Artemis 1 going to the Moon (launched Nov 16)

  • Topic: NASA 
  • Thread starter Thread starter mfb
  • Start date Start date
  • Tags Tags
    Moon
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
Sign up Log in
183 replies · 24K views
PeroK said:
Why do things not work these days? Perhaps that's an unfair assessment?
I have heard today about regulations here concerning fire prevention after a major fire at an airport years ago. Someone commented on them as overregulation that hinders efficiency too restrictively. I could imagine that NASA suffers similar problems after the shuttle disasters.
 
Physics news on Phys.org
fresh_42 said:
I have heard today about regulations here concerning fire prevention after a major fire at an airport years ago. Someone commented on them as overregulation that hinders efficiency too restrictively. I could imagine that NASA suffers similar problems after the shuttle disasters.
It doesn't sound "too restrictive" to me. The LH leak limit is 4%, they are seeing "7% concentration". I have not been able to find an exact and explicit description of what the numerator and denominator are in that 4% limit. However, this LH leak is into an environment rich in O2 - because the LOX also leaks and because there is O2 condensation.

Also, the temperature cycling procedure they are using now was tried twice on Sept 3rd to no advantage.
 
Reply
  • Like
Likes   Reactions: russ_watters and PeroK
11:08am: Temperature cycling complete. New plan: when refueling (LH) this time with a pressure reduction in the storage tank to only 5psi and then a very slow LH pressure build-up.

They have also repeated that the leak stopped immediately after the flow stopped.
 
11:35am NASA Announcement: They are in LH Fast Fill - and apparently no important leak yet.
11:45am NASA Announcement: As the pressure increased, an 0.5% leak has developed.
The % measurement is the concentration of hydrogen in a cavity near the Quick Disconnect.
They are going to continue to increase pressure until the pressure reaches 10% (or the LH tank is full). So it will be allowed to pass the 4% limit.
11:51am: Pressure is up to the minimum required for tanking. H2 concentration in QD Cavity is still about 0.5%.
 
Last edited:
Hydrogen tanks are 27% full, now going up at a good rate.
If this were a launch attempt at the 27th the delay would have been too long for the launch window.
 
The new concentration limit is actually "10% for 5 minutes" - with no further explanation. Not clear to me whether the 5 minutes starts at 4% or 10%.

12:07: 35% LH full, leak concentration is "under 1%" (no longer "about 0.5%").
12:12: Engine kick start bleed has started and is nominal. Leak rate now over 1%.
12:15: Leak concentration topped out at 3.4% with pressure sufficient for the kick start bleed.
 
.Scott said:
It doesn't sound "too restrictive" to me. The LH leak limit is 4%, they are seeing "7% concentration". I have not been able to find an exact and explicit description of what the numerator and denominator are in that 4% limit.
That's the Lower Explosive Limit(LEL) volumetric (and molar) concentration for hydrogen. That they exceeded it means they had an explosive mixture. Really dangerous.
 
russ_watters said:
That's the Lower Explosive Limit(LEL) volumetric (and molar) concentration for hydrogen. That they exceeded it means they had an explosive mixture. Really dangerous.
It's the H2 concentration in the LH QD Cavity. There are two mitigating issues regarding an explosion: 1) That cavity has no ignition sources. 2) The equipment in that region is pretty rugged - a moderate H2 "explosion" could be taken in stride.

But clearly, they are not being overly conservative.

12:25: 50% LH Full. LOX tank full.
 
2/3 full

A bit under 1% per minute, slower than nominal but likely enough for an actual launch attempt. They'll try filling with a higher pressure now to see how the leak behaves.
 
12:43am NASA Announcement: LH 67% tank. NASA has decided to increase the storage tank pressure to nominal.

With the process based on the procedure up to this point, it would take about 2 hours to fill the LH tank.
The 10%, 5 minute limit would stop the fill at either 10% H2 concentration or 5 minutes past 4% concentration.

Also, that QD cavity is apparently pretty small - in the ball park of a few cubic feet.
 
1:11pm NASA Announcement: They just reached "replenish" on the LH tank - so "Fast Fill" has completed successfully.

1:19pm: NASA decided earlier not to start the upper stage fueling on schedule. They are now deciding whether to go for that part of the test or not.

1:35pm: No news on the upper stage test - but NASA will be moving forward on the "prepres" test - bringing the tanks up to the flight pressure and and down to flight temperature levels.

Also, NASA has moved on to the upper stage fueling.
 
Last edited:
2:07pm: Upper stage QD Boot Containment was lost. Has happened before. Doesn't sound very important.
2:11pm: Fast fill for both LOX and LH in upper stage.

(meanwhile - Elon says Starship flight very likely in November)

3:15pm NASA Announcement: Upper stage LH in the "Topping" stage.

The Prepress test is still expected today.

3:27pm: LH upper stage fill is complete.
3:32pm NASA Announcement: Go for the LH2 Prepress test. Replenish and fill and drain valves are closed. Tank vent valve close. Engine bleed with high flow. Simulates flight conditions.
3:36pm NASA Announcement: LH2 Pre-press test started. Upper stage LOX tank is continuing to load.

The Pre-press is the last item on the original checklist for a launch attempt. This doesn't mean that 9/27 launch attempt is go, but its one less item that could stop it.

3:44pm NASA Announcement: LH Leaking crossed the 4% concentration limit - and is holding at about 4%. But this was the 4-inch LH bleed quick-disconnect - not the 8-inch LH feed one that was causing the problem earlier.
3:45pm NASA Announcement: Upper stage LOX fill has completed.
3:48pm NASA Announcement: The pressure test target pressure has been reached. The Pre-press test is complete.

3:56pm NASA Announcement: Core tank is in replenish.
4:12pm NASA Announcement: Pre-press test was successful - and the pressure control was good enough to complete the test in only 15 minutes.
The 4-inch bleed QD reached a little over 5% - but it lowered on its own. In an actual launch, it would have stopped the launch.
4:15pm: LOX Upper stage is nearing completion.

4:31pm: A final replenish test was just completed. That was the last test. They are go for "cutoff" (the simulated countdown) and detanking.

- - -
 
Last edited:
There was actually more information about how the testing was progressing than you commonly get with a SpaceX test.

There was more information about that FTS battery issue. It's sounding to me like the 25-day limit is tied a lot more to guaranteeing regular FTS equipment access to the Range (Space Force) than it is to what might reasonably cause an FTS equipment malfunction. -- So I am a lot more optimistic about NASA getting an extension on the FTS waiver.

I wouldn't guess about whether they will want to do another test before the launch. Sounds like a close call to me.

And .. https://www.nasaspaceflight.com/ announced that they will now have a 24/7 video feed of the NASA Florida launch complex.
 
NASA announced that this test went well enough to go for a 9/27 launch.
This topic will be discussed on NASA Live in 2 hours (12:30pm ET 9/23/2022).

The press release is at: https://www.nasa.gov/press-release/...pdate-on-demonstration-test-artemis-i-mission

"Based on data from the test, teams are fine-tuning procedures for the next launch opportunity, targeted for no earlier than Sept. 27. The rocket remains in a safe and flight-ready configuration at the launch pad."
 
Regarding the Tuesday, Sept 27th:
https://www.nhc.noaa.gov/refresh/graphics_at4+shtml/145524.shtml?mltoa34#contents
145524_earliest_reasonable_toa_no_wsp_34[1].png
 
From Fox Weather:
NASA is hoping to launch on Sept. 27 at 11:37 a.m. EDT. However, that launch window was not entirely up to the space agency. NASA first needed approval from the Space Force, which oversees the Eastern Range, to extend the Flight Termination System certification due to safety requirements. The FTS is required on all rockets and would cause the vehicle to self-destruct if it veers off course and threatens the public.

SLS chief engineer John Blevins shared the good news on Friday that both the Sept. 27 and Oct. 2 backup date were approved by the Space Force.
They have the Space Force waiver. So if they return to the VAB, it'll for the tropical storm, not the FTS.
 
Ars Technica has an interesting article about NASA's plans .

But one caution: The article talks about FTS "battery life" but during the Wednesday live feed it was explained that the FTS waiver issue was not really a "battery life" issue.

What is interesting in the article is that NASA is prepared to leave SLS out in the open during a Tropical Storm (but not a hurricane).

Quoting from the article:
So what is the upside of risking the rocket and spacecraft , which were developed at a cost of more than $30 billion, in a tropical system? By waiting out the weather NASA is seeking to preserve an opportunity to launch on September 27 or October 2. Failing that, it will need to roll back to the hangar regardless.

Doing so would likely push the next launch attempt into the second half of November. "Some life-limited items would be coming up in that case," Blevins said. This appeared to be an admission that for NASA, the clock is ticking on a rocket that has been fully stacked for launch for nearly a year now, and which has critical parts that cannot be serviced in that configuration. In short, NASA officials would very much like to get off the pad as soon as possible.

I can't help noting that Elon recently mentioned November as well.
 
Weather criteria for Artemis 1
Do not launch if the peak liftoff winds exceed a range of 29 knots through 39 knots between 132.5 feet and 457.5 feet, respectively.

Do not launch through upper-level wind conditions that could lead to control problems for the launch vehicle.

Do not launch through precipitation.
"Tropical storm force" winds are >34 knots, so the risk of exceeding the first wind speed limit for the Tuesday launch window is pretty small. Most likely they'll never get TS winds at the launch pad (~30% risk according to the forecast), and even if they do it's probably after the end of the launch window. The other criteria are worse, with just a 20% chance of acceptable weather overall.

Will be interesting to see how this develops.
 
Just to keep in suspense, Tropical Storm Ian has now slowed. Per todays 11am forecast chart below, tropical force winds will arrive at the launch site after 8pm Tuesday.

Will Ian allow the launch or won't it? Stay tuned...

Actually, it could become even more suspenseful than that. On Tuesday night, Ian might be creating conditions unsafe for an unsheltered SLS. So if NASA shoots for that 70 minute window on Tuesday and the launch is scrubbed, we could be watching a Goliath racing to the VAB.

145630_earliest_reasonable_toa_no_wsp_34.png
 
.Scott said:
They will decide on whether to return SLS to the VAB tomorrow.
Looks like they want to keep an October 2 launch an option if the storm moves away, but it's likely they'll go back to VAB.
 
As @mfb noted, the Tuesday launch is unscrubbed - but still far from a certainty.
Hurricane Ian has not moved that much and tropical force winds are not expected at the cape until early Wed. morning - perhaps time to move SLS to the VAB after the launch window has expired.

NASA has postponed a final decision until today.
102341_earliest_reasonable_toa_no_wsp_34.png
 
Last edited:
The following launch window would be October 17 – October 31 but they are unlikely to make that, so we are probably looking at November 12 – November 27 with a backup launch window of December 9 – December 23. They got the FTS extension this time, so I assume they can get it again - preparing for a November 12 launch would give them up to 6 actual launch attempts, three per window. Hurricane frequency should go down.
 
The SLS just arrived at the VAB - so it is now safe from the weather.
With SLS at the VAB, NASA should be able to get caught up on all the scheduled servicing - including the FTS. So I do not expect that they will need an FTS extension.

Edit:
NASA just posted another SLS update:
https://blogs.nasa.gov/artemis/2022...craft -arrive-at-vehicle-assembly-building-2/

And they do mention the replacement of all FTS batteries as part o their planning.
 
They replace the batteries before returning to the launch pad of course - but if they replace them e.g. November 7 then the original 20 days would only cover the end of the November launch window. We could run into the same situation as earlier this month, 2-3 failed launch attempts and the question if the rocket can stay on the pad until the December launch window. Probably yes, because the batteries used in November shouldn't be worse than the batteries installed in August.
 
mfb said:
They replace the batteries before returning to the launch pad of course - but if they replace them e.g. November 7 then the original 20 days would only cover the end of the November launch window. We could run into the same situation as earlier this month, 2-3 failed launch attempts and the question if the rocket can stay on the pad until the December launch window. Probably yes, because the batteries used in November shouldn't be worse than the batteries installed in August.
Somewhere in the NASA coverage I read that if it gets into December, they run into a long list of booster devices expiring - and thus more time in the VAB. Perhaps the "planning" they are doing now will take greater advantage of the VAB visit than just the FTS.
 
From inverse.com.

NASA is coordinating several factors to see what’s the best choice for the next launch target. A launch in October, as early as next week, is not off the table. But Jim Free, associate administrator of NASA’s Exploration Systems Development Mission Directorate, suggested it’s unlikely. Free told reporters he didn’t want Artemis I to return too quickly to the launchpad without first addressing “limited-life items” that need periodic reassessment.

Free also said the team prefers to do a daytime launch, but November’s launch opportunities wouldn’t support that.
 
Teams Confirm No Damage to Flight Hardware, Focus on November for Launch
.Scott said:
Somewhere in the NASA coverage I read that if it gets into December, they run into a long list of booster devices expiring - and thus more time in the VAB. Perhaps the "planning" they are doing now will take greater advantage of the VAB visit than just the FTS.
They have already extended that twice, November vs. December is probably not making a big difference. If they have to re-stack it then it's going to be a long delay.
 

Similar threads

Artemis 2 launch - humans return to the Moon after 54 years
  • mfb
  • · Replies 92 ·
  • Aerospace Engineering
4
Replies
92