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  • Writer's pictureMatt Russell

#237 - The Expanse

Julio and Matt discuss the science and the politics of The Expanse. We talk about the Epstein drive, The Juice, Belters DNA, Artificial Gravity and lots more including a bizarre deal with mosquitoes and discovering the origins of little green men.

“I thought if you told people facts, they'd draw their conclusions, and because the facts were true, the conclusions mostly would be too. But we don't run on facts. We run on stories about things. About people.”

James S.A. Corey, Babylon's Ashes


Congratulations to China!!!

Becoming the second nation to successfully land a robot on Mars that continues to function (Russia, Britain and Europe have all come agonisingly close)

On 24 April CNSA formally announced that the rover is to be named Zhurong after a Chinese mytho-historical figure usually associated with fire and light

."ignite the fire of interstellar exploration in China and to symbolize the Chinese people's determination to explore the stars and to uncover unknowns in the universe”

At 23:18 UTC, on 14 May 2021, the Tianwen-1 lander successfully landed in the preselected landing area in the southern part of the Mars Utopia Planitia

The landing phase began with the release of the protective capsule containing the lander/rover. The capsule made an atmospheric entry followed by a descent phase under parachute, after which the lander used retro-propulsion to soft-land on Mars

Lander may deploy the rover Zhurong on 22 May 2021.

The rover is designed to explore the surface for 90 sols; its height is about 1.85 m (6.1 ft) and it has a mass of about 240 kg (530 lb). After the planned rover deployment, the orbiter would serve as a telecommunications relay for the rover while continuing to conduct its own orbital observations of Mars.

Chinese President Xi Jinping stated in response to the landing, "You were brave enough for the challenge, pursued excellence and placed our country in the advanced ranks of planetary exploration. Your outstanding achievement will forever be etched in the memories of the motherland and the people."


Science of Expanse.

Often our path into space is described by fiction writers first, we spoke at great length in our mars episodes about how sci-fi shaped our thinking and plans to conquer the solar system and then deeper space. From Jules Verne and his fantastical journey to the moon and Von Braun vision of getting Mars, more recently we’ve seen cyclers on Stowaway and potato growing on the Martian both take a stab at what things might be like soon.

What about the slightly further out future, not the super far-out future of Star Trek, or the completely separate timeline of Star Wars, but the future set out in books like The Expanse, Red Mars etc..

The Expanse has become an incredibly popular series of books and TV, lauded by many as a hard sci-fi classic so we thought we’d take a look this week and see if we can unpick what the Expanse might tell us about how close or how far away we are from this technological dream?

So the problem is The expanse shows us how we could be living in the solar system, and it makes it all look really feasible, but if the technologies don’t exist ...they might not ever exist are we kidding ourselves?. Do we allow sci-fi to slightly skew realistic expectations of solar system exploration?

Propulsion and Orbital Mechanics

So, as we keep banging on in the podcast over the years, something that when you talk about space week in week out, you realise that space travel is hard, the tyranny of the rocket equation almost completely traps us to the earth’s surface (as this week electron failure can testify). As far as we’ve managed so far the only way to move forward when you don’t have something to push against is to throw mass out the back and utilise newtons laws of motion. This means you have to carry a lot of stuff to chuck out the back. This means you have to carry a lot of stuff to carry that lot of stuff, the tyrannical rocket equation means a rocket, like Saturn V, weighs about 3000 tons on the launch pad just to get 50 tons to the moon!!! That is barely 1.5% of the original mass. If the earth was much bigger, the technology just wouldn’t work. For some 10g super-Earths you have to start using up a pretty sizeable fraction of the mass of the planet to get off the planet using chemical propulsion.

So does Expanse use the science fiction trope of conveniently forgetting about the rocket equation?

Well yes, sort of.

Travel between the vast distances between planets of the solar system has been made possible with the "Epstein drive". But we don’t have any superluminal travel or travel to other star systems until the introduction of the strange alien technology.

Of course Scott Manley:The Rocket Science of 'The Expanse' does a great job breaking down the “science of the Epstein Drive” but we’ll try to make it simple here.

The Epstein Drive

The Epstein Drive is a modified Fusion Drive invented by Solomon Epstein, who dies when he discovers the process as his test ship is hurled at 7g for 37 hours until it runs out of fuel and is going 5% the speed of light. ...whoops

Tech: Well a basic rundown of the number shows that chemicals just couldn’t release this amount of energy no matter what so really the only way the Epstein drive can work is through nuclear fusion.

We are shown a pellet-like system failing in one episode when the ring is interfering with physics, so potentially this is pellets of Helium 3 in inertial confinement nuclear fusion (essentially a tiny star or hydrogen bomb). That explosion can be directed out of a nozzle (like a torch) using complex electrical fields to guide it all in one direction. This is why people suggest Helium 3 because all the products are charged particles. Of course, they aren’t though. The problem is the energy required for the exhaust velocity is insane as in totally bonkers and we just don’t know how to efficiently point that energy all out the exhaust even if a fraction of it is going somewhere else it’s bad news.

Basically, to get the exhaust velocity for a 100 tonne fully fuelled vehicle it would require 35 TW of energy, the UK requires about 0.0035 TW!!! 3 orders of magnitude less!!! If a small fraction of that gets back into the spacecraft the spacecraft would have to absorb many MWs of energy per KG of spacecraft, which essentially would vaporise any known material.

Think about a car engine, most of the energy is making its way into creating forward motion, but it’s pretty much inevitable that there are inefficiencies and when you have insane energies even with tiny inefficiencies you are still left with insane waste energy, either smashing materials and DNA to bits (neutrons) or heating stuff up to vaporizing temperatures, Xrays etc. This really is the bottom line here, fast rockets are by definition bright torches and profoundly dangerous weapons if they malfunction or are even used maliciously.

If we are only able to get fast rockets using newtons laws of motion and essentially using reaction mass, the energies required will always be a huge problem. Convenience for storyline 10/10 actual likelihood in the next 300 years 1/10

Physiological Adaption

Expanse has realised that these powerful Epstein Drives would result in incredible g forces as they accelerate and decelerate the spacecraft. This is basically not survivable by humans, so they have a special magic injection “the juice” to stop them from dying.

Why do pilots flying fighter jets faint?! That's because of the G forces they are exposed to, in Acceleration and Quick turns

The G forces can place great strain on the body, mostly because your body weight can increase several times. That makes the blood flow to other parts that are not the brain and force the heart to try and compensate.

So in theory to handle the G forces you got two approaches:

A suit that can actually expel the G forces beyond what is desirable off the body

  • It's possible to some extent: the flight suits that fighter pilots wear squeeze their bodies hydraulically to offset g. You just fairly quickly hit limitations from the fact the body does not have a uniform density. In particular, the lungs need to stay full of air, which is very light. (There are liquid breathing systems that have been tested on animals, but even if they’re refined enough for people, the current fluid is much heavier than you want, giving the opposite problem.)

  • Gels could be used, but it’s all very bulky..

We have amphetamines, we have blood pressure drugs, we have anti-emetics(vomiting), but what about vascular reinforcement drugs?. Also, the crash couches need to accurately find viable veins over and over, in multiple bodily locations at once, without infection or wound treatment.

So this liquid injected into the bloodstream would combine with the blood and flesh in the body, saturating every part in our body with oxygen and specific enzymes. That should prevent any blackouts. high g for extended periods of time will have a high risk of stroke, and it's no different in the Expanse. Most burns are done under 4g even in combat situations to limit this risk, and they only go for crazy 8-10g burns if the alternative is being hit by a torpedo. They show characters making this choice ...and some dying as a result.

Humans evolve to adapt to various environments, like the Belters!!!

An entire underclass of humans called the “Belters,” with their own dialect have been growing up in low gravity and has created physiology that marks them as different from those who grew up Earth, with Earth’s gravity.

  • They are much taller and thinner

  • Must take medications for their bones to grow properly.

  • There is a constant need for resistance exercise to maintain muscle mass, especially for anyone who intends to try to go planetside.

  • Many Belters are unable to go to the surface of a planet after living their entire lives in low gravity.

  • Some Belters argue that these changes mean that they have branched off to become an entirely new human subspecies.

How feasible is this though would humans evolve?

Evolve by natural selection? How?

Although genes to help deal with radiation and low gravity aren’t impossible, humans would eventually evolve these adaptations. Evolution is a very slow process and won’t help us with certain things in the Belt. Natural selection essentially needs an environment that kills the weak but lets the strong survive. Likely without technological intervention living in the belt is 100 per cent fatal to everyone. But also we live in a society that doesn’t allow much for evolution, we don’t just watch people get picked off by natural selection and breed the survivors, something human civilisation probably left behind 1000s of years ago.

Interestingly there could be, epigenetics changes, heritable phenotype changes that do not involve alterations in the DNA sequence. The Greek prefix epi- in epigenetics implies features that are "on top of" or "in addition to" the traditional genetic basis for inheritance. These genes essentially switch on and can stay switched on to the next generation, so perhaps that is what is going on with the Belters? Researchers have found that spaceflight seems to switch on the expression of genes that deal with inflammation, help regulate fluids, and repair cell damage.

So the belter-child would still have the same genes as one conceived on Earth, but if it grew up in space, those genes would likely express themselves differently than they would on Earth. The belter-kid would be different from an Earth-kid, but not genetically different, just epigenetically different. One wonders how many generations epigenetic changes would take to become changes in DNA?. Can epigenetic changes be permanent? It looks like if you remove the environmental pressure, the epigenetic marks will eventually fade, and the DNA code will--over time--begin to revert to its original programming

Environmentally induced phenotypes can in this way persist for several generations

There have been many advances in Crispr technology, MIT and UCSF researchers create CRISPR 'on-off switch' that controls gene expression without changing DNA. this is a massive breakthrough. Obviously, it’s hard to change a human body into all the deep tissues, but maybe feteus? But research over the next few years with this technique I think will be hugely important for long term space habitations.

CRISPR is the relics of DNA sequences found in the genomes of prokaryotic organisms such as bacteria and archaea, derived from DNA fragments of bacteriophages (virus) that had previously infected the prokaryote. In other words the biological warfare of Virus v Bacteria has raged for billions of years, They are used to detect and destroy DNA from similar bacteriophages during subsequent infections. Diagram of the CRISPR prokaryotic antiviral defense mechanism, Cas9 (or "CRISPR-associated protein 9") is an enzyme that uses CRISPR sequences as a guide to recognize and cleave specific strands of DNA that are complementary to the CRISPR sequence. Cas9 enzymes together with CRISPR sequences form the basis of a technology known as CRISPR-Cas9 that can be used to edit genes within organisms. The development of the CRISPR-Cas9 genome editing technique was recognized by the Nobel Prize in Chemistry in 2020 which was awarded to Emmanuelle Charpentier and Jennifer Doudna

The industrialisation of the Solar system

The show adds the sophistication of it being in space, but it has for sure parallels with our world, the Earth (centrally governed by the UN, yeah right) is Europe or “The old world” that wants to keep the colonies under control for its benefit. Mars being the young nation or workaholics that turns hyper militaristics (Of course this is the USA) and the colonies inhabited by the belters that could be Africa or Latin America (the Belters have a thick Afrikaans accent).

Artificial Gravity

Thanks to engines that are so efficient that can provide constant acceleration and flip and burn manoeuvres

Also some habitats like asteroids occupied by the belters (Eros/Ceres) have been “spun up” to provide artificial gravity (this leads to real state being more valuable close to the “skin” of the asteroid and the gravity is better there than closer to the center, poor belters growing up close to the center of the asteroid/habitat suffer development issues for it.

Finally, there is one notable “generation” ship on the books, the Nauvoo / Behemot / Medina Station. Originally commissioned by the mormons, this massive spaceship can spin its habitat and provide artificial gravity to its passengers.


Space war will look more like naval war than air combat , and The Expanse books gets it. Evasion has to deal with mass (and the high Gs already discussed), the use of railguns. Even the use of asteroids to attack Earth.


The big project for the martians, not that advanced in the show and becomes obsolete once new inhabitable worlds can be accessed, triggering an identity conflict for the Martians.

Politics of settlements

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