Starbase Factory Tour with Elon Musk [Part 1]

- Hi, it's me, Tim Dodd, the Everyday Astronaut. Welcome to STARBASE Texas. This is where SpaceX is building testing, and even launching their mars bound rocket Star ship. Today, I'm gonna take you inside the gates and show you things that have never been shared outside of SpaceX.

First of all, we have the ultimate tour guide, Elon Musk, who answers all of my questions and gives us unbelievable insights to the rockets development. We talked and walked around for over two hours. So I'll be cutting this up into three parts. The first two are at the Star Base factory and the last one is at the launch pad.

Each section has a goldmine of valuable information. So make sure you're subscribed. You've got your notifications on and you've got your note pads ready to jot some notes.

Now heads up, we talk about some pretty advanced concepts and subject matter that can be pretty intimidating on first listen, but don't worry, I've got you covered with lots of informational videos here on my channel. So perhaps if you are new to Star ship or really all of this stuff, consider watching my complete guide to Star ship, that'll be a really good overview for you for some of the things that we talk about here in this conversation. And I'll also be linking to some of my other videos that will help out with some of the stuff that we talk about as well. Now you might notice, we mention Soviet rocket engines quite a bit in this conversation.

Maybe it's because I was wearing my new Soyuz shirt that you can get at everydayastronaunt.com/shop, or perhaps it's because I've been working on a complete history and family tree of Soviet rocket engines for almost two years now. And that video is currently in the works and it will be out when it's done. And one last thing, this video is broken up into sections and we have links in the description for those sections.

We also will occasionally be putting up a little map, courtesy of ring Watchers on Twitter that will help you keep your bearings as we're walking around. I think that'll help quite a bit. And we also have an article version of kind of our conversation and some of the key points that we bring up over at everydayastronaut.com. There is a link in the description to that as well. Okay, enough talking, let's go hang out with Elon.

- Is it the camera? Probably with the camera, and then somebody else for the camera. - [Tim] It's just camera envy at this point. He saw me with this and he's like listen- - I'll get my camera out. - [Tim] Yeah, you take a video of me. - So I can take a video of this, of you guys taking the video. - Make sure this is going through there.

Just shoot the screen the whole time. I don't want anything else. - All right, so this is... Okay, so this is I'm being videoed here. And then the video of the video. This is the video on the video of the video.

- Go back there. (laughs) - So I feel like I got here maybe at about the most exciting peak of insanity. - It's definitely a very exciting time, 'cause we are in kind of a final push to complete the launch pad system, stage zero, essentially. So we're saying that the launch system, the tower and the, you know, the chopstick arms to catch the rocket are as complex as either of the stages.

- [Tim] Really? - Yeah, absolutely, if not more. We could produce boosters and ships way easier than we could make the launch site. So therefor I'll say it is harder suddenly than any single booster or ship. - I think that's one of the things people don't even realize is the manufacturing out here, that's kind of one of the things that you harp on so much is how, you know, how that's so important and that's in the long scheme, the hardest part of all of this is just manufacturing.

- I think, currently a factory is underrated and design is overrated. So people generally think that, like this Eureka moment of like you come up with this idea and that's it, now it's good. But the design like this, literally a thousand percent, maybe 10000% more work that goes into the production system than the thing itself. So say like how much effort we put into say designing Raptor versus deciding the manufacturing system it's 10 to a 100 times more effort to design the manufacturing system than the engine. - [Tim] Even of a Raptor? - Oh yeah, absolutely. Especially with Raptor.

Quote basically the amount of effort that goes into the design rounds down to zero. - [Tim] Right, right. - Relative to the amount of the effort that goes into the manufacturing system.

And if this was not true, I'd like 1000 Raptors please. Oh, you can't make them? Oh, okay. - [Tim] Right, right. - So this is like just very fundamentally underappreciated.

If people have not been in manufacturing, especially manufacturing of something that's relatively new, then they don't understand. And they think the design is the hard part, and they think production is like a copier or something like that. This is completely false. - [Tim] It's definitely not as sexy as the end thing.

Like, you know, the end product is very sexy and you know, that's what draws people's attention, but the whole back end of it is what makes it possible. - I can't emphasize enough, I'm trying to correct the misperception that design is the hard part. It is not the hard part. There have been lots of great rocket engines designed. You've spend a lot of time looking at the Russian rocket engine designs. There's some amazing Russian rocket engine designs.

They've been doing stage combustion for a long time. And they've done, I don't know, hundreds of different designs, literally. So the hard part is not, can you design a stage combustion engine? This has been done.

Now admittedly, ours is a higher pressure than before, and it is a full flow stage combustion, but that's a relatively minor increments relative to what the Russians have already done. What is super hard about Raptor is, how do we make a Raptor where the cost per ton of thrust is under a thousand dollars? Yeah, I mean, we definitely don't wanna cut, the fundamental thing that needs to be fixed is the cost per ton to orbit. So things that address the cost per ton to orbit are good.

If humanity will be a multi-planet species, if we get cost per ton to orbit to a point where we can afford to become a space race civilization and a multiplanar species. - [Tim] Right. - So this is, at it's heart, it is a fundamentally an optimization of cost per ton to orbit and then ultimately cost per ton to the surface of Mars. - [Tim] Right. - Well, if you're working on getting the cost of, even when you're starting to think of it as dollars, dollar per ton of thrust, I don't know if anyone's ever considered that as a key metric. That's a new thing that I've never thought about, never considered, well, not even...

- [Tim] Raptor is kind of unique. And now you start also thinking about instead of thrust to weight ratio, when you have a fixed diameter and fixed circle area, you're also worried about the nozzle exit to thrust ratio as being a pretty strong consideration too. - Yeah, you basically end up pulling up all the area under the rocket. So for this version, we have 29 engines.

There is a lot of beeping. I'm not sure having this many things beep is actually helpful. - [Tim] It's a sensory overload. - It's like everything around you is crying Wolf.

- If everything's in danger, nothing is danger - - And you're just got to turn it out. Yeah, exactly. So it's pretty silly, but- - [ Tim] So this is obviously the nose of booster 4. - [Elon] This is basically, that's the inter stage and the fuel tank of booster 4.

- What are the little... So obviously that's where the grid fins go, right? And then what's the thing in between them? - that's basically, that's actually the Mount point. There are two. It's debatable whether this is the right design or not. In fact, it's like the whole design is wrong, just a matter of how wrong. But that's one of the load points for picking up the booster.

It's just like tiny little, it looks small, but it's actually not that small, like close up it's this thing is just high in the air. Like all your sense of perspective is wrong. And when this lands, it has like basically the density of a beer can. An empty beer can. With like some mass, you know, with the engine is obviously- - [Tim] What is the dry mass, are you under 200 tonnes? - We should be under 200 tonnes. (machines beeping) The mass is a moving target.

You often say like, what are propellant residuals when you land? That's a big deal. Like both how much margin on what you have and what are the unusable propellant. Like you can't just go to zero margin, you know? Because you're the things going to like, crater. And it should be under 200 tonnes though. But as a rough rule of thumb, like the engines, including mountain mass are roughly two tonnes. So that's 29 engines at 58 tonnes.

Then the sort of the fuel tank itself, and the oxygen tank, it's probably on the order of... Well, it's a little heavy right now. So maybe it's like 80 tonnes or so. Then you've got the inner stage, we've got the grid fins, batteries and a bunch of other things.

So that's around 20 tonnes, and then you got propellant residuals, which might be on the order of 20 tonnes too. All of that should come to, I don't know, call it 160 to 200 tonnes depending on the sort of final mass numbers. But like right now everything is too heavy, like avionics too heavy. - [Tim] The avionics even? - Yeah. - [Tim] I thought it was just a little- - I mean, it should be, but the grid fins are electrically powered so we have batteries that are energy optimized instead of power optimized.

So like this grid fins only let things work for like two or three minutes. So it's very different from like an electric car, which you wanna have several hours of driving. So it is really, we need power optimized batteries, not energy optimized batteries. This is just a short term thing. So the battery mass can probably drop by maybe a factor of 10. So that's just one example.

- [Tim] Should we back up a little bit so there's little- - Yeah, less banging. - And then we're trying to get that crane in here and do work. - [Tim] You got a lot of people on set right now. - Yeah, I mean, that residuals number is a super big deal on the mass though, because the booster is designed to have 3,600 tonnes of propelling, which is an almost 80% liquid oxygen by mass, like 78%- - [Tim] 'Cause you burn at what? Is it 3,71- - 3.5, 3.7.

- [Tim] Okay, yeah. - And you wanna bias in favor of oxygen because oxygen is dancer and cheaper. So in terms of improving your payload and you know, reducing cost per ton, oxygen is basically plants make it for free and plankton. So it's basically like electricity cost of separation and distillation.

- [Tim] Right. Now, remind me though. Is it like, as far as the ratio goes, fuel OF ratio having a lighter molecule.

Do we kind of want that to be spewing out faster or something, 'cause it's less reaction. It can be accelerated quicker or faster. - Yeah, There's a trade off between... Well, I mean, would you tend to get limited by is you don't wanna go too close to stoichiometric 'cause the heats basically melt your engine. So that tends to limit you on trying to go to higher OF, that's the actual thing limiting you. You tend to hit the stoichiometric melting point before you rollover on ISP.

- [Tim] Okay, okay. - Generally. - [Tim] That makes sense. - [Tim] And remind me of the grid fins. Do they still fold in? - No.

- [Tim] No, is that gonna be permanently that way? - Yeah. I have a rule just implement rigorously is the sort of five step process. First make your requirements less dumb, your requirements are definitely dumb. It does not matter who gave them to you. It's particularly dangerous, if a smart person gave you the requirements, because you might not question them enough. - [Tim] Yeah, you might take it as like gospel.

Like you have to do this. - Everyone's wrong, no matter who you are, everyone's wrong some of the time. So mega requirements is less dumb, then try very hard to delete the part or process. This is actually very important. If you're not occasionally adding things back in, you are not leading enough.

The bias tends to be very strongly towards, let's add this part of the process step in case we need it. But you can basically make in case arguments for so many things, and for a rocket that is trying to achieve, try to be the first fully reusable rocket, there's never been a fully reusable rocket people don't understand. Like this is like the holy grail of rocketry, okay? And so you have to run a tight margins because if you don't run tight margins, you're gonna get nothing to orbit. So you've got to delete the part or process step, it's super important. And you can like hedge your bets. So that's why the grid fins for example, do not fold down because that's a whole extra mechanism that we don't need.

- [Tim] And they just compensated for by having strong enough engine authority to steer it in the little atmosphere. - Actually our simulation show, we don't really need any extra engine authority. As long as the grid fins, you know, basically follow the flow, they're not really disturbing the flow, it's really here nor there. As long as they don't have a high angle of attack, it doesn't matter. - [Tim] A few degrees or something within a degree or two.

- But in any case, it's the thing we could add later. So now these grid fins are humongous. We will go see them. But they're like, I mean, like a dinosaur bear trap. It's like you've build a bear trap or a dinosaur, that's what these things look like.

And if you have a whole mechanism for folding them, that's like clearly a part that we don't need. So this is a good design decision that actually I didn't come up with it, and it was like, great. But it followed the principle of like fleet partly lead the process.

I was like, great, good idea, let's not fold them. Why are we folding them, anyway? It's so random. Whatever requirement or constraint you have, it must come with a name, not a department.

'Cause you can't ask the departments, you have to ask a person, and that person who's putting forward, the requirement or constraint must agree that they must take responsibility for that requirement. Otherwise you could have a requirement that basically an intern two years ago randomly came up with, off the cuff and they're not even have the company anymore. But it came from the, let's say, air loads department. They're like, actually there's no one at our current department that currently agrees with that. This has by the way it happened several times.

- [Tim] So again, it could be literally thought of... - this could be, it's every department. - [Tim] It can be thought of as gospel again, but it might be something that's just totally in passing. Or someone played too much Kerbel and had fins at the top of the rocket. And then it just, you know, it did this.

- These things are often just way more silly than you think. Anyway, so step one, make your requirements less dumb. Step two, delete the part or process step.

If you're not deleting a part or process step, at least 10% of the time, basically if you're not adding things back in 10% of the time, you're clearly not deleting enough. And then only the third step is simplify or optimize. The third step.

The reason it's the third step is 'cause it's very common, possibly the most common error of a smart engineer is to optimize the thing that should not exist. And say, well, why would you do that? Well, everyone has been trained in high school and college that you gotta answer the question, convergent logic. So you can't tell a professor, your question is dumb.

You will get a bad grade. You have to ask the question. So everyone is basically, without knowing it, they got like mental straight jacket on that is they'll work on optimizing the thing that should simply not exist. I'll give you an example for way back in the day of Falcon 1. So in the original sort of like when Tom Mueller and I were like batting around, like, okay, what should this rocket look like? I think I was literally in like Tom's kitchen or something.

And we had like the spreadsheet and like, okay, we need to like make minimally viable rockets, like with half a tonne or whatever something like that. And then initially the spreadsheet had, we had an NOT / MMH upper stage, so sort of hypergol, upper stage kind of like a varient of the TRW LMD. - [Tim] Which I think Tom worked on, right? - Well, we trained Tom worked on it, he's not that old. It was like a baby, you know, (laughs). A very advanced baby.

But his mentors did work on the LMD. So, you know, lunar module descent engine. Basically a pintel injector- - [Tim] That's right, 'cause that's where the pintel injector comes from.

- You can also deep it and everything. Now the problem with that is, how much this NTO/MMH costs. It's super expensive, okay. It's like a rare chemical. So even if you're like, you know, if Edison and Tesla had a baby and that baby was smarter than both of them combined and said, your job is to optimize an NTO/MMH Upper stage, you're screwed, okay? So like nitrogen tetroxide or monomethyl hydrazine are super expensive and they're also toxic. - [Tim] They're super nasty, yeah.

It's the handling costs alone are pretty appreciable. - I mean, I do think like saving safety is over-corrected on the NTO/MMH. It went from like, nobody had any protection and breathe the fumes all day to it's cyanide. And neither of those are true, it's not cyanide.

You won't die. Bill Gerstenmaier told me like this story of like, when he started at NASA, they actually, I think passed around like a cup of like hydrazine so that everyone knew what hydrazine smell. - [Tim] Nooo....

So like, 'cause it has like a lot more rotten egg smell or something like that. So he literally opened a cup of hydrazine and like, obviously he's still alive. So that's an example of like, don't optimize this thing that shouldn't exist. We should not have NTO/MMH upper stage. Now Dragon does have that, but that's because Dragon's got to do a lot of like nuanced firings of the Draco engines, you know, with very short pulse durations.

And trying to have something that's not hypergolic is very difficult and it can be done, like, not hypergolic and not cryogenic. Now you options tend to suck. So, you know, they start going down the peroxide barking up peroxide tree or something like that. Or super esoteric mono props. And that's like the again back to big money.

- [Tim] That's step three. - Yeah, so exactly. Thanks to these quite laborious, sorry for the laborious explanation here, and then finally you get to step four, which is accelerate cycle time. You're moving too slowly, go faster, but don't go faster until you've worked on the other three things first. If you're digging and you're great, don't dig it faster, stop digging your grave. But you can always make me go faster.

And then the final step is automate. And now I have personally made the mistake of going backwards on all five steps multiple times. So I have to repeat this. - [Tim] Well on Model 3 Yes, multiple times, but on Model 3. Where literally I automated, accelerated, simplified and then deleted.

But like one example I've talked about before, is like the, they were these like fiberglass mats, on top of the bottle three battery pack, they were in between the full pan and the battery. And it was one point Chuck in the battery pack production line and I was like, basically living on the battery factory production line, like probably fixed the line. 'Cause it was like choking the entire Model 3 production program.

So the first mistake was we should not have... I like try to fix the automation, like make the robot better, make it like move faster, shorter path, increase the torque, delete the reverse 720 degrees on the bolt. 'Cause that's unnecessary. Just go forward fast on a 20% rate at a 100% rate. And instead of spackeling glue on the entire battery pack, just put little dabs of glue because the fiberglass mask was sandwiched between the battery pack and the floor plan anyway.

So all you need is like somebody to hold it in place until put the backpack into the car. So automating was a mistake. Then accelerating was mistake. Then optimizing was a mistake. And finally I said, what the hell are these mats for? And I asked the, the battery safety team, 'cause I was like, what are these mats for? I said are they for fire protection or something? They said, "No, they are for noise and vibration. "So you don't get that."

And I said, "But you're the battery department." And I asked a NVA noise vibration analysis team, what's it for, they said fire safety. So literally it was like being in a Goldberg cartoon. It was like actually, I feel like I'm in a Goldberg cartoon quite frequently. So I'm like, you know, are we in like some simulation where I'm like trapped in some like Kafka esq. / Goldberg cartoon situation, but that's what it feels like a lot.

So then finally, okay, great. Let's try a car with the fiberglass mats and without, and they put a microphone in both, and see if you could tell the difference. You can not. In fact, I was like, which one is which? So we just deleted them and just bypass this $2 million robot cell as a complete pile of none sense. Another mistake that has to happen in production is too much in-process testing.

So when you were first setting up a production line, you don't know where things are breaking. You don't know where things are breaking, so you'll test like working process at various steps and 'cause you wanna isolate where's the mistake occurring? So a very common issue with production lines is to not remove the end process testing after you diagnose where the problems are. So basically if you have like a very high acceptance, like if things are getting to end of line testing and are passing, then you don't need to do in-process testing.

But what used to happened is they'll be like an initial development engineering team that will be like basically debugging the production line, but then they will forget to take out the in-process testing steps. So then what happens is the in-process tester will often choke the cycle time. Choke took the line production time. It'll be like the limiter and also have some number of false positives and false negatives.

But they'll be like false positive, like then you're like rejecting good parts. So really in volume production, if things are working well, you're really just taking a risk, will this subsystem be rejected in the training production process or at the end. And so you just really wanna move things pretty much, almost always to just test at the end line, and that's it.

Maybe there's like one or two in-process steps that are hard to test an end of line, but basically remove almost everything. And there is another thing with battery pack where, this is so crazy. Like one of the things the battery pack has to do is to resist water ingress, so it has to be leak proof. So if you drive through deep water, water doesn't come into the battery pack you're short of battery back. You might have seen some of the videos of like people driving Teslas in like extremely flooded waters, where it's like half underwater. Yeah, like there was literally a guy, I believe in Kazakhstan literally drove a model S through a submerged water tunnel.

All the other cars were out and he basically steered the car with the wheels and use the wheel rotation, like a boat and drove out the tunnel. So it's important to have the battery pack resists water ingress. But then instead of us doing a pressure test on the battery pack, we were actually pressurizing the inside of the battery pack which was the wrong direction. And the battery pack lid was glued. But, you know, we basically had resin that was not cured. And so we were just blurting out the resin, which doesn't a dumb sense.

'Cause you should actually be drawing your vacuum on the front of pack and not pressurizing it. And especially not pressurizing it when there's uncured resin is what's holding down the battery pack. So the pack was failing quite often on the pressurization tests, which should have been a vacuum test. - [Tim] Oh, speaking of grid fins. - Yeah, great. - [Tim] Look at that.

Man, that thing is huge. - Yeah, that's right so it's like a- - [Tim] Dinosaur bear trap? - Dinosaur bear trap. - [Tim] Oh, wait, that'd just a dinosaur trap wouldn't it? - This is a dinosaur trap. - [Tim] That's insane, honestly. - This thing could catch a T-Rex.

(laughs) - [Tim] Oh my gosh, that's crazy. And of course it's got the serrated teeth, which helping the transonic regimes, right? - Yeah. - [Tim] Is there any other reason for the teeth other than that? - No it's just, well, it actually helps in transonic and subsonic, but the effectiveness is better if you've got a pointy , if it's more pointy basically. There is a lot of pointy-ness, Sorry, hey Marvin. So he just gets crushed under a...

- [Tim] Wow, so how heavy are these guys? - These are, I like... actually I don't know the number off hand, but probably at least three tonnes, I'm guessing. When I say it's like a moving target, this is not the, like I wouldn't take this to the bank. Like it's not, you know... There's quite a lot of mass we can get out of this. - [Tim] It's just good enough for now.

Like that's- - Yeah, it's good enough now. But like, you know, we're basically just needs to be like enough control authority to get this through the atmosphere and positioned well enough so that when the engines light, the engine can correct whatever error is left after that we couldn't take out what the grid fins. - [Tim] Man, that is crazy. Those are huge.

It looks like the motor will mount to the lever arm there, is that just... - So this is, yeah... This will react to onto the dome, basically a fuel dome. So there's like kind of like a C channel around the fuel dome at the top.

And there's a motor that's gonna rotate this with a gearbox and that's basically the load will agree reacted between the circular feature that you see there. And the sort of, I shouldn't say C channel, sort of a L channel on the dome. So it's just a simple sort of ring on the dome. - [Tim] And then is that so, what I'm seeing there, where there's the rope is actually a through on the end here, is that the lever arm for the thing? Or is that just...

- Yeah. - [Tim] ahh I see is slides over, it's like... - Yeah. - [Tim] Okay. - That's where the motor will interact, so yeah. - [Tim] Wow.

- But it's just basically, it's using like Model 3 motors basically. - [Tim] Yeah, which is so cool. - Yeah, might as well use it. - [Tim] So you mentioned, you know, really trying to simplify it. There's been talks that they're not...

Did you say it on Twitter that you're gonna eliminate the cold gas thrusters or hot gas thrusters on the B4, for the first orbital test? - Yeah, well we can move to like maybe a quieter location. I'm pretty sure we can cut the weight of that in half, like that's, you know, we're not even really trying to optimize the gauge. That's just basically plate. That's just like cut plates welded together.

First just got to like making that thing work and then we'll optimize it. - [Tim] Yeah, of course. Which again is some of the Soviet union was so good. It was like minimum viable product basically, get it good enough to fly and test it.

And obviously you guys did that with Starship, big time with 8, 9, 10, 11, 15 was like, let's just get it out there, see what works, see what doesn't and iterate, you know? - Yeah, and if you look at like the various reasons, like why we blew up Starship is like, and you looked at the risk list, none of the reasons that blew up are on the risk list. - [Tim] Really? - Yeah, it was like, no, maybe you can argue like, one of them maybe was on somebody's risk list, but it wasn't brought up beforehand, if you can put it that way. I mean, there's a crazy amount of new technology happening here and it's all evolving simultaneously, we need to iron out like the unknowns sort of thing. Yeah, the unknown are the big ones. - [Tim] Is that the new flaps for 20 down there? - Yeah.

- [Tim] So remind me the numbering scheme. 'Cause you were talking about version two Raptor, the other day, what we've seen so far, and are those original version two yet, like the green nozzles, those aren't version two yet, right? Have you started making version two? - We've made parts of version two. So we've made the thrust chamber assembly.

And we have, I think pretty much finished the design of the pumps, we're gonna make the pumps. So hopefully we'll have either Raptor 2 in about a month we might be testing the first one. - [Tim] Okay, and will that be, you said it you're going to be kind of producing stuff or the prototypes are kind of gonna be always in Hawthorne that eventually gonna be moving mass production to McGregor. - Yeah, we're doing volume production of Raptor and McGregor. We will keep California factory operating basically for development engines and the Raptor vacuum version.

- [Tim] So if you're reaching 230 tonne on version two, what's that gonna be at, like 330 bar? - But technically, I think 298, but I think we should come on, we've got like get two more bar out of that thing. - [Tim] Wait, wait, so even only 300, big air quotes on 300, you're getting to 230 already? - Yeah, but then we're opening the throats and reducing the area ratio. The extra thrust is like, there's a slight, I think we lose two or three seconds of ISP, but we gain a lot more in thrust. And the increase in thrust outweighs the slight drop in ISP. - [Tim] Yeah, especially on the first stage. yeah. - I mean basically any thrust to weight below one is worthless.

- [Tim] It's worthless, yeah. So if we go from .4 to .5, it's a massive leap compared to even... Yeah, yeah. - [Tim] Okay, so that makes total sense. So the Rap Vac currently what that for thrust? Is it still around that same number about 200 tons? - The Raptor vacuum, or RVac as we put it We will actually be the 230 ton gross number is the thrust at sea level of the sea level version of version two of the...

It's essentially it's like helpful to certainly like quibble about like, why are you talking about thrust in tonnes? That's not technically a scientific thing. It's because you can do the math in your head really easily if you have a rocket in tonnes and thrust in tonnes. - [Tim] Right, of course, - That's why, and Newton has got like divide by 10 all the time. Which is like annoying. And then you only get kilograms now you've got to like divide by 10,000 to get tons.

Which is ridiculous. Okay, so you're like, this is absurd. Only a fool would use Newtons in my opinion, if you're designing a rocket. And especially big rockets, 'cause you just like have a zillion Newtons. But if you measure things in tons and you measure thrust in tons, now you know thrust weight very easily.

- [Tim] Is that like the only Imperial thing you measure then? - No, these are still metric tonnes. - [Tim] Okay, that makes sense. I was getting nervous for a second. - The pressure is in bar, 'cause everybody kinda knows like what's one atmosphere. So but Pascal's another trash unit. I hate Pascals.

That's why it's so tiny, it's absurd. - [Tim] We did have a whole segment of units that Elon hates and it's just (laughs). - It's like units that make understanding things more harder instead of easier. But everyone understands like a bar or an atmosphere essentially. And everyone like crew can get their mind around a tonne. Like you have an intuitive sense for a ton.

Like your car is like two tons. - [Tim] You have some grasp, you have some context. - Yeah, if you got hit by a tonne, you'd know what that meant. If you got hit by a Pascal, that's like, I dunno a mouse fart.

(laughs) That's like one Pascal. There's another important principle, which is that, you really want everyone to be chief engineer. So if everyone is chief engineer means that people need to understand the system at a high level to know when they are making a bad optimization. It's like, like when they are like, because we've done this many times where we've like put immense effort into reducing the engine mass, but hardly any effort into reducing proponent residuals or like order of magnitude, less evidence reducing proponent residuals.

And then you land with a literal ton of unused fuel. And actually we still kind of do that with Falcon 9. It has about a tonne of unused fuel upon landing, which is pretty annoying. - [Tim] Oh, that's still not much in the grand scheme of everything.

It's still not much, but that is in context. So it still is quite a bit though. - Yeah, but like we spend so much effort getting a ton out of engines, like, you know, that sort of whatever, like 130 kilograms per engine, like that's, yeah So that's like 120 ish. - [Tim] Wow, look, the sunsets out here are pretty hard to beat. That's insane. God, that's amazing.

So congrats on the HLS solidify a little more today. - That was cool. The GAO was a staunch defender of good contracting. - Can we head over and check out the mock-up there? Because there's still a lot that we don't know about HLS publicly, at least. I assume that, you know, a decent amout more.

- I don't know if I do, but... - Well, first off, I guess the most obvious one that I'm excited is those thrusters. - So the thrusters are a good example of running that algorithm I just mentioned, laboriously mentioned, which is, a question to the requirements, making requirements based on deleted part. When we're looking at, what does the booster actually need to do with stage separation? If you put rotation into the stack like before you turn off the main engines. So they both rotating.

They're gonna rotate and just- - [Tim] Wait, sorry. Like pitching and yawing or rolling? - So like you got the integrated stack. We do this with... - [Tim] with Starlink! - with Starlink. So we rotate the stage and- - [Tim] And kind of fling it out. - Yes, but they basically have different amounts of an inertia, essentially rotational maybe to linear inertia. They basically move at different rates.

So if you rotate the thing, depending on where you are, you will move at a different speed. And so it automatically separates if you rotate and then separate. So there's no actual separation mechanism for the Starlink satellites and they technically can bump into each other and occasionally do, but if they bump into each other, for like one mile an hour, doesn't matter. So there's bounce off. - [Tim] It's already made it through the pretty harsh environments of launch.

- Yeah, it's fine. But like, I'm pretty sure this is like, this might be the only ride, we were like literally tussling 60 satellites off with like a hay, bundle of hay, like dry, you know? Dumping the rods that hold them down. Like a hay bale and just flinging them. And it's fine, then they just separate, split up and go to their position. So we've got to stage step, instead of asking the attitude control thrusters, the reaction control thrusters to do the booster rotation, which has a lot of force.

You have the main engines initiate rotation. Now this is quite complex space ballet. 'Cause everything has got to happen in just the right way. But you basically initiate the rotation of the stack, kind of stop the main engines. Then the two will actually separate by themselves.

And you need like a little bit, we have like cold gas ACS, or reaction control system. It's like, depending on who you ask, it's a reaction control system, or an attitude control system. So it's basically like small maneuvering thrusters So you fire those on the ship that gives you a little bit of maneuvering. And then on the booster, we actually have quite a lot of ullage gas, like basically you've got a lot of hot gaseous oxygen and hot methane, which actually have, you know, if you've got a big enough area, it's got decent thrust and vacuum.

- [Tim] The actual- - The vents. But literally you use to vent to vent the stage. - [Tim] Yeah, so not in a separate bottle, but literally like the ullage of the main tanks.

- Yes. - [Tim] Okay. - So just use the ullage as your thrusters and just control the orientation of the venting. So it is not just venting out sideways, but it is venting in a direction that will just work. Which can be sideways sometimes.

Anyway, we've got like basically a lot of gas in this thing, which would have to actually just vent to vacuum anyway. 'Cause it's got too much gas. And that's just extra mass that you don't need. So if you've got basically enough control authority because of the kicking the whole stack over before main engine cut off, plus using the ullage gas to vent, you don't need a separate hot gas thruster system. You don't even need a cold gas thruster system. You already have hot gas.

Question the requirements, delete the part. - [Tim] But this is only for the booster, right? - Yes. Although arguably, now you mentioned it, it might be wise to do this for the ship too. - [Tim] You'd think that- - At least mostly well- - [Tim] Because the tanks are what, six or eight bar or something? The main tanks? - Yeah, there'll be like six-ish bar.

- [Tim] And so one of those would be pretty low pressure, low ISP gas thrusters. If you're only doing the gas from there, or is there some trick you can do to... - In vacuum, like it's this different in atmosphere. Like six bar in vacuum is actually decent. It's like common to have thrusters in space, thrusters that are, let's say eight bar, like the Draco thrusters for that maneuver dragon are operating around chamber pressure of around eight or nine bar. - [Tim] What? - Yeah.

Like dragon is still in PSI. So it's like 120, 130 PSI. Technically it's a pressure pulse, but you know, so 120 PSI is like roughly eight bar ish, maybe eight and a half bar. So it's not that far from the tank pressure. - [Tim] Right. So you don't even need to store the gas in an even higher, like in a bottle that's like 200 bar or something.

You don't even need to do that to operate RCS. - No, if you've got a hot gas, first of all it's like, we really want the ullage gas to be as hot as possible up to the point where it is impacting the strength of a hull. Like we don't wanna soften the metal so much that it pops basically.

So the hotter the gas is the higher the ISP. So having hot gas is good and it's already there and you already have the pressure vessel and you're gonna choke it away anyway. So obviously you just use for attitude to control.

So like, obviously... Initially you can't do this with the ship because everything's cryo, but once the ship is mostly empty and you drive to orbit, it also is in the same situation with a lot of hot gas. So actually we should really be the vast majority of our maneuverings should be with the hot gas that's in the ship. Thanks, now we are gonna fix that. - [Tim] So the thrusters on HLS that are gonna be around the ring, the renders showed like 24 or something of like- - Those are different.

That's for landing on the moon. - [Tim] Okay, yeah, yeah. Are those pressure fed? Like, what are those? Do you have a name for them yet or anything? - Let's just say like, this is the tentative design right now. But with the agreement with NASA, I think we may see that design evolve and it may be better actually. Like a big question here is like, can you land on the moon with the main engines or do you need a separate thruster system that's way up there. Like basically, if you land with the main engine, you're gonna dig a big ditch in the moon and then fall over.

'Cause you landed in a ditch that you dug. It's like literally dig your own grave. That would be obviously bad. So we don't wanna dig our own grave and then fall in it. But more analysis is like, I think we could probably land with the main engine and not dig a grave and die it, but we would have to prove that, you know, get something that's like, I don't know, the consistency of like lunar regolith and like something that's like a good- - [Tim] A good analog.

- Analog of that, and then like land the ship in that and see how big is the hole that we're digging. If you've got low pressure engines that have high up naturally, you're not gonna dig a hole basically. So that's kind of like the sure thing. But I think if we can prove that the main engines do not dig a giant hole, then we can land with the main engines and then not have- - [Tim] Any of those, the ring. What about the, are you gonna have any sea level Raptors on the lunar variant or we only have vacuum optimized? - [Tim] Because I assume like on a normal star ship, even at stage separation, you'll probably light all six at first, just to minimize gravity loss or something, right? So you'll still fire all six then probably shut down the sea levels and let the back of them optimize, you know, like they probably do what like, half the second stage burn time or something with sea level or if you? - Well, so the vacuum engines don't gimbal. So you'd have to have some things to provide the control authority.

I mean, technically you could say like, well, if you're in a low disturbance situation, like the moon has no atmosphere. Man, this is beeping city. - [Tim] You wanna move on? - Yeah. If you're not facing like a lot of atmospheric disturbances, then you need much less control authority and you could probably land with three just by differential throttling and three engines.

But if you lost any of the engines, you'd be toast. So probably make sense to, I don't know, probably keep the same config, you know? - Or like you can even just have one in the middle that would offer, you know, a decent amount of gimbal authority and all that. - It's based on how much optimization we're aiming for here.

- [Tim] 'Cause you're only going to make one of these things, right? Or are you planning on like, is NASA wanting multiple or, oh, my word. So by the way, I think there's a good chance that ITAR and comms might not want all of this. Wait until you see part two is unbelievable. And I promise I'm going to get it to as soon as I can. Thank you Elon, for spending so much time with me and allowing me to ask all of the questions I had. It was amazing.

And thanks to the teams at SpaceX for allowing me to share this all with you. And thanks to Cosmic Perspective for helping shoot this and just kind of helping out all the time. Find them on YouTube and on Patreon as well. And I owe a huge thank you to my Patreon supporters for helping make this and everything else we do here at Everyday Astronaut possible. If you want access to our discord channel, where we're probably going to be talking about this conversation a lot or live streams or lots of other fun stuff, head on over to patreon.com/everydayastronaut.

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2021-08-06 02:50

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