Ultimate Steve

There was another Starship debate over on a Discord server today, as seems to happen every couple days like clockwork, and I came away from it with somewhat of a new perspective on the Starship program. Many of the criticisms of Starship ultimately come down to the idea that it is too ambitious, that SpaceX has bitten off more than they can chew here. Well, that and taking off the cuff remarks by Elon (for example 1m per flight, 1000 passengers in p2p) as gospel and using them to show why the program is obviously stupid and the whole thing is a scam. But the first one is more interesting and what I thought about a lot today. Ignore HLS for a second, I'll talk about that later. I think a lot of people would have liked to see SpaceX originally take (or pivot to) a more conservative approach to a next generation launch vehicle as a stepping stone to a fully and rapidly reusable launch vehicle rather than skipping straight to something with Starship levels of ambition. Like, for example, a fully reusable but not rapidly reusable vehicle, or a very large partially reusable vehicle. But why? The obvious answer is that it allows them to create something that blows Falcon out of the water for considerably less effort than Starship would take. ...But why? They have the market completely cornered. Nobody can compete with Falcon, even discounting Starlink. Everyone except possibly Blue Origin and Relativity is stuck trying to create a rocket marginally competitive with what Falcon 9 was a few years ago. Serious competition is at least 10 years away. SpaceX doesn't need to do a thing to completely dominate the space industry for the foreseeable future. They can sit on their hands, maybe make Falcon block 6 if Relativity is looking threatening enough in a few years time. Basically do what ULA did. What could they do with a Falconlike SHLV that they could not do with Falcon? Large stations if anyone was interested, maybe small scale medium-high cost Moon missions, being the de facto Artemis launch vehicle. But not much that is commercially viable. Not many people are going to pay 120 million for 100 tons to orbit. There would be a market, but as we are seeing with Falcon Heavy, not a huge market. SpaceX does not want to launch a handful people to the Moon for tens of billions of dollars. They don't want to sit on their hands and accumulate wealth. They do not want to keep making minor improvements to Falcon 9 forever. Whether or not you agree with this goal, SpaceX wants to create a self sustaining city on Mars, or at least, create some of the prerequisite technologies required for that to happen. It is not a financial goal. It is an emotional goal. SpaceX is fundamentally an emotionally motivated company, and while finances can't be ignored, they are a means to an end. If money was the primary goal, Elon would have created sensible businesses with the PayPal money. instead, SpaceX was created out of spite for the Russians and frustration with the state of the industry. Since then, they have plastered windows on things with no business having windows on them (Cargo Dragon, I4 dome, doubling down on Starship having a huge window), dragged the space industry, kicking and screaming, into the 21st century, with many of the major advancements financed on their own dime, made Dragon 2, their spacesuits, the crew access arm, the launch tower, and much more look stylish and cool (depends on taste), arguably at the expense of a small amount of functionality, and strapped a meme payload to what was at the time the most capable operational rocket in the world. I rewatched the IAC 2016 talk today, and while almost all of the details have changed, the core architecture has remained the same. That talk laid it out clear, this core architecture was designed with Mars in mind. In order to create a self sustaining city on Mars under reasonable economic conditions, a rapidly and fully reusable vehicle must be mass produced, and it must use propellants practical to produce on Mars, and orbital refilling must be utilized. While an incremental approach to developing such a system does have some merits, if there is a proper time to dive in headfirst into the onslaught of engineering challenges associated with such a ridiculously lofty goal, it is while they are a decade ahead of everyone else. In order to succeed, everything known about rocket building needs to be challenged. Anything short of a high performance mass producible rapidly and fully reusable rocket is not an acceptable stopping point, and SpaceX has made that clear with how often they threw out things that weren't working. They tested every assumption about rocket development made to date, knowing full well most of them would be reinforced, but a few would give way to unexplored potential. They threw out carbon fiber after investing a ton of money into the hardware to produce 9 and 12 meter tanks. They threw out the Florida starship site (for now at least). They made a water tower fly, and then threw out the next six prototypes for not being good enough. They built or partially built 26 starships and 3 boosters before getting something that might get to orbit, each of which had major changes from the previous, and then threw B4/S20 out practically on the eve of flight. They tried a new launch pad, and when that didn't work, they threw it out and tried something else. They tried a new form of staging, and when that didn't work, they threw it out and tried hot staging. They tried hydrolox Raptor, and it didn't work, they threw it out. Large scale ITS Raptor, thrown out. Raptor 1, 1.5, etcetera, thrown out. Raptor 2, on its way out because Raptor 3. There's even been talk of a different engine altogether. They have produced hundreds of Raptors by now and they haven't even gotten to orbit, that's more than the total production of most other rocket engines. ITS re entry configuration, thrown out. Two strakes, thrown out. Tripod with two flaps and a rudder, thrown out. Body flaps, modified numerous times. Initial tiles, thrown out. Bare metal, thrown out. Transpiration cooling, thrown out. Back to tiles because that might actually be the best option, several iterations, throwing them out until they are good enough. Can't land on the launch mount? Can't crane a ship from a landing pad to the launch pad fast enough to colonize Mars? Throw it out, try landing directly in the crane. They are pushing the envelope in all directions trying to find anything that will get them closer to their goal and they can and will throw out any design, no matter how firmly entrenched, if it falls short of their goals. They have created the largest satellite constellation ever (okay, if you're gonna be that guy, project West Ford was indeed way bigger) just to finance the rate at which they throw stuff away. Even that satellite constellation is designed to be thrown away and replaced every five years. This whole time, also pioneering the early stages of mass production necessary to make the city on Mars a reality. But this city can't be built alone. A rocket such as what Starship aims to be is a prerequisite for a Mars colony, but not sufficient on its own. So every so often, SpaceX will put Starship out there to get people thinking about what such a revolutionary rocket could do in fields it isn't even optimized for. A Moon base, gigantic space stations, crewed missions to the moons of Jupiter, probes ejected from Earth at insane speeds with refueled expendable upper stages, and even point to point. Some of these are more realistic than others. If enough people start thinking about what this could do, some of them will start trying to make it a reality, and some of them might just end up producing Mars hardware in a few decades time. Then, SpaceX decided to go "Hey, NASA, Starship can also be used as a Moon lander!" And in a move that was unexpected to most external observers, and may have even been unexpected internally, NASA, strapped for cash and with the only other status quo choices being "expensive consortium led by a company with no orbital experience" and "oopsie daisy, negative mass moment", saw a chance for an incredibly radical future, and went "Okay. You have four years. Show us what you can do." Of course, this is where it all went a little sideways. You can fiddle around with your revolutionary side project all you want when your only limiting factor is how long it takes other space companies to catch up with you. There are no customers to complain when it takes twice as long as planned, or keeps blowing up over and over and over again. While HLS has been great for emphasizing Starship's legitimacy and getting even more people thinking about it, now SpaceX can't just keep throwing stuff out ad nauseum, it actually has to deliver results in a reasonable timeframe. Granted, some of this is the government's fault, selecting a lander in 2021 and expecting a landing in 2024 was never a realistic goal no matter who is doing the design. But now, a program with the single constraint of "Get lots of stuff to Mars, toss away everything that can't do that" has to be made to support the most important human spaceflight mission in decades in relatively short order. It must be safe and with a relatively frozen design, and the tankers must be produced and rapidly launched with not much more tweaking. I don't know yet whether the added cash and legitimacy is outbalanced by the conflicting requirements. These conflicting requirements seem to be where a lot of the conflict is coming from. Since HLS, Starship is both a vehicle that needs to be chaotic in the near term in order to be revolutionary in the long term, and stable in the near term in order to get us back to the Moon. I don't know if they will make it to Mars, much less build a city, but if anyone can do it in the next hundred years, it is probably going to be them, and they are not going to stop trying to reach that goal until they go bankrupt or the CEO dies and doesn't get replaced with a like minded person. That was a lot more than I intended to write. TLDR: SpaceX is emotionally/ideologically motivated. Their ultimate goal is to colonize Mars. If their goal is to make money and remain competitive, they already have that, no reason for something Starship level. Something in between Falcon and Starship also does not make sense if their goal is merely to remain competitive. Starship makes sense viewed through the Mars lens, its other applications are byproducts. I suspect long term an optimized Lunar architecture will look a lot different. SpaceX will not design themselves into something that cannot be evolved into a rocket capable of creating a city on Mars. This means a lot of throwing out stuff that doesn't work, pushing boundaries, and lots of failures. Starship won the HLS contract, which is not a contract you want to have rapid iteration, boundary pushing, and frequent failures on. The two conflicting aspirations for what Starship is supposed to be are causing some amount of conflict and debate. In the time it took me to write that, the news that the ship firing today was a single engine maneuvering burn test arrived. This is completely unrelated to the above wall of text, but given how small LEO maneuvers will be (I'd guess this is simulating a de-orbit burn), that static fire might have actually been full mission duration.

I was not commenting on the validity of doing full duration static fires for Starship, I was just pointing out that full duration static fires were an important part of Falcon 9 and Falcon 9R's development cycles. But since you brought it up, all else kept equal, I would love to see full duration Starship and Super Heavy static fires, as there is some amount that can be learned from them. However, all is not equal, as SpaceX's land situation makes that more trouble than it is worth. Edit: I worded that a bit passive aggressively by accident, it is not meant to be passive aggressive.

They did, though. And as part of a series of many (I think they fired this one 8 times but it has been many years since I learned that so I might be wrong) post flight static fires to characterize reuse:

Last I checked we didn't have a clue why stage 2 exploded, the only real things we know is that: 1. There was probably a LOX leak towards the end 2. The FTS was activated While there isn't much to suggest it was engine related, there isn't much to suggest it wasn't engine related. But it is worth noting that the upper stage engines were (I think, double check me on this) an older model that still had hydraulic TVC and aren't really indicative of the current state of Raptor. Stage 1, we still don't have any official word, but it is looking like it had something to do with extreme fuel slosh during separation casing either damage to the plumbing via fluid hammer or propellant starvation, which is a problem with the flight profile and/or fuel feed system and not with Raptor itself. This is only as accurate as the public telemetry and this guy's CFD skills, but someone did run a simulation: That does not look like it is healthy for the vehicle. A bit alarming that internal simulations did not predict this, or maybe a bad assumption was made here, but preventing this should be a relatively straightforward change in the stage separation profile once the causes behind their improper assessments are made clear. It is also possible that the engine failures could be due to the effects of spinning up the turbopumps while in a weird angular rate and acceleration state, in which case the solution is to perform the flip slower and sacrifice a small amount of payload. It could have also been a large cascading failure, in which case Raptor, the failure detection software, and the engine shielding are to blame, but none of the IFT-1 failures caused obvious cascades (if I remember right). It could also be a lot of failures of Raptor due to the dynamic environment they hadn't been able to test at and analyzed incorrectly. This would indeed be a large scale failure of Raptor. Yes, it is quite possible that there is a huge conspiracy to cover up the fact that Raptor is unreliable. That is, however, far from the first thing that crosses my mind with the available evidence. Why would there be a conspiracy when we can look at the public test flights and see with our own eyes that Raptor has a ways to go? Every aborted static fire, every failed ignition, every sound a Raptor makes on a test stand, and every single in flight failure are all the subject of public scrutiny. There is no other rocket engine development program that is livestreamed 24/7 by several different YouTube channels. We probably know more about Raptor reliability than any other privately developed and operated engine besides Merlin. The part that seems to be missed by many is that Raptor is also obviously improving. A couple years ago, it was a struggle to light three engines at the same time on the ground, taking several attempts. Now they can ignite all 33 on the booster and all 6 on the ship first try, and have them work for minutes on end. There being no detailed public safety estimates for Raptor like there are for SLS is likely down to the different levels of oversight the programs have been given. Such analyses have not been mandated, so they would not be run. Such analyses would not have much point to them, as two Raptors produced six months apart are very different, and by the time a comprehensive safety report was completed, it would already be very out of date. The fact that the engines might still be iffy two years before the proposed lunar landing date is less down to the engines themselves and more down to the government trying to start a lunar landing program less than five years before the proposed lunar landing date, which was never going to work with any of the bids, and the only affordable bid being the most ambitious launch vehicle project ever, a project that was very open about not adhering to traditional development practices.

I do agree that bug is a strong word, but I do also think that suggestion is a weak word, so I am not entirely sure where this should be put. But yeah, time warp limits are too restrictive. They are making hunting for the new discoverables a pain, making biome hopping a pain, and making me put stuff in less efficient higher orbits, or taking less efficient steeper trajectories because I'm optimizing for time spent IRL instead of Delta-V.

Part 3 (Spoilers: Kerbin Sightseeing Quest Part 1 and Duna Quest):

Part 2 (Spoilers: Minmus Quest):

Hello everyone! One of my self imposed rules for my first KSP 2 save was to not make it into a mission report because I inevitably make up a story, and my willingness to make the story, post the story, and play the game get desynchronized and all three die. However, enough shenanigans have taken place, and I will only get to react to KSP 2's story for the first time once, so I thought I'd at least give this a short writeup. After all, what could go wrong? As of time of starting to write, I have just landed on Duna. All sections will contain spoiler warnings. Part 1 (Spoilers: Mun Quest):

Hello, checking in to make sure I'm not missing something obvious. Workspaces can be useful for assembling multiple ships in a series or multiple ships intended to be used together (although the vessel naming system needs a serious overhaul to allow it to work at its full potential), but for standalone ships, which is, at least for early game, most of the ships you will be using, you will want one workspace per ship. In KSP 1, I build my ship, title it, and save it. If I change something after it, I'll press save at least once, maybe a few times because I'm paranoid like that. In KSP 2 I open up a new workspace. I build my ship, give it a name in the top right hand corner. Then I press save. I get a menu. I have to then give the workspace a name, and press save a second time. If I make a change to the craft, I have to press the save icon, then press the save button, and then press "Yes I want to overwrite the design I'm currently editing" button. All these extra clicks are adding small amounts of frustration each time I have to click several times to do what took one click in KSP 1, am I missing something about how to use workspaces or is this a case of poor design?

Reported Version: v0.2.0 (latest) | Mods: none | Can replicate without mods? Yes OS: Windows 10 | CPU: AMD Ryzen 5 1400 | GPU: 1650 | RAM: 16gb When I place some parts, such as the RA-15 and RA-2 relay antennas inside a fairing, launching too fast through the atmosphere will still heat them even if the parts are inside a protective fairing. Here is the ship, the Solar Challenger 2, although I have experienced this bug with other ships. I attempted to fix it by mounting a heat shield in front of the antenna, but that did not work either. Once it gets going fast enough, the relay antenna starts to heat up despite being visibly inside the fairing. Heating up some more. And, gone. Visibly gone once the fairing has disappeared. This is a separate bug but if I go slow enough to prevent overheating, antennas and docking ports (and maybe other parts?) do not appear to radiate heat away and will stay nearly overheated for the rest of the flight. To reproduce, enclose an antenna in a fairing and go fast through the atmosphere. Included Attachments: .ipsImage { width: 900px !important; }

Okay, that three week cadence lasted about as long as summer did, it is winter break now, so maybe I'll get another one or two out before it ends, but then, what a scary thought, I'll have no more breaks until I retire unless I can't get a job post graduation... That doesn't make me sad or anxious or scared at all! Anyway, finally: Chapter Three: The Gilded Planet

Good catch, I somehow saw the stage 2 analysis and misread it as stage 1 in my head, my bad. A mistake that bad is inexcusable, and I do indeed have no excuse, and it calls into question the rest of my analysis. I am aware of that, which is why I said that my first analysis was not valid past the first 30 seconds or so. In the second part of the analysis, the x and y accelerations are broken out and trigged together separately according to that graph and the current pitch angle. But yes, I did not really question the validity of that set of data, as the method I think they used to separate horizontal and vertical (finding vertical velocity by numerically deriving the altitude telemetry, using that and the total velocity to find horizontal velocity, and numerically deriving both to find both accelerations) is only as good as the available telemetry and timestep. Since we can see the accelerations change more or less in line with the mass flow and mixture ratio changes, I'm inclined to believe that the current numerical way is good enough on these timescales, but if the telemetry we have can't be trusted, then any conclusions based on it are little better than speculation. I also thought about the pitch angle method, I would have done that analysis above for the whole flight with a spreadsheet if that data was available, but I don't think pitch angle data is available unfortunately.

I had a big long thing typed out but then realized I had multiplied by the wrong number somewhere and had to restart. In short, I have a large number of problems with the assumptions you made, but Raptor is indeed not operating at 100 percent of its advertised thrust. I have more problems with your conclusions, but let's just walk through the re analysis for now. This analysis only covers stage 1. I initially went to the raw video but then downloaded the data used to make the graphs you used after I had to restart after I was confident they matched well enough. I added columns for acceleration, smoothed acceleration, and expected mass at that point given the linear decrease you would expect at full throttle (this is not a valid assumption beyond the first 30 seconds or so of flight as any off nominal throttle would cause the mass to diverge). This analysis also assumes vertical flight by adding 9.81 to the acceleration, this is also not a good assumption outside of the initial 30 seconds. I then made a column for the current thrust, and another column for the fraction of the expected thrust (throttle). From my own double checking, Raptor is producing at or above 90 percent of its advertised thrust for at least the first 30 seconds of flight . Spikiness is probably down to inconsistencies in the source video but I am not sure. Due to the assumptions mentioned earlier, ignore everything after 30 seconds or so, it is not valid. The ramp up at the beginning may either be due to my implementation of the smoothing filter, or possibly the original source data has had a smoothing filter applied to it. Telemetry might also have a lag of a few seconds. EDIT: This section has some good points, but argues against a strawman. I somehow misread his stage 2 analysis as a stage 1 analysis, this a monumentally stupid error and I have no idea how I didn't catch it. Keeping it in for the good bits, but Exoscientist did NOT calculate stage 1 as having burned from 80% to 5% of its fuel. You used this graph to estimate fuel flow rate: Which has the starting fuel capacities at 80 percent, which does not seem right at all. Per official SpaceX telemetry, this is the stage 1 fuel load at liftoff: That's not quite full, but that looks like a lot more than 80 percent to me. Plus measuring fuel levels can be tricky, I'm not 100% convinced that sensor is fully accurate, as we have no idea what type of sensor they are using, and measuring exact fullness of a fluid container that big probably doesn't have an easy solution. The person who made the plot you used also had this pointed out to them, realized their mistake and uploaded a new version on the reddit thread you linked (update upon further inspection, this is in your blog post, but you used the numbers from the false one): Your math in the expected fuel consumption of 23.1 tons appears correct given the assumptions you made. However, just simply by inspection, it cannot be running at this throttle level for the entire 150 second burn, as it would consume more than the 3400 tons of estimated propellant. Using your numbers of 80% and 5%, that is 75% of 3400 tons burned in 150 seconds, or 17 tons of propellant per second, as you found. Using the corrected graph, with what appears to be 95 percent to 10 percent drop, we get instead ~19.25 tons per second, implying 83% throttle average if we assume a linear relationship between thrust and mass flow rate. I will return to my discussion about the accuracy of this data and whatever sensors are providing it. If it is some sort of distance sensor, which measures the height of the fuel in the tanks, it is possible they printed the raw value instead of accounting for the tank geometry, and this value could also be affected by slosh and possibly pitch if drag is significant enough to cause an offset in the fuel level from horizontal. If the sensor is of that type and the raw value is used, the first and last 5 percent or so would hold much less fuel than the rest. There also might be zeroing differences. A "full" tank with 3400 tons of propellant needs some volume free for pressurant, and will not actually be 100% propellant, so on this type of sensor, a full tank might show up as 95% full or so. I also don't know the methodology of how this data was extracted from the X livestream, the small rounded bars at low resolution don't seem conducive to precise analysis. Is the true value at the tip of the )? Or at the base? Middle? This could give us an offset as well. If the bottom 5 percent holds half of what a normal 5 percent would, and the top 5 percent is pressurant by design, it then comes out to 21 tons per second or 91% throttle, but I wouldn't put any stock in this number either, there are simply too many things we don't know. But either way from this graph, if I am reading your blog post right, you saw a constant slope and assumed a constant throttle, and also assumed a linear relationship between mass flow rate and thrust, where when throttling engines in real life, you can only do that to a point, you can also vary the mixture ratio to increase or decrease exhaust velocity and throttle that way. But why are we even using that graph anyway when you posted this far better one on Reddit a while back? From this graph it is very clear that there are at least four, possibly five separate throttle regimes, and that the mixture ratio varies throughout the flight. The slopes are, well, not visibly different, but they are with a ruler up to the screen. I was unable to find how you got this graph, but I am going to assume it is from the same raw data as the other graph, just properly plotted. In that case, the same sensor biases could apply if they exist. In either case, we can see by the variations in slopes and differential slopes, we can see that Raptor is altering its throttle by altering both mass flow rate and mixture ratio, which makes this a very complicated problem to figure out its thrust at any point in flight from this information alone. The simple F = mdot(u9-u0) formula cannot be used here as we do not know the isp of Raptor at all of its different mixture ratios and mass flow rates. Fortunately, we also have the acceleration data which you also used: The first 30 seconds or so seems to more or less match what I found, so it can probably be trusted, although I'd love to double check how the pitch data was extracted given that we only had the low resolution indicator on the livestream. Especially for the tail end of stage 2, it could skew the results if that indicator is inertial to the vehicle or fixed to local up/down. I do see pretty obvious throttle changes on that graph, though, which correlate to the earlier fuel graph. So, what I see in general is a gradual throttle down to maintain a constant acceleration near max Q, and then either a gradual throttle up or holding at that throttle level (or some combination thereof). After this the throttle tapers off towards the end of the burn. Redoing your analysis at the marked yellow bars, horizontal acceleration is 11m/s^2 (at the marked point it does not look like 10 to me) and vertical acceleration is about 6m/s^2. Plus the 9.8, vertical becomes 15.8. This is at about 95 seconds, and the pitch of the vehicle at this point in the flight was about 57 degrees above the horizon. (although as I said earlier the accuracy of this pitch data is questionable) Doing some simple trig, we can estimate vertical from horizontal as 16.94m/s^2 or horizontal from vertical as 11.26m/s^2, so there's a bit of inaccuracy somewhere, as expected when rounding to whole numbers. Net Starship acceleration is either: Via pythagoras: 19.25 Trig given horizontal: 20.2 Trig given vertical: 18.84 Which are similar to, but generally higher than what you found. Now, as for the expected acceleration at this point in flight (T+95), there's about 42% propellant remaining. Taken naively as a fraction of the booster's 3400 tons of propellant, the stack has a mass of about 2928 tons at this point in the flight, and the expected acceleration is 25.43m/s^2 using the sea level thrust. As for a vacuum, you have fed the vacuum isp back through the F=mdot(u9-u0) equation assuming constant mdot, which may not be the case, as Raptor may prioritize to maximize isp in some situations and thrust in others, by varying mixture ratio and mass flow rate (as we saw above, it does do this), so this assumption is a bit flawed. The source for the 363s number is also a NSF article from 2014, so I would not take stock in that either. That was the 4.5MN version of Raptor, which had 321s at sea level. I've looked and I cannot find an up to date vacuum isp or vacuum thrust value for non vacuum raptor. If you do find one, please let me know. Assuming your number of ~30m/s^2 as the worst case, Raptor is producing somewhere between 63 and 80 percent thrust at this point in the mission. This is not really a good faith analysis though without good numbers for Raptor's vacuum stats, so a wide range is the best I can do. At its worst, though, this would indeed mean that Raptor is throttling down to possibly below 2/3 at this point in the mission. So, from the data, your analysis appears to say that Raptor operates at below 75% throttle for most or all of the flight, the wording is unclear. My analysis shows that Raptor does operate at at least 90 percent of advertised thrust for a significant amount of time, and throttles down a lot throughout the rest of the flight, including to values in the rough range of what you were saying. From that, you conclude: Which is quite the leap. In two mini paragraphs you take that, assume that throttle has a linear relationship between pressure ratio (I just passed a class over these exact equations, a clean obvious linear relationship is anything but the case), and conclude that: Raptor has a leaking problem big enough to warrant throttling down Throttling down would solve the leaking problems The observed throttling down is to solve the leaking problems This throttling down would drop the payload by 1/3 This change would increase refueling launches from 16 to 24 With no calculations. Especially the 1/3 payload drop, I want to know how you got that number. I do not understand how you can conclude this so confidently. I don't think we have enough information to conclude the reason behind the throttling, but off the top of my head, it could be any of these, likely some combination of many of them: Increasing isp at the expense of thrust For a reusable vehicle thrust is very important in the early stages of first phase flight. Raptor's design has been changed a lot for maximum thrust at the cost of isp in the past. The optimal engine changes with a lot of factors. It may be mathematically optimal to throttle in a certain way throughout the flight to alter isp and thrust to whatever is optimal at that time. Raptor has been observed making many changes to mixture ratio and mass flow rate throughout the flight Basically, the idea here is that Raptor operates in an inefficient but very powerful way early on, and then powers down somewhat to increase efficiency later on Maybe the numbers we have are wrong (in which case our baseline for 100% thrust is also wrong) Most mass numbers we have are conveniently rounded to the nearest 100 tons, this is not a lot of precision. Fuel and dry masses could be off by a lot. Has subcooling changed since the propellant numbers were first given? Raptor isp is always changing, there's no guarantee that 327s is the correct value, or that the raptors on the most recent booster were the version that had 327s Likewise, Raptor thrust is always changing. No guarantee that 230 tons is the correct value, or that the Raptors used were the 230 version. 230 could have been a dev value from when they were pushing it and not necessarily what they would set it to on any given launch. 230 could also be an "Emergency thrust" value or something like that. These numbers could also vary from engine to engine. Differences between non gimbaling and gimbaling raptors I have not seen this talked about, maybe they have different thrusts. Are they the same, just one without gimballing hardware? Or has the non gimballing version been pushed further due to less complexity? The non gimbaling one is I think called Raptor Boost, maybe those have the 230 thrust and the gimbaling ones have less. Maybe they have different isp. Maybe they have different other characteristics. Maybe they are throttled separately to optimize for any given time of flight. Could telemetry have been inaccurate? Later in flight, does telemetry analysis take into account reduced gravity both from altitude and centripetal acceleration from increased orbital velocity? Does drag play much of a role in reducing apparent acceleration? Throttling down for vibrational reasons Combination of engine vibrations and atmosphere based vibrations could cause problems in some areas Throttling down for structural reasons Does not explain why throttle is so low so much earlier Does explain further throttling towards the end of the flight Throttling down for aerodynamic reasons Starship is pretty aerodynamically weird with the grid fins, chines, and body flaps, it may have different requirements than normal vehicles Max Q throttling as per usual Is this normal? Is this even a throttle down? Well, obviously the throttle is decreasing for some reason This could be the correct throttle profile for whatever reason, the one they think they can get 150 tons from This throttle down is not necessarily associated with a payload cut and likewise an increase in refueling launch count If this is not normal, is this permanent? There are many prototypes until Artemis, the throttle cut cannot be assumed to be a permanent feature (or a temporary one) The design is constantly evolving, SpaceX is not the type of company that sees a problem and just lets it sit there, they will keep tweaking and changing Raptor until they are happy with it. NASA still seems to be happy with progress from what I've gleaned in recent statements, although this is the public facing side of things and should be taken with a grain of salt Engine problems Engines could leak Engines could have been de rated mid flight by the flight computer due to off nominal signals Systemic engine problems could merit a reduction in target thrust by 10% for early flights And I suppose that it is possible that despite working fine for 30 seconds at 90% throttle, 60-70% was deemed the safe maximum for the rest of the flight, and that 100% all the time was the baseline for 150 tons to orbit. I don't think it is a good idea to blame any one thing (let alone the worst thing) and then extrapolate that to the program as a whole. Most of those bullet points are easily more effort to analyze than I put in to this semester entirely, and many we don't have data for.

I think the postcards are cool regardless of who does them. I think it's an excellent outreach program. Like a couple levels above the send your name to space thing. Granted I am somewhat biased, as I do have a space postcard of my own hanging up in my bedroom.

How would it land then with just the vactors?

Granted this is from a long time ago and is pulled off of reddit, so accuracy is dubious, but should be in the right ballpark. Non subcooled Lox is 1141 kg/m3, which comes out to 16.6 tons. Non subcooled methane is 8.63kg/m3, so about 8.63 tons.

The 33 don't count for this analysis, this is just about restarting in flight, which is a significantly different environment than ground start.

All 33 don't need to restart, though, I think it is just the ring of 10. Current slightly educated speculation points to an issue with the dynamics of the fuel feed system and not with raptor itself. Some of the support for this is that one of the engines that stayed lit the whole time also failed. A review of the video shows that 9 of the 10 did reignite successfully, just something catastrophic happened over the next 20 seconds.

Gateway has grown on me. It's engineering benefits are questionable, but I've gradually learned the lesson that in this era, cost and engineering aren't what you need to optimize for. The best most cost effective program is going nowhere if you don't have political support, and even if it does its not going to go on for very long. For better or worse, support is the thing to optimize for these days. Artemis is very very good at this. It's gotten legacy contractors, new contractors, democrats, republicans, Canada, Japan, ESA, and many others all behind a Lunar program and Gateway is a wonderful part of that, both as sunk cost infrastructure to point to and a relatively easy place for contractor or international participation. A pit stop in NRHO is a small price to pay if it means that a semi sustainable Lunar program actually happens instead of being cancelled.

Thank you for the confirmation, and double thank you for spoilering the image, I have not opened it and I plan on finding it myself soon.

Wait... there's a vall lake now?

Given that we are talking about solar's flaws... This is definitely a tangential comment, but when discussing space based solar, something that isn't talked about often enough is that it gets rid of solar's biggest disadvantage, which is that it can't act as a baseload power source. There are no no clouds in space, there is no snow in space, there is (almost) no night in space (high orbit), you aren't tied to a peak at a certain time of day, and in the event of overproduction you can either rotate the satellite slightly or beam the excess into deep space. Granted, there's still a bajillion other problems with space based solar, of which the biggest is probably economic, but a guy can dream!

Many months in the making, a new grand tour record jointly designed and flown by @camacju and myself! Music video: Technical details video: Almost 4 tons lighter than the previous record, and we thought of nearly a ton of optimizations during the time it took to fly, so 6.8 is definitely possible. I'm not sure how far this optimization can continue, but I have a hunch that enough stuff will be discovered to make 6 tons a reality some day. Edit: Silly me, forgot the exact mass. 7719kg with Bill, 7673 (or maybe 7674 depending on how it is rounded?) without Bill.

It is also possible that the published timeline accounted for some number of expected engine outs. I don't think this would be the case, but it is possible.

I can't wait until Starship deploys a Starlink, then this silly suborbital vs. Atmospheric unstable orbit vs. Orbit debate can end.