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hi it's me tim dodd the everyday astronaut

space is trying some pretty crazy things

with their starship rocket

but perhaps there's nothing

more crazy than letting your

9 meter wide

50 meter tall rocket fall out of the sky belly 1st

and then try to light your engines basically

very last moment in order to go from horizontal

to vertical to hopefully land softly now

the reason they're doing this is so they can make

their terminal velocity as

slow as possible

so the rocket engines don't have to do nearly as much

work slowing the rocket down

now in order to understand what exactly that

all means

there's a ton of physics lessons to unpack here

and seeing all of these spectacular failures

has brought up

a lot of really good questions from you guys

but perhaps there's no bigger question than why

why are they doing that belly flop maneuver

why are they going from belly 1st

and then flipping to tail down

and why are they doing that maneuver so late

why don't they just start that

landing maneuver just a little

bit earlier to make sure there's enough time

to make corrections if

something doesn't go right

but we're also going to look at what other

options and constraints and variables spacex has

with running on different

number of engines is running on more engines

better is starting that landing burn earlier better

and can they use parachutes as a backup if

something goes wrong

and of course we'll answer the ultimate question

will this belly flop maneuver

ever be safe enough for humans

I mean

could you even survive the g forces of that crazy flip

should spacex just scrap this whole idea

and go back to landing

it more like a falcon 9

which is proven to be

highly successful

so today we're going to cover the wonders of

terminal velocity

thrust to weight ratio

gravity drag and engine throttling

to see if we can figure out why

space is pursuing such a crazy landing maneuver

and if we even think that's a good idea

or

if maybe they should just go back to the drawing board

let's get started 3 2 1 song

now right off the bat

in case you haven't watched already

you might want to watch my

complete guide to starship

as we actually go over a lot of things

that are going to be talked about in this video

so it might be helpful if you haven't seen that

or if you have

other questions about starship in general

after you watch this video

give that one a watch

it'll likely help you find some answers

but the point of this

video is to explain the physics behind

the rocket science

that's a try and speculate

but we're going to help you understand why

so when spacex does make changes

which they inevitably will

you'll have some grasp on

why they may have made those decisions

but this is a long video

and like all my long videos

we've got some time stamps for you guys

for easy watching or

quick skipping to these certain sections

you might want to see

we also have the YouTube player broken up

in those same sections

and we have an article

version of this video up on our website at

everydayness

com the links in the description

so that you can quickly search for certain topics

starship is doing something

completely unique here with this landing maneuver

so here's how it works

or I guess how it's supposed to work

starship reenters and falls out of the sky belly 1st

to scrub off as much velocity as possible

while falling

at about 500 meters and altitude

it lights up its raptor engines

gimbals them

full tilt folds in the rear flaps and swings from

horizontal to vertical

so it can land tail down

by having the rear fins or aft fins

or as I might call them delawareans tuck in

and by keeping the nose fins extended

it makes it so the nose has

much more drag and will want to point up

and the tail will want to fall down

which will help to aid in the rotation

in later versions of starship will likely see

powerful hot gas thrusters that could aid in this flip

but as of the making of this video

they've been using purely cold gas thrusters basically

off of a falcon 9

but they only use that to get

into the bell flat for this testing period

but they don't actually aid in the flip itself

because the rocket is lighting its engines up

while it's horizontal

it needs to pull propellant from special tanks called

header tanks

so that the engines don't suck up gas bubbles

because of course

the main drain valves on a rocket's propellant tank

are usually at the bottom of the tank which

for a normal rocket is typically oriented pointy end up

flame end down

while starship is falling through the atmosphere

the propellant will settle on the belly side

of the rocket

otherwise known as the windward side

starship has these special header tanks

that are essentially just reserved propellant

that are nearly full

and have their drain valve at a little bit of an angle

which is perfect for the landing maneuver

but also because the rocket lights attentions

while it's horizontal

it'll inject a lot of horizontal velocity

and then intentionally

over rotate all the way beyond vertical

in the opposite direction

to cancel out that horizontal velocity

once it begins to rotate back to vertical

it tucks in its top flaps and will precisely

control itself down to a nice

soft touchdown

much more like a falcon 9 booster landing

so for now I think we need to answer the most

burning question

why

why are they even doing this absurd maneuver

and not just landing like a falcon 9

since that obviously works really

really well

okay so let's start with the belly flop maneuver

well like we mentioned at the top of this video

and in our complete guide to starship

it's all about scrubbing off as much

velocity as possible

let the atmosphere do as much work as it can

essentially for free

no propellant necessary

but one of the biggest

reasons that starship will be coming in

belly first is

actually to control peak temperatures

and orientation of starship during orbital reentry

which is a huge huge deal

especially when trying to land at a precise location on

earth or mars

now we're not going to be focusing on that

orbital reentry portion in today's video

because I've covered it a bit in some other videos

so let's try and figure out

why starship continues to belly flop

once it's in the

lower portions of the atmosphere when it could

easily straighten itself out

at a higher altitude and land

more like a falcon 9

so the key here is getting your terminal velocity as

slow as possible

terminal velocity is the

maximum velocity and object reaches

while falling through a fluid

such as air

yes air is a fluid

it's when the downward force of gravity

equals the force of drag

so the more drag and object has

the slower its terminal velocity

it's the same

reason why a feather will fall slower than a hammer

well at least here on earth in earth's atmosphere

do them here and hopefully

go hit the ground at the same time

now of course

terminal velocity actually

changes based on local conditions

as the atmosphere gets thicker and thicker

drag gets higher

so the terminal velocity is slower and slower

but as long as your drag is equal to gravity

you are at terminal velocity

even when that velocity number

is changing just like skydiving

if you fall belly 1st

your terminal velocity is at a minimum

and you can spend as much time

falling as possible

while also maintaining a lot of control

with your arms and legs

now imagine if you were skydiving feet or head 1st

you'd fall substantially faster

because the oncoming air has much

less surface area to hit

and slow you down compared to belly 1st

so the atmosphere can't do as much work

and your terminal velocity would be much higher

and if we just look at the belly of starship

versus looking at the bottom of starship

you can see just how much more cross section there is

there is approximately 545

square meters of surface area on the belly side

but only about

70 square meters of surface area

on the base of the rocket

that's 7.8

times more surface area to help slow the rocket down

of course the mass would be the same

no matter the orientation

so if you have 7.8 times more surface area

there's a lot more surface for all the air

to push against

all things considered equal

the terminal velocity will be substantially slower now

granted

the actual coefficient of drag is vastly different

between the concave engine section

and the rounded cylindrical body of the rocket

but even so

the terminal velocity is substantially slower

falling belly 1st

perhaps one of the most fun things

about using starship

as an example of terminal velocity is

they can actually

change its terminal velocity

on how deployed all of its flaps are

while belly flapping

if starship deployed all of its flaps out more

its terminal velocity would be slower because it has

more drag

if it were to tug its flaps in a little more

its drag would decrease

and it would fall faster through the atmosphere with a

higher terminal velocity

now in general

space sex doesn't want the flaps to be maxed out

so either all the way open

or all the way closed because

they would be incapable of

making further adjustments to maintain orientation and

control

they will likely want to be roughly in the middle

remaining relatively neutral

and we can actually see the difference

of velocity in the telemetry of starship

versus a falcon 9

let's take a look at declan murphy's awesome

flight club data of the two

this is a highly accurate simulation of starship

sn8's flight profile and the nrl 108

falcon 9 mission

for these initial medium altitude tests

like we've been seeing

starship free falls a bit

after it gets into the belly flop

it slows down as it gets lower and lower

and into thicker parts of the atmosphere

until it slows all the way down to only

about 90 meters per 2nd

before lighting its engines for the flip

and landing burn

now of course

if starship was falling from a

higher altitude or coming back

in from orbit

there would be a higher peak velocity

but once it gets into low altitudes

and in thicker atmosphere

it should reach terminal velocity which is

very low by the time it lights its engines

and that is great

so now let's look at the falcon 9

notice that

after the entry burn the falcon 9 is back in free fall

it actually speeds up a little after engine shutdown

because the atmosphere is still pretty

thin at 40 kilometers

but then it slows down more and more

and the more

the rocket gets into the lower parts of the atmosphere

the slower it gets

don't forget starship won't ever need to do

any kind of reentry burn

after its orbit burn at all

because it will use

its heat shield to protect itself during re entry

and the entire broad side of the vehicle to slow down

so despite coming in at orbital speeds

and not just suborbital speeds

like the falcon 9

it will only have to do one

landing burn

and that right there is a substantial difference

but even for the final landing burn

staying in the belly flop as long as possible

still pays off

because notice

right before the falcon 9 lights attentions

its velocity is still about 310 meters per 2nd

that's a little

more than three times faster than starship

before it lights its engines for the landing burn

and it still hasn't even

reached the equilibrium of terminal velocity

because at this point

it's still experiencing aerodynamic drag of almost 2gs

so it didn't even reach terminal velocity period

so I guess that's maybe

a huge difference is that starship will

actually hit terminal velocity

and the falcon 9 just doesn't

okay well so what 220 meters per 2nd difference

that doesn't sound like that big of a deal

I mean to get into low earth orbit

you need to go about 7 800 meters per 2nd

so 220 meters per 2nd

that's only a small fraction of orbital velocity

why is this belly flop maneuver worth it

well here's the problem when you're falling

every 2nd you're trying to slow down propulsive

the first 9.8 meters per second of deceleration

are just wasted fighting gravity

so that 235 meters per 2nd can

actually be a lot more

because of something called gravity drag

or gravity loss

but in order to actually

understand gravity losses

we need to 1st

explain thrust to weight ratios and engine throttling

and here's where the fun begins

thrust away ratio perhaps you've heard of it

perhaps you've played lots of herbal space program

like me and you have a pretty decent grasp of it or

maybe you don't have

any idea what I'm talking about at all

and that's fine

so let's imagine a rocket hovering for now

let's completely ignore the atmosphere

if we separate these forces and concepts

it's going to make this a lot easier to learn

so in order to hover

the rocket engine needs to produce exactly as much

thrust as the rocket weighs

in order to explain this best we're going to use

newtons for both the weight

and the thrust of the rocket

since it's a unit of force

an object with a mass of one kilogram weighs

9.8 newtons on earth

this is because

earth's gravity pulls at one

kilogram with a force of 9.8 newtons

and just for fun on mars

the same mass would weigh 3.7 newtons

of course it be just as easy to use

pounds and pounds force in this example

but we'll use newtons despite

me not being very used to it

but it's all relative anyway

so if your rocket weighs 1 000 newtons

otherwise known as a kiloton

and you're producing 1

000 newtons of thrust in the opposite direction

you would hover

because you have a thrust weight ratio of one to one

which means your thrust is

exactly counteracting gravity

and therefore your weight

your net acceleration is zero

because your thrust is exactly counteracting

earth's pole

on your rocket produce

900 newtons of thrust with your 1000 newton rocket

and your thrust to weight ratio will be less

than one to one

specifically 0.9 to one

and you'll go down

for each 2nd to your at this throttle setting

with that thrust away ratio of 0.9 to one

you'll go downward

faster and faster you would be accelerating downward

and if you throttle back up to one to one

you wouldn't go back to a hover magically

you'd actually continue to go down at the same

velocity a thrust weight ratio of one to one

just means your velocity is not changing

so in order to get back to a hover

we need to increase our thrust weight ratio to

over one to one

just to accelerate enough to reach zero velocity

so now let's throttle our engines to produce 1

100 newtons of thrust

which would be a thrust to weight ratio of 1.1 to 1

and we'll start canceling out the velocity

once we get back to

zero velocity

we can return to a thrust weight ratio of one to one

if we want to hover

so now let's get back to where we started

let's go to a thrust away ratio of 1.5 to 1

and accelerate quickly upwards

and again this is very important to remember

if you instantly throttled back

to a thrust away ratio of one to one

you would continue going up at the same velocity

you wouldn't magically hover

so to get back to hovering where we started

we'll hold our upwards velocity until we are close

to where we started

and then we'll reduce our thrust away ratio

below one to one

decelerate until our velocity is at

0m per 2nd

and then increase our throttle back

to a thrust away ratio of one to one

to maintain a hover

right back where we started

it's actually quite hard

to make a rocket hover and maneuver

but it gets even more complicated when you remember

that when a rocket engine is running

it's also burning fuel

so the rocket is getting lighter and lighter

as propellant is expelled

so in order to maintain a thrust to weight ratio of

say one to one

you have to be able to precisely

throttle your engine to produce

exactly as much

thrust as your rocket weighs

even though it's getting lighter and lighter

and of course

throttling an engine is a big big deal for landing

otherwise if you couldn't throttle

you would have to turn on your engines at the exact

right moment

huh that sounds like a really bad idea

right joe barnard okay

so let's take a look at joe barnard from bps spaces

model rocket landing attempts

which he tried to do

exactly this by using solid rocket motors

can't throttle or shut down early

if you start your landing burn too early

and have too much

thrust and you hit zero velocity above the ground

and the engine still running you're going to go back up

if you start your landing burn too late

you're not going to be able to scrub off all your

velocity in time

and you'll smack into the ground

or if you're like joe bernard's rockets

you're going to turn into a beautiful

beautiful land shark

or here's another fun example

the falcon 9 actually has too much thrust with only

one of its nine merlin engines

at minimum throttle to be able to hover

so they have to start the landing burn very precisely

this is called doing a hover slam or a suicide burn

if spacex started too early

they could run the risk of running out of fuel

or hitting zero velocity before they touch the ground

and would fall from an even higher altitude

and of course

if the falcon 9 starts its engines too late

it will engage in an unscheduled disassembly when it

hits the ground

at a very high velocity

turning it into a falcon million pieces

since a single merlin engine can throttle between 100

down to about 40

you can start your landing burn at a point

where your throttle is directly in between the two

so about 70

this allows you to

increase your throttle if you started a little late

or decrease your throttle

if you started a little early

the rocket is continually calculating

its velocity is deceleration

and trying to make it hit 0 meters per 2nd

right when it hits 0m in altitude

it will precisely control its throttle

right up until touchdown

although this is all done

autonomously by the flight computer

which can precisely calculate exactly how much

and how quickly to slow it down

that isn't quite as scary as you might think

in fact you may have done this

a lot like

maybe every single day

lot of us

actually do a hover slam or a suicide burn basically

every day if you drive a car

so today we're actually going to be practicing

our own hover slams and suicide burns and showing you

that by modulating your brake pedal

you're basically doing the exact same thing

as a rocket engine slowing down

so I'm going to be doing this with my friend

trevor colman

so let's say you're traveling at

50 kilometers per hour and there is a stop sign ahead

we want to try and stop

right at the stop sign without ever

letting off the brakes and

without ever touching the accelerator pedal again

in this example the stop sign is the ground

where the rocket falling

and we're using our brakes as the rocket engine

that is slowing us down

but we can even go a little bit deeper

with this example

since letting off the accelerator of your car is like

lighting up your rocket engine

because

you begin to slow down before you even use your brakes

this is called engine braking

and although it's pretty obvious in

lower gears of an internal combustion engine car

it's even more

obvious in a hybrid or an electric vehicle

which have regenerative braking

and with a tesla we can even

change our regenerative braking setting to be

standard or low

which would be the same as changing the rocket engines

minimum throttle setting

so the next time you're driving around town

think about when you let off your accelerator

you just lit up your rocket engine

which will start slowing you down

and as you use your brakes

it's like throttling your rocket engine more or less

it's pretty fun

okay so that's thrust away ratio and hover slams

so how is that affect this gravity drag

gravity loss thing

okay so what the heck is this

gravity drag or gravity loss thing

gravity loss

is when you're using your engine to fight gravity

so let's assume you have a

thrust to weight ratio of one to one

as we know you're not changing your velocity at all

your engines are just fighting gravity

so every 2nd

you're running your engine

with a thrust to weight ratio of one to one

you're just wasting precious propellant

fighting gravity

your engine is trying to accelerate your craft at

9.8 meters per 2nd squared

and so is gravity just

in the opposite direction

now like we talked about to

actually get somewhere we need a thrust away ratio of

more than one to one

since the first bit of propellant will

always be sacrificed to that pesky gravity

and this makes a big difference in the

overall efficiency and performance of a rocket

so let's plot this out

because it's pretty fun to see spelled out

on the left we'll show

thrust to weight ratio

versus how much of the propellant is

actually performing work

which is basically the efficiency of the burn

against gravity

on the right

will show the thrust away ratio versus acceleration

so how much net acceleration the rocket is experiencing

if our thrust to weight ratio is one to one

100% of our propellant is spent fighting

gravity and

0 of our propellant is getting us somewhere

and as you know

that means our net acceleration is zero

if our thrust to weight ratio is 1.1 to one

91 of our propellant is still spent fighting gravity

and only 9 is used

getting us somewhere with the net acceleration of

0.1 g's but this produces infinitely more

work than a thrust away ratio of 1 to 1

since that wasn't producing any

so let's jump up to a thrust to weight ratio of 1.5

to 1

now two thirds of our propellant is wasted to gravity

and one third goes into accelerating the vehicle

so although we only increased our thrust 36

over a thrust to weight ratio of 1.1 to 1

we actually produced

five times the amount of net acceleration

getting us to 0.5 g's

let's do it again

now with a thrust to weight ratio of two to one

now 50 of our propellant is wasted on gravity

and 50

of our propellant goes to accelerating our vehicle

compared to 1.5 to one

we only increased our thrust by 33

but we produced twice the amount of acceleration

if we have a thrust to weight ratio of 3 2 1

only one third of our propellant was wasted

fighting gravity

and two thirds was used to perform work

which is great

so we increase our thrust by 50

and we still doubled our acceleration

and lastly

if we have a thrust to weight ratio of 6 to 1

gravity only eats up about 17

so again we

doubled our thrust

and more than doubled our acceleration

but notice we went from

66 of our propellant producing work

at a thrust away ratio of 3 to 1

up to only 83

with a thrust to weight ratio of 6 to 1

so we're definitely seeing some diminishing returns

and no matter how high your thrust to weight ratio is

you'll never reach 100

of your propellant

performing work because gravity will

always eat 9.8 meters per 2nd squared here on earth

but percentage of how much of your thrust gravity is

eating just keeps going down and down

until it's not really a major factor in the efficiency

of your landing burn

so let's think about a falcon 9 falling from the sky

again

if its thrust away ratio is really low like 1.1 to 1

it would have to start its landing burn very high up

and most of its propellant would be wasted

just fighting gravity

it takes substantially

more propellant to start your burn

this high up

or think of it the other way

if you had a much higher thrust weight ratio

it could do a very short landing burn

lighting its engines at the last 2nd

and only a small fraction of the propellant

was wasted fighting gravity

but the reality is

it's actually not quite as bad as we just made it seem

at least here on earth with earth's atmosphere

and especially towards the beginning of a falcon

9's landing burn

now this is really getting into the weeds on all this

but when the falcon 9 is near terminal velocity

drag alone is

already producing an awful lot of deceleration

there's much

more drag than gravity is pulling down on the rocket

so it's slowing down before the engines even light

but once you light your engines

you of course begin to slow the rocket down

but ironically you're

actually reducing the drag the rocket experiences

so the slower the rocket engine makes the rocket

the more work

it actually has to do to fight off gravity

near the end of the landing burn

it's basically carrying all the weight of the rocket

and our whole thrust weight ratio thing

really matters here the most

honestly crazy to me

the engineers have to factor in all of this stuff

when they're designing these landing profiles

okay so now we know about terminal velocity

we know about gravity drag

and how a high thrust to weight ratio can help

combat it

I think it's time we get into

why

does spacex do the flip from belly flop to tail down

so late

so we finally have

all the pieces of knowledge necessary to explain

why they want to do the flip pretty much

as late as possible

as you know the terminal velocity of going belly 1st

is much slower than engines down

so the longer they stay in that belly flopped position

the less work the engines have to do cool easy

but next we actually have a very

carefully plant and wonderful compromise of

mission planning

every decision has a compromise so

here's where things get pretty fun

so let's make an assumption

we want to be belly flopping

for as long as possible to scrub off velocity

but we also want to land safely and reliably right

so we

do want some wiggle room there and not be doing this

last sight in landing burn

where there's absolutely no margin for error

what options are there

starship has three sea level raptor engines

all capable of aiding in the landing

flip and landing burn

each engine can throttle between about 40

and 100 throttle setting

so we can actually have

some crossovers and thrust options

if we're running on one engine

two engines or three engines

with one engine running

we can produce between approximately 880 kilotons

to 2200 kilotons of thrust

with two engines running

we can produce between 1 760 kilotons

to 4 400 kilotons of thrust

and with three engines running we can produce 2

640 kilotons to 6600 kilotons of thrust

and a good point of reference here

when starship is falling from the sky

before it lights its engines

ways approximately 1.4 million newtons

otherwise known as 1.4 mega newtons

or 1400 kilotons

that's about one

mega newton of weight for a dry starship and about

400 kilotons worth of wait for the propellant

that's left over for landing

with a little bit leftover for safety margins

now of course these numbers are subject to change

as starship gets more and more refined

it'll probably get a little bit heavier

because it has more of a heat shield

but we could see the header tank shrink or whatever

but for now let's just use this as a reference

we actually have a ton of engine options here

but right away

you may notice

we actually have a little bit of a paradox

if you want to start the flip early

you'll need a low thrust to weight ratio

so say one engine at a low throttle setting

which is the least reliable thing

as if you lose an engine

it may take too long to get the other

engines up and running

but if you want to run all three

engines the whole time

you'll have to start the flip scarily late and

awfully close to the ground

because

with all three engines running at low throttle settings

it would still be a pretty aggressive suicide burn

but spacex has the option of lighting all three

engines for the flip

and then reducing the number of engines running

once the vehicle is closer to the ground

so they can have greater fine throttle control

while maintaining some redundancies at engine ignition

which seems like a decent compromise

but the performance hit of starting too early is

actually quite a big deal

in fact I had declan murphy

show the difference between the delta v requirements

for starting your landing burn at two

different altitudes

and real quick reminder here of what delta v is

it means change in velocity and

for rockets

you can kind of think of it like the range of a car

it's the balance of the fuel efficiency of your engine

and how much fuel you have in your car

so the higher the delta v you have

the further you can go

so about the absolute earliest starship can flip is

2.5 kilometers

and that's flipping with two engines

then going down to one engine at

nearly minimum throttle setting

for the entire landing burn

and using basically as much

header tank fuel as possible

then

about the absolute latest starship can flip is down

around 300 meters

and that requires all

three raptor engines running at their

highest throttle setting

full bore pulling 4.5 gs to come to a soft touchdown

so now between these two options is some

reasonable compromise

likely right around the 550 meter mark

like we've seen spacex trying the flip so far

and this balances some some engine out capabilities

and allows for some engine overlapping thrust profiles

and it doesn't have a long

and inefficient landing burn

because when you compare their delta

v requirements at each of these altitudes

you can see there isn't a huge difference between

550 meters and 300 meters

but there is

a fairly substantial performance difference

if you start up at 2.5 kilometers

the result of that delta v savings could be as much

as almost 20 tons of repellent

which could mean

slightly more than 20 tons that you could have put

into orbit which is more than a single falcon 9

has ever launched into orbit period

so that's a lot of mass

but of course it's important to remember for now

with its header tanks nearly full

it's around 30 tons of fuel anyway

so they might as well use

all of it and do whatever is the safest

but maybe in the future we could see the header

tanks shrink

as they aim to increase performance

while still having some redundant options for landing

but 2.5

kilometers is about the earliest starship can do

the flip

period due to the size of the header tanks which

again of course could always change

but then you're just

making it more and more inefficient and not really

any more reliable in any conceivable way

if you were flipping earlier

because let's stop and think about it so far

of the four

starship prototypes that have flown as of the

making of this video

none of them really would have worked out

any better had they started the flip earlier

the exception being maybe sn10 which

had a problem where it was

sucking up some of its helium instead of propellant

which means the rocket hit the ground at two

higher velocity

now of course

there might

always be submissions that have some unique edge cases

or more extreme requirements

for instance a heavier payload during landing may

always require all three

engines running at nearly maximum throttle for landing

but that might not be a safe

or reliable solution for humans

to me it seems like what they're doing now

with lighting of three engines

that the flip is great

because that way if one of them isn't working out okay

they can just

continue to do the flip and the landing on two engines

okay so all of this will allow starship to fall slower

and when timed correctly

it'll use very

little propellant for the landing burn

which will increase the performance of the rocket

since the propellant saved can be used to put more

stuff into orbit

and that's the whole point

so the real gold mine for spacex will be finding that

exact right altitude that balances performance

engine shut down opportunities with

overlapping thrust options between the engines

and leaves them with the fewest chances

to make a big old boom but aren't big

matter how reliable you make it

how is spacex

actually going to make this reliable

enough to make it safe for humans

can they

okay okay let's say everything

works out perfectly and starship can land reliably

this maneuver still looks pretty intense and isn't it

always subject to some spectacular failures

what would it be like if humans were on board starship

can it be safe

is this something your life could depend on

as someone who wants to ride this thing

now for dear moon

we better get into this

well first off

the biggest weakness

we need to remind ourselves that for now

the raptor engines are still in their infancy

they're literally

still in development

and they're getting more and more reliable by the day

they are far from perfect

but spacex is flying and testing these things

at a blistering speed

and they're accelerating

so with general engine reliability

the reliability of this maneuver will go up

drastically like we just talked about

by having landing profiles that will have few

single point failures

it could become much more reliable and on top of this

space will practice this maneuver a ton

since they're planning on flying starship

an insane amount between cargo

and eventually refueling flights

and all these other things

not only in this testing phase

but once it's operational

it'll see an awful lot of flights

and they'll have plenty of time to learn

from successes

close calls and failures

but there is

something that will hopefully help

make this flip maneuver itself

a little bit more reliable if there are problems with

say the engine gumble or something

because spacex is working on powerful

hot gas thrusters

that use high pressure gaseous methane

and high precious gaseous oxygen

that can aid in the flip maneuver

but what if they didn't do that flip at all

would the

hot gas rusher would be powerful enough to just simply

land belly 1st

well

no the hot gas thrusters

will not be nearly powerful enough to be able to

actually slow down an entire starship

but if you had enough of them of course

you could maybe do that but

lugging around all those additional engines

and that extra plumbing adds a lot

lot of complexity

a lot more failure points and a lot of weight

besides that

they'd have to beef up the rocket to handle

landing it horizontally

but more importantly

starship already has

rap engines

which are arguably some of the most

incredible rocket engines ever made

and will substantially outperform hot gas thrusters in

every metric

so

why would they want to land on less efficient engines

but the same thing is basically true for parachutes

I have a lot of people asking me

why they aren't using parachutes as a backup

if the main engines didn't light

or something like that

well the first

and most

obvious reason for parachutes is that they take a

long time to deploy

and you have to deploy them in stages

so you don't create

too much shock and destroy the shoots

and or the lines

if starship is lighting its engines up at say even two

1000m

and something goes wrong

and they need to then deploy the parachutes

that's not even enough time to deploy the small

drug shoots let alone the main shoots

not to mention the sheer weight

of the parachutes and parachute system

they actually weigh quite a bit

between the different shoots

the mortars that deploy them and of course

again beefing up the structure

to handle the loads in that orientation

and from the parachute mounting points

and let's not forget about the sheer

mass of starship at 100 metric tons

when it's dry with absolutely zero fuel on board

it would be the heaviest thing to

ever be carried under parachutes

the previous record was the space shuttle

solid rocket boosters

which weighed about 90 tons

that's right

the space shuttle's sr were

actually the largest parachutes ever

and they had three

drug shoots and then there are three

main shoots which weighed around five tons

just for the parachutes again

not to mention the mortars that would fire it

or the additional structure

from mounting the parachute too

okay okay forget backups

parachutes or backup engines and stuff like that

let's say the flip just become comes 99 99

reliable for landing

can he human even

withstand the g forces of the flip maneuver

well for that

let's take a look at the peak

gs of the landing maneuver

believe it or not

the peak gs of the flip and landing is under 3gs now

granted

they may be in a slightly dizzying mixture of vertical

and horizontal

but they're not even as great as many roller coasters

and of course

there likely could be seats that would

rotate and make it so you

always experienced g forces in the same direction

mostly lying on your back

to spread out the g's as much as possible

to keep you safe

and just look at the actual maneuver

follow the nose where the passengers or cargo would be

someday it doesn't actually move that much at all

yes the tail whips around pretty aggressively

but the nose barely does at all

I think it just looks scarier than it is

at the end of the day

I'd rather experience

the g's of starship than the g's of a falcon 9 booster

propulsive landing

which pulls up to

5gs at certain points during reentry and landing burns

while that's certainly survivable

it's definitely starting to get pretty uncomfortable

of course

no one's writing a falcon 9 booster when it lands

but it just shows how

high the g forces are

in order to recover a booster vertically

so

although the belly flop looks dangerous and nauseating

it likely wouldn't actually be that bad for humans

especially if the seats compensated for the rotation

it probably be no big deal at all

but as far as reliability

well

only time will tell how reliable this actually can be

so with that

I definitely think we need to wrap things up

so spacex is trying something pretty spectacular

and there's

reasons to maybe be skeptical about it at this point

having seen so many failures

but let's not forget this is just the very

very beginning

the raptors aren't very mature yet either

and will definitely get more and more reliable

as they continue development

for those of you that weren't around

during the early days of the falcon 9

many people had their doubts

space could even get it to fly

ever there were scrubs galore

problems and questions coming up

every time they got a falcon 9 to the pad

and then of course there were

many doubts if they could ever get it to land

and at first it did seem like a bad idea

and like something that just might

never be worth their time

but now no one

doubts the merits of spacex landing

and reusing their falcon

9 boosters as of today about 75

of all falcon 9 flights have successfully landed

and been recovered

and about half

of all missions have been on flown boosters

they clearly

have figured out a system that works incredibly well

and has already changed the game

or perhaps you remember when

space started using super chill

propellants for their falcon 9

they were scrubbing constantly

for instance ses 9

one of the first missions to use supercharged props

was scrubbed

four times

because of issues with the supercharged propellant

and people

were questioning whether or not it was worth it

and if they could ever get it to actually just

work out without being super finicky

including ula's tori bruno

but the ultimate question why

we've set it at the beginning and we'll say it again

now that you understand everything

using as much of the rocket to slow down

in the atmosphere as possible

essentially for free

that's a great

reason right there

and then by doing the flip as late as possible

they minimize gravity drag

and they won't waste too much

delta v landing the rocket

in order to fulfill the goal of being a

super heavy lift

fully reusable rocket

they have to squeeze absolutely

every little drop of performance out of the vehicle

in the early days of this testing program

we're going to see a

lot of failures

space will learn a lot of lessons

but they're cranking these things out so fast

they can rapidly iterate and learn at a pace

that will certainly lead to getting results in a hurry

but the reality is

I know the last minute aspect looks scary but frankly

every part just simply needs to work

this all just needs to become more reliable period

and if I know anything about spacex

they will force this thing into being reliable because

they don't seem to take no for an answer

after all nothing that's physically possible

is impossible but at the end of the day

who knows

space could play around with this for a while

and then say

you know what

let's just focus on what gets us the absolute highest

chances of safely landing and recovering period

and then they could make some just drastic changes

I mean

elon's already talking about catching the booster

with the launch tower

and maybe even doing that same thing with starship

who knows maybe someday we'll see them

blowing a bunch of fans up at starship and

catching it in a giant net

I mean

I feel like nothing is off the table for spacex but

for now I'm excited to see them try this

more and more because it sure is exciting

so what do you think

do you think spacex will figure out this maneuver

and make it reliable

and routine or do you think

they'll wind up back at the drawing board

and have to come up with another

completely different solution altogether

let me know your thoughts in the comments below

I will quick

thank you to a lot of people who helped make this

video possible

including declan murphy from flight club io

you guys should definitely be familiar with this

if you're out

ever trying to take pictures of a rocket

be sure and check out his

rocket photographer toolkit

there's a ton of really fun stuff to play with though

too so definitely check out flight club io

is awesome and declan does amazing work

and check them out on YouTube too

because he's doing an awesome job

explaining some of the differences we're seeing

between these missions

and also casper stanley

who made a lot of the awesome 3d renders in this video

check out his rocket explorer app

on the steam store which is

super super cool and another thanks to corey at

sea underscore bass 3d on Twitter

for some of his incredible animations as well

and a lot of the footage you saw from this video

was from the partnership I have

with my friends at cosmic perspective

so ryan scaliness and mariela's bender

who work with me to make

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on launch day

definitely watch their incredible films on YouTube

find their YouTube page right now

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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