Four Down, Four to Go: Artemis I Rocket Moves Closer to Hot Fire Test
The Space Launch System (SLS) rocket core stage for the Artemis I lunar mission has successfully completed its first four Green Run tests and is building on those tests for the next phase of checkout as engineers require more capability of the hardware before hot-firing the stage and its four powerful engines.
Green Run is a demanding series of eight tests and nearly 30 firsts: first loading of the propellant tanks, first flow through the propellant feed systems, first firing of all four engines, and first exposure of the stage to the vibrations and temperatures of launch.
“We are methodically bringing several complex systems to life and checking them out during the first seven tests,” explained SLS Stages Manager Julie Bassler. “Then it is show time for the eighth test when we put it all together and fire up the rocket’s core stage, just like we’ll fire it up for the Artemis I launch to the Moon.”
On Aug. 5, engineers at NASA’s Stennis Space Center near Bay St Louis, Mississippi, where the stage is loaded into the B-2 Test Stand, completed the fourth of eight planned tests of the 212-foot-tall core stage. For Test 4, engineers performed the initial functional checkout of the main propulsion system components to verify command and control operability (valve response, timing, etc.) and performed leak checks on the core stage-to-facility umbilical fluid and gas connections.
“With test gases flowing through this many parts of a complex rocket stage, we expected the test team to encounter some issues,” said Jonathan Looser, who manages the SLS core stage main propulsion system. “Historically, there’s never been a NASA human-rated launch vehicle flown without one or more full-up tests before flight, and they have all encountered first-time issues. As expected, we found a few with valves and seals and addressed them, and now we’re ready to complete the next four Green Run tests.”
The Green Run testing series formally started in January with modal testing to verify computer models and support guidance and navigation control systems. In March, the test series was interrupted by a shutdown related to COVID-19 cases in Mississippi. When testing resumed in May with appropriate safety measures in place, the team completed Test 2, activation of computers, data collection health monitoring and other “avionics” that make up the brains and nervous system of the core stage. Test 3 was a check of the fail-safe systems that shut down the stage in a contingency situation. Each test builds on the prior test and is longer than the previous one, adding new hardware activations to those already completed.
For Test 4, functional and leak checks of the stage main propulsion systems and engines lasted three weeks. Engineers were able to conduct the test with gaseous nitrogen and helium, which is more efficient than using liquid hydrogen and oxygen propellants, which are only needed for the actual hot-fire test. As these gases flowed through systems, special instrumentation monitored for any leaks or poor connections.
Next up for the Green Run team is Test 5. It will ensure the stage thrust vector control system works correctly, which includes huge components that steer the four RS-25 engines, called actuators, and provides hydraulics to the engine valves.
Test 6 simulates the launch countdown to validate the countdown timeline and sequence of events. This includes the step-by-step fueling procedures in addition to the previous test steps of powering on the avionics and simulated propellant loading and pressurization.
As one final checkout before the full firing test, Test 7 is called the “wet dress rehearsal,” meaning it builds on the simulations in Test 6 and includes fueling the rocket. After once again powering on the avionics, hydraulic systems, fail-safe systems, and other related systems that have been checked out in the prior six tests, the team will load, control, and drain more than 700,000 gallons of cryogenic, or super cold, propellants.
Only after passing these seven tests will it be time for Test 8, a full countdown and hot fire test for up to eight minutes. During the test, all four RS-25 engines will be firing at a full, combined 1.6 million pounds of thrust just as they will on the launch pad. Test 8 will be the final checkout to verify the stage is ready for launch. Afterward, engineers will prepare the stage for its trip to Kennedy Space Center in Florida.
“We want to find any issues here on the ground at Stennis, where we’ve added hundreds of special ground test sensors to the stage for Green Run,” said Ryan McKibben, one of the Stennis Green Run test conductors. “We have great access to the stage on the B-2 Test Stand and have engineers and technicians on hand who are familiar with this stage.”
By the time all eight Green Run tests are complete, Boeing, the prime contractor for the core stage, estimates it will collect 75-100 terabytes of data, not including voice and video data collected. And that’s a lot of homework considering that all the data in the Library of Congress amounts to just 15 terabytes.
NASA is working to land the first woman and next man on the Moon by 2024. SLS and Orion, along with the human landing system and the Gateway in orbit around 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.
Update: 19.00 MESZ
SN6 begins test campaign as future Starships hatch plans for SpaceX’s next leap
Following the successful test of Starship SN5 during its 150-meter hop just a week ago, the next Starship (SN6) is preparing to repeat the test in the coming days. With a potential tag-team – or hop-team – role for SN5 and SN6, a roadmap is starting to form ahead of the more ambitious tests that will involve Starships SN8 and SN9 – both of which are already under various stages of construction at SpaceX Boca Chica.
With the incredible build and test cadence continuing at SpaceX’s facility in South Texas, a “hot-swap” in the Mid Bay was required after SN5 rolled back from the launch site, following what was the first successful hop of a Starship test vehicle.
With SN6 already assembled in the Mid Bay and waiting patiently for her turn at testing, the two prototypes swapped places, allowing SN5 to take SN6’s slot in the bay, while the latter rolled to the vacated test mount at the launch site.
Starship SN6 – a near-twin to SN5 – is currently pushing through a pre-hop test sequence that includes proof-testing ahead of a Static Fire test, laying the path toward its own 150-meter hop.
SpaceX CEO and Chief Designer Elon Musk recently noted there will be numerous hops to refine the launch sequence,providing useful data ahead of the next major milestones that will see a future Starship launch as high as 20 kilometers.
This could result in SN5 and SN6 tag-teaming over the coming weeks, each replaying their 150-meter hops under the power of a single Raptor engine.
First, SN6 is required to pass numerous tests ahead of the hop, including proof/cryo testing, milestones that occurred on Sunday with the loading of LN2 (Liquid Nitrogen).
Providing all goes well with those tests, the hydraulic rams – placed in the launch mount to impart forces on the aft of the vehicle during pressurization tests – will be removed and a Raptor engine (likely SN29) will be installed on SN6. This will allow the Static Fire test to take place, which will provide a green light to proceed toward the 150-meter hop.
Following the test, SN6 will either be placed back on the launch mount for a second hop or rolled back to the Mid Bay to tap SN5 back into the game for her second hop.
Likely to take place during the hop series, a Test Tank, called SN7.1, will make a trip to the launch site for a test of its own. While both SN5 and SN6 are made from 301 Stainless Steel, SN7.1 is made from 304L (or at least a variant of this alloy). 304L is what all near-term future Starships will be made from before SpaceX employs its under-development proprietary alloy.
Data from SN7.1 will be fed into the data set that will guide pressure allowances on Starship SN8, which has already begun final assembly inside the Mid Bay next to its new neighbor, SN5.
With SN8 also made from 304L, the vehicle is set to provide the next leap forward – or upwards – for SpaceX’s Starship Launch System (SLS – not the orange one).
SN8 is expected to gain the nosecone, made from a five ring barrel section and the fairing dome, along with aerodynamic control surfaces, pointing towards a much greater leap compared to the tests with her younger sisters. While such a completed nosecone has been observed inside the Windbreak, it has not been confirmed that this is the nosecone section that will be installed on SN8.
Numerous nosecones, to the point of it becoming amusing, can be seen waiting their turn for potentially becoming flight-worthy. Ultimately, the nosecones which include a header tank are believed to be the most likely to fly.
SN8’s aft section is also expected to gain fins, with aft fins already seen on site, along with additional hardware recently arriving via new deliveries over the past few days. Most notably, SN8 will fly with three Raptor engines.
While SN8 presses onwards to become the first full-stack Starship, SN9 has been seen in public for the first time, with a Common Dome section rolled out of one of the Big Tents at the Production Site.
Although it is early days for SN9, this sighting intimates that there are likely parts – namely bulkheads – for several other Starships under construction inside the Big Tents, given the lead time and Elon Musk’s note that this is one of the hardest parts of Starship to construct.
Moving past Starship, preparations for the huge Super Heavy booster are in full swing at both the Production Site and the Launch Site.
Continuing to rise above Level 3, the new High Bay is being built at pace. Construction of the High Bay only began a month ago and has since risen to become the tallest building at SpaceX Boca Chica.
This 81-meter tall facility will host the stacking of Super Heavy sections before the vehicle is then rolled to the launch site for mating with the Starship vehicle.
Notably, work on the Super Heavy launch site has picked up considerably over recent days.
Located next door to the Starship test site that currently hosts SN6 and permanent resident Starhopper, the Super Heavy pad was a placeholder area of SpaceX Boca Chica, with only its land area laid out by Earthmovers via ground preparations. However, it came back to life via numerous borehole drilling operations, as foundations for what is envisioned to be a huge launch tower were laid.
In recent days, the shape of foundations for a new structure has been observed, although it is not clear if this will become the launch tower structure, a water tower for Super Heavy’s Sound Suppression System – or something completely different.
Now classed as the “Orbital Launch Pad”, rebar cages have been placed around the immediate construction area, akin to how the Tripod Test Stand at SpaceX’s McGregor test site was constructed (albeit by original tenants, Beal Aerospace).
SpaceX’s official renderings of Super Heavy launching from Boca Chica place focus mostly on a HIF (Horizontal Integration Facility) and the huge service tower. However, such footage, however official, should always be deemed notional, not least when portraying an ever-refining launch system.
What can be confidently assumed is SpaceX is preparing the facility groundwork for the first assembly and testing of Super Heavy by 2021.
Test programs and new vehicles will always stretch schedules. However, there remains the distinct possibility SpaceX could launch their first Super Heavy rocket before the Space Launch System (SLS – the orange one) is due to conduct her maiden launch at the end of next year.
Backbone of a spacecraft
This structure is the frame and base for the European Service Module, part of NASA’s Orion spacecraft that will return humans to the Moon.
Built in Turin, Italy, at Thales Alenia Space, this is the third such structure to roll out of production. However, this one is extra special, as it will fly the first woman and next man to land on the Moon and return on the Artemis III mission by 2024.
The structure is nearly complete and acts as a backbone to the Orion spacecraft, providing rigidity during launch.
Much like a car chassis, this structure forms the basis for all further assembly of the spacecraft, including 11 km of wiring, 33 engines, four tanks to hold over 8000 litres of fuel, enough water and air to keep four astronauts alive for 20 days in space and the seven-metre ‘x-wing’ solar arrays that provide enough electricity to power two households.
Orion’s backbone will travel to the Airbus integration hall in Bremen, Germany, at the end of the month to integrate all the elements listed above and more. This third European Service Module will join the second in the series that is already in Bremen, and nearing completion, to be sent to NASA’s Kennedy Space Center next year.
The first service module is already finished and will be integrated with the Crew Module and rocket adapters to sit atop the Space Launch Systems rocket. The first completed Orion craft is scheduled for a launch and fly-by around the Moon, without astronauts, next year on the first Artemis mission.
The countdown to the Moon starts in Europe with 16 companies in ten countries supplying the components that make up humankind’s next generation spacecraft for exploration.