Wiki Super Heavy/Starship - General Development Discussion

[ecarfan]

I’m confused about what I heard. Visually it looked like the engines ignited before the LC said “ignition” (which came immediately after he said “2” in the countdown sequence; shouldn’t ignition come right after “zero”?) and then he said “plus one”, “plus two”, and then “full duration” but that didn’t seem like 6 seconds of firing.

I’m speculating there will be one or two more static fires before launch.

 

[ecarfan]

NSF shows in their live feed that “31 engines fired full duration, two shutdown early”.

 

[mongo]

Separately, people have been commenting that the low wall they put up on the "soil" side of the launch area seems too low to do anything useful (e.g. contain the deluge outflow). In watching the test video, I wonder if it exists to reduce erosion. A low wall would suffice to ruin the flow of exhaust low to the ground, ensuring that it doesn't get a chance to go straight into the surrounding soil.

The wall only needs to be higher than the other side with the retention pond (plus flow pressure). Additionally, there is a lot of area behind it. For a 50 foot diameter circle, every foot of depth is 2,000 cubic feet or around 15,000 gallons.

 

[ecarfan]

Love this view. Was pleased to see that SpaceX decided to livestream the static fire, since only they can give us views like this!

 

[JB47394]

Love this view. Was pleased to see that SpaceX decided to livestream the static fire, since only they can give us views like this!

Did you notice the way that condensation came from various engines in a particular sequence? I wonder if that matches the firing sequence, where they keep cycling through the engines like that during the chill phase, then light them off using the same sequence.

 

[Electroman]

2 engines shut down early. Does that not mean this test is not a full success ?

 

[scaesare]

NSF shows in their live feed that “31 engines fired full duration, two shutdown early”.

So a couple of days ago in this thread we were discussing the engine-out probs that SpaceX has had, and the conversation took to internal plumbing vs, QD's to spin the engines up, and the fact that recent spin prime tests might indicate they were working through issues getting them to light.

The "shutdown" early comment implies they were lit, but didn't stay that way.

I feel like early shutdown has been an issue reported in earlier tests as well. Does anybody else recall that (I will try and rewatch earlier tests if I get a chance).

If so, I wonder if that implies plumbing issues as @JB47394 mentioned earlier, or if there are internal engine problems. Given test stand success, I assume more likely the former, or some other on-booster interaction (shock waves from nearby engines, etc...)

 

[JB47394]

2 engines shut down early. Does that not mean this test is not a full success ?

It's not a full success. My understanding is that they can go with as many as three engines out. So if this had been the situation for a launch, they would have flown. On the first static fire they had four engines out, which is why the whole thing shut down before full duration.

I feel like early shutdown has been an issue reported in earlier tests as well. Does anybody else recall that (I will try and rewatch earlier tests if I get a chance).

If so, I wonder if that implies plumbing issues as @JB47394 mentioned earlier, or if there are internal engine problems. Given test stand success, I assume more likely the former, or some other on-booster interaction (shock waves from nearby engines, etc...)

They've had a combination of failed-starts as well as shutdowns. The engines are tested extensively in isolation and are extremely reliable. So if it's not the engines themselves (94% fired fine during the test), then it's something that changed between the test stand and the static fire. That's pretty much everything except for the internals of the engines. Each engine has a unique environment around it, including pressure, vibration, temperature, propellant delivery, and so on. It could even be the engine start sequence triggering something. The business end of a booster is an incredibly complex environment.

 

[ecarfan]

Each engine has a unique environment around it, including pressure, vibration, temperature, propellant delivery, and so on. It could even be the engine start sequence triggering something. The business end of a booster is an incredibly complex environment.

Very good points. I cannot imagine how hard it must be to computer model all the variables in that 33-engine environment to try to predict what happens when igniting that many engines so close together. It’s amazing to me that SpaceX has made so much progress so quickly with the Starship booster. They are getting very close to a successful liftoff!

 

[scaesare]

It's not a full success. My understanding is that they can go with as many as three engines out. So if this had been the situation for a launch, they would have flown. On the first static fire they had four engines out, which is why the whole thing shut down before full duration.

They've had a combination of failed-starts as well as shutdowns. The engines are tested extensively in isolation and are extremely reliable. So if it's not the engines themselves (94% fired fine during the test), then it's something that changed between the test stand and the static fire. That's pretty much everything except for the internals of the engines. Each engine has a unique environment around it, including pressure, vibration, temperature, propellant delivery, and so on. It could even be the engine start sequence triggering something. The business end of a booster is an incredibly complex environment.

Yeah, suspect that you are correct, and what I was also saying when I referred to "plumbing issues ... or some other on-booster interaction (shock waves from nearby engines, etc...)" in agreement with your earlier post.

I have to imagine the fluid dynamics of the fuel & oxidizer alone have to be extremely complex feeding the vast volume 33 of those monsters require. Your "startup sequence" comment also feels very likely for the cases where they never lit to begin with. Or perhaps starting later sets of engines starves the earlier-lit ones and they shut down...

 

[ls7corvete]

Everyday astronaut had a recent video on how complex startup sequences can be.

 

[ecarfan]

 

[scaesare]

Yeah, I've seen that video before... the process for Raptor is certainly complex, being a full-flow staged combustion methalox engine. But apparently they start reliably enough in isolation on a test stand.

It's the additional complexity of either starting them, or keeping them running, when installed on the booster alongside 32 of their counterparts, that I'm wondering about, as that seems to be the issue.

 

[scaesare]

In a discussion over at the NSF forum, somebody made the point that these also may be very conservative sensor thresholds commanding engine shutdown (or not allowing light to proceed) while they are gaining data. As they get more operational knowledge they should be able to tune and potentially relax those as they have done on the Merlins...

Also, it appears that the static fire was done with Raptor V2's, and V3's are on their way, so many things may already have been addressed.

 

[Cosmacelf]

We all have to remember that we are still in the engineering prototype stage, so there is no such thing as a failed test. All tests gather data to iterate towards the first production booster.

 

[JB47394]

We all have to remember that we are still in the engineering prototype stage, so there is no such thing as a failed test.

I understand your meaning, but the booster certainly failed to achieve the test objectives. The test itself was a success because they were able to find out whether the booster could achieve the test objectives. A pyrrhic victory.

 

[Buckminster]

https://twitter.com/x/status/1697839090186531066

Elon should call this Darth Powell mode. Brrrr.

 

[Grendal]

https://twitter.com/x/status/1697442574099947530

 

[JB47394]

CCSC = NASA's Collaborations for Commercial Space Capabilities (CCSC-2 is the Second such program)
SAA = Space Act Agreements (proposals for collaborations with NASA)
PDR = Preliminary Design Review

So note that the Q4 2028 milestone is for a design review of a space station. The flight goals go no farther than Q3 2024 with "Successful Starship Recovery". Which, interestingly, is listed as "Successful recovery of the Starship system". I have to assume that means both booster and Starship.

From the link on CCSC:

The first CCSC agreements resulted in four collaborations associated with development of commercial launch vehicles, spacecraft, and space suits:

• Northrop Grumman developed its Mission Extension Vehicle (MEV) to reliably and safely rendezvous and dock with a client satellite running low on fuel, taking over its attitude and orbit maintenance. Two of these MEVs have been successfuly fielded for ongoing commercial missions.
• Final Frontier Design matured its space suit designs for high altitude and space flight, and after acquisition by Paragon Space Development Corporation, is supporting NASA’s Extravehicular Activity Services (xEVAS) Contract.
• SpaceX developed its Starship fully reusable transportation system designed to carry both crew and cargo to Earth orbit, the Moon, Mars, and beyond. Starship is currently undergoing flight tests.
• United Launch Alliance developed its new Vulcan Centaur launch vehicle that will replace its Atlas and Delta systems, and provide higher performance and greater affordability. Vulcan Centaur’s initial flight is planned for first quarter 2023.

 

[ecarfan]

So note that the Q4 2028 milestone is for a design review of a space station.

Thanks for pointing that out! Note: the Starship LEO crewed spaced station has been discussed in this thread.

Hoping SpaceX makes a lot of progress towards creating the first LEO tourist destination in space before I get too old.

And yes, I’m not assuming that the “space station” in question is for tourists, it probably is not.