Screenshot from NASA Webcast of the Artemis I launch. In half an hour there WILL be daylight
Mission Rundown: NASA - SLS block 1 - Artemis I
Written: November 15, 2022
Only the pricetag is bigger
NASA is set to launch the Orion spacecraft to a distant retrograde lunar orbit on the Space Launch System (SLS) for its maiden launch. Launching from Launch Complex 39B, at the Kennedy Space Center, in Florida, the Artemis I mission will certify both Orion and the SLS Block 1 rocket for crewed spaceflight.
The next mission–aptly named Artemis II–will be crewed, and bring a yet-announced crew to lunar orbit (but will not land on the lunar surface). Just like Apollo 8.
This orbit will mark the farthest a spacecraft meant for crew will have been from Earth at 450,000 km. Additionally, this mission will mark the longest a spacecraft will have free-flown (not docked to another spacecraft or space station), with a planned mission duration of 42 days. At the time of launch, the SLS Block 1 rocket will be the most powerful rocket in the world (although, SpaceX’s Starship rocket will take this record shortly).
In addition to the Orion spacecraft, SLS will launch 10 6U smallsats as part of the low-cost CubeSat mission. They are mounted on the Stage Adapter. It is currently unknown when these payloads will be deployed. Read this article about them.
It’s the final countdown
The countdown to the launch of Artemis I is incredibly long, starting almost 48 hours prior to the actual rocket launch, and I’m guessing ingress of a crew will happen 8 hours prior to fueling the rocket and initiating the terminal countdown of the launch.
With a promising weather forecast predicting a 90% chance of acceptable conditions throughout the window, all eyes were largely on the late afternoon and evening hours of Tuesday, Nov. 15, when Launch Director Charlie Blackwell-Thompson and her team began fueling the SLS – a sequence that has given the team issues to work through in previous wet dress rehearsals (WDRs) and launch campaigns.
The main focus was on the liquid hydrogen (LH2) side of the propellant environment, where teams have struggled against leaks on the ground side while also working through feed pressure alterations.
While regular pumps are used to move liquid oxygen (LOX) from its storage sphere on the northwest corner of 39B into SLS, a lighter pressure difference is all that is used to move the more volatile LH2 from its storage sphere on the northeast corner of the pad.
After using the original pressure profile during the WDRs and first two launch attempts, all of which saw leaks on the LH2 ground side that exceeded the four percent ambient hydrogen concentration safety limits around the fuel lines on the LH2 Tail Service Mast Umbilical (TSMU), NASA tested a kinder, gentler fueling process this time.
Only a minor leak was detected in the Launch Platform hydrogen pipelines, to which a Red Team of engineers was dispatched in order to torque down the bolts to tighten the leaking seal of a valve. The Red Team was successful in their endeavor.
The countdown began on Nov. 14 with Call To Stations at 1:24 am EST (06:24 UTC) ahead of the clock starting to count backward to zero at 1:54 am EST (06:54 UTC). The count is timed for liftoff at the opening of the two-hour launch window Wednesday morning and includes an extra hour of hold time than the previous countdowns.
There are two ways of counting down where the first L count is a general countdown of planned events in sequence with build in stops or holds towards the actual sharp T count or Terminal Countdown where nothing must go wrong.
The staggered start sequence of the four RS-25 engines was commanded by the on-board flight computers at T-06.36 seconds, with each engine starting 120 milliseconds apart to ensure that acoustic energy levels around the vehicle, as well as engine start transients, stay within vehicle limits.
It took each RS-25 approximately three seconds to arrive at 90% of rated thrust, at which point engine health checks began. If all engines and systems onboard the rocket are functioning nominally, the command to ignite the Solid Rocket Boosters (SRBs) and disconnect the T0 umbilicals is sent as the countdown reaches zero.
Once ignited, the SRBs commit the vehicle to flight as there is nothing but its own mass holding it down to the launch pad. There are no hold-down bolts on the SLS. Liftoff was clocked to 01:47:44 am EST on November 16, 2022. link
After rising vertically for about seven seconds, SLS’s computers command the engines and boosters to gimble their thrust vector control systems (TVCs) to roll, pitch, and yaw the vehicle onto the proper azimuth, or compass heading, needed to obtain the correct initial Earth parking orbit to set up for the trans-lunar injection (TLI) burn.
A difference of 18.5 degrees between 70.1 and 88.6 in the compass heading over the two hour window will after 43 minutes shift the Azimuth heading to 76.8 degree east. link
[(18.5 degrees : 120 minutes) x 43 minutes] + 70.1 = 76.8 degrees
As SLS and Orion accelerated toward space, the stack reached max-q, the moment of maximum stress on the rocket, at T+01:10 as the vehicle climbed through 12.9 km (42,500 feet) altitude and accelerated through 447 m/s or meters per second (1,000 mph).
At about T+02:12 the twin five-segment SRBs separated from the Core Stage. Under a nominal mission profile, SLS is traveling around 1,417 m/s (3,170 mph) while being 48.1 km (158,000 feet) in altitude. At T+5:24 they will crash ~400 km downrange.
Approximately one minute later, with the vehicle now flying above the majority of Earth’s atmosphere, the aerodynamic elements protecting Orion should now safely be jettisoned. Three fairing panels surrounding the European Service Module (ESM) will separate at T+03:13 seconds, followed immediately by the Launch Abort System (LAS) at T+03:19. To me it’s the launch abort tower. I think they will crash ~5-600 km downrange.
The core stage continued to power the ascent for several more minutes, targeting an unstable 30 x 1805 km orbit. The 30 km perigee, while above the Earth’s surface, is well within the atmosphere. This trajectory ensures that the Core Stage safely reenters during its first orbit, breaking apart over a designated area of the Pacific Ocean.
After Main Engine Cutoff (MECO) at T+ 08:04 the Inner Cryogenic Propulsion Stage or in an alphabet soup form known as the ICPS and Orion stack will separate from the core stage at T+08:16. At T+1:26:00 it will crash ~33 800 km downrange east southeast of Hawaii.
For ICPS and Orion to avoid the same fate as the core stage, the spacecraft coasts up to apogee before performing the first of two ICPS burns.
During this coast phase, Orion’s four solar arrays deploy, beginning about T+18:20 after liftoff. Solar array deployment takes about 12 minutes. The solar arrays will fold back during all subsequent burns to minimize stress loads on the Solar Panel hinges.
The 1805 km apogee burn gives the combined ICPS and Orion stack enough energy to raise the perigee to 185 km and enter into a low earth orbit; a second lunar injection burn will send the combined ICPS and Orion stack to the Moon.
The Inner Cryogenic Propulsion Stage is itself a slightly modified Delta Cryogenic Second Stage (DCSS) from United Launch Alliance’s Delta IV rocket family, and is powered by a single RL-10-B-2 engine. The ICPS perigee raise burn at T+51:22 lasting 22 seconds.
Following another coast phase for ICPS and Orion until perigee, the Trans-Lunar Injection (TLI) burn occurs. This maneuver raises the orbital apogee out to the Moon, allowing Orion to later insert itself into the desired Distant Retrograde Orbit. This second ICPS burn begins at T+01:37:00 lasting approximately 18 minutes.
Orion separates from ICPS at T+2:06:10. Shortly after, and T+2:07:31, Orion’s thrusters will fire briefly to distance the spacecraft from ICPS. First then will ICPS begin deployment of 10 CubeSats mounted inside the Orion adaptor ring. These secondary payloads are all bound for individual missions to the moon except one bound for a rendezvous with an asteroid in heliocentric orbit.
Flightplan of Orion. Note the ICPS trip around the Moon before leaving to orbit the Sun. Source
With Orion on its Trans-Lunar trajectory, ICPS conducts one final burn at T+3:30:00 to safely dispose of itself into a heliocentric orbit.
Roughly eight hours after launch, Orion will perform its first trajectory correction burn, which will be the first burn of the ESA Service Module. Orion will spend the next five days heading toward the Moon. On day six, Orion will perform a powered flyby of the Moon, getting to within 60 miles of the surface.
Orion will spend three days getting into a Distant Retrograde Orbit (DRO) –an extremely stable orbit due to the interactions between the spacecraft and Lagrange points. Ten days after launch, Orion will be in DRO, and on day 11 Orion will surpass the Apollo 13 record for the furthest a crew spacecraft has been from the Earth.
Days after entering into DRO, Orion will conduct yet another burn to leave DRO. Orion will then reach its farthest point from Earth, at 450,000 km. From there, Orion will make its way home, flying past the Moon for the last time, and reentering and splashing down on day 25. Orion is expected to hit the Earth’s atmosphere at 40,000 kph. During reentry, the spacecraft will be surrounded by plasma that is roughly 3,000 Kelvin (2727 C).
The Space Launch System
Artemis I (originally known as Exploration Mission 1 (EM-1)) was announced in 2012 following the cancellation of the Constellation program. With it, NASA announced that the SLS rocket would bring the Orion spacecraft and European Service Module, which is based on the Automated Transfer Vehicle (an ISS resupply spacecraft), to lunar orbit. With the goal of bringing humans back to the moon safely and sustainably (unlike Apollo), the Artemis program is very different from the Apollo program.
To start, the most notable difference is that the Artemis program will require several launches to return humans to the lunar surface, whereas Apollo only required a single launch. This allows for the program to bring significantly more to the surface, with the Starship Human Landing System (HLS) being able to deliver up to 150 metric tonnes to the surface–an unprecedented amount of cargo.
The Space Launch System is a fully-expendable super heavy-lift launch vehicle developed by NASA and subcontracted out to Boeing, ULA, Aerojet Rocketdyne, and Northrop Grumman. Following the cancellation of the Constellation program, the SLS vehicle is a replacement for the Ares I and Ares V launch vehicles. Alongside Starship, the SLS will be the US’ access to deep space for the coming decades.
SLS is a shuttle-derived rocket, utilizing the same RS-25 engines, two solid rocket boosters, and a similar looking orange core stage.
The SRBs on SLS are an extended version of the Space Shuttle’s SRBs–the SRBs flown on the shuttle were four segments tall, whereas the SRBs on SLS are five segments tall. This means that the SRBs produce roughly 25% more thrust, at 16 million Newtons each, and have an exhaust velocity of 2.37 km/s.
For Artemis I, the ring segment casings for the SRBs are all flight-proven, each having supported several previous Space Shuttle missions. However, unlike with the Space Shuttle, these two SRBs are not going to be recovered.
The core stage of SLS is a one burn sustainer stage that runs on liquid hydrogen (LH2) and liquid oxygen (LOx). A sustainer stage is a stage that is lit on the ground and remains lit until orbit. The main propulsion system is attached to the bottom of the core stage and is home to the four RS-25 engines.
Similar to the SRB casings, all four of the RS-25s on the Artemis I mission are flight-proven, having each supported many shuttle flights. Unfortunately, the four shuttle engines will be expended on this flight. The core stage is 65 meters tall and 8.4 meters wide. The stage uses autogenous pressurization to backfill the tank.
The RS-25 is a fuel-rich dual-shaft staged combustion cycle engine that runs on LH2 and LOx. The engine produces 2.279 MN of thrust in a vacuum, with an ISP of 4.436 km/s.
The second stage of SLS for the Artemis I mission is the Interim Cryogenic Propulsion Stage (ICPS), which is derived from the Delta Cryogenic Second Stage. ICPS is 5 meters wide and hosts a single RL10B-2 engine. This engine produces 110 kN of thrust with an exhaust velocity (ISP) of 4.565 km/s. The engine is capable of being restarted 15 times but is only scheduled to start three times.
ICPS has 10 CubeSats mounted inside its Orion adaptor ring. These secondary payloads will be deployed in sequence from timers or initiated from ground signals.
The ESA Service Module
The European Service Module is equipped with a single Orbital Maneuver System AJ-10 rocket engine from the Space Shuttle era that have been reused 19 times, before this last 20th flight to the Moon with the Orion Multipurpose Crew Vehicle. Photo
Graphic overview on the European Service Module with structure and function. Source: link
Funding to the Service Module was provided by ESA (European Space Agency) and it was built by ESA contracting Airbus Space, the service module will provide power, air and water to the Orion spacecraft on missions to extend human existence to the Moon.
As the Orbital Maneuver System engine was designed and used for the Space Shuttle, engineers must ensure that the engine will work as needed on the Orion spacecraft that has different requirements and is being launched on a different rocket.
Graphic from ESA with the main tanks and maneuver thrusters inside the Service Module. link
The focus on these firing tests is the interaction between the engines and the propulsion subsystem as well as the performance of the pressurization function. The propellant for the Propulsion Qualification Model is provided by four 2000-liter tanks with 1-cm thick walls containing mixed oxides of nitrogen (MON) as oxidiser and monomethyl hydrazine (MMH) as fuel. The tanks will hold the propellant at a pressure of 25 bar with a total capacity of nine tonnes. The pressurization system features high-pressure Helium tanks to push propellant into the engines. There are 14 fuel and supply tanks in total.
The Propulsion Qualification Model (PQM) is a replica of the propulsion subsystem and is crucial for ensuring that all engines and thrusters fire safely and accurately to get the spacecraft where it needs to go. The OSM-E engine is one of 21 engines divided into three classes on the PQM: the primary AJ-10 Orbital Maneuvering System Engine (OMS-E), eight small secondary auxiliary thrusters, and 12 reaction control system (RCS) thrusters. With the RCS engines mounted on the Orion spacecraft itself there will be 33 engines in total, doubling the amount of RCS thrusters that are included in the PQM.
The European Service Module will have four solar wings each measuring 7 m in length to provide power during the mission. The solar wings were shipped from an Airbus facility in Leiden, The Netherlands by aircraft to Miami airport and on to the Kennedy Space Center. Apollo’s Service Module used hydrogen/oxygen fuel cells to provide power.
The Orion Crew Module
Above the European Service Module is the Orion Crew Module where up to four astronauts will live and work on a typical two-week flight to the Moon and back. The first mission, Artemis I, will be uncrewed and is set to launch in 2022.
Orion 2 without panels being welded in the O&C Building cleanroom. Photo: NASA/Kim Shiflett
Ground teams have loaded the Zero-G indicator – a Snoopy plushie – inside of the Orion Spacecraft. This is a part of an agreement between Peanuts and NASA. Also loaded inside of the spacecraft was a NASA mannequin, which was named “Moonikin Campos”.
The Zero-G indicator, a soft toy that can't damage or trigger any switches, is meant to show visually when the spacecraft reaches the environment of microgravity as it begins to float within the capsule. Such indicators have flown on several spacecraft’s from Russian Soyuz to SpaceX’s Crew Dragon and Boeing’s CST-100 Starliner.
Another one of the payloads that have recently been loaded into Orion in the VAB is a joint Amazon-Cisco-Lockheed Martin technology demonstrator named Callisto. This includes an Amazon Alexa virtual assistant along with other technologies. It’s a computer.
The Orion Crew Module itself is a bigger version of the Apollo Command Module with a titanium pressure vessel surrounded with life support systems, oxygen, nitrogen, water, RCS thrusters, avionics, battery packs, computers, electrical harnesses outside and inside plus a lot of panels. Everything is bolted on with 192 lateral bolts around the perimeter.
The titanium pressure vessel is welded together from seven major parts: A bottom floor bulkhead, a barrel sidewall, a three part cone with four windows and a sidehatch, a sealing top bulkhead and a docking tunnel with one or two hatches. Surrounding the tunnel is room for parachutes, drogue chutes, star cameras and docking avionics.
The parachute system for Orion is composed of 11 different parachutes which operate to slow down the spacecraft and bring it to a safe earth landing. The system's three primary parachutes are made of tough nylon and are the size of football fields.
The parachutes are packed under thousands of pounds of pressure. It takes over a week to pack just one main parachute. NASA has conducted 17 previous parachute drops at the Yuma proving ground. Each in slightly different configurations.
The Crew Module will also be integrated with its heatshield consisting of 186 blocks of Avcoat material, and the heatshield assembly has since gone through thermal testing and application of sealant in the seams between all the blocks. The sealant material is an RTV (Room Temperature Vulcanizer) and phenolic material, that have been tested in the thermal chamber at ambient pressure and it was taken to a high temperature and a low temperature brimming with test sensors searching for flaws.
The titanium pressure vessel is covered with a micrometeoroid and debris protection material made of numerous blocks of Thermal Protection System TPS similar to the 186 Avcoat blocks in the heat shield. During reentry they will protect the crew against the heat backwash from plasma shockwave.
The black backshell panels will be covered with a silicone-oxide coated aluminum kapton tape, in a similar fashion to how the heat shield is taped. It will protect them from direct sunlight in space. The picture below makes me think: ‘Batman’.
Engineers are checking and installing micrometeoroid and debris protection. Photo source
Between the Orion Crew Module and the European Service Module there is a Crew Module Adaptor CMA that is a donut shaped ring filled with extra life support systems, oxygen, nitrogen, water, avionics, battery packs, computers, electrical harnesses plus a lot of outer panels. That also is bolted on with bolts inside and around the perimeter.
The donut-shaped CMA has an inner ring wall with longerons encircling it. There are face-sheet-like walls or panels on the forward and aft faces (or the top and bottom) and then also on the outside edge. Access to the compartment divided by those walls is difficult enough to require a lift of the Orion Crew Module.
Artemis I had launched when an issue came up with one of the two Power and Data Units (PDU) in the Crew Module Adapter. The PDU was inaccessible on the Artemis I spacecraft in the fully-assembled configuration, and NASA decided to fly with the issue as-is. That design flaw is fixed on Artemis II. Access to the PDU is now through the outer wall.
Protection from Fairings or Ogives
On top of Orion for the Artemis I mission is the forward bay cover. This will protect the Orion’s crew module at speeds of more than 25,000 mph. After reentry, jettison mechanisms will generate enough thrust to push the cover away from the spacecraft and allow the three main parachutes to unfurl, stabilizing and slowing the capsule to 20 mph or less for a safe splashdown in the Pacific Ocean.
Inner Cryogenic Propulsion System ICPS with its CubeSat adapter cone, European Service Module ESM with Capsule Module Adapter CMA, Orion Crew Module OCM, three ESM cover panels and the Launch Abort System LAS ‘abort tower’ with a four panel cap. American alphabet soup. Yerk.
Artemis I will be a test of the Orion spacecraft and Space Launch System rocket as an integrated system ahead of crewed flights to the Moon. Although there will be no crew on the Artemis I, the launch abort system will collect flight data during the ascent to space and then jettison from the spacecraft.
The Orion spacecraft will be protected by four panels, or ogives, that make up the fairing assembly and protect the spacecraft from heat, air, and acoustic environments during its entry into orbit. Orion will be integrated onto the Space Launch System in the HIF.
On top of the fairing assembly will be mounted the 13,4 meter (44 foot) tall LAS Launch Abort System or Abort Tower, who will pull Orion away to safety either during launch, ascent or even into orbit. There are several abort scenarios available. link
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