NASA completes swing arm test on SLS launch platform

A view of NASA’s Space Launch System inside High Bay 3 of the Vehicle Assembly Building. This picture was taken Sept. 17 after retraction of work platforms ahead of the Umbilical Release and Retract Test. Credit: NASA/Frank Michaux

The swing arms on the mobile launch tower for NASA’s Space Launch System released and retracted Sunday night inside the Vehicle Assembly Building at Kennedy Space Center, another key test on the march toward liftoff of the Artemis 1 moon mission.

The Umbilical Release and Retract Test, or URRT, validated the way connections between the Space Launch System and its mobile launch tower will rotate or drop away at ignition and liftoff.

The swing arms and umbilicals provide power, communications, coolant, and propellant to the Space Launch System and the Orion spacecraft on the launch pad, according to NASA.

The umbilicals detached simultaneously from the nearly fully-assembled Space Launch System moon rocket in the VAB high bay, just as they will during liftoff from pad 39B at Kennedy to begin the Artemis 1 mission.

Artemis 1 is the first test flight of NASA’s Artemis program, which aims to return astronauts to the moon in the 2020s. The first test flight of NASA’s new Space Launch System heavy-lift rocket will send an unpiloted Orion crew capsule into lunar orbit for a demonstration mission lasting several weeks. The Orion spacecraft will return to Earth for a splashdown and recovery in the Pacific Ocean.

Future Artemis missions using the SLS will launch four-person teams of astronauts to the moon aboard Orion spaceships.

The Umbilical Release and Retract Test over the weekend verified previous testing that involved detachment of individual umbilicals from simulated SLS interfaces.

“Previous testing at the Launch Equipment Test Facility and in the VAB refined our designs and processes and validated the subsystems individually, and for Artemis 1, we wanted to prove our new systems would work together to support launch,” said Jerry Daun, arms and umbilical systems operations manager at Jabobs, NASA’s ground systems contractor at Kennedy.

“This test is important because the next time these ground umbilical systems are used will be the day of the Artemis 1 launch,” said Scott Cieslak, umbilical operations and testing technical lead, in a NASA statement.

Unlike the moving launch tables used by the space shuttle, the SLS mobile launcher includes a gigantic skyscraper-like structure on the platform itself. The 380-foot-tall (115-meter) Mobile Launcher features a metal tower atop a two-story base with six swing arms that will retract away from the rocket before launch.

In the shuttle era, pads 39A and 39B had fixed umbilical towers to provide astronauts, ground crews and swing arms access to the vehicle. The Apollo program’s Saturn 5 moon rocket used a similar pad setup as the SLS, but the Saturn 5’s mobile tower had nine swing arms.

The SLS tower and platform contain nearly 1,000 pieces of ground support equipment, routing power, data, water, propellants, air conditioning and other commodities to the launch vehicle and Orion crew capsule.

During the retract test Sunday, six swing arms and umbilicals simultaneously released from the Space Launch System.

At the top of the rocket, the Orion Service Module Umbilical detached from a mass simulator stacked on top of the rocket to mimic the weight of the Orion spacecraft, which will be stacked later.

Below the Orion mass simulator, the Interim Cryogenic Propulsion Stage Umbilical released and swung away from the rocket. Near the top of the SLS first stage, the Core Stage Forward Skirt Umbilical and the Vehicle Stabilizer System arms detached as they will during launch.

The Core Stage Inter-Tank Umbilical, located between the first stage’s liquid hydrogen and liquid oxygen tanks, and the Tail Service Mast Umbilical at the base off the rocket.

Other swing arms, such as the Crew Access Arm to be used by astronauts boarding the Orion capsule, were not part of the retract test. The crew arm moves away from the launcher in the final minutes of the countdown, not at the moment of liftoff.

“It was a great team effort to build, and now test, these critical systems,” said Peter Chitko, arms and umbilicals integration manager. “This test marked an important milestone because each umbilical must release from its connection point at T-0 to ensure the rocket and spacecraft can lift off safely.”

Unlike the moving launch tables used by the space shuttle, the SLS mobile launcher includes a gigantic skyscraper-like structure on the platform itself. The 380-foot-tall (115-meter) Mobile Launcher features a metal tower atop a two-story base with six swing arms that will retract away from the rocket before or during launch.

In the shuttle era, pads 39A and 39B had fixed umbilical towers to provide astronauts, ground crews and swing arms access to the vehicle. The Apollo program’s Saturn 5 moon rocket used a similar pad setup as the SLS, but the Saturn 5’s mobile tower had nine swing arms.

The SLS tower and platform contain nearly 1,000 pieces of ground support equipment, routing power, data, water, propellants, air conditioning and other commodities to the launch vehicle and Orion crew capsule.

The next milestone in Artemis 1 launch preparations will be the Integrated Modal Test, according to Tiffany Fairley, a NASA spokesperson.

Stingers, or shakers, will introduce vibrations to the rocket as it stands on its support posts at the base of the mobile launch platform. Sensors across the rocket and along the mobile launch tower, will measure the resonant response to the vibrations.

The rocket’s twin side-mounted solid-fueled boosters each stand on four vehicle support posts, with the vehicle’s weight holding it on the mobile platform — without the support of hold-down bolts — during stacking, rollout, and the countdown before liftoff.

That will be followed by removal of the Orion mass simulator and the Orion Stage Adapter test article. Those will be replaced by the flight-ready stage adapter and the real Orion spacecraft, which has been fueled with in-space maneuvering propellant and mated with its launch abort system at Kennedy.

Technicians recently completed installation of ogive fairings over the top of the Orion spacecraft, providing the aerodynamic shield that will cover the capsule during launch.

After additional tests to verify the mechanical and electrical connections between the Orion spacecraft and the SLS rocket, NASA will be ready to roll the fully-assembled launcher to pad 39B atop one of the agency’s Apollo-era crawler transporters.

The rocket will spend about a week on the pad before NASA’s launch team runs through a simulated countdown, culminating in the loading of super-hold liquid hydrogen and liquid oxygen aboard the launch vehicle.

Assuming that test, known as a wet dress rehearsal, is a success, teams will drain the propellant, safe the rocket, and return the Space Launch System to the Vehicle Assembly Building for final closeouts.

The time-sensitive work inside the VAB after the wet dress rehearsal will include the installation of pyrotechnic ordnance for the rocket’s separation systems and range safety destruct mechanism, which would terminate the flight if the rocket flew off course after liftoff.

Then the rocket will roll back out to pad 39B for another week of preparations ahead of the first launch attempt.

NASA Administrator Bill Nelson said Tuesday that the Artemis 1 mission could launch at the end of this year or early next year. But NASA officials privately say there is little chance of launch Artemis 1 by the end of December.

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