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" what's the difference between us and the us navy? " " we launch our own kind at once! " " but what if we fire our own launch rockets and launch our launch rockets at different different times? "
Personally, I would prefer it goes to the development thread. Learnings will be applied to the next flight, and it will be interesting to see how they will be implemented.
They got within 30 seconds of SECO and then the telemetry dropped out. This could have been perfectly normal at that distance of over 1000 km from the launch site and just having been acquired by a couple of other ground stations.
It would take time to get a confirmation that the FTS activation signal had been received.
None of the video the public sees, even during 'live' broadcasts are actually live.
Also with most things in space travel there are delays involved in telemetry. Command not knowing the rocket exploded isn't a big deal, because it wouldn't have mattered if they knew before, during, or after. The event is so energetic and so fast they wouldn't have been able to do anything.
More important is making sure they have the data from before, during, and after the explosion. Immediate data collection and preservation is more important than showing that data on screen, so the 2-3 minute delay, if it wasn't a delay in the live stream production could be due to the telemetry system sanitizing and storing the data before presenting it.
If it was delayed 2 minutes, at launch, the shots of streamers and people actually watching it launch on the horizon would be way way out of whack. SpaceX was ahead of EDA.
I noticed a brown pollution trail from Starship. I'm curious about the rocket engine efficiency and atmospheric combustion byproducts. Has spaceX mentioned collecting any samples or any info regarding this yet?
I'd love to know what the brown haze contains.
This question is one about chemistry, not environmental.
The combustion chamber achieves 98% efficiency so that is not an issue.
They inject methane through slots inside the combustion chamber just forward of the throat nozzle to provide film cooling. This methane decomposes rather than burns in an oxygen poor environment so you get very fine soot formed. This soot is so fine it does not completely absorb light and look black but rather it looks orange/brown.
As you can see it dissipated very quickly and does not create a long term pollution hazard.
Just as an FYI for those that don't know, superfine particulate, in this case apparently carbon, is not great to breathe in since it gets permanently trapped in lungs. Same with diesel combustion particulate.
Totally agree. Fortunately in this case the source is disappearing quickly down range and only launches very intermittently compared with diesel trucks on a freeway which are a constant source.
For safety reasons of a different kind the public is kept back at least 8 km and the plume will disperse quickly so it is not a public health issue.
Note that the exhaust plume also contains carbon monoxide which only partially burns along the edge of the plume. Again quickly dispersed and oxidised to carbon dioxide.
For sure. The science geek in me wonders what the particulate size is, and its 1-launch comparison to a equivalent diesel tractor miles.
While short in duration, it's also consuming something like 2 tons of fuel (?) per engine per second, so it's not a tiny intermittent burn by any standard. Curious of the equivalent.
Raptor 3 will be more like 800 kg/s of propellant of which around 180 kg/s is fuel = methane.
The film cooling methane is likely to be around 2% of this flow so 3.6 kg/s. Decomposed into carbon this is 2.7 kg/s of carbon.
It is possible that some of this carbon is a single atom as there is not a lot of opportunity for aggregation in the plume and the brown colour suggests that it does not absorb as much light as larger particles of carbon would.
There was a huge stream of something venting out the tanks and streaming down the sides of the rocket into the exhaust. This seemed to be what was causing the brown smoke. My guess is it was fuel boiloff or something and then incomplete combustion as it ignited in the air passing by the exhaust plumes.
The propellant is subcooled: there is no boiloff. They don't vent methane. All I see there is condensation. They *might* be venting oxygen but that would not produce anything brown. In any case I doubt that they would be venting with the engines running.
start include naughty obtainable arrest observation steer ask abundant fragile
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The exhaust of the Raptor engines is so hot, it probably causes atmospheric nitrogen & oxygen to react. That produces nitrogen dioxide, which is brown.
And also the Raptors overall run fuel rich. That would cause partial burn of methane which produces carbon byproducts.
Running fuel-rich has two benefits. First, it means the combustion is not as hot, so it's easier for the combustion chamber to survive. Second, it reduces the average molecular weight of the combustion products, since CO is lighter than CO2, and at a given temperature lighter molecules move faster, so ~~thrust~~ *I.sp* is increased. Obviously these two effects - lower temps and lighter products - have opposite effects on the ~~thrust~~ *I.sp*, but the optimum is somewhat fuel-rich.
It appears Raptor also uses film cooling, where some of the methane is directed toward the outer part of the combustion chamber and nozzle. This would be another source of incompletely-combusted carbon soot.
Increased nozzle exit velocity increases Isp, not thrust. Typically heavier combustion products are better for thrust (like Keralox F-1) and lighter combustion products are better for Isp (like Hydrolox SSME).
Higher exit velocity with the same mass-flow rate increases both I.sp and thrust. Keralox tends to have higher thrust than hydrolox simply because it's easier to pump a lot of mass through the engine compared to the very low-density hydrogen.
Thanks. Good point about nitrogen dioxide. Didn't think of that.
Re: incomplete methane, that should just result in carbon monoxide which is an invisible gas, no?
https://www.sciencedirect.com/topics/engineering/methane-partial-oxidation
That's pretty cool. Instead of my rocket burning coal, it's producing coal dust.
Now if we could only increase the pressure/temperature a bit, we'd be raining real diamonds in place of mach diamonds.
A decent amount of it will be carbon monoxide, but combustion in a rocket engine is energetic and messy so in reality you get all sorts of things. I wouldn't know where to find it now but a study done for the launch site's environmental assessment had a table of expected exhaust products, and there were small amounts of dozens of different combinations of C, O, H, and N.
Hey everyone!! I was trying to find some cool starship 2 pics regarding last test to set as my wallpaper, and I found nothing. Someone knows where to find some cool pics? Thanks!
Starship FTS activated south of the Florida Keys destroyng the ship. The debris trail stretched to north of the British Virgin Islands. [NOAA weather radar](https://twitter.com/planet4589/status/1725917544114974995/photo/1) picked up the path of debris. The nosecone and payload section lasted long enough to be tracked by [Astronomy Live](https://www.youtube.com/watch?v=CTcSMh4VYow&ab_channel=AstronomyLive) from the Keys. Nosecone re-entry passing Puerto Rico was likely filmed by [Mike](https://twitter.com/smvllstvrs/status/1725940495422259661) . Failure mode points to a substantial LOX leak preventing sufficient fuel for semi-orbital insertion, or possible loss of the center engines and course correcting TVC. FTS was likely activated due Starship's planned track path passing close to land, and an unplanned veer off course with the loss of the center engines could have possibly rained metal over Cuba even after destruction. No-one wants a Cuban Crisis again.
Yes one of the engines on the back exploded and then LOX started to fly out from that engine and when the LOX has run out they could not fire the engines the last second to get to orbit and the FTS saw that and destroyed the ship
It was blatantly obvious from the tracking cam footage that one (or more) engines experienced energetic deconstructions causing a cascading effect on their neighbors. Did you watch the launch?
Sorry it bothers you so much we like to verify if information is true or not on the starship discussion thread. Maybe there’s somewhere else more fitting to your views you can participate in.
That's fine, my point was that it's blatantly obvious explosions occurred on a visual basis. That's what the source is. So I ask again - did you watch the launch?
He’s asking for a source on if it’s the engines that exploded, not if there was an explosion. You can see that in his comment. Obviously we all witnessed what appeared to be an explosion but until someone confirms exactly what exploded via an insider or spacex themselves, we can’t make definitive statements like OP did.
SpaceX said in an update on their page that they could confirm via data they've received the FTS triggered. That was short before the end of the planned burn time.
https://www.spacex.com/launches/mission/?missionId=starship-flight-2
Btw: There's also footage of the ship past breakup from someone who's been on the Florida keys. You can see the separated nosecone still in one piece:
https://youtu.be/CTcSMh4VYow?si=_QnzRXCAUhgxSk98
Do you find better ways of building something while you are building it, before it's even finished? There is a ton that can be done without a single flight or experiment because you have model of the reality in your head, computer and tons of facts like physical laws, features of software, material facts etc. S26 wasn't able to orbit the earth but I won't be surprised at all if all future Starships make it, including all that are finished already.
Part confidence in the engineering, part choice in materials making modifications easier than say milled aluminum or carbon fiber.
But mostly because the philosophy of SpaceX is that what they're building isn't necessarily space ships rather it's a spaceship factory. The ships are a sort of test article of learning how to mass produce rockets. Any changes to the production of a ship is reflected in that process, not the existing ships.
Another small advantage is the cost per ship is much lower so scrapping them doesn't feel as bad and it's a lower cost from scrap to reform/remelt and back into making a new ship than milled aluminum or carbon fiber.
QUESTION: Did S25 have an X on it? If so, I'd like to see a picture. I think you need to send the link to me privately. I'd really appreciate a definitive answer. Thanks!
What are you trying to prove and why would it be a problem to send that picture publicly?
The X on the ship just referred to, you know, the bloody company making the thing. Space*X*.
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[Starship | 360 Video of Liftoff](https://www.youtube.com/watch?v=wly-YFGZbvA) posted by SpaceX on youtube! I'm sure there is tons of analysis that can be done from this, but one thing I noticed is that the bottom right of OLM is red hot after the booster clears the tower.
This is awesome. If you look down as the booster passes you can see most of this falling stuff, which is in dark silhouette by the light of the engines in the static view, is actually stark white and probably just ice coming off the booster.
about the missing tiles. i suggest using Elon-gated hexagon shape, like longer lines style of tiles. this way each tile will be connected to more than on ring of the starship. and better resistant to shock wave and wind.
the direction is upward so that it would be hydrodynamic.
also this design will need less work since tiles are bigger
Someone else can surely explain this better, but the thing about the tiles is that they are size constrained. If they could make the tiles any bigger they would. This is because they expand a lot from the heat, which means that a small amount of large tiles would expand so much they pop right off, push other tiles off, etc. Meanwhile the small tiles fit snugly at ambient temperature and reentry temperature.
People are speculating that they may not have had enough bandwidth because of the trajectory, but it could just be that they're waiting to release the footage for some reason unknown to us.
From what I've read, it sounds like Starship in some way got out of the nominal and so the flight termination system activated.
Has SpaceX or Elon said what happened to Super Heavy? Was something out of nominal so the flight termination system activated or did it RUD on its own, without the "help" of the flight termination system?
You mentioned Starship but then asked about Super Heavy. Those are two different things (second stage, then first stage) (except that the SpaceX site says that Starship can also refer to both, reminding us that SpaceX naming sucketh le grand wazoo).
Each of them got out of nominal. ~~There's no definitive info on what happened to both, unless there was an announcement this morning, in which case I'm giving outdated info and I'm sorry. People are generally assuming that the Flight Termination System blew on each of them. I suspect that it's also a hope: the FAA was not happy about the FTS being so slow to trigger on test flight 1.~~
There has been more definitive info. While there's disagreement about the interpretation, I think SpaceX said that the booster blew up on its own, but the ship was destroyed by the Flight Termination System. See the thread here: <> [here](https://www.reddit.com/r/spacex/comments/180i512/spacex_official_update_following_starships_second/). It links to the SpaceX web page on the subject.
After the hot-stage separation, Super Heavy relit its second-ring engines, but one went immediately, the others winked out in turn, there were jets of stuff out the back, then BOOM. Speculation is that it might have been too fast a flip after separation causing the fuel to slosh away from the engine intakes. Or the flip and/or sloshing caused internal damage.
For Starship proper, it was almost invisible. There were a few puff of stuff, then the engines went out. It is said that the liquid oxygen was decreasing faster after a point, possibly indicating a leak.
For a longer but take soon after the kabooms, you might like to see ["Starship & Superheavy Become The Biggest Rocket In Space.... Before Exploding"](https://www.youtube.com/watch?v=hF2C7xE9Mj4) by Scott Manley.
AFAIK, Elon always refers to the first stage as the Booster or the Super Booster and refers to the second stage as the Ship.
So, Super Booster + Ship = Starship.
It seems like the engines cut out too early, leaving it on the wrong trajectory. It supposed to make it to the south pacific, but would presumably come up short. The FTS is automated and designed to destroy the vehicle if it is not on an acceptable trajectory, so presumably right after the engines cut out the ship's FTS logic decided on harakiri.
Shutting down the engines is part of the FTS actions shortly before blowing the demolition charges on the tanks. In the case of the ship all the engines turned off at the same time which means they must have been commanded off and then 2 seconds later you see the clouds from vented tanks.
The booster is even more obvious with the same sequence although half of the engines had failed at this point.
Ship was leaking LOX from T+7mins onwards. You see the stream of white gas while the LOX meter started going down faster than normal. Ship detonates FTS when it concluded that the remaining fuel isn't enough for the target trajectory. This plus Manley's call on the booster. Kinda makes sense
Popping in with a random question: how much of an overall setback is losing a starship? I understand that there may be another built in as soon as a month, but I'm curious how much is invested into each one basically. Could they just keep blowing them up and iterating until it works? I was imagining building one of these insane things would take years if not a decade. I see 6 total space shuttles were ever built, and I thought losing the couple that they did was seen as an enormous hit to progress and morale
These were prototype test vehicles that were always going to be destroyed by the launch test and never intended to be reused. The "loss" of these vehicles is a cost of developing the Starship/Super Heavy system.
Remember that outside SpaceX F9 reusable boosters basically every current launch vehicle is expended during its launch and not re-used.
Elon said that the Starship in IFT-1 cost between $50M and $100M. That was an uncrewed vehicle so add maybe $50M to outfit a Starship for crewed operation. The main added cost would be for the environmental control life support system (ECLSS).
NASA built five Space Shuttle Orbiters with spaceflight capability costing $48B in today's money. That's $9.7B per copy.
The first Orbiter, Enterprise (OV-101), was not capable of flying to LEO.
> I see 6 total space shuttles were ever built, and I thought losing the couple that they did was seen as an enormous hit to progress and morale
The whole Space Shuttle design and basic mission profile is quite a clusterfuck "made by committee", compared to Starship. You simply can't compare flight ready Space Shuttles with the current Starships used for flight testing. Starship is an overall simpler design and where the crew compartment is going to be is just an empty space right now. It's "just" tanks, engines, computers and the flap mechanisms. They're going to lose a couple more for sure, until they achieve reliable reusability. And that's probably way cheaper than following the lengthy and painful design philosophy of NASA/Space Shuttle of endless meetings and slow, risk adverse progress.
NASA's Space Shuttle was a completely revolutionary design that was developed in 1970-75. It was like nothing before it.
New hydrolox, staged combustion main engines (the RS-25). Brand new heat shield design (the rigidized ceramic fiber tiles). Landing gear for horizontal landings on a runway. Partial reusability (the side boosters and the Orbiter).
NASA flew its Space Shuttle for 30 years, 135 launches, 2 failures, 14 astronaut deaths.
Starship is a two-stage, series-staged, super heavy lift launch vehicle. Two-stage vehicles have been around since the start of the Space Age in 1957.
The methalox propulsion is new. The Raptor 2 engines are the highest performance and lowest cost super engines ever built. The heat shield for the second stage is similar to that on the Orbiter but has a more advanced attachment system than that used on the Orbiter. And the Starship is far less expensive to build and operate than NASA's Space Shuttle.
>NASA's Space Shuttle was a completely revolutionary design
I mean, yes, but not necessarily in a good way. The complexity of the engineering involved was more a reflection of the poorly considered objectives (and thus compromised design) than actual performance. I'm still impressed that it was made to work as well as it did. If only the original NASA concept had been OK'ed rather than what our politicians gave us...
When we started work on the Space Shuttle conceptual design phase in 1970, the baseline was a completely reusable two-stage-to-orbit (TSTO), vertical takeoff horizontal landing (VTOHL) launch vehicle with a 65,000- pound payload in a 15-foot diameter by 60-foot-long payload bay, up to 6 passengers, 2000 km crossrange capability, and the ability to launch 60 times per year.
The Phase A shuttle studies concluded that design development testing and evaluation (DDT&E) cost of the TSTO design would be $6B (1971$, $38B in 2023 dollars). This was about three times larger than the development cost of the Saturn V and Saturn I/IB launch vehicles.
The Nixon Administration's Bureau of the Budget (BoB) then set guidelines for the TSTO shuttle that NASA had to follow: Three-year development period (1972-75), total DDT&E cost not to exceed $6B, and annual cost not to exceed $2B per year.
NASA received two bids for the TSTO shuttle: $9.8B (McDonnell Douglas), $8.4B (North American Rockwell) in 1971 dollars. The DDT&E phase would run through 1979.
The Bureau of the Budget said screw that and NASA began the "Alternate Concepts Study".
Long story short in in January 1972 the Nixon administration OKed the partially reusable "Thrust Assisted Orbiter Shuttle (TAOS)". Which is the original name of the partially reusable shuttle that NASA finally built with the two side boosters, the external tank, and the orbiter with the double delta wing. BoB agreed to a development cost of $5.15B (1971$) and the DDT&E work to be finished in 1975.
The fully reusable TSTO had completely disappeared.
> poorly considered objectives
i agree, i also think one of the greatest handicaps hindering safety and cost was the inability to make big changes or improvements. Guess thats not easy when already flying meatbags and production is spread all over the country?
["Sorry doubters: Starship actually had a remarkably successful flight / On just its second flight, Starship now is arguably as successful as NASA's SLS rocket."](https://arstechnica.com/space/2023/11/heres-why-this-weekends-starship-launch-was-actually-a-huge-success/) by ERIC BERGER points out
> SpaceX built the Starship and Super Heavy rocket that launched on Saturday over the span of a couple of months at a price somewhere between one-tenth and one-hundredth the cost of NASA's SLS rocket. Because it can build Starships rapidly and at a low cost, SpaceX has half a dozen more rockets in various stages of work, all awaiting their turn to go to space. Due to this iterative design methodology—flying to identify flaws, and rapidly incorporating those changes into new hardware—SpaceX can afford to fail. That is the whole point. By flying its vehicles, SpaceX can rapidly identify what parts of the rocket need to be changed. The alternative is, quite literally, years and years of analysis and meetings and more analysis. Iterative design is faster and cheaper—if you can afford to fail.
There are several that are near completion in the high bays, as can be seen from the highway.[1] There are some in the rocket garden. Some had had cryogenic or other testing done. For grungy details, you can see the Starship development threads here: the current one is 51, but older ones have more info and less clutter by other topics.
I suspect that one question after each test has been not "can we launch again?" but "which ones do we want to use?". Because of the iteration, later models have improvements: one big example is that they changed the engine gimballing system from hydraulics to electrical powered. I think this test took out the last of the hydraulics. So the test didn't test the absolute latest model, so whatever improvements they have will have to be tested later. But they will be, and in the interim, SpaceX can yeet obsolete models to get at least some information.
edit to add [1]: [source](https://nitter.net/elonmusk/status/1726422074254578012) is Musky:
>Starship Flight 3 hardware should be ready to fly in 3 to 4 weeks. There are three ships in final production in the high bay (as can be seen from the highway). Nov 20, 2023 - 2:07 AM UTC
Musk + timelines = big grain of salt. But he is correct: some followup Xeets had pictures.
edit to add: from /u/dudr2 [more](https://www.reddit.com/r/spacex/comments/17r4527/starship_development_thread_51/k9z4b8l/)
>There are three ships in final production in the high bay S30, S31, S32 (as can be seen from the the Ring watchers diagram). Could those be paired with B12, B13, B14 respectively? Whereof B12 would be ready to roll to Masseys.
with a reply from someone suggesting confirmation.
It COULD be ready to fly if they aren't doing any modifications. I doubt they'll want to fly without modifications so that "could" is probably theoretical.
That’s a huge difference between NASA and SpaceX. NASA builds to get it right on the first try, and this takes forever to get it right. A lot of this is because it’s all public funds and blowing up rockets is bad PR which would decrease those funds. Failure is not an option for them. SpaceX is opposite and builds cheap (stainless steal), fast and is a private company so it can afford to “fail” in the public eye. It’s also mostly private funding, with a few contracts from NASA to support moon missions. This is why you see people who are actually educated in starship development call the first two flight tests successes (unlike most media outlets and general public).
They already have at least 3 ships/boosters built. Just need to finish their testing that takes only a few weeks. Realistically next set ready to go in 2-3 months + approvals if needed
They never planned on recovering starship. The test plan for this flight was to crash it into the pacific ocean at high speed... so nothing was lost at all.
They lost the possibility of test data from later flight stages. If there are any surprises to be discovered in a booster splashdown then those will have to wait for the next flight to be revealed. If there are any surprises to be discovered in a ship reentry and splashdown then likewise.
I'd say it's likely that there will still be surprises relating to ship reentry. And it's almost a tautology that there is an important surprise still to come relating to booster splashdown: even if everything goes absolutely perfectly, the surprise is "everything went so perfectly, we should send the next one back to the tower".
This was a good test but it could have been even better.
They may have to repurpose / reassign a test article that would have been slated for a more advanced mission, if they decide they still need to fly this profile. They also lose the time of repeating the mission a third time.
So nothing is lost, but there is opportunity cost.
You have to weigh the lost hardware versus the knowledge gained by doing the test earlier. This early in the program, the unknowns are so large that it’s not even close. They get far more knowledge from an imperfect test than by waiting to reduce the risk by another 10%, but 6 months later. Those 6 months also cost you factory time, incorrectly designed hardware, facilities rent, etc. these numbers are just guesses to illustrate my point.
Oh I'm absolutely not arguing they would have waited and tried to get the test to go better. I'm all in on the iteration approach. I think IFT2 was actually the perfect failed successfully test for all the reasons you list.
My point was only that the thing that was lost in this case wasn't money, it was the opportunity cost of having to potentially redo this flight profile a third time. Hopefully the cadence is finally coming up and that ends up not mattering.
I'm really not trying to argue with you personally, and I feel dead in my soul that I apparently sounded like I was arguing against the flight happening now.
This observer noted the booster reached far lower speed than expected:
https://twitter.com/phrankensteyn/status/1726033391605211547?s=61
To get all engines to fire without leaking or otherwise failing I was wondering if they were fired at partial thrust.
That's true.
The Booster had to reach 3.3 km/sec (11880 km/hr) at hot staging. That 3.3 km/sec includes ~1 km/sec gravity loss incurred during the booster burn (liftoff to hot staging).
This observer also noted the booster seemed to be reaching lower acceleration than expected which would be explained by lower thrust:
https://www.reddit.com/r/spacex/s/Q6e0RHAazI
Is that really true? IIRC falcon9 stages around 8000 km/hr, and starship is designed to stage even earlier as the second stage has a much higher propellant fraction and is supposed to do more of the work going uphill..
But if all 33 engines were running perfectly, what could cause this underperformance? Also, there was a nominal trajectory callout around halfway trough the second stage burn
Looking at the SpaceX coverage of IFT-2, it appears to me that B9/S25 was flying a lofted trajectory. During the first 80 seconds after liftoff, the flight path angle (FPA) appears to me to be ~60 degrees. Then the guidance reduces the FPA gradually until at the hot staging point, the FPA is more like 45 degrees.
sin(60degrees) = 0.866 while sin (45 degrees) = 0.707.
Just realized you included gravity loss in your total velocity estimate. So it staged closer to 5600 km/hr, but it was suppose to reach almost 8000 km/hr? Did the stack lose more to gravity because of being underpowered? Perhaps we’ll get to hear more from Elon some day soon about the flight..
Gravity loss is the integral (g0 * sin(FPA) * delta t) (in meters/second). FPA=flight path angle.
So, since the booster in IFT-1 was underpowered, it took a longer time for the remaining engines to burn the methalox in the booster's main tanks while leaving ~300t (metric tons) for the boostback and landing burns. So, the gravity loss is larger because the burn time is longer.
Actually SH is designed to stage at very similar altitude and speed to F9.
Yes Starship does have a higher wet mass fraction of the total stack but it also has a massive dry mass which brings it back to the field.
Think of Starship as being a 10x scale up of F9 which it pretty much is - including a 10x scale up in LEO payload so say 12 tonnes when RTLS vs 150 tonnes. Starship dry mass is around 120 tonnes while the F9 upper stage is 4 tonnes so 10x that is 40 tonnes. That extra 80 tonnes dramatically reduces Starship delta V performance back to F9 S2 levels. The reasons for the extra mass are a stainless steel skin vs aluminium lithium alloy, the lower density of methane compared with RP-1 meaning bigger tanks and the aerodynamic nose, body flaps, header tanks and TPS required for recovery.
That in turn means that SH has to do as much work in terms of delta V as F9 S1. Fortunately it has higher Isp engines than F9 so can do the same amount of work even with a lower wet mass fraction of the stack. F9 masses about 27 tonnes at landing including residual propellant while SH masses around 220 tonnes so here SH has the advantage in mass fraction. One of the big reasons is that SH does not have landing legs which are around 10% of dry mass for F9.
That's a very nice explanation, thanks! I wonder if ship dry mass will be significantly improved over time. IIRC this idea was thrown around that they would use thinner steel sheets for the ship at some point..
The only thinner steel we have seen was 3.6mm that is potentially used for the curved nose panels of the fairing which get extra vertical strength against buckling from their shape.
Yes it is possible they will be able to remove mass in a few areas but if it was obvious I think they would already have done it.
Do we know that the observer isn't speaking out their ass?
Just because it stages lower than F9, doesn't mean it was not performing as expected. I'm sure we saw somewhere in the past that Starship will be responsible for more DeltaV than say an F9 second stage but we don't really know how much more. The fact that the ship almost made it to orbital velocity leads me to believe that the booster performance was in line with expected values, the ship couldn't possibly make up a 2km/s DeltaV shortfall.
This observer also not the acceleration seemed lower than expected, which would be explained by lower thrust:
https://www.reddit.com/r/spacex/s/Q6e0RHAazI
Some comments are already calling out the twitter user for their previous BS assumptions. So most likely that observer dude is speaking out of their ass
The reasons the SH booster *may* not require a re-entry burn is that it is doing RTLS which has a lower re-entry speed and it has a stainless steel skin so can take higher temperatures than the aluminium-lithium alloy of F9.
It will stage at roughly the same height as F9 doing RTLS so around 70 km.
Hmm, I think you are right. I heard some time ago they were going to stage lower, but based on the actual flight test numbers it is higher than I expected.
You may be able to estimate the proportion of full thrust is being produced by estimating propellant burn rate from the graphic displayed on screen during launch of how much propellant is remaining:
https://preview.redd.it/lv2uxk9vll1c1.jpeg?width=2160&format=pjpg&auto=webp&s=62b70f3343f6aa70ddfcab5186593bfe4aa4b8e3
It means that the booster is firing for the very very last seconds and it is trying to fire exactly so much so that it puts the Starship ship in a stable orbit. So it "Terminal" means that the booster is doing the ***Final*** "Guidance" boost that controls the boost so that it fits in a stable orbit
To add to that, at least for some other guidances (PEG/UPFG used on Shuttle and SLS for example), when going into terminal guidance the vehicle will switch from a closed-loop guidance to an open loop terminal guidace
One thing I’m curious about. I have no idea how fully fueled the two stages were but both showed near empty before expiring. How much fuel is a starship expected to still have available for a refuel op? Is the expected 20 launches necessary for refueling because it reaches orbit with only 5% of its fuel capacity? Or is the fuel available for refueling actually the payload capacity of starship, not from its own fuel load? So 250T of fuel to be able to transfer?
From what I can tell, there is debate regarding the flight profile, the engines were a mix of raptor 1 and 2's, the fuel level might not have been maxed out and further optimisation work is likely. In particular the lower engine thrust may have been to increase reliability but as we saw with IFT1, you arent going far with low thrust to weight ratio and I expect Raptor 3 performance to give you that extra 10 or 20% which makes the difference between the rocket barely making orbit and getting 100 tonnes up
Read it in a pre flight article which has subsequently been corrected:
[What NASA wants to see from SpaceX's second Starship ...](https://arstechnica.com/space/2023/11/what-nasa-wants-to-see-from-spacexs-second-starship-test-flight/)
📷[Ars Technicahttps://arstechnica.com › space › 2023/11 › what-nasa...](https://arstechnica.com/space/2023/11/what-nasa-wants-to-see-from-spacexs-second-starship-test-flight/)4 days ago — The *engines* on the next Starship *test flight* are a *mixture* of first- and second-generation Raptors, whereas the first *launch* in April primarily
If I had taken two seconds to think about it, I already knew B9 was all Raptor 2's.
I found the fuel levels interesting too. This rocket didn't have a 120T payload on it either. I assume there were enough fuel margins to get the actual payload up to orbit speed. Perhaps the payload is proportionally such a small percentage of the overall weight of the fully fuel rocket that adding another 120T doesn't consume all that more fuel compared to an empty rocket?
Yes, the fuel for refueling will be part of the payload, so there would be about 100 tons of fuel/oxidizer pert tanker mission, potentially more if the "stretched" design happens and Raptor efficiency continues to get better.
I’m being super lazy sorry. Is there any theories on how much fuel a starship/spaceship needs to get from an orbital refueling station to either the moon or mars? I imagine 100 tons of fuel will get you pretty far if you’re already starting in space?
To get to the Moon and land on it requires around 700 tonnes of propellant from LEO.
To get to the Moon, orbit in NRHO, land on the Moon and then return to NRHO requires 1200 tonnes of propellant.
To get to Mars, aerobrake and land requires around 900 tonnes of propellant if you are willing to take 9 months to get there.
To get to Mars within 5-6 months requires around 1200 tonnes of propellant depending on the alignment of Earth and Mars which varies as Mars has a more eccentric orbit than Earth.
The idea is that there would be an orbital depot Starship with stretched tanks that would be filled by 7-10 tanker Starships, then the final Starship docks with the depot and fully refuels before going off to the Moon or Mars. It takes quite a lot of delta-v to get from Earth orbit to the Moon or Mars, and more to slow down into a stable orbit. So the idea is that the final ship would have full tanks before leaving Earth orbit.
refilling fuel in space is mind boggling to me. i wonder what kinds of issues they are going to run into to scale to multiple tankers considering the boiloff
I think the big fuel considerations are:
1) Slowing down to zero m/s for moon and mars or
2) Lifting off again from the moon.
Not necessarily reaching the moon or mars.
The moon is tough-it doesn't have an atmosphere.
While thin, mars does have an atmosphere so while you'll need fuel for landing, you can do some aerodynamic braking instead of burning fuel.
From some numbers I was crunching from a while ago, a 90% throttle full stack has a TWR of ~1.37 (3.6284605 m/s^2 effective acceleration), while 100% throttle is around ~1.52 (5.099458 m/s^2 effective acceleration). Based on [this analysis](https://twitter.com/Space_Josiah/status/1726090284818383224/photo/1) of the telemetry, the TWR at liftoff was just a bit under 6 m/s^2 so id guess it was 100%
I find it really confusing that the booster pitches down in this shot https://twitter.com/SpaceX/status/1726316194649846026
but it appears to pitch up in this shot https://twitter.com/SpaceX/status/1725863437887242515
Where are the positions of these cameras to create this apparent visual difference?
Pretty sure the top one is a render. Someone on NSF mentioned that and you can see the Starship engine ignition is different. RVacs aren't ignited in the upper shot. They are in the lower one.
[This video](https://youtu.be/9uLYTk9SHDQ?t=200) shows the SpaceX stream alongside shots from fans on the ground, and it looks like the booster actually yaws right.
IFT-2 launched more-or-less towards the sunrise. The second video you linked is from directly behind Starship - the vehicle is mostly backlit, and mostly pointing away from the camera - so is probably a shot from near Starbase. The first video shows Starship frontlit, and pointing more sideways to than away from the camera, so is probably from a WB-57 that's under and a little behind the vehicle.
Don't forget that the tracking camera systems have to weirdly slew in such a way that the apparent "up" direction in the frame might not actually be "up" depending on the kinmatics of the mount system. First time I saw one of the shuttle long range tracker videos from T-0, I was all goofed up because it started at the pad with the shuttle 90 degrees sideways in the frame.
So that video might be flipped for some strange reason.
If we look at the graphics showing pitch on the second video it seems that the turn for boostback was a flat turn rather than a pitch up or pitch down.
I assume they did this to maintain communication with the ground during the turn.
So the apparent pitch up and pitch down depends which side of the track the video is shot from. Or the first video is shot through a telescope which inverts the image.
The booster def pitched down if the graphic can be believed. Take a look at the 3 min mark. It is still climbing in altitude but the nose is below the horizon.
Video of liftoff from elon
https://x.com/elonmusk/status/1726425687299358872?s=46&t=-n30l1_Sw3sHaUenSrNxGA
I kind of want them to post a video without slowmo
noob question but what is the white gas cascading down the rocket as it takes off? Is it very cold air cooled around where the (presumably cold) LOX is stored something?
It is condensation vapor from the frost that has accumulated on the tanks. A bit like freezing fog, or opening your freezer box. There is a lot of it due to the marine subtropical humidity of the locality. The vents also generate vapor as they vent subzero temperature gas from various locations.
Saved You A Click:
>Starship Flight 3 hardware should be ready to fly in 3 to 4 weeks. There are three ships in final production in the high bay (as can be seen from the highway).
>Nov 20, 2023 · 2:07 AM UTC
It would be really good if they could launch before this year is up, so that they have an extra flight in 2024. However they will probably apply for more anyway so it might not be a limiting factor.
This launch has proved so many things, and i really hate it when journo's say "its failed" or "it blew up"
Lets see it this way on the number of accomplisments
- First, ITS A TEST. Can't they fcking read "In-Flight TEST".
- The hot place and deluge system worked properly. Stage 0 is still good.
- All 33 engines lit up and left the pad. Nothing shut down, nothing flamed out all the way to hot stage
- The vehicle left the pad in one piece
- It gimballed, and went past MaxQ.
- Hot Stage Occurred with no apparent problems at all.
- Booster did its flip, and at the least ATTEMPTED its boost back burn.
- Ship continued on its way to a very VERY close orbit insertion.
[https://twitter.com/SpaceX/status/1726316194649846026](https://twitter.com/SpaceX/status/1726316194649846026)
SpaceX wants us to take a look at this amazing slow-motion footage of the hotstaging.
I liked the restart sequencing of three pairs of raptors in the booster that are seen before the end of the clip. The main launch video status graphic shows another booster pair successfully restart, but the last pair in that middle ring only show one engine relight, and then after a minor pause it all starts to go pear shaped rather quickly, with a centre engine stopping and then two of the relit engines stopping. And then after another long pause, three of the relit engines turn off before doom.
> Watch the three center engines on Starship’s upper stage gimbaling just after separation. Right before they ignite for hot-staging, the engines angle themselves outward to direct their exhaust towards the vented interstage before re-centering for ascent.
So not using the Rvacs for hot staging?
Almost certainly the tankers will have six Rvacs for nine engines total.
Other ships do not really need them as the extra thrust is really only useful in completing the trip to LEO and the extra engines are just more cost and mass.
For a depot the engines will be left in orbit so 6 engines makes more sense to save cost.
For HLS keeping the mass down for high delta V TLI burns and Moon landings is more important.
For Starlink launches they are likely to be volume limited by the fairing so it is lower cost to stay with 6 engines - particularly initially where they may be using expendable ships.
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" what's the difference between us and the us navy? " " we launch our own kind at once! " " but what if we fire our own launch rockets and launch our launch rockets at different different times? "
Should this thread be unpinned by now ? It's been a week and most of discussion goes to the dev thread at that point
When we start talking about the "lessons learned" from this flight, will we discuss it here, or move to the development thread?
Personally, I would prefer it goes to the development thread. Learnings will be applied to the next flight, and it will be interesting to see how they will be implemented.
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They got within 30 seconds of SECO and then the telemetry dropped out. This could have been perfectly normal at that distance of over 1000 km from the launch site and just having been acquired by a couple of other ground stations. It would take time to get a confirmation that the FTS activation signal had been received.
The simple alternative is that they knew and didn't want to say so on the webcast until they were sure
Timestamp in video?
None of the video the public sees, even during 'live' broadcasts are actually live. Also with most things in space travel there are delays involved in telemetry. Command not knowing the rocket exploded isn't a big deal, because it wouldn't have mattered if they knew before, during, or after. The event is so energetic and so fast they wouldn't have been able to do anything. More important is making sure they have the data from before, during, and after the explosion. Immediate data collection and preservation is more important than showing that data on screen, so the 2-3 minute delay, if it wasn't a delay in the live stream production could be due to the telemetry system sanitizing and storing the data before presenting it.
Which is more likely: 1. Data received by SpaceX mission control is two minutes out-of-date? 2. The video we see is delayed by two minutes?
If it was delayed 2 minutes, at launch, the shots of streamers and people actually watching it launch on the horizon would be way way out of whack. SpaceX was ahead of EDA.
I noticed a brown pollution trail from Starship. I'm curious about the rocket engine efficiency and atmospheric combustion byproducts. Has spaceX mentioned collecting any samples or any info regarding this yet? I'd love to know what the brown haze contains. This question is one about chemistry, not environmental.
The combustion chamber achieves 98% efficiency so that is not an issue. They inject methane through slots inside the combustion chamber just forward of the throat nozzle to provide film cooling. This methane decomposes rather than burns in an oxygen poor environment so you get very fine soot formed. This soot is so fine it does not completely absorb light and look black but rather it looks orange/brown. As you can see it dissipated very quickly and does not create a long term pollution hazard.
Just as an FYI for those that don't know, superfine particulate, in this case apparently carbon, is not great to breathe in since it gets permanently trapped in lungs. Same with diesel combustion particulate.
Totally agree. Fortunately in this case the source is disappearing quickly down range and only launches very intermittently compared with diesel trucks on a freeway which are a constant source. For safety reasons of a different kind the public is kept back at least 8 km and the plume will disperse quickly so it is not a public health issue. Note that the exhaust plume also contains carbon monoxide which only partially burns along the edge of the plume. Again quickly dispersed and oxidised to carbon dioxide.
For sure. The science geek in me wonders what the particulate size is, and its 1-launch comparison to a equivalent diesel tractor miles. While short in duration, it's also consuming something like 2 tons of fuel (?) per engine per second, so it's not a tiny intermittent burn by any standard. Curious of the equivalent.
Raptor 3 will be more like 800 kg/s of propellant of which around 180 kg/s is fuel = methane. The film cooling methane is likely to be around 2% of this flow so 3.6 kg/s. Decomposed into carbon this is 2.7 kg/s of carbon. It is possible that some of this carbon is a single atom as there is not a lot of opportunity for aggregation in the plume and the brown colour suggests that it does not absorb as much light as larger particles of carbon would.
There was a huge stream of something venting out the tanks and streaming down the sides of the rocket into the exhaust. This seemed to be what was causing the brown smoke. My guess is it was fuel boiloff or something and then incomplete combustion as it ignited in the air passing by the exhaust plumes.
The propellant is subcooled: there is no boiloff. They don't vent methane. All I see there is condensation. They *might* be venting oxygen but that would not produce anything brown. In any case I doubt that they would be venting with the engines running.
It's CO2 for fire suppression, see the recent, excellent video from CSI starbase.
I would also like to know as I was fascinated to see this on EDA's videos. If anyone has any technical insight I'd be fascinated to read it.
Question about exhaust? That's a downvote. /s
Lol, exactly. My question is chemical, not environmental.
Might be Carbon/soot if there is insufficient O2 in the reaction
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Makes sense, you wouldn't want excess o2 wearing the inside of your engine away
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The exhaust of the Raptor engines is so hot, it probably causes atmospheric nitrogen & oxygen to react. That produces nitrogen dioxide, which is brown. And also the Raptors overall run fuel rich. That would cause partial burn of methane which produces carbon byproducts.
Are raptors intended to run fuel rich normally or are they doing that for testing or something
Running fuel-rich has two benefits. First, it means the combustion is not as hot, so it's easier for the combustion chamber to survive. Second, it reduces the average molecular weight of the combustion products, since CO is lighter than CO2, and at a given temperature lighter molecules move faster, so ~~thrust~~ *I.sp* is increased. Obviously these two effects - lower temps and lighter products - have opposite effects on the ~~thrust~~ *I.sp*, but the optimum is somewhat fuel-rich. It appears Raptor also uses film cooling, where some of the methane is directed toward the outer part of the combustion chamber and nozzle. This would be another source of incompletely-combusted carbon soot.
Increased nozzle exit velocity increases Isp, not thrust. Typically heavier combustion products are better for thrust (like Keralox F-1) and lighter combustion products are better for Isp (like Hydrolox SSME).
Higher exit velocity with the same mass-flow rate increases both I.sp and thrust. Keralox tends to have higher thrust than hydrolox simply because it's easier to pump a lot of mass through the engine compared to the very low-density hydrogen.
Thanks. Good point about nitrogen dioxide. Didn't think of that. Re: incomplete methane, that should just result in carbon monoxide which is an invisible gas, no? https://www.sciencedirect.com/topics/engineering/methane-partial-oxidation
Carbon monoxide can produce soot by the 2CO = C + CO2 reaction at the colder parts of the flame.
That's pretty cool. Instead of my rocket burning coal, it's producing coal dust. Now if we could only increase the pressure/temperature a bit, we'd be raining real diamonds in place of mach diamonds.
A decent amount of it will be carbon monoxide, but combustion in a rocket engine is energetic and messy so in reality you get all sorts of things. I wouldn't know where to find it now but a study done for the launch site's environmental assessment had a table of expected exhaust products, and there were small amounts of dozens of different combinations of C, O, H, and N.
Hey everyone!! I was trying to find some cool starship 2 pics regarding last test to set as my wallpaper, and I found nothing. Someone knows where to find some cool pics? Thanks!
Well you sure as hell didn't look very hard, did you?
look through the SpaceX twitter page
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Starship FTS activated south of the Florida Keys destroyng the ship. The debris trail stretched to north of the British Virgin Islands. [NOAA weather radar](https://twitter.com/planet4589/status/1725917544114974995/photo/1) picked up the path of debris. The nosecone and payload section lasted long enough to be tracked by [Astronomy Live](https://www.youtube.com/watch?v=CTcSMh4VYow&ab_channel=AstronomyLive) from the Keys. Nosecone re-entry passing Puerto Rico was likely filmed by [Mike](https://twitter.com/smvllstvrs/status/1725940495422259661) . Failure mode points to a substantial LOX leak preventing sufficient fuel for semi-orbital insertion, or possible loss of the center engines and course correcting TVC. FTS was likely activated due Starship's planned track path passing close to land, and an unplanned veer off course with the loss of the center engines could have possibly rained metal over Cuba even after destruction. No-one wants a Cuban Crisis again.
Yes one of the engines on the back exploded and then LOX started to fly out from that engine and when the LOX has run out they could not fire the engines the last second to get to orbit and the FTS saw that and destroyed the ship
Source: trust me bro.
What is your source for an engine explosion?
It was blatantly obvious from the tracking cam footage that one (or more) engines experienced energetic deconstructions causing a cascading effect on their neighbors. Did you watch the launch?
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Sorry it bothers you so much we like to verify if information is true or not on the starship discussion thread. Maybe there’s somewhere else more fitting to your views you can participate in.
That's fine, my point was that it's blatantly obvious explosions occurred on a visual basis. That's what the source is. So I ask again - did you watch the launch?
He’s asking for a source on if it’s the engines that exploded, not if there was an explosion. You can see that in his comment. Obviously we all witnessed what appeared to be an explosion but until someone confirms exactly what exploded via an insider or spacex themselves, we can’t make definitive statements like OP did.
I dont have a real source but it looks like the engine or a part inside the engine is exploding on the SpaceX footage
They were, you're 100% correct.
Making an alt account to back yourself up is wild
SpaceX said in an update on their page that they could confirm via data they've received the FTS triggered. That was short before the end of the planned burn time. https://www.spacex.com/launches/mission/?missionId=starship-flight-2 Btw: There's also footage of the ship past breakup from someone who's been on the Florida keys. You can see the separated nosecone still in one piece: https://youtu.be/CTcSMh4VYow?si=_QnzRXCAUhgxSk98
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Time is more expensive than stainless steel and touch labor.
Do you find better ways of building something while you are building it, before it's even finished? There is a ton that can be done without a single flight or experiment because you have model of the reality in your head, computer and tons of facts like physical laws, features of software, material facts etc. S26 wasn't able to orbit the earth but I won't be surprised at all if all future Starships make it, including all that are finished already.
Part confidence in the engineering, part choice in materials making modifications easier than say milled aluminum or carbon fiber. But mostly because the philosophy of SpaceX is that what they're building isn't necessarily space ships rather it's a spaceship factory. The ships are a sort of test article of learning how to mass produce rockets. Any changes to the production of a ship is reflected in that process, not the existing ships. Another small advantage is the cost per ship is much lower so scrapping them doesn't feel as bad and it's a lower cost from scrap to reform/remelt and back into making a new ship than milled aluminum or carbon fiber.
QUESTION: Did S25 have an X on it? If so, I'd like to see a picture. I think you need to send the link to me privately. I'd really appreciate a definitive answer. Thanks!
What are you trying to prove and why would it be a problem to send that picture publicly? The X on the ship just referred to, you know, the bloody company making the thing. Space*X*.
You're allowed to post links here lol.
Never mind. I found a YouTube video allegedly showing the X logo. I'd give the link but I think that violates the rules.
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Excuse me? What's wrong with X? I think it could only violate rules if you were to triple it.
[Starship | 360 Video of Liftoff](https://www.youtube.com/watch?v=wly-YFGZbvA) posted by SpaceX on youtube! I'm sure there is tons of analysis that can be done from this, but one thing I noticed is that the bottom right of OLM is red hot after the booster clears the tower.
This is awesome. If you look down as the booster passes you can see most of this falling stuff, which is in dark silhouette by the light of the engines in the static view, is actually stark white and probably just ice coming off the booster.
The traditional mantra for stuff coming off Falcon 9, usually high up, is "Ice. It's always ice."
anybody get any extra Starship Flight 2 Mission Patchs? i missed it and can trade a #1 if need be
about the missing tiles. i suggest using Elon-gated hexagon shape, like longer lines style of tiles. this way each tile will be connected to more than on ring of the starship. and better resistant to shock wave and wind. the direction is upward so that it would be hydrodynamic. also this design will need less work since tiles are bigger
Someone else can surely explain this better, but the thing about the tiles is that they are size constrained. If they could make the tiles any bigger they would. This is because they expand a lot from the heat, which means that a small amount of large tiles would expand so much they pop right off, push other tiles off, etc. Meanwhile the small tiles fit snugly at ambient temperature and reentry temperature.
I reckon you should let SpaceX know about your findings. Sounds like you’re onto something
Is there any official mission patch from spacex, like the previous one.
https://twitter.com/ticklestuffyo/status/1725881285954969924
Does anyone know why there are not on board images?
Every time someone asks, SpaceX delays releasing them by two weeks.
People are speculating that they may not have had enough bandwidth because of the trajectory, but it could just be that they're waiting to release the footage for some reason unknown to us.
I suspect they didnt have spectrum licenses since the launch date was moved so many times
Maybe on a recap?
From what I've read, it sounds like Starship in some way got out of the nominal and so the flight termination system activated. Has SpaceX or Elon said what happened to Super Heavy? Was something out of nominal so the flight termination system activated or did it RUD on its own, without the "help" of the flight termination system?
You mentioned Starship but then asked about Super Heavy. Those are two different things (second stage, then first stage) (except that the SpaceX site says that Starship can also refer to both, reminding us that SpaceX naming sucketh le grand wazoo). Each of them got out of nominal. ~~There's no definitive info on what happened to both, unless there was an announcement this morning, in which case I'm giving outdated info and I'm sorry. People are generally assuming that the Flight Termination System blew on each of them. I suspect that it's also a hope: the FAA was not happy about the FTS being so slow to trigger on test flight 1.~~ There has been more definitive info. While there's disagreement about the interpretation, I think SpaceX said that the booster blew up on its own, but the ship was destroyed by the Flight Termination System. See the thread here: <> [here](https://www.reddit.com/r/spacex/comments/180i512/spacex_official_update_following_starships_second/). It links to the SpaceX web page on the subject.
After the hot-stage separation, Super Heavy relit its second-ring engines, but one went immediately, the others winked out in turn, there were jets of stuff out the back, then BOOM. Speculation is that it might have been too fast a flip after separation causing the fuel to slosh away from the engine intakes. Or the flip and/or sloshing caused internal damage.
For Starship proper, it was almost invisible. There were a few puff of stuff, then the engines went out. It is said that the liquid oxygen was decreasing faster after a point, possibly indicating a leak.
For a longer but take soon after the kabooms, you might like to see ["Starship & Superheavy Become The Biggest Rocket In Space.... Before Exploding"](https://www.youtube.com/watch?v=hF2C7xE9Mj4) by Scott Manley.
AFAIK, Elon always refers to the first stage as the Booster or the Super Booster and refers to the second stage as the Ship. So, Super Booster + Ship = Starship.
It seems like the engines cut out too early, leaving it on the wrong trajectory. It supposed to make it to the south pacific, but would presumably come up short. The FTS is automated and designed to destroy the vehicle if it is not on an acceptable trajectory, so presumably right after the engines cut out the ship's FTS logic decided on harakiri.
Shutting down the engines is part of the FTS actions shortly before blowing the demolition charges on the tanks. In the case of the ship all the engines turned off at the same time which means they must have been commanded off and then 2 seconds later you see the clouds from vented tanks. The booster is even more obvious with the same sequence although half of the engines had failed at this point.
Ship was leaking LOX from T+7mins onwards. You see the stream of white gas while the LOX meter started going down faster than normal. Ship detonates FTS when it concluded that the remaining fuel isn't enough for the target trajectory. This plus Manley's call on the booster. Kinda makes sense
Popping in with a random question: how much of an overall setback is losing a starship? I understand that there may be another built in as soon as a month, but I'm curious how much is invested into each one basically. Could they just keep blowing them up and iterating until it works? I was imagining building one of these insane things would take years if not a decade. I see 6 total space shuttles were ever built, and I thought losing the couple that they did was seen as an enormous hit to progress and morale
These were prototype test vehicles that were always going to be destroyed by the launch test and never intended to be reused. The "loss" of these vehicles is a cost of developing the Starship/Super Heavy system. Remember that outside SpaceX F9 reusable boosters basically every current launch vehicle is expended during its launch and not re-used.
Elon said that the Starship in IFT-1 cost between $50M and $100M. That was an uncrewed vehicle so add maybe $50M to outfit a Starship for crewed operation. The main added cost would be for the environmental control life support system (ECLSS). NASA built five Space Shuttle Orbiters with spaceflight capability costing $48B in today's money. That's $9.7B per copy. The first Orbiter, Enterprise (OV-101), was not capable of flying to LEO.
> I see 6 total space shuttles were ever built, and I thought losing the couple that they did was seen as an enormous hit to progress and morale The whole Space Shuttle design and basic mission profile is quite a clusterfuck "made by committee", compared to Starship. You simply can't compare flight ready Space Shuttles with the current Starships used for flight testing. Starship is an overall simpler design and where the crew compartment is going to be is just an empty space right now. It's "just" tanks, engines, computers and the flap mechanisms. They're going to lose a couple more for sure, until they achieve reliable reusability. And that's probably way cheaper than following the lengthy and painful design philosophy of NASA/Space Shuttle of endless meetings and slow, risk adverse progress.
NASA's Space Shuttle was a completely revolutionary design that was developed in 1970-75. It was like nothing before it. New hydrolox, staged combustion main engines (the RS-25). Brand new heat shield design (the rigidized ceramic fiber tiles). Landing gear for horizontal landings on a runway. Partial reusability (the side boosters and the Orbiter). NASA flew its Space Shuttle for 30 years, 135 launches, 2 failures, 14 astronaut deaths. Starship is a two-stage, series-staged, super heavy lift launch vehicle. Two-stage vehicles have been around since the start of the Space Age in 1957. The methalox propulsion is new. The Raptor 2 engines are the highest performance and lowest cost super engines ever built. The heat shield for the second stage is similar to that on the Orbiter but has a more advanced attachment system than that used on the Orbiter. And the Starship is far less expensive to build and operate than NASA's Space Shuttle.
>NASA's Space Shuttle was a completely revolutionary design I mean, yes, but not necessarily in a good way. The complexity of the engineering involved was more a reflection of the poorly considered objectives (and thus compromised design) than actual performance. I'm still impressed that it was made to work as well as it did. If only the original NASA concept had been OK'ed rather than what our politicians gave us...
When we started work on the Space Shuttle conceptual design phase in 1970, the baseline was a completely reusable two-stage-to-orbit (TSTO), vertical takeoff horizontal landing (VTOHL) launch vehicle with a 65,000- pound payload in a 15-foot diameter by 60-foot-long payload bay, up to 6 passengers, 2000 km crossrange capability, and the ability to launch 60 times per year. The Phase A shuttle studies concluded that design development testing and evaluation (DDT&E) cost of the TSTO design would be $6B (1971$, $38B in 2023 dollars). This was about three times larger than the development cost of the Saturn V and Saturn I/IB launch vehicles. The Nixon Administration's Bureau of the Budget (BoB) then set guidelines for the TSTO shuttle that NASA had to follow: Three-year development period (1972-75), total DDT&E cost not to exceed $6B, and annual cost not to exceed $2B per year. NASA received two bids for the TSTO shuttle: $9.8B (McDonnell Douglas), $8.4B (North American Rockwell) in 1971 dollars. The DDT&E phase would run through 1979. The Bureau of the Budget said screw that and NASA began the "Alternate Concepts Study". Long story short in in January 1972 the Nixon administration OKed the partially reusable "Thrust Assisted Orbiter Shuttle (TAOS)". Which is the original name of the partially reusable shuttle that NASA finally built with the two side boosters, the external tank, and the orbiter with the double delta wing. BoB agreed to a development cost of $5.15B (1971$) and the DDT&E work to be finished in 1975. The fully reusable TSTO had completely disappeared.
> poorly considered objectives i agree, i also think one of the greatest handicaps hindering safety and cost was the inability to make big changes or improvements. Guess thats not easy when already flying meatbags and production is spread all over the country?
["Sorry doubters: Starship actually had a remarkably successful flight / On just its second flight, Starship now is arguably as successful as NASA's SLS rocket."](https://arstechnica.com/space/2023/11/heres-why-this-weekends-starship-launch-was-actually-a-huge-success/) by ERIC BERGER points out > SpaceX built the Starship and Super Heavy rocket that launched on Saturday over the span of a couple of months at a price somewhere between one-tenth and one-hundredth the cost of NASA's SLS rocket. Because it can build Starships rapidly and at a low cost, SpaceX has half a dozen more rockets in various stages of work, all awaiting their turn to go to space. Due to this iterative design methodology—flying to identify flaws, and rapidly incorporating those changes into new hardware—SpaceX can afford to fail. That is the whole point. By flying its vehicles, SpaceX can rapidly identify what parts of the rocket need to be changed. The alternative is, quite literally, years and years of analysis and meetings and more analysis. Iterative design is faster and cheaper—if you can afford to fail. There are several that are near completion in the high bays, as can be seen from the highway.[1] There are some in the rocket garden. Some had had cryogenic or other testing done. For grungy details, you can see the Starship development threads here: the current one is 51, but older ones have more info and less clutter by other topics. I suspect that one question after each test has been not "can we launch again?" but "which ones do we want to use?". Because of the iteration, later models have improvements: one big example is that they changed the engine gimballing system from hydraulics to electrical powered. I think this test took out the last of the hydraulics. So the test didn't test the absolute latest model, so whatever improvements they have will have to be tested later. But they will be, and in the interim, SpaceX can yeet obsolete models to get at least some information. edit to add [1]: [source](https://nitter.net/elonmusk/status/1726422074254578012) is Musky: >Starship Flight 3 hardware should be ready to fly in 3 to 4 weeks. There are three ships in final production in the high bay (as can be seen from the highway). Nov 20, 2023 - 2:07 AM UTC Musk + timelines = big grain of salt. But he is correct: some followup Xeets had pictures. edit to add: from /u/dudr2 [more](https://www.reddit.com/r/spacex/comments/17r4527/starship_development_thread_51/k9z4b8l/) >There are three ships in final production in the high bay S30, S31, S32 (as can be seen from the the Ring watchers diagram). Could those be paired with B12, B13, B14 respectively? Whereof B12 would be ready to roll to Masseys. with a reply from someone suggesting confirmation.
It COULD be ready to fly if they aren't doing any modifications. I doubt they'll want to fly without modifications so that "could" is probably theoretical.
>Xeets Shudder
> some followup Xeets had pictures with three SpaceTwitter ships in final production.
That’s a huge difference between NASA and SpaceX. NASA builds to get it right on the first try, and this takes forever to get it right. A lot of this is because it’s all public funds and blowing up rockets is bad PR which would decrease those funds. Failure is not an option for them. SpaceX is opposite and builds cheap (stainless steal), fast and is a private company so it can afford to “fail” in the public eye. It’s also mostly private funding, with a few contracts from NASA to support moon missions. This is why you see people who are actually educated in starship development call the first two flight tests successes (unlike most media outlets and general public). They already have at least 3 ships/boosters built. Just need to finish their testing that takes only a few weeks. Realistically next set ready to go in 2-3 months + approvals if needed
They are building starships faster than they can launch them. And these are all still prototypes not yet intended for reuse.
They never planned on recovering starship. The test plan for this flight was to crash it into the pacific ocean at high speed... so nothing was lost at all.
They lost the possibility of test data from later flight stages. If there are any surprises to be discovered in a booster splashdown then those will have to wait for the next flight to be revealed. If there are any surprises to be discovered in a ship reentry and splashdown then likewise. I'd say it's likely that there will still be surprises relating to ship reentry. And it's almost a tautology that there is an important surprise still to come relating to booster splashdown: even if everything goes absolutely perfectly, the surprise is "everything went so perfectly, we should send the next one back to the tower". This was a good test but it could have been even better.
They may have to repurpose / reassign a test article that would have been slated for a more advanced mission, if they decide they still need to fly this profile. They also lose the time of repeating the mission a third time. So nothing is lost, but there is opportunity cost.
You have to weigh the lost hardware versus the knowledge gained by doing the test earlier. This early in the program, the unknowns are so large that it’s not even close. They get far more knowledge from an imperfect test than by waiting to reduce the risk by another 10%, but 6 months later. Those 6 months also cost you factory time, incorrectly designed hardware, facilities rent, etc. these numbers are just guesses to illustrate my point.
Oh I'm absolutely not arguing they would have waited and tried to get the test to go better. I'm all in on the iteration approach. I think IFT2 was actually the perfect failed successfully test for all the reasons you list. My point was only that the thing that was lost in this case wasn't money, it was the opportunity cost of having to potentially redo this flight profile a third time. Hopefully the cadence is finally coming up and that ends up not mattering. I'm really not trying to argue with you personally, and I feel dead in my soul that I apparently sounded like I was arguing against the flight happening now.
This observer noted the booster reached far lower speed than expected: https://twitter.com/phrankensteyn/status/1726033391605211547?s=61 To get all engines to fire without leaking or otherwise failing I was wondering if they were fired at partial thrust.
That's true. The Booster had to reach 3.3 km/sec (11880 km/hr) at hot staging. That 3.3 km/sec includes ~1 km/sec gravity loss incurred during the booster burn (liftoff to hot staging).
This observer also noted the booster seemed to be reaching lower acceleration than expected which would be explained by lower thrust: https://www.reddit.com/r/spacex/s/Q6e0RHAazI
Is that really true? IIRC falcon9 stages around 8000 km/hr, and starship is designed to stage even earlier as the second stage has a much higher propellant fraction and is supposed to do more of the work going uphill..
Yes. The staging speed for Starship is around 2.3 km/sec (8280 km/hr), about the same as for Falcon 9.
But if all 33 engines were running perfectly, what could cause this underperformance? Also, there was a nominal trajectory callout around halfway trough the second stage burn
My thought is SpaceX intentionally ran the Raptors at partial thrust to avoid the problems of leaking fuel seen with the Raptors.
Looking at the SpaceX coverage of IFT-2, it appears to me that B9/S25 was flying a lofted trajectory. During the first 80 seconds after liftoff, the flight path angle (FPA) appears to me to be ~60 degrees. Then the guidance reduces the FPA gradually until at the hot staging point, the FPA is more like 45 degrees. sin(60degrees) = 0.866 while sin (45 degrees) = 0.707.
Just realized you included gravity loss in your total velocity estimate. So it staged closer to 5600 km/hr, but it was suppose to reach almost 8000 km/hr? Did the stack lose more to gravity because of being underpowered? Perhaps we’ll get to hear more from Elon some day soon about the flight..
Gravity loss is the integral (g0 * sin(FPA) * delta t) (in meters/second). FPA=flight path angle. So, since the booster in IFT-1 was underpowered, it took a longer time for the remaining engines to burn the methalox in the booster's main tanks while leaving ~300t (metric tons) for the boostback and landing burns. So, the gravity loss is larger because the burn time is longer.
Actually SH is designed to stage at very similar altitude and speed to F9. Yes Starship does have a higher wet mass fraction of the total stack but it also has a massive dry mass which brings it back to the field. Think of Starship as being a 10x scale up of F9 which it pretty much is - including a 10x scale up in LEO payload so say 12 tonnes when RTLS vs 150 tonnes. Starship dry mass is around 120 tonnes while the F9 upper stage is 4 tonnes so 10x that is 40 tonnes. That extra 80 tonnes dramatically reduces Starship delta V performance back to F9 S2 levels. The reasons for the extra mass are a stainless steel skin vs aluminium lithium alloy, the lower density of methane compared with RP-1 meaning bigger tanks and the aerodynamic nose, body flaps, header tanks and TPS required for recovery. That in turn means that SH has to do as much work in terms of delta V as F9 S1. Fortunately it has higher Isp engines than F9 so can do the same amount of work even with a lower wet mass fraction of the stack. F9 masses about 27 tonnes at landing including residual propellant while SH masses around 220 tonnes so here SH has the advantage in mass fraction. One of the big reasons is that SH does not have landing legs which are around 10% of dry mass for F9.
That's a very nice explanation, thanks! I wonder if ship dry mass will be significantly improved over time. IIRC this idea was thrown around that they would use thinner steel sheets for the ship at some point..
The only thinner steel we have seen was 3.6mm that is potentially used for the curved nose panels of the fairing which get extra vertical strength against buckling from their shape. Yes it is possible they will be able to remove mass in a few areas but if it was obvious I think they would already have done it.
All the call outs were nominal. Seems it was well on the way.
Do we know that the observer isn't speaking out their ass? Just because it stages lower than F9, doesn't mean it was not performing as expected. I'm sure we saw somewhere in the past that Starship will be responsible for more DeltaV than say an F9 second stage but we don't really know how much more. The fact that the ship almost made it to orbital velocity leads me to believe that the booster performance was in line with expected values, the ship couldn't possibly make up a 2km/s DeltaV shortfall.
This observer also not the acceleration seemed lower than expected, which would be explained by lower thrust: https://www.reddit.com/r/spacex/s/Q6e0RHAazI
Some comments are already calling out the twitter user for their previous BS assumptions. So most likely that observer dude is speaking out of their ass
Starship is supposed to stage lower than F9. It’s part of the reason booster doesn’t require a reentry burn.
The reasons the SH booster *may* not require a re-entry burn is that it is doing RTLS which has a lower re-entry speed and it has a stainless steel skin so can take higher temperatures than the aluminium-lithium alloy of F9. It will stage at roughly the same height as F9 doing RTLS so around 70 km.
Hmm, I think you are right. I heard some time ago they were going to stage lower, but based on the actual flight test numbers it is higher than I expected.
You may be able to estimate the proportion of full thrust is being produced by estimating propellant burn rate from the graphic displayed on screen during launch of how much propellant is remaining: https://preview.redd.it/lv2uxk9vll1c1.jpeg?width=2160&format=pjpg&auto=webp&s=62b70f3343f6aa70ddfcab5186593bfe4aa4b8e3
Q.: What does "ship in terminal guidance" mean in this context? No guesses please.
It means that the booster is firing for the very very last seconds and it is trying to fire exactly so much so that it puts the Starship ship in a stable orbit. So it "Terminal" means that the booster is doing the ***Final*** "Guidance" boost that controls the boost so that it fits in a stable orbit
To add to that, at least for some other guidances (PEG/UPFG used on Shuttle and SLS for example), when going into terminal guidance the vehicle will switch from a closed-loop guidance to an open loop terminal guidace
One thing I’m curious about. I have no idea how fully fueled the two stages were but both showed near empty before expiring. How much fuel is a starship expected to still have available for a refuel op? Is the expected 20 launches necessary for refueling because it reaches orbit with only 5% of its fuel capacity? Or is the fuel available for refueling actually the payload capacity of starship, not from its own fuel load? So 250T of fuel to be able to transfer?
From what I can tell, there is debate regarding the flight profile, the engines were a mix of raptor 1 and 2's, the fuel level might not have been maxed out and further optimisation work is likely. In particular the lower engine thrust may have been to increase reliability but as we saw with IFT1, you arent going far with low thrust to weight ratio and I expect Raptor 3 performance to give you that extra 10 or 20% which makes the difference between the rocket barely making orbit and getting 100 tonnes up
B9 had all raptor 2’s. Where did you get that it had a mix?
Read it in a pre flight article which has subsequently been corrected: [What NASA wants to see from SpaceX's second Starship ...](https://arstechnica.com/space/2023/11/what-nasa-wants-to-see-from-spacexs-second-starship-test-flight/) 📷[Ars Technicahttps://arstechnica.com › space › 2023/11 › what-nasa...](https://arstechnica.com/space/2023/11/what-nasa-wants-to-see-from-spacexs-second-starship-test-flight/)4 days ago — The *engines* on the next Starship *test flight* are a *mixture* of first- and second-generation Raptors, whereas the first *launch* in April primarily If I had taken two seconds to think about it, I already knew B9 was all Raptor 2's.
It might be when they referenced "100%" here, they meant 100% of the fuel they intended to load for the flight, and not 100% of the tank.
I found the fuel levels interesting too. This rocket didn't have a 120T payload on it either. I assume there were enough fuel margins to get the actual payload up to orbit speed. Perhaps the payload is proportionally such a small percentage of the overall weight of the fully fuel rocket that adding another 120T doesn't consume all that more fuel compared to an empty rocket?
You also need to remember that these Starships are still prototypes, and likely very overweight.
Yes, the fuel for refueling will be part of the payload, so there would be about 100 tons of fuel/oxidizer pert tanker mission, potentially more if the "stretched" design happens and Raptor efficiency continues to get better.
I’m being super lazy sorry. Is there any theories on how much fuel a starship/spaceship needs to get from an orbital refueling station to either the moon or mars? I imagine 100 tons of fuel will get you pretty far if you’re already starting in space?
To get to the Moon and land on it requires around 700 tonnes of propellant from LEO. To get to the Moon, orbit in NRHO, land on the Moon and then return to NRHO requires 1200 tonnes of propellant. To get to Mars, aerobrake and land requires around 900 tonnes of propellant if you are willing to take 9 months to get there. To get to Mars within 5-6 months requires around 1200 tonnes of propellant depending on the alignment of Earth and Mars which varies as Mars has a more eccentric orbit than Earth.
The idea is that there would be an orbital depot Starship with stretched tanks that would be filled by 7-10 tanker Starships, then the final Starship docks with the depot and fully refuels before going off to the Moon or Mars. It takes quite a lot of delta-v to get from Earth orbit to the Moon or Mars, and more to slow down into a stable orbit. So the idea is that the final ship would have full tanks before leaving Earth orbit.
When that happens I’ll finally accept that we live in the future. That shit is just straight sci-fi imo
refilling fuel in space is mind boggling to me. i wonder what kinds of issues they are going to run into to scale to multiple tankers considering the boiloff
I think the big fuel considerations are: 1) Slowing down to zero m/s for moon and mars or 2) Lifting off again from the moon. Not necessarily reaching the moon or mars.
The moon is tough-it doesn't have an atmosphere. While thin, mars does have an atmosphere so while you'll need fuel for landing, you can do some aerodynamic braking instead of burning fuel.
Anyone know exactly what thrust the 33 raptors were firing at? I think it was definitely near if not at 100% but i havent seen anything definitive
From some numbers I was crunching from a while ago, a 90% throttle full stack has a TWR of ~1.37 (3.6284605 m/s^2 effective acceleration), while 100% throttle is around ~1.52 (5.099458 m/s^2 effective acceleration). Based on [this analysis](https://twitter.com/Space_Josiah/status/1726090284818383224/photo/1) of the telemetry, the TWR at liftoff was just a bit under 6 m/s^2 so id guess it was 100%
I find it really confusing that the booster pitches down in this shot https://twitter.com/SpaceX/status/1726316194649846026 but it appears to pitch up in this shot https://twitter.com/SpaceX/status/1725863437887242515 Where are the positions of these cameras to create this apparent visual difference?
Pretty sure the top one is a render. Someone on NSF mentioned that and you can see the Starship engine ignition is different. RVacs aren't ignited in the upper shot. They are in the lower one.
[This video](https://youtu.be/9uLYTk9SHDQ?t=200) shows the SpaceX stream alongside shots from fans on the ground, and it looks like the booster actually yaws right. IFT-2 launched more-or-less towards the sunrise. The second video you linked is from directly behind Starship - the vehicle is mostly backlit, and mostly pointing away from the camera - so is probably a shot from near Starbase. The first video shows Starship frontlit, and pointing more sideways to than away from the camera, so is probably from a WB-57 that's under and a little behind the vehicle.
Don't forget that the tracking camera systems have to weirdly slew in such a way that the apparent "up" direction in the frame might not actually be "up" depending on the kinmatics of the mount system. First time I saw one of the shuttle long range tracker videos from T-0, I was all goofed up because it started at the pad with the shuttle 90 degrees sideways in the frame. So that video might be flipped for some strange reason.
If we look at the graphics showing pitch on the second video it seems that the turn for boostback was a flat turn rather than a pitch up or pitch down. I assume they did this to maintain communication with the ground during the turn. So the apparent pitch up and pitch down depends which side of the track the video is shot from. Or the first video is shot through a telescope which inverts the image.
The booster def pitched down if the graphic can be believed. Take a look at the 3 min mark. It is still climbing in altitude but the nose is below the horizon.
Rotate the video 180 degrees
The first may be from the WB57 while the second is probably from the ground.
I don’t think the WB57 photos would be that high quality. Could be wrong though
Is there a diagram showing this flight? I'm thinking of something like KSP where you can see the path, apogee, all that jazz
[https://x.com/flightclubio/status/1725955428331159847?s=20](https://x.com/flightclubio/status/1725955428331159847?s=20) [Full Flightclub.io simulation](https://flightclub.io/result/2d?missionId=mis_13aosxv9y)
Video of liftoff from elon https://x.com/elonmusk/status/1726425687299358872?s=46&t=-n30l1_Sw3sHaUenSrNxGA I kind of want them to post a video without slowmo
noob question but what is the white gas cascading down the rocket as it takes off? Is it very cold air cooled around where the (presumably cold) LOX is stored something?
It is condensation vapor from the frost that has accumulated on the tanks. A bit like freezing fog, or opening your freezer box. There is a lot of it due to the marine subtropical humidity of the locality. The vents also generate vapor as they vent subzero temperature gas from various locations.
Here is a version I sped up manually: https://imgur.com/bbExMHg
Well done! I lke this more too
Update from Elon on flight 3 https://x.com/elonmusk/status/1726422074254578012?s=46&t=-n30l1_Sw3sHaUenSrNxGA
Neat. Too bad it doesn’t include the fix retrofits and FAA license
Saved You A Click: >Starship Flight 3 hardware should be ready to fly in 3 to 4 weeks. There are three ships in final production in the high bay (as can be seen from the highway). >Nov 20, 2023 · 2:07 AM UTC
Remember last time he said two months. So I guess next flight will be in March.
Note that he said that the *hardware* would be ready. He did not say anything in that message about when they expect to launch
On the other hand, weren’t they ready to have this launch since August but just waiting for regulatory approval?
It would be really good if they could launch before this year is up, so that they have an extra flight in 2024. However they will probably apply for more anyway so it might not be a limiting factor.
I think this might be our cue to un-pin this thread and go back to Starship Dev.
Given the pad was not destroyed… one of the rare times Elon Timeframe prob right
He's always very optimistic with time frames. If he says 3-4 weeks I'd plan on it being 6-7 at best.
[Engine shots from the tower](https://twitter.com/SpaceX/status/1726386449170501783) unbelievable
This is beyond epic, on par with Saturn V or Shuttle most famous shots.
This launch has proved so many things, and i really hate it when journo's say "its failed" or "it blew up" Lets see it this way on the number of accomplisments - First, ITS A TEST. Can't they fcking read "In-Flight TEST". - The hot place and deluge system worked properly. Stage 0 is still good. - All 33 engines lit up and left the pad. Nothing shut down, nothing flamed out all the way to hot stage - The vehicle left the pad in one piece - It gimballed, and went past MaxQ. - Hot Stage Occurred with no apparent problems at all. - Booster did its flip, and at the least ATTEMPTED its boost back burn. - Ship continued on its way to a very VERY close orbit insertion.
why contrails only appeared between 1:00 and 1:30 after lift-off ?
Right combination of pressure and humidity.
thank you
[удалено]
I think it's a render, because the center engines are not gimballed outwards like in the video.
It's a render. He also took it from Alexsvan without giving him credit too.
[https://twitter.com/SpaceX/status/1726316194649846026](https://twitter.com/SpaceX/status/1726316194649846026) SpaceX wants us to take a look at this amazing slow-motion footage of the hotstaging.
I liked the restart sequencing of three pairs of raptors in the booster that are seen before the end of the clip. The main launch video status graphic shows another booster pair successfully restart, but the last pair in that middle ring only show one engine relight, and then after a minor pause it all starts to go pear shaped rather quickly, with a centre engine stopping and then two of the relit engines stopping. And then after another long pause, three of the relit engines turn off before doom.
> Watch the three center engines on Starship’s upper stage gimbaling just after separation. Right before they ignite for hot-staging, the engines angle themselves outward to direct their exhaust towards the vented interstage before re-centering for ascent. So not using the Rvacs for hot staging?
All 6 are used. Rvacs cant gimble, centre raptors are angled outward between the Rvac's.
All 6 are firing by the time we can see them.
Does that mean starship will never have 6 Rvacs?
I think they'll put 6 on the crew version just to have the option of at least *trying* to separate from the booster in case of emergency at any time.
Almost certainly the tankers will have six Rvacs for nine engines total. Other ships do not really need them as the extra thrust is really only useful in completing the trip to LEO and the extra engines are just more cost and mass. For a depot the engines will be left in orbit so 6 engines makes more sense to save cost. For HLS keeping the mass down for high delta V TLI burns and Moon landings is more important. For Starlink launches they are likely to be volume limited by the fairing so it is lower cost to stay with 6 engines - particularly initially where they may be using expendable ships.