- Hi, it's me Tim Dodd, the Everyday Astronaut.
Last night, Elon Musk updated the world
on SpaceX's Starship development.
Let me tell ya, 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, it's unheard of.
If only there was someone that could answer a few more
of my questions about this program and about Starship.
- That's a nice shirt.
- How's it going?
Thank-you, you know full flow
staged conduction not a bad idea
Mind mic-ing yourself up there?
[Tim Voiceover] After Elon complimented my shirt,
we mic-ed him up and let the cameras roll.
Now, for those of you new to my channel,
we're gonna get into some fairly in-depth rocket science
and 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 staged combustion
cycle and aerospike engines.
There were parts of this interview
that I wasn't really planning to release at first
but, actually think the best thing I can do is just show you
the entire thing, un-cut, from a single camera,
so you can feel like you're right there with us.
- Yeah, first off, thank-you so much for,
you know, talking to me, I mean,
we're underneath your beautiful beast.
- Yeah it's crazy, can you believe this is even here?
- I was here a month ago, literally standing right here,
well not, just over the fence,
and you know you got a tube and a pointy tube,
and now you've got this!
I mean, how do you, how do you do that?
Is it just sheer will?
Is everyone that driven about the goal?
- I don't, I think I've learned a lot of lessons
about how to make things go fast.
And then I've...
propagated those lessons to the SpaceX team
and there's just like an incredibly talented,
hard working team at SpaceX, in fact at times I think,
maybe there's too many talented people at SpaceX.
We have like...
you know, too many talented people,
that we're cornering the market, or something.
You know, but there's like this very talented group
that works super hard and...
The, and just have 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.
And one of the most fundamental errors made
in advanced developments is to stick to a design
even when it is very complicated,
and to not strive to delete parts and processes.
It's incredibly important.
So, this is why the switch to steel was
because the advanced carbon fiber was taking too long.
- Right, right, 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"
- Yeah, is it in the future or not?
If it's not in the future, who cares?
- Yeah, yeah, and you did that, I mean
look at last year, DearMoon, you guys
were kind of in that like, awkward stage
of probably figuring this out right here.
You know, you had the carbon fiber mandrel...
- I think we didn't even have the steel,
I think we were still on the path,
when was the DearMoon thing?
- Almost exactly a year ago.
- That was before the change to steel.
- Yeah, you guys, I mean you showed the
carbon mandrel and everything and you're,
you know, excited about that, but then
all of the sudden we see you switch-
- I canceled the carbon fiber design in October last year.
- Yeah, so just after that.
- Yeah...
- You know, what people don't understand is
that you're the lead engineer, you're literally sit-
- Literally, this is, I was actually at dinner
with some, with a friend and he was like,
"Well, who's the chief engineer at SpaceX?"
Oh I go, "It's me", "No, no" he's like,
"It's not you, who is it?", like okay
it's either someone with a very low ego,
or, I don't know, you know,
but, you know that said,
you know the, like,
you know what I actually used to tell the team,
I was like, "Everyone is a chief engineer",
this is extremely important, and that
everyone must understand how, the, broadly speaking,
all the systems in the vehicle work.
And so that, so you don't have
self-system optimization, cause this is
naturally what happens, you can see
the organizational errors,
The product errors reflect the organizational errors.
So like essentially, you'll see that there's
an interface at this particular,
like, whatever departments you've got,
that will be where your interfaces are.
- Right.
- Instead of like, getting rid of something,
or questioning the constraints, the 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",
and 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.
- Right, which is never.
- As you were saying like, what's the probability that
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, they are,
even our own standards are wrong some of the time.
So, question your constraints, this is extremely important,
and, another thing that like, if you say like,
"What are the mistakes that smart engineers make?",
like, one of the most, one of the biggest
traps for smart engineers is optimizing
a thing that shouldn't exist.
- Yeah, so they'll just sit there and spin on
that thing that's just like,
"Why do we even have this is the first place?"
- Absolutely, so,
When you go through college, and you're like,
studying physics or engineering, I studied physics,
the, you have to answer the question
that the professor gives you, you don't get to say,
"This is the wrong question".
- Right, right, right, yeah.
- But, 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".
- Yeah, and that's what you said last year,
I mean, you kinda said like, "It took us a long
time to frame the question even, because we
didn't necessarily know what it was".
- It took ages to frame the question, I mean, 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,
but his book is so deep, people don't even understand.
But like, in The Hitchhiker's Guide to the Galaxy,
the Earth is a giant computer, and the Earth,
it comes up with the answer- 42.
- Right, yep.
- And, to the question, so what's life,
the answer to life, the universe and everything?
The answer's 42, and they're like,
"What the hell, that doesn't make any sense".
The really, the 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, at the point in which you
can properly frame the question,
the answer is comparatively easy.
- Right, right.
I have one more question for you, I'm working
on a video about aerospikes, it's gonna be about
an hour long video on aerospikes and, you know,
they're like the rotary engine of rocket, you know,
rockets, like the rotary was, it's been advantageous
in some ways, you know, like your-
- Yeah, aerospikes, man, I tell you
- They're cool but, what's the biggest,
what's your biggest beef on them?
'Cause I'm trying to get as much insight on like,
why do you think they, you know, aren't used,
and obviously, I assume, you're not ever going
to an aerospike for a lot of reasons...
- You know, I've internally asked this question
so many times, like, "Guys, don't we, shouldn't we
maybe do an aerospike?", the...
The challenge, so...
And you're going to explain to the audience
what an aerospike is?
- Oh yeah, you're gonna be like the end of this thing,
I've already set it all up, yeah yeah.
- Otherwise you know, "What the hell are you talking about?"
you know?
- You gotta get your combustion efficiency,
so, you know like, there's really two parts to, like,
when you have a rocket engine, what're you trying to do?
You're trying to shoot things out,
as fast as possible, in a straight line.
- Yes, yep, converting as much thermal
and pressure into kinetic energy.
- Yes, exactly, so you have your combustion efficiency,
and 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 flow,
and shooting the molecules out in a straight line,
so that you go in the other direction, Newton's Third Law.
- Yep.
- With a traditional combustion chamber,
you can get to a very high combustion efficiency,
cause the molecules are all sort of bouncing around
in there, they've got a time to combine and do their thing,
and then when you sort of choke it through the throat,
you know, it, that gives them sort of more opportunity
to combine, so you can
Like, we think we can probably get to 90, certainly
98.5, hopefully 99 percent of
theoretical combustion efficiency.
This is so if, God himself came and knitted together
the molecules, you're one percent better, okay
maybe one and a half percent better, that's so,
that's very high efficiency.
- Because of full flow staged combustion.
- Full flow staged combustion, exactly,
you've got a gas-gas interaction,
so you've got two hot gases combining
- Yeah.
- And with a relatively simply reaction, the only
thing that would be simpler would be hydrogen.
But you've got CH4 and O2, that's pretty simple,
you don't have any long chain hydrocarbons,
you know, with kerosene you've got the long chains,
they've gotta break down, they've gotta recombine,
it's a total soup, you know.
Yeah, it's a part like 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 engine?"
The 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,
and this is where methane starts to look really good.
- Yeah, yeah.
- It's like, very hard to get to like 96 percent
combustion efficiency, or even 95 percent
combustion efficiency with kerosene,
but with methane you can get 98 easy,
99 with a little bit of difficulty.
- And, so you don't think, you're just telling me now,
spoiler alert, you're probably never gonna see
a full flow staged combustion cycle
aerospike engine produced by SpaceX?
- You know, if somebody can show
that we're wrong, that would be great.
If somebody can explain, "Wow, you've got a,
there is a way to make your design better",
this is a gift.
- Right, right, right.
- "Thank you for this
great gift, wow, this is awesome".
It's definitely like, the worst thing would be like,
"We wanted to do this dumb design,
and stick with our dumb design", that would be insane.
- Right.
- I would love it if somebody could show how
an aerospike is the smart move,
in which case, we'll just do an aerospike.
- Yeah, then just do an aerospike;
there's a reason they haven't been used.
(chuckles)
Period.
- But maybe, that reason is not valid, you know?
'Cause there's also, there hasn't
been a methane orbital engine.
- Right?
Or a flying full flow staged combustion, yeah.
- So, there's been neither a full flow staged combustion
engine that's seen flight, nor has there been a methane
engine that's seen flight, certainly in a rocket scenario,
I think there may have been some like,
little test things or whatever, but no actual rockets.
So, but I'm very confident that CH4 is the right fuel.
Maybe aerospike is, 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, and that you're
straightening the flow sufficiently.
- To get your expansion ratio
- Yeah
- Yep, awesome.
- Also, if you've got a two-stage rocket, like
I think like, this is the other thing like,
you've got two-stage rockets where your
boost stage is primarily in atmosphere,
and your upper stage is primarily in vacuum,
then you can specialize the, for a vacuum nozzle
and a sea level nozzle, and then you're like,
"Why need the aerospike?"
It's only if you do want, if you want
to try to do single stage, reusable,
then that's when you start like having
to reach for the aerospike.
- Right, yep, that's awesome.
Aerospikes, with Elon Musk!
Thank you so much.
- I would love it if somebody could show it like,
"Hey, you're missing the mark, you could
do this different thing, and this would be a better move",
that would be, thank you, please.
- Right, yeah of course, absolutely.
Hey ,thanks for your time again,
see you soon, pleasure meeting you.
(voices in background)
Oh yeah, we might need to steal your mic,
I mean, I don't know, I can bill you later.
Thanks again for this
- Absolutely.
- I have to say, I've been to IEC 2016, seeing,
that was like, it was almost like awkward back then
cause it was like,
- "You're insane", and now it's like,
"Hey look, I'm not insane."
(laughs)
- Well, you know obviously I'm sane,
but you know, I mean...
(background chatter)
Even when I am exposed to this all day,
it's so like "Holy Smith!"
you know, it's so mad, you know,
to see it actually there, and I was up
in the nose, and I mean I'm gonna
post this later but...
- Jack Buyer's photo, Beyer he got a photo of you
like, I think like peeking out of it.
- Well, like this is the, when I was inside there
- Oh, shoot, no way!
Aw and those are the header tanks?
- Yeah.
- And all the batteries got, what six...
- They've got four Tesla 100 kilowatt hour batteries.
- Yes!
- And we just like, basically welded it
on to the header tanks.
- Right.
- Oh we didn't even talk about that,
you're doing model three motors basically, is that?
- Yeah, for that, I mean, I don't love the,
I think we should, we should just have electro-mechanically
I think we are going to, probably with Mach three,
move to a purely electro-mechanical
actuators for the valves.
Currently, it's electric motors powered,
it's like Tesla motors and batteries that
essentially pump hydraulic fluid into the accumulator
and then the hydraulic piston moves the valve.
But it would be simpler to just have the motors directly-
- Just do it
- Kind of worm drive the valve.
- That's awesome.
- And also the way the header tanks are done
right now is crazy, we shouldn't be carrying
the header tanks like cargo, I mean,
we want the header tanks to be integral
to the tip, so seriously, like just take the tip,
use the tip of the rocket as the half of the header tank,
and essentially mirror the main tanks,
but in small form, in the nose.
So, just have two domes
- Yeah.
- And have the oxygen and fuel
in the tip of the rocket,
not as, not carrying the tanks like cargo,
but having the tanks-
- Just integrated, right?
- Yeah, just a mini version of the big tanks
- Right, oh, and then you don't have an extra wall
and everything too, it's just integrated into,
yeah, yeah, yeah, gotcha.
- Like in the early days of rocketry, like V2
or whatever you know, like the fuel and oxygen tanks
were carried like cargo in the aeroshell.
- Oh really?
- Yeah.
In the early days of aircraft and rockets,
the propellant tanks were carried like cargo
- Right.
- now modern rockets, modern rockets and airplanes,
like the wing is just a fuel tank in, in wing shape.
- Yeah, yeah, yeah.
- Yeah, we should do the same for the header tanks.
- I love it, thanks again .
- Thank you.
- Thank you guys.
(laughs) Sorry, I didn't mean to keep him so long I guess.
- [Man] Why're you looking at me?
(laughs)
- [Man] Was, was I rushing you out?
- (laughs) No, not at all.
- [Man] With everything at the end, "Come on!"
- I'm just trying to kick him outta here, you know?
Wasting all my time tonight, just kidding.
Uh, so that was awesome!
Actually, we've still got a lot more questions
to get answered, and stick around 'cause I'll have
a lot of content explaining some of the topics
we talk about, and sorry about the whole like,
thing on aerospikes, I wasn't planning
to release all that 'cause that's for a video
I've been working on, but whatever,
I guess you get an aerospike video spoiler today, my 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,
but, maybe if we're lucky Elon will continue
to update us on Twitter, or, Elon,
you can always come talk to me any time about all the
nerdy stuff you want, I 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, it wouldn't be a career without you guys,
so thank you so much for your support.
If you want access to more behind-the-scenes things
and exclusive content and access, please consider becoming
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And if you want your own full flow staged combustion
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Thanks everybody, that's gonna do it for me,
I'm Tim Dodd, the Everyday Astronaut,
bringing space down to Earth for everyday people.
(upbeat music)