April 1961,
the Soviets put the first man in space.
Just weeks later, the Americans
announced they would be one-upping them
by sending a man to the moon.
>> I believe that this nation should commit
itself
to achieving the goal
before this decade is out of landing a
man on the moon and returning him safely
to the earth.
>> It was a bold assertion, particularly as
by this time the US had only ever sent
one person into space.
To get to the moon, they needed to
improve their deep space technology and
fast. And so, Project Gemini was born.
Gemini was the key stepping stone to
building the technology that would keep
men in space long enough to get to the
moon. A stepping stone most of us have
all but forgotten.
This pioneering project was designed to
bridge the giant gap between Mercury and
Apollo, and it repeatedly [music]
pushed brave crews to the very edge of
survival with astronauts nearly boiling
alive, riding nuclear warheads into
space, and being rescued by some of the
earliest cosmic computers.
I'm Alex Mccolgan and you're watching
Astrum Extra. Join me today as we
explore the science and technology of
Project Gemini. Discover its biggest
wins and nearest misses, and reveal how
these vital missions paved the way for
Apollo 11 landing on the moon.
On the 12th of April 1961, the US lost
the race to put the first man into space
when Yuri Gagarin, a Soviet cosmonaut,
successfully orbited the earth.
Determined not to fall behind again,
President John F. Kennedy committed the
United States to landing a man on the
moon as quickly as they could.
>> We choose to go to the moon in this
decade and do the other things, not
because they are easy, but because they
are hard.
>> But the United States Mercury program
had only just cracked how to get a man
into space, specifically one man in
fact, Alan Shepard, whose mission had
only lasted for just over 15 minutes.
This was a far cry from conquering space
travel. If they wanted to get [music] to
the moon, they needed to make progress
and fast. And that's when Project Gemini
was born.
Its aims were set out from the beginning
as a project to master long duration
space flight, perfect orbital rendezvous
and docking, to test space walks, and
refine re-entry [music] and landing. But
before all that, first they needed to
get into space. So, let's start with how
they actually planned to get up there.
The Mercury and Gemini rockets had
[music] some similarities. Both were
originally missiles repurposed for
spaceflight. Perhaps not the most
comforting thought, but their structural
differences meant there were new
problems for the Gemini mission to
solve.
The Mercury Atlas rocket was based on
the US Air Force's Atlas
Intercontinental Ballistic Missile. It
was smaller with a pretty flexible
structure and used less dense cryogenic
[music] or low temperature fuels.
The Gemini Titan rocket was derived from
another missile, the Titan II. As it
needed to support two passengers, it was
larger, stiffer, and used denser
hypergolic fuels, substances that would
ignite upon contact with each other.
This new stiff frame with its long fuel
lines and the dense liquids within
created quite the headache for engineers
at launch, as they caused mission ending
pogo oscillations. Essentially, as the
fuel accelerates, a tiny natural
vibration in the the frame causes the
fuel lines to flex slightly. This flex
changes the pressure inside the fuel
line, forcing a sudden, tiny surge of
extra fuel into the engine. The engine
burns this extra fuel, creating a sudden
spike in thrust, a literal kick forward.
That extra kick ripples back up through
the rocket structure, causing the fuel
lines to flex even harder.
This all creates a closed feedback loop.
The rocket bounces up and down, which
pulses the fuel, which pulses the
engine, which bounces the rocket even
harder. It's like the rocket becomes a
giant pogo stick. But, whilst this might
sound fun,
on early Titan II test flights, bouncing
vibrations were recorded that were so
violent, they would have rendered an
astronaut unconscious.
This was because the Titan II was
originally designed to carry a nuclear
warhead, rather than people. So, the
initial engineering tolerances were a
bit aggressive.
NASA, unsurprisingly, refused to put a
human on the Titan II until the pogo
levels were reduced to below 0.25 G. So,
how did they do it?
Well, they had two choices. Start from
scratch building a new rocket that was
more flexible with shorter fuel lines
that ran on a new propellant, or they
could engineer solutions into the Titan.
With time being of the essence, they
chose option two.
NASA formed a pogo working group of more
than 1,000 engineers to come up with a
solution.
One of the main ways they reduced the
vibration was to put a shock absorber
into fuel lines called a surge dampener.
These were small cavities filled with
trapped, compressible gas, usually
helium, inserted directly into the fuel
lines.
So, when a pressure pulse traveled down
them, instead of hitting the engine and
creating a kick, it hit the gas cavity.
The gas then compressed just like a
mechanical spring, absorbing the energy
and smoothing the flow into a [music]
steady stream. This dampened the
vibrations and astronauts were able to
ride the Titan throughout the Gemini
program with no adverse [music] effects.
And this knowledge fed right into the
Apollo program's Saturn V rocket.
The Saturn V was a colossus, standing
around three times taller than the
Titan, but it had a completely different
fuel and structural makeup. In other
words, the engineers had no idea how it
would fare on takeoff. So, when during
the uncrewed Apollo 6 test, the rocket
began to shake, NASA engineers sprang
into action. Because of the legacy
Gemini data, they already had the
mathematical models to easily diagnose
Pogo, and the engineering solutions to
install similar suppressors in the
Saturn's [music] F-1 and J-2 engines,
preventing the rocket from shaking
itself to pieces and allowing astronauts
to ride it safely on the next test.
But, getting off the ground was just the
start.
Back in the early 1960s, the Gemini and
Apollo programs were running
concurrently. Gemini was the more active
training ground, while Apollo was still
on the drawing board. So, in 1962, when
NASA selected lunar orbit rendezvous as
a way for the Apollo mission to land, it
needed a command module for travel and a
separate lunar module to descend to the
lunar surface.
But, NASA had never even flown two craft
at the same time, let alone needing to
separate and reconnect them in the
depths of space.
This kick-started a whole testing phase
for the Gemini missions to work out how
to do it.
At first, engineers were skeptical about
the possibility of spacecraft that moved
at 28,000 km/h meeting in space, but it
was deemed worth a try.
This was one of the main aims of the
Gemini program, and the first mission to
test the new ideas was an intense
pursuit. Gemini 7 served as the passive
target, while Gemini 6A was launched to
find it.
>> [music]
>> They weren't just looking for a flyby.
They needed to achieve station keeping,
where two spacecraft travel at the exact
same velocity and altitude, appearing
motionless relative to each other. And
this required some deep scientific
thought and engineering ingenuity.
[music]
First, they used the Clohessy-Wiltshire
equations to understand and master the
paradox of orbit, why you need to slow
down to speed up to catch another
spacecraft. These formulas revealed that
to move forward, or speed up, a pilot
often had to fire thrusters not towards
the other spacecraft, but in reverse.
This dropped the craft into a lower
orbit with stronger gravity.
That accelerated them, allowing them to
gain ground before popping back up to a
matching orbit at the precise
microsecond of intercept. Secondly, they
used a digital onboard computer that was
linked to a Westinghouse L-band radar.
The radar bounced pulses off the target
to measure range, or distance, and range
rate, the closing speed.
The computer then translated these raw
pings into steering commands, replacing
guesswork with calculus, which is
usually more accurate.
And finally, NASA developed a
concentric, or co-elliptic, flight plan.
This kept Gemini 6A at a constant
altitude below Gemini 7, trailing it
like a shadow.
By maintaining this steady vertical gap,
the radar geometry remained stable and
predictable, allowing the crew to
transition into the final phase with
high precision.
And on the 15th of December, 1965,
this all played out for real.
From 435 km away, Gemini 6A's [music]
onboard computer crunched the numbers
for the long-range intercept. As the gap
closed to 80 km, the hunt became visual.
Gemini 6A's onboard astronaut Wally
Schirra reported spotting a bright star
that wasn't on any chart, which turned
out to be the glint of sunlight
reflecting off Gemini 7.
But there was a long way to go, and it
wasn't all smooth sailing. In the final
30 m, the geometry of orbit shifted too
quickly for 1960s processes to track, so
Schirra took manual control, peering
through an optical sight to nudge his
thrusters closer and closer until
success.
The science stood up, and they weren't
just close. At times, they were only 30
cm apart, staying there for nearly 5
hours and circling the Earth at 28,000
km per hour while remaining perfectly
still relative to one another.
But the final test was yet to come on
the 16th of March, 1966,
in Gemini 8.
They had shown it could find and get
close to a target. Now, Gemini 8 had to
prove they could join it. Harder still,
the vehicle it had to dock with was a
dumb target, an unmanned robotic stage
called the Agena. So, Gemini 8 had to do
100%
of the work.
Luckily, a hotshot pilot was at the
controls. You might even recognize his
name, Neil Armstrong.
Alongside co-pilot David Scott, who went
on to crew two Apollo missions himself,
Armstrong used the same playbook of
orbital and radar principles [music]
from the Gemini missions before this,
but then also had to add steering the
ship into a target docking adapter.
[music]
As he closed in at a speed of just 1.6
km/h, he took care to align them just
right as even a glancing blow could
potentially send both craft into an
uncontrollable spin, forcing them out
into space.
Inching closer, Armstrong switched to a
manual optical sight. He was now
balancing six degrees of freedom,
simultaneously managing thrusters for
rotational and linear movement. A few
minutes later, Gemini's nose slid into
the Agena's latches.
But just minutes [music] after the
successful docking, something happened
that could have caused the mission to
end in tragedy.
In the middle of a controlled maneuver
while turning the combined spacecraft 90
degrees, Scott noticed they were also
[music] rolling.
Armstrong attempted to stop it by firing
Gemini's thrusters, but the spin started
again and was [music] getting worse.
By this time, they were on the opposite
side of the planet from mission control
in Houston and out of touch with the
controllers there.
Armstrong and Scott were on their own
and struggling to regain control.
Soon the spin was so great that the pair
were finding it hard to even focus on
the instrument panels and there was a
very real concern that if the spin
continued, the Agena could start to
break apart and even explode. Suspecting
the problem was coming from the Agena,
Armstrong undocked, but this only served
to exacerbate the problem. Without their
combined mass, the Gemini capsule
accelerated, reaching a spin of one
revolution per second.
Centrifugal force began to pull blood
into the astronauts' heads. They were
seconds away from blacking out and
dying.
The problem was a stuck thruster in the
orbital attitude and maneuvering system
on the adapter module of the Gemini
spacecraft. Armstrong managed to turn
off the OAMS
and use the re-entry control system or
RCS to stop the spin, using 3/4 of its
propellant to achieve this.
With so little fuel left, Armstrong and
Scott had no choice than to immediately
return to Earth.
Whilst this forced an emergency landing
in the Pacific around 4 hours later, it
meant both astronauts kept their lives.
Despite this near-death experience, the
Gemini 8 crew had done what they set out
to do, to prove it was possible to join
another craft in orbit. And 5 months
later, the Gemini 11 mission perfected
the procedure, docking with the Agena
[music] 300 km above Earth just 94
minutes after launch.
This was an incredible achievement, to
go from peril to perfection in such a
short space of time, and one that would
pave the way for the future rendezvous
of Apollo 11's lunar module and command
and service module.
But this wasn't the only aspect of space
travel NASA was investigating. They also
wanted to master the EVA or
extravehicular activity, more commonly
known to you and me as a spacewalk.
Scientists had no idea how the human
body would stand up to the rigors of
space outside a capsule, if at all. Was
it even something NASA could prepare
their astronauts for?
Ground simulations can only go so far
when you're practicing walking on the
moon. So, after years of vacuum chamber
test,
>> [music]
>> NASA decided the only way to truly know
if a human could survive the void was to
[music] put their theories to the
ultimate test.
During Gemini 4, only the second crewed
mission of the program, astronaut Ed
White was tasked with the unthinkable,
opening the spacecraft's hatch and
stepping out into the vacuum of low
Earth orbit.
4 years earlier, the US [music] had
barely managed to put a man in space for
15 minutes. Now, they wanted to dangle
an astronaut outside the safety of his
spacecraft with nothing but a thin layer
of fabric between him and instant death.
While NASA was confident in the new G4C
[music] space suit it had developed, the
technology was brand new, having been
finalized just a year before.
>> [music]
>> On the 3rd of June, 1965, at 19:46 UTC,
it was finally put to a real-life
[music] test, and the atmosphere in
mission control was electric.
Though Soviet cosmonaut Alexei Leonov
had claimed the first spacewalk crown 3
months earlier, White was about nearly
double [music] his record, remaining
outside for a grueling 23 minutes.
Initially, it looked effortless.
White appeared to be walking on air,
proving that his pressurized suit could
maintain atmospheric stability while
allowing him to move.
But, that ease was deceptive.
To maneuver, White used the handheld
maneuvering unit, better [music] known
as the zip gun. By firing bursts of
pressurized oxygen, White used Newton's
third law, each action having an equal
and opposite reaction, to propel
himself.
But, this ran out of gas 3 minutes into
the spacewalk.
Without handholds or a stable platform,
[music]
he was unable to move around easily,
with many of his motions sending him
into chaotic [music] multi-axis tumbles.
The real danger, however, began when it
was time to get back into the spacecraft
and come home.
After White used his umbilical to climb
back to the craft, a mechanical
nightmare unfolded.
The spacecraft's hatch wouldn't lock. An
internal spring which usually meshed
gears together would [music] not
compress.
If they couldn't seal that hatch, they
couldn't re-pressurize the cabin,
meaning both White and Commander James
McDivitt would either run out of oxygen
or perish during re-entry. McDivitt
jammed his fingers into the mechanism,
forcing the gears together whilst White
manhandled the handle.
Inside the bulky pressurized suits, the
physical exertion was monumental.
By the time the gears finally clicked
into place, both men were drenched in
sweat, their heart rates spiking to
dangerous levels. NASA officially logged
the mission as a triumph, but the near
disaster changed everything behind the
scenes.
The easy spacewalk had revealed a
sobering truth. Performing [music] work
in zero G was far more exhausting than
anyone had predicted, and the lessons
learned on Gemini 4 would set the stage
for a much more difficult challenge five
missions later.
Gemini 9A.
Gemini 9A was meant to be a leap forward
in extravehicular activity with
astronaut Gene Cernan tasked to test the
astronaut maneuvering unit, a futuristic
rocket pack.
However, the mission was plagued with
catastrophic failures.
To protect against the AMU's hot
thrusters, Cernan's spacesuit was
additionally outfitted with metal
trousers made of Chromel-R, basically
like woven steel.
But once he exited the hatch, the vacuum
of space turned the metal trousers into
a rigid shell.
Cernan later described the experience as
having all the flexibility of a rusty
suit of armor.
The struggle was immediate.
Without adequate handholds or footholds,
every attempt to move triggered an
opposite reaction, causing Cernan to
spin uncontrollably.
The Gemini suit relied solely on
circulating oxygen for cooling, which
proved insufficient for the sheer
physical exertion needed to get
anywhere. It turns out they hadn't
completely learned their lesson in the
previous mission.
Cernan's heart rate hit 180 beats per
minute. He began sweating so profusely
that his visor fogged over completely.
To see, he had to rub the tip of his
nose against the glass to clear a tiny
patch. Recognizing the danger, Commander
Tom Stafford aborted the test. Near
blind, Cernan guided himself back to the
hatch by touch alone.
Reentering the cockpit was a nightmare
of excruciating pain.
The suit was so stiff that Stafford had
to help physically manhandle Cernan back
into his seat so they could force the
hatch shut.
After being out for 2 hours, they closed
the door and repressurized.
When Cernan popped open his visor, he
looked as red as a boiled lobster and
had lost nearly 6 kg of water weight.
Stafford was reportedly so concerned
that he took the water gun for drinking
and rehydrated food packages and
squirted him in the face to cool him
down, risking the loose water shorting
out electronics. This extremely near
miss led to two massive fixes for Apollo
that continue to this day.
The first was underwater training.
NASA realized zero-g aircraft lights or
30-second bursts weren't enough to
educate the astronauts, so they moved
EVA training to natural buoyancy tanks.
Spacesuits and vehicles [music] are
submerged so they hover in the water
with their weight balanced by the
buoyancy of the fluid so astronauts can
simulate long-term labor.
This training enabled Buzz Aldrin to
successfully complete his spacewalk on
the Gemini 12 mission, another name you
likely recognize.
Secondly, engineers realized that gas
cooling within a spacesuit was not good
enough for working astronauts. They
developed a liquid cooling garment, the
water-cooled long johns that allowed
Apollo astronauts to spend as much as 8
hours on the lunar surface without
overheating, a far cry from Gemini's
initial 23 minutes.
But it wasn't just time outside the
spacecraft NASA were worried about on a
moon mission. Getting there would take 8
to 12 days, and before Gemini, no one
knew if the human body or a spacecraft's
power systems could even last that long.
Before the Gemini program, NASA relied
almost exclusively on silver-zinc
batteries. These were the workhorses of
the Mercury program, chosen because they
offered the highest energy density of
any battery technology available at the
time.
But to power a command module for 2
weeks using only batteries on a mission
to the moon, the weight of the
silver-zinc cells would have added
thousands of kilograms to the
spacecraft, requiring a much larger and
likely non-existent rocket to lift it.
In other words, it was impossible.
So their solution was the fuel cell.
Unlike a battery, which stores energy, a
fuel cell is essentially a miniature
[music] chemical plant. It has liquid
hydrogen on one side and liquid oxygen
on the other.
These are separated by a proton exchange
membrane, essentially a polymer sheet.
This causes an electrochemical reaction
that generates electricity. As the
primary byproduct of this reaction was
pure water, it allowed astronauts to
essentially drink their fuel exhaust,
solving their weight problem of power
and water with a single elegant system.
But the debut of this system didn't go
well. On day one of the Gemini 5
mission, an oxygen tank heater failed.
Pressure plummeted and the fuel cells
began to lose power.
The crew had to turn off all
non-essential equipment and terminated
their rendezvous exercise.
Thankfully, the oxygen pressure
eventually stabilized at a low 71 PSI,
which meant they still had [music] the
minimum power required for a drifting
flight. Gordon Cooper and Pete Conrad
[music] spent nearly 8 days drifting in
a cold, dark capsule, essentially acting
as test subjects for a long duration
survival in a damaged ship. This lesson
in power conservation and so-called
trickle mode operation would, years
later, become the blueprint for saving
the lives of the Apollo 13 crew when
their oxygen tanks exploded and vented
into space just two days into their
mission.
With the technical aspect sorted, NASA
also needed to ascertain the impact of
long-term space flight on the human body
and mind.
So, just over 3 months later, on the
Gemini 7 mission, Frank Borman and Jim
Lovell were tasked with spending 14 days
inside a cockpit the size of the front
seat of a Volkswagen Beetle.
Scientists feared the human body might
break down in microgravity, with
astronauts' bones becoming so brittle
and porous that re-entry forces would
cause them to shatter. And in a way,
they were right. The results were
startling. Without the load of gravity,
bones did begin shedding calcium at an
alarming rate as astronauts peed out
their bones. But thankfully, not enough
for them to break on reentry. This
discovery gave the clinical proof that
led to the first space-based exercise
protocols and load-bearing restraints.
Because of the bone and muscle loss seen
on Gemini 7, Apollo was designed with
the much more robust physical
requirements.
The in-flight exercise program became a
daily scheduled task, a regiment of
running in place, isometric holds, and
resistance training on the Exer-Genie.
This mission also refined space food
technology.
After the sandwich incident of Gemini 3,
where John Young snuck a contraband
corned beef sandwich, unleashing
floating crumbs that could have posed a
serious short circuit risk to the
electronics, NASA invented a gelatin
coating for bite-sized food cubes,
literally sealing the food to prevent
disaster.
So, subsequent missions tested [music]
these snacks alongside rehydratable
meals, eating bacon squares, cinnamon
bread cubes, strawberry cereal cubes,
peanut cubes, chicken sandwich cubes,
coconut cubes, and brownie cubes.
Whilst they do sound tasty, I'm not sure
I'd like to try them.
The limited food choices were just the
tip of the iceberg when it came to the
less pleasant conditions the Gemini 7
astronauts had to endure.
By day 10, the trapped body odor and
stored waste inside the cramped,
unwashed capsule were overwhelming.
The crew even engaged in a suit war with
mission control. Doctors insisted at
least one of them stay suited for safety
at all times, but the stiff, hot suits
were causing unbearable misery.
Borman and Lovell eventually reached a
mutiny level of frustration, finally
winning the right to remove them. It was
a psychological victory where crew
comfort wasn't a luxury, but a safety
requirement.
This ultimately led to the Apollo
astronauts spending the majority of
their trips in much comfier attire,
flight coveralls or undergarments,
instead saving their bulky suits for the
more technical and dangerous aspects of
the mission where, should anything go
wrong, there were more deadly
consequences.
This was the launch, spacewalks, any
other technical procedures, and then
finally re-entry.
Getting astronauts back to Earth safely
is easier said than done.
While Mercury capsules were largely
passive during re-entry, Gemini
introduced the first onboard digital
computer, the IBM-built Gemini guidance
computer, and an inertial measurement
unit to help control descent. These
tools allowed astronauts to actively
steer the spacecraft during its landing.
By rolling the capsule to shift its
center of lift, a technique called
[music] lifting re-entry, crews could
actually consistently aim towards a
specific target landing rather than just
falling.
They were then puzzled when Gemini 3
missed its landing target by [music] 111
km.
Eventually, they realized that the
capsule didn't generate as much lift in
the atmosphere as their mathematical
models expected. So, they rebuilt the
aerodynamic profiles in the computer,
and by the end of the Gemini program,
Buzz Aldrin and Jim Lovell flew a fully
automatic re-entry, splashing down just
4.8 km from their recovery ship in
Gemini 12. This precision was
non-negotiable for Apollo. Without the
ability to steer through the atmosphere
and the navigation math perfected during
Gemini's rendezvous maneuvers, NASA
could never have guaranteed a safe
return from the moon or a reliable
pickup in the vast Pacific Ocean.
In total, the Gemini program may have
only lasted 20 months, but in that time
[music] it carried out 10 missions,
taking 16 astronauts beyond the realms
of our planet, and in doing so, it
changed the face of human space travel
forever.
Where Mercury had proven humans could
exist in space, it was Gemini that
allowed us to stay there, turning pipe
dreams into a reality and paving the way
for the lunar landings.
Apollo may today take all the glory, but
I hope you now agree that it was Gemini
that laid the groundwork to not [music]
only get us to the moon, but home again
safely. And these are all learnings that
are still very much in use today as we
strive to get back to the lunar surface
with the Artemis program, and then
perhaps even look beyond to Mars.
As we do so, we'll be using the same
fundamental physics and hard-won lessons
>> [music]
>> first mastered by the pioneers of
Gemini.
>> That's one small step for man,
one
giant leap for mankind.
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