SLS engineering tests to accompany pre-launch checkouts for Artemis 1

The launch campaign for NASA’s Artemis 1 test flight will be punctuated by critical and… The post SLS engineering tests to accompany pre-launch checkouts for Artemis 1 appeared first on

SLS engineering tests to accompany pre-launch checkouts for Artemis 1

The launch campaign for NASA’s Artemis 1 test flight will be punctuated by critical and unique tests to support both pre-launch checkouts of this first-flight vehicle and long-term design objectives. Launch preparations are progressing towards the first power-up of the Artemis 1 Space Launch System (SLS) rocket, which will allow the Exploration Ground Systems (EGS) launch team to begin digital diagnostics.

The Integrated Test and Checkout (ITCO) of the flight and ground systems will include special engineering tests for the Orion and SLS Programs. Up to this point, mathematical models were used to analyze and predict how the different systems would work when assembled on the launch platform; over the next few months, some of the tests will help calibrate those analytical models while others verify that the vehicle is ready to launch for the first time.

First-flight engineering tests included in pre-launch checkouts

There is more to launch preparations than stacking the pieces and bolting them together. The Artemis 1 flight vehicle is a group of interconnected machines that each controls different phases of the launch and mission.

The Artemis 1 vehicle includes three independent flight control systems. The NASA SLS flight system being flown for the first time will be in control from liftoff to cutoff/suborbital insertion by the Core Stage. At that point, control is handed off to the United Launch Alliance flight system on the Interim Cryogenic Propulsion System (ICPS) for flight through the trans-lunar injection burn (TLI). After TLI, Orion separates from the ICPS on its way to the Moon and the Orion spacecraft’s flight control system then performs the Artemis 1 mission, navigating in and out of lunar orbit and back to Earth.

All three flight systems need to be aware of each other, and up until shortly before ignition they are responding to directions from the ground launch command and control system. Before the crawler-transporter takes the Mobile Launcher with the vehicle stacked on it out to the launch pad, all those interconnections and their thousands of constituent signals need to be validated during integrated checkouts while parked in the Vehicle Assembly Building (VAB).

In addition to the standard pre-launch checkouts that every Orion/SLS vehicle will go through in the VAB, a number of engineering tests will be carried out during the Artemis 1 campaign as part of the overall development of the spacecraft, launch vehicle, and ground support systems.

Credit: NASA.

(Photo Caption: The ICPS in-space stage for Artemis 1 is suspended on one of the VAB cranes in position while being mated to the partially-assembled SLS stack on July 6. Along with preparatory checkouts, the SLS vehicle will be put through a series of engineering tests prior to the Artemis 1 launch.)

“[Testing is] a good truth model for us,” Dr. John Blevins, NASA’s Chief Engineer for the SLS Program, said in a July 12 interview. “As we stacked and put the boosters together, and before we put the Core Stage on, we did this test that we call the booster pull test. We put [a] load on the booster, and we really measured the stiffness, if you will, the compliance of the joint on the bottom of the booster where it is on the vehicle posts. So ITCO has already started.”

One of the more prominent tests on the Artemis 1 launch processing schedule is the Integrated Modal Test, which is the latest in a series of modal tests that have been performed on different parts of the flight and ground structures. During the Green Run design verification campaign of the Core Stage at the Stennis Space Center, a modal test was performed on the standalone stage while it was suspended on a crane at the test stand.

“We did do a ping test when it was on the crane, and then we also did three shakers at Stennis Space Center to get those modes if you will, the displacements through the structure as we excite the structure,” Blevins said. “We basically suspended the vehicle with shakers on it, and we did that modal test and were able to get the information that really went to finalize the finite element model.”

“The Integrated Modal Test is one of the more exciting ones,” Blevins observed. “We’re going to do that with the integrated vehicle; that modal test has got six shakers to do that. We’ve already done some modal testing down at KSC. We took the crawler transporter system and did a modal test on that. We did it with and without the Mobile Launcher. And now we’ll have the vehicle on the Mobile Launcher, so we’ve got this modal test with the six shakers to do that in place.”

As with the test on the Core Stage by itself at Stennis, the integrated SLS vehicle with a mass and center of gravity Orion simulator on top is still connected to the Mobile Launcher. The shakers that vibrate the structure are not just vibrating the vehicle structures, but also the ground support equipment they are attached to.

Additional testing and data was performed and gathered on the ground equipment at Stennis and KSC by themselves.

Blevins noted that there are other tests that will measure the coupled structural dynamics between the vehicle, Mobile Launcher, and crawler-transporter. A dynamic rollout test is planned when the Artemis 1 vehicle rolls out to the launch pad for its last planned series of tests — and then on its way back from the pad to the VAB for final launch closeouts.

There is the possibility of a braking test during rollout. “We do have a test of opportunity as we roll out the vehicle where we just brake as we’re rolling out at all of 0.8 miles an hour speed,” Blevins said. “[We would] make a hard braking, and you’ll see the response of the vehicle. And that’s another integrated type of test.”

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  • “We’re going to monitor the dynamic response of the vehicle as we have it on [the crawler]. There’s not just that braking test or that dynamic rollout test, but also that full [rollout] event. And that’s really part of ITCO as well because that feeds back the fatigue spectra that we would expect on different rollouts and rollbacks.”

    Before the fully connected vehicle rolls out on the Mobile Launcher to the pad, a series of Program Specific Engineering Tests (PSET) will be carried out inside the VAB.

    “Some of the tests are software tests,” Blevins related. “Some of them we would call sensor-to-effector testing.” One of those software tests is an “end-to-end polarity test” that demonstrates that gimbaling commands to the SLS Solid Rocket Booster (SRB) nozzles and Core Stage engines from the flight software guidance system are properly translated from vehicle motion sensors.

    “We actually point to a place in orbit and then we monitor the change in the nozzles. And we make this a really complex location so I can see [gimbaling] in all axes, but we’ll monitor the vehicle just changing from where it’s sitting on the Earth to how that point in space changes during the day,” Blevins explained. “We’ll set up video and we’ll take really low speed video to see the integrated motion of the nozzles. And that’s really like a flight controls test, although certainly it works through the software.”

    “We also have some acoustic tests coming up here shortly where we make some noise and we measure [the] attenuation. It’s one of the few tests that aren’t what I would call critical to making sure we’re successful on Artemis 1 or 2, but it is a way we can learn about the attenuation of noise through that structure and inform us how we can decrease mass or really inform some of our payloads as we go forward.”

    “If we have [payloads] that are going to be in different volumes, they will be able to have a better, more accurate measure of the acoustics that would be placed on them,” he added.

    Blevins also elaborated on some other SLS functional and environmental testing that will be performed during launch campaign testing. “There’s RINU (Redundant Inertial Navigation Unit) initialization,” he said. “We spin up the CAPUs (Core Auxiliary Power Unit) in their environment. We did that obviously with Green Run, and they were quite important [for that].”

    “There’s a comm (communications) test that’s through-and-through the system. So we send signals. Some of those pass certain information through the SLS systems between the Core Stage to Orion, and so that’s got to go through those parts. There’s ordnance tests with our Flight Termination System that are required.”

    “There’s also a time correlation test that we’re going to do where we ping and we make sure the timing throughout the system/rocket doesn’t have any excessive latency,” Blevins continued. “You’ve got multiple flight instrumentation boxes that are hooked up to different data acquisition systems, so we can really calibrate any of that lag out if we find any in this time correlation test. But that’s a particularly good one.”

    “Just to mention a few others, one is an RF test, a radio frequency test, where we’re just making sure that the local cell towers don’t block our telemetry systems and things like that. Not all of these are standard; this is a little bit more than a normal rocket because it’s a first launch of a rocket. We won’t do a modal test again [after Artemis 1]; we won’t instrument some of the things as much, but all of those are really important tests,” Blevins added.

    The Orion program will also be running specific engineering tests on their spacecraft during ITCO.

    Credit: NASA.

    (Photo Caption: A finite element style rendering of the vehicle configuration that will be used for the Integrated Modal Test (IMT) to be conducted on the SLS and Orion simulator while they are sitting on the Mobile Launcher. A structural test article of the Orion Stage Adapter and a Mass Simulator for Orion will substitute for the flight spacecraft elements during ping and shaker testing.)

    The integrated operations team of EGS and prime launch processing contractor Jacobs is working to prepare the SLS part of the Artemis 1 stack for power up by their Spaceport Command and Control System (SCCS) to begin some of the bigger testing and checkouts in the VAB.

    The first powered ITCO test is called the Interface Verification Test (IVT). The connections between all of the SLS flight hardware and the Mobile Launcher will be checked out in the IVT, which is currently projected for mid-August.

    “We’ll verify health and status of the vehicle, that everything is functioning correctly, as intended per the build,” Danny Zeno, Senior NASA Test Director for EGS, said in a recent interview. “We want to make sure electrical interfaces are correctly mated. We’ll go through a series of vehicle leak checks to make sure all of those are good from a ground perspective. And that data is essentially looking good as a readiness check to make sure all the systems are looking good and performing nominally.”

    After the IVT is completed, internal access platforms will be removed from the equipment sections of the Core Stage and other SLS elements will be closed out as if for launch in preparation for the next two tests. The first of those, the Umbilical Release and Retract Test (URRT), will verify the Mobile Launcher’s swing-arm release system, which must safely detach the ground umbilical connections from the vehicle at T0 and quickly swing, or drop as the case may be, the various arms away.

    That will be followed by the Integrated Modal Test, where the shakers described by Blevins will excite the vehicle as it is attached to the Mobile Launcher through just the eight Vehicle Support Posts on the SRB aft skirts.

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    Nauka science module launches to ISS

    Good things come to those (modules) that wait.  On July 21, at 14:58:25 UTC (10:58:25… The post Nauka science module launches to ISS appeared first on

    Nauka science module launches to ISS

    Good things come to those (modules) that wait.  On July 21, at 14:58:25 UTC (10:58:25 EDT), a Proton-M rocket launched from the Baikonur Cosmodrome to take the first Russian ISS module in 11 years to orbit.  The moment marked a major milestone for Roscosmos, which was originally slated to launch the module in 2007.

    After launch and orbit insertion, the module, MLM-U Nauka, is now performing an eight day phase to the Station for an automated docking on July 29 to the nadir docking port of the Zvezda service module, a port currently occupied by the Pirs module.

    Nauka – the “long suffering” module

    Upon arrival, Nauka will become the third largest module of

    The main task for the Nauka module will be to conduct scientific experiments.  The pressurized compartment of the module contains 21 universal working places (URM), including four locations with sliding shelves, a glove box, a frame with an automatic rotating vibration-proof platform, and a porthole with a diameter of 426 mm for visual and instrumental observations.

    Equipment to allow easier replacement of old experiments with new ones is also incorporated into Nauka’s internal design and is based on lessons learned from the early years of the ISS program. 

    An additional 16 URMs are located on the outer surfaces of the module, which also has an airlock chamber and a European manipulator robotic arm, which will allow operations with experiments in the vacuum of space without performing EVAs.

    The full name of the new module, MLM-U “Nauka” (which means “science”), stands for “Multifunctional laboratory module Nauka, improved.”  However, it is also somewhat lovingly referred to as the “long-suffering module” due to its numerous uses and launch date changes.

    Initially, Nauka was built as a backup for FGB Zarya, the first module of the ISS.  Construction started in 1995, with a design based on the hull of the Soviet cargo ship TKS, itself a part of the Almaz military program which included orbital stations, a supply cargo ship, and crewed ships with reusable descent modules. 

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  • Nauka is in fact the last surviving, active part of the Almaz program, excluding the hulls and ships which were sold to the Excalibur-Almaz company and to museums for exhibition.  Nauka’s original use as a back up Zarya stemmed from the critical nature of the Zarya module to the overall ISS design; given a launch failure would have set the ISS program back years, Nauka was built as a “quick replacement” to Zarya in case the original module was lost in a launch failure.

    Zarya successfully launched on a Proton-K rocket from the Baikonur Cosmodrome on November 20, 1998 and was grabbed by Shuttle Endeavour’s robotic arm, or Canadarm, on December 6 and manually docked to the Unity module.  At this point, Nauka, or FGB-2, as it was called originally, was already 80% complete and now no longer needed for its primary back-up role. 

    The same year as Zarya’s launch, the Khrunichev Center proposed creating a scientific module for the U.S. segment of the Station based on FGB-2 to replace Destiny, delivery of which from Boeing was running late.  While an agreement of intent was signed, Destiny was completed and successfully sent into orbit in 2001 while FGB-2 remained on Earth. 

    Not wanting to discard a nearly complete module, in 2004, Roscosmos decided to create a laboratory module based on it for the Russian segment of the ISS.  To do this, FGB-2 had to be completely reequipped — all systems that would have been needed as a Zarya back-up but that were no longer necessary for its use as a science module were removed to make room for scientific equipment.  

    Nauka undergoing checkouts and outfitting in 2020. (Credit: Katya Pavlushchenko)

    At the same time, Roscosmos partnered with the European Space Agency to install an 11 meter European robotic arm, the ERA, on the new module.  The European arm will be able to help cosmonauts access locations on the Station during spacewalks and remove and install equipment placed on the outer surface of the ISS. 

    The re-equipment process for FGB-2 was anticipated to take three years, resulting in a 2007 launch.  The module was formally renamed at this time to MLM Nauka.  However, as is often the case in the space industry, the proposed deadlines turned out to be too optimistic.  

    By 2006, two years into the refit, the launch was postponed to 2009 and then again to 2012.  In December 2012, with another launch delay added, the module was finally moved from the Khrunichev Center, where it was built, to RSC Energia for testing. 

    Here, a problem was discovered.

    In June 2013, RSC Energia specialists reported a large number of defects had been found in the module.  In particular, metal shavings were discovered contaminating fuel lines, which caused the launch date to be postponed to 2014 and the module itself was returned to the Khrunichev Center for pipeline cleaning.

    The procedures and bureaucracy took several months, including a slight rename to the module.  According to documents, since the module was already manufactured and fully paid for, it was legally necessary to call its repair an “upgrade.”  From that moment on, the letter “U,” which means “improved,” appeared in the name of the module. 

    Nauka, just before encapsulation for launch. (Credit: Roscosmos)

    At the end of 2013, the module was finally transported back to the Khrunichev Center and a new launch date was set for 2016.  However, checkout of all systems took three years, due to lack of funding, necessitating another slip to the launch date.

    In April 2017, specialists at the Khrunichev Center announced that the same metal shavings previously found in the fuel pipelines were found in the propellant tanks of the module as well.  This statement, combined with another long-term postponement of the launch, led many experts to question if Nauka would ever fly to orbit. 

    However, the new issue with the tank posed a problem: the propellant tanks for Nauka were made in the 1990s on equipment that no longer existed in 2017 at a factory that was already demolished using technology that now remained only as drawings.

    The module’s bellow refillable propellant tanks are 400-liter tanks installed on the outer surface of the housing of the module. These tanks are fueled with unsymmetrical dimethylhydrazine and dinitrogen tetroxide.  From them, fuel travels to the orbital maneuvering engines, which are necessary for orbit correction and rendezvous maneuvers. 

    Officials were concerned that the metal shavings could travel into the engines and contaminate them, preventing the module from being able to dock with the ISS and burning up in the dense layers of the atmosphere instead.

    At first, engineers wanted to flush the tanks under pressure, but this procedure was not successful.  After that, cutting, washing and re-welding of the tanks was tested on a mockup of the module, but it was found that after such a procedure it would not be possible to restore the tanks to their proper condition and strength.  

    An internal cut-way showing the layout of Nauka. (Credit: Roscosmos)

    Additional ideas were considered to:

    • replace the existing propellant tanks with ones made for the Science and Power Module (NEM).  This was rejected because the tanks of NEM have a different diameter and it would require a redesign of the module and the fairing for Nauka.
    • replace the propellant tanks of Nauka with the ones from an upper stage Fregat.  A series of spherical Fregat tanks would have been fitted into the current dimensions of the module, but they would not be refuelable and would have demanded significant improvement of the whole propellant system of the module.
    • send Nauka to orbit with its regular propellant tanks as they were.

    The possibility of manufacturing new propellant tanks using old technology was not considered due to the lack of equipment for their production.  As a result, it was decided that Nauka would fly with its regular propellant tanks, which would now be used only once. 

    At the same time, numerous experts in the space industry noted that contamination with metal shavings of 100 microns in size could not affect the engines of the module and that given similar designs it is possible a similar contamination existed in the tanks of Zarya and in the tanks of the Mir station modules but that the older quality control methods couldn’t detect the shavings.  

    Some experts also noted that metal shavings are a consequence of the very design of the tanks and are formed with every movement of the bellows; therefore simply building new ones would not solve the issue.

    Nevertheless, over the intervening three years, all the original pipelines and valves were dismantled and replaced with new ones.  At the beginning of 2020, specialists began a new testing campaign of the Nauka module, and a new launch date was set: May 2021.  

    The tests lasted slightly longer than expected, and the new official launch date was set for July 15, 2021.  But the adventures of the “multi-suffering” module didn’t end there. 

    In early July 2021, when the fairing had already been installed over the module for launch, Nauka was suddenly returned to the assembly building.  According to the official version, shortcomings were found, but no further information was stated at first.

    The RussianSpaceWeb portal published a report stating that final assembly workers forgot to install the thermal vacuum insulation covers on the star tracker and infrared sensors.  This issue was missed by Roscosmos and apparently only spotted by spaceflight enthusiasts from images posted by the Russian space agency.  The module was returned to the assembly building, and the launch date was postponed again to July 21, 2021.


    At 20,350 kg mass, Nauka was near the upper limit of what the Proton-M rocket could deliver to low Earth orbit (LEO). 

    With a lift capability of 23,000 kg to LEO, the Proton-M lifted off from Site No. 200/39 at the Baikonur Cosmodrome, pitching onto an azimuth, or compass heading, to achieve a 51.6 degree inclination orbit.

    The Proton-M for this mission flew in its three stage-to-orbit configuration, with all stages burning the highly toxic dinitrogen tetroxide and unsymmetrical dimethylhydrazine mixture.

    The first stage employed six RD-275M engines arranged around the circumference of the first stage tanks.  A hot-stage event, where the second stage ignites while the first stage is still attached and firing, handed off between the two lower stages.

    The mighty power of the Proton-M as it lifts off with Nauka. (Credit: Roscosmos)

    Payload fairing separation occurred at an altitude of 138 km just after third stage separation and ignition 330 seconds into the flight.

    The third stage, 8S812, then completed the launch sequence, placing Nauka into a 190 x 350.1 km orbit in the plane of the International Space Station after a 580 second ascent

    Once in orbit, Nauka deployed its solar panels and began eight days of system checkouts and rendezvous burns to gradually raise its orbit up to the 415 km altitude of the Station.  If all goes to plan, Nauka will dock itself to the ISS — under the watchful eye of Mission Control, Moscow, and the Russian crew onboard the Station — on Thursday, July 29.

    However, Nauka’s destination on the Station is currently occupied by the Pirs docking compartment — which itself has the Progress MS-16 vehicle docked to it.  

    If Nauka is declared “go” for arrival to the ISS after a successful launch and initial orbital checkout over July 21 and 22, the Progress MS-16 vehicle will remove the Pirs module from the Zvezda nadir docking port on Friday, July 23 at 13:17 UTC / 09:17 EDT to make room for Nauka.

    Pirs will not be removed from the Station until Nauka receives post-launch clearance to proceed with its mission as Pirs is a critical docking port and module for the ISS until Nauka is ready to take its place.  Nevertheless, Pirs will not be brought back to the ISS but will instead remain gripped by Progress MS-16 as the craft deorbits for a destructive reentry into Earth’s atmosphere — making Pirs the first ISS module to be decommissioned and removed from the outpost.  

    Six days after Pirs’ permanent departure, Nauka is scheduled to perform the final rendezvous sequence with the ISS and dock itself to the Zvezda service module’s nadir location on July 29 at 13:25 UTC / 09:25 EDT.

    (Lead image: Proton-M lifts off from Baikonur Site 200/39 with Nauka. Credit: Roscosmos)

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