NASA’s Artemis 1 lunar mission completed a crucial phase before the flight today (June 20), completing a two-day set of tests known as the wet rehearsal.
These tests included refueling Artemis 1’s huge space launch vehicle (SLS) and performing a simulated countdown that guided NASA’s vehicle and Orion capsule through most of the progress it would have endured on the day of launch before the engine was started. . The simulated countdown ended at 19:37 EDT (2337 GMT), ending the wet dress.
Not everything went perfectly smoothly. The Artemis 1 team noticed a hydrogen leak during charging today, and they deliberately “masked” data related to the problem to allow the countdown to continue. (During the actual countdown, such data would raise red flags, NASA officials said.) This change meant that the countdown was stopped at T-29 seconds before “take-off” instead of T-9 seconds, as originally planned. .
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But this hiccup did not dampen the enthusiasm of the Artemis 1 team.
“This is a great day for our team,” said Charlie Blackwell-Thompson, Artemis’ director of launch at NASA’s Kennedy Space Center’s (KSC) ground-based research program, during a wet dress webcast just after she finished. “We are really proud to work through charging operations and work through the number of terminals.”
KSC ground crews are likely to spend the next few days preparing the Artemis 1 stack and mobile launch platform (MLP) for transport from launch site 39B to the Vehicle Assembly Building (VAB), where technicians will analyze the results of a series of tests.
The wet dress was the last important stage that Artemis 1 had to complete before launch. During the actual mission, the SLS rocket will launch an unmanned Orion on an approximately one-month voyage to the moon and back. Artemis 1 will be the first in a series of expeditions to the moon that NASA hopes will lay the groundwork for a permanent human presence on the lunar surface – one of the agency’s main goals Artemis program.
Artemis 1 will be the first flight to SLS, realizing more than a decade of research, development and production to advance NASA’s plans to study humans beyond low Earth orbit (LEO). If Artemis 1 goes well, NASA plans to fly with astronauts aboard Artemis 2 and Artemis 3, the latest mission will suppress the astronauts The moon after about four years.
Agency officials have repeatedly expressed optimism about the launch of Artemis 1 in late August, but these hopes have always depended on a smooth wet dress rehearsal. Now this startup window looks much closer to reality.
Procedures for missile and MLP systems at 39B began on Saturday (June 18th) with a call to ground crew stations at 17:00 EDT (2100 GMT). This marked the beginning of the countdown clock to the simulated start time of 14:40 EDT (1840 GMT) today, which was later shifted back to 16:38 EDT (2038 GMT).
True to its name, one of the first major protocols for rehearsing the SLS wet dress was filling the water tanks for the pad’s damping infrastructure. The system dumps nearly half a million gallons (1.9 million liters) of water on the launch site and fire trenches during actual takeoff and works to absorb the acoustic energy emitted by the engine’s ignition.
Then in the process came the launch of the vehicle stage. Operators began this on Saturday night, first turning on Orion systems. The SLS core was powered the next, early Sunday morning (June 19th), followed by a series of inspections of the system to verify connections between the spacecraft, ground infrastructure and boards in mission control.
With active systems of the first stage of the rocket, the final preparation for the four of the vehicle RS-25 engines completed their own set of inspections and tests, which ended on Sunday morning.
NASA officials met on Sunday to assess the progress of the rehearsal and receive a weather briefing from meteorologists with the United States Cosmic force Space Launch Delta 45, which predicts favorable weather conditions for today’s tanking procedures. In an official blog post, NASA said ground crews on Sunday afternoon “are launching a rocket launch to ensure the space launch system is ready for upcoming refueling operations.”
Burning the midnight oil, so to speak, NASA teams turned on the power to the upper stage of the SLS, known as the intermediate cryogenic drive stage (ICPS), just before 2:00 am EDT (0600 GMT) today. By 2:40 a.m. (6:40 a.m. GMT), all non-essential personnel had been removed from the launch pad.
Artemis 1 made its full stack debut in mid-March, when the vehicle and MLP first switched from VAB to the wet dress rehearsal site, which began on April 1. But the technicians encountered problems during this experiment; three separate attempts to complete the wet dress were worn out due to complications during SLS loading operations.
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The Artemis 1 team threw the Artemis 1 stack back to VAB on April 25th, then spent about a month in renovations and upgrades to pave the way for another wet dress experience. Failures in charging during the first wet garment place a predominant focus on these systems during this morning’s cryogenic charging procedures.
The built-in countdown delay took effect early this morning and was expected to last 1.5 hours. During this time, mission leaders briefed on the time and tanking of vehicles and had initially received a “departure” from Blackwell-Thompson, but the detention was extended when operators encountered a problem with the supply valve in the backup nitrogen gas system of the Pad 39B. According to Derol Neil, a NASA spokesman for the live broadcast of the wet dress agency, the valve “will not close”, although the fault is “not in the valve itself, but in the controller”.
Technicians were unable to immediately determine the cause of the problem, but they replaced the valve. The affected nitrogen gas line was initially identified as excess feed to the substrate. However, after replacing the valve, the engineers reassigned this leg for primary use and the unaffected line as a new spare. “Manual re-testing of this valve works well, according to the team there,” Neil said during the broadcast.
Nitrogen gas is used at site 39B to clean fuel tanks, umbilical tubes and other cavities inside the SLS, both before and after the tank. The time of Artemis 1 back in VAB after the first attempt at wet clothing allowed some planned site improvements to move forward ahead of schedule. One of these improvements included improving the supply of nitrogen gas to the substrate, which almost doubled its capacity.
“We passed and did a test to check this [the gaseous nitrogen upgrades] supported all our pre-deployment needs, “Blackwell-Thompson told Space.com during a news conference on June 15.” We went through all the flow profiles, checked all the pressures, and also checked all the timelines with some margin to ensure that our flow rates and our needs can be supported during our wet dress rehearsal. “
Assistant Launch Director Jeremy Greber joined NASA’s post-broadcast update after the valve resolution, informing listeners that “the problem has been cleared and we are in a good configuration to start cryocharging [and] is no longer limited. “According to Neil, Blackwell-Thompson gave the opportunity to continue with the morning cryogenic tanking procedures just before 9 a.m. (1:00 p.m. GMT today) and the countdown resumed at 9:28 a.m. EDT (1,300 GMT).) to corrected T-0 from 16:38 EDT (2038 GMT).
The two stages of the SLS rocket are powered by liquid oxygen (LOX) and liquid hydrogen (LH2). The charging process of both involves supercooling the propellants and cooling the associated hardware before tanking. Technicians closely monitor the rate of refueling, starting with slow filling and increasing to peak flow rates as umbilical cords and fuel tanks acclimatize to extremely low temperatures. Once almost full, the transfers are reduced to a top speed before moving on to an even slower flow, comparable to the evaporation of fuel, which causes the navel to break and start.
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The LOX slow charge for the SLS main stage started this morning at 10:08 am (14:08 GMT) and reached fast charge speeds fifteen minutes later. In what is known as the ‘rear stand limit’, which refers to the voltage at the connection points for the bottom of the SLS solid rocket boosters, according to Nail, the LOX tank of the basic stage cannot be filled to more than 49%, while the LH2 tank depletion sensors are completely covered.
To take care of some of the lost time in the morning, the mission operators were able to speed up the cooling procedures for LH2 for the propellant and umbilical tubes. This cooling also includes ICPS vent valves, which experienced pressure spikes during the first wet Artemis 1 dress. After this test, NASA technicians added these components to the cooling procedures prior to filling the LH2 for the base stage.
Operators were able to start the slow charging of LH2 by 10:42 AM EDT (1442 GMT). At 11:30 EDT (15:30 GMT), after the tank bottom depletion sensors were submerged, the LH2 transfer speeds were switched to fast flow, placing the two first-stage fuel tanks on the road to reach the target T -0 at 16:38 EDT (2038 GMT).
Although the LH2 tank is basically the largest of the rocket – coming with 537,000 gallons (2 million liters) – it was also the tank that had to be replenished first. The transfer of LH2 from the main stage of SLS started the refill flow at 12:42 (1642 GMT), which allows operators to start cooling LH2 for ICPS about 20 minutes later.
The first stage LOX tank holds 196,000 gallons (740,000 liters) – less than half the volume of the LH2 tank – but the vehicle’s liquid oxygen is …
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