In this lecture, I would like to do an introduction
to rockets. I’ll be focusing more on the
rockets that took people to the Moon.
Let’s start with a brief history of rockets.
The earliest know use of rockets is in China,
perhaps beginning even earlier than the 13th
century. Rockets were first developed in the
Song dynasty, which was around between the
year 960 to 1279. On the right is a picture
of “Long Serpent” rockets, which were
arrows with rockets mounted on their sides.
As such, the first documented use of rockets
is in warfare.
Continuing this trend of rockets being used
for battle, in India Mysorean rockets were
used against British forces in 1780 as depicted
on the left. Mysorean rockets were taken to
the United Kingdom where they were developed
as Congreve rockets. Those Congreve rockets
were later used in the War of 1812 by the
British against the United States. Having
witnessed the use of those rockets at Fort
McHenry in Baltimore, Francis Scott Key wrote
“and the rockets’ red glare” into the
American anthem (the Star-Spangled Banner).
Next, I would like to talk about Konstantin
Tsiolkovsky who was a Russian/Soviet high
school math teacher. He pioneered much of
the theory of rocketry. He’s particularly
known for the Rocket Equation, which is shown
on the right. This equation is fundamental
to rocketry and helps designers calculate
the propellant required for a rocket of a
given mass and for a given Delta V or change
of velocity required. In the way that the
equation is written above, the change in velocity
that a rocket experiences (Delta V) depends
on Ve, which is the velocity of the rocket
exhaust and the natural log of the ratio of
the initial mass (mi) to the final mass (mf).
The difference between the initial mass and
the final mass is the mass of the propellant.
I’d like to also note that there’s a crater
on the farside of the Moon called Tsiolkovsky
crater in his honor. The crater is shown on
the right. You’ll notice that the crater
is filled with dark basaltic lava.
Next, I’d like to talk about Robert Goddard
who was a pioneer in rocketry in his own right.
He also has a connection to high school education
as noted in the quotation, which I will return
to in a moment. Robert Goddard had numerous
contributions to rocketry. One of his prominent
contributions was the development of the first
liquid-fueled rocket in 1926. He also has
a connection to Baltimore, Maryland since
he died here in 1945.
Robert Goddard was heavily criticized when
he was alive. On the left is a newspaper clipping
from the front page of the New York Times
on January 12th, 1920. The article read, “Believes
Rocket Can Reach Moon, Smithsonian Institution
Tells of Prof. Goddard’s Invention to Explore
Upper Air.” The next day there was an editorial
in the New York Times stating, “That Professor
Goddard, with his [quote] chair in Clark College
and the countenancing of the Smithsonian Institution
does not know the relation of action to reaction,
and of the need to have something better than
a vacuum against which to react-to say that
would be absurd. Of course he only seems to
lack the knowledge ladled out daily in high
schools.”
On July 17th, 1969, only days before Neil
Armstrong stepped foot on the Moon, the New
York Times issued a correction. Toward the
end of the correction it stated, “Further
investigation and experimentation have confirmed
the findings of Isaac Newton in the 17th Century
and it is now definitely established that
a rocket can function in a vacuum as well
as in an atmosphere. The Times regrets the
error.” The correction was 24 years too
late since Robbert Goddard died in 1945.
We have to talk about Wernher von Braun. He
developed the V-2 rocket for Nazi Germany.
A schematic of the V-2 rocket is shown in
the middle. The V-2 is the world's first long-range
guided ballistic missile. They were built
by slave laborers from concentration camps.
In production of this rocket, 12,000 to 20,000
people were killed. These rockets were aimed
at mostly London, where 9,000 people died
in the attacks of this rocket. After surrendering
to the Americans after World War II, von Braun
came to the United States. The rocketry work
in the United States culminated in the development
of the Saturn V rocket, shown on the right.
Some of you may have read the comic series
The Adventures of Tintin. There are two books
in the series about traveling to the Moon.
One, shown on the right, is Explorers on the
Moon. When Hergé wanted to have a rocket
in this story, he look to the V-2 rocket for
inspiration since that was what a rocket was
at the time. I just want to take a moment
to point out how choices we make with the
technologies that we have have consequences
in influencing and informing future generations
of what is possible. It is our responsibility
to use our technologies for good.
As we have seen, the early history of rockets
is mostly comprised of them being used for
warfare. It turns out that rockets can be
used for purposes other than warfare! Shown
here are the five rockets of the early U.S.
human space program. The rockets are ordered
according to the numbers shown above. First
is the Redstone rocket, which was used for
the first two Mercury missions of Alan Shepard
and Gus Grissom. The Redstone rocket was not
very powerful, so both of those flights were
suborbital, meaning that they didn’t go
into orbit around the Earth. They went up
to space, but then came back down while following
a parabolic path. The Mercury program then
moved on to the Atlas rocket. The Atlas, being
more powerful, allowed astronauts to go into
orbit for the rest of the Mercury missions,
starting with John Glenn’s Mercury 6 mission.
After Project Mercury, NASA moved to the Gemini
missions. Each Gemini mission had two astronauts
instead of the one onboard Mercury spacecraft.
All Gemini missions launched from the Titan
rocket. For Project Apollo, two types of Saturn
rockets were used. One was called the Saturn
IB, which was used for the Earth orbital Apollo
7 mission and the other was the much more
powerful Saturn V rocket. The Saturn V was
used for Apollo 8 through Apollo 17.
Let’s look at the two Saturn rockets used
for Apollo missions in a bit more detail.
Let’s consider the name “Saturn.” You
may wonder why the rocket is called Saturn.
The rocket is named after the planet Saturn.
The U.S. rocket program had a series of rockets
called Jupiter. Jupiter C is shown on the
left. When they were developing more powerful
rockets, they wanted to move onto a different
name. They used Saturn since it’s the planet
after Jupiter.
Here’s a list of all Apollo rocket launches
divided by the two Saturn rockets that were
used. Note that there were three uncrewed
and unnamed Saturn IB launches, followed by
the uncrewed Apollo 5. Apollo 5 used the Saturn
IB that was attached to the Apollo 1 spacecraft.
That is the mission where Gus Grissom, Ed
White & Roger Chaffee died in the fire. Apollo
7 was the only Apollo mission to launch into
space using a Saturn IB rocket. There were
two uncrewed Saturn V launches prior to Apollo
8. Apollo 8 and onward, all Apollo missions
were launched using Saturn V rockets.
This is footage I filmed on July 20th, 2019
on the 50th anniversary of the Apollo 11 Moon
landing at Kennedy Space Center in Florida.
This video should help you get a sense of
scale of the Saturn IB rocket.
Let’s take a look at a schematic of the
Saturn IB, so that we understand its major
components. The Saturn IB had two stages and
the spacecraft sat above the second stage.
Let’s consider each stage individually.
The first stage of the Saturn IB had 8 engines.
The stage used Rocket Propellant-1 (or RP-1)
as fuel. It’s a form of kerosene. For oxidizer,
it used liquid oxygen. Rocket stages primarily
consist of tanks and engines but there are
other important components such as baffles
to stop the liquids from sloshing.
The second stage of the Saturn IB had one
engine. While the oxidizer was again liquid
oxygen, the fuel was liquid hydrogen instead
of Rocket Propellant-1. Note that the Saturn
IB’s second stage was also the third stage
of the Saturn V rocket. If you listen to or
read Apollo mission audio or transcripts,
they’ll often say “S-IVB,” by which
they are referring to this stage.
Let’s take a look at the Saturn V rocket.
Please take a moment to take in the gigantic
size of this rocket.
The first stage of the Saturn V has 5 very
large F-1 engines. Those engines are to this
day still the most powerful rocket engines
ever made.
Large rockets are generally unstable. Try
balancing the tip of a pen or pencil on one
finger and you’ll get the basic idea. To
make sure that large rockets are going in
the correct direction, their engines are gimbaled.
The 4 outer engines of the Saturn V were gimbaled
giving the rocket the ability to steer itself.
The Apollo spacecraft sat at the top of the
Saturn V rocket. The cone shaped part of the
Apollo spacecraft, called the Command Module,
was where astronaut were during most of the
mission. When they were going to land on the
Moon, two astronauts moved into the Lunar
Module (or LEM) from the tunnel where people
are peering inside in this video. At the back
of the Apollo spacecraft is the engine that
was used to get into and out of orbit around
the Moon. This engine used a hypergolic fuel
and oxidizer, which means that the fuel and
oxidizer ignited upon contact without the
need for a spark or ignition source. This
was a safety feature since there was only
one engine on the Apollo spacecraft and it
was critical. Particularly when leaving the
Moon’s orbit, if this engine didn’t work
then the astronauts wouldn’t have had any
way of getting back home. The fuel used was
a 50-50 combination of two types of hydrazine
and the oxidizer was nitrogen tetroxide. The
middle cylindrical portion of the Apollo spacecraft
is the Service Module and, as the name suggests,
it housed propellants, fuel cells, and various
support systems for the Command Module. You’ll
also notice there are small thrusters on the
sides of the Service Module and those were
used to change the Apollo spacecraft’s pointing.
This is how the three astronauts were seated
during launch inside the Command Module. The
mission Commander was seated in the left seat
followed by the Command Module Pilot and the
Lunar Module Pilot. Shown here are three dummies
but they help you get the idea of the small
space astronauts had to work with during missions.
While the Apollo spacecraft stayed in orbit
around the Moon, the spacecraft that landed
on the Moon was the Lunar Module (or LEM).
It had two parts. The upper part was where
the two astronauts were and was the portion
of the LEM that was used to leave the surface
of the Moon and meet back up with the Apollo
spacecraft. The bottom part of the LEM, primarily
consisted of the propulsion system used to
land on the Moon.
This is the Apollo 14 Command Module. As you
probably can tell, it has seen better days.
Its current condition is largely due to the
intense temperatures of coming back at a very
high speed through the Earth’s atmosphere.
This is a schematic of the Saturn V rocket
showing its main components. It had three
stages compared to the two stages of the Saturn
IB rocket. The extra trust via the third stage
was necessary to get the Apollo spacecraft
to the Moon. Let’s look at the stages individually.
Like the Saturn IB’s first stage, the first
stage of the Saturn V used a combination of
Rocket Propellant-1 (or RP-1) and liquid oxygen.
It had five F-1 engines. The first stage took
the astronauts to about 68 km (42 miles) above
sea level before it ran out of propellant
and was jettisoned.
The second stage of the Saturn V used a combination
of liquid hydrogen and liquid oxygen as propellant
and had 5 J-2 engines. It carried the astronauts
to about 175 km (109 miles) above sea level
before it ran out of propellant and was jettisoned.
Like the second stage, the third stage of
the Saturn V also used a combination of liquid
hydrogen and liquid oxygen as propellant.
It had one J-2 engine. You may recall that
this stage was also the second stage of the
Saturn IB rocket. This rocket put the Apollo
spacecraft first into Earth orbit and then
was shutoff, while the Apollo spacecraft orbited
the Earth and final checks were made before
TLI (Trans-Lunar Injection). At the time of
TLI, this stage reignited giving the Apollo
spacecraft sufficient energy to break away
from Earth’s gravitational pull and head
towards the Moon. After its use, this stage
was either directed into an orbit around the
Sun or was purposely crashed onto the Moon
to study the interior of the Moon using seismology.
We should not ignore a very important interstage
ring that sat above the third stage. This
Instrument Unit was the computer brain of
the Saturn V and did the necessary calculations
to guide the rocket.
I found this model of the Saturn V at Kennedy
Space Center very cool! The side panels of
this model are transparent, so we can take
a look at what is going on inside the rocket.
This clip will end at the bottom of the second
stage. Notice how much of the rocket is taken
up by tanks for fuel and oxidizer.
This clip continues from the bottom of the
second stage onward.
Let’s take a look at rocket propulsion in
a bit more detail. Rockets are essentially
creating fire and using that heat energy to
propel themselves forward. Generally, the
three components for a fire are an oxidizer
(like oxygen), a fuel (like liquid hydrogen)
and a spark. Rockets typically need all three
components to work.
You are probably more familiar with other
types of engines that do something similar
in the sense that they also use an oxidizer,
a fuel, and an ignition source to produce
heat energy and then use that energy to propel
a vehicle like a car or an airplane. On the
left is a car engine where it takes in a mixture
of fuel (typically gasoline, also known as
petrol) and an oxidizer (oxygen from the air)
compresses that mixture and ignites it with
a spark plug. The resulting burst of energy
pushes the piston down, which creates rotational
motion that makes the wheels of the car rotate.
A jet engine, in this case a particular type
of jet engine used on commercial airplanes
called the turbofan engine, does something
similar. The turbofan engine takes in oxygen
from the air, compresses it, combines that
with fuel, and ignites the mixture. This produces
energy that is used to push the engine and
in turn the airplane itself forward.
Unlike car engines and jet engines, rockets
don’t take their oxidizer from the air.
Part of the reason is that large rockets are
typically out of the Earth’s atmosphere
in a matter of minutes and the other reason
is that given the large quantity of fuel that
rockets consume in a short period of time,
it would be difficult to get the necessary
oxygen from the atmosphere quickly. As such,
rockets carry all three component (fuel, oxidizer,
and an ignition source) with them. Broadly
speaking there are two types of rockets. Historically,
the older of the two is the solid-fueled rocket.
As we saw in the beginning of this lecture,
these are the types of rockets that were developed
early on in China and are used today at fireworks
shows. The solid-fueled rocket was the only
type of rocket till 1926 when liquid-fueled
rockets were developed by Robert Goddard.
As the name implies, in solid-fueled rockets
the propellant is a solid. It’s often a
plastic-like material that has a combination
of fuel and oxidizer. That means they just
need to be ignited and they start going. One
downside, is that they are generally hard
to stop once they get going. They don’t
have the ability to stop and restart, as was
required by the Saturn V’s third stage.
On the other hand, liquid-fueled rockets can
be restarted and they were the primary means
of propulsion for the Apollo program. While
liquid-fueled rockets are complicated due
to a number of reasons including the multiple
tanks, pipes, and pumps, they are very powerful.
Before we end today, let’s look at the various
steps in the Apollo flight path. This image
is not easy to see, so I encourage you to
use the link below to download the image for
yourselves. Let’s take a look at the four
main steps individually.
The first step is to get into Earth orbit.
You will see a depiction of the Saturn V’s
first stage burning and being jettisoned into
the ocean. Next the second stage is used and
discarded into the ocean. The third stage
burns for a short time to give the spacecraft
sufficient velocity to go into Earth orbit.
After final checks, the third stage reignites
giving the spacecraft sufficient velocity
to escape Earth’s gravitational pull. On
the way to the Moon, the Apollo spacecraft
comes off the third stage and turns around
180 degrees. This is done to align the top
of the Apollo spacecraft with the Lunar Module,
which was sitting below the Apollo spacecraft
during launch. The Apollo spacecraft docks
with the Lunar Module and extracts it. As
I mentioned, for some of the Apollo missions,
the third stage (or S-IVB) was directed into
an orbit around the Sun and for other missions
this stage was purposely crashed onto the
Moon.
Once the Apollo spacecraft got close to the
Moon, the Apollo spacecraft’s engine was
fired to slow down and get captured into orbit
around the Moon. After sometime, two astronauts
got into the Lunar Module and detached from
the Apollo spacecraft. While the Apollo spacecraft
stayed in lunar orbit, the Lunar Module landed
on the surface.
After surface operations were completed, the
two astronauts on the Moon flew back to the
Apollo spacecraft using the upper portion
of the Lunar Module. That portion of the Lunar
Module was jettisoned once the two astronauts
were back inside the Apollo spacecraft. The
Apollo spacecraft’s engine was then fired
to break away from the Moon’s gravitational
pull and to head back home.
When close to the Earth, the bottom portion
of the Apollo spacecraft, the Service Module,
was jettisoned. The Command Module then came
through the atmosphere and landed in the ocean
where the astronauts were picked up by ship.
