Get ready for the SLS launch targeting the Moon on August 29th

Around 7:30 a.m. EDT the Space Launch System rocket and Orion spacecraft for the Artemis I mission arrived atop Launch Complex 39B at NASA’s Kennedy Space Center in Florida after a nearly 10-hour journey from the Vehicle Assembly Building. The launch is scheduled for Aug. 29 at 8:33 a.m (a two-hour launch window) and it has been a long time in the making. Over the past few years, we’ve been reporting on how the Artemis mission has sometimes turned to AM for parts, from the Aerojet Rocketdyne (now part of Lockheed Martin) engines for the Space Launch System, or SLS for short, to the Orion capsule and interior parts built by Airbus and Lockheed Martin.

Stratasys and Phoenix Analysis & Design Technologies (PADT) teamed with Lockheed Martin Space to deliver the next-generation 3D printed parts for NASA’s Orion deep-space spacecraft. The parts were made using Stratasys advanced materials – including an ESD variant of the new Antero 800NA, a PEKK-based thermoplastic offering high-performance mechanical, chemical, and thermal properties. Recently the companies released images of Orion capsule’s seats for future manned missions.

As a pioneering space company, paving the way for today’s commercial space industry, Aerojet Rocketdyne has a long history in metal AM and was one of the first rocket engine manufacturers to adopt the technology. For more than two decades, the company invested extensive time and resources into leveraging this technology, focusing most of its energies on laser powder bed fusion (LPBF). It’s due to these efforts that the aerospace manufacturer was able to successfully design and integrate 3D printed end-use components for a variety of projects, among them the massive RS-25 engines that will carry the Artemis mission into space.

More recently the Aerojet Rocketdyne tuned to nTopology and Velo3D to make the “reaction control system” (RCS) on the future spacecraft lighter, smaller, and much less expensive than its predecessors.

The original Apollo RCS included four individual R-4D bipropellant thrusters, originally designed by Marquardt Corp., that used hypergolic (spontaneously igniting) nitrogen tetroxide and hydrazine as propellants. Every lunar lander and service module had four quads, each of which generated more than 100 pounds of thrust to control the spacecraft’s roll, pitch, and yaw during flight. Following a series of acquisitions, Aerojet Rocketdyne eventually took ownership of the R4-D RCS. The new, topology-optimized, 3D printed RCS is 1/5 the mass, 1/2 the size, and 1/3 the cost of a conventionally manufactured version. And since it contains far fewer components, it’s also easier to assemble, with much less chance of failure during operation.

Time to fly to the Moon on the SLS

The Artemis mission, including the ambitious SLS rocket and Orion capsule, has been marked by delays and growing costs but this is nevertheless a great moment for space exploration. It is the first flight of the agency’s Space Launch System (SLS) super heavy-lift launch vehicle and the first flight of the full Orion spacecraft. The Orion spacecraft for Artemis 1 was stacked on 20 October 2021, marking the first time a super heavy-lift vehicle has been stacked inside the Vehicle Assembly Building (VAB) since the final Saturn V with Skylab. The fully stacked vehicle was rolled out for launch on 17 August 2022.

To ensure the continued success of the mission, the Biden administration’s 2023 budget request included $7.5 billion for the Artemis moon program, a $1.1 billion boost the agency says will help keep the project on track for a lunar landing as early as 2025. But Artemis is expected to continue to drive all space-related activities, including collaborations with ESA and private companies such as SpaceX. Another $1.5 billion in the budget request would go development of new Human Landing System moon landers procured through competition following three initial Artemis landings using SpaceX vehicles, one unpiloted and two carrying astronauts.

In the coming days, engineers and technicians will configure systems at the pad for launch. Teams have worked to refine operations and procedures and have incorporated lessons learned from the wet dress rehearsal test campaign and have updated the launch timeline accordingly.  

Before the Artemis I mission launches on its way around the Moon, the launch team at Kennedy Space Center and supporting teams across the country will begin the launch countdown about two days before liftoff. Teams have and incorporated lessons learned from the wet dress rehearsal testing and have refined the launch timeline accordingly.

The launch countdown contains “L Minus” and “T Minus” times. “L minus” indicates how far away we are from liftoff in hours and minutes. “T minus” time is a sequence of events that are built into the launch countdown. Pauses in the countdown, or “holds,” are built into the countdown to allow the launch team to target a precise launch window, and to provide a cushion of time for certain tasks and procedures without impacting the overall schedule. During planned holds in the countdown process, the countdown clock is intentionally stopped and the T- time also stops. The L- time, however, continues to advance.

Countdown to Artemis

Below are some of the key events that take place at each milestone after the countdown begins.

L-46 hours 40 minutes and counting  

The launch team arrives at their stations and the countdown begins (L-46, 40 minutes hours)
Fill the water tank for the sound suppression system (L-46H – L-41H)
Liquid Oxygen (LO2)/Liquid Hydrogen (LH2) System Preparations for Vehicle Loading (L-46H – L-37H)
The Orion spacecraft is powered up if not already powered at Call to Stations (CTS) (L-42H – L-41H30M)
The interim cryogenic propulsion stage (ICPS) is Powered-up (L-38H30M – L-35H30M)
The core stage is powered up (L-34H – L-33H20M))
Final preparations of the four RS-25 engines (L-36H20M – L-31H)

L-32 hours and counting  

Core stage composite overwrapped pressure vessel (COPV) Pressurization to Flight Pressure (L-31M – L-22H)
Charge Orion Flight Batteries to 100% (L-30H – L-26H)
Charge core stage Flight Batteries (L-27H – L-21H)
The ICPS is Powered-up for launch (L-18H30M – L-15H30M)

L-15 hours and counting 

All non-essential personnel leave Launch Complex 39B (L-12H – L-10H)
Ground Launch Sequencer (GLS) Activation (L-11H15M – 9H15M)
Air-to-gaseous nitrogen (GN2) Changeover for vehicle cavity inerting (L-10H45M – Launch)

L-9 hours, 40 minutes and counting 

Built-in countdown hold begins (L-9H40M – L-7H10M)
The launch team conducts a weather and tanking briefing (L-9H40M – L-8H50M)
The launch team decides if they are “go” or “no-go” to begin tanking the rocket (L-8H40M)
Core Stage LO2 transfer line chilldown (L-8H15M – L-8H)
L-8 hours and counting

Core stage LO2 main propulsion system (MPS) chilldown (L-8H – L-7H20M)
Core stage LO2 slow fill (L-7H20M – L-7H5M)
Core Stage LO2 fast fill (L-7H5M – L-4H15M)
Core Stage LH2 chilldown (L-7H15M – L-7H5M)
Core Stage LH2 slow fill start (L-7H5M – L-6H15M)
Core Stage LH2 fast fill (L-6H15M – L-5H5M)
Core Stage LH2 topping (L-5H5M – L-5H)

L-5 hours and counting  

Core Stage LH2 replenish (L-5H – Launch)
ICPS LH2 ground support equipment (GSE) and tank chilldown (L-4H45M – L-4H30M)
ICPS LH2 fast fill start (L-4H30M – L-3H30M)
Orion communications system activated (RF to Mission Control) (L-4H20M – L-3H45M)
Core stage LO2 topping (L-4H15M– L-3H55M)
Core Stage LO2 replenish (L-3H55M – Launch)
ICPS L02 MPS chilldown (L-3H55M– L-3H45M)
ICPS L02 fast fill (L-3H45M– L-2H55M)
ICPS LH2 validation and leak test (L-3H30M – L-3H15M)
ICPS LH2 tank topping start (L-3H15M – L-2H55M)

L-3 hours and counting

ICPS/Space Launch System (SLS) telemetry data verified with Mission Control and SLS Engineering Support Center (L-2H55M – L-2H45M)
ICPS LO2 validation and leak test (L-2H55M – L-2H30M)
ICPS LH2 replenish (L-2H50M – Launch)
ICPS LO2 topping (L-2H30M – L-2H10M)
ICPS LO2 replenish (L-2H10M – Launch)

L-50 minutes and counting

Final NASA Test Director briefing is held (L-50M)

L-40 minutes and holding  

Built-in 30-minute countdown hold begins (L-40M)

L-15 minutes and holding   

The launch director polls the team to ensure they are “go” for launch

T-10 minutes and counting  

Ground Launch Sequencer (GLS) initiates terminal count (T-10M)
Orion ascent pyros are armed (T-6M)
Orion set to internal power (T-6M)
Core Stage LH2 terminate replenish (T-5M57S)
Core Stage auxiliary power unit starts (T-4M)
Core stage L02 terminate replenish (T-4M)
ICPS LO2 terminate replenish (T-3M30S)
ICPS switches to internal battery power (T-1M56S)
Core stage switches to internal power (T-1M30S)
ICPS enters terminal countdown mode (T-1M20S)
ICPS LH2 terminate replenish (T-50S)
GLS sends “Go for automated launch sequencer” command (T-33S)
Core stage flight computer to automated launching sequencer (T-30S)
Hydrogen burn off igniters initiated (T-12S)
GLS sends the command for core stage engine start (T-10S)
RS-25 engines startup (T-6.36S)

T-0  

Booster ignition, umbilical separation, and liftoff