The most efficient engines we've flown, the RL-10  (used on the Delta IV and Atlas rockets as part of the Centaur Upper Stage) and the RS-25 , (the Space Shuttle Main Engine) get around 450-460s for their specific impulse. These engines use liquid hydrogen and liquid oxygen. The issue with liquid hydrogen is twofold: it is not very dense, and to keep it from boiling away in liquid form, it needs to be really cold. So you need huge, insulated tanks to store it. Hydrogen is everywhere, but it's kind of a pain to use as rocket fuel.
Merlin Vacuum , which is currently used on the Falcon vehicles gets 311s. The RD-0110 , used on the Soyuz gets 326s. These use RP-1, which is highly refined kerosene. It's super easy to work with. On earth. Where we have 200 years of infrastructure in place to support using hydrocarbons. It takes that infrastructure to refine it into a form that rocket engines can use without gunking up the works with unburnt carbon and other particulate crap.
Raptor uses methane, which is kind of like a jack of all trades between density, efficiency, ease of processing, storage, and ease of use in engines. This is basically how SpaceX seems to operate: rather than optimizing a single part of the system (like trying to get the most efficient engine), they try to optimize from a systems level. I don't really know much more than that, because there hasn't really been a lot of stuff for civilians to read on methane engines. This is kind of the cutting edge of the second golden age of space exploration. This freaking rules, what a time to be alive.
They're optimizing for "real" reusability, as in eventually aiming for airline-like turnarounds. None of the earlier engines you noted were reusable except the RS-25, and given how long it took to turn the Shuttle around one could argue it doesn't really count as "reusable" in sense SpaceX is aiming for.
Aiming for reusability and ease of maintenance leads to different optimization paths, in particular we should expect that any one component is going to be less powerful, it'll need to account for wear & tear, not use once and crash it into the ocean.
But raw performance on a single trip doesn't matter much if you can just deliver the same payload in two trips to orbit instead.
Not just the time but the cost, if you take the figure of how much the space shuttle program cost, and divide it by total number of flights (including the two lethal ones), it cost somewhere between $900 million to $1.1bn every time the thing launched. It was very far from the early 1970s dream of an economically reusable spacecraft.
Except that you're doubling the cost if you have to do two trips.
If the rocket is reusable, then the vehicle cost gets amortized over the total number of trips, and the per-trip cost gets closer to just the cost of fuel (hopefully at least an order of magnitude less than a new vehicle+fuel on each flight).
It’s also a bitch to work with. When it’s not trying to immolate or suffocate you it’s busy turning every metal part it touches to garbage .
Hydrogen + CO2 => Methane + Water
This is an extremely important reaction. Mars, for instance, has effectively unlimited Hydrogen and CO2 which also means effectively unlimited Methane and Water. How just absurdly convenient is that?
But it also plays a major role in things like life support. We breathe out CO2. On Earth where we have an enormous atmosphere this doesn't matter. But in closed systems, such as the ISS or what will be the habitation regions on Mars, this is a major issue that needs to be dealt with or we'd kill ourselves with our own exhaust.
NASA, on the ISS, used to deal with life support by producing oxygen from imported water, and discarding the produced hydrogen. They'd then collect exhaled CO2 from the air using CO2 scrubbers and also discard that. That was a pretty inefficient system that required large amounts of imported water to sustain. Now they use the Sabatier Reaction to convert the exhaled CO2 into water and methane. Only the methane is discarded. And as a result of this, instead of needing to import large amounts of water, now all they need to import is a small amount of hydrogen to keep the reaction running.
On Mars this will result in a really cool system. What will be an increasingly large scale life support system will be literally creating rocket fuel as a byproduct. Of course methane is also a controlled and efficient gas, so it can also be safely used for things like cooking dinner.
 - https://en.wikipedia.org/wiki/Sabatier_reaction
"Raptor is designed to power the new reusable vehicles SpaceX’s is building, the Starship spacecraft and the Super Heavy rocket."
Also they call Tim Dodd an "industry expert"...
I would not be at all surprised if there's a List Of Things Apple PR Hereby Politely Requests That Scott Doesn't Mention.
When I was at AWS I was similarly forbidden from mentioning anything to do with video games to just about anybody, despite not having anything to do with video games myself, and many other topics besides the obvious (e.g. "don't disclose EC2/S3 capacity numbers", "don't reveal how Glacier works"), and in fact there was a whole programme of PR training and tiered permission to speak at conferences or to the press/analysts that boiled down, mostly, to knowing what you could and couldn't say, and how diplomatically you parried questions on the latter.
Either that or Terry Pratchett's law of rewritten rules applies.
 no-one would believe me anyway
 it's a massively redundant array of vinyl records
This appears to me to make each flight much more complicated to pull off, introducing more points for it to fail without contingencies, and it makes me nervous. But, again, I am an just an unenlightened observer from an unrelated field. I don't even play Kerbal Space Program! I'm sure they've weighed a million different options and their risks, and have arrived at this one after a lot of thinking, but it has been bugging me. The stainless steel construction certainly looks beautiful out there in Texas.
This approach is more or less the same as what the starship is doing here, except instead of using a glider trajectory for the controlled landing they instead use retropropulsive landing. This is needed because what SpaceX is landing here is a second stage, not a first stage. Way more heat, way more power.
So they need propulsive landing.
The big difference you're seeing compensated for is that Mars atmosphere is less than 1% dense as Earth. So to slow yourself down you need a much larger exposed surface area. Do that exact maneuver on Earth and you'd get an 'unplanned rapid disassembly' during reentry thanks to the thicker atmosphere. That danger and complexity is also something that's hidden.
I cannot recommend Kerbal enough for anybody even vaguely interested in space. Just absurdly fun and does really help you get a feel for all of these issues.
That is the planned Earth re-entry maneuver. Belly first almost all the way down, using the heat shield on one side, then flipping and completely re-orienting near the ground so that the vehicle is pointed upwards, and then the final burn to land upright.
But it does make sense that this path has arisen from a secondary capability: to land on planets or moons with less atmosphere. It still doesn't make me less nervous about their ability to pulli it off reliably. Here's hoping.
The falcon doors also provide a surprising benefit: cover in the rain. And they are very practical with small children.
Musk is very much responsible for why the team works the way it does. He specifically focused on hiring people who experiment and try out things a lot. He did not want just pure theoretical guys.
So, he knew about a problem, he heard someone mention a possible solution, and he insisted they use that solution.
That is not what designing is.
A system of local optimums is an inefficient system. Sort of the self-identified takeaway of the book _The Goal_, and I haven't stopped thinking about this statement since I read it.
But the raptors on the second stage have to operate efficiently in a vacuuum, but also work well and sea level for the landing. So even taking Mars out of the equation (which we really shouldn't, but just for sake of argument), it's requirements are quite different to anything we've built before.
Methane, which is cryogenic and less dense, ought to deliver more? Otherwise bigger tanks and operational issues will eat out the benefits.
For example, Merlin vacuum has a 1:165 expansion ratio. The RD-58MF has a 1:500 ratio. The Wikipedia article for the RD-58 family shows the increase in Isp from various expansion ratios.
Interesting that using http://rocketworkbench.sourceforge.net/equil.phtml I couldn't get declared Isp (380) for methane-LOX for reasonable nozzle expansion ratios. Maybe the model is too approximate...
If they told you the stats of the material, better strength at cryo tempertures meaning mass reduction, higher melting point meaning minimal heat shielding and great thermal conductivity it would be easy to imagine it was some new super composite. Then your head explodes when they tell you it's 2% the cost of what they were using before and it's so easy to work with they don't even need a factory they can just weld it in a field.
Imo Elon is starting to get into contention for greatest engineer of all time.
Soyouz is simple.
Soyouz is reliable.
Soyouz is cheap.
Soyouz is in use for 50+
Soyouz is still there while NASA has no launcher available nowadays, despite decades of « on the edge innovation ».
Soyouz is great. Its an engineering marvel.
And Starship is likely to become even greater.
Only in relation to other single-use rockets.
SpaceX has been eating russian's (and other countries') space business for years now, simply because they are cheaper.
His nuclear cruise missile program is so lame by comparison.
Building a dynamic, innovative organisation capable of developing a re-usable architecture would be very expensive, and unless they can not just equal but handily beat SpaceX, there's just no money in it. Their current launch systems already meet their military needs, so there's no political support from that quarter either.
Their war chest is not looking too healthy though, the hit to oil prices in the last 5 years depleted a lot of their reserves. Thanks for the correction.
I don't know man, did he design it himself?
Many jurisdictions would still have an issue with him using the title engineer. (edit: it's recently been determined to infringe on first amendment rights . Still applies in Canada)
 https://www.reddit.com/r/spacex/comments/davt2l/cnn_intervie... timestamp around 2:30
 https://www.youtube.com/watch?v=P06X2TZUKZU&list=PLpEqMkxe7X... (From the "Dan Rasky: SpaceX's Collaborative Design Approach" video of the "COTS: Dan Rasky" playlist of "Knowledge @ NASA".)
I was as entranced with the possibility of a permanent extraterrestrial base while watching the presentation last night as I was when I saw the boosters land tandem style in 2018.
What an amazing thing to see happen, the people Elon has brought together have done amazing things on the shoulders of already incredible work.
I wasn't like them, but that ability to understand on a fundamental level, not forget, and then very quickly tackle more and more complex problems so fast was like a superpower. It took me much much longer, without the detailed understanding.
Although its a curious topic, I would have no doubt that whatever temperature cycling they design parts of the structure to go through in their "rapidly reusable" regime, the effects of "heat fatigue" or whatever to call it will have been rigorously assessed .
Steel won't melt at 300-400 Celsius but "handling" those temperatures for 10 minutes will change the properties of the material, possibly by a lot, so you don't need "melting" for structural collapse (Twin Towers style).
As the GP says, if you put cold rolled steel, which has an elastic yield strength of >1500 MPa, at 300-400 Celsius, then it is only a matter of time (30-120 min) till the elastic yield strength sinks to 500 MPa or less.
So either this is a single use device, or the steel isn't reaching temperatures over 250 Celsius, or the steel isn't cold rolled but is a low strength steel instead (although that would have other problems).
> or the steel isn't reaching temperatures over 250 Celsius
That might be the case. The space shuttle had an aluminum structure that would fail at 175C, and now we have 40 years of technology advancements for the heat shield.
Is this why jet fuel can't mel..... ah never mind.
Steel becomes harder and more brittle if quenched (hardening), and softer and less brittle if cooled slowly (tempering).
Cold Rolling steel is done to avoid the heat cycle which would otherwise result in tempering, which is why its specific stats don't strike me as particularly relevant past the first launch.
Heat cycles also have the effect of warping steel.
Smaller grain size leading to stronger material -- this is a result of more grain boundaries as the scale of the grain goes down. Hall-Petch strengthening. A secondary effect is that with smaller grains oriented in random directions the metal is more resistant in general from stresses in all directions; whereas with larger grains you tend to get weakness in a particular direction (along the slip planes.)
This is common knowledge, at least it's basic material physics that I learned in college.
It is more practical to discuss the hardness and ductility at specific temperatures, as well as its ability to keep its carbon content under those temperature conditions.
But I think the word GP was looking for was annealing. Annealed metal bends quite easily (that's the analogy in 'simulated annealing' in optimization theory). For instance the wire bonsai practitioners use is traditionally made of annealed copper. Copper is already pretty ductile but once annealed it's positively floppy. Bending it work-hardens it, causing it to stiffen back up. Eventually one learns that if you bend it just so, it will stay where you wanted it to stay.
You do not want your space craft reconfiguring itself.
"Tempering [...] is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air."
Here's a good description https://www.metalsupermarkets.com/difference-annealing-tempe...
Also, it's a lot easier to foresee the weight of a design than its cost so most space programs use it as a proxy for cost. So generally the space industry would optimize for minimizing weight and not even try to think about how the materials used would affect cost.
Here, specifically, with regard to steel rockets? SpaceX stopped optimizing for weight and used thick steel. SpaceX optimized for cost and practicality. Brute force rocket engineering, rather than "the best performance numbers on paper" which is where a lot of rocket designs seemed to get lost in the weeds of some component that ends up being a massive maintenance mess but gives you "the best performance".
The steel tanks that collapsed in the sixtys? They were so thin they needed pressurization at all times or they would collapse. SpaceX realized that was a design and maintenance risk, and just built thick tanks.
I am so used to seeing space stuff done in clean rooms, and things taking years and years to come to fruition (e.g. hearing about and seeing NASA or ESA probes etc getting made) that to see what is essentially a bunch of guys in a field just welding something together blows my mind.
I mean, is it just the outside that looks like that and inside it is ultra-exotic materials and tanks? Of course the engines are sophisticated machinery, but what about the insides? Are we just seeing the outer shell and it's all unobtanium nano-tube composite on the inside?
Once the temperatures get reasonable, it might be aluminum or or carbon fiber. The passenger/cargo/avionics section are probably the only areas where this would be true, so a bulk of the rocket will be steel.
When Canondale hit the big time, they had one model year where they made the dropouts out of solid aluminum and in the next model year the derailleur hanger was bolted on. It's the easiest part to bend and there's no repairing it. Bad enough for road bikes, spectacularly dumb for mountain bikes.
Nope, it's just steel. Outside shell is the tank.
I think the military was looking at a similar material to replace depleted uranium with something non-radioactive (depleted uranium still experiences alpha particle decay, which is fine if you don't aspirate or ingest it, but a shell can pulverize on impact with a target. Also it's still a heavy metal even if you don't take rads from it).
I thought the point of depleted uranium projectiles was simply the density of uranium, giving them large impact energy for a given volume. If that's the case, titanium (4.5 g/cm^3) will not even be as good as steel (8 g/cm^3), let alone uranium (19 g/cm^3).
Or the F-86 Sabre: https://upload.wikimedia.org/wikipedia/commons/3/39/F86F_Sab...
The most beautiful thing in the world is success.
Both characteristics combine to give a lighter rocket than one built out of Al / carbon fiber.
The price is just the cherry on top.
The number of rings is roughly 35 for Starship, with about ten vertical seams each.
For easier thinking, line the vertical seams up and you see that this gives 50m length per vertical seam from bottom to top of Starship. So there are a total of 500m for that.
35 rings with ~28m circumference add up to about 1km of seams between them.
Now if they can use rolls twice as wide and only a single vertical weld each, then that's 500m between the rings and 50m for a single vertical seam. 550m of welds there instead of 1.5m before. This should speed things up quite a lot and reduce the cost of labour.
Raptor production is the real bottleneck, though.
They are shooting for one per day, no? Based on the differences identified in the three hanging under the Boca Chica vehicle now, it’s still in development.
No, they'll do a helical weld, exactly like large pipes (like this: http://www.xysteelpipe.com/upload/201512118145340710.jpg)
You basically need to do that as the steel rolls off the press, though, which is why they didn't do that for Mk I. They'll need to cold roll the steel onsite.
Composite tanks on few rockets being flown with them are made in one of a kind, purpose built autoclaves
This is exceedingly rare in a pessimistic world drowning in the voice of Luddites and backwards-looking preservationists.
Like always, technology solving real world problems versus politicians (professional or amateurs) creating (and never really solving) self-serving perpetual issues.
Almost certainly the top minds at spacex are focussed on starship, and the 5% number might only be kinda-true because starship is being built with a lot of contractors.
Starship wasn’t built by the Falcon or Crew Dragon manufacturing teams, and the vast majority of the design and engineering currently happening for Starship has long been completed for Crew Dragon.
Let’s also remember that NASA is hardly the only company that pays SpaceX, they have other income sources and what they do with that income is ultimately their choice. Unless they are using NASA money to build Starship there should be no problem.
"Musk said in 2018 that SpaceX was “all hands on deck for Crew Dragon,” and it would be making trips to the ISS by December 2018.
After that, he said, “most of our engineering resources will be dedicated to BFR, and I think that will make things go quite quickly,” he said. BFR was the earlier name for Starship."
"All hands on deck" is not some subjective term, it is naval and means get everyone on deck now to repel boarders.
Elon responded saying he would do whatever it took to go faster, but there was nothing he could do.
The payload of the 2011 version was almost reached by the Falcon 9 itself. That was one of the major reasons for the delay, not design and production issues. The Falcon Heavy profited from all the advancments on Falcon 9 and it made no sense to actually build a Falcon Heavy before Block 4.
In fact the first costumers for Falcon Heavy flew on Falcon 9 instead.
In 2011, FH was supposed to have "arrival at launch site" by 2H 2012. It first launched in 2018 (after arriving at launch site in 2018 not 2012). The same level of delay would mean the first Starship does not reach orbit until ~2025. That seems crazy pessimistic and would be a dramatic departure from the otherwise normal delays faced by SpaceX.
I think it's extremely unlikely that Starship would face FH-level delays. That would cancel the Starlink constellation, cede the space-internet game to others, hand the torch to BO or others working on large projects, and absolutely destroy morale at SpaceX.
I just don't see it happening.
Keeping that in mind, having 5 year delay on brand new design, using totally different materials, new engine, etc isn't far fetched.
Starship has none of those potential delays and has already solved most of the hard problems (as evidenced by the Hopper hopping already). Starship has all of the learnings and experience that FH and F9 didn't have.
There will be delays, sure. But we won't be waiting 5+ years again for a single launch. Those days are over, and SpaceX is proving it.
Some context, I haven't read this yet: https://www.quora.com/What-makes-SpaceXs-Falcon-Heavy-more-t...
> Keeping that in mind, having 5 year delay on brand new design, using totally different materials, new engine, etc isn't far fetched.
The first full size Starship prototype is already built though (within ~2 years of initial announcement? Not behind schedule basically at all, so far?). IIRC for FH it was a ~5 year delay before SpaceX even starting construction on the first parts. The difference with Starship is staggering. The pace is dramatically faster, the risks are reduced up-front, and the tests are planned on a much shorter timeframe.
We would frequently go 6 months to a year and hear no news at all about FH. There is news, updates and progress available to the public on an hourly or daily basis about the Starship progress. Night and day.
Experience from FH and F9 is useful, but it's a totally different type of spacecraft, with different use-cases, different materials, engines, cooling, etc. There's TONS of new stuff that they have to research, experiment, fail, try again, etc, until it's doing even 50% of what Elon promised.
StarHopper seems like it can use those learnings, and that was tested recently. The engine was already functioning on a test stand and mated to Hopper for static fires; the Hopper hop itself is testing the engine, sure, but also the complex math of doing a vertical landing with a gimballing engine, etc.
The general space industry considered reusabable spacecraft that land vertically to be pretty much impossible until F9 and FH did it. But Hopper just does that casually, you don't bat an eye, you don't even comment that Hopper was testing a new rocket dynamics/physics for the math that (almost) only SpaceX has figured out.
I just don't see the pessimism here. I've been watching SpaceX for 12+ years and I don't see any of the same issues plaguing them today as did in the past.
New issues, but not the same ones. The new issues have dramatically smaller turnaround time to resolve.
The days of 5-year SpaceX delays are over.
VTVL isn't new. To do it you need ability to throttle engine and do trust vectoring - once you have that, it's "fairly" simple math and physics.
SpaceX is first company that commercialized it, and huge props for that. No one cracked economy of it before (and it's not 100% sure that spacex did - no one saw their financials).
> New issues, but not the same ones. The new issues have dramatically smaller turnaround time to resolve.
We'll see, but I'm extremely sceptic about it. With F9/FH SpaceX did amazing but incremental improvements to current rocket technology. Starship has tons of uncharted territories.
They are building 4 partially functional prototypes to mess up and learn stuff fast.
I'm certain it will be a long time until it can get to Mars, but LEO within the next 2-3 years is probably realistic.
Starship is designed to land from interplanetary speeds (not just LEO orbital speeds), can re-fuel in orbit, and has the world'd most advanced rocket engines. The jump from F9 -> Starship is substantially larger than the jump from F9 -> FH.
No way, that's where most of the differences are. The Falcon 9 second stage is a classic expendable stage but Starship is a brand new design which aims to be fully reusable.
I know I'm piling on here with this quote but I just don't understand why you'd say this if you'd done the least amount of research. They are about as different as two rockets can be—do you think Starship is "just a bigger version" because it's an upper stage? Because it's built by the same company? Its design and (theoretical, until it flies) capabilities are radically different and expanded relative to F9 stage 2.
What similarities are you referring to? They're designed to be launched atop another, bigger rocket. Other than that...?
FWIW SpaceX is exactly the kind of phenomenon that might spur state investment.
The Artemis thing is like a joke for real, though. After the last 30 years of bullshit we've seen from the US government's manned space exploration efforts I think I'll be living in a SpaceX-manufactured igloo on Titan before Richard Shelby and his obstructionist, pork-slinging ilk manage to put footprints on the moon.
We're talking about rockets here, which should be a million miles away from any discussion of Brexit.
The largest rolling mills in the world are ~4 meters wide. They require backup rollers, ie rollers that push down the rollers that push down the rollers that push down the metal. Bending deflection increases with width^2. A 28 meter wide rolling mill does not exist AFAIK and cannot be built in three months.
It's been 12 hours and I only skimmed the video, so I might be misremembering what he said. My understanding was this: Mk1 is welded from plates so at each layer of the stack you have n-1 welds holding the n plates together. My understanding of his comment was that the steel coils will wrap around the major axis of the rocket but instead of each layer containing n-1 welds to join n plates, there will just be one weld in each layer to join the beginning and end of that coil. That would still leave you with welds joining the different layers of coils but only one "seam" weld along the rocket's major axis.
No real indication he means a spiral.
There are a lot of problems with a spiral. Thin sheets of steel, even hot rolled, are very affected by the rolling process. There's also the weld line going up in a spiral. That will cause uneven heat diffusion and expansion, which is a recipe for disaster given that the skin will be cold enough to liquify helium on one side and boiling hot on the other. Then red hot during reentry. Straight lines don't have the same problems.
Single helical weld.
This of course matters if the seam is weaker than the rest of the metal.
I've been assured time and again that you can make welds that are stronger than the rest of the metal, but my lizard brain thinks they're all liars.
Same exists for most goods - try to buy a dustsheet to cover your room, and you can't buy one wider than 5 meters without a seam
While SpaceX did launch an unpiloted Crew Dragon test flight to the space station this year, a subsequent abort system test failed, leading to the destruction of the vehicle. SpaceX aims to resume abort system tests later this year ahead of the first crewed test flight.
NASA Administrator Jim Bridenstine, it seems, is not happy with the years-long delays of Crew Dragon, as well as Boeing's Starliner spacecraft, especially after seeing SpaceX build Starship Mk1 this year ahead of its own test flight.
"I am looking forward to the SpaceX announcement tomorrow," Bridenstine wrote on Twitter Friday. "In the meantime, Commercial Crew is years behind schedule. NASA expects to see the same level of enthusiasm focused on the investments of the taxpayer. It's time to deliver."
The tales I heard from my father were X-ray scans of their finished, grinded, polished welds and they had to be perfect. Not a hair-sized infraction would be permitted.
I wish he could have gotten into the space industry vs oil refineries. The latter is much harder on a person.
I'm a mediocre amateur welder and I totally understand why.
It's hard on people regardless. And the oil industry is not known for being prudent in looking after their workers' health.
They got real pissed when he filed a workers compensation claim for a hearing aid before he retired. Thankfully he had support from his union.
And the number of stories he's told me where he was nearly killed...
I've no sympathy for the industry.
puts sunglasses on
DHS would like your location...
Somehow my Dad managed to swipe that thing around like he was painting or something. It was impressive.
The https://www.spacex.com/careers/list ? There are currently several entries for Welder (Starship) and Tank Fabricator/Welder.