News Elon Musk finally got it up. Starship that is.

[Doughie99]

I can post a video tomorrow of Elon talking a bit about the Raptor's engine-lighting procedure. He is quite deliberately vague as it's SpaceX guarded info exactly what happens but it's very obvious it's unusual and complex and things need to work exactly right for engine ignition to happen reliably.

And here, as promised is the video with Elon Musk talking in some detail (not TOO much detail...) about the start sequence of Raptor2 engine, compared to Merlin engines etc :
The reason I'm posting this is because it seems quitre apparent to me that there is still a re-light reliability problem with the Raptor 2.0 engine which makes me suspect that Raptor 2.1 (or Raptor3.0) is in development and will be used sometime this year or next year, to try to fix this issue.

Timestamped:


A short transcript excerpt from that video regarding the ignition sequence etc I am providing here :

Note for transcript below :
Merlin refers to the Merlin engine that powers the Falcon9 and FalconHeavy rockets.
Raptor refers to the much more complex engine that powers Starship system 1st stage booster and 2nd stage Starship.


Elon: "for Raptor1 we have torch igniters in the main chamber..... for Raptor2 has no torch igniters in the main chamber."
Interviewer: "How does it light then?"
Elon: " well....that's secret sauce".

Elon : "If the pre-burner doesn't light or doesn't light exactly right....you've got a challenge. The start sequence for Merlin engine much easier and simpler than the start sequence for Raptor. For Raptor you've got an Oxygen powerhead and a fuel powerhead and they're different shafts and you've got two turbines and two pre-burners and they're crossfeeding one another. So the start sequence for Raptor is insanely complicated compared to the start sequence for Merlin.

You're doing this delicate dance between the fuel power-head and the oxygen power-head and if they get out of synch then you can go stoichiometric in the pre-burners and melt or explode the pre-burners. So.....starting an engine like this is very complex."

 

[ralphc1]

ok you could be onto something there. Yes it was going 1,100kmh base-down at loss of telemetry.

But....as a counterpoint....

Falcon9 1st-stage rockets re-enter literally every week base-down (engines first) and they come in supersonic too, and cross the sound barrier during their landing-burn and as far as I know those Merlin engines have never failed *ever* to relight despite the massive "upwards" airflow and they've done that literally hundreds of times. So that would indicate that, in general, relighting engines at supersonic speeds when you have a very fast "upwards" (relative) airflow of 700mph+ isn't a problem at all for SpaceX's other rockets.

Raptors have an extremely unusual and complex start-up procedure. Doesn't even have ignition torches in the combustion chamber at all! It's a highly complex engine and as far as I know, no other rocket engine in existence has a start-up procedure as complex as Raptor. So I will venture to suggest that there is a fundamental problem with Raptor's relighting and I do think sooner or later Elon Musk will comment on this and come up with a new modified version.

I can post a video tomorrow of Elon talking a bit about the Raptor's engine-lighting procedure. He is quite deliberately vague as it's SpaceX guarded info exactly what happens but it's very obvious it's unusual and complex and things need to work exactly right for engine ignition to happen reliably.

They were discussing that the Falcon 9 has a burn higher up to slow it down. That would be above the atmosphere so it would be easier to light. For some reason, they chose not to do that with Starship. Maybe fuel considerations. It does come in supersonic for the final but it used the Merlin engines fueled by kerosene where Starship uses Raptors fueled by natural gas. I know how difficult it is to light a cutting torch in windy conditions. Once it's lit the wind isn't a problem but getting it to light requires shelter from the wind.

I haven't seen anything where SpaceX explained the shutdown of the Raptors after separation. One side shut down before the other. Did some engines shut down before they were supposed to, did some run longer than they were supposed to or was that the way they were supposed to shut down? I also noticed that the last engines to shut down were the ones that tried to start according to the video they showed.

Did you notice the brown smoke at launch after the rocket reached some altitude? Was that something in an engine eroding? With 33 engines packed so tightly together, any problem with one engine can become a problem for many.

 

[Phlog]

For those of you who didn't see it this morning, Starship launched this morning and things were looking good for a while. All of the booster engines functioned at launch and until the ship separated. The booster engines restarted to turn the booster around to head to the planned soft landing in the ocean. Video from the booster as it was headed back to earth showed a grid fin moving. Just before the engines were supposed to restart for the slowdown, the one visible grid fin started moving around more and picture of the ground was moving as the booster wobbled. From the data shown, only one engine restarted and no more of the picture was seen. I assume they lost control and maybe used the destruct command.

The ship carried on around the Earth with a camera on the ship showing a tail fin and the side of the ship. The ship reached altitude and shut down the engines. After the engines were shut off, there appeared to be something coming out of the bottom. After a time the ship got into an area where they expected a loss of signal which was expected to last for about 30 minutes. They did regain contact with it in time for it to start re-entry. Some black pieces started to go by which many assumed were parts of the heat tiles. The fin could be seen glowing red as it moved to change the attitude of the ship. Then contact was lost and apparently the ship broke up over the Indian Ocean.

SpaceX likes to claim success even when missions don't go as planned because they collect data. If they lost all contact, there won't be much data to retrieve. I don't know when, if ever we will find out what happened.

It's not just a claim of success, it is an objective success. It is considered entirely normal in the rocket building business for 'unscheduled rapid disassembly' and space X has the best record in achieving success over time of any program in history that I can think of.

Elon bless.

 

[ralphc1]

It's not just a claim of success, it is an objective success. It is considered entirely normal in the rocket building business for 'unscheduled rapid disassembly' and space X has the best record in achieving success over time of any program in history that I can think of.

Elon bless.

I guess I was spoiled by watching missions that did what they were designed and scheduled to do. Mercury Gemini and Apollo had no failures that resulted in the loss of the rocket.

The Space Shuttle didn't have a failure until it's 25th mission. It's second on it's 113th. It flew 133 of 135 missions successfully.

 

[Phlog]

I guess I was spoiled by watching missions that did what they were designed and scheduled to do. Mercury Gemini and Apollo had no failures that resulted in the loss of the rocket.

The Space Shuttle didn't have a failure until it's 25th mission. It's second on it's 113th. It flew 133 of 135 missions successfully.

Yes, but they cost so much more and took so much longer. It's a different ethos, a silicone valley methodology of rapid iteration. I agree it looked different though for sure, although I like seeing the process.

 

[ralphc1]

Yes, but they cost so much more and took so much longer. It's a different ethos, a silicone valley methodology of rapid iteration. I agree it looked different though for sure, although I like seeing the process.

Took longer? May 25, 1961 President Kennedy made a speech saying that the US should put a man on the moon by the end of the decade and they did it 8 years later. Elon Musk announced plans to build the Mars Colonial Transporter in late 2012 and it's 11 years later without even one completed flight.

What goal has Musk ever accomplished in the time he said he would? Musk said they would land on Mars by 2018 and human landings by 2026.

https://www.bbc.com/news/business-36155591​

As far as the Silicone Valley methodology of rapid iteration, I can't say that I enjoyed basically being a Beta tester for computer operating systems. I remember this joke from back in the early days of computers.

Spoiler: Comparing computers to cars.

At a recent computer exposition, Bill Gates reportedly compared the computer industry with the auto industry and stated: “If General Motors had kept up with the technology like the computer industry has, we would all be driving $25.00 cars that got 1,000 miles to the gallon.”

In response to Bill’s comments, GM issued a press release stating: “If General Motors had developed technology like Microsoft, we would all be driving cars with the following characteristics:

1. For no reason whatsoever, your car would crash twice a day.
2. Every time they repainted the lines in the road, you would have to buy a new car.
3. Occasionally your car would die on the freeway for no reason. You would have to pull over to the side of the road, close all of the windows, shut off the car, restart it, and reopen the windows before you could continue. For some reason, you would simply accept this.
4. Occasionally, executing a maneuver such as a left turn would cause your car to shut down and refuse to restart, in which case you would have to reinstall the engine.
5. Macintosh would make a car that was powered by the sun, was reliable, five times as fast and twice as easy to drive – but would run on only five percent of the roads.
6. The oil, water temperature, and alternator warning lights would all be replaced by a single “General Protection Fault” warning light that would only come on when it is too late to fix the problem.
7. The airbag system would ask “Are you sure?” before deploying.
8. Occasionally, for no reason whatsoever, your car would lock you out and refuse to let you in until you simultaneously lifted the door handle, turned the key and grabbed hold of the radio antenna.
9. Every time GM introduced a new car, car buyers would have to learn to drive all over again because none of the controls would operate in the same manner as the old car.
10. You’d have to press the “Start” button to turn the engine off.
11. The resale value would drop 75% just driving off the lot and go to nothing in 2 years. Forget trade ins.
12. When you install a new set of tires you would have to replace multiple other accessories or the vehicle wouldn't operate correctly.

 

[ralphc1]

Did the booster soft landing fail because it ran out of oxygen? A poster on Youtube noticed that the oxygen level indicator on the video appears to be on the empty mark just as the 12 engines shut down after the flip maneuver.
Who knows how accurate that is. Look at 3:40 on the flight test clock.

 

[Phlog]

Took longer? May 25, 1961 President Kennedy made a speech saying that the US should put a man on the moon by the end of the decade and they did it 8 years later. Elon Musk announced plans to build the Mars Colonial Transporter in late 2012 and it's 11 years later without even one completed flight.

What goal has Musk ever accomplished in the time he said he would? Musk said they would land on Mars by 2018 and human landings by 2026.

https://www.bbc.com/news/business-36155591​

As far as the Silicone Valley methodology of rapid iteration, I can't say that I enjoyed basically being a Beta tester for computer operating systems. I remember this joke from back in the early days of computers.

So that's a good point, but the moon shot was one mission and it was a state that achieved it by applying 2.5% GDP for ten years. Like 5.86 trillion dollars if it were done today. The entirety of space Xs achievements so far has been less than that. Not one mission but revolutionising transport to space.

Musk overestimates his goals. Sure. I don't think that's relevant when judging his success. Unless you're judging the success of his predictions.

And yes, iterative design has it's flaws, but it's proven to be more efficient than other models. Is what it is!

 

[ralphc1]

So that's a good point, but the moon shot was one mission and it was a state that achieved it by applying 2.5% GDP for ten years. Like 5.86 trillion dollars if it were done today. The entirety of space Xs achievements so far has been less than that. Not one mission but revolutionising transport to space.

Musk overestimates his goals. Sure. I don't think that's relevant when judging his success. Unless you're judging the success of his predictions.

And yes, iterative design has it's flaws, but it's proven to be more efficient than other models. Is what it is!

While trial and error in the computer industry was accepted as a business model, it is less desirable in the transportation industry. If I'm going to travel in a land vehicle, almost making it to the destination but not quite would not be considered a successful trip but not a disaster. Doing the same in a boat or an airplane could end in disaster. Sending large objects into the air hoping to be able to control them but losing control could end in disaster if the pieces land on some populated area.

Just to get one trip to the moon is going to require several launches of Starship to transfer fuel.

 

[Phlog]

While trial and error in the computer industry was accepted as a business model, it is less desirable in the transportation industry. If I'm going to travel in a land vehicle, almost making it to the destination but not quite would not be considered a successful trip but not a disaster. Doing the same in a boat or an airplane could end in disaster. Sending large objects into the air hoping to be able to control them but losing control could end in disaster if the pieces land on some populated area.

Just to get one trip to the moon is going to require several launches of Starship to transfer fuel.

There was plenty of trial and error in the shuttle program, you just didn't see it. The critical design is done before people are onboard. Space X already has a better safety record than any one else re getting things to space. Cheaper too.

 

[ralphc1]

There was plenty of trial and error in the shuttle program, you just didn't see it. The critical design is done before people are onboard. Space X already has a better safety record than any one else re getting things to space. Cheaper too.

What examples of trial and error were there in the shuttle program?

 

[ralphc1]

I have been waiting for the Common Sense Skeptic to present his analysis of the Starship launch. He has good connections and sources and usually breaks things down very well. He used SpaceX's own pre flight timeline to compare it to the actual flight. He mentions the smoke on takeoff that suggests a less than ideal mixture or engines consuming themselves. If the mixture was rich it should have used more CH4 than O2 but the data showed the O2 level being lower than the CH4.

He points out the very low levels of O2 and CH4 in the booster data as the engines shut down in a rather strange pattern after the flip maneuver. Did the Booster run out of O2 and that prevented it relighting? If it ran out of oxygen, that could be a big problem. If the tanks were full at takeoff and that wasn't enough to supply the return burn, how do they increase that? If they make the booster larger to hold more oxygen, it adds weight requiring more power which requires more fuel and oxygen. There was no payload on the Starship so it was lighter than it will be on a real mission.

He points out that the payload bay opened well after it was announced that the command had been given. He pointed out that it likely didn't open all of the way as the hydraulic cylinders had a lot more stroke left. He also points out that the cameras never showed it closing either.

As far as the O2 transfer from the header tank, he points out that the O2 level in the main tank never showed any increase.

There was also something venting from the Starship. I don't know how many of these successes SpaceX can afford.