Based on The Expanse TV series I wonder how people should build their ships to avoid spreading of highly contagious lifeform.

Protomolecule's features:

  • infectious agent with extra-terrestrial origins
  • set of free-floating instructions designed to adapt to and guide other replicating systems
  • it is able to maintain its primary structure in a wide variety of conditions, and it has an affinity for carbon and silicon structures, but is anaerobic
  • it can use ionizing radiation as an energy source, and its growth can speed up considerably if exposed to high doses
  • human-hybrid was a powerful and durable entity that could survive in hard vacuum, move at great speeds, and tear through hull plating and armored targets using its bare hands

Now of course human can use nuclear weapons and destroy entire ship or take course toward the Sun.

Human technology level is pretty low(allow to travel within Solar System) so forget about:

  • FTL
  • energy shield
  • teleportation

I wonder how to design ship that can survive contact with "Protomolecule" without scuttling the entire ship and escape with lifepods.

  • 3
    $\begingroup$ what do you mean "free floating instructions" and "affinity for carbon and silicon structures"? Does it have a corporeal form, do the instructions float with out a medium? $\endgroup$ Commented Mar 1, 2016 at 21:08
  • $\begingroup$ Have you exhausted the methods used today to prevent biological contamination? Sterilization sounds much easier than what you have in mind, and yet even there we accept some level of contamination which may not be acceptable for such a troublesome material. You may need more advanced technology than you are admitting for the question $\endgroup$
    – Cort Ammon
    Commented Mar 1, 2016 at 21:34
  • 1
    $\begingroup$ free floating instructions doesn't make sense. How do you protect against handwaving plot devices? $\endgroup$
    – JDługosz
    Commented Mar 5, 2016 at 13:34
  • $\begingroup$ OP are you trying to protect the inside or the outside of the ship? $\endgroup$
    – ozone
    Commented Mar 5, 2016 at 16:53
  • $\begingroup$ Is anti-gravity off limits? I'd assume people would have found a way to not get crushed by extreme accelerations... $\endgroup$
    – Martin_xs6
    Commented Mar 9, 2016 at 18:19

5 Answers 5


First things first: you cannot keep the outer part of the spaceship from being contaminated.

This settled, let us focus on the inside parts of the spaceship. We are dealing with a highly adaptable, highly resistant life form which cannot be killed with powerful e.m. radiation. This life form is also known to have an affinity for carbon and silicon based structures.

In order to contain such a life form, we would set up chemical traps. We would use a paint which contains buckminsterfullerine (bucky balls) and graphite particles mixed with some silicon impurity. The amount of carbon and silicon in the paint increases as we go from the outer parts of the spaceship to inwards.

The effect would be that the life form would follow the chemical trail and seek more carbon-silicon rich regions. In the innermost regions of our spaceship, we would have a containment facility where biochemical receptors would be used to sense the presence of this life form. On receiving positive signals, the blast doors would shut, trapping the life form inside. Now you would use an extremely corrosive acid in vapor form to completely annihilate all traces of the life form and convert it into chemical goo.

So the basic plan goes like this => use chemical signatures to lure this life form to where we want it to go. => once there, trap it inside and use extremely corrosive compounds (or maybe high temperatures, or a mixture of the two) to kill/neutralize it.


Your question is built upon the premise that such a protomolecule could actually exist. However, that premise is not well founded.

infectious agent with extra-terrestrial origins

Our bodies are designed to detect and eliminate anything foreign, and they do it pretty well. On Earth viruses and bacteria have adapted alongside other life in order to still be able to affect them, but this requires them to make special adaptations. The result of this is that viruses are not universal - dogs can't catch the flu from a human, for example. This makes it very unrealistic that an extra-terrestrial molecule could infect a human.

set of free-floating instructions designed to adapt to and guide other replicating systems

Again, viruses have to be adapted to specific hosts. Also, for your body to actually be vulnerable to "free-floating instructions", it would have to be DNA. DNA is only moderately stable, and would fall apart quickly in space.

It also wouldn't have time to "adapt to" anything else before it was eliminated - unless it's an intelligent system (much larger than simply a molecule) the only adaptation it can do is through evolution, which requires far more time than our bodies would take to eliminate the foreign molecule.

it can use ionizing radiation as an energy source, and its growth can speed up considerably if exposed to high doses

DNA is quite vulnerable to ionizing radiation. In order to be immune to ionizing radiation the protomolecule would require significant protection around the instructions, but that would require it to be an actual life form rather than just a protomolecule.

human-hybrid was a powerful and durable entity that could survive in hard vacuum, move at great speeds, and tear through hull plating and armored targets using its bare hands

Yeah, this bit is just pure science fiction.

In short, you've got a made up substance that is not realistic at all. Given that it's made of handwavium, there's no way to tell what could be done to effectively avoid it - there's always a way for handwavium to get around whatever protections you can come up with.

  • $\begingroup$ Actually that only rules out a natural biological life form. The question does not specify it is one and it would obviously be lot more realistic to think it is some sort of self-replicating weapon with swarm intelligence composed of units too small to be visible. $\endgroup$ Commented Mar 1, 2016 at 21:07
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    $\begingroup$ @VilleNiemi so a different question would be how to design a better hard-SF pathogen. $\endgroup$
    – JDługosz
    Commented Mar 5, 2016 at 13:36

Two methods - disrupt its internal structure or exhaust its supply of energy.

No matter what material the Protomolecule is made of it must store information about its form, so when it reproduces or divides the new Protomolecule will know what form to take. It also needs this information to know how to heal when part of its body is destroyed. Humans store it in DNA but binary code or elaborate silicon structures could server the same purpose.

All of these storage methods are based on the physical location of atoms and the chemicals between them. If we rearrange a vast majority of the atoms and their bonds the structure will be broken and the Protomolecule will cease to be alive, just like if we took the same elements and put them in the same configuration we would have a new Protomolecule. This says that anything that breaks the bonds of the Protomolecule will kill it.

So hot fire, plasma, in some forms strong acids and basses, can purify matter, by randomizing it.

Noble gasses won't form chemical bonds, plasma is to hot to from them, so either can be used as a barrier to stop the spread of Protomolecules.

It also takes a great deal of energy to switch forms so we could try to exhaust the Protomolecule by keeping it in a space shielded from ionizing radiation(Xray - gama ray), and exposing it to many weak easy to defeat life forms. Most space ships could be shielded and the Protomolecule could be tricked into bonding with dodo birds for instance which would be easier to defeat. When it runs out of energy the Protomolecule becomes harmless.


Basic biological containment protocols work just fine. Avoid touching the stuff, don't breathe it in, and if anyone becomes infected (given that you know what they can do when the Protomolecule has had a bit of time to work it's magic), burn them. If you have any idea what the protomolecule's 'instructions' are, help it out as much as possible in ways that leave you out of it. It doesn't actually care about you.

Also worth pointing out, though you didn't explicitly note it in your question: It isn't just anaerobic, oxygen is fairly toxic to it until it's got it's claws into another organism. Ramp up the O2 as high as you dare, put everyone in hazmat suits, and don't feed the alien plot device. You'll be fine.

Of course, if you do feed the alien plot device:

Given that with enough biomass the Protomolecule shunted Eros out of orbit by turning off inertia, temporarily terraformed Venus, built a gateway to an alien transport hub, resurrected the pattern of a dead man's brain that it just happened to have in storage in order to try and find it's own 'off' switch, shut down an ancient alien security network, accidentally melted a moon, blew a hole in the side of a planet and was regarded by it's creators with the same level of concern as a wrench...

You're pretty boned.


Chlorine gas decontamination, run the oxygen at the highest safe concentration. The protomolecule outside of a host is so oxygen-sensitive that it can’t even spread by droplet. You have to directly touch a relatively large amount of the liquid to become infected. This makes sense given how complex and delicate it would have to be, and given that it was engineered to be optimized for anaerobic, primitive life.

Really, expanse ships are mostly built up to isolate this anyway. They use some kind of decontamination spray that seems effective enough, and there was only one case where somebody who knew what they were working with managed to spread it onto a ship by accident.


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