A crucial step in the ambitious Artemis program, NASA will try to launch its massive SLS rocket again on Saturday. The mission will carry an unmanned Orion spacecraft all around the moon and back. Managers announced Tuesday that engineers had found a solution after being hampered on Monday by difficulties bringing one of the rocket’s four shuttle-era engines up to the necessary pre-start temperature.
At 4:07 PM EDT on Thursday, the launch crew will begin a new countdown, presuming final approval to continue. The Artemis 1 mission will launch at 2:17 p.m. on Saturday, one day later than NASA’s initial backup launch date. A 60% likelihood of inclement weather is expected for the rocket’s two-hour launch window, so the crew will once again have to work around the weather.
In an effort to increase cooling for all four of the RS-25 engines, the core stage fuelling technique will be changed, according to NASA’s mission management team chairman Mike Sarafin. In order to strengthen sealing and avoid leaks like the one that happened momentarily on Monday, fittings surrounding a fuel-line umbilical at the foot of the rocket will also be tightened.
We decided to operationally alter the gasoline loading technique and begin our engine chill down sooner, or what was known as “option 1,” Sarafin stated. In order to fix the leak we discovered at the hydrogen tail service mast umbilical, we also agreed to carry out some work at the pad. Furthermore, we decided to shift our debut day to Saturday. On Thursday, the Mission Management Team will meet again to discuss our flight justification and general preparation.
The solid rocket boosters and the core stage will launch the Orion capsule into an elliptical orbit while accelerating to 70 mph (straight up) in only seven seconds. The capsule is carrying instrumented test dummies as well as a variety of sensors and experiments. United Launch Alliance’s upper stage of the rocket will then launch the spacecraft out of Earth’s gravity and onto a course towards the moon.
The spacecraft will make a near flyby of the moon before launching into a far-off orbit that will take it beyond the range of any human-rated spacecraft. On October 11, the spacecraft will return to Earth after another lunar flyby and splash down in the Pacific Ocean to the west of San Diego.
In order to prepare for the flight of four men around the moon in late 2024, the Artemis 1 mission will put the SLS rocket and the Orion spacecraft to the test, including a high-speed, high-temperature re-entry. The first Artemis lunar landing is anticipated to take place between 2025 and 2026.
NASA must launch the Artemis 1 mission within certain “windows” due to the continually shifting locations of the Earth and moon as well as the rocket’s capacity to attain the intended trajectory. The fact that the battery powering the upper stage’s self-destruct mechanism has to be repaired every 25 days and can only be done there at NASA’s Vehicle Assembly Building further complicates the situation.
This implies that the Artemis 1 mission must start by Monday in order to avoid having the rocket towed back to the VAB, which would postpone another launch attempt until October at the earliest or, more likely, until late September. The SLS rocket is essential to the Artemis mission, and NASA officials and engineers want to be certain it operates as intended before sending people to the moon.
On March 18, 2021, at the SSC in Mississippi, engineers conducted a full-duration test fire of the core stage engines, which lasted for eight minutes. In order to prepare for launch, the rocket was then transported to the Kennedy Space Center.
On April 3, NASA performed a dress rehearsal countdown and fueling test, a crucial step in ensuring that the rocket, launch pad, and ground systems function as intended. However, a series of primarily ground-system issues prohibited engineers from loading propellants.
On April 4 and 14, two further efforts to refuel were unsuccessful because of other unconnected issues. On June 20, engineers were finally able to completely load the core stage, but only after a leaking quick-disconnect connection was isolated. This was necessary for a real launch since the flow of hydrogen coolant to the core stage engines was being obstructed.
On August 16, the SLS rocket was wheeled back out to pad 39B to prepare for launch after the quick-disconnect had been fixed back in the Vehicle Assembly Building.
The revised quick-disconnect seemed to function correctly during Monday’s launch attempt. Once the tanks in the core stage were full, liquid oxygen and hydrogen were circulated through the engine’s pipes to get them ready for the very low temperatures of the propellants (-423 degrees Fahrenheit for hydrogen and -297 degrees Fahrenheit for oxygen).
But none of the engines heated up to the desired level. Engines 1, 2, and 4 reached around -410 degrees, however engine No. 3 only got to about -380 degrees. Trying to figure out what was wrong, engineers sent all the hydrogen coolant to engine 3, but it still didn’t reach the temperature it was supposed to.
The data from engine 3 may be caused by a malfunctioning sensor, according to engineers, according to John Honeycutt, manager of the SLS program at the Marshall Spaceflight Center. Data from other sources and pressure measurements suggest satisfactory cooling.
He said that the behavior of the sensor “doesn’t square up with the physics of the scenario.” So, in order to determine whether or not we have all of the engines cooled down, we will be examining all of the other data we have. Engineers think they can cool each of the four engines as required by beginning the chill down cycle approximately 45 minutes early when the engines are close to ambient temperature.
The rocket’s test fire at the Stennis Space Center last year followed a similar process. The engines in that instance were appropriately cooled and started normally for a full-duration “green run.”
According to the data we currently have, Honeycutt stated, “We believe we can do something similar to what we did at the Stennis Space Center to put ourselves in a better position for launch.” Before granting the go-ahead to conduct a launch attempt, the crew will evaluate all the data on Thursday, as Sarafin said. In order to create the flight logic, the crew is now looking through the data, according to Honeycutt. I don’t have it now, but I anticipate that we will be able to get there.
Source: CBS News