A Conversation about Starship
Transcript
0:00Tim DoddHi, it's me, Tim Dodd, the everyday astronaut. Last night, Elon Musk updated the world on SpaceX's Starship development. Let me tell you, the event was amazing. We learned a lot of really cool details, but I'm still a little baffled by the pace of this program.
0:15Tim DoddIt's unheard of. If only there was someone that could answer a few more of my questions about this program and about starship. Elon, how's it going? Thank you. You know, full flow stage combustion, not a bad idea.
0:27Tim DoddMind micing yourself up there? After Elon complimented my shirt, we mic'd him. Let the cameras roll. Now, for those of you new to my channel, we're going to get into some fairly in depth rocket science.
0:38Tim DoddAnd if it's over your head, don't worry. Stick around my channel and I promise I'll make sense of all the stuff we talk about like full flow stage combustion cycle and aerospike engines.
0:47Tim DoddThere were parts of this interview that I wasn't really planning to release at first, but I actually think the best thing I could do is just show you the entire thing uncut from a single camera, so you can feel like you're right there with us.
0:59Tim DoddYeah. First off, thank you so much for, you know, talking to me. I mean, we're underneath your beautiful beast.
1:05Elon MuskYeah, it's crazy. Can you believe this even is even here?
1:07Tim DoddI was here a month ago, literally standing right here. Well, not just over the fence and you know, you had a tube and a pointy tube and now you've got this.
1:15Tim DoddI mean, how do you, how do you do that? Is it just sheer will? Is everyone that driven about the goal? I don't know.
1:22Elon MuskI think I've learned a lot of lessons about how to make things go fast and then propagated those lessons to the SpaceX team. And there's just like an incredibly talented, hard working team at SpaceX.
1:36Elon MuskIn fact, at times I think maybe there's too many talented people at SpaceX where like too many talented people that were cornering the markets, but there's like a very talented group that works super hard and just taking the general approach of if a design is taking too long, the design is wrong and therefore the design must be modified to accelerate progress.
2:05Elon MuskOne of the most fundamental errors made in advanced development is to stick to a design even when it is very complicated, and to not strive to delete parts and processes.
2:16Elon MuskIt's incredibly important. So this is why the switch to steel was because the advanced card fiber was taking too long.
2:22Tim DoddRight. Well, and you're not. You're definitely not a sunk cost fallacist. You're like, mister, this is clearly the new path forward. Let's hop on it.
2:30Elon MuskYeah. Is it in the future or not? If it's not in the future, who cares?
2:32Tim DoddYeah. Yeah. And you did that. I mean, look at last year, Dear Moon. You guys were kind of in that, like, awkward stage of probably figuring this out right here.
2:38Tim DoddYou know, you had the carbon fiber
2:40Elon Muskmandrel, you didn't even have the steel. I think we were still on the path. When was the Dear Moon thing?
2:44Tim DoddAlmost exactly a year ago.
2:46Elon MuskThat was before the change to steel. Yeah.
2:48Tim DoddYou guys, I mean, you showed the carbon mandrel and everything and you're excited about that, but then all of a
2:52Elon Musksudden you canceled the carbon fiber design. You. October last year. Yeah.
2:57Tim DoddSo just after that. Yeah. And what people don't understand is that you're the lead engineer. You're literally.
3:04Elon MuskLiterally. This is a. I actually had dinner with some. With a friend and he was like, well, who's the Chief Engineer of SpaceX? I look, it's me. It's like, it's not you.
3:14Elon MuskWho is it? Like, look, it's either someone with a very low ego or. I don't know. But, you know, that said, you know, like, what I actually tell a team is like, everyone is a chief engineer.
3:27Elon MuskThis is extremely important in that everyone must understand how the, broadly speaking, all the systems in the vehicle work. And so that you don't have subsystem optimization, because this is naturally what happens.
3:41Elon MuskYou can see the organizational errors in the, like, the product errors reflect the organizational errors. So essentially, you'll see that there's an interface at this. If you've got whatever departments you've got, that will be where your interfaces are.
4:01Elon MuskAnd then instead of getting rid of something or questioning the constraints, one department will design to the constraints that the other department has given them without calling into question those constraints and saying those constraints are wrong.
4:16Elon MuskAnd you should actually take the approach that the constraints that you are given are guaranteed to be some degree wrong. Guaranteed to be some degree wrong. Because the counterpoint would be that they are perfect.
4:26Tim DoddRight.
4:26Elon MuskWhich is never, as you say, like, what's the probability? This is a Platonic ideal of a perfect part zero. Okay? Basically, so question your constraints. It does not matter if the person handing you those constraints won a Nobel Prize.
4:39Elon MuskEven Einstein was wrong some of the time. So question your constraints. Extremely important. And I think another thing that what are the mistakes that smart engineers make? One of the biggest Traps for smart engineers is optimizing a thing that shouldn't exist.
5:02Elon MuskYeah.
5:02Tim DoddSo they'll just sit there and spin on that thing. That's just like, why do we even have this in the first place?
5:07Elon MuskAbsolutely. Because when you go through college studying physics, engineering, I studied physics. You have to answer the question that the professor gives you. You don't get to say this is the wrong question.
5:20Tim DoddRight, right.
5:22Elon MuskBut in reality we have far more degrees. When you're in reality, you have all the degrees of freedom of reality. And so the first thing you should say is this question is wrong.
5:32Tim DoddYeah. And that's what you said last year. I mean, you kind of said like it took us a long time to frame the question even because we didn't necessarily know.
5:39Elon MuskJust to frame the question. Yeah. It's just like the Hitchhiker's Guide to the Galaxy. Douglas Adams, best philosopher ever, maybe, I think best book in philosophy ever. Hitchhiker's Guide to the Galaxy.
5:48Elon MuskThis book is so deep, people don't understand. But like in the Hitchhiker's Guide to the Galaxy, the Earth is a giant computer and the Earth comes up with the answer 42.
6:01Elon MuskAnd to the question, what's life answer to life of the universe and everything. Answer is 42. And they're like, what the hell? That doesn't make any sense. It's like, oh, really?
6:10Elon MuskThe hard part is the question. The answer is the easy part. You need a much more powerful computer to tell you what the question is. And this is true.
6:17Elon MuskAt the point which you can properly frame the question, the answer is comparatively easy.
6:21Tim DoddRight, right. I have one more question for you. I'm working on a video about aerospikes. It's going to be about an hour long video on aerospikes. And they're like the rotary engine of rocket.
6:30Tim DoddYou know, rockets. Like the rotary was. It's advantageous in some ways.
6:33Elon MuskYeah, they're cool.
6:35Tim DoddBut I know what's the biggest. What's your biggest beef on them? Because I'm trying to get as much insight on, like, why do you think they aren't used? And obviously I assume you're not ever going to an air spike for a lot of reasons.
6:49Elon MuskYou know, I've internally asked this question so many times, like, guys, shouldn't we maybe do an arrow spike? The challenge. So are you going to explain to the audience what an aerospike is?
7:04Elon MuskOh, yeah.
7:05Tim DoddYou're going to be like the end of this thing. I've already said it all up.
7:07Elon MuskOtherwise, what the hell are you talking about? So you've got to get your combustion efficiency. There's really two parts to. When you have a rocket engine, what are you trying to do?
7:22Elon MuskYou're trying to shoot things out as fast as possible in a straight line.
7:26Tim DoddYes, yep. Converting as much thermal and pressure into kinetic energy.
7:30Elon MuskYes, exactly. So you have your combustion efficiency. So what percentage of max theoretical combustion efficiency are you. And then what's your nozzle efficiency, which is really, you know, are you straightening the float and shooting the molecules out in a straight line so that you go in the other direction?
7:50Elon MuskNewton's third law.
7:51Tim DoddYep.
7:52Elon MuskSo.
7:57Elon MuskWith a traditional combustion chamber, you can get to a very high combustion efficiency because the molecules are all sort of bouncing around in there. They have time to combine and do their thing.
8:10Elon MuskAnd then when you sort of choke it through the throat, you know, that gives them sort of more opportunity to combine. So we think we can probably get to 90, certainly 98 and a half.
8:22Elon MuskHopefully 99% of theoretical combustion efficiency. This is. So if God himself came and knitted together the molecules do 1% better. Okay, maybe 1.5% better.
8:33Tim DoddThat's very high efficiency because of full flow stage combustion.
8:35Elon MuskFull flow stage combustion, exactly. You've got a gas gas interaction. So you've got two hot gases combining. And with a relatively simple reaction, the only thing that would be simpler would be hydrogen.
8:48Elon MuskBut you got CH4 and O2. It's pretty simple. You don't have any long chain hydrocarbons with kerosene. You've got the long chains, they've got to break down, they got to recombine.
8:55Elon MuskIt's a total soup. It's like potluck dinner situation. It's very hard to get high combustion efficiency with kerosene. So when you look at the, say, like, what's the theoretical value of, say, a lox kerosene engine as compared to a methane methane engine?
9:12Elon MuskThe kerosene actually looks more compelling than it really is because you can't achieve the high combustion efficiency with kerosene that you can with methane. So you actually want to say, what is the actual achievable combustion efficiency times the theoretical chemical energy that's the real number.
9:30Elon MuskThis is where methane starts to look really good. It's like, very hard to get to, like, 96% combustion efficiency or even 95% efficiency with kerosene. But with methane, you can get 98 easy, 99 with a little better difficulty.
9:44Tim DoddAnd so you don't think you're just telling me now, spoiler alert. You're probably never Going to see a full flow stage combustion cycle aerospike engine produced by SpaceX.
9:51Elon MuskYou know, if somebody can show that we're wrong, that would be great. Yeah. You know, if somebody can explain like, wow, you've got a. There is a way to make your design better.
10:03Elon MuskThis is a gift, right. I would be like, thank you for this great gift. Wow, this is awesome. It's definitely like the worst thing would be like we want to do the dumb design and stick with our dumb design.
10:16Elon MuskThat would be insane.
10:16Tim DoddRight.
10:18Elon MuskI would love it if somebody could show how an aerospike is the smart move. In which case we'll just do an aerospike.
10:24Tim DoddYeah, just do an aerospike. There's a reason they haven't been used, period.
10:30Elon MuskBut maybe that reason is not valid, you know, because there also hasn't been a methane orbital engine.
10:38Tim DoddRight. Or flying full flow stage combustion. Yeah, yeah.
10:41Elon MuskSo there's been neither a full flow stage combustion engine that's, that's seen flight, nor has there been a methane engine that's seen flight. Certainly in a rocket scenario, I think there may be some like little test things, but.
10:52Elon MuskYeah, but no actual rockets. So. But like very confident that CH4 is the right fuel. So maybe aerospike is right. Even though it's not been done before. But you just have to show that your combustion efficiency is not affected and that you're straightening the flow sufficiently to
11:17Tim Doddget your expansion ratio. Yeah, awesome.
11:22Elon MuskAlso, if you've got a two stage rocket, I think this is the other thing. You've got two stage rockets where your boost stage is primarily in atmosphere and your upper stage is primarily in vacuum.
11:33Elon MuskThen you can specialize for a vacuum nozzle and a sea level nozzle. And then you're like, why do you need the aerospike? It's only if you want to try to do single stage reusable.
11:44Elon MuskThen that's when you start having to reach for the aerospike.
11:47Tim DoddRight. Yep. That's awesome. Aerospikes with Elon Musk.
11:51Elon MuskHey, thank you so much. I would love it if somebody could show like, hey, you're missing the mark. You could do this different thing and, and this would be a better move.
11:57Tim DoddThat would be.
11:58Elon MuskThank you. Please.
11:58Tim DoddRight, yeah, of course.
11:59Elon MuskAbsolutely.
12:00Tim DoddHey, thanks for your time again. Yeah, pleasure meeting you. The mic get off here. Oh yeah, we might need to steal your mic. I mean, I don't know. I can bill you later.
12:12Tim DoddThanks again for this.
12:13Elon MuskAbsolutely.
12:14Tim DoddMan. I have to say I've been, I think 2016, seeing that was like it's almost like awkward back then because it was like, you're insane. And now it's like, hey, look, I'm not insane.
12:24Elon MuskWell, you know, obviously insane, but I mean, even when I am exposed to this all day, it's still like holy, you know, it's still mad, you know, to see it actually there.
12:40Elon MuskAnd I was up in the nose. I post this later.
12:44Tim DoddBut Jack Buyer's photo, Bayer, he. He's got a photo of you like I think like peeking out of it.
12:51Elon MuskWell, like this is the. This is when I was inside there.
12:58Tim DoddNo way. Oh, and those are the header tanks.
13:02Elon MuskYeah.
13:03Tim DoddAnd all the batteries you got what, six?
13:05Elon MuskWe got four Tesla 100 kilowatt hour batteries that were just like basically welded onto the header tanks.
13:10Tim DoddRight?
13:11Elon MuskYeah.
13:11Tim DoddWe didn't even talk about that. You're doing Model 3 motors, basically.
13:17Elon MuskI mean, I don't love the. I think we should just have electromechanically. I think we are going to probably with Mach 3, move to a purely electromechanical actuators for the flaps.
13:28Tim DoddRight.
13:28Elon MuskCurrently it's electric motors, just like Tesla motors and batteries that is that essentially pump hydraulic fluid into an accumulator and then the hydraulic piston moves the flap. But it'll be simpler to just have the motors directly worm drive the flap.
13:51Elon MuskYeah. And also the way the header tanks is done right now is crazy. We shouldn't be carrying the header tanks like cargo. I think we want the header tanks to be integral to the tip.
14:01Elon MuskSo essentially just take the tip tip, use the tip of the rocket as half of the header tank and essentially mirror the main tanks, but in small form in the nose.
14:10Elon MuskSo just have two domes and have the oxygen and fuel in the tip of the rocket. Not carrying the tanks like cargo, but
14:24Tim Doddhaving the tanks just integrated. Right.
14:27Elon MuskJust a mini version of big tanks.
14:28Tim DoddRight. Okay. And then because you don't have an extra wall and everything too integrated into. Gotcha.
14:34Elon MuskIn the early days of rocketry, like V2 or whatever, you know, the fuel and oxidizer tanks were carried like cargo in the Aeroshell.
14:40Tim DoddOh really?
14:41Elon MuskYeah. In the early days of aircraft and rockets, the propellant tanks were carried like cargo.
14:47Tim DoddRight.
14:47Elon MuskAnd now modern rockets, modern rockets and airplanes, like the wing is just a fuel tank in wing shape.
14:54Tim DoddYeah, yeah, yeah, yeah.
14:55Elon MuskWe just do the same for the header tanks.
14:56Tim DoddI love it. Thanks again.
14:58Elon MuskAll right, thank you.
14:59Tim DoddYep. Thank you guys.
15:04Tim DoddSorry, I didn't mean to keep him so long, I guess.
15:06Elon MuskWhy are you looking at me?
15:12Tim DoddNo, not at all.
15:15Elon MuskCome on.
15:16Tim DoddI'm just trying to kick him out of here, you know. Wasting all my time tonight. That was awesome. We've still got a lot more questions to get answered and stick around because I'll have a lot of content explaining some of the topics we talk about.
15:31Tim DoddAnd sorry about the whole thing on aero spikes. I wasn't planning to release all that because that's for a video I've been working on. But whatever. I guess you get an aerospike video spoiler today.
15:41Tim DoddMy bad, sorry. In the interview I didn't really get much time to talk about like heat shields or the super heavy booster or what the interior of starship might look like.
15:49Tim DoddBut maybe if we're lucky, Elon will continue to update us on Twitter. Or Elon, you can always come talk to me anytime about all the nerdy stuff you want to.
15:58Tim DoddI love it. I think you did too. I owe the biggest thank you to my Patreon supporters. You guys have helped take this little passion and hobby into a career.
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16:39Tim DoddI wouldn't be doing any of this stuff if you weren't doing crazy things to get humans off this planet. So thank you guys. Everydayastronaut.com shop thanks everybody that's gonna do it for me.
16:49Tim DoddI'm Tim Dodd, the everyday astronaut, bringing space down to earth for everyday people.