The Truth About the First Moon Landing

0:00 57 years ago in July 1969, the world stood still, staring a go at grainy,

0:09 flickering televisions as Buzz Aldrin and Neil Armstrong

0:13 descended from the Eagle Luna module towards the moon.

0:20 Looking back, it feels almost like a fever dream of ambition.

0:24 This was only 66 years after the first airplane took flight.

0:30 But against all odds,

0:32 we broke free from Earth's gravity and touched another world.

0:38 Base here.

0:39 The Eagle has landed.

0:40 This frontier busting feat was presented as absolutely effortless.

0:45 A triumph of US might.

0:48 But was it really all plain sailing?

0:52 What the 600 million or so TV viewers had

0:56 no idea about was that this mission nearly failed.

1:01 Behind the scenes, approximately 400,000 engineers, scientists,

1:07 and experts worked tirelessly around the clock from incredibly detailed

1:12 plans years in the making to keep it all on track.

1:16 The slightest deviation could end not just in human tragedy,

1:21 but also have huge global political consequences.

1:26 So, how did this scientific army plan

1:29 for every eventuality and stop disaster in its tracks?

1:35 I'm Alex Mccoan and you're watching Astram Extra.

1:39 Join me today as we uncover the incredible

1:42 science that made the Apollo 11 mission possible.

1:46 We'll explore the launch, journey through space,

1:49 and descent onto the moon, digging into the meticulous maths,

1:54 maneuvers, and materials that kept the Apollo 11

1:58 team alive that most people don't even know existed.

2:04 The next time you go out at night, look up, find the moon.

2:08 Hopefully, you can't really miss it.

2:10 And now imagine going there,

2:13 traveling more than 384,000 km away from everything and anyone any

2:20 human being has ever known and actually landing on the moon.

2:25 It blows my mind to think about,

2:28 but nearly 60 years ago, three humans did just that.

2:34 On Wednesday the 16th of July 1969, an estimated half a million people descended

2:40 on the roads and beaches around Cape Canaveral.

2:43 They were here to witness the launch of Apollo 11,

2:46 humanity's first attempt at a manned moon landing.

2:51 A 110 m Saturn 5 rocket shimmerred in the distance.

2:55 The excitement was palpable.

2:58 But what none of these lawn chair

3:00 lounging enthusiasts knew was that a problem was

3:03 about to unfold that could stop the mission

3:05 before it even got off the launch pad.

3:08 Just as the crew arrived on site,

3:10 a leaking hydrogen replenish valve was discovered 60 m

3:14 up in the third stage of the Saturn 5.

3:17 Not something you want to see just before you're set to take off.

3:21 Because liquid hydrogen is kept at a bone chilling minus252° C,

3:27 it constantly boils off into gas as the rocket sits on the pad.

3:32 So, the replenish valve allowed the tank to be constantly topped up,

3:36 keeping it at 100% capacity.

3:38 This was vital.

3:39 Without a completely full tank,

3:42 the rocket would not be able to complete its trans lunar injection,

3:45 the burn that would take the craft out of Earth's orbit and towards the moon.

3:50 The leak was so severe it could have caused an explosion.

3:55 So fuel loading was immediately stopped and the lines were quickly drained.

4:00 It was only just over 2 years since the tragic

4:03 Apollo 1 fire where three crew members had died.

4:07 So there was no room for error and certainly no appetite for risk.

4:11 If the leak remained unressed,

4:13 the mission would be over before it even left the pad.

4:18 So, a brave crew consisting of three technicians

4:22 was dispatched to try and tighten the valve.

4:25 But with a little more than 2 hours to launch, time was running out.

4:30 The crew were working on the valve, manually tightening each bolt,

4:34 even as the astronauts were starting to board the craft just 30 m above them.

4:40 But when they still failed to stop the leak,

4:42 the crew took the extreme measure of pouring water

4:46 from an eyewash station over the valve where it froze.

4:51 While the resulting ice successfully isolated and sealed the leak,

4:55 it rendered the valve completely inoperable.

4:58 They needed another way to keep the tanks topped up.

5:02 Engineers decided to try using the large main

5:04 fill valve to keep fuel in the tank, something it was never intended for.

5:10 For the final hours of the countdown,

5:13 two engineers worked to keep the rocket flight ready.

5:16 One monitored fuel levels whilst the other turned the fill valve on and off,

5:22 topping up the tanks to compensate for boiloff.

5:26 Oxidizer tanks in the second and third stages now have pressurized.

5:29 Meanwhile, Buzz Aldrin, Michael Collins,

5:32 and Neil Armstrong sat in the command module in eerie silence,

5:36 preparing themselves for launch.

5:39 Now sealed off from Earth's atmosphere entirely,

5:42 they were concerned with a different gas,

5:45 one that was just as critical to their survival

5:48 as the integrity of the rocket itself.

5:53 During the planning stages, it had been decided that the Apollo

5:56 spacecraft needed to be as light as possible.

5:59 To make that happen,

6:01 a decision was taken to fill the astronauts module with pure oxygen.

6:06 Normal air is 78% nitrogen.

6:09 So only taking oxygen meant that they didn't need heavy tanks of nitrogen

6:14 and allowed for the use of a lower pressure within the craft.

6:18 combined this made for a lighter weight spacecraft.

6:22 Win-win, right?

6:24 Well, not really.

6:26 Oxygen is very flammable.

6:29 And this was a contributing factor in the Apollo 1 fire I mentioned before.

6:34 After that fire, the gas makeup NASA used was tweaked to a mix of 60% oxygen,

6:41 40% nitrogen to make it less flammable.

6:44 They also pressurized it at a much higher 16 psi.

6:48 So if any leaks occurred,

6:50 the air would flow out and not let the humid Florida air in.

6:55 Once they were safely in orbit,

6:57 the composition would then gradually be changed to pure

7:00 oxygen at a lower pressure of 5 psi.

7:04 But even this amended launch mix caused problems.

7:08 As I mentioned, normal air is around 78% nitrogen and 21% oxygen.

7:14 This mix meant that humans have a significant

7:17 amount of nitrogen dissolved in our blood.

7:20 Early testing showed that if astronauts took

7:23 off like this, when the cabin pressure dropped,

7:26 the nitrogen formed bubbles in their blood and joints,

7:30 causing a potentially lethal condition.

7:33 It was therefore mandatory for all the astronauts to change

7:37 their internal makeup before they even set foot on a rocket.

7:41 They did this by breathing pure oxygen for roughly 2

7:45 hours beforehand to flush out the nitrogen from their blood,

7:49 which is why you see them attached to what

7:50 looks like suitcases as they walk to the rocket.

7:54 That's the oxygen.

7:56 Having successfully purged the nitrogen from their veins to survive the launch,

8:00 the crew was ready to go.

8:04 10 9 ignition sequence start.

8:09 6 5 4 3 2 1 zero.

8:16 All engine running.

8:41 Heat.

8:41 Heat.

9:03 But this was just the beginning of their journey.

9:06 Now they actually had to get to the moon.

9:09 The astronauts started to prepare themselves for trans lunar injection,

9:14 the engine burn that would send them out

9:16 of low Earth orbit towards the mysterious moon.

9:20 This was a particularly dangerous part of the journey

9:23 as it required some exacting maths to ensure the correct trajectory.

9:28 Get it wrong and they risked being lost to deep space.

9:32 And they still had to make it out

9:33 of the lethal radiation field that blankets the Earth,

9:37 the Van Allen radiation belts.

9:42 The Van Allen radiation belts are essentially two concentric

9:45 donuts of radiation held in place by Earth's magnetic field.

9:49 Normally, they act as a shield protecting our planet

9:52 and us on it from the solar wind.

9:56 But for a spacecraft passing through them, they are a high energy gauntlet.

10:02 And in the 1960s, the lethality of these belts was a terrifying unknown.

10:08 Scientists were so concerned that they

10:10 even conducted high alitude nuclear tests,

10:14 including a mission called Starfish Prime,

10:17 to see if they could physically blow a hole

10:19 in the belts to create a safe passage for astronauts.

10:23 Needless to say, this was less than

10:26 effective and actually added radiation to the belts.

10:30 So instead, NASA's trajectory experts found a solution in geometry.

10:35 A team of so-called human computers, mainly poorly paid women who would go

10:40 on to become NASA's first computer programmers.

10:44 They tweaked the mass of the trans lunar injection

10:46 to exploit a loophole in the Earth's magnetic architecture.

10:50 It was much safer to go directly out

10:52 at the North or South Pole where there wasn't much radiation,

10:56 but doing so would have used up too much fuel.

10:59 The compromise was a slant trajectory.

11:03 NASA precisely angled and timed the launch and the burn.

11:07 So, the spacecraft would bypass the high density horns of the inner Van

11:11 Allen belt entirely and head through the weaker fringes of the outer belt.

11:16 But even after making it through the radiation belts,

11:19 the navigational problems didn't stop.

11:22 In fact, the chances of things going wrong only got higher.

11:28 When people think of Apollo 11 flying to the moon,

11:31 many imagine its engines were burning the whole time.

11:35 But to do that would have required too much fuel.

11:38 It would have made Saturn 5 so heavy, it wouldn't have made it off the ground.

11:43 Instead, for most of its trip through space,

11:46 engineers used physics to coast Apollo 11 to the moon.

11:50 Well, specifically where the moon would be in 3 days time.

11:55 It followed a figure of eight geometry that used

11:59 the moon's mass as a gravitational anchor and free accelerator.

12:04 This was called a free return trajectory,

12:07 a mathematical fail safe to ensure that if the spacecraft's engines failed,

12:11 the moon's gravity would naturally sling

12:14 the craft back towards the Earth's Pacific Ocean.

12:18 Once the Saturn 5's third stage had provided the initial shove,

12:21 the spacecraft became a ballistic projectile.

12:25 It was essentially falling away from Earth,

12:29 gradually slowing down until it reached the equiere,

12:33 the invisible tugof-war point where the moon's

12:36 gravity finally become stronger than the Earth's.

12:39 From that point, the moon's gravity took over,

12:42 accelerating the craft towards its destination for free.

12:46 But this required terrifying precision.

12:49 If the craft were too slow, it would fail to reach the moon's hillphere,

12:54 the zone where the lunar gravity takes over,

12:57 too fast, and they would overshoot the target entirely,

13:01 hurtling into a permanent solar orbit with no hope of return.

13:07 To hit the right window,

13:08 the Saturn 5's third stage had to ignite for exactly 5 minutes and 48 seconds.

13:16 But it wasn't just about time.

13:18 Velocity was also key.

13:20 The engine needed to add precisely 3.05 km/s to the rocket's orbital speed.

13:27 A deviation of just 1 second in burn time could mean

13:31 the difference between a historic landing and a drift into the cosmic dark.

13:38 Thankfully, it went exactly as planned,

13:41 taking the Apollo astronauts from around 28 12,000 km/h to more than 39,000 kmh.

13:50 But as they hurdled ever closer to the moon,

13:53 the astronauts needed to decouple from the Saturn 5 rocket,

13:57 they were currently encased in one of its top sections,

14:00 which was far too heavy to make it all the way to the moon.

14:05 The Apollo spacecraft was not a single cohesive vessel,

14:09 but a modular stack composed of three distinct sections,

14:13 all housed within Saturn 5's third stage.

14:17 There was the service module,

14:19 a windowless powerhouse containing the fuel cells and the primary propulsion,

14:23 the command module where the astronauts were for takeoff, and the lunar module,

14:29 the fragile two-stage craft designed for the lunar descent.

14:34 While we often imagine this trio flying as a single unit, in fact,

14:39 it required a complex piece of inflight assembly known as transposition,

14:45 docking, and extraction.

14:48 During launch, the Luna module was

14:50 stored beneath the command and service module,

14:52 tucked safely inside the spacecraft lunar module adapter,

14:56 essentially a protective garage on the upper neck of the Saturn 5's third stage.

15:01 This was necessary because the lunar module was far too fragile

15:04 to be directly exposed to the forces needed to climb through Earth's atmosphere.

15:11 Once trans Luna injection was complete

15:13 and the crew were coasting towards the moon, they had to build their new ship.

15:18 Pyrochnic bolts fired,

15:20 jettisoning four protective panels and exposing the lunar module.

15:25 The command and service module or CSM then detached.

15:31 To avoid damaging the delicate lunar module

15:33 with the massive heat of the main engine,

15:35 the astronauts used only the small reaction control system thrusters positioned

15:41 in the top of the CSM's cone to drift a short distance away.

15:46 At just 3 and 1/2 hours into the mission with surgical precision,

15:52 pilot Mike Collins turned the CSM 180°,

15:56 facing it back towards the spent third stage.

16:00 He then moved in for a nose ton-nose docking,

16:04 connecting the lunar module to the top of the CSM,

16:07 essentially wearing it like a hat for the remainder

16:10 of the 3-day journey to the moon.

16:13 Only with this mechanical connection complete,

16:16 could they now begin what NASA termed the trans lunar coast towards the moon,

16:21 trusting their navigation to a computer

16:24 with less processing power than a modern calculator?

16:28 But how did they know they were on course with no real landmarks,

16:33 only an empty vacuum?

16:40 While Project Gemini, the space program before Apollo,

16:44 had experimented with basic digital maths to aid navigation,

16:48 the Apollo program represented a paradigm shift.

16:52 It was the first time human lives were entrusted

16:55 to a computer for the entirety of a voyage into space.

17:00 The Apollo guidance computer or AGC developed

17:04 at MIT's instrumentation lab was a marvel of miniaturization.

17:09 At a time when most computers filled entire rooms,

17:13 the AGC was roughly the size of a briefcase.

17:17 It was also the first of its kind to utilize silicon integrated circuits,

17:21 the ancestors of the chips in your smartphone today.

17:25 By today's standards, its specs were pretty humble.

17:28 Just 4 kilob of erasable RAM and about 72 kilob of rope

17:34 memory software that had literally been woven into the copper wire by hand.

17:40 To know where it was in the featureless void,

17:43 the AGC relied on the inertial measurement unit.

17:47 This was the spacecraft's inner ear, a stabilized platform of three gimbal

17:52 gyroscopes and ultra sensitive accelerometers that allowed

17:56 the computer to track every nudge

17:58 of the thrusters and every shift in orientation,

18:02 maintaining a fixed reference in space without ever looking out a window.

18:09 But even the most advanced sensors in the 1960s were prone to drift.

18:14 Over time, tiny mechanical errors in the gyroscopes would accumulate,

18:18 causing the computer's internal map to slowly lose its alignment with reality.

18:24 To fix this, NASA turned to the oldest trick in the navigator's book, the stars.

18:30 From the cockpit of the command module,

18:33 Mike Collins used a sextant just like the 18th century sailors did.

18:39 He would peer through the optics to find two specific guide

18:43 stars from a catalog of 37 stored in the computer's memory.

18:48 Houston, we'd like you to press on to.

18:53 Then use the sex to measure the exact angle

18:56 between these stars and the Earth or Moon's horizon.

19:01 Finally, he fed this data back into the computer,

19:04 detailed as a P23 sighting, which allowed it to reset its internal gyroscopes.

19:12 The crew were now on a straight path to the moon.

19:16 And you might think this meant things got easier,

19:19 but in reality, it created a lethal thermal nightmare.

19:23 One extreme enough to rip their ship apart.

19:32 In the vacuum of space, there is no atmosphere to circulate heat,

19:36 which creates a world of thermal extremes.

19:39 The side of the spacecraft facing the sun

19:41 can bake in temperatures as high as 121° C,

19:45 while the side shrouded in shadow plunges to a staggering- 157°.

19:53 Without intervention,

19:55 these massive temperature gradients would have caused the metal

19:58 skin of the service module to expand and contract unevenly,

20:02 potentially warping the structure, freezing fuel lines,

20:06 or frying the delicate electronics nestled just inches away.

20:10 So NASA used a maneuver called passive thermal control,

20:15 more colloally known to the engineers and astronauts as the barbecue roll.

20:20 Just like a rotisserie chicken over a fire,

20:23 the spacecraft was set into a slow rhythmic spin

20:27 of exactly three revolutions per hour, or roughly 0.3°/s.

20:34 This constant motion ensured that no single part of the hull was

20:38 exposed to the sun or the cold of deep space for too long.

20:42 The internal systems and the astronauts inside remained

20:46 at a steady room temperature of approximately 21° C.

20:51 It was a low tech solution to a high stakes problem.

20:55 But whilst the temperature was stable,

20:57 the astronaut safety was a different story because

21:01 out in space there is one other big threat.

21:06 Radiation.

21:08 As I mentioned earlier, Earth is protected by a thick atmosphere

21:12 and the invisible magnetic donuts of the Van Allen belts.

21:16 But once the spacecraft leaves these protective shields,

21:20 it enters a shooting gallery of high energy particles.

21:24 High doses of these particles could cause acute radiation sickness, nausea,

21:30 and disorientation, which would lead to fatal

21:32 errors during a complex lunar landing.

21:35 Not to mention the risk of developing cancer later in life.

21:40 Solar particle events caused by solar flares or chronal mass ejections

21:46 could flood the spacecraft with a sudden deadly burst of protons.

21:50 These solar storms are powerful enough to not only irradiate human tissue,

21:56 but to scramble the delicate silicon of the Apollo guidance computer.

22:01 Since a leadline ship would be too heavy to ever leave the ground,

22:05 NASA had to rely on intelligence and timing.

22:09 First, they established the Solar Particle Alert Network.

22:14 This was a global ring of observatories that monitored the sun 24 hours a day.

22:19 If a major flare was spotted, a warning would be sent to Houston,

22:23 giving the astronauts time to take cover

22:25 in the most shielded part of the command module.

22:28 Counterintuitively, NASA had actually timed the Apollo

22:32 program to coincide with the solar maximum,

22:35 the period in the sun's 11-year cycle where it is most active.

22:40 While this increased the chance of a solar flare,

22:43 it also strengthened the heliosphere,

22:46 a bubble-like region of space around the sun

22:48 and planets caused by the solar wind.

22:51 During solar maximum,

22:53 the sun's intensified solar winds acts like a magnetic umbrella,

22:57 pushing away much more powerful and harder to block galactic cosmic rays.

23:02 By accepting the risk of a storm they could monitor,

23:06 NASA shielded the astronauts from the constant drizzle of deep space radiation.

23:12 But this constant monitoring required a communication line to be

23:15 open between the astronauts and Earth the whole time.

23:19 And that's not easy given the 300,000 km distance

23:23 and the fact that the world had not yet invented fiber optics,

23:26 a global satellite network or the internet.

23:32 In the vacuum of space, there is absolute silence.

23:36 So instead, to bridge the nearly 384,633 km

23:42 gap between Earth and the Moon, every word,

23:46 every command, and every shot of grainy television

23:49 footage had to be converted into electromagnetic radio waves.

23:56 Despite traveling at the speed of light,

23:57 these signals still face the difficulty of distance, which created a small lag,

24:03 a delay of about 1.3 seconds each way,

24:06 meaning an astronaut had to wait nearly 3 seconds

24:09 for an answer to any question sent to Houston.

24:12 To handle the massive amount of data needed to be sent back and forth,

24:17 NASA developed the unified Sband or USB system.

24:21 Operating in the 1.5 to 5.2 2 GHz range.

24:26 This was a masterpiece of integration.

24:28 Rather than having separate radios for voice, video, and spacecraft health data,

24:34 the USB combined them into a single highfrequency stream.

24:40 Managing the stream was the manned space flight

24:43 network coordinated by the Goddard Space Flight Center.

24:46 Because the Earth is a rotating sphere, NASA couldn't rely on just one antenna.

24:51 They deployed a global safety net to ensure messages got through.

24:56 This net consisted of 17 ground stations scattered from Madrid to Canberra,

25:02 four tracking ships positioned in the vast

25:05 stretches of the Atlantic and Pacific,

25:07 and a fleet of eight Apollo range instrumentation

25:10 aircraft designed to catch signals where ships couldn't reach.

25:15 and all these signals needed to be able to be

25:18 received by the spacecraft which had its own specialized technology.

25:23 The command module used four omnidirectional antennas for close range but once

25:28 in deep space it relied on a steerable high gain antenna,

25:32 a cluster of four 31in parabolic dishes.

25:38 The Luna module carried its own 26-in steerable dish.

25:42 And for the historic broadcast from the lunar surface,

25:45 the astronauts even deployed a 10 ft collapsible umbrella

25:49 antenna to ensure the world could see their first steps.

25:54 But even with all of this, there was a hole.

25:57 For roughly 48 minutes of every 2hour lunar orbit,

26:01 the craft would pass behind the far side

26:04 of the moon and the signal would be lost.

26:07 In this window, the astronauts were truly alone,

26:10 cut off from all human contact until they

26:14 rounded the corner and Earth rose over the horizon.

26:18 This meant that huge sections of one of the most

26:20 important moments in the mission occurred in radio silence.

26:26 The descent.

26:29 In the decade leading up to the Apollo 11 landing,

26:32 the lunar surface was a scientific enigma that invited terrifying speculation.

26:38 Without direct physical samples,

26:40 NASA's planners had to account for a myriad of potential theories.

26:45 The most prominent of these was the fairy castle

26:48 theory proposed by Cornell astrophysicist Thomas Gold in 1956.

26:54 He argued that billions of years of micrometeorite bombardment had ground

26:59 the lunar surface into a fine electrostatic dust in the moon's vacuum.

27:04 He said these grains would cling together in loose porous structures

27:08 like fairy castles that would have the structural integrity of a spiderweb.

27:14 Gold warned NASA that even though on the moon

27:17 it would be 2.5 tons thanks to lower gravity,

27:21 a 15tonon lunar module wouldn't be able to land on this surface.

27:26 It would sink like a stone into water,

27:29 burying the astronauts in a miles deep sea of dust.

27:34 Other researchers such as JD Bennell feared a different kind of instability.

27:40 They theorized that the lunar regalith might be pyrooric,

27:44 chemically hungry, and highly reactive.

27:47 He worried that the moment the hot exhaust touched the pristine lunar soil,

27:52 it would trigger a violent explosive chain reaction.

27:57 Even the craters themselves were a source of dread.

28:00 Some geologists believed that the lips of the lunar craters were so

28:03 fragile the mere weight of a spacecraft would cause a catastrophic collapse,

28:09 tipping the lunar module and leaving the crew stranded on their sides,

28:13 unable to launch back to orbit.

28:16 NASA's engineers couldn't disprove these theories,

28:20 so they did the only thing they could.

28:22 They overengineered for every possible nightmare.

28:28 The Luna module was designed with a wide spled stance.

28:32 Its four landing legs contained honeycomb

28:35 aluminium structures designed to compress upon impact,

28:38 absorbing the shock of a hard landing and preventing the craft from tipping.

28:43 At the end of these legs sat 37in circular foot pads,

28:48 large discshaped snowshoes designed to spread the LM's weight across the dust,

28:55 ensuring it stayed on the surface rather than sinking into it.

28:59 Dangling beneath three of these foot pads were 68in long blue probes.

29:05 They were the spacecraft's cat whiskers.

29:09 The moment the probe touched the lunar soil,

29:12 a lunar contact light would glow blue in the cockpit.

29:15 This was the signal for the astronauts to shut down the engine immediately.

29:19 A critical move to prevent the engine

29:21 pressure from building up against the ground

29:23 and potentially causing an explosion or blowing

29:26 out a massive unstable crater beneath them.

29:30 If the ground began to give way or if the quicksand proved real,

29:34 the astronauts had a panic button.

29:36 The abort guidance system allowed for multiple

29:40 abort modes with a single command.

29:42 The bottom half of the LM called the descent stage would

29:46 be jettisoned and the other half named the ascent stage would fire,

29:50 kicking the crew back into the safety of orbit.

29:54 This ability for the LM to split into two halves was the ultimate fail safe.

29:59 The ascent stage was an entirely independent spacecraft designed

30:03 to fly even if the descent stage was tilted, sinking, or physically damaged.

30:10 Inside the Luna module cabin, the paranoia of the unknown continued.

30:15 Every inch of the interior was stripped of flammable materials

30:19 backed by dual redundant oxygen tanks and extra power reserves.

30:24 Because on the moon, there was no such thing as a minor complication.

30:29 The Apollo 11 team was ready for any eventuality.

30:34 And at 1:44 p.m.

30:36 ET on the 20th of July, 1969, Neil Armstrong and Buzz Uldren left my Collins

30:44 in the CSM and began their descent to the lunar surface.

30:49 But it was far from a smooth ride.

30:55 12 minutes.

30:56 That was the time it took for Apollo 11 to fall from orbit to history.

31:01 And it was a descent defined by chaos.

31:05 It began with a positional error.

31:08 As the LM Eagle emerged from behind the moon,

31:11 Neil Armstrong realized that they were

31:13 passing landmarks 3 seconds ahead of schedule.

31:17 A tiny bit of residual pressure in the docking

31:19 tunnel had given them an extra shove,

31:22 meaning they were drifting towards a boulder strewn crater

31:26 instead of a flat plane they were initially aiming for.

31:30 Then the silence was shattered by the 1202 program alarm.

31:36 Inside the cramped cabin, a yellow caution light flickered.

31:41 The primary guidance computer, a machine with less memory than a modern car key,

31:46 was being overwhelmed by cycle steals.

31:50 In other words, a faulty radar switch

31:52 was flooding the processor with useless data, forcing it to reboot mid descent.

31:59 And while you were dropping to a completely unknown surface at more than 100

32:03 kmh is possibly the worst time I can think of to have it issues.

32:08 Down in mission control,

32:10 26-year-old Steve Bales had seconds to decide, abort or land.

32:17 Trusting the software's ability to prioritize critical tasks, he gave the go.

32:23 But the drama wasn't over.

32:25 As Eagle dropped below 150 m,

32:28 Armstrong looked out the window and saw a crater filled with jagged rocks.

32:33 If they landed here, the mission would end in a tip over or a ruptured hull.

32:39 With nerves of steel, Armstrong took manual control.

32:45 He tilted the craft forward, skittering over the boulders,

32:49 searching for a clear patch of dust.

32:52 In the background, Buzz Uldren called out altitudes

32:55 and descent rates while a new crisis emerged.

32:58 The fuel light.

33:00 Because they had hunted for a landing spot for so long,

33:04 2 to 3 minutes, the fuel was splashing around, triggering a lowle sensor.

33:11 Houston called out 60 seconds, then 30 seconds.

33:15 If they didn't touch down before the clock hits zero,

33:18 they would have to abort the landing and ignite the ascent engine or crash.

33:25 Dust kicked up by the engine obscured the ground,

33:29 robbing Armstrong of his depth perception.

33:32 He relied on the contact light probes dangling from the landing gear.

33:37 At 4:17 p.m.

33:40 ET, the blue light flashed.

33:43 Armstrong throttled down and the Eagle settled into the sea

33:47 of tranquility with barely 25 seconds of fuel remaining.

33:52 The troubleshooting was complete.

33:55 The impossible had been done.

33:59 Uh, Tranquility Base here.

34:01 The Eagle has landed.

34:03 Roger, TW Tranquility, we copy you on the ground.

34:06 You got a bunch of guys about to turn blue.

34:08 We're breathing again.

34:09 Thanks a lot.

34:12 Very smooth touchdown.

34:17 Man had landed on the moon.

34:22 But this wasn't merely a triumph of three men.

34:26 Behind every maneuver and step taken on this journey to the moon

34:30 was a masterpiece of collective

34:33 human intelligence spanning countless specialtities.

34:37 The mission was a tapestry woven from a million strokes of genius,

34:43 solves, fail safes, checklists, and foresight.

34:47 the physical manifestation of hundreds of thousands of minds

34:51 working together to push humanity forward in one great leap.

34:56 It was proof that when focused on a singular impossible goal,

35:01 the quiet expertise of many could carry the few safely to a world unknown.

35:08 But this isn't the end of the Apollo 11 saga.

35:11 Join me again soon for part two where we

35:14 continue to uncover the scientific fingerprints that coat this mission.

35:19 We're stripping back the layers of the most iconic armor

35:22 in history to reveal the scientific secrets of the lunar space suit.

35:27 We'll dive into the high stakes orbital ballet required

35:30 to reunite the astronauts in the silence of the void.

35:34 And finally, we'll face the ultimate trial by fire.

35:38 The vital physics of re-entry, where a thin shield was all that stood

35:43 between the crew and a 3,000 degree inferno.

35:48 The journey home has only just begun.