Hey 42 here.

>> It started as a fiery accident.

>> That tsunami has already engulfed some

cities for 3 years now. We've struggled

with these droughts.

>> The risks we face from nuclear weapons,

climate change, and disruptive

technologies.

[screaming]

>> If you've spent any time watching the

news lately, you've probably come to the

same conclusion that I have.

Ukrainian authorities tried to hide the

disaster.

>> We as a species.

>> This is the closest the world has ever

been to midnight. A

>> whether it's another deadly pandemic,

AI, the next world war, or a bloody

great asteroid with our name on it.

Sooner or later, something is going to

come along and murder every single last

one of us. There are so many dangers

facing our species that on the face of

it, our doom seems certain.

But it turns out there's a surprisingly

simple solution that could at least in

theory protect us from every single one

of those threats.

We need to spread out a bit.

As of today, humanity's eggs are all

piled up in a great big space [music]

basket we call Earth. We're sitting

ducks, dangerously vulnerable to any

number of different doomsday scenarios.

But if we're able to establish human

colonies on other planets,

no disease, asteroid, or environmental

collapse will be able to touch us. Or at

least not all of us. As you may already

be aware, space is big. In fact, I don't

think it's unreasonable to say that

whoever built this server we call the

universe completely messed up when they

coded the scale. The closest star system

to our own, Alpha Centuri, is about 4.2

light years away. That might not sound

all that far, but it is very.

This right here is the Voyager 1 space

probe. As of right now, it is the most

distant man-made object from our home

planet. In the late summer of 1977, two

unmanned spacecraft, Voyager 1 and 2,

lifted off from Cape Canaveral a top

Titan Centaur rockets. And after popping

by to visit Jupiter and Saturn on its

way through the solar system, it's been

hurtling away from our home world at a

nippy 38,000 mph.

That's about 20 times faster than a

bullet from an AK-47.

But in almost 5 decades traveling at

this absurdly rapid pace, Voyager 1 has

covered a grand total of just 0.0026

light years, a smidge under a single

light day. Voyager 1 isn't heading for

Alpha Centuri, but if it was at its

current speed, it will get there in

about 77,000

years. 77,000 years just to visit our

closest neighbor. Like I said, someone

totally effed up on the scale of this

place. You might be thinking that given

Voyager 1's age, we probably have newer,

better technology capable of propelling

space probes to much greater speeds.

>> And as it happens, we do.

>> And liftoff. The crew of Artemis 2 now

bound for the moon. Humanity's next

great voyage begins.

>> But even the fastest modern probes would

still take tens of thousands of years to

reach Alpha Centuri. For the time being,

we're stuck right here on planet Earth.

Or are we? A decade before the launch of

Voyager 1, the entire planet was gripped

by the space race. After the Soviet

Union took an early lead with the launch

of the Sputnik satellite, the US

ultimately took home gold by putting a

man on the moon. If you know your ass

from Neil Armstrong, you'll know that

the moon landing, made possible by

NASA's Saturn 5 rocket, was the crowning

achievement of the Apollo program. But

what you might not know is that the

Saturn series of rockets weren't the

only option seriously considered for

flying men to the moon. During the late

50s and early 60s, the US government

invested in a top secret alternative

with the code name Orion.

And in every way that counted, it

appeared to be the more promising

option. Orion was far bigger and far

faster than Saturn 5. Big enough and

fast enough to launch city-sized

spaceships across the vast distances

between the stars. But NASA never built

it. Not because it didn't work, but

because Orion's unbelievable performance

came with one small catch.

Unlike Saturn 5, which used traditional

chemical rockets for propulsion, Orion

was [music] quite literally blasted into

space by riding the explosions of

thousands upon thousands of nuclear

bombs. This is the story of a

nuclearpowered starship powerful enough

to change the future of humanity and

terrifying enough never to be built.

Project Orion.

You know, for a long time I was working

seven days a week on this channel and I

thought I was fine. I [music] genuinely

thought I was just being productive, but

the people closest to me could see what

I couldn't. I was chronically stressed,

constantly irritable, and I basically

stopped being present for anyone. I was

coasting along thinking everything was

normal whilst the people around me were

dealing with the fallout. It took me a

while to realize that my mental health

was suffering. Not because something

dramatic happened, but because I'd lost

perspective entirely. And that's the

[music] thing about therapy. Sometimes

you don't need it for a crisis. You need

it because you can't see what's right in

front of you. And a fresh perspective

[music] from someone qualified can make

all the difference. That's where today's

paid partner, BetterHelp, comes in.

[music] BetterHelp makes starting

therapy easy. You take a short quiz, get

matched with a credentialed therapist,

[music]

and you can switch anytime at no extra

cost if it's not the right fit. Advice I

received from Better Help was to focus

my work when [music] my brain was most

active, usually in the mornings, so I

get more done in less time. And since

doing that, [music] I've had much more

free time to spend with others. Over 6

million people to date have gotten help

through Better Help, earning a 4.8 out

of five rating on the App Store. [music]

So, click the link in the description or

go to betterhelp.com/42

and get 10% off your first month of

therapy.

To launch a rocket into space, you need

a lot of fuel. To carry a lot of fuel,

you need a big rocket. And to launch a

big rocket, you need even more fuel. And

here is the result. Mass percent

propellant. They're all around 90%. Your

rocket sitting on a launchpad, 90% of it

is propellant. 10% of it is everything

you think of as the rocket.

>> This feedback loop formalized in

something called the Silkovsky rocket

equation is baked into the physics of

chemical propulsion and it places

practical limits on how big and how fast

chemically propelled rockets can get.

When Apollo 11 blasted off from the

Kennedy Space Center on the 16th of July

1969, about 90% of its total mass was

fuel and only about 4% made it to the

moon as payload. If we'd wanted Apollo

11 to fly faster or carry more, we would

have needed a dramatically larger rocket

carrying vastly more fuel. This basic

trade-off is unavoidable when using

chemical rockets. Which is why in the

late 1940s, mathematician and

theoretical physicist Stanislav Ulam

dared to ask a bold question.

What if we don't use chemical [music]

rockets at all?

Ulam was a key member of the Manhattan

project during the Second World War and

these days he's probably better known as

one of the architects of the Teller Ulam

design, the breakthrough that made

modern thermonuclear weapons [music]

possible.

But in the years after the war, Ulam

became increasingly interested in other

applications of nuclear energy. One of

which was a radical new way to power

spacecraft, something we now call

nuclear pulse propulsion.

We think of nuclear bombs almost

exclusively as instruments of mass

destruction. But at their cold

radioactive cores, nuclear devices are

essentially just extraordinarily

powerful energy sources. If we could

somehow harness that raw power and turn

[music] it into momentum, we could build

a spaceship that would completely ignore

the limitations that hamstring chemical

rockets.

The nuclear pulse propulsion design went

through several iterations over the

following years, but it ended up looking

something a bit like this. Instead of

burning chemical fuel continuously

inside an engine, the craft was

propelled by nuclear bombs. Each ship

would carry hundreds or even thousands

of so-called pulse units, small nuclear

devices wrapped in propellant. These

pulse units would be released every few

seconds, detonating around 25 m behind

the ship,

and careful bomb design would send a

high velocity jet of plasma straight

into a large metal plate. A

shockabsorbing system between the plate

and the craft would smooth out each

impact, turning a series of incredibly

violent nuclear explosions into

something approaching steady

acceleration. Such a craft would be

capable of carrying payloads measured in

the thousands of tons and reaching

speeds chemical rockets could only dream

about.

If that sounds utterly insane, that's

because it absolutely was. But

amazingly, early theoretical models

suggested it just might work. In fact,

early models suggested it might be

absolutely bloody amazing. The concept

was picked up by US defense contractor

General Atomics where it was given the

code name Orion and placed under the

leadership of Theodore Taylor, another

alumni of the Manhattan Project.

Taylor saw the potential of Orion

immediately, but he knew that to realize

that potential, he was going to need

more than talented scientists. He needed

genuine visionaries capable of thinking

on a scale that most people only dream

of. Luckily, he had exactly the right

candidate in mind. Freeman Dyson.

By the late 1950s, Dyson was already one

of the most highly respected theoretical

physicists in the world. He worked on

nuclear weapons theory, contributed to

quantum electronamics, and developed a

reputation for seeing connections that

others missed. Even more importantly,

Dyson was a man known for thinking big.

He worked out how Orion scaled, how to

tame its wild acceleration into

something survivable by humans, and just

what the hell we might do if we could

make it all work. In complete contrast

to chemical rockets, Dyson's

calculations showed that Orion didn't

just tolerate scale, it benefited from

it. Larger ships were more efficient,

smoother to accelerate, and easier to

protect from both the forces of the

bombs themselves and the resulting

radiation. The more research was done on

nuclear pulse propulsion, the less it

was viewed as a spectacular but

speculative way to launch something into

space. Instead, it began to be seen by

some as a logical, perhaps even an

inevitable evolution in human space

travel.

Dyson put together various different

profiles for potential Orion missions.

On the smaller end, he envisioned a

spacecraft weighing about 900 tons.

That's less than a third the size of

Apollo Saturn 5's rocket. Yet, it could

carry a payload almost three times

heavier. A midsized Orion would have

weighed about 4,000 tons. Not all that

much bigger than the roughly 3,000 ton

Saturn 5. But a midsized Orion was

capable of carrying a payload more than

10 times heavier. Dyson even worked on

designs for an Orion weighing 10,000

tons, capable of carrying payloads in

excess of 6,000 tons than a single

launch.

These were designs Orion engineers

believed could be built with current

technology. And they were completely

rewriting the rules of space travel. And

it didn't stop there. In the late 1950s,

General Atomics published a classified

paper that attempted to answer a simple

question. Just how big can this thing

get? The paper's biggest design was an 8

million ton BMoff the size of a small

city that could have served as a genuine

interstellar colony ship.

And it wasn't just Orion's potential

size that had scientists excited. It was

also the speed. Orion studies calculated

truly mind-boggling theoretical top

speeds. In some cases, approaching 5% of

the speed of light. As we've seen, even

modern chemical rockets would need tens

of thousands of years to reach the

nearest star system, Alpha Centuri. But

traveling at 5% of the speed of light,

Orion could get there in under a

century, the length of a single human

lifespan.

>> Soviet Union launched a little ball and

that little ball went around the Earth

with little beeps that said, "We can hit

you. We can hit you. We can [music] hit

you." In 1958, the newly formed Advanced

Research Projects Agency, DRPA, known

these days as DARPA, began quietly

funding Orion Research to the tune of a

million dollars a year. That might not

sound like much, but it signals

something important. The US government

viewed Orion as more than just a

scientific curiosity. The US Air Force

also got involved, keen to understand

the military applications of this

potentially revolutionary technology.

Air Forceled research investigated the

possibility of using Orion as a launcher

for a massive Death Star orbital weapons

platform capable of striking anywhere on

Earth. As the funding and interest

levels continued to increase, the

growing Orion team, now with some 40

full-time members, began taking the

first steps towards turning their

theories into reality. For obvious

reasons, fullscale Orion tests were a

bit of a challenge.

So the team used conventional explosives

to test the underlying physics. Small

scale Orion models known as pututs were

built and launched using TNT pulse units

rather than nuclear ones.

The most successful test sent a single

putt put 100 m into the air. And despite

the violent method of propulsion, the

flight was both predictable and stable.

Extensive work was also being carried

out on one of the most challenging

aspects of the entire concept, the

pusher plate. Multiple designs were

explored, but they all face the same

problem, surviving hundreds or even

thousands of nuclear detonations, each

delivering extreme shock and

temperatures in the tens of thousands of

degrees. The temperatures were the

biggest concern, but these thermal

spikes were incredibly short-lived,

lasting just milliseconds. That

minimized heat transfer to the plate.

Something that could be further

mitigated by adding a renewable oil

coating that would flash vaporize with

each explosion, carrying heat away

before it could cause damage. And so,

one by one, the team overcame most of

the biggest hurdles involved with

building Orion. As they did so, they

proved it wasn't just the physics that

worked. The engineering did too. Despite

the progress, the US Air Force abruptly

dropped their support of the project.

By the end of the 50s, the first true

intercontinental ballistic missiles were

appearing on the scene.

>> We believe we can greatly compress the

time from the initiation of our

development program until we get our

first units into the operational

inventory.

Given that they could strike distant

targets in a matter of minutes from

groundbased silos, they rendered the

idea of an orbital nuclear weapons

platform mostly redundant. With the

military stepping back, the Orion team

turns to the only remaining organization

with both the resources and the

motivation to pursue something as

ambitious as Orion.

NASA. By the early 60s, NASA was already

very much focused on the Saturn series

of rockets for Apollo. Designed under

the guidance of the so-called father of

space travel, Verer von Brawn.

>> I have always considered President

Kennedy's commitment that we are going

to put men on the moon of this decade an

objective very clearly defined [music]

which cannot be debated.

>> He's a really interesting character, by

the way, famed for developing the

infamous V2 rocket for Hitler. The

Americans imported him straight from

Nazi Germany after the Second World War.

So, let me know if you'd like to see a

video on him in the future. Despite the

focus on chemical propulsion, NASA was

interested in exploring Orion's almost

science fictional specifications

interested enough to commission a number

of classified studies. One proposal

explored the possibility of using Orion

for a manned Mars mission. The study

outlined a flight profile in which Orion

would take eight astronauts on a round

trip to Mars and back in just 125 days.

Now, this work was carried out more than

60 years ago. And yet these numbers are

far beyond anything we could

realistically achieve even today.

For comparison, NASA's most recent

high-profile Mars expedition, Mars 2020,

>> we have started our constant velocity,

>> an unmanned mission with no concern for

crew health or life support. Took nearly

7 months to reach the red planet.

>> Touchdown confirmed. Perseverance safely

on the surface of Mars.

>> The cost estimates were just as

striking. The projected development cost

for the theoretical Orion Mars mission

was around $1.5 billion. As a

comparison, the Apollo program that took

NASA to the moon in 1969

cost more than $25 billion.

It was almost too good to be true.

better than Apollo by every measure. But

you don't have to be a space nerd to

know what happened next. Had Orion taken

Neil and the gang to the moon, I

wouldn't be making this video. NASA

chose the Saturn rockets for the Apollo

program. The question is why? Well, it

turns out there was a growing divide

between the scientists working on Orion,

people like Freeman Dyson, and to some

extent von Brawn, and the administrators

and politicians who ultimately signed

off on NASA's decisions.

When the scientists looked at Orion,

they saw sound physics and near

limitless potential. But when the suits

looked at the same project, they saw

something very different.

>> The light flash and the heatwave, then

the blast tears away part of each roof.

>> Risk. Massive. Unavoidable risk.

Space flight is a dangerous business.

Launchpad explosions were common.

Guidance systems regularly failed and

many missions were lost. [music]

[singing]

With Saturn series rockets, these

incidents were sometimes deadly, but

they were always local. Orion was

different. A launch failure might

conceivably have set off a chain of

reaction of hundreds or even thousands

of nuclear bombs. Even worse, a failure

in the upper atmosphere might have

spread radioactive fallout halfway

across the planet.

That was one hell of a risk to take in

the name of science. And the truth is,

there was no compelling reason to take

it. Apollo was already well underway,

and the Saturn rockets, whilst nowhere

near as capable as Orion on paper, were

good enough to do the job. More

importantly, they used designs we'd

already built and technology we already

understood. The rest is history.

Orion research did continue for a couple

more years, but in 1963, the already

weakened project was delivered a mortal

combat style fatality by the signing of

the partial testban treaty. The treaty

banned nuclear detonations in the

atmosphere, underwater, and even in

outer space. Practically overnight, the

core idea the entire project was built

on became illegal under international

law. Orion's nuclear race was run.

It's amazing to think that even today,

so far as we know, the Orion concept is

viable. Not to mention orders of

magnitude more capable than anything

we've built since. With modern

technology and materials, we could

probably have a pretty good go at

building it, too. Which leads us to the

obvious question. Given that

establishing human colonies on other

planets is clearly our best chance of

securing the long-term survival of our

species, is there any chance the project

might be revived? Well, the short answer

is no. Almost certainly not. [music] A

functioning Orion rocket would be just

as illegal to operate today as it was in

the '60s. But it isn't the only reason.

High-profile disasters like Chernobyl

and Fukushima have turned nuclear

technology into a political liability. 3

years after the Fukushima disaster,

thousands of anti-uclear demonstrators

have filled the streets of Tokyo.

>> I find it difficult to imagine an

accident that could be any worse than 3M

Island without actually harming members

of the public.

>> Even the most basic use of nuclear

energy as a civilian power source is

highly controversial in some countries.

The idea of blasting a rocket into space

on a trail of nukes is always going to

be a tough cell. There's other concerns,

too. As a civilization, we've spent the

last few decades trying to reduce the

nuclear stockpiles around the world. But

an operational Orion program would

require the mass production of thousands

upon thousands of new devices. By

design, they wouldn't be weapons, but a

nuke is still a nuke. No. Despite its

incredible promise, Orion will almost

certainly never be built. But the ideas

it's based on are so powerful, they've

never quite gone away. In the 1970s and

80s, two high-profile studies, Project

Aidus and Longshot, attempted to harness

the incredible performance of nuclear

pulse propulsion in a less explosive

manner. Both explored the viability of

fusionpowered NP. Instead of detonating

huge fishing bombs behind the ship,

Dadeless and Longshot proposed firing

thousands of tiny fishing fuel pellets

into an inship reaction chamber before

compressing them to trigger controlled

fusion micro explosions, generating

pulsed thrust without giant nuclear

weapons. On paper, Dadeless and Longot

solved the biggest problem with Project

Orion, whilst retaining most, if not

all, of the performance. Unfortunately,

both projects suffered from the same

problem. Unlike Orion, which was largely

buildable with 60s technology, this new

kind of pulse propulsion depended on

controlled nuclear fusion, something we

hadn't figured out yet. In fact, almost

half a century later, we still haven't

figured it out. There have been several

other attempts to build Orionlike ships

over the years since Dadeless and

Longot, but all failed for the same two

reasons. Either they required

inconventionally illegal nuclear

explosions or they relied on technology

we simply don't have yet.

These days, nuclear pulse propulsion

remains a viable consideration for

future deep space exploration. But it's

no longer the only game in town, and

most modern research is focused on less

controversial alternatives. Things like

ion and plasma drives, nuclear thermal

engines, and light sails.

These kinds of technologies dominate

modern space research. But amazingly,

none of them can match Orion's raw

performance. No iron, plasma, or nuclear

thermal engine is capable of crossing

the vast distances between the stars in

the space of a human lifetime. Not even

close. They do, however, come with a

crucial and obvious advantage. They

don't require the detonation of

thousands of nuclear bombs to leave

Earth.

For that reason alone, Orion is likely

to remain a truly fascinating footnote

in the history of space travel. A

sliding doors moment that had things

played out a little differently, could

have seen humanity venture out towards

the stars much earlier than even the

most optimistic sci-fi writer could have

predicted. And hey, it can't hurt to

have a literal nuclear option in our

back pockets just in case. Thanks for

watching.