Why does SpaceX land on a drone ship sometimes and land on land other times?

Why does SpaceX land on a drone ship sometimes and land on land other times?


Hi it’s me Tim Dodd the Everyday Astronaut. SpaceX is now better at landing their Falcon
9 rockets than I am at flying kites… but one question comes up often “Why do they
land on a barge in the ocean sometimes and land on land other times?” and sometimes
we see that SpaceX doesn’t even try to land the first stage at all… In order to answer these questions we’ll
go through the variables that are at play and show you some examples using the industry
standard giraffestronaut in a convertible. Wait what? Yeah, this episode rules… Watching a SpaceX rocket land is maybe the
coolest thing to watch this day and age. If you’re unfamiliar with what I’m even talking
about I suggest you check out my video “Why Throw Rockets Away” or if you need an entry
level vocabulary of rockets, I’d suggest you start here with my series “A Beginner’s
Guide to Rocket Vocabulary” Now we’ve seen SpaceX land their Falcon
9’s on both their Autonomous Spaceport Drone Ship (ASDS) and back on land at Kennedy Space
Center at their landing pad LZ-1.Their two Drone Ships are the sizes of football fields
and are cleverly named “Of Course I still Love You” and “Just Read The Instructions”
which are nods the science fiction book “The Player of Games” So what does determines where the Falcon 9
will land? Well, I’m glad you asked because it’s really
quite simple really – First we take a Runge Kutta Integrator that
will numerically integrate a system of different equations from an initial condition state
vector forward to an arbitrary moment in time. Then we derive the equations of motion for
your vehicle. We need to take into account aerobraking with
some translational equations that are highly-coupled, nonlinear ordinary differential equations
that require numerical routines. I don’t know what any of this means. Whyyy! My brain hurts just trying to read that sentence,
let alone try to do any of the complex math. So let’s start with something we can all
relate to first, ROAD TRIPS! And to be more specific road trips involving
a tow truck pulling a car with 2 astronaut giraffes, you know giraffestronauts. Normal stuff. Our 2 Giraffestronauts are on a road trip
from SpaceX’s HQ in Hawthorne, CA and they want to get to San Fransisco, some 400 miles
away. Now because they don’t have opposable thumbs,
they can’t operate a gas pump, duh! So they need to get there without filling
up. With two giraffestronauts, the car gets 30
mpg, (meaning it can go 30 miles on one gallon of gas) and their car has a 10 gallon gas
tank, giving them a range of 300 miles. If they bring any other giraffestronaut friends
along, it hurts the fuel economy by 2 miles per gallon due to their long, gangly necks. Unfortunately, the car can’t get them there
on it’s own, so they get smart and say, “I know, let’s tow our car part of the
way and then we’ll drive the rest of the way!!!! HUZZAH!” So they call up a tow truck who shows up with
a massive 40 gallon fuel tank. The tow truck on its own can get 10 miles
per gallon with a total range of 400 miles, but then they realize that when they put the
car with its passengers on it, the gas mileage drops to 4.5 mpg, with any additional passenger
decreasing it another .5 mpg. So now with the car and two giraffestronauts
on board, the tow truck’s range drops to just 180 miles. The tow truck driver says, “Ok, I’ll take
you 100 miles so you can get there and I can still get home” In doing so, the truck will
chew through 22.2 gallons to deliver them the first 100 miles, leaving the truck with
just 17.8 gallons to get home, and now that it’s not towing the heavy car and goofy
giraffestronauts, it gets 10 mpg and that’s 178 miles of range, which is easily enough
to get back home. Ok, let’s add another giraffestronaut to
the equation for a total of 3 in the car. The car’s gas mileage will drop from 30
to 28 mpg for a range of 280 miles. So the tow truck driver sighs and says, “ok,
I’ll take you 120 miles, but now at only 4 mpg, I’ll use 30 gallons of gas, leaving
me with only 10 gallons left to get home.” He looks at the map and sees that’ll leave
him hanging out somewhere near Beverly Hills. Which isn’t too bad of a place to hang out. And he’s got a cousin that lives there so
he’ll just hang out there until someone comes and picks him up! And lastly, what happens when we add one more
giraffestronaut for a total of FOUR giraffestronauts in the car, will they still make it to San
Francisco? The car’s gas mileage will drop from 28 to
26 mpg for a range of only 260 miles. The tow truck will only be getting 3.5 mpg
dropping its range to only 140 miles, JUST enough to get get all four giraffestronauts
to their destination. But in this case we’re going to leave the
tow truck stranded way up near Bakersfield and nobody makes it back from Bakersfield,
am I right?! Bakersfield! So, do you see what we did here? By simply adding a few more giraffestronauts,
we quickly altered the trips of both vehicles, drastically. In all of these examples, we were able to
get the giraffestronauts to San Fransisco, but depending on how many of them there were,
we were pushing the limits of how far the tow truck could go and if it could return. I may have lost a lot of sleep thinking about
this… Our parallels here are the first stage of
the Falcon 9 is like the tow truck, the second stage is like the car, and the giraffestronauts
are the payloads. So let’s take a look at three actual SpaceX
missions to see what this looks like in real life. On February 19th, 2017, SpaceX launched one
of their Dragon cargo vehicles on top of a Falcon 9 to the International Space Station
for mission CRS-10. The dragon capsule weighed 4,200 kg. This meant there was plenty of margins left
over for the first stage to turn around and return to Kennedy Space Center and land at
their landing pad, LZ-1. On March 30th, 2017, SpaceX launched an SES
communications satellite to Geostationary Transfer Orbit on a Falcon 9 for mission SES-10. Now this baby weighs nearly 5,300 kg, so it
only had enough margin to land on the autonomous spaceport drone ship about 400 miles down
range. Lastly, On March 16th, 2017, SpaceX launched
EchoStar 23 on top of a fully expendable Falcon 9 to geostationary orbit. The satellite weighs 5,500 KG which pushes
it just beyond what can be recovered. So, just like rockets of the past, the first
stage plummeted into the ocean after only 2:40 seconds of use. To keep the price of the rocket down and to
get the most performance out of the vehicle, they strip it of its landing legs and grid
fins, which looks just plain weird these days! I call it a naked Falcon 9. Much like with our giraffestronauts going
to San Francisco, small changes in a payload can mean big changes in how far each vehicle
can travel. Something to remember is the Falcon 9 1st
stage weighs a whole lot less on its descent without the 2nd stage and payload on top of
it. This means it requires a lot less fuel to
land on its own than it would require if there was all that additional weight on top of it. People have also asked me, “Why don’t
they land that first stage in Africa or Europe?” Their thinking is the rocket is traveling
east, doesn’t that mean the first stage could end up in Africa or Europe? Well, let’s take another look at that map
to see how far it actually is. Oh… we’re just barely off the coast of
Florida still… Notice that even an expendable first stage
that burns all of its fuel still crashes only a few hundred miles off the coast of Florida. A very, very long ways away from Europe or
Africa. But most of all landing on a boat, although
it seems crazy to us humans, has proven to be a very achievable feat by a computer controlled
rocket. But all of this drills in why recovering and
reusing a multi million dollar fine piece of engineering is so important. It’s a shame that the portion of the rocket
that is the biggest and costs the most is completely done after less than 3 minutes
of use. That’s crazy! That’s really expensive. And it only gets used for a little bit of
time. Then nothing happens! *Mumbles* So I think that does it for why SpaceX sometimes
lands the Falcon 9 on land, sometimes the ocean on the barge and other times it doesn’t
land at all. If you have any other questions or comments
about this, leave them in the comment section below. Make sure and hit subscribe so you know when
I make more fun, funny and factual content. Also a huge shout out to my patreon supporters
for helping make this and other Everyday Astronaut content possible. If you want to help contribute, please visit
Patreon.com/EverydayAstronaut Thanks to Declan Murphy of the awesome website,
flightclub.io for the amazing telemetry visuals. Thanks everybody, that does it for me. I’m Tim Dodd the Everyday Astronaut. Bringing space down to earth for everyday
people.

Eugene Islam

100 thoughts on “Why does SpaceX land on a drone ship sometimes and land on land other times?

  1. Some of your audience is retired – youth is only a cruel weight – Vietnam War was huge in 1969 – California was building napalm by the tons along with huge war related industries – we were in a Civil War in Wash. D.C. every spring – set the mood of early space – nuclear war was a reality. You never mention those tiny points. Musk is the new Henry Ford no doubt though. In my lifetime the landing of the Moon was big – then Americans got bored, next was Hubble that saved all programs – people get bored before you know it. You are way too young still. Something to remember. Webb is unknown by the "average" person not your audience – treat us with diagrams not you in your suit.

  2. woah woah there, NASA, JPL and spaceX engineers will haunt you for explaining their work better than them….
    Great video, awesome analogy, Cool suit….
    Here have a SUB….

  3. This reminds me of people trying to outsmart manufacturers in multicopters (the so badly named drones) putting bigger batteries..

    the thing for example is standard flown with a 2000mAh battery (200g) and lasts 10m.. people then go and say "oh but i modified mine and put a 3000mAh! it will fly 15m! ".. but no.. that 3000mAh weights 300g ..extra 100g so the motors need to spin faster and draw more power to lift those extra 100g..so the range wont be 15m.. and it gets worst the more weight as the motors need to draw more and more power spinning faster and losing efficiency due to prop drag and heat..

    planes and rockets work simular.. extra payload or extra fuel will cost you

  4. What does a spent rocket booster look like? How does it land (does it burn up?) and how/are they recovered?

  5. Very good video, simple, easy to understand, funny, cool, but not dumb or condescending. JusT Perfect. keep it up.

  6. Hello there! I was wondering, what about the Falcon Heavy? Will they have three barges? Also, if the payload is extremely small, is it possible for the rocket to keep going and land somewhere on land, without boosting backwards?

  7. I know how they can fit 2 rockets on a drone ship. Also reload it an launch from a drone or back to land and to the location… Tell SpaceX to contact me at 2542452484 text first then call I work a lot….

  8. i figured out the solution elon musk just needs to find a non self serve gas station in space so his giraffestronaughts can come back to earth on the first stage

  9. I didn't consider the extra weight factor. Shucks. I thought that some extra speed was required on some missions and that was why more fuel was used inserting the payload into the orbital trajectory it needed. I wish I'd found your videos sooner.

  10. i like the analogies, wish you'd have shown the maps and routes side by side though. also – ya'll must have different tow trucks than we got out here…
    edit- commented before the end.. nailed it with the rocket graphics

  11. I love your videos, but I really don't understand why do you keep using gallons, miles, etc, instead of the International system of units. I'm from spain and it's anoying to be converting the untis, because an underused and obsolete system. Sorry If It seemd rude, that was not my intention its simply it's weird for me the use of this system in a cientific youtube channel, and because the english for me I'm not really confident with it, and I don't know if some things can be bad interpretations.

  12. Wish this wasn't explained like I was 5. Could also have been done way easier and way faster. Wonder how the BFR will launch possibly some of its biggest payloads and also get its first stage back to the launch pad.

  13. Where do I find all the orbital mechanics math that was "too complicated for everyday astronauts"? It sounded so interesting and I kind of could hear some clues that I'm familiar with.

  14. I love your channel and the work you do but the whole giraffes in the car was too convoluted, the simple animation of the rockets just after explained the whole thing so much better, but then it would have been a shorter and less humorous video.

  15. Way….WAYYYYY too complex. Great premise but you lost A LOT of people half way through that. Just say that the rocket doesn't have enough fuel to make it back to LZ1 or LZ2. It's a "booster" which means it boosts the load as far as is safe or feasible. SpaceX puts a gas tank in with a bit more gas than they use, the booster must land in Beverly Hills because they can't make the tank any larger so it drops on a drone ship with this reduced load of gas available.

    HUZZA!

  16. Hey everyday astronaut i know the space suit almost killed you but can you do a little *space walk* under water or explain why you dont do it with that suit

  17. Any way I can get some facts about the Dragon crew capsule? I was wondering if they are still using the Draco's for emergencies during launch? Also if they are can they use the Draco's to do an emergency landing if the chutes fail? Also how many variations are there of the crew capsule if more than one?
    Oh and Ty for the video btw lol
    Cheers from canada

  18. I knew why they land on the droneship or on land or not recover at all, somehow I’m more confused because of the girrafestronaut explanation… XD

  19. This is a hilarious comparison. Well done! You should definitely add littlte Giraffestronaut pets to your shop.
    Btw. still miss your old intro…

  20. I loved the explanation in this video. I was sceptical about watching it since I knew the answer to the question you posed but your delivery is great. We need more people like you getting others excited for science and engineering. Great work

  21. Why does the video "footage" of the landings look like a cross between crappy CGI and claymation photography from an early 60s kiddie program?

  22. I came into this video thinking that this is a dumb question and the answer is obvious, but I came out way smarter and kind of enlightened. Thank you for these great videos!

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