green Run hot fire.

Hot fire day begins with filling the liquid oxygen and liquid hydrogen tanks with more than 700,000 gallons of propellant. After the supercold propellant is loaded and the core stage systems are conditioned to cryogenic temperatures as low as minus 423 degtrees Fahrenheit, the test conductor will poll the team. When everything is ready, they will proceed with the terminal countdown that includes the final 10 minutes before the hot fire. During the terminal countdown, the team will initiate the autonomous launch sequence that simulates the countdown for the Artemis I launch. Then, the test transitions from ground control to on-board software control of the core stage so that the test is fully automated starting at T-30 seconds.

The core stage RS-25 engine ignition starts at approximately six seconds before T-0, beginning with Engine 1, followed by Engines 3, 4, and 2, each ignited in sequence a few hundredths of a second apart. Recording data on how the stage performs at T-0 and as the engines ramp up to 109 percent power is one critical test operation. Another is when the engines are throttled down to 95 percent, just as they are throttled down in flight at Max-Q, or maximum dynamic pressure when aerodynamic forces put the greatest stress on the rocket.

The team will also test the margins of the core stage thrust vector control system that gimbals, or moves, each engine in a specific pattern. Each engine has its own thrust vector control system that is essential for moving the engine to control the rocket’s flight. Depending on the trajectory flown, the thrust vector control system can gimbal the engines to direct thrust and thus the rocket’s path. The first gimbaling occurs a little over a minute into the test.

An important part of the hot fire occurs when this system begins rapidly moving the engines in specific patterns that are more extreme than those planned for Artemis missions. This occurs around 2 minutes and 10 seconds into the test. This test is called the frequency response test because it measures the stage’s frequency as the thrust vector control system gimbals the engine. The test ensures the thrust vector control system’s response is demonstrated under a variety of flight-like conditions. This is a very dynamic portion of the core stage hot fire test and understanding the thrust vector control system and the core stage’s response across a range of frequencies is important to understand the stage’s performance during flight.

To ensure SLS can safely send humans to space, NASA will use data from the Green Run test campaign, along with modeling and analysis, to show the core stage design can fly not only on Artemis I, but also for many deep space missions.

For updates on Green Run progress, check back at this blog. NASA TV coverage will begin about 30 minutes before the test. For more information about SLS Green Run, visit https://www.nasa.gov/artemisprogram/greenrun