Artemis

[Dakota Tebaldi]

At 40 minutes on the clock, the countdown has entered a hold while the vehicle engineers troubleshoot the engine issue.

 

[Dakota Tebaldi]

The launch team believes the engine problem could not be fixed in time to make the launch window today, so today's launch is SCRUBBED.

The next launch window is Friday afternoon. But whether they will attempt to launch on that day hinges on what they figure out with the engine.

Before a launch can happen, the engines - kind of like the fuel delivery lines from earlier when the tanks were being filled - have to be pre-chilled. It may seem counterintuitive, but while the engines are RUNNING, the exhaust nozzles are actually colder-than-ice-cold; they have to be, because the heat of the rocket exhaust would destroy them if they weren't actively cooled. They're so cold that there's literally frost on the outsides of the nozzles AS the rocket engines are running. The way this cooling happens is that the cryogenic fuel - the liquid hydrogen - from the tanks is first pumped through a system of tubes and pipes and passages all over the nozzles and the around the actual engine itself before the hydrogen actually gets injected into the reaction chamber of the engine.

Obviously before the engine can run all the air has to be bled out of that cooling pipe network, filling it with the liquid hydrogen and basically priming the engine to start. They were doing a test bleed on the engines when this problem arose - three of the engines completed their bleeds properly but the fourth engine - specifically, Engine Number 3, wasn't cooling down far enough to the correct temperature range. The engineers thought this might be some kind of pressure problem, and they tried a variety of things, cycling the bleed procedure (basically the equivalent of turning it off and then turning it back on again), shutting the valves on all the rest of the engines, and even pressurizing the hydrogen tank to try and push hydrogen into the system. But they still haven't gotten that engine to cool to the right temperature.

So although the launch is scrubbed, the vehicle is actually being kept fueled, at least for the time being, so that the engineers have a full pressurized tank to use while they work on this problem, which they will be doing until it's solved.

 

[Noodles]

So, somewhat related. I don't understand why Uverse, which is the service at work I can watch NASA on, is using the SD channel only for NASA.

 

[Dakota Tebaldi]

So, somewhat related. I don't understand why Uverse, which is the service at work I can watch NASA on, is using the SD channel only for NASA.

That IS pretty odd. NASA provides feeds all the way up to 4K I'm pretty sure.

 

[Free]

So, somewhat related. I don't understand why Uverse, which is the service at work I can watch NASA on, is using the SD channel only for NASA.

Probably to cut down on their transmission costs.

 

[Dakota Tebaldi]

Clear your weekend, it's time to try again!

 

[Dakota Tebaldi]

It's still a ways off but the current forecast for Saturday afternoon shows isolated showers at the Cape. Lightning is a no-go condition, but rain in the area is acceptable - at the pre-launch briefing last weekend before the first attempt, the weather officer said the constraint is that the vehicle should not be flying THROUGH any rain during ascent. If the rain is sporadic, there should be some clear moments during the window to launch through.

 

[Dakota Tebaldi]

Missed this one XD

 

[Dakota Tebaldi]

Between now and launch day, engineers have basically two things planned. Firstly they're getting some people out to the pad to see if they can address that small hydrogen leak where the umbilical attaches to the side of the rocket. As far as that goes, they're expecting to just have to torque a couple of bolts a bit more.

Secondly, they're changing the prelaunch operations to start the engine bleed earlier in the countdown, since the issue was that the one engine wasn't supercooling fast enough to reach the required temperature by launch. The schedule they're shifting to is the one that was used to prepare this same core stage and these same engines for the successful hot-fire test at Stennis Space Center last year.

NASA also has new coverage times for us:

The countdown for launch is scheduled to resume Saturday at 4:37 a.m., at the L-9 hour, 40 minutes planned hold in the countdown where managers receive a weather briefing and conduct a poll on whether to proceed with propellant loading operations. Launch controllers do not need to begin the initial 46 hour, 10 minute countdown again because many of the configurations needed for launch are already in place.

On Saturday, live coverage of tanking operations with commentary on NASA TV will begin at 5:45 a.m. EDT. Full launch coverage in English will begin at 12:15 p.m. and NASA en espanol broadcast coverage will begin at 1 p.m. EDT. Click here for the latest information on launch briefings and events.

Weather forecast for Saturday is 60% favorable right now.

 

[Noodles]

So is the planned lift off time around 2:17 with the new launch window, assuming everything goes smooth?

 

[Dakota Tebaldi]

So is the planned lift off time around 2:17 with the new launch window, assuming everything goes smooth?

Yep! 2:17 is the earliest the rocket can ignite and lift-off, and it has two hours after that point to do it if it's going to happen that day.

The next launch window after the Saturday attempt is Monday afternoon.

 

[Dakota Tebaldi]

At the pre-launch briefing today the relevant people went over the problems with Monday's launch attempt and what has been done to address them. It looks like all the work was done as of this afternoon.

Firstly, that small leak in the hydrogen fill line at the service tower umbilical. It wasn't bad enough to stop the launch on its own, but some engineers went up and took care of it anyway. It sounds like they found what they believed to be the source of the leak and repaired it, and put everything back together so that should be a non-issue.

There was also an issue where before the launch engineers saw what looked like a crack near the top of the core stage. During the launch countdown the engineers had already determined that it was a marred area just on the thermal insulating foam, not a structural crack in the rocket itself, but while they had the opportunity they took a closer look at that too, and verified it wasn't a problem.

Finally, the engine. Engineers have been testing and poring over data from the launch for the last couple of days, and their determination is that the problem was a bad temperature sensor. All the rest of the data showed that the proper volume of hydrogen was flowing completely through the engine at the correct rate, the same as with all of the other engines - only that temperature sensor was showing a reading that didn't make sense. The rocket would have to be taken back to the VAB and unstacked just to replace that sensor which would push the launch back by weeks if not months, so instead of doing that, in addition to the new earlier bleed procedure just to make sure, they've figured out what other, known-good sensors they should watch in order verify that fuel is flowing properly during the bleed.

 

[Dakota Tebaldi]

There's a little under 3 and a half hours remaining in the count right now and the vehicle is tanking - but, again, there's a problem with hydrogen delivery. Liquid oxygen is full now, but there is a leaking seal on, it seems, the hydrogen umbilical line again still? I just got up so I'm getting caught up to speed but it sounds like this particular leak is different and a bit worse than the one they dealt with on the previous launch attempt Monday. As of now they've tried twice to thermally cycle the seal to get it to seat properly but those attempts didn't work, so they're deciding what to try next. Liquid hydrogen is about 10% full atm.

If this launch attempt has to be called off, the next window is Monday again, a bit later in the afternoon.

 

[Dakota Tebaldi]

Looks like another scrub for today. That hydrogen leak is too bad.

The next opportunity like I said is Monday, but I'm not sure it's going to happen that fast. It sounds like this is something that will need a physical repair and that's going to take at least a couple of days. I'm not super-certain exactly where or what the nature of this leak is, except that it is a hydrogen delivery line leak and it is apparently not the same component that had leaked on Monday (that leak was a tiny one and they managed to fix it this week) and may not even be in the same area. I'll learn more at the post-attempt news conference and share.

Anyways, team is de-fueling and safe-ing the vehicle. Just remember that failures are always better before launch than during launch.

 

[Dakota Tebaldi]

Okay so here's the deal. The engineers are fairly confident that the leak is in a soft seal in the quick-disconnect fitting where the hydrogen fill line mates with the side of the rocket. This actually is in the same area on the service umbilical as the leak from Monday, but it is a different component.

It was a pretty substantial leak. It was first noticed when the tanking shifted from slow-fill to fast-fill, as I described a couple of days ago. It's not known why this leak developed. There was a brief overpressure incident during pre-chilling this morning that might have caused it, but they don't know yet and it's a question they'll be working on answering in the coming days.

The important takeaway though is that the issue can't be fixed during the current launch period, and the team has suggested the period beginning September 26th as the earliest target for launch. So it'll be a few weeks until they try again.

So right now the engineers intend to replace the soft seals on the fitting, but they have to decide whether to do it in situ with the vehicle on the pad, or roll Artemis back to the VAB and do the replacement there. Both choices have a pro and a con. Doing it on the pad means the repair has to be done in the open and unsheltered from the elements which is less than ideal, but with the advantage that once the repair is done they can actually do a test-fueling with the hydrogen right there and make sure it's good. Rolling back to the VAB gives the team a controlled environment in which to work, but they cannot perform tests with cryogenic fluids in the VAB, they can only do a test at ambient temperatures, which may not be fully revealing. The engineers will weigh both options and decide by early next week what they will do.

 

[Dakota Tebaldi]

 

[Dakota Tebaldi]

 

[Lexxi]

Bah. Everytime I saw the word seal, I saw this (stupid words that mean more than one thing):


Rocket seal:

 

[Dakota Tebaldi]

In case you're wondering, the "flight termination system" is basically the rocket's self-destruct system.

Have you ever read a news story about a rocket launch in China where something goes wrong and the rocket just....ends up crashing into some small village downrange (I think it's happened more than once)? Or seen this video from Russia:


In the US, rockets are required to have a flight termination system. Rocket launches are monitored VERY closely, and if something goes wrong where it becomes apparent the rocket has or will imminently lose directional control, the flight termination system destroys the engine so that the rocket will immediately fall straight down and explode within the boundaries of the range. It looks like this when it happens:


On a crewed rocket like the Apollo was (and Artemis will be), the smaller escape rocket at the top would fire and pull the crew module safely away while the rest of the launch vehicle asplodes.

Anyway, this self-destruct system runs off a set of batteries. They're charged in the VAB before the rocket is rolled out to the pad, and verifying that they're charged is an item on the loooong list of things that the range controllers at Kennedy require in order to give the rocket a temporary certification to launch. Like all batteries though, they don't stay charged forever. And they can't be charged at the launch pad either; if the range decides that it's been too long and there's a risk they're no longer charged enough to run the FTS, they will revoke the certification and Artemis will HAVE to be rolled back to the VAB to recharge them before it can launch. If that's the case, the launch would likely happen sometime in mid-October.

 

[Soen Eber]

The major hitch here is congress mandated that NASA should use existing technologies for the new effort, which means the engines and fuel system are based on using hydrogen gas. It has been notorious for frequent shuttle delays, and Artemis is continuing to hold to that long-standing tradition.

I'm no expert, I've only read a couple articles detailing the hydrogen fuel woes so I'll let someone else with more grounding expand on this.