SpaceX Starship megarocket launches on 2nd-ever test flight, but explodes in 'rapid unscheduled disassembly'

[Admin]

SpaceX's next-generation Starship megarocket launched on its second-ever test flight today, but explodes in a "rapid unscheduled disassembly." (Nov. 18)

SpaceX Starship megarocket launches on 2nd-ever test flight, but explodes in 'rapid unscheduled disassembly' : Read more

 

[Unclear Engineer]

Watched it live. Really great to see all 33 Raptor engines burning all the way to stage separation, and all 6 on StarShip burn as well, after the stresses of boosted launch and stage separation by the "hot" process.

It was a surprise to see Starship fail to achieve its intended engine cutoff point before exploding - it had burned well for almost all of its intended time. I hope SpaceX got the needed telemetry to find out why that happened. But, it seems that they were not getting telemetry at that point, and it took a while for them to conclude that the Flight Termination System had activated to destroy StarShip.

It will also be interesting to see how the launch pad held up. There is some chatter elsewhere about denting to one of the tanks in the tank farm near the pad.

Hoping for a follow-up article from Space.com soon that tells us what is actually known.

And hoping that the FAA did not see anything that it wants to "investigate" for another 7 months.

 

[TEAMSWITCHER]

Watched it live. Really great to see all 33 Raptor engines burning all the way to stage separation, and all 6 on StarShip burn as well, after the stresses of boosted launch and stage separation by the "hot" process.

It was a surprise to see Starship fail to achieve its intended engine cutoff point before exploding - it had burned well for almost all of its intended time. I hope SpaceX got the needed telemetry to find out why that happened. But, it seems that they were not getting telemetry at that point, and it took a while for them to conclude that the Flight Termination System had activated to destroy StarShip.

It will also be interesting to see how the launch pad held up. There is some chatter elsewhere about denting to one of the tanks in the tank farm near the pad.

Hoping for a follow-up article from Space.com soon that tells us what is actually known.

And hoping that the FAA did not see anything that it wants to "investigate" for another 7 months.

Don't blame the FAA for doing their job. The first launch was a complete failure, a mini environmental catastrophe followed by complete loss of flight control, and a flight termination system that basically failed.
This second test was better, but also rather disappointing. The Artemis schedule is as slow as can be, but at this pace, SpaceX meeting that slowed down schedule is seriously in doubt. The problem is that SpaceX is still trying to get the EASY part working. There are already pictures showing severe heat shield loss just a few minutes after liftoff. That heatshield would NEVER have survived a re-enty. SpaceX isn't close with Starship.. In fact, they are dealing with all the same problems NASA had with the Space Shuttle, and some new ones too.

 

[Wolfshadw]

Please keep commentary non-aggressive and on topic.

Wolfshadw
Moderator

 

[Hypocee]

Almost all of this is good but I'm disappointed by "The Starship upper stage continued flying for a short time after stage separation." The upper stage flew steadily and on-trajectory for almost its entire planned burn, and it's likely we'll find that its failure was related to some preparation for engine shutdown in the previously untestable flight regime outside the atmosphere.

 

[Hypocee]

Don't blame the FAA for doing their job. The first launch was a regulatory failure, a mini environmental catastrophe followed by separation failure after excellent and robust flight control, and a flight termination system that basically failed.

FTFY a bit but yes, we can think two things at one time. The SpaceX team is doing excellent and exciting work, and also they should never have been permitted to launch the heaviest rocket in history without a shock and erosion suppression system in place. Every commentator foresaw the demolition of the pad, and the issues it caused on the rocket and on the ground, months in advance. "A fine is a price"; the real way you make an irresponsible billionaire think twice next time is to step in and give him a few months' time out. That's what the FAA correctly did.

The problem is that SpaceX is still trying to get the EASY part working. There are already pictures showing severe heat shield loss just a few minutes after liftoff. That heatshield would NEVER have survived a re-enty. SpaceX isn't close with Starship.. In fact, they are dealing with all the same problems NASA had with the Space Shuttle, and some new ones too.

Nah. The whole point of the bellyflop and cylindrical shape is that Starship is much less dense than the Shuttle and hits at 90 degrees rather than 40 with a huge frontal shield area. This (literally, I think) exponentially reduces both the aerodynamic and thermal loads taken. There's always some degree of damage that would lead to failure in reentry, and maybe that would have been true on this flight, but Starship is incomparably more damage tolerant than the Shuttle, and overall much less complex.

Loss of thermal tiles would certainly impact the system's rapid reusability, but that's a future concern. Seeing where and how tiles stayed on or came off in unpredictable conditions was another purpose of doing an empirical test like this. SpaceX is indeed currently "trying to get the easy part working"...but they're doing so after nailing down the hard parts: Dynamically maintaining and maneuvering in the bellyflop, and relighting liquid engines under lateral g-loading. And, of course, inverted-pendulum landing, but as noted in the article they've made that routine at this point. Provided the engines turn on and don't pop, it's just different numbers in the same equations.

 

[DrRaviSharma]

Still after Saturn V and one Artemis ULA launch, this is the greatest milestone achieved by humanity.
Next couple of attempts and we space human flight enthusiasts and participants will see the reliability, repeatability and confidence levels (statistically) improve towards its first goal - to land humans from lunar orbit to Moon and bring them back to orbiting station around Moon. Then more cislunar and lunar landings and one can see this as a Lunar workhorse back and forth to Earth and eventually venture deeper some day say 5 years + by extrapolation towards Mars.
Best to Spirit of SpaceX, NASA, FAA and Elon.
Ravi
(Dr. Ravi Sharma, Ph.D. USA)
NASA Apollo Achievement Award
ISRO Distinguished Service Awards
Former MTS NASA HQ MSEB Apollo time frame
Former Scientific Secretary ISRO HQ
Ontolog Board of Trustees
Particle and Space Physics
Senior Enterprise Architect
SAE Fuel Cell Tech Committee voting member for 20 years.

 

[Trainer Paul]

Great Job !
Watched the launch from my home, and also on line.
It was amazing to see all engines burning like a LED light in the night. Great Job.

Was amazed about a shorter lift off time, saving fuel, less issues with the pad, and to save water.

Was surprised about the use of using water to protect the pad during lift off. Great idea.
(Pad drains would be nice, to recover the water to be reused, pumped back to the water tank)
* Note : the pad itself seems to be a cluttered, not set in a open area like N.A.S.A. used to do, tanks and equipment isn't far away and brings a little concern to my mind, I would assume this is only a test site and those issues will be taken care of in the future in a different area.

Separation is a little puzzling to me, as I would think the 1st stage would stay in a vertical position for a longer period of time to absorb the trust of the Second Stage, and then turn. Avoiding trust from the 2nd stage in a horizontal position. This would also allow slowing speeds of the 1st stage before a turn. The view in the sky from the first stage after separation was truly something I will never forget. (RUD)

Loss of communication ?
Could the separation be part of this failure as they seemed to happen not long after each other? In some ways I believe it might have been part of the plan, built to not last but one trip, recovery and reuse with salt water not the best options or cost effective for reuse. (Recommended; a black box type information gathering for on board data collection and recovery if not already being done.)

Without failure we don't learn, we all must fall before we walk. I can say this launch was truly amazing. 100% better than the last attempt.

Keep up the good work and dedication.

 

[billslugg]

Cannot allow the first stage to slow down. Any amount of slowing at stage separation puts the booster fuel at the top of the tank where it cannot get to the suction pipes supplying the engines.
Hot staging requires sufficient engine power on the booster stage to offset the thrust on it by stage separation. They only had three engines, throttled down, on the booster. They may need more power to prevent sloshing.

 

[DrRaviSharma]

Great Job !
Watched the launch from my home, and also on line.
It was amazing to see all engines burning like a LED light in the night. Great Job.

Was amazed about a shorter lift off time, saving fuel, less issues with the pad, and to save water.

Was surprised about the use of using water to protect the pad during lift off. Great idea.
(Pad drains would be nice, to recover the water to be reused, pumped back to the water tank)
* Note : the pad itself seems to be a cluttered, not set in a open area like N.A.S.A. used to do, tanks and equipment isn't far away and brings a little concern to my mind, I would assume this is only a test site and those issues will be taken care of in the future in a different area.

Separation is a little puzzling to me, as I would think the 1st stage would stay in a vertical position for a longer period of time to absorb the trust of the Second Stage, and then turn. Avoiding trust from the 2nd stage in a horizontal position. This would also allow slowing speeds of the 1st stage before a turn. The view in the sky from the first stage after separation was truly something I will never forget. (RUD)

Loss of communication ?
Could the separation be part of this failure as they seemed to happen not long after each other? In some ways I believe it might have been part of the plan, built to not last but one trip, recovery and reuse with salt water not the best options or cost effective for reuse. (Recommended; a black box type information gathering for on board data collection and recovery if not already being done.)

Without failure we don't learn, we all must fall before we walk. I can say this launch was truly amazing. 100% better than the last attempt.

Keep up the good work and dedication.

appreciate your analysis

 

[DrRaviSharma]

Cannot allow the first stage to slow down. Any amount of slowing at stage separation puts the booster fuel at the top of the tank where it cannot get to the suction pipes supplying the engines.
Hot staging requires sufficient engine power on the booster stage to offset the thrust on it by stage separation. They only had three engines, throttled down, on the booster. They may need more power to prevent sloshing.

You may be right, thanks.

 

[Trainer Paul]

Cannot allow the first stage to slow down. Any amount of slowing at stage separation puts the booster fuel at the top of the tank where it cannot get to the suction pipes supplying the engines.
Hot staging requires sufficient engine power on the booster stage to offset the thrust on it by stage separation. They only had three engines, throttled down, on the booster. They may need more power to prevent sloshing.

I agree not sure at where the point is when the first stage is no longer pushing, I would assume force meters would be installed to know when separation would de ideal and automatic unlock would take place on its own or locked when only being forced downward any upwards force automatically unlocks mechanically like a check valve. The slow down I was referring to was after separation before the turn to save the first stage keeping it upright until 2nd stage is far away.

 

[billslugg]

The first stage is not supposed to stop pushing. It is supposed to be under constant acceleration even as separaton takes place. That did not happen here as can be seen in the telemetry data, it lost about 80 m/s in about 2 seconds as separation occurred. The booster was not pushing hard enough and Starship pushed it backwards, sloshing the fuel.
With three engines at 50%, even as it flips around for reentry burn it never stops being pushed by the engines. The flip was done but the other engines did not come on, it just blew up.

 

[Macro]

Lovely but lets imagine that is any other country in the world sending gigantic rocket overfying all over nations and ready to explode anytime ! Not your ordinary weather ballon.

 

[billslugg]

It does not overfly any nation but the US until it is in space. Any nation is permitted to fly over their own country until into space then anyone can fly over anyone. There are treaties about this.

 

[Trainer Paul]

You may be right, thanks.

Talking about the first stage, after separation, moving into recovery. At some point the first stage fuel could be cut off by rotation and possibly gravity.
Wonder what the plan was for this ?
Cut off and Reignition? Vent to make sure it's liquid fuel and not gas before reignition ?

Worst case is feeding engines gas and not liquid fuel.

The first stage is not supposed to stop pushing. It is supposed to be under constant acceleration even as separaton takes place. That did not happen here as can be seen in the telemetry data, it lost about 80 m/s in about 2 seconds as separation occurred. The booster was not pushing hard enough and Starship pushed it backwards, sloshing the fuel.
With three engines at 50%, even as it flips around for reentry burn it never stops being pushed by the engines. The flip was done but the other engines did not come on, it just blew up.

I reviewed the replay today, you are most definitely correct. The 2nd stage was for the most part dragging the first stage before separation, actually surprised it unlocked.
This would indeed cause the fuel to be an issue. As mention before, some type of indication between 1st and second stage seems to be needed to indicate the force or weight being pushed or pulled between stages to get a perfect separation and to conserve fuel.

Not sure how much of a communication delay they have, it might have to be a trigger on board 2nd stage for unlocking using the indicators. Weight load sensors between stages comes to mind here ?

The indicators if installed would also allow the team to know with payload on board if too much stress is being applied on liftoff and a slower or faster liftoff is needed.

Being a second test, it's clear that advancements have definitely been achieved.

 

[Unclear Engineer]

The real crux of the issue is the probability that some parts of something launched will make it through re-entry and hit the ground where it might hurt people. From orbit, there is the burnup during re-entry and the intentional selection of re-entry by deorbiting systems to provide risk reduction. But, those aren't factors for failures during the ascent phase.

So, the ascent phase, where there is not yet enough altitude or speed to reach orbit, is a crucial part of the risk down-range. That is why most nations launch from coastal areas facing roughly eastward. That is why China evacuates some towns when it launches from inland sites. That is why Japan gets peeved about launches from North Korea.

So, what does the ascent phase go over when StarShip is launched from Texas over the Gulf of Mexico? We know the 1st stage is going to try to come back to the starting point, but where is the 2nd stage when it reaches orbital velocity and altitude? Does any location of a RUD potentially send debris onto any of the islands that are not part of the U.S.?

 

[billslugg]

Yes, there might be some "pushing or shoving" going on between the two stages at separation, but under no circumstances, ever, should either stage experience decelleration. Both stages under positive accelleration all the time.

 

[Unclear Engineer]

I don't see how the second stage could "pill" the first stage before separation. The engine exhaust from the second stage is diverted by the first stage through the adapter ring and vented mostly outward, not rearward.

And, even if the engines in the second stage were capable of "pulling" the first stage, the fuel in the first stage tanks does not know the difference. All it sees is the acceleration of the tank walls around it, which then is imparted to the fuel in the tank.

 

[billslugg]

Right, the second stage is not supposed to "pull" on the first stage. The locks are supposed to be unlocked before the second stage ignites. I was responding to this statement in post #16:

"As mention before, some type of indication between 1st and second stage seems to be needed to indicate the force or weight being pushed or pulled between stages to get a perfect separation and to conserve fuel."

 

[Classical Motion]

Accelerometers on the stages and a simple 8 bit microprocessor can easily ratio and separate at the right instant. And I am sure this has been done. Redundantly and with superior hardware.

Like everything else, it's probably a combo of causes.

 

[billslugg]

The cause was that three engines at half throttle on the booster is insufficient to maintain positive acceleration on the booster when pushed backwards by the igniting second stage. They might decide to make a new interstage with larger vent opening or they might decide to simply raise the thrust level on the booster during separation.

 

[Classical Motion]

Just put AGC on booster throttle. Any decel sensed is rebuffed with acc. I would think this kind of control would have been done years ago. If you can throttle the stage. Maybe the throttle has slow response?

I know nothing about it. What did the first guy to launch stages do? How long was it before they realized this timing need? Surely this is not a new problem.

Maybe I am entirely wrong and we are just learning to tune our launches.

Edit:

I think they'll get it. His returning boosters failed at first. Now they're common. I was surprised at their usage.

Maybe rocket science isn't open source. And not that common.

 

[billslugg]

Booster ullage has not been such a problem in the past because first stages were generally run dry, they did not need fuel for a return. No one cared if the explosive bolts and solid rocket boosters pushed the first stage backwards a bit.

Ullage in liquid fueled second stages was a not a problem at separation since the tank was full. There was a problem later on since many of them had to restart to trim the orbit. But when releasing the third stage, no one cared about ullage in the second stage since it would burn up on reentry.

Musk did not want to use conventional stage separation due to weight and cost of the additional rocket motors or springs or whatever. He tried to spin them apart the first launch and that didn't go very well.

Hot staging is very simple, requires no tiny rocket motors, no control loops, much cheaper. Very risky though since the lit engines can damage the booster and themselves. This is why no one ever tried it before. Hot staging requires precise timing, a set of booster engines that can be throttled, a vent ring and damage resistant second stage engines. Too risky for NASA.

 

[Unclear Engineer]

SpaceX doesn't use hot staging for its Falcon 9. So, at least for that sized vehicle, they have developed the alternative into a very reliable system.

So, I am wondering if there is any reason they can't do the same for Super Heavy + Star Ship.

Certainly, there are much larger forces at work in the bigger vehicle. And, I wonder about the effects on the fuel and oxidized liquid free surfaces inside their tanks when the 1st stage goes through its turn-back maneuver.

It occurs to me that SpaceX may have decided to go to hot staging only for these early tests where they have no intention of reusing the 1st stage and are putting a high priority on getting hot re-entry data for the second stage. They may be thinking about going back to coast separation after they get to a point where they really want to reuse everything. Or, maybe they will find that they can arrange to reuse everything after hot staging, Remember, it isn't just resuse - it is rapid reuse that SpaceX is designing for.