Launch timeline in pdf
Jonathan McDowell is asking for numerical trajectory data
Preliminary:
LEO Insertion: 162 km x 1,801 km parking orbit.
• HEO Phase: 42-hour checkout in a high-eccentricity orbit (e approx. 0.88).
• TLI Burn: Delta v boost to reach escape velocity (v_e approx. 11.2 km/s).
• Lunar Flyby: Pericynthion at approx. 10,300 km from the surface.
• Max Distance: 400,171 km from Earth (The d_max human record).
• Entry Interface: 122 km altitude at Mach 32 (40,000 km/h).
Scott manley comments
SLS reference guide
2 feb
Engineers conducted a first run at terminal countdown operations during the test, however, the countdown stopped at 5 minutes left due to a spike in the liquid hydrogen leak rate. Crew safety remains the highest priority.
Engineers pushed through several challenges during the two-day test and met many of the planned objectives. To allow teams to review data and conduct a second wet dress rehearsal, NASA now will target March as the earliest possible launch opportunity for the flight test.
Moving off a February launch window also means the Artemis II astronauts will be released from quarantine, which they entered in Houston on Jan. 21. As a result, they will not travel to NASA’s Kennedy Space Center in Florida Tuesday as tentatively planned. Crew will enter quarantine again about two weeks out from the next targeted launch opportunity.
NASA began the approximately 49-hour countdown at 8:13 p.m. EST on Jan. 31. Leading up to, and throughout tanking operations on Feb. 2, engineers monitored how cold weather at Kennedy impacted systems and put procedures in place to keep hardware safe. Cold temperatures caused a late start to tanking operations, as it took time to bring some interfaces to acceptable temperatures before propellant loading operations began.
Moving off a February launch window also means the Artemis II astronauts will be released from quarantine, which they entered in Houston on Jan. 21. As a result, they will not travel to NASA’s Kennedy Space Center in Florida Tuesday as tentatively planned. Crew will enter quarantine again about two weeks out from the next targeted launch opportunity.
NASA began the approximately 49-hour countdown at 8:13 p.m. EST on Jan. 31. Leading up to, and throughout tanking operations on Feb. 2, engineers monitored how cold weather at Kennedy impacted systems and put procedures in place to keep hardware safe. Cold temperatures caused a late start to tanking operations, as it took time to bring some interfaces to acceptable temperatures before propellant loading operations began.
LH2 TSM2 leak
During tanking, engineers spent several hours troubleshooting a liquid hydrogen leak in an interface used to route the cryogenic propellant into the rocket’s core stage, putting them behind in the countdown. Attempts to resolve the issue involved stopping the flow of liquid hydrogen into the core stage, allowing the interface to warm up for the seals to reseat, and adjusting the flow of the propellant.
Teams successfully filled all tanks in both the core stage and interim cryogenic propulsion stage before a team of five was sent to the launch pad to finish Orion closeout operations. Engineers conducted a first run at terminal countdown operations during the test, counting down to approximately 5 minutes left in the countdown, before the ground launch sequencer automatically stopped the countdown due to a spike in the liquid hydrogen leak rate.
Teams successfully filled all tanks in both the core stage and interim cryogenic propulsion stage before a team of five was sent to the launch pad to finish Orion closeout operations. Engineers conducted a first run at terminal countdown operations during the test, counting down to approximately 5 minutes left in the countdown, before the ground launch sequencer automatically stopped the countdown due to a spike in the liquid hydrogen leak rate.
In addition to the liquid hydrogen leak, a valve associated with Orion crew module hatch pressurization, which recently was replaced, required retorquing, and closeout operations took longer than planned. Cold weather that affected several cameras and other equipment didn’t impede wet dress rehearsal activities, but would have required additional attention on launch day. Finally, engineers have been troubleshooting dropouts of audio communication channels across ground teams in the past few weeks leading up to the test. Several dropouts reoccurred during the wet dress rehearsal.
The team carried out updated procedures to purge the Orion service module’s cavities with breathing air during closeout crew operations rather than gaseous nitrogen to ensure the team assisting the crew into their seats and closing Orion’s hatches can safely operate in the White Room.
With March as the potential launch window, teams will fully review data from the test, mitigate each issue, and return to testing ahead of setting an official target launch date.
What's happened before WDR 2:
As for why SLS is still experiencing these same hydrogen leaks after three years between missions, NASA officials have some theories, but haven't quite nailed down a definitive cause. "These are very bespoke components," NASA Associate Administrator Amit Kshatriya said Tuesday, describing each SLS as its own unique vehicle to learn and understand.
The leaky seal could possibly be a result of vibrations incurred during the rocket's initial rollout to the pad,, Kshatriya said. It took the Artemis 2 SLS rocket nearly 12 hours to make the 4-mile trip to the pad from the VAB at a top speed of 1 mile an hour last month.
"That rollout environment is very complicated," he added, noting that the Artemis 1 SLS was put through different acceleration tests on its way between the VAB and the pad at Launch Complex-39B specifically to help determine the effect of such stresses on the rocket and launch platform. "We think that's a contributor. But again, we have to tear the seal apart and see what happened."
"We really did learn a lot from the Artemis 1 mission, and we implemented a lot of the lessons learned yesterday through wet dress," Lori Glaze, NASA's Exploration Systems Development Mission Directorate acting associate administrator, said during a post-wet dress rehearsal press conference on Tuesday.
"Everyone's aware of some of the challenges with the hydrogen tanking from Artemis 1, and we've made some changes," Glaze said.
Despite the hours of troubleshooting the persistent hydrogen leak — which NASA officials say was stabilized within acceptable limits (but never eliminated) —mission operators managed to fully fuel both SLS stages and carry the test down to the simulated clock's terminal count (the last 10 minutes before liftoff). But the team didn't quite get as close to T-0 as needed in order to earn NASA's gold stamp of approval to launch with a crew onboard.
"The fact that we got to full tanking yesterday on the first try was a tremendous success, and we gathered an enormous amount of data in the processes and how we want to go forward with that in the future," Glaze said.
At T-5 minutes 15 seconds, the SLS ground launch sequencer terminated the count due to a spike in the same quick disconnect hydrogen leak it had experienced all afternoon, which was cause to abort the test, NASA said.
"As we began that pressurization, we did see that the leak within the cavity came up pretty quick," Artemis Launch Director Charlie Blackwell-Thompson said during Tuesday's press briefing, referring to a cavity on the rocket's mast umbilical. The activity triggered safety procedures already in place for such contingencies, she added.
"We got into our safety steps. We saw the hydrogen concentration come down and then later in the evening, we got into our drain operation," she said.
While maintaining the wet dress rehearsal an overall success in terms of data gathered and the accolade of filling SLS's tanks on the first try, Blackwell-Thompson also assured that, unlike Artemis 1, the hydrogen hiccups can likely be addressed at the pad, and don't seem to warrant a rollback to the VAB for maintenance.
"During Artemis 1, we found out that we can do some work on these plates at the pad," Blackwell-Thompson said. "I had hoped that we would not have to demonstrate that again for Artemis 2, but we showed that we can go do this work at the pad and be ready for launch."
As for why SLS is still experiencing these same hydrogen leaks after three years between missions, NASA officials have some theories, but haven't quite nailed down a definitive cause. "These are very bespoke components," NASA Associate Administrator Amit Kshatriya said Tuesday, describing each SLS as its own unique vehicle to learn and understand.
The leaky seal could possibly be a result of vibrations incurred during the rocket's initial rollout to the pad,, Kshatriya said. It took the Artemis 2 SLS rocket nearly 12 hours to make the 4-mile trip to the pad from the VAB at a top speed of 1 mile an hour last month.
"That rollout environment is very complicated," he added, noting that the Artemis 1 SLS was put through different acceleration tests on its way between the VAB and the pad at Launch Complex-39B specifically to help determine the effect of such stresses on the rocket and launch platform. "We think that's a contributor. But again, we have to tear the seal apart and see what happened."
"This is the first time this particular machine has borne witness to cryogens. And how it breathes, and how it vents, and how it wants to leak is something we have to characterize," Kshatriya said, and testing before the launch pad can only go so far.
Even with an "aggressive approach" to dealing with hydrogen leaks during Artemis 1, "we're pretty limited as to how much realism we can put into the test," said John Honeycutt, the chair of NASA's Artemis Mission Management team. "We try to test like we fly, but this interface is a very complex interface, and when you're dealing with hydrogen, it's a small molecule, it's highly energetic," he said, admitting he and mission managers weren't expecting these issues to crop up again.
"This one caught us off guard," Honeycutt added. "The initial things that we were seeing in the technical team felt like we either had some sort of misalignment or some sort of deformation or debris on the seal."
NASA mission blog
DutchSpace twitter
NASA press conference YouTube
LH2 full fill, a success
22 Feb
Rollback to fix helium flow in upper stage
Nasa blog
留言
張貼留言