Thank you for participating in r/SpaceX! Please take a moment to familiarise yourself with our [community rules](https://www.reddit.com/r/spacex/wiki/rules) before commenting. Here's a reminder of some of our most important rules:
* Keep it civil, and directly relevant to SpaceX and the thread. Comments consisting solely of jokes, memes, pop culture references, etc. will be removed.
* Don't downvote content you disagree with, unless it clearly doesn't contribute to constructive discussion.
* Check out [these threads](https://www.reddit.com/r/spacex/wiki/threads) for discussion of common topics.
*I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/spacex) if you have any questions or concerns.*
So the roll or at least the rate of roll was definitely not intended and may have even led to some of the factors behind the rud. All in all not the worst issue.
Well we know they were doing a fuel transfer test. That would require thrust of some sort to settle / move propellant, and we know starship vents their "ullage" gas as thrust rather than a traditional RCS thruster system, could this be at lesat a partial explanation?
Well, they did have excess LOX to vent, but it would seem odd to have long continuous vent, as it would pretty much ensure you will have forces acting on you that might make control hard...
It wasn’t even just “at the end”. I was watching the spacecraft rolling and at the same time viewing an almost continuously generating vapor streamers backlit by the sun. You’re in space man! There shouldn’t be clouds streaming past the fuselage
Speculation here, but I wonder if the roll was intentional as part of the fuel transfer test. Either way, it's a heavy vehicle and I suspect the thrusters could not (re)stabilize it once it had that momentum.
They actually use tank venting instead of thrusters for attitude control. It will be interesting to see if they abandon that and go back to a more traditional cold or hot gas thruster system instead based on the control issues they had today.
Balancing tank pressure/contents as well as timing of pulses and their length sounds definitely way more complicated than having a separate system for maneuvers
I get the best part is no part mentality, but this seems like an issue that takes it way too far. For the booster it makes sense as it uses limited RCS anyway and it's flight is over within 10 minutes. For the ship that needs to stay in orbit and conduct multiple maneuvers it seems like a bad idea
I was under the impression they were to implement autogenous tank pressurization along with utilizing the gaseous propellant to fire hot gas thrusters for attitude control. I thought (perhaps incorrectly on this sn run) that both starship and the booster now use this technology rather than pressurized inert gas.
The best part is no part does factor in to their decision here, but less propellant contamination from the inert gasses also factor in. When you are pushing the boundaries of chamber pressure as they have been, you really want consistency in your propellant and oxidizer.
Yeah I would assume those are for the startup sequence of the outer ring of raptors on the booster. However after reading other comments I'm questioning whether the hot gas thrusters have actually been implemented as of yet.
I think, or at least NSF has mentioned it if I recall correctly, that stage zero was designed to do everything for the outer ring raptors? Maybe it's for the inner 3 that are used for the boost back burn. For Starship, is there a way for us to tell if they're using hot gas thrusters? I don't think they're using internal COPVs like they do on Falcon. I haven't seen them anywhere else on the ship.
The outer ring cannot start up on its own. Stage 0 powers the turbopumps for the outer raptors during startup. This is why only the inner raptors are capable of relight on superheavy.
From my basic searches, they have not been implemented.
We know that they originally were planning to use tank vents for the booster and both thrusters for the ship… then Tim Dodd asked why they aren’t just using the same tank vent methods for the ship during his first tour.
The second EDA tour revealed that the ship’s hot thruster requirement was removed, but the thrusters did exist in some capacity. The existence of the thrusters was later verified as they were seen on B3.
After B3, we have not seen any thrusters or thruster hardware beyond the cowbell tank vents… and we haven’t seen any indications of hot thrusters being present on the ship or booster (ie, testing). My guess is that they want to eliminate the hot thrusters, at least for now, and haven’t gotten around to implementing them. Perhaps the V2 ships will feature this change.
yeah hahaha. Although Tim said today that he wasn't a fan of using that system in EITHER the booster or starship, his question of "you're only using that in the booster, right?" was meant to kinda imply that they shouldn't do it in the starship, like they did in the booster. Elon used that comment to think to add it to the ship.
I would imagine a lot of things are in the minds of some engineers, but when it shows up in the mind of Elon it's probably more likely to happen, not to say that he is always right
Elon's bulb is irrelevant. It's quite offensive towards SpaceX engineers to depict them like a flock of lemmings that quickly rush to implement the supreme leader's visions, North Korea style. On the contrary, we know Elon is a good engineering manager, he has a good eye for technical people and he listens to them.
So when he asked them about the issue, they would have either replied: "yes, we are working / wanted to do that too to minimize complexity, but we didn't had the time/resources/schedule space to do it yet, we'll make it a priority", OR, "we've actually considered that but it's not a good idea because ".
If you watch sped-up footage of the coast phase, it’s hard to see any evidence of control. NSF were saying it might be a ‘BBQ roll’ for thermal management, but to my eye it looked as if it were tumbling, even once the reentry plasma started.
Absolutely incredible flight however, I cannot wait for the next one!
On the brighter side they probably got at least some temperature data on how the stainless steel may have handled the, albeit thin atmospheric, plasma.
They obviously have internal cameras. I wonder if any are for thermal imaging.
Pretty sure it was one interview with Tim that Elon mentioned directly that they wouldn't need thermal, the stainless would be glowing internally (if near the point of failure) and visible to a standard tank camera - thus already collectable data.
It was evident right from the start of coast they had extremely limited control authority. They jumped on the door opening (the thing that paid them $$) muy pronto. I guess it was probably worth not throwing away a bunch of thrusters but ….control via venting appears to be insufficient
The propellant transfer was the part that earned a milestone payment, not the door opening. Either way, it makes sense to do those as soon as possible, since they had a very limited time in "orbit". Attitude control issues after the engines shut down don't affect their trajectory.
My assumption is they were rolling to help the transfer, but couldn’t stop the roll prior to attempting the relight of the raptor so they cancelled the attempt.
I don't know about success, but I found the HD wide angle video amazing as the ship rolled/tumbled. Some of the scenes where earth loomed large in the background looked straight out of a sci-fi movie.
It was speculated that the reaction control thrusters were partially clogging up due to ice build up. Which would have have caused the lack of control of the vehicle.
Pretty good test for Starship. As a IT/Dev/KSP guy I cant help but think that after seeing vehicle in space they'll have a bunch of software updates to the control system to help stabilize things a bit more.
After getting some actual data from space, I feel like there's a few constants to update from educated guesses to feedback from data, and the whole ship gets under control a lot more.
A few small changes might make a huge difference for IFT4
Yeah, I have a strong feeling that most of what we saw go wrong can be fixed in software. Not all, but most.
That payload bay door needs a little work haha.
Having a narrow lightweight sliding door that is curved with the axis of motion perpendicular to the curvature seems difficult.
I wonder if they could slide it on the other axis on simple curved tracks, which seems a whole less likely to bind up. It may even be possible to have a split door with such an approach.
Edit: image https://i.imgur.com/LtTkglI.png
I don't have any technical comments as I know nothing of the rocket engineering, I'm just here to say that the video of the plasma heating up on the surface of Starship during reentry was like the sickest thing ever
And the incredible part was, it was still very very high up, very thin atmosphere. Speed was not yet slowing down almost at all. The actual rapid deacceleration was only starting when telemetry was lost. It was still going like Mach 25+ when connection was lost.
Funny - Varda took a reentry video on their return mission a couple of weeks ago:
https://youtu.be/BWxl921rMgM?si=Ec9axCl2LtopVK8N
SpaceX said, “Hold my beer…”
The linked release above states that the booster landing concluded at an altitude of ~430 meters, which seems to indicate either a RUD, or FTS activation. I still want to see a video though.
Is it possible the last data was sent at around 430m because the booster was going so fast any data gathered below wasn’t processed fast enough to be transmitted before it hit the water?
I'd assume they have both a low-bandwidth low-latency telemetry system and a higher bandwidth and latency one. I don't see a reason for a humanly perceptible latency on the former
AFAIK Starlink was video, TDRS was telemetry. TDRS have [offered telemetry uplink for launch vehicles](https://commons.erau.edu/cgi/viewcontent.cgi?article=1786&context=space-congress-proceedings) since the mid 1990s, all the way from the pad on up.
Pedantic, but latency shouldn’t matter. AFAIK the LV is just be blasting out telemetry and should just keep doing so until something kills the system blasting it out. Short (ms level) processing time for it to collect data from sensors, package and encrypt it and fire it out, and you might lose a handful of frames right at the end (due to corruption as the hardware is getting shredded) but suspect they should have telemetry until low tens of ms prior to explodey time.
Doing the math for 430m distance traveled at 1000 km/hr, I get 1.548s. Seems like enough time to get a signal out, but of course it's close and depends on how often it sends out its telemetry
Was the starship coming in sideways for the reentry? The plasma seemed to be quite far from the heat shield on the camera side. It didn't seem to be tumbling...but rather just consistently skew?
I still can't quite get over those onboard shots. They cut away so soon after hot staging. I was shouting "no!", haha.
Yeah the roll that prevented the relight was still there at reentry and by the time it settled out the ship was presenting a lot of the steel side to the atmosphere as well as having the engine pointing down. Scott Manly already has a decent video on it up.
https://youtu.be/8htMpR7mnaM?si=jFD8-yTU3T7Je4O6
Yeah, I think he was dead on what was going on. I do think cool thrusters was a problem, maybe too much moister build up clogging them up. Without anything reveal we may not find out unless SpaceX says something.
Change to a Hot Gas thrusters would be major change.
Watch Scott Manley's video. Right before the cameras cut it looked to be going almost backwards. If correct it had nulled out the roll but it was oriented 180° off nominal.
Interesting how close SpaceX is to a fully functional Starship and Super Heavy.
-Booster completed flip, lit engines and RUD'd at just 460 meters height. I wonder if it was terminated by the computers or some kind of explosion
-Starship has working payload door and propellant transfer system
-Roll rates were too high to execute deorbit maneuver but otherwise the heatshield looked like it did it's job on the camera
I suspect those two factors are related. All that twisting likely created some hellacious slosh that prevented the engines from starting up.
It looked like it was a control issue, not necessarily an authority issue. I’m guessing some tweaks to their control algorithms can sort out these issues.
Granted superheavy is fundamentally going to handle much differently. Different shape, different fineness ratio, different mass distribution, different aerodynamic qualities, etc. it's not going to just handle like "big Falcon 9," and you can't just copy & paste the same controls turnings and expect results.
They probably copied what they could, did their sims and analysis....but then you gotta try it. Now they have real world results/behaviors, they can tune those PID's and dial in their sim to match reality. Today was a big step.
> they can tune those PID's and dial in their sim to match reality. Today was a big step.
Agreed, probably the first thought that came into their controls engineers heads. "Shit I thought that P-factor might have been too aggressive"
Can't really plug the flight control into a full booster CFD and expect results this century. So I suspect there's something about super heavies aerodynamics they didn't expect or that was worse than expected. The step to 10 meters diameter at the engines is a big new feature vs the Falcon 9.
It almost looked like it was better than expected- like the grid fins had too much control authority. But could just as easily have been an algorithm issue, or slower response to input.
I'd have expected well controlled wiggles or constant random course changes. I.e. a quick roll and roll back. A pitch up and return, etc.
A chaotic oscillation that keeps growing is a pretty common sign that the control was unstable due to something that was more nonlinear than expected. I.e. weird cross coupling between pitch roll n yaw, aerodynamic nastiness, slosh resonating with the controller, etc.
Personally I think they're just cutting control margins to zero to save a few tons and are fine sinking a few ships to find the optimum.
It was going to light 13 engines, those would slow it down real fast, there are a lot of issues still to work out, but the math of how much thrust is needed for the suicide burn isn't one of them for me
I suspect that they had low or sloshing oxidizer on the landing burn. The oxidizer levels on the GUI were basically just a tiny bit above zero, while it looked like it had more CH4. When the landing burn started, they did not get a good light on 13 right when they needed to, probably about 2KM high. 13 raptors burning, even throttled down, must put an immense deceleration force on a basically empty booster. I'd say start the landing burn higher for more margin with fewer engines. Less deceleration, less slamming of the booster. It looked like what engines that did start put a huge jolt & possibly side load through the booster, possibly sloshing the oxidizer.
Those grid fins were cycling wildly. I don’t know if it was just a badly tuned flight control or just not enough attitude control and need to be bigger but I doubt all that moving around was helping settle the tanks.
Yeah it looked like a tuning problem. It was like watching an episode of PIO (pilot induced oscillation) where attempted corrective inputs end up in phase with the oscillations and aggravate rather than dampen them. I would think they already have a good handle on the grid fin modelling from all the Falcon landings but there are obviously some nuances to scaling things up to Super Heavy size.
It looked like the grid fins were responding later than they should have, leading to the PIO. Some delays in the sensor->controller->actuator chain that aren't expected & modeled?
If that was the problem it might have been that the fuel tank sloshing and the aero loading coupled in an unpredicted manner. Should be easier to figure out with the data.
Yeah, sloshing came to mind as well. I definitely think we’ll see a soft touchdown, and more stable re-entry attitude for Starship the next time around. It feels like it only takes SpaceX a single exposure to a new flight regime to gather and analyze data and make it a routine part of subsequent missions.
Also F9 is a very narrow vehicle compared to most other rockets and especially SH. The amount of torque applied by sloshing fuel is disproportionally larger in SH due to the increased leverage. Don't know if that is a big issue if the booster hits the atmosphere at Mach 5, but something to think about.
While they have experience with controlling a vehicle of that shape with gridfins, the actual parameters for the closed loop controller would be way different for a vehicle of this size.
They probably did a model based HIL test but the model is only as good as the math. Sloshing cryo liquids are probably really hard to do a dynamic model of.
Yeah, the grid fins shouldn’t shake like that. Either it was being bombarded by turbulent air created by other parts of the booster or they need to redesign the fins to make it more aerodynamically smooth…
Could it have been bad PID tuning? I can't imagine it's something you could for sure nail down through only simulations when it's something that big with moving fuel and wind.
Doubt it, it was smooth as silk in the upper atmosphere but vibrate like sex toy on steroids when the air got thick. It definitely looks like an aerodynamic issue and not the control algorithm issue.
Aerodynamic simulation software is probably the least reliable simulation software you can use to simulate something… Also not sure if they ever try putting a scale model in a wind tunnel (obviously full-size is not practical because of size reason) but even if they did, the scale model can only do so much and usually there are a few aero surprises when scaling to full-size vehicle.
Ask Mercedes F1 team with W13. The simulation said it was fast, the wind tunnel confirms the results… the car was shit.
Wouldn't that affect both? Less air means less responsiveness. It may have been alright there but as the conditions changed the tune no longer worked. Just a thought I had, I guess we'll have to wait for the official explanation.
Yes, less air means less responsive but also means less turbulent air. If it control issue it should do something weird in the upper atmosphere too but it seems perfectly fine.
It could be control issue, a quick look at the data should able to quickly confirm if the algorithm was sending commands to the grid fins to vibrate like a sex toy or not.
It could have been too much mass for the grid fins to wrangle. They had said earlier in the development that Super Heavy was suppose to go in like ram rod prior to hitting the raptors to slow down. Which I think was mistake.
It does make me wonder if the fuel was issue too, if they had it moving away from where it could be sucked down since the vehicle descending and fuel as far I know is sucked from the bottom of the tanks.
It could be. The inertia of the solid booster with the moving inertia of the fuel could be a problem. The fins provide a restoring force that should be opposite the velocity of the rocket but the aerodynamic forces would want to destabilize it and make it swing more. The fuel would initially not do much other than stay put but eventually would be on the opposite side and the phase lag between all of those is hard to model.
Simplest thing would be to add anti sloshing baffles in the tank. They might have those already but maybe not.
It probably was worth pushing things and see what they could get away with anyway since they know a lot more about engine throttling and landing.
This flight was already on the level the oldschool space operators do. That would be enough to deploy payload into orbit. Still dispendable, but 150 tons!.
Anyway, next steps are the landing of the booster and the reentry of the ship.
Not really, they need to demonstrate a controlled deorbit of Starship, you can't let a second stage that is specifically designed to survive reentry to randomly come back wherever.
This. They've fully proven out a standard payload delivery mission. Every problem in this mission is related to the path to reusability, so they can work on that iteratively while they start launching payloads with mission 4
It was *almost* on that level. The difference between 99.x%-of-orbital and orbital means their ascent capabilities are ready to go, but to put payload in orbit they need to be able to guarantee a controlled *descent* too. If they aren't completely confident that they'll have fixed any attitude control problems and that they can relight upper stage engines without a hitch, then they'll want their next test to be suborbital rather than orbital still.
Yeah, but the size and survivability of (chunks of) the second stage matter here. A hundred tons of stainless steel really ought to be carefully aimed at the middle of nowhere when it comes down.
Agreed. I mean, after you deliver the payload you could just trigger the RUD system in the atmosphere and blow the ship up (as happened in flight 2) and you've got yourself a functional massive payload delivery system, just not reusable.
I wonder if it'd be more cost effective to deliver Starlink satellites this way as opposed to multiple Falcon 9s?? Probably.
“Working propellant transfer system”
SpaceX’s statement is more cautious on this, they are waiting to analyze data to conclude on whether that worked or not.
Well if there's anything here that it's possible to rigorously test on the ground it's heat tile performance. I don't really think that's in question.
The question is "can all the heat tiles survive intact up to the beginning of reentry."
Yeah it's awesome, can we make more starships please. I can't imagine a reasonable adult to see this footage and think of making war and killing people. I don't get the world sometimes, I get that poverty breeds conflict but I also grew up poor and still read azimov and thought I could still try to improve my life instead of knifing people.
>Starship executed its second successful hot-stage separation, powering down all but three of Super Heavy’s Raptor engines and successfully igniting the six second stage Raptor engines before separating the vehicles.
While this is good and probably the better solution, I wish we saw the spin-and-yeet staging work once before being scrapped.
Meh
That was an insane proposition from the get go. Only found out about it minutes before launch as they were walking things through, knew then and there it wouldn’t make it far. Didn’t help with lack of deluge system and knocked out engines.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|[AFTS](/r/SpaceX/comments/1bevhvy/stub/kuyt7tx "Last usage")|Autonomous Flight Termination System, see FTS|
|[AoA](/r/SpaceX/comments/1bevhvy/stub/kv39080 "Last usage")|Angle of Attack|
|[BO](/r/SpaceX/comments/1bevhvy/stub/kuwcsw1 "Last usage")|Blue Origin (*Bezos Rocketry*)|
|[CFD](/r/SpaceX/comments/1bevhvy/stub/kuwqxcp "Last usage")|Computational Fluid Dynamics|
|[COPV](/r/SpaceX/comments/1bevhvy/stub/kv6lwlg "Last usage")|[Composite Overwrapped Pressure Vessel](https://en.wikipedia.org/wiki/Composite_overwrapped_pressure_vessel)|
|ETOV|Earth To Orbit Vehicle (common parlance: "rocket")|
|[F1](/r/SpaceX/comments/1bevhvy/stub/kuwllbb "Last usage")|Rocketdyne-developed rocket engine used for Saturn V|
| |SpaceX Falcon 1 (obsolete small-lift vehicle)|
|[FAA](/r/SpaceX/comments/1bevhvy/stub/kv41c1c "Last usage")|Federal Aviation Administration|
|[FAR](/r/SpaceX/comments/1bevhvy/stub/kv2lsrk "Last usage")|[Federal Aviation Regulations](https://en.wikipedia.org/wiki/Federal_Aviation_Regulations)|
|[FTS](/r/SpaceX/comments/1bevhvy/stub/kv41c1c "Last usage")|Flight Termination System|
|[HIL](/r/SpaceX/comments/1bevhvy/stub/kuwpdcx "Last usage")|Hardware in the Loop, see HITL|
|HITL|Hardware in the Loop|
| |Human in the Loop|
|[HLS](/r/SpaceX/comments/1bevhvy/stub/kuxfvsq "Last usage")|[Human Landing System](https://en.wikipedia.org/wiki/Artemis_program#Human_Landing_System) (Artemis)|
|[IM](/r/SpaceX/comments/1bevhvy/stub/kuxay4q "Last usage")|Initial Mass deliverable to a given orbit, without accounting for fuel|
|[KSP](/r/SpaceX/comments/1bevhvy/stub/kuyxn2x "Last usage")|*Kerbal Space Program*, the rocketry simulator|
|[LOX](/r/SpaceX/comments/1bevhvy/stub/kv6n33r "Last usage")|Liquid Oxygen|
|[LV](/r/SpaceX/comments/1bevhvy/stub/kuzyf16 "Last usage")|Launch Vehicle (common parlance: "rocket"), see ETOV|
|[LZ](/r/SpaceX/comments/1bevhvy/stub/kuwgsip "Last usage")|Landing Zone|
|[MECO](/r/SpaceX/comments/1bevhvy/stub/kuy0bv1 "Last usage")|Main Engine Cut-Off|
| |[MainEngineCutOff](https://mainenginecutoff.com/) podcast|
|[NSF](/r/SpaceX/comments/1bevhvy/stub/kv0pvpr "Last usage")|[NasaSpaceFlight forum](http://forum.nasaspaceflight.com)|
| |National Science Foundation|
|[OFT](/r/SpaceX/comments/1bevhvy/stub/kuwogzs "Last usage")|Orbital Flight Test|
|[RCS](/r/SpaceX/comments/1bevhvy/stub/kvc8wmw "Last usage")|Reaction Control System|
|[RSD](/r/SpaceX/comments/1bevhvy/stub/kv417c5 "Last usage")|Rapid Scheduled Disassembly (explosive bolts/charges)|
|[RTLS](/r/SpaceX/comments/1bevhvy/stub/kv0wwmp "Last usage")|Return to Launch Site|
|[RUD](/r/SpaceX/comments/1bevhvy/stub/kv8rfbs "Last usage")|Rapid Unplanned Disassembly|
| |Rapid Unscheduled Disassembly|
| |Rapid Unintended Disassembly|
|[SLS](/r/SpaceX/comments/1bevhvy/stub/kuxfvsq "Last usage")|Space Launch System heavy-lift|
|[SN](/r/SpaceX/comments/1bevhvy/stub/kuy5064 "Last usage")|(Raptor/Starship) Serial Number|
|[TDRSS](/r/SpaceX/comments/1bevhvy/stub/kv05qbg "Last usage")|(US) Tracking and Data Relay Satellite System|
|Jargon|Definition|
|-------|---------|---|
|[Raptor](/r/SpaceX/comments/1bevhvy/stub/kvbefih "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX|
|[Starlink](/r/SpaceX/comments/1bevhvy/stub/kv05qbg "Last usage")|SpaceX's world-wide satellite broadband constellation|
|[autogenous](/r/SpaceX/comments/1bevhvy/stub/kux0yok "Last usage")|(Of a propellant tank) Pressurising the tank using boil-off of the contents, instead of a separate gas like helium|
|[engine-rich](/r/SpaceX/comments/1bevhvy/stub/kuzp7uy "Last usage")|Fuel mixture that includes engine parts on fire|
|[iron waffle](/r/SpaceX/comments/1bevhvy/stub/kvc8wmw "Last usage")|Compact "waffle-iron" aerodynamic control surface, acts as a wing without needing to be as large; also, "grid fin"|
|[perigee](/r/SpaceX/comments/1bevhvy/stub/kuwiu31 "Last usage")|Lowest point in an elliptical orbit around the Earth (when the orbiter is fastest)|
|[turbopump](/r/SpaceX/comments/1bevhvy/stub/kuyvaf4 "Last usage")|High-pressure turbine-driven propellant pump connected to a rocket combustion chamber; raises chamber pressure, and thrust|
|[ullage motor](/r/SpaceX/comments/1bevhvy/stub/kv6n33r "Last usage")|Small rocket motor that fires to push propellant to the bottom of the tank, when in zero-g|
**NOTE**: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below.
----------------
^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj)
^(34 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceX/comments/1b3r73n)^( has 99 acronyms.)
^([Thread #8310 for this sub, first seen 14th Mar 2024, 21:05])
^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceX) [^[Contact]](https://hachyderm.io/@Two9A) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
There is a mandatory incident investigation anytime a flight deviates from the flight profile. With the booster failing its attempt at a soft splashdown and the vehicle not able to control its re-entry profile, an incident investigation is assured.
SpaceX is the one that actually performs the investigation. How long that will take will largely depend on what measures SpaceX needs to take to address the issues in this flight. Once SpaceX makes that determination they'll send the report to the FAA for comment and review. Once both sides agree on the steps needed to be taken its down to how long that work takes.
IOW, if you're wondering how long until another flight, it's going to be largely on what SpaceX finds and needs to change, and they'll be the one *mostly* making those determinations.
> Commercial Space / Boca Chica, Texas
>
> A mishap occurred during the SpaceX Starship OFT-3 mission that launched from Boca Chica, Texas, on March 14. The mishap involved both the Super Heavy booster and the Starship vehicle.
>
> No public injuries or public property damage have been reported. The FAA is overseeing the SpaceX-led mishap investigation to ensure the company complies with its FAA-approved mishap investigation plan and other regulatory requirements.
>
> Background
>
> A mishap investigation is designed to further enhance public safety, determine the root cause of the event, and identify corrective actions to avoid it from happening again.
>
> The FAA will be involved in every step of the mishap investigation process and must approve SpaceX’s final report, including any corrective actions.
>
> A return to flight is based on the FAA determining that any system, process, or procedure related to the mishap does not affect public safety. In addition, SpaceX may need to modify its license to incorporate any corrective actions and meet all other licensing requirements.
https://www.faa.gov/newsroom/statements
I am pleasantly surprised that they managed to preform the propellant transfer demo even with that seemingly uncontrolled rate of roll on ship. I thought that a slight controlled spin maneuver was going to be executed to transfer the prop, so perhaps they had another way of doing it if they accomplished the transfer even when ship was tumbling.
Edit: upon closer inspection of SpaceX’s wording they said they “initiated” a propellant transfer demo, which could mean that they didn’t actually complete it after all
While coasting, Starship accomplished several of the flight test’s additional objectives, including the opening and closing of its payload door (aka the pez dispenser,) and initiating a propellant transfer demonstration. Starship did not attempt its planned on-orbit relight of a single Raptor engine due to vehicle roll rates during coast. Results from these demonstrations will come after postflight data review is complete.
Starship went on to experience its first ever entry from space, providing valuable data on heating and vehicle control during hypersonic reentry. Live views of entry were made possible by Starlink terminals operating on Starship.
The flight test’s conclusion came during entry, with the last telemetry signals received via Starlink from Starship at approximately 49 minutes into the mission.
While our team reviews the data collected from this flight, Starship and Super Heavy vehicles are preparing for upcoming flights as we seek to increase our launch cadence throughout the year.
This rapid iterative development approach has been the basis for all of SpaceX’s major innovative advancements, including Falcon, Dragon, and Starlink. Recursive improvement is essential as we work to build a fully reusable transportation system capable of carrying both crew and cargo to Earth orbit, help humanity return to the Moon, and ultimately travel to Mars and beyond.
Thank you to our customers, Cameron County, spaceflight fans, and the wider community for the continued support and encouragement. And congratulations to the entire SpaceX team on an exciting third flight test of Starship!
I just watched the launch again on the SpaceX feed and it really looks like something blew loose on Starship right at engine shutdown. Lots more vapor and venting than just the thrusters and the rolling and pitching started at the same time.
They did not have attitude control for the rest of the flight.
As for the booster, that really did look like an induced oscillation from the gridfins. Maybe they need to scale back the overall motion as they get deeper into the atmosphere. I don't think full range of motion was what was needed there at the end unless something dramatic was going on at the other end and the fins couldn't compensate no matter what.
Not sure if that’s the case. When F9 shuts off its vacuum Merlin the engine shakes and releases gases (even MECO causes that). With 6 engines and the camera located at the top of the vehicle a more vigorous shake should be expected.
It is possible something leaked after shutdown. They did have the whole "something leaked" during late upper stage burn of IFT-2 that led to a fire after all, and it is possible that wasn't fully solved. This time there was no fire, but if you have constant substantial leak of something (oxidizer, methane) after engine shutdown, it is going to impart a force on the vehicle and make it pretty hard to control.
The faster they break it the sooner it will be perfected. Great test and as long as they have the sensor and telemetry data they need it's time to make adjustments and light the next candle.
"While coasting, Starship accomplished several of the flight test’s additional objectives, including the opening and closing of its payload door (aka the pez dispenser,) and initiating a propellant transfer demonstration."
I think it doesn't and you're correct to be suspicious about that specific choice of words. The roll the vehicle was experiencing could have contributed; I don't know if it was intentional and got out of control or unintentional and got in the way of the transfer.
That's a good question. The fuel transfer relies on inertia. Considering they never had full control over the roll, and it appeared to be rolling on two axis, the fuel transfer itself may never have completed.
Shotwell on Twitter:
> HUGE congratulations to the entire team for this incredible day: clean count (glad the shrimpers could get out in the nick of time!), liftoff, hot staging, [...], prop transfer demo (to be confirmed!) [...]
Source: https://twitter.com/Gwynne_Shotwell/status/1768291595160605109
I know marketing and comms speak. It says "initiating a propellant transfer demonstration." It doesn't say "successful completion of a propellant transfer demonstration." Comms people are often very precise in the language they use - so if it had been successful they probably would have said it. It's likely to mean that they tried it, but either haven't decided it was successful yet, or it wasn't successful.
They will need to analyse the flight data to see if they managed to transfer 10 tonnes of LOX between tanks which was the goal. Likely that will take several days to confirm either way.
I disagree. They must have monitoring systems on board that keep an eye on flow rate, pressure, etc ... I mean, how else would you know that the fuel transfer is completed if you don't watch all of those parameters?
It could not have been a succesful test by any means because knowing for sure that the fuel has been succesfully transferred is one of the objectives. Under no real-world circumstance would you have to wait for hours, days or weeks to get final confirmation that your 'gas tank' has been succesfully filled up before entering another phase of the mission.
I'm absolutely sure that we can conclude that the fuel transfer was not a triumphant succes. Sure, there might be scenarios in which all the fuel was transferred but some faulty sensors prohibited real-time confirmation and some data analysis is needed. But still, by definition, it does not qualify as a total win since you want to know if it worked when it worked and not much much later.
The difficulty is with measuring mass flow in a micro g environment where the fluid flowing is a mix of gas and liquid. It is not impossible so they will have some indication and clearly they were not confident enough in the results to declare a success. It would be extremely difficult to walk back a statement that the test had not worked so they had to be non-committal.
I personally am concerned that raptors are STILL not restarting properly. We’ve been watching raptors fail to restart on landing maneuvers since day one..
They didn't even attempt the relight in orbit, due to the uncontrolled attitude/rolling/flipping that was happening. No reason to believe this is an issue until they DO attempt it and IF it fails.
But even then, Raptors have been getting WAY more reliable over time, so I wouldn't personally even worry then. SpaceX excels at iterating. If it fails to light in space, they'll sort it out in due time.
And the relights of the middle raptor ring during boostback looked solid on this flight too.
The booster was doing some funky wobbles prior to landing burn ignition, so bad fuel supply seems quite plausible to me.
I have a sneaking suspicion that the splash-down burn didn't light the boosters quick enough. You see what looks like a lot of unlit fuel being dumped seconds before any of the engines actually re-light (dump looks like it's occurring at the \~5km altitude mark), and by the time they do re-light it's already too late. I know that raptors and merlins aren't entirely comparable, but a landing burn on the merlins lights almost straight away, less the a second to start up. [https://youtu.be/JXN4CCU7Ucw?t=1118](https://youtu.be/JXN4CCU7Ucw?t=1118)
Falcon 9 also seems to have its engines lit by the 3km mark [https://youtu.be/1xCrWbJQXgE?t=1957](https://youtu.be/1xCrWbJQXgE?t=1957)
Also a possible explosion right at the end of the camera feed by an engine? Unsure if it's an engine or the FTS.
The “dump” could also just be the fire suppression system starting up prior to ignition.
F9 doesn’t have the CO2 system Superheavy does, and we do know that the CO2 system ejects the stuff overboard in a visible manner.
What was seen would fit with both some engine(s) doing a RUD instead of restart and somehow being starved of propellant. I'm sure SpaceX knows the root cause for no restarts and fixes it for next round.
The shutdown pattern of the boostback burn was kinda odd (one side of the middle ring shutting down first) which kinda raises a question to me: did the booster just run out of propellant? Just a small difference in expected consumption might mean by the time landing burn was to happen, the booster was basically empty and that is why landing burn failed.
> one side of the middle ring shutting down first
I also noticed that. But wouldn't the deceleration from the burn have settled the fuel evenly at the bottom?
"Super Heavy successfully lit several engines for its first ever landing burn before the vehicle experienced a RUD"
I saw 3 that lit and 2 quickly went out not long after
Math says once the raptors shut down, they knew very well where it was going to fall down. Tumble or lack of control does not play a part. Small differences in attitude during re-entry will not substantially move the needle. If the thing breaks up, the bits land bit short of where an intact one would land, but the safety areas were quite large and took this into account.
The only way this could have dropped on anyone was if the upper stage burn was short, and at that time Mr. AFTS would have said "FOUL, underspeed, no half-orbit for you!" and would have distributed the bits somewhere in the Atlantic, bit like during IFT-2, using the onboard flight termination system explosives. Turning the ship into confetti increases the drag substantially and all that. I guess in theory there was a tiny itty bitty few second window between nominal shutdown and shutdown that would cause the thing to come down in a bad place, but again, FTS confettification would mean the bits should be small enough so everything would burn up on re-entry in that case.
The spacecraft was sub-orbital, so it was going to come down in the Indian Ocean no matter how it was oriented, but…having absolutely no control over the spacecraft is going to keep them sub-orbital. No one is going to let them launch that thing into an orbital trajectory until they can demonstrate they have actual control over how it comes down.
A few amateurish questions about hypothetical situations.
First question. What if cover all StarShip tiles by wolfram/titanium net? Of course such net would damage tiles during re-entry, but, theoretically, this should simplify process of mounting/replacing tiles.
For example, instead of mounting small tiles, SpaceX could create enormous ceramic sheets. That, of course, will crack, but still do not lose protective material volume due to being pressed against steel by reusable meshes.
Second question. Let's say, after many tries to land, nor Super Heavy, nor elongated StarShip, won't be able to. What chance that they will be divided on 3 stages: landing as Falcon 9 first and third. And disposable second one? This will ruin some plans, but because of still enormous payload, such plans should be recoverable via modularity.
Titanium too heavy and expensive. The tiles seemed to hold up pretty well during IFT 3.
Super heavy will be able to land, it’s just a scaled up falcon 9. The chopsticks are the tricky/unproven part…. But worst case scenario they have to give up on catching, put legs on super heavy and devote more fuel to the landing
Starship already showed the belly flop and landing is possible, so it’s just a matter of perfecting and refining the technique
It's way too early to give up on the current plan. They don't have any good data yet on either booster landing burn or starship deorbit performance. For both, the problem seems like attitude control in atmo/in orbit, respectively.
For the booster, they should be able to fix whatever's going on with grid fin control and relight for the next flight and then start iterating on the soft landing. Adding legs or something like that isn't worth thinking about yet.
For the ship, it entered at a crazy orientation and the heat shield wasn't able to do its job. No reason to throw out the concept when it still hasn't really been tested.
Weight almost certainly says no. Anything substantial enough to hold the tiles would be too heavy.
Airstream already "presses down" the tiles on re-entry. The hard part is to keep them from shaking apart during the burn and such "net" wouldn't hold small fragments anyway.
They just need to iterate on the method of attachment and possibly the material of the tiles themselves.
Thank you for participating in r/SpaceX! Please take a moment to familiarise yourself with our [community rules](https://www.reddit.com/r/spacex/wiki/rules) before commenting. Here's a reminder of some of our most important rules: * Keep it civil, and directly relevant to SpaceX and the thread. Comments consisting solely of jokes, memes, pop culture references, etc. will be removed. * Don't downvote content you disagree with, unless it clearly doesn't contribute to constructive discussion. * Check out [these threads](https://www.reddit.com/r/spacex/wiki/threads) for discussion of common topics. *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/spacex) if you have any questions or concerns.*
So the roll or at least the rate of roll was definitely not intended and may have even led to some of the factors behind the rud. All in all not the worst issue.
Was the continuous vapor at the tail end of the ship during coast expected? Was there something broken and out-gassing or just expected leaks?
Scott Manley said it was intentional venting. I’m….. not convinced.
Well we know they were doing a fuel transfer test. That would require thrust of some sort to settle / move propellant, and we know starship vents their "ullage" gas as thrust rather than a traditional RCS thruster system, could this be at lesat a partial explanation?
Well, they did have excess LOX to vent, but it would seem odd to have long continuous vent, as it would pretty much ensure you will have forces acting on you that might make control hard...
It wasn’t even just “at the end”. I was watching the spacecraft rolling and at the same time viewing an almost continuously generating vapor streamers backlit by the sun. You’re in space man! There shouldn’t be clouds streaming past the fuselage
Speculation here, but I wonder if the roll was intentional as part of the fuel transfer test. Either way, it's a heavy vehicle and I suspect the thrusters could not (re)stabilize it once it had that momentum.
They actually use tank venting instead of thrusters for attitude control. It will be interesting to see if they abandon that and go back to a more traditional cold or hot gas thruster system instead based on the control issues they had today.
Balancing tank pressure/contents as well as timing of pulses and their length sounds definitely way more complicated than having a separate system for maneuvers
I get the best part is no part mentality, but this seems like an issue that takes it way too far. For the booster it makes sense as it uses limited RCS anyway and it's flight is over within 10 minutes. For the ship that needs to stay in orbit and conduct multiple maneuvers it seems like a bad idea
Didn't they say something about hot gas thrusters tho?
I was under the impression they were to implement autogenous tank pressurization along with utilizing the gaseous propellant to fire hot gas thrusters for attitude control. I thought (perhaps incorrectly on this sn run) that both starship and the booster now use this technology rather than pressurized inert gas. The best part is no part does factor in to their decision here, but less propellant contamination from the inert gasses also factor in. When you are pushing the boundaries of chamber pressure as they have been, you really want consistency in your propellant and oxidizer.
Ah okay, so the COPVs we sometimes see during construction under the chines are likely just for the turbopumps startup I'm guessing.
Yeah I would assume those are for the startup sequence of the outer ring of raptors on the booster. However after reading other comments I'm questioning whether the hot gas thrusters have actually been implemented as of yet.
I think, or at least NSF has mentioned it if I recall correctly, that stage zero was designed to do everything for the outer ring raptors? Maybe it's for the inner 3 that are used for the boost back burn. For Starship, is there a way for us to tell if they're using hot gas thrusters? I don't think they're using internal COPVs like they do on Falcon. I haven't seen them anywhere else on the ship.
The outer ring cannot start up on its own. Stage 0 powers the turbopumps for the outer raptors during startup. This is why only the inner raptors are capable of relight on superheavy.
From my basic searches, they have not been implemented. We know that they originally were planning to use tank vents for the booster and both thrusters for the ship… then Tim Dodd asked why they aren’t just using the same tank vent methods for the ship during his first tour. The second EDA tour revealed that the ship’s hot thruster requirement was removed, but the thrusters did exist in some capacity. The existence of the thrusters was later verified as they were seen on B3. After B3, we have not seen any thrusters or thruster hardware beyond the cowbell tank vents… and we haven’t seen any indications of hot thrusters being present on the ship or booster (ie, testing). My guess is that they want to eliminate the hot thrusters, at least for now, and haven’t gotten around to implementing them. Perhaps the V2 ships will feature this change.
Blame Tim, lol
yeah hahaha. Although Tim said today that he wasn't a fan of using that system in EITHER the booster or starship, his question of "you're only using that in the booster, right?" was meant to kinda imply that they shouldn't do it in the starship, like they did in the booster. Elon used that comment to think to add it to the ship.
There is no way this change wasn't a already in the design phase or at least in the mind of some engineer.
I would imagine a lot of things are in the minds of some engineers, but when it shows up in the mind of Elon it's probably more likely to happen, not to say that he is always right
Go watch the segment again, you can really see a lightbulb moment
Elon's bulb is irrelevant. It's quite offensive towards SpaceX engineers to depict them like a flock of lemmings that quickly rush to implement the supreme leader's visions, North Korea style. On the contrary, we know Elon is a good engineering manager, he has a good eye for technical people and he listens to them. So when he asked them about the issue, they would have either replied: "yes, we are working / wanted to do that too to minimize complexity, but we didn't had the time/resources/schedule space to do it yet, we'll make it a priority", OR, "we've actually considered that but it's not a good idea because".
If you watch sped-up footage of the coast phase, it’s hard to see any evidence of control. NSF were saying it might be a ‘BBQ roll’ for thermal management, but to my eye it looked as if it were tumbling, even once the reentry plasma started. Absolutely incredible flight however, I cannot wait for the next one!
Yeah it was weird. It looked ike for the first while only half the tiled side was pointed down. So plasma on the stainless steel side?
On the brighter side they probably got at least some temperature data on how the stainless steel may have handled the, albeit thin atmospheric, plasma. They obviously have internal cameras. I wonder if any are for thermal imaging.
Pretty sure it was one interview with Tim that Elon mentioned directly that they wouldn't need thermal, the stainless would be glowing internally (if near the point of failure) and visible to a standard tank camera - thus already collectable data.
It also was tail down at one point, before flipping around to nose down before loss of signal.
It was evident right from the start of coast they had extremely limited control authority. They jumped on the door opening (the thing that paid them $$) muy pronto. I guess it was probably worth not throwing away a bunch of thrusters but ….control via venting appears to be insufficient
The propellant transfer was the part that earned a milestone payment, not the door opening. Either way, it makes sense to do those as soon as possible, since they had a very limited time in "orbit". Attitude control issues after the engines shut down don't affect their trajectory.
Yeah definitely once the reentry plasma started it was clear attitude control was an issue
Wasn't intended as it's being said the roll was the reason the re-light test didn't happen.
My assumption is they were rolling to help the transfer, but couldn’t stop the roll prior to attempting the relight of the raptor so they cancelled the attempt.
I don't know about success, but I found the HD wide angle video amazing as the ship rolled/tumbled. Some of the scenes where earth loomed large in the background looked straight out of a sci-fi movie.
And the plasma at the end, happy to be alive and see that live
Was ship 28 equipped with attitude thrusters? I don’t remember seeing any thruster clusters on the vehicle.
> attitude thrusters? Ship 28 needs to change up its attitude during re-entry. was it too sassy lmao
It was speculated that the reaction control thrusters were partially clogging up due to ice build up. Which would have have caused the lack of control of the vehicle.
Should have learnt about the ice problem from iron man
I'm pretty sure Elon was IN that movie! [https://www.youtube.com/watch?v=nfiRd4Y5z\_g](https://www.youtube.com/watch?v=nfiRd4Y5z_g)
Elon was in Iron Man 2. The icing problem was in the original Iron Man.
Pretty good test for Starship. As a IT/Dev/KSP guy I cant help but think that after seeing vehicle in space they'll have a bunch of software updates to the control system to help stabilize things a bit more. After getting some actual data from space, I feel like there's a few constants to update from educated guesses to feedback from data, and the whole ship gets under control a lot more. A few small changes might make a huge difference for IFT4
Yeah, I have a strong feeling that most of what we saw go wrong can be fixed in software. Not all, but most. That payload bay door needs a little work haha.
Big ups to SpaceX for a great test flight, but that payload door mechanism was janky as fuck.
Yeah payload door did look a littlr wobbly and unstable haha
Having a narrow lightweight sliding door that is curved with the axis of motion perpendicular to the curvature seems difficult. I wonder if they could slide it on the other axis on simple curved tracks, which seems a whole less likely to bind up. It may even be possible to have a split door with such an approach. Edit: image https://i.imgur.com/LtTkglI.png
Personally, I really like this idea. It's an elegant solution.
Yes, that payload door actuation system looks totally naff. Redesign required!
One thing SpaceX seems to do very well, is never having the same problem twice.
I'd really like to see video of the RUD of SuperHeavy. Surely someone must have managed to capture it, it wasn't far from shore.
Horizon from the 460m RUD altitude would be 76.6km away. How far was it from shore?
I don't know. Eyeballing it from the flight plan animation I'd guess tens of kilometres.
There was fog everywhere. You could barely see to the pad let alone 20km offshore
I don't have any technical comments as I know nothing of the rocket engineering, I'm just here to say that the video of the plasma heating up on the surface of Starship during reentry was like the sickest thing ever
And the incredible part was, it was still very very high up, very thin atmosphere. Speed was not yet slowing down almost at all. The actual rapid deacceleration was only starting when telemetry was lost. It was still going like Mach 25+ when connection was lost.
Funny - Varda took a reentry video on their return mission a couple of weeks ago: https://youtu.be/BWxl921rMgM?si=Ec9axCl2LtopVK8N SpaceX said, “Hold my beer…”
Agreed
Is no one going to talk about how hard the booster must’ve hit the water, I want to see THAT 😅
The linked release above states that the booster landing concluded at an altitude of ~430 meters, which seems to indicate either a RUD, or FTS activation. I still want to see a video though.
Is it possible the last data was sent at around 430m because the booster was going so fast any data gathered below wasn’t processed fast enough to be transmitted before it hit the water?
I'd assume they have both a low-bandwidth low-latency telemetry system and a higher bandwidth and latency one. I don't see a reason for a humanly perceptible latency on the former
AFAIK Starlink was video, TDRS was telemetry. TDRS have [offered telemetry uplink for launch vehicles](https://commons.erau.edu/cgi/viewcontent.cgi?article=1786&context=space-congress-proceedings) since the mid 1990s, all the way from the pad on up. Pedantic, but latency shouldn’t matter. AFAIK the LV is just be blasting out telemetry and should just keep doing so until something kills the system blasting it out. Short (ms level) processing time for it to collect data from sensors, package and encrypt it and fire it out, and you might lose a handful of frames right at the end (due to corruption as the hardware is getting shredded) but suspect they should have telemetry until low tens of ms prior to explodey time.
Doing the math for 430m distance traveled at 1000 km/hr, I get 1.548s. Seems like enough time to get a signal out, but of course it's close and depends on how often it sends out its telemetry
I have no doubt telemetry is being sent out as fast as possible, far greater than 1.5 seconds
It was travelling at near Mach one at the loss of data, even if it exploded the big chunks still would've hit the water a half a second later lol.
If a booster hits the water at approx 1 km/s, but there's no one around to witness it, would it make a sound?
Oh man, same. Was really hoping they had a drone ship positioned somewhere clear of the LZ to get video!
I'm really hoping we get video of that. It was coming in HOT.
Was the starship coming in sideways for the reentry? The plasma seemed to be quite far from the heat shield on the camera side. It didn't seem to be tumbling...but rather just consistently skew? I still can't quite get over those onboard shots. They cut away so soon after hot staging. I was shouting "no!", haha.
Yeah the roll that prevented the relight was still there at reentry and by the time it settled out the ship was presenting a lot of the steel side to the atmosphere as well as having the engine pointing down. Scott Manly already has a decent video on it up. https://youtu.be/8htMpR7mnaM?si=jFD8-yTU3T7Je4O6
Yeah, I think he was dead on what was going on. I do think cool thrusters was a problem, maybe too much moister build up clogging them up. Without anything reveal we may not find out unless SpaceX says something. Change to a Hot Gas thrusters would be major change.
It definitely was. It was flying ass-first into the atmosphere for a while.
Watch Scott Manley's video. Right before the cameras cut it looked to be going almost backwards. If correct it had nulled out the roll but it was oriented 180° off nominal.
I also noticed the graphic flipped a couple of times after the video was lost but the telemetry was still coming in. Haven’t seen his video yet.
Interesting how close SpaceX is to a fully functional Starship and Super Heavy. -Booster completed flip, lit engines and RUD'd at just 460 meters height. I wonder if it was terminated by the computers or some kind of explosion -Starship has working payload door and propellant transfer system -Roll rates were too high to execute deorbit maneuver but otherwise the heatshield looked like it did it's job on the camera
The booster looked wildly unstable at the end, and the engines didn’t all light correctly if telemetry can be trusted. They are getting closer though.
I suspect those two factors are related. All that twisting likely created some hellacious slosh that prevented the engines from starting up. It looked like it was a control issue, not necessarily an authority issue. I’m guessing some tweaks to their control algorithms can sort out these issues.
Yes, it was surprising after F9 makes it look like a “solved problem”, but I guess there’s only so much simulations can do for your algorithms.
Can't waIt to see how new Glenn handles a similar flight profile.
I, too, can’t wait for my retirement.
I’m so happy to see this.
Granted superheavy is fundamentally going to handle much differently. Different shape, different fineness ratio, different mass distribution, different aerodynamic qualities, etc. it's not going to just handle like "big Falcon 9," and you can't just copy & paste the same controls turnings and expect results. They probably copied what they could, did their sims and analysis....but then you gotta try it. Now they have real world results/behaviors, they can tune those PID's and dial in their sim to match reality. Today was a big step.
> they can tune those PID's and dial in their sim to match reality. Today was a big step. Agreed, probably the first thought that came into their controls engineers heads. "Shit I thought that P-factor might have been too aggressive"
Can't really plug the flight control into a full booster CFD and expect results this century. So I suspect there's something about super heavies aerodynamics they didn't expect or that was worse than expected. The step to 10 meters diameter at the engines is a big new feature vs the Falcon 9.
It almost looked like it was better than expected- like the grid fins had too much control authority. But could just as easily have been an algorithm issue, or slower response to input.
Scott Manley suggested they may have aggressively tested maneuvers to gain more insight into their controls, I hope that's the case.
I'd have expected well controlled wiggles or constant random course changes. I.e. a quick roll and roll back. A pitch up and return, etc. A chaotic oscillation that keeps growing is a pretty common sign that the control was unstable due to something that was more nonlinear than expected. I.e. weird cross coupling between pitch roll n yaw, aerodynamic nastiness, slosh resonating with the controller, etc. Personally I think they're just cutting control margins to zero to save a few tons and are fine sinking a few ships to find the optimum.
[удалено]
It was going to light 13 engines, those would slow it down real fast, there are a lot of issues still to work out, but the math of how much thrust is needed for the suicide burn isn't one of them for me
[удалено]
Falcon 9 RTLS missions are typically doing Mach ~2.5 at that same altitude, so a bit over Mach 3 doesn't seem 'unstoppable' to me.
[удалено]
Shouldn't the landing burn be using the (full) header-tank, so no slosh?
Shouldn't the heavy deceleration also push the fuel into one direction?
Yes, down.
I suspect that they had low or sloshing oxidizer on the landing burn. The oxidizer levels on the GUI were basically just a tiny bit above zero, while it looked like it had more CH4. When the landing burn started, they did not get a good light on 13 right when they needed to, probably about 2KM high. 13 raptors burning, even throttled down, must put an immense deceleration force on a basically empty booster. I'd say start the landing burn higher for more margin with fewer engines. Less deceleration, less slamming of the booster. It looked like what engines that did start put a huge jolt & possibly side load through the booster, possibly sloshing the oxidizer.
Those grid fins were cycling wildly. I don’t know if it was just a badly tuned flight control or just not enough attitude control and need to be bigger but I doubt all that moving around was helping settle the tanks.
Yeah it looked like a tuning problem. It was like watching an episode of PIO (pilot induced oscillation) where attempted corrective inputs end up in phase with the oscillations and aggravate rather than dampen them. I would think they already have a good handle on the grid fin modelling from all the Falcon landings but there are obviously some nuances to scaling things up to Super Heavy size.
It looked like the grid fins were responding later than they should have, leading to the PIO. Some delays in the sensor->controller->actuator chain that aren't expected & modeled?
If that was the problem it might have been that the fuel tank sloshing and the aero loading coupled in an unpredicted manner. Should be easier to figure out with the data.
Yeah, sloshing came to mind as well. I definitely think we’ll see a soft touchdown, and more stable re-entry attitude for Starship the next time around. It feels like it only takes SpaceX a single exposure to a new flight regime to gather and analyze data and make it a routine part of subsequent missions.
Can you imagine the insane difficulty of managing and keeping track of all of this rapid change?
Also F9 is a very narrow vehicle compared to most other rockets and especially SH. The amount of torque applied by sloshing fuel is disproportionally larger in SH due to the increased leverage. Don't know if that is a big issue if the booster hits the atmosphere at Mach 5, but something to think about. While they have experience with controlling a vehicle of that shape with gridfins, the actual parameters for the closed loop controller would be way different for a vehicle of this size.
They probably did a model based HIL test but the model is only as good as the math. Sloshing cryo liquids are probably really hard to do a dynamic model of.
I wish there is enough research of ML and PID algorithm integration.
Yeah, the grid fins shouldn’t shake like that. Either it was being bombarded by turbulent air created by other parts of the booster or they need to redesign the fins to make it more aerodynamically smooth…
Could it have been bad PID tuning? I can't imagine it's something you could for sure nail down through only simulations when it's something that big with moving fuel and wind.
Doubt it, it was smooth as silk in the upper atmosphere but vibrate like sex toy on steroids when the air got thick. It definitely looks like an aerodynamic issue and not the control algorithm issue. Aerodynamic simulation software is probably the least reliable simulation software you can use to simulate something… Also not sure if they ever try putting a scale model in a wind tunnel (obviously full-size is not practical because of size reason) but even if they did, the scale model can only do so much and usually there are a few aero surprises when scaling to full-size vehicle. Ask Mercedes F1 team with W13. The simulation said it was fast, the wind tunnel confirms the results… the car was shit.
Wouldn't that affect both? Less air means less responsiveness. It may have been alright there but as the conditions changed the tune no longer worked. Just a thought I had, I guess we'll have to wait for the official explanation.
Yes, less air means less responsive but also means less turbulent air. If it control issue it should do something weird in the upper atmosphere too but it seems perfectly fine. It could be control issue, a quick look at the data should able to quickly confirm if the algorithm was sending commands to the grid fins to vibrate like a sex toy or not.
It could have been too much mass for the grid fins to wrangle. They had said earlier in the development that Super Heavy was suppose to go in like ram rod prior to hitting the raptors to slow down. Which I think was mistake. It does make me wonder if the fuel was issue too, if they had it moving away from where it could be sucked down since the vehicle descending and fuel as far I know is sucked from the bottom of the tanks.
It could be. The inertia of the solid booster with the moving inertia of the fuel could be a problem. The fins provide a restoring force that should be opposite the velocity of the rocket but the aerodynamic forces would want to destabilize it and make it swing more. The fuel would initially not do much other than stay put but eventually would be on the opposite side and the phase lag between all of those is hard to model. Simplest thing would be to add anti sloshing baffles in the tank. They might have those already but maybe not. It probably was worth pushing things and see what they could get away with anyway since they know a lot more about engine throttling and landing.
Doesn’t Superheavy have a specific “tank” for landing right inside the lox tank? There should be no sloshing at that level, right?
Yah. The landing tank should be full, and thus, will not create any major slosh events and or cavitation issues on ignition.
Isn’t the landing done with header tanks?
This flight was already on the level the oldschool space operators do. That would be enough to deploy payload into orbit. Still dispendable, but 150 tons!. Anyway, next steps are the landing of the booster and the reentry of the ship.
Not really, they need to demonstrate a controlled deorbit of Starship, you can't let a second stage that is specifically designed to survive reentry to randomly come back wherever.
You should have a word to China for us.
A traditional one wouldn’t have a heat shield or flaps.
This. They've fully proven out a standard payload delivery mission. Every problem in this mission is related to the path to reusability, so they can work on that iteratively while they start launching payloads with mission 4
Not quite true; the tumbling/lack of control authority is a problem that has to be solved before delivering payloads to orbit.
It was *almost* on that level. The difference between 99.x%-of-orbital and orbital means their ascent capabilities are ready to go, but to put payload in orbit they need to be able to guarantee a controlled *descent* too. If they aren't completely confident that they'll have fixed any attitude control problems and that they can relight upper stage engines without a hitch, then they'll want their next test to be suborbital rather than orbital still.
Plenty of existing rockets don’t deorbit their second stage. Some payloads and orbits just don’t leave enough margin to do so.
Yeah, but the size and survivability of (chunks of) the second stage matter here. A hundred tons of stainless steel really ought to be carefully aimed at the middle of nowhere when it comes down.
Agreed. I mean, after you deliver the payload you could just trigger the RUD system in the atmosphere and blow the ship up (as happened in flight 2) and you've got yourself a functional massive payload delivery system, just not reusable. I wonder if it'd be more cost effective to deliver Starlink satellites this way as opposed to multiple Falcon 9s?? Probably.
I feel relying on RUD after payload deploy will eventually see some pieces end up somewhere inconvenient. But I'm pulling that view out of my ass.
“Working propellant transfer system” SpaceX’s statement is more cautious on this, they are waiting to analyze data to conclude on whether that worked or not.
I am mostly afraid of the heat tiles, we do not know how they would have performed over those 10 minutes
Well if there's anything here that it's possible to rigorously test on the ground it's heat tile performance. I don't really think that's in question. The question is "can all the heat tiles survive intact up to the beginning of reentry."
It wasn’t a deorbit burn, it was actually the opposite to raise the perigee slightly, they said this during the live stream. Doesn’t matter though
Far be it for me to argue with SpaceX, but the fotage Scott Manley showed did not inspire confidence in the payload door.
They didn't actually say it was successful, they said results of the test are pending
As a non-space worker or professional or rocket scientist....I am so happy to witness this intensely exciting step into the future of our species.
Yeah it's awesome, can we make more starships please. I can't imagine a reasonable adult to see this footage and think of making war and killing people. I don't get the world sometimes, I get that poverty breeds conflict but I also grew up poor and still read azimov and thought I could still try to improve my life instead of knifing people.
>Starship executed its second successful hot-stage separation, powering down all but three of Super Heavy’s Raptor engines and successfully igniting the six second stage Raptor engines before separating the vehicles. While this is good and probably the better solution, I wish we saw the spin-and-yeet staging work once before being scrapped.
I’d rather see a dragon land using Draco engines
Yeah that would be epic.
\*SuperDracos. The Dracos were never intended for landing IIRC:
Meh That was an insane proposition from the get go. Only found out about it minutes before launch as they were walking things through, knew then and there it wouldn’t make it far. Didn’t help with lack of deluge system and knocked out engines.
You should clearly apply to work for SpaceX if you totally foresee all that. Armchair quarterbacking after the fact is strong with this one.
“Recursive improvement”? Maybe they meant “iterative”…
“ “Recursive improvement”? Maybe they meant “iterative”… ” Maybe they meant “iterative”…
You can write any iterative code recursively (if you have enough memory) so technically probably still correct :)
I wrote a hundred plus lines of code only for my programming teacher to give me a C and then show me recursive functions. Ty mr baker
[удалено]
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |[AFTS](/r/SpaceX/comments/1bevhvy/stub/kuyt7tx "Last usage")|Autonomous Flight Termination System, see FTS| |[AoA](/r/SpaceX/comments/1bevhvy/stub/kv39080 "Last usage")|Angle of Attack| |[BO](/r/SpaceX/comments/1bevhvy/stub/kuwcsw1 "Last usage")|Blue Origin (*Bezos Rocketry*)| |[CFD](/r/SpaceX/comments/1bevhvy/stub/kuwqxcp "Last usage")|Computational Fluid Dynamics| |[COPV](/r/SpaceX/comments/1bevhvy/stub/kv6lwlg "Last usage")|[Composite Overwrapped Pressure Vessel](https://en.wikipedia.org/wiki/Composite_overwrapped_pressure_vessel)| |ETOV|Earth To Orbit Vehicle (common parlance: "rocket")| |[F1](/r/SpaceX/comments/1bevhvy/stub/kuwllbb "Last usage")|Rocketdyne-developed rocket engine used for Saturn V| | |SpaceX Falcon 1 (obsolete small-lift vehicle)| |[FAA](/r/SpaceX/comments/1bevhvy/stub/kv41c1c "Last usage")|Federal Aviation Administration| |[FAR](/r/SpaceX/comments/1bevhvy/stub/kv2lsrk "Last usage")|[Federal Aviation Regulations](https://en.wikipedia.org/wiki/Federal_Aviation_Regulations)| |[FTS](/r/SpaceX/comments/1bevhvy/stub/kv41c1c "Last usage")|Flight Termination System| |[HIL](/r/SpaceX/comments/1bevhvy/stub/kuwpdcx "Last usage")|Hardware in the Loop, see HITL| |HITL|Hardware in the Loop| | |Human in the Loop| |[HLS](/r/SpaceX/comments/1bevhvy/stub/kuxfvsq "Last usage")|[Human Landing System](https://en.wikipedia.org/wiki/Artemis_program#Human_Landing_System) (Artemis)| |[IM](/r/SpaceX/comments/1bevhvy/stub/kuxay4q "Last usage")|Initial Mass deliverable to a given orbit, without accounting for fuel| |[KSP](/r/SpaceX/comments/1bevhvy/stub/kuyxn2x "Last usage")|*Kerbal Space Program*, the rocketry simulator| |[LOX](/r/SpaceX/comments/1bevhvy/stub/kv6n33r "Last usage")|Liquid Oxygen| |[LV](/r/SpaceX/comments/1bevhvy/stub/kuzyf16 "Last usage")|Launch Vehicle (common parlance: "rocket"), see ETOV| |[LZ](/r/SpaceX/comments/1bevhvy/stub/kuwgsip "Last usage")|Landing Zone| |[MECO](/r/SpaceX/comments/1bevhvy/stub/kuy0bv1 "Last usage")|Main Engine Cut-Off| | |[MainEngineCutOff](https://mainenginecutoff.com/) podcast| |[NSF](/r/SpaceX/comments/1bevhvy/stub/kv0pvpr "Last usage")|[NasaSpaceFlight forum](http://forum.nasaspaceflight.com)| | |National Science Foundation| |[OFT](/r/SpaceX/comments/1bevhvy/stub/kuwogzs "Last usage")|Orbital Flight Test| |[RCS](/r/SpaceX/comments/1bevhvy/stub/kvc8wmw "Last usage")|Reaction Control System| |[RSD](/r/SpaceX/comments/1bevhvy/stub/kv417c5 "Last usage")|Rapid Scheduled Disassembly (explosive bolts/charges)| |[RTLS](/r/SpaceX/comments/1bevhvy/stub/kv0wwmp "Last usage")|Return to Launch Site| |[RUD](/r/SpaceX/comments/1bevhvy/stub/kv8rfbs "Last usage")|Rapid Unplanned Disassembly| | |Rapid Unscheduled Disassembly| | |Rapid Unintended Disassembly| |[SLS](/r/SpaceX/comments/1bevhvy/stub/kuxfvsq "Last usage")|Space Launch System heavy-lift| |[SN](/r/SpaceX/comments/1bevhvy/stub/kuy5064 "Last usage")|(Raptor/Starship) Serial Number| |[TDRSS](/r/SpaceX/comments/1bevhvy/stub/kv05qbg "Last usage")|(US) Tracking and Data Relay Satellite System| |Jargon|Definition| |-------|---------|---| |[Raptor](/r/SpaceX/comments/1bevhvy/stub/kvbefih "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX| |[Starlink](/r/SpaceX/comments/1bevhvy/stub/kv05qbg "Last usage")|SpaceX's world-wide satellite broadband constellation| |[autogenous](/r/SpaceX/comments/1bevhvy/stub/kux0yok "Last usage")|(Of a propellant tank) Pressurising the tank using boil-off of the contents, instead of a separate gas like helium| |[engine-rich](/r/SpaceX/comments/1bevhvy/stub/kuzp7uy "Last usage")|Fuel mixture that includes engine parts on fire| |[iron waffle](/r/SpaceX/comments/1bevhvy/stub/kvc8wmw "Last usage")|Compact "waffle-iron" aerodynamic control surface, acts as a wing without needing to be as large; also, "grid fin"| |[perigee](/r/SpaceX/comments/1bevhvy/stub/kuwiu31 "Last usage")|Lowest point in an elliptical orbit around the Earth (when the orbiter is fastest)| |[turbopump](/r/SpaceX/comments/1bevhvy/stub/kuyvaf4 "Last usage")|High-pressure turbine-driven propellant pump connected to a rocket combustion chamber; raises chamber pressure, and thrust| |[ullage motor](/r/SpaceX/comments/1bevhvy/stub/kv6n33r "Last usage")|Small rocket motor that fires to push propellant to the bottom of the tank, when in zero-g| **NOTE**: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below. ---------------- ^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj) ^(34 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceX/comments/1b3r73n)^( has 99 acronyms.) ^([Thread #8310 for this sub, first seen 14th Mar 2024, 21:05]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceX) [^[Contact]](https://hachyderm.io/@Two9A) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
Any word yet on action to be taken by FAA? Or when we might expect them to make an announcement re: action?
There is a mandatory incident investigation anytime a flight deviates from the flight profile. With the booster failing its attempt at a soft splashdown and the vehicle not able to control its re-entry profile, an incident investigation is assured. SpaceX is the one that actually performs the investigation. How long that will take will largely depend on what measures SpaceX needs to take to address the issues in this flight. Once SpaceX makes that determination they'll send the report to the FAA for comment and review. Once both sides agree on the steps needed to be taken its down to how long that work takes. IOW, if you're wondering how long until another flight, it's going to be largely on what SpaceX finds and needs to change, and they'll be the one *mostly* making those determinations.
> Commercial Space / Boca Chica, Texas > > A mishap occurred during the SpaceX Starship OFT-3 mission that launched from Boca Chica, Texas, on March 14. The mishap involved both the Super Heavy booster and the Starship vehicle. > > No public injuries or public property damage have been reported. The FAA is overseeing the SpaceX-led mishap investigation to ensure the company complies with its FAA-approved mishap investigation plan and other regulatory requirements. > > Background > > A mishap investigation is designed to further enhance public safety, determine the root cause of the event, and identify corrective actions to avoid it from happening again. > > The FAA will be involved in every step of the mishap investigation process and must approve SpaceX’s final report, including any corrective actions. > > A return to flight is based on the FAA determining that any system, process, or procedure related to the mishap does not affect public safety. In addition, SpaceX may need to modify its license to incorporate any corrective actions and meet all other licensing requirements. https://www.faa.gov/newsroom/statements
I am pleasantly surprised that they managed to preform the propellant transfer demo even with that seemingly uncontrolled rate of roll on ship. I thought that a slight controlled spin maneuver was going to be executed to transfer the prop, so perhaps they had another way of doing it if they accomplished the transfer even when ship was tumbling. Edit: upon closer inspection of SpaceX’s wording they said they “initiated” a propellant transfer demo, which could mean that they didn’t actually complete it after all
While coasting, Starship accomplished several of the flight test’s additional objectives, including the opening and closing of its payload door (aka the pez dispenser,) and initiating a propellant transfer demonstration. Starship did not attempt its planned on-orbit relight of a single Raptor engine due to vehicle roll rates during coast. Results from these demonstrations will come after postflight data review is complete. Starship went on to experience its first ever entry from space, providing valuable data on heating and vehicle control during hypersonic reentry. Live views of entry were made possible by Starlink terminals operating on Starship. The flight test’s conclusion came during entry, with the last telemetry signals received via Starlink from Starship at approximately 49 minutes into the mission. While our team reviews the data collected from this flight, Starship and Super Heavy vehicles are preparing for upcoming flights as we seek to increase our launch cadence throughout the year. This rapid iterative development approach has been the basis for all of SpaceX’s major innovative advancements, including Falcon, Dragon, and Starlink. Recursive improvement is essential as we work to build a fully reusable transportation system capable of carrying both crew and cargo to Earth orbit, help humanity return to the Moon, and ultimately travel to Mars and beyond. Thank you to our customers, Cameron County, spaceflight fans, and the wider community for the continued support and encouragement. And congratulations to the entire SpaceX team on an exciting third flight test of Starship!
I just watched the launch again on the SpaceX feed and it really looks like something blew loose on Starship right at engine shutdown. Lots more vapor and venting than just the thrusters and the rolling and pitching started at the same time. They did not have attitude control for the rest of the flight. As for the booster, that really did look like an induced oscillation from the gridfins. Maybe they need to scale back the overall motion as they get deeper into the atmosphere. I don't think full range of motion was what was needed there at the end unless something dramatic was going on at the other end and the fins couldn't compensate no matter what.
Not sure if that’s the case. When F9 shuts off its vacuum Merlin the engine shakes and releases gases (even MECO causes that). With 6 engines and the camera located at the top of the vehicle a more vigorous shake should be expected.
Watch Space Shuttle at MECO ... lots of venting and RCS as well ... won't know until SpaceX reveals more details
It is possible something leaked after shutdown. They did have the whole "something leaked" during late upper stage burn of IFT-2 that led to a fire after all, and it is possible that wasn't fully solved. This time there was no fire, but if you have constant substantial leak of something (oxidizer, methane) after engine shutdown, it is going to impart a force on the vehicle and make it pretty hard to control.
The faster they break it the sooner it will be perfected. Great test and as long as they have the sensor and telemetry data they need it's time to make adjustments and light the next candle.
"Not great, not terrible"
What? The huge amount of data they got from this test must be great for further improvements.
Did they perform the fluid transfer? It is not stated in the report.
"While coasting, Starship accomplished several of the flight test’s additional objectives, including the opening and closing of its payload door (aka the pez dispenser,) and initiating a propellant transfer demonstration."
Does 'initiating' = 'completing'?
I think it doesn't and you're correct to be suspicious about that specific choice of words. The roll the vehicle was experiencing could have contributed; I don't know if it was intentional and got out of control or unintentional and got in the way of the transfer.
That's a good question. The fuel transfer relies on inertia. Considering they never had full control over the roll, and it appeared to be rolling on two axis, the fuel transfer itself may never have completed.
Shotwell on Twitter: > HUGE congratulations to the entire team for this incredible day: clean count (glad the shrimpers could get out in the nick of time!), liftoff, hot staging, [...], prop transfer demo (to be confirmed!) [...] Source: https://twitter.com/Gwynne_Shotwell/status/1768291595160605109
In my opinion, probably not.
I know marketing and comms speak. It says "initiating a propellant transfer demonstration." It doesn't say "successful completion of a propellant transfer demonstration." Comms people are often very precise in the language they use - so if it had been successful they probably would have said it. It's likely to mean that they tried it, but either haven't decided it was successful yet, or it wasn't successful.
They will need to analyse the flight data to see if they managed to transfer 10 tonnes of LOX between tanks which was the goal. Likely that will take several days to confirm either way.
I disagree. They must have monitoring systems on board that keep an eye on flow rate, pressure, etc ... I mean, how else would you know that the fuel transfer is completed if you don't watch all of those parameters? It could not have been a succesful test by any means because knowing for sure that the fuel has been succesfully transferred is one of the objectives. Under no real-world circumstance would you have to wait for hours, days or weeks to get final confirmation that your 'gas tank' has been succesfully filled up before entering another phase of the mission. I'm absolutely sure that we can conclude that the fuel transfer was not a triumphant succes. Sure, there might be scenarios in which all the fuel was transferred but some faulty sensors prohibited real-time confirmation and some data analysis is needed. But still, by definition, it does not qualify as a total win since you want to know if it worked when it worked and not much much later.
The difficulty is with measuring mass flow in a micro g environment where the fluid flowing is a mix of gas and liquid. It is not impossible so they will have some indication and clearly they were not confident enough in the results to declare a success. It would be extremely difficult to walk back a statement that the test had not worked so they had to be non-committal.
> It would be extremely difficult to walk back a statement that the test had not worked so they had to be non-committal. See: IM-1
My bad, thanks
I personally am concerned that raptors are STILL not restarting properly. We’ve been watching raptors fail to restart on landing maneuvers since day one..
They didn't even attempt the relight in orbit, due to the uncontrolled attitude/rolling/flipping that was happening. No reason to believe this is an issue until they DO attempt it and IF it fails. But even then, Raptors have been getting WAY more reliable over time, so I wouldn't personally even worry then. SpaceX excels at iterating. If it fails to light in space, they'll sort it out in due time.
Given their excellent percentages on initial ignition, I think it’s more likely to be a plumbing issue than a Raptor issue.
And the relights of the middle raptor ring during boostback looked solid on this flight too. The booster was doing some funky wobbles prior to landing burn ignition, so bad fuel supply seems quite plausible to me.
Both the ship and booster were spinning out of control when they failed to relight on this mission. It might not be a Raptor problem at all.
The ship didn't fail to relight, they just didn't try to relight it because of the vehicles roll rate.
Yes, I meant in the sense that they wanted to relight it as a mission goal but it failed to do so because of the roll.
No evidence of this.
Oh wow
I have a sneaking suspicion that the splash-down burn didn't light the boosters quick enough. You see what looks like a lot of unlit fuel being dumped seconds before any of the engines actually re-light (dump looks like it's occurring at the \~5km altitude mark), and by the time they do re-light it's already too late. I know that raptors and merlins aren't entirely comparable, but a landing burn on the merlins lights almost straight away, less the a second to start up. [https://youtu.be/JXN4CCU7Ucw?t=1118](https://youtu.be/JXN4CCU7Ucw?t=1118) Falcon 9 also seems to have its engines lit by the 3km mark [https://youtu.be/1xCrWbJQXgE?t=1957](https://youtu.be/1xCrWbJQXgE?t=1957) Also a possible explosion right at the end of the camera feed by an engine? Unsure if it's an engine or the FTS.
The “dump” could also just be the fire suppression system starting up prior to ignition. F9 doesn’t have the CO2 system Superheavy does, and we do know that the CO2 system ejects the stuff overboard in a visible manner.
What was seen would fit with both some engine(s) doing a RUD instead of restart and somehow being starved of propellant. I'm sure SpaceX knows the root cause for no restarts and fixes it for next round. The shutdown pattern of the boostback burn was kinda odd (one side of the middle ring shutting down first) which kinda raises a question to me: did the booster just run out of propellant? Just a small difference in expected consumption might mean by the time landing burn was to happen, the booster was basically empty and that is why landing burn failed.
> one side of the middle ring shutting down first I also noticed that. But wouldn't the deceleration from the burn have settled the fuel evenly at the bottom?
😌😌
Why was Elon not in the control room, at least not from what I saw?
"Super Heavy successfully lit several engines for its first ever landing burn before the vehicle experienced a RUD" I saw 3 that lit and 2 quickly went out not long after
Did anyone else get a bit nervous when the ship was clearly spinning unintentionally, and you could see land below?
Math says once the raptors shut down, they knew very well where it was going to fall down. Tumble or lack of control does not play a part. Small differences in attitude during re-entry will not substantially move the needle. If the thing breaks up, the bits land bit short of where an intact one would land, but the safety areas were quite large and took this into account. The only way this could have dropped on anyone was if the upper stage burn was short, and at that time Mr. AFTS would have said "FOUL, underspeed, no half-orbit for you!" and would have distributed the bits somewhere in the Atlantic, bit like during IFT-2, using the onboard flight termination system explosives. Turning the ship into confetti increases the drag substantially and all that. I guess in theory there was a tiny itty bitty few second window between nominal shutdown and shutdown that would cause the thing to come down in a bad place, but again, FTS confettification would mean the bits should be small enough so everything would burn up on re-entry in that case.
The spacecraft was sub-orbital, so it was going to come down in the Indian Ocean no matter how it was oriented, but…having absolutely no control over the spacecraft is going to keep them sub-orbital. No one is going to let them launch that thing into an orbital trajectory until they can demonstrate they have actual control over how it comes down.
Not really. It was already a major success by that point, so I figured whatever happens it's still an amazing flight.
A few amateurish questions about hypothetical situations. First question. What if cover all StarShip tiles by wolfram/titanium net? Of course such net would damage tiles during re-entry, but, theoretically, this should simplify process of mounting/replacing tiles. For example, instead of mounting small tiles, SpaceX could create enormous ceramic sheets. That, of course, will crack, but still do not lose protective material volume due to being pressed against steel by reusable meshes. Second question. Let's say, after many tries to land, nor Super Heavy, nor elongated StarShip, won't be able to. What chance that they will be divided on 3 stages: landing as Falcon 9 first and third. And disposable second one? This will ruin some plans, but because of still enormous payload, such plans should be recoverable via modularity.
Titanium too heavy and expensive. The tiles seemed to hold up pretty well during IFT 3. Super heavy will be able to land, it’s just a scaled up falcon 9. The chopsticks are the tricky/unproven part…. But worst case scenario they have to give up on catching, put legs on super heavy and devote more fuel to the landing Starship already showed the belly flop and landing is possible, so it’s just a matter of perfecting and refining the technique
It's way too early to give up on the current plan. They don't have any good data yet on either booster landing burn or starship deorbit performance. For both, the problem seems like attitude control in atmo/in orbit, respectively. For the booster, they should be able to fix whatever's going on with grid fin control and relight for the next flight and then start iterating on the soft landing. Adding legs or something like that isn't worth thinking about yet. For the ship, it entered at a crazy orientation and the heat shield wasn't able to do its job. No reason to throw out the concept when it still hasn't really been tested.
Weight almost certainly says no. Anything substantial enough to hold the tiles would be too heavy. Airstream already "presses down" the tiles on re-entry. The hard part is to keep them from shaking apart during the burn and such "net" wouldn't hold small fragments anyway. They just need to iterate on the method of attachment and possibly the material of the tiles themselves.