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SLS vs. Starship
- avmich 6y agoSo ironic Saturn-V is drawn as carrying 140 tons, while Apollo CSM is 30 tons and Lunar Module is 15 tons, yet Space Shuttle is drawn carrying just 27 tons. Definitely a case of apples and oranges.
- Tuna-Fish 6y agoThey are listed with numbers about payload to (quite low) LEO. Apollo CSM and the Lunar Module were launched into a much higher-energy trajectory. The Saturn V could have launched 140 tons to LEO, it just never did. IIRC the most massive thing it ever launched was ~90 tons of Skylab.
- avmich 6y ago> They are listed with numbers about payload to (quite low) LEO. Then one should include the mass of Shuttle Orbiter. That the orbiter is used as a second stage... Saturn-V lists mass of third stage alright. > The Saturn V could have launched 140 tons to LEO, it just never did. No, it never could. It's a popular illusion. The only way to reach 140 was to count parts of Saturn V reaching orbit as payload. When you count payload only, that number falls. It's like counting the mass of Sputnik 1 adding the weight of the second stage of R-7. Or, in other words, a satellite with mass 140 tons couldn't be brought to LEO by Saturn V. To get Saturn V realistic number for LEO in similar sense to Shuttle's 27 tons (did Shuttle ever got 27 tons to orbit? Could it even be launched safely with 27 tons payload, given that it could only land with about 15 tons in the bay?), you should look at ~77 tons of Skylab. There is at least a hint that LEO payload is not all which gets to LEO.
- bobthebuild123 6y agoI think you're confusing mass of the payload with something else. Mass of the payload to LEO is just how much mass is brought to LEO. According to "Alternatives for Future U.S. Space-Launch Capabilities" [0], the Saturn V did in fact bring 140 tons to LEO... [0] https://www.cbo.gov/publication/18196 https://www.cbo.gov/publication/18196
- avmich 6y agoI think people are confusing the mass which appears on orbit with payload. Payload is (as meant when the word "payload" was created) rather the goal; in case of Saturn V it was Apollo stack which needed to be launched to the Moon. Similarly, in Space Shuttle case payload is something which is in the shuttle trunk; that's why typically a shuttle flies. Illustration for why 140 tons isn't the payload of Saturn V is that Saturn V wasn't able, or designed, to launch arbitrary 140 tons to LEO, and Skylab is a implicit confirmation of that. The definition of payload to LEO in case of higher-than-LEO missions can include booster stage and fuel, but then we have another strange case of Shuttle with IUS - the payload could fly higher, and was rather small, yet we don't consider Orbiter's mass as part of LEO payload in this case. Since, as another consideration, we usually consider Saturn V as a 3-staged rocket, not a 2-staged (as flew with Skylab) with a space booster stage which is used for LEO insertion as well as for subsequent translunar injection, it would be logical not to include 3rd Saturn's stage into LEO payload. Then Saturn V LEO payload becomes too small to be meaningful (TLI requires a lot of fuel). It would be better - here - to consider Space Shuttle LEO payload to include Orbiter's mass - that justifies large liftoff weight. As for what's Saturn V LEO payload, this question is better be met with clarifications.
- avmich 6y agoFrom https://www.cbo.gov/publication/18196 https://www.cbo.gov/publication/18196, the link above: "The payload of 140 metric tons is derived from weight data pro-vided in Richard W. Orloff, Apollo by the Numbers: A Statistical Reference, NASA SP-2000-4029 (National Aeronautics and Space Administration, updated September 27, 2005), available at http://history.nasa.gov/SP-4029/SP-4029.htm http://history.nasa.gov/SP-4029/SP-4029.htm. In that reference, 140 mt is the weight of the Apollo 17 command-and-service modules, the lunar module, the spacecraft/lunar module adapter, the instrument unit, and the S-IVB stage (the third stage of the Saturn V), including the fuel remaining in that stage needed to propel the Apollo command-and-service modules and lunar module from low earth orbit to the moon." So this number includes the S-IVB stage and unspent fuel. Which ought to raise the question of the definition of the payload - we don't usually consider launcher's parts among payload mass. > Mass of the payload to LEO is just how much mass is brought to LEO. No, it's usually not that simple - Space Shuttle here doesn't include Orbiter's mass (I think it's a mistake), Sputnik payload didn't include R-7 second stage (I think it's right), Energia doesn't have 0 LEO payload even though it releases the payload below LEO (I think this definition is also more meaningful).
- deleted 6y ago[deleted]
- jccooper 6y agoThe chart is tons to LEO. Saturn V wasn't designed for LEO, but it certainly could have dropped that much there. (Skylab used a pretty fair fraction of that capability.) When you're comparing launchers you have to pick some baseline target orbit. LEO is a good lowest common denominator, but isn't quite fair as launch systems optimized for higher energy orbits (like the Saturn V) lose some of their advantage. But a higher orbit is even less fair to systems designed for LEO; choose anything else, like GEO or lunar insertion, STS would have a big fat 0.
- avmich 6y agoYeah, I know, but the point is Saturn V is shown as carrying to LEO 140 tons - and 140 tons was actual translunar payload (Apollo CSM + LEM, ~45 tons) plus dry 3rd stage (~15 tons) plus unspent fuel in the 3rd stage (about 2/3 of initial load of 105 tons of fuel). At the same time Space Shuttle doesn't show the empty mass (a lot) and unspent fuel (very little) of Space Shuttle "second stage", which is Orbiter, and mentions only payload in the bay of that Orbiter. We could arbitrarily say Energia brings 0 tons on orbit - because it's, strictly speaking, a suborbital rocket, the payload needs to add some ~100 m/s of velocity to get to orbit, this was done to avoid getting empty stage to orbit (so no littering, no necessary maneuver to deorbit). Or, alternatively, we could say Energia brings 170 (!) tons to LEO - indeed, if one pays no attention to factual suborbital speed and adds mass of empty 2nd stage of Energia, which is 78-86 tons (http://buran.ru/htm/rocket.htm http://buran.ru/htm/rocket.htm), one gets this number. So it's important to carefully compare similar things. 140 tons for Saturn V is too different from 27 tons of Space Shuttle by method, not by result.
- ggm 6y agoThank you for a well reasoned argument. I would love some formalism of actual useful lofted weight, vs apparent weight lofted to some stated orbit. Getting 27 tonnes to LEO but leaving 50 tonnes in unstable orbit is not 77 tonnes of useful loft, to me (fictive example)
- ruph123 6y agoOne is for science, the other to realize one person’s megalomanic phantasies.
- horseRad 6y agowow
- atonalfreerider 6y agoThis is a very broad claim. Here is a factual refutation: https://spacenews.com/nasa-certifies-falcon-9-for-highest-priority-science-missions/ https://spacenews.com/nasa-certifies-falcon-9-for-highest-pr... From the article lead: >NASA has certified SpaceX’s Falcon 9 to launch the agency’s most important science missions, giving the agency new options that could result in lower costs. NASA sees reducing launch cost as a top scientific priority. The mission of Starship is to do the same.
- kanox 6y agoSLS is not "for science", it's a jobs program for Shuttle contractors.
- ppur 6y agoEspecially with the way innovation works now, one person's "megalomaniacal fantasies" can easily lead to scientific progress.
- bryanlarsen 6y agoWho is the megalomaniac? Elon Musk or Richard Shelby?
- hwc 6y agoFrom May, 2020. Seems like 50 years ago.
- _Microft 6y agoYeah, in 2020, we actually might want to add the month to the submission title. ;)
- _Microft 6y agoPah, the feeling when your shallow post gets all the upvotes but the link to a Covid-risk calculator of a renowned research institute that you submitted earlier gets none. Priorities, folks, pri-or-i-ties... ><
- agsacct 6y agoSLS is the last major gasp of a military industrial complex that has completely taken over congress. The fact that we're paying $146M for each engine on the SLS (takes 4 to launch) and SpaceX is promising an entire launch for Starship at <100M is obscene. (Oh, and SLS ends up at the bottom of the ocean...Starship you can just refuel). While I don't agree with all thing Musk, he's revolutionized the global spacelaunch industry by reducing costs 10x. Now, totally dominant in an industry, he's making that rocket obsolete in favor of a better one (Spaceship).
- skykooler 6y agoOf course, a large part of the cost of those engines is that they're designed to be reusable (a difficult task with hydrogen/oxygen engines due to thermal shocks and hydrogen embrittlement). This made sense when they were being built for the Space Shuttle. It no longer makes sense now that they are using the same engines for an expendable first stage.
- agsacct 6y agoWhich makes the plans to throw them away with each launch even more silly. They are cobbling together jobs programs from space shuttle components with no real strategy except "worked before" and "we can charge a lot of money for this".
- kanox 6y agoThe $146 million figure is specifically for new engines that are no longer designed to be reusable.
- pfdietz 6y agoReusability doesn't make engines costly. All liquid rocket engines are reusable. They have to be, so they can be tested before being put on the vehicle, and so during development you can keep reusing test articles. The Merlin engines on the Falcon 9 are reusable (and on the first stage, they are reused). They are reported to cost SpaceX just $400K per engine to manufacture.
- LeifCarrotson 6y agoScott Manley's video today talks about the political machines behind SLS: https://youtu.be/WVKC54H3v78 https://youtu.be/WVKC54H3v78
- rbanffy 6y agoLong duration projects face the risk of looking silly when something radically changes the landscape. SLS took the safe route back to mostly expendable launchers from a "reusable" system that was the result of extensive feature creep and left the agency with some psychological scars (and some extremely cool and inspiring museum pieces). As the author says, some things are impossible until they aren't. Starship may still hit a development wall, but, at this point, it's doubtful. If it works, it changes the landscape completely.
- pfdietz 6y agoSLS looked silly from day 1.
- HPsquared 6y agoSuetonius quotes the Roman emperor Vespasian: "You must allow my poor hauliers to earn their bread."
- bryanlarsen 6y agoThe reasoning behind SLS sort of made sense 10 years ago. We didn't know that Starship, New Glenn and Falcon Heavy were coming down the pipe. We decided that the US & NASA needed super-heavy lift capability. Previous attempts to design a heavy lift vehicle were lost to political regime change and congress in-fighting. Previous attempts to design a single-stage-to-orbit vehicle were cancelled due to its virtual impossibility. So NASA & Congress designed a program that was unkillable. It greased too many wheels and lined too many pockets to make it easy to kill. It was also designed ultra-conservatively using mostly existing designs so there was no technical risk. So now when we complain that it's a pork-filled boondoggle that's impossible to kill, that was the plan, and there was a certain logic behind it. It makes no sense in a world with Falcon Heavy, Starship & New Glenn, but who would have predicted that with confidence in 2010?
- Gravityloss 6y agoSLS never made sense. Too big, too expensive, too low flight rate. These all problems contribute to each other. Also, large solid rockets are very troublesome. They can not be fueled on the pad, so they are heavy and dangerous from casting to stacking to launch. There will never be a high launch rate reusable rocket with solids.
- bryanlarsen 6y agoBig was the whole point, people decided we needed the capability to send large masses beyond Earth orbit in a single launch. Anything smaller would mean "giving up" on human spaceflight to the moon or Mars. Doing it in a single launch is silly, but that thinking was widespread at the time. And a low flight rate was also a given. Delta IV Heavy only files about once every 18 months, there's insignificant demand for anything even bigger. That was why NASA decided they had to do this themselves, because it would be insane for any commercial company to build a rocket without a market. And expensive was also part of the plan, you can't spread enough pork to make it unkillable if it isn't expensive. Big, expensive, low flight rate. Those weren't problems, they were requirements.
- 6y ago
- jvanderbot 6y agoWho would have known the SpaceX experiment would work? There is some case to be made that US Gov was overly conservative and not willing to innovate, but I suspect that's safer than using taxpayer money on a SpaceX-like iniative that suffers as many failures as SpaceX did initially. Can you imagine the political fallout? We don't have an appetite for that from the Gov any more, not like we did in decades past. NASA and the US Gov made the decision to fill a strategic gap the only way they knew how (and the way that had worked in the past). Now, other options are emerging, but not available and certainly not certified.
- andromeduck 6y agoLiterally anyone familiar with politics and economics. At a fundamental level, industry responds to price incentives and government responds to political incentives.
- gbear605 6y agoTen years ago, it was unknown if the technology behind SpaceX would pan out. No one doubted that the economics would work if the technology also did.
- jjoonathan 6y agoI didn't think the early SpaceX rockets did much that was technologically novel. The real reason why everyone expected the commercial crew program to turn into big contractor grift is because they saw the same story play out 100 times before and 100 of those times the big contractors found a way to capture the money and send the project into development hell. The 101st time was different.
- bryanlarsen 6y agoThe non-governmental market size for conventional super-heavy launch vehicles is zero.
- jvanderbot 6y agoI think this is a textbook example of hindsight being 2020. Of course it's obvious now.
- samizdis 6y agoRelated to this, I found this article [1] interesting, from Arstechnica in September: Charlie Bolden [former NASA administrator] says the quiet part out loud: SLS rocket will go away [1] https://arstechnica.com/science/2020/09/former-nasa-administrator-says-sls-rocket-will-go-away/ https://arstechnica.com/science/2020/09/former-nasa-administ...
- Diederich 6y agoI can't recommend Tim's channel enough: https://www.youtube.com/c/EverydayAstronaut/videos?view=0&sort=p&flow=grid https://www.youtube.com/c/EverydayAstronaut/videos?view=0&so... (sorted here by most popular, where his most informationally rich material shows up on top.) His material is SpaceX heavy but far from exclusive, and he works very hard to recognize and compensate for any biases he might have when doing deep dives and analysis. There's quite a lot of technical material in many of his videos, presented in an organized, pleasant and approachable fashion.
- scrumbledober 6y agothe channel is one of my top recommendations, but I think another thing that should be pointed out is he posts an article version of each of his videos. I really really wish this was more common.
- throwaway894345 6y agoIt’s crazy to see this here. I knew Tim in college; it’s crazy because he bought this old cosmonaut suit as a prop for his photography and it just kind of took off on random corners of the Internet and then next thing I know he’s doing this stuff with NASA and now he’s on the front page of HN.
- walrus01 6y agoIt's not really fair to put the N1 in the category of successful giant rockets that have flown. Yes it flew, it exploded every time. No third stage of an N1 ever made it to low earth orbit.
- boomskats 6y agoThe title made me think the post was something to do with starship.rs, comparing it with a newer, potentially even better shell prompt that I had yet to hear about. I feel weirdly disappointed.
- generalizations 6y ago> If you love SpaceX, you can thank NASA for that. > If it were not for NASA’s initial investment of nearly $400 million for the Falcon 9 and Dragon spacecraft, SpaceX would not be here. Is this true? I thought SpaceX was well under way before they figured out Falcon 9 or the dragon module.
- gbear605 6y agoSpaceX was well underway, but they would have gone bankrupt without investment from NASA.
- DannyB2 6y agoIdea: Let's take an expensive re-usable engine (left over from the Shuttle) and put it on an expendable launch vehicle!
- danpalmer 6y agoI believe engine re-use is on their roadmap. Not for the first launch, or the second, but I think the aim is to have it soon. That said, it's "re-use" by ejecting them and parachuting them down to a safe landing, so who knows if that will work.
- bbatsell 6y agoYou are thinking of ULA’s Vulcan rocket, and there are indications that their engine reuse plan has been entirely abandoned. Aerojet has modified the Shuttle’s RS-25 engine design to make it explicitly non-reusable (in the hopes of reducing costs).
- danpalmer 6y agoHuh, it looks like I might be. I could have sworn this was a block 1B or block 2 feature, that they were going to eject the engine unit and refurbish it, but looks like I must be mistaking it for the Vulcan. That's a shame they might have abandoned their engine re-use plan.
- nn3 6y agoI find the point that SpaceX has no plans beyond the next step hard to believe. I could imagine they perhaps have no firmly officially approved plans like a full waterfall project, but surely there must be already a lot of trade studies on the next steps, and at least some rough plans. Or maybe the even have approved plans, but with the understanding that they could change quickly as new data comes in. Otherwise a project like StarShip is likely not feasible. For example for a Mars project you must at least have some idea that long term live support is feasible with the chosen size. They likely have that idea based on data from ISS, but I bet there were some preliminary studies on this at least.
- kanox 6y ago> surely there must be already a lot of trade studies on the next steps, and at least some rough plans. Starship was always designed to refuel in Earth orbit, land on Mars, refuel on Mars and fly back to Earth in a single stage. This kind of architecture has never been attempted before and it has a lot of long-term implications for the design, for example the same reentry maneuver must work on two planets and orbital refueling is mandatory. All other rocket designs consider "planetary landing" as something for the payload to worry about.
- BadThink6655321 6y agoWhile I see a lot of discussion about the contents of the article (politics, engineering, etc...) I want to comment on the article itself. Very well done. A delightful read during lunch. Bravo!
- m0zg 6y ago> "Why do both programs exist". For the same reason why we still manufacture tanks, only to then park them in the desert: pork.
- cryptoquick 6y agoTim Dodd is an amazing and pure soul, bless his heart. His fair, thorough, and well-researched explanations of this topic, and others, including his other recent video on just Starship vs Falcon 9 and Heavy, are real eye-openers. And, as others here have said, yeah, hindsight is 20/20, given that the SLS will almost certainly be a boondoggle, and barring any major failures on South Padre or something... inconceivable... its utility will likely be obviated before it even launches. But, even as an avid newspace fan for the past 10+ years, I still have to say, it wasn't terribly obvious Starship would launch on "Elon Time"... or "Elon Time 2.0.", even only two years ago when Elon unveiled "Dear Moon", he hadn't even announced he'd be building Starship out of stainless steel. Yeah, and he builds them like water towers are built, in ring sections, not advanced composites. I shudder to think back even 10 years... Like, since it's pretty much fully reusable, yes, both stages, it could cost less than a million dollars to launch 150 metric tons to low earth orbit, which is pretty handy, because they're using it to launch a network of thousands of communications satellites in ridiculously low orbits that'll probably decay in only a few years and it's looking like that's actually gonna work really well. Yeah, way better than the one time Motorola tried it. Oh, and if you wanted to get 150 metric tons to GTO, you just need a single orbital refueling launch. The moon, mars, just a couple more orbital pitstops. Oh, and it uses a rocket engine design that's never even gotten off the test stand the handful times it was looked into before. Yeah, hindsight's a... cough Oh, did I mention there's a global pandemic? And President Trump got voted out of office. And Apple replaced all their Intel chips with the one they have in their iPads and smart phones, and it wound up being way better. Yeah, Intel's in a pretty tough spot, actually. Oh, and try to find as many Pokemon cards as you can, some people have paid their mortgages off that way. Yeah... Time travel's gonna be hard to explain. Especially since nobody has DVD burners anymore.
- DarthGhandi 6y agoThis reads like a gpt-3 blog.