The Space Launch System Runs Into More Problems During Tests
Artemis has the goal of not only returning humans to the surface of the Moon but setting up a more permanent human presence. This goal is very ambitious and requires a massive amount of infrastructure and different pieces of the mission. The Space Launch System is one of the most powerful rockets in the world meant to transport both humans and cargo to and from the Moon.
Over the past few months, this launch vehicle has been going through testing apart of the wet dress rehearsal. Unfortunately for the agency, it has not gone very well and both the rocket and ground systems have experienced multiple issues along the way. This has continued to delay the test and ultimately the Artemis program.
With the first launch of SLS intended to happen this summer, these continued delays and problems are not a good sign for the future of Artemis. This will no doubt have an impact on returning humans to the Moon. Here I will go more in-depth into the recent issues that SLS has gone through with testing over the past few days and more.
Recent Updates
After initial attempts of the wet dress rehearsal for SLS back in April, over the past few days the launch vehicle has returned to the pad and tried again. Unfortunately, following a similar theme over the past few months, it ran into more problems. This began on June 18th where at approximately 5 p.m. EDT, the launch team arrived at their stations inside the Launch Control Center at NASA’s Kennedy Space Center in Florida to begin the wet dress rehearsal test for NASA’s Artemis I mission. The countdown began 30 minutes later at 5:30 p.m. or L-45 hours, 10 minutes before the initial target T-0 of 2:40 p.m. on Monday, June 20. Overnight, teams powered up the Orion spacecraft and the Space Launch System core stage and prepared the rocket’s four RS-25 engines, which will not be lit during the test. From here, the launch team made its way through countdown operations and wet dress rehearsal activities. Teams also configured several systems on the ground, rocket, and spacecraft and performed activities to prepare umbilicals that connect the rocket and spacecraft to the mobile launcher and are used to provide power, communications, coolant, and propellant.
The next day on June 20th, the mission management team chair has given a “go” to proceed with tanking the Space Launch System rocket for the Artemis I wet dress rehearsal test. Tanking begins with chilling down the liquid oxygen lines for the core stage. In sequential fashion, liquid oxygen and liquid hydrogen will flow into the rocket’s core stage and interim cryogenic propulsion stage tanks and be topped off and replenished as some of the cryogenic propellant boils off. Next, the launch control team began filling the Space Launch System’s interim cryogenic propulsion stage (ICPS) with liquid hydrogen (LH2) followed by liquid oxygen (LOX) loading. The core stage LH2 and LOX tanks, meanwhile, were being replenished as some of the supercool propellants boils off, meaning the propellant tank will be full through the rest of the countdown. However, all of this came to an end late on June 20th when another problem arose. The Artemis I wet dress rehearsal ended at 7:37 p.m. EDT at T-29 seconds in the countdown. The test marked the first time the team fully loaded all the Space Launch System rocket’s propellant tanks and proceeded into the terminal launch countdown, when many critical activities occur in rapid succession.
During propellant loading operations earlier in the day, launch controllers encountered a hydrogen leak in the quick disconnect that attaches an umbilical from the tail service mast on the mobile launcher to the rocket’s core stage. The team attempted to fix the leak by warming the quick disconnect and then chilling it back down to realign a seal, but their efforts did not fix the issue. In this case, two tail service mast umbilicals, or TSMUs, connect from the zero-level deck on the mobile launcher to the SLS rocket core stage aft section. The TSMUs are about 33 feet tall. They will provide liquid oxygen and liquidhydrogen fluid lines and electrical cable connections to the SLS core stage engine section to support propellant handling during prelaunch operations. The TSMUs will tilt back before launch to ensure a safe and reliable disconnect and retract of all umbilical hardware away from the rocket during lift-off. These same umbilicals have been having problems since the beginning of SLS wet dress rehearsal testing.
In terms of the test, NASA points out that after the leak was detected, launch controllers developed a plan to mask data associated with the leak that would trigger a hold by the ground launch sequencer, or launch computer, in a real launch day scenario, to allow them to get as far into the countdown as possible. The time required to develop the plan required extended hold time during the countdown activities, but they were able to resume with the final 10 minutes of the countdown, called terminal count. During the terminal count, the teams performed several critical operations that must be accomplished for launch including switching control from the ground launch sequencer to the automated launch sequencer controlled by the rocket’s flight software, an important step that the team wanted to accomplish. NASA gave updates on Twitter the day of mentioning, “UPDATE: Liquid oxygen upper stage is now in stop flow. The team has discovered a hydrogen leak at a quick disconnect for the core stage and are currently working to understand the situation.” Despite the problem encountered, by the end of the test the agency tweeted again this time saying, “The team has wrapped wet dress rehearsal for the day. Artemis I Launch Director Charlie Blackwell-Thompson said this was a “great day for our team” and she was “really proud of the team and all they’ve done to get us here.”
SLS & Artemis
Now that we know more about some of the recent recurring issues the rocket has run into, we can take a closer look at the wet dress rehearsal and the launch of Artemis 1. The wet dress rehearsal is considered the final test of the Space Launch System rocket, Orion spacecraft, and Exploration Ground Systems before the Artemis I launch at Launch Pad 39B. The rehearsal will run the Artemis I launch team through operations to load propellant into the rocket’s tanks, conduct a full launch countdown, demonstrate the ability to recycle the countdown clock, and also drain the tanks to give them an opportunity to practice the timelines and procedures they will use for launch. During what NASA points out as an approximately two-day test, teams will start by activating the facilities needed for launch and formally beginning the countdown sequence. Teams will staff the Launch Control Center at Kennedy and connect with staff in the Mission Control Center at NASA’s Johnson Space Center in Houston, the Space Force Eastern Range, and the SLS Engineering Support Center at the agency’s Marshall Space Flight Center in Huntsville, Alabama. Launch controllers will power on different rocket and spacecraft systems, along with ground support equipment.
From here, the agency will then load more than 700,000 gallons of cryogenic, or super cold, propellants including liquid hydrogen and liquid oxygen into the rocket at the launch pad on the mobile launcher according to the detailed timeline they will use on the actual launch day. They will practice every phase of the countdown, including weather briefings, pre-planned holds in the countdown, conditioning and replenishing the propellants as needed, and validation checks. During the wet dress rehearsal, once launch controllers reach the point just before the rocket’s RS-25 engines will ignite on launch day, they will recycle back to the T-10 minute point, and then resume the countdown once more after a hold. The team will then deliberately halt the countdown at about 10 seconds before the simulated liftoff to demonstrate stopping a launch and draining the propellants from the rocket. Sometimes called a “scrub,” launch controllers may decide not to proceed with launch if a technical or weather issue arises during or prior to the countdown, so demonstrating the ability to remove propellants will ensure teams are prepared for various launch day scenarios. As I partially mentioned prior, these tests began back in April. However, it became clear very soon into the tests that this process would likely take longer than expected. After multiple problems arose the SLS was returned to the VAB for repairs and recently returned to the pad. Now once again it has run into more problems.
Conclusion
For months now the Space Launch System has been trying to complete its wet dress rehearsal in preparation for the first launch of the rocket part of Artemis 1. After receiving repairs it seems the agency is back where it started as more leaks become apparent in recent testing. In order to avoid even more delays for SLS and overall Artemis missions, they need to finish the wet dress rehearsal and successfully launch SLS. We will have to wait and see how it progresses and the impact it has on the space industry.