Pre launch preparations
The flight test article (FTA), consisting of the production LAS and the Crew Module Separation Ring assembly, was moved to Launch Complex 46 in late May for mating to the Abort Test Booster (ATB), which was assembled on the launch pad in April. The two systems make up the full flight test vehicle (FTV) for AA-2.
(Photo Caption: Elements of the AA-2 Abort Test Booster (ATB) are lifted into place at Launch Complex-46 in April. From left to right, the SR-118 solid rocket motor is lifted onto the launch mount on April 12, the TRS/GCA assembly is lifted up into the mobile service tower to stack on the SR-118 on April 16, and finally the aeroshell that fits over them is lifted for installation on April 18.)
An SR-118 Northrop Grumman solid rocket motor that provides the propulsion for the test was the first element erected on the launch pad at LC-46. Its original purpose was as the first stage of the Peacekeeper Inter-Continental Ballistic Missile (ICBM). The Peacekeeper program was deactivated in 2002 and today the motors in the inventory are used for commercial purposes such as space launches.
A combination Thrust Reaction Structure (TRS)/Guidance Control Assembly (GCA) part was then attached to the top of the motor, followed by aeroshells that were cover the SR-118 motor and TRS/GCA package. The Orion hardware reaches 5.5 meters in diameter at its widest and the TRS and aeroshells connect the smaller diameter motor and streamline the overall test vehicle. Additional ballast adds weight to the vehicle.
“This is probably one of the heaviest that we’ve had for the Rocket Systems Launch Program, it’s over 300,000 pounds,” Air Force Lieutenant Colonel Ryan Rose, Chief of the Small Launch and Targets Division, said. “The motor itself is 105,000 and then we have about 100,000 pounds of ballast on there as well, so it’s going to be one of the heaviest Peacekeeper missions that we’ve had.”
The separation ring simulates aspects of the Crew Module Adapter that the Crew Module and LAS attach to.
The combined Crew Module Separation Ring (CSR) assembly was integrated at the Johnson Space Center in Houston last year and shipped to KSC in December. Overall test preparations were slowed down by a five-week long partial government shutdown, but eventually checkouts with the booster GCA and LAS avionics were completed and the LAS was attached to the CSR in the Launch Abort System Facility (LASF) at KSC.
After the full test vehicle was mated, the final connections between the test article and the booster were completed, some additional panels were installed, and the test team went through a series of dress rehearsals in June.
The centerpiece of the AA-2 test is the LAS and the system is the only production Orion hardware taking part in the test. The system is centered around three solid-rocket motors, the abort motor, the attitude control motor (ACM), and the jettison motor.
Northrop Grumman is the prime contractor for the first two motors, which fire together to execute an abort. Aerojet Rocketdyne is the prime for jettison motor, which is used on every Orion launch.
For nominal launches, the LAS is jettisoned in the upper atmosphere to improve overall launch vehicle performance to orbit insertion. In an abort case, the jettison motor separates the LAS from the Crew Module at the end of the LAS firing sequence. The Crew module and the LAS elements together make up the Launch Abort Vehicle (LAV) that separates from the test booster in flight.
The motors are stacked with the long abort motor at the bottom, the ACM at the top, and the jettison motor in between.
The abort motor fires upward through four reverse flow nozzles that turns the exhaust back around. During the transition from Constellation to Exploration Systems Development, the maximum thrust for the motor was adjusted from 500,000 pounds to 400,000 pounds thrust.
“That will be easier on the crew but [also]…on the crew module, the weld joints, all the avionics, and everything that is inside the crew module, it doesn’t put as much stress on them, so we don’t have to test them [to] as high [requirements],” Dr. Roger McNamara, Director of the Orion Launch Abort System for Lockheed Martin, explained.
The ACM starts at the abort command with the abort motor to steer the separating Launch Abort Vehicle. “It’s continuous throughout the duration of the abort firing and actually until it flips the Crew Module over,” Kirasich explained. “Actually flipping the Crew Module over it’s just doing a pitch maneuver itself, but it’s a closed-loop control.”
There are eight pintles in the Attitude Control Motor that steer the combined LAS/CM “Launch Abort Vehicle” during an abort. “It’s the valve that modulates the thrust out each one of the nozzles,” Kirasich said.
David Daniewicz, Chief Engineer for the Jettison Motor at Aerojet Rocketdyne, said the jettison motor generates about 40,000 pounds of thrust for about one and a half seconds. The motor weighs about 900 pounds total, with the propellant weighing taking about 350 pounds of that weight.
The rockets in the LAS are attached to the Crew Module by the Motor Adapter Truss Assembly, both structurally and electronically. “The MATA consists of several pieces but the main ones are the Motor Adaptor Cone (metallic), Truss assembly (composite), Connector Ring Lanyard pull and LAS retention and release (R&R) mechanisms interface (6),” Sandy Mossman, Lockheed Martin Orion LAS and AA-2 Integration System & Integration Engineer, said in an email. “The Crew Module attaches to the LAS via the R&Rs. The lanyard pull is for the electrical harness interfaces between the Crew Module and the LAS.”
A relatively recent change was to the adapter cone, going from a composite structure to a metallic one. “[The] Program decision to switch was in the spring 2016,” she said.
“The change to a metallic MATA cone was after the EM-1 (Artemis 1) MATA was built. The AA-2 and Artemis 2 and up will have a metallic MATA cone which reduced weight and improved performance for the abort condition.”
(Photo Caption: A metallic MATA cone at its AMRO Fabricating Corporation manufacturing facility in California. The cone structure was changed from a composite material to metal after the Exploration Flight Test-1 mission.)
Construction of the EM-1/Artemis 1 LAS hardware started before AA-2 was advanced in the sequence, and that LAS will fly with old composite MATA cone. “The switch was after EFT-1 which flew the composite,” Mossman added.
“AA-2 will be the first flight with a metallic MATA Adapter cone. The adapter cone was the only switch. The trusses remain composite.”
With the ESD programs in development, early launches and development tests like AA-2 are capturing in-flight data from development flight instrumentation. As with other flight vehicle elements, this production LAS has its share of DFI in addition to the operational instrumentation and command and control connections.
The vehicle management computers in the Crew Module fly Orion, including in an LAS abort mode. The Orion computers talk to avionics in the LAS.
“The ACM controller responds to thrust commands from the Crew Module,” Mossman explained. “The Abort Motor and Jettison Motor are not commanded by the ACM controller. They are ignited by pyro signals from the Crew Module.”
Mossman elaborated on the DFI-heavy avionics configuration for the test: “For AA-2 the avionics consists of the Vehicle Control System on the ACM, a NASA provided RF communication system to broadcast data through the LAS forward interstage (FIS) antennae and four NASA provided RDAU (Remote Data Acquisition Unit) boxes,” she said.
“The RDAUs compile Developmental Flight Instrumentation (DFI) data and transmits the data to the Crew Module,” she added. “The Crew Module compiles the data with other Crew Module DFI on operational flight data in its avionics system. This data is sent back up the LAS and out the LAS antennae using the RF system on the FIS. The ACM avionics are the only part that will fly in future missions.”
A four-piece, ogive-shaped fairing covers the Crew Module both to streamline the airflow over the spacecraft during atmospheric flight and to protect it from the blast of the abort motor if it is activated. Additional fillet fairing panels fit over the abort motor casing above the MATA. The panels are made of composites.
“They’re laid up, the composite fabrics are laid up in Denver, Sunnyvale, and San Diego and then they’re shipped here and they come in as just raw composite pieces in a rough shape,” Kirasich noted. Finishing and detailing is done at MAF before they are transported to Kennedy Space Center.
Given AA-2’s earlier positioning in the test flight sequence after Artemis 1, construction began after the hardware for that mission. “Artemis 1 will fly the composite MATA where AA2/Artemis 2 fly the metallic system,” Mossman noted.
“Artemis 1 & 2 have an avionics communication pallet in the FIS where AA-2 has the NASA supplied smaller system. AA-2 has a much larger DFI system and four RDAUs where Artemis 1 & 2 have smaller systems.”
Artemis 1 LAS integration underway
The LAS hardware converges on the LASF at KSC for assembly and finally integration with the Orion spacecraft. With the AA-2 hardware ready for launch, the LAS hardware for Artemis 1 is now being shipped to the LASF to be built up in preparation for that flight in 2021 or perhaps late 2020.
The inert abort motor for Artemis 1 from Northrop Grumman and the jettison motor from Aerojet Rocketdyne have been delivered to KSC to begin integration of the LAS tower. “We have this trailer where the whole tower, the motor assembly, stacks,” Blake Watters, Launch Abort System Lead Engineer with Lockheed Martin, said. “So you’ve got the abort motor which comes in with the aft interstage, the jettison motor goes on the front of that.”
“Then you go to the forward interstage and the attitude control motor and the nose cone. And then on the aft end you’ve got the motor adapter truss assembly, the connecting piece between the abort motor and the top of the Crew Module.”
“There’s a [little] play with the way you do the sequence, but that’s essentially the tower you build on the trailer and from there is where you do the mate to the Crew Module,” Watters added.