I get asked a few
similar questions often, and they're truly fantastic questions. They all start with
something along the lines of "why don't they just," and then they're followed with
what seems like a great idea, such as "why don't they just
launch rockets from on top of mountains" so they're closer to space and they won't have as
much air to fight against, and they could even use more
vacuum efficient engines. I mean, think about how much
fuel is wasted just to get up to say four kilometers in altitude. How much smaller and more
efficient could rockets be if they could start off much
higher above sea level, above most of the atmosphere? Or another great one is why
don't they just launch rockets from the equator so the rocket
gets to take full advantage of the earth's rotation
to help it get to orbit? Why aren't we taking full advantage of the planet we're living on? I mean, it's free energy, right? How much of a difference
does launching rockets from different locations actually have? I'm Tim Dodd, the Everyday Astronaut, and today we're going
to dive into the physics of launching rockets from
different places around the earth. We'll go over the pros and the cons of launching from mountaintops or closer to the equator in great depth to see if we can figure out why exactly we just really don't see
rockets launching from these locations all that often, if at all. Here's the timestamps for these sections, which are also in the description here. The YouTube timeline is
broken up into these sections, and of course we have an article version of this video up at everydayastronaut.com for your reading pleasure. And while you're there, take
a look at our awesome shop where you can find incredibly
detailed 1:100 scale metal Falcon 9 model rockets, and lots of other really cool stuff@everydayastronaut.com slash shop. Okay, let's get started. 3, 2, 1. [Intro Music] Right at the
top here, I have to strongly, strongly suggest watching my
video orbit versus suborbital because it lays down a lot
of important groundwork that are vital concepts for this video. But if you already are familiar
with orbit versus sub orbit where it is space start and the Karmán line apogee
versus perigee, zero G and weightlessness, et cetera, et cetera, then I think you're probably
ready for this video. And quick little fun note,
this is part one of two. In the next video we're going to talk about why don't they
just use other technologies alongside rocket engines to help make launches more
efficient, like using jet engines or air launching, or even
build massive catapults or maglevs and things like
that to help throw rockets. So be sure and stay tuned. So that being said, let's start
off with a great question. "Why don't they just launch
rockets from on top of mountains?" Launching from a mountain? I mean, this one seems pretty obvious. Not only are you closer to space, the atmosphere is also much thinner on top of tall mountains. So you can actually
utilize a more efficient, more vacuum optimized nozzle and you'll actually have less air to fight against on
ascent by using a longer, larger nozzle. We gain efficiency from the
engine since the nozzle's job really is just to convert
high pressure, hot, slow moving exhaust gas
into lower pressure, lower temperature, faster,
moving exhaust gas, which directly correlates to
the engine's efficiency. But there is a limit to how big you can make a
nozzle in the atmosphere. A larger nozzle can lower
the pressure of the exhaust below ambient air pressure,
especially at sea level where ambient air pressure
is at the thickest, and that can cause flow
separation at the nozzle exit that can actually damage the engine. The difference between a sea level engine and a vacuum optimized engine
is really obvious on the 3.7 meter wide Falcon 9 because you can fit 9 sea level
engines on the first stage, but you can only fit one
vacuum optimized Merlin engine on the upper stage. So same engine, different nozzles. It shows you how big a
difference that really is. Now the general rule of thumb
is you can't have your nozzle exit exhaust be below about 40% that of the ambient air around it. So at sea level with one bar of pressure, the exhaust is rarely much
below 0.4 bar at the exit of the nozzle to prevent flow separation. Okay, now that we have that out of the way and we understand the
difference between a sea level and vacuum optimized engine, let's make up a little
situation where we might want to launch a rocket from
on top of a mountain. Let's pretend we're ULA
or United Launch Alliance. We're from the United States and we've got our headquarters in Colorado pretty close to Denver. One day we decided, you know, we've got the beautiful Rocky Mountains right in our backyard. So why don't we just
choose a new launch site for the Delta four medium
with no solid rocket boosters. Now yes, I know that that
rocket's retired, so bear with me. It's we're using it for
a very particular reason. You'll see why here shortly. We decided we want to put
a new launchpad up on top of Pike's Peak because it's
pretty close to our workforce. It has a paved road
all the way to the top, and it's really quite
tall at 4,302 meters. And believe it or not, here, the atmosphere is
already about 40% thinner than it is at sea level. This means we could increase
our nozzle size on our first stage, which could offer a
few percent better efficiency. Our new slightly larger
nozzle can get 380 seconds of specific impulse at the launch site and 420 seconds in a vacuum
versus the 360 seconds and the 412 seconds, the standard RS-68 a engine
would normally achieve. And here's the fun part. This
theoretically could have been possible on the Delta four
medium, which is why we chose it, because it only had a single
engine with nothing else to really run into, no other engines next to it or anything like that. So the nozzle could
have theoretically grown for these special
mountain launch versions. Now, the big question is
though, what did it do? What's the actual performance
gain of doing this? If the delta form medium with no solid rocket boosters
launched from Kennedy Space Center, it could lift about 8.5 tonnes. So how would a delta form
medium with this new, you know, mountain launch version actually perform? Well, it's payload capacity
could go up about a thousand kilograms to almost 9.5 tonnes. That's actually quite a
healthy increase in capacity. But believe it or not,
there's actually very, very little advantage in launching
from a higher altitude in terms of it being closer to space. That modest gain of four
kilometers compared to the hundreds of kilometers of altitude that the rocket will end up
in just really isn't a lot in terms of percentage of the final altitude. Another thing that doesn't
make a big dent is the velocity gained from launching
from a higher altitude. Since the velocity at the
ground is roughly the same regardless of where you
launch from either sea level or on top of a mountain. As those of you who watch
my video on orbit versus sub orbit, know, even if you started
in space, you'd still need to gain roughly 7,900 meters
per second of velocity in order to actually get into orbit
and therefore stay in space. So we see virtually all of these gains from the
more efficient nozzle that we could utilize, which
gives us additional delta V or change of velocity from
the same amount of propellant because the nozzle's more efficient. So there's that, and
then plus it's, you know, there's less air to fight against, but we really don't see any
advantage from the actual starting altitudes distance to space, which is frankly negligible. But regardless, a one ton increase or what is that, that's
more than a 10% increase. Sounds pretty amazing. You know, rocket scientists
will go to some extreme measures for just a few percentage gain. So what's the holdup? Why don't we see rockets
launching from Pikes Peak? Well, there's a couple
things at play here, but perhaps the biggest
showstopper is the location of this pad being inland
where the rocket would have to overly populated areas
and personal property. This is generally a big no-no, at least here in the United States. The FAA does not love when a
highly explosive rocket flies overpopulated areas, especially because even in normal, nominal operations or norminal operations, a traditional rocket booster
is simply dropped off and expended and it'll actually
come crashing down just a few hundred kilometers down range. Now, theoretically, you know,
something like a Falcon 9 could just return to the launch site, but you're still having to
fly overpopulated areas. So if something went wrong and they had to terminate the rocket, yeah,
you're gonna have big chunks of rocket debris falling down
in, you know, in the middle of Colorado Springs or something. And I just don't think that's a good idea. Now, having a rocket or
potentially having rocket parts falling from the sky isn't
really a big deal when you're launching over the ocean, where the spent booster can
just simply crash into the ocean far away from any human population. And just to make sure there
aren't any humans at risk of a booster crashing on their heads, the path is actually
cleared of boats and planes before every single launch. That's right, they actually
publish an exclusion zone downrange of where the
rocket's going to fly, and they have to clear out
to make sure there's no boats or planes before every single launch, and they, you know, they
publish it ahead of time so you know, captains and pilots know not to go into this area, but occasionally, you know,
someone didn't check it right or ended up in the wrong
place at the wrong time. And there'll be a wayward boat or a plane that comes
right down into the range before the rocket's about to take off. And you know, it'll end up
totally scrubbing the rocket. They'll have to like shut it all down, and it's just one of the most frustrating and worst reasons for a scrub - Hold, hold, hold
aborting to launch auto. Launch director calling a hold. We have a red range for a fouled range with a ship in the hazard area. Now, it simply wouldn't be
possible to clear out an area for hundreds of kilometers
down range when launching inland from the United States. Now, unfortunately, for
some people living in remote villages in China, Russia, and Kazakhstan, they don't have the luxury of living in an area
where a giant metal tube might not crash on them. Anytime a rocket launches. Another major complication
is simply the logistics of getting both the rocket,
but also the propellant and all the other stuff up the top of the mountain for each launch. And this isn't trivial, the road going up Pike's
Peak is very windy with extremely tight turns and often hazardous weather conditions. So yeah, some of these conditions
might actually be outside of the operational range of
both the rocket and the crew. So in this particular example, unless the factory was
basically right next to the launchpad, shipping
a five meter wide delta four across the country by highway and then up a windy treacherous
road up a mountain just really doesn't make sense. Shipping costs and logistics
is why SpaceX designed the Falcon 9 to be the size that it is. Falcon 9 is exactly 12 feet wide or 3.65 meters wide, which
is the maximum width. You can ship something on US
highways without getting into the super load category
of oversized loads. But of course, the real reason
why we don't see rockets launching on top of mountains is because it costs more money,
potentially a lot more money. In a case like this, if there
happened to be a payload that was more than 8.5 tons and we're ULA, and we're sitting there going,
"uh oh, our Delta four medium can't do more than 8.5 tons". Instead of losing a customer, we could probably just upgrade them to a Delta four medium plus
with two solid rocket boosters. Which yes, that was a thing you can do. You could add two or four smaller solid
rocket boosters to the side of the rocket, and at
just $5 million a piece or $10 million for the pair, you could increase the payload
capacity to 12 metric tons. So a full 3,500 kilogram increase. So for the very few times
where that one extra ton of payload capacity might
find you a new customer, it'd simply not be worth
the investment, the risk, and the increased cost of operations when instead you
could just simply attach two solid rocket boosters to your rocket that would fit the needs of the customer. But here's something interesting. In our example, we
actually lost a little bit of potential performance increase because of our launch location. No, I'm not talking about the altitude, I'm talking about the latitude. Pikes Peak is at 38.8 degrees north, so it's a good 10 degrees further
north than Cape Canaveral. This means it's even further
away from the equator. So the Earth's rotation doesn't
offer as much of a boost as it would at lower latitudes. Okay, so this brings up a good point. "Why don't they just launch
rockets from the equator to take full advantage
of the Earth's rotation?" The Earth is spinning quite quickly, in fact. At the equator, the earth surface is moving at
about 460 meters per second, which is a fairly large chunk of the 7,900 meters per second needed to actually orbit the earth. That's about 6% of orbital velocity. I mean, this seems like
a no-brainer free energy. And thanks to the relationship
between your total delta V and your payload capacity,
460 meters per second of free velocity can actually drastically increase your payload
capacity much beyond 6%. Well, it's obviously a pretty good idea, and that's actually exactly
why the European Space Agency has been doing this since 1968. The French Guiana Space
Center is a European spaceport located in South America
in the French territory of French Guiana. It's very close to the equator, only about five degrees north of it. This allows rockets launching from there to take nearly full advantage
of the Earth's rotation, and it offers a quite noticeable increase in payload capacity. But how much of an increase
are we talking about here? Well, we can actually see
the exact amount since nearly identical Soyuz 2.1 rockets
launched from both the GUiana Space Center, at that five
degree north latitude and Baikonur Cosmodrome, which is located
at about 46 degrees north. When launching from French Guiana, the Soyuz ST can take
about 3,200 kilograms to a geostationary transfer
orbit when the nearly identical Soyuz 2.1 A launches from Baikonur it's limited to only
about 2000 kilograms to that same geostationary transfer orbit. That's 60% more payload capacity just by changing the launch site. And ESA isn't the only ones who were eyeing some free velocity from the Earth's rotation. A company called Sea Launch
had a floating launch platform that, as the name implies, would
launch rockets from the sea right on the equator. The rocket that launched from
this sea platform called Ocean Odyssey was a Zenit 3SL. So a variant of the Zenit
rocket featuring one of my all-time favorite rocket engines, the RD-171, which is the most powerful
liquid fueled rocket engine ever made. The rocket and the
platform sailed 11 days, a pretty incredible 4,800
kilometer journey from Long Beach, California to the equator at
154 degrees west longitude in international waters. From here, the ZENIT 3SL
could take 6,160 kilograms to geostationary transfer
orbit, which again, was a very healthy increase in
capacity from its derivative, the ZENIT 3SLB, which could only take 3,750 kilograms to GTO from its launch
site in the Baikonur Cosmodrome in Kazakhstan. So again, it's about a
60% increase in capacity. Sea Launch would fly the
Zenit 3SL 38 times with the last launch in
2014, they would end up with an okay track record having lost four of those 38 missions. Unfortunately, they closed up shop in 2014 as their services were largely considered unreliable and expensive. But wait, they were able to launch 60% more payload using pretty much the exact same rocket. Why did they fail? Or for that matter, why doesn't every launch
provider just ship their rockets to lower latitudes to get increased performance
out of their rockets? Well, if we're now having
to ship our rocket, and in the case of sea launch our rocket and our entire launch pad
down to the equator, of course that's going to cost money, and this cost won't be
insignificant, likely in the millions of dollars in fuel, fleet, and personnel just to ship it there. Now, pretty much all launchpads
have some considerable distances between the launch
teams and headquarters, but the more remote it is, the more of a logistics issue it
becomes to move teams around for every single launch campaign. But not only do these logistics
apply to the personnel, it also applies to payloads
and replacement parts and fuel and all that sort of stuff. So now you also have to fly and ship every single thing
to these remote locations. Every single time there's
a problem or a new part or something that needs
to be replaced or added. I mean, imagine if there's
a problem with the rocket and you actually had to send
it back to the factory. That's gonna cost you,
that's gonna cost you a lot. Now, if you're a company like ULA, again, as a perfect example, who's
already shipping their rocket by barge, getting a rocket
from Huntsville, Alabama to Cape Canaveral is already
a 3,400 kilometer journey, or all the way down around the, the Panama Canal to California. So you could theoretically imagine a world where it could be more advantageous or frankly, more of an option
for ULA to ship a rocket via, you know, the ocean to
a launch complex closer to the equator compared
to, again, let's say SpaceX and their highway shippable Falcon 9. But the reality is flying closer to the equator probably
makes the biggest difference. If your other option is
landlocked to the East, such as everywhere in Europe, and or if your current launch
pads are very far north, like those pads in Russia and Kazakhstan here in the United States, our primary launch pads are
already fairly far south, at least compared to, you know, those in Russia and Kazakhstan. You know, the majority of our
launches take place at Kennedy Space Center, and that's
already at 28.5 degrees north, so that's decent. And then there's Wallops Virginia, which is a little bit
less frequently used. It's almost 38 degrees north, and then SpaceX's Starbase
is at 26 degrees north. And this extra inertia from
the Earth's rotation is mostly advantageous when you are
launching into high energy orbits like geostationary orbits or the rare equatorial orbit, which can technically only
really be reached either from the equator or by doing an energy
intense dog leg maneuver. Now, if you're launching
into a polar orbit or a sun synchronous orbit or a retrograde orbit, launching closer to the equator is
actually not an advantage because you actually
have to fly retrograde to cancel out the rotation of the earth. So in these cases, it's
actually advantageous to fly closer to the poles. So ironically, having a launchpad
down at the equator could actually be a negative
thing for certain missions. And that, my friends, is
the art of compromise. And frankly, the location of launchpads often is
primarily a matter of what land is actually
just available, period. It's not always feasible to place a launchpad at the
exact perfect location maximized for performance because it's
got the highest altitude and the lowest latitude
and blah, blah, blah. Sometimes it just simply comes down to simple land acquisition considerations. Oftentimes, launch complexes
are on military bases or federal land. I mean, sure, there's a handful of private launch pads popping up now, especially in the last decade or two, but you often are limited
to what's available or you know, being offered to you, your company or your organization. But there's pros and
cons to all this stuff. There's always pros and cons. So to summarize, rockets
are incredible feats of engineering, and they're
already pretty close to the edge of what's physically possible. So it only makes sense that
we, you know, all kind of crave to try and find ways to help
squeeze even more performance out of them, optimizing them
as much as physically possible. But the problem all comes
down to a couple simple words, practicality and compromises. Yes, on paper, pretty much everything we
talked about in this video would indeed help a rocket do more work and potentially increase its performance dramatically at the end of the day. There's always some deep trade that each engineering team goes through when designing a system. If option A is projected to
cost, let's say, $1 billion before you can start flying
a customer's payload, and option B is projected
to cost $2 billion, that's a gamble that you simply
might not be able to take due to your available resources. Whenever I think of a
question like this myself where there's something along the lines of "why don't they just," I
first usually tend to just kind of default to why does
every team of engineers seem to wind up doing such similar things and coming to similar solutions so often, But honestly, in the future,
who knows, if Rocket launching to, you know, the Moon and Mars
and all these huge missions, and we're launching a thousand
times more than we are right now, these things might help. You know, 60% payload capacity
might make a ton of sense. I mean, and don't forget,
SpaceX was looking at, you know, launching on sea launch platforms
that could potentially be, you know, down near the equator. So you never know,
maybe in the future some of this stuff will be utilized, but for now it's not so much. But what would you do if you
were building a launch vehicle and a launch complex? Would you try and find a
mountain near the equator next to the ocean, or would you
just take whatever's easily accessible, available, and affordable? Let me know your thoughts
and if you have any other questions about the stuff
in the comments below. And don't forget, this was only part one of a two part video series, and in part two, we're going
to dive into air launching or putting jet engines on rockets or giving them a boost from the ground with a slingshot or a maglev. This whole, "why don't they
just" thing keeps getting more exciting and more ridiculous. So be sure and stay tuned for part two. I owe a huge thank you to
our Patreon supporters, our YouTube members, and
our Twitter subscribers. We offer some fun little
perks like, you know, script read throughs and
exclusive live streams. Or you can get your name here
if you're a Patreon supporter at the Mission Director tier. But all these things just
really go a long way. Or if you feel like it, drop
a "super thanks" here on YouTube or give this video a thumbs up and share it with a friend. It all helps. And of course,
while you're online, head over to everydayastronaut.com/shop
for things like this, our Aerospike shirt or incredible Falcon
9 metal model rockets. I always say metal, but
you need to like, it's not until you hear 'em and feel
'em and feel how heavy and and detailed these things are in person that you realize just
how amazing they are. We have lots of other cool
stuff, including our dress wear, schematics, collection,
future martian shirts, fun accessories like our heat
shield color changing mug, and tons of other cool stuff and more stuff is coming along the way. Head on over to
everydayastronaut.com/shop. Thanks everybody. That's
gonna do it for me. I'm Tim Dodd, the Everyday
Astronaut, bringing space down to earth for everyday people.
