Canned Monkeys Don't Ship Well, the Remix Version

You thought you were rid of me. Sorry, Charlie's still on vacation for a few more days, so here's something that has nothing to do with current politics. Just to be annoying, I'm going to revisit that ever-giving fount of joy, slower than light (STL) interstellar travel. You may think that, because it's not physically impossible, that it's inevitable that humans will travel this way one day. Sadly, it looks like blasting your way between the stars the hard way requires magical technology too, just as FTL does.

We've talked about this before on the blog, but unfortunately, the really good conversation was about 800 comments in and about 8 (?) years ago, so you can't just google it. Here, I'm going to cover two points: why canned monkeys don't ship well, and what the precursors to STL would look like, so that we'll know if our society ever starts preparing itself to expand into space at less than the speed of light.

"Canned monkeys don't ship well" refers to the problem of keeping people alive in interplanetary or interstellar space (this for the two people who didn't know it already). There are a lot of problems, what with providing air, water, food, radiation protection, decent meteor defenses, a working clothes cleaner, producing food reliably, recycling trash, keeping people healthy and able to step onto a planet again, and last but not least, completing a human life cycle from conception through birth to maturity and senescence. Many of these are provided by Earth, and the rest require more space than anyone currently has on the International Space Station (ISS). That's why, for instance, they don't have a clothes washer on the ISS. They wear their clothes for a week or so depending on what it is, and throw them out. More insidious problems have to do with what the lack of gravity does to the health of humans, plants, and animals. Correct me if I'm wrong, but I don't think any plant or animal has successfully completed a life cycle (seed to seed or animal to animal) entirely in freefall. And, if you read Chris Hadfield's An Astronauts Guide to Life on Earth, he's quite candid about how extendedly unpleasant it was to reacclimatize to Earth after spending a year in space. It wasn't just reflexes--his feet couldn't tolerate the weight on them, he had rashes and all sorts of weird symptoms that took days to go away, and weakened bones that took at least a year to go away. It's uncomfortable to get into freefall, it's painful to get out of freefall after an extended time in it, it's not just humans that have problems, it seems to be most eukaryotes do, and we still need to figure out how to work around this. Magic, obviously. Just wave that wand, and the problems go away. But what exactly is the wand you're waving? CRISPR? Vibrating pants? Some wonderful pharmaceutical suitable for plants, humans, and fish (gravipramine?)?

Fine, you say, my interstellar ark will spin to make up for this problem. And the ship will be huge, so you can have not just your damned washing machine but vast pools of water as radiation shields (as in Anathem). This is great. Heck, we'll even assume that you have steering and propulsion systems that can handle pushing a great sloshing gyroscope in a precise direction for centuries. Yeah, that. It'll be fun to steer your spindizzy when there's a lot of weight moving around inside it. The wobbling thrust to compensate will be fun too, and keeping this coupled set of chaotic oscillators from going out of control will be easy, of course. All we need is a magic navigation system, magic because it doesn't just steer a wobbling gyroscope impeccably, it does it for centuries without error, and with rapid collision avoidance too. Isn't magitech wonderful?

This is where we get into the engineering challenges. I'm certain, for instance, that we can build computers that last 50 or 100 years. After all, the Voyager space probes are still kind of working, 40 years later. Actually, there's a fun little problem here: a few bespoke resilient computers for expensive space probes won't disrupt a consumer electronics market built on planned obsolescence, but what if you're building an effectively immortal (to a first approximation) system? Won't that decimate the local computer industry, when everybody wants a computer that they can pass on to their kids, rather than discarding, just so that a team of engineers can stay employed making replacements? After all, STL voyages last decades to centuries, and the electronics all have to work forever, with only onboard repairs. This is actually be one of the precursors to deep space colonization, that computers stop being made to fall apart, but instead are built simultaneously rugged, long-lived, and easy to repair. Or, of course, we could put an entire computer fabrication facility on every spaceship. I'm sure that won't take much weight. And swapping out the navigation system every few years should be really easy, too.

That's just one subsystem. If we're talking about a century or millennium long voyage (and note that these are optimistic given our current state of propulsive affairs), then to a first approximation, every bit of hardware either has to last the entire trip, or has to be totally repairable using the (recycled?) supplies brought along. Yes, yes, I know, 3-D printing. That will certainly be part of it, but don't you think that there's going to be critical infrastructure that just can't be reprinted ad nauseum, like critical structural elements and parts of the hull? You'll need really good (dare I say magical?) printing capabilities to reprint a big chunk of the ship from inside the ship. You'll also need a really efficient materials recycling facility to sort all the waste materials and efficiently remanufacture all the printer feedstocks. But heck, sorting stuff into pure materials streams and rebuilding it only takes lots of energy, time, know-how, and specialized technology, which is why we don't yet do this with municipal trash. Actually, trash management is another one of those little precursors: if idiot-proof urban recycling becomes a thing, we'll be one small step closer to space.

Then we've got the big noise, the interstellar medium and the fun of ramming into it at high speeds. Raising your kids in the middle of a firing range or next to the containment shell of a nuclear reactor is positively tame in comparison. Interplanetary and interstellar space are astonishingly good vacuums (better than we can readily make on Earth), but they're not empty. Worse, the stuff in space tends to move really, really fast, which means it has a lot of energy. Bullets travel at around 1 km/sec, but meteors travel at 10 km/sec and above, and an STL spaceship needs to get moving much faster than this to make decent time between the stars. Even the best steering system can't get a ship (especially a huge, spinning, sloshing ship) rapidly out of the way of some bit of interstellar debris. No, we need shields, and those shields need to be fixable or replaceable from inside the ship, because humans aren't going to survive very well either out in that shooting gallery. Yes, anti-micrometeorite armor (like Whipple shields) works on a different principle than terrestrial armor and wouldn't stop a bullet, but even it needs to be replaced, and a starship will occasionally run into bullet-sized space junk at ultraballistic speeds. So we need magical armor. And magical radiation shielding too, preferably in the shape of a mobile cowling, so that robots and humans can get outside and work on the starship hull, under cover, and not die rapidly. More magic! Or heck, I'd settle for a force field at this point.

And yes, there's a rocket firing for years to centuries to push the starship up to speed. How long do real world rockets fire for, again? The starship engine is another one of those magical technologies. While yes, ion engines have fired continuously for years (on the Dawn space probe, for example), their thrusts are tiny, equivalent to the weight of a piece or two of paper in your hand. Since space is effectively frictionless, those tiny thrusts add up, but only on relatively light-weight spacecraft, over interplanetary distances, and over a few years. We need extremely high thrust and for centuries, and it's not clear how to get this. The closest we might want to get is an Orion drive powered by hydrogen bombs, but then we've got to store those beasts indefinitely. And I'm sure everyone wants to grow up immediately adjacent to a nuclear test range, protected by some really, really good shielding that will have to be repaired in house, even though it's a wee bit radioactive.

Then, once we get to the new planet, we've got to land on it, repeatedly. So we need landers that can boost themselves back up to orbit, ideally in a single stage. That's easy, we're developing SSTO (single stage to orbit) technology now. Right? Well, the little interesting challenge is that your lander has to be full of fuel to take off again. Indeed, without magic fusion rockets or some such, almost all of the lander's weight when it lands has to be fuel. And it's going to be really hot on landing, as it decelerates from orbital speed (Mach 10+) down to zero. So you're flying the equivalent of an ostrich egg full of rocket fuel, and decelerating it from Mach 10 to zero, landing on a totally unimproved landing spot (so the lander either has to be able to hover or land in the water, take your pick), and then take off from that spot (or the water) again. And if you think the water launch of a supersonic plane is easy, you really should google "XF-2Y Sea Dart." Anyway, making conventional rocket landers more magitech to work. We could use Orion technology to land and take off, but then the lander is going to have to land, erm, quite a long distance from wherever the colony is. That's going to be a bit tedious, especially the part where they have to repair the road after every launch or landing.

Finally, we've got the problem of using the toilet. Yes, I know space toilets have come a long way. Here I'm talking about recycling nutrients, all 17 of them. People have tried living in closed ecosystems since the 1970s, and it's a chore. I saw a description of one DIY experiment that said that the man involved had to produce feces of the correct weight and composition every day, just to feed the recycling system that fed the plants that fed him. If you've got a small, closed ecosystem, shit can't just happen, it has to be excreted in precise amounts and on schedule. Earthly ecosystems are resilient to when poop happens because there are huge surpluses of some nutrients (like nitrogen in the air). This gives us a fair amount of slack in how nutrients get processed. Dead wood can lie around for centuries in the desert without causing all the plants around it to die from lack of carbon. Unfortunately, when you get into a smaller ecosystem, the surplus nutrient pools are smaller. So, if there's too much dead wood around (or unprocessed feces) you really could starve, and if you don't have enough oxygen for the microbes to break down the dead wood, you could suffocate as the microbes got to work recycling your waste. Biosphere 2 ran into problems associated with this. Ideally, you want the starship's biosphere to be as big as possible for stability. Simultaneously you need to minimize its weight and size to make it easier to send to another star system. Magic ecosystem handling? That's the easy solution. The hard solution is making sure that everyone on the ship is more capable of running an ecosystem than are almost all PhD ecologists currently working (that would include me, incidentally).

Speaking of which, the crew: all astronauts, the best of the best, right? Good breeding stock and all? And their grandkids are going to settle the new planet? Well, erm, yeah. There are problems here too. One is that humans don't breed true, so amazingly talented people tend to have less talented kids; it's called regression to the mean. In a multigenerational setting, you have to allow for incredibly talented initial crew getting old, becoming incompetent, and passing off their responsibilities to their less-talented offspring. That's tricky. You also have to allow for people being incapacitated, whether they are young, old, pregnant, sick, or drunk. Yes, drunk. One of my proposals for dealing with the shortcomings of a closed ecosystem was to designate 10% of the grain crop to making beer, so that people could get drunk occasionally. The point wasn't that alcoholism was good, it's that if your nutrient cycling is so tight that you can't afford the surplus crop needed for an occasional party, then you're absolutely incapable of dealing with problems that incapacitate part of the crew, let alone storing surplus food for when it's needed. Having a system that's resilient to people getting drunk occasionally is one way to make sure that your system can also deal with more serious problems. And, if there's a crop failure, the grain that would have gone to alcohol can be used for food.

I could go on, but there are three points that really need to be made instead. One is that STL can involve as much magic technology as FTL. It doesn't involve breaking Einstein, but Einstein's not the only scientific hurdle out there. All sorts of things are permitted by general relativity but physically or logistically impossible.

The second is that our species isn't ready for the stars. We're not magical enough. If we were getting close, the precursors for interstellar technology would already be around, changing our lives. For instance, if we could almost build a starship, it would be possible for an (evil) magnate to build a secret lair that was impenetrable to anything including a nuclear blast (starship shielding). His minions could take shelter in that lair, seal the entrances, and live in there under his dynasty for centuries, with no problem at all (closed ecosystem with indefinite recycling, plus social engineering). Climate change would be a non-issue for the super-rich, because their castles would be proof against anything the climate or outsiders could throw at them. And we'd have the equivalent of the GNP of Russia to literally throw away in making a starship that would send a few hundred people on a one way trip to a nearby star, since that's about the level of resources you'd need for a starship. So yeah, we're not there yet. This isn't to say that you can't write a story using STL, but it would be good if you spread the magic technology more widely than just in your ship. Why should people have starships in space, but only the Whole Earth Catalog planetside? Starship tech makes for great secret bases and mechanized armor, if nothing else. And every character won't be able to just fix a toilet, they'll have the whole system piped through their closet composting and growth chamber to feed them a treat a few weeks later. In an STL enabled world, proving you can take care of your own crap should be a rite of passage akin to getting a driver's license today.

The final point is one that I'm sure is well-known to SF cognoscenti: there's a reason so many SF writers have used FTL, gravity control, reactionless drives, and force fields. They make things easy. Instead of getting into the aeroponic weeds about how everybody must cycle their nutrients through the system for centuries, you just wave at least two of those magic wands and all of the difficult STL technical challenges go away. You can speed from star to star before your life support runs out, land on planets and take off as many times as you want, and interplanetary and interstellar meteors won't kill you, because you're not about to run into them at high speed without proper shielding. They're not stupid tropes, just overexposed because they're so gosh darned useful. I may be wrong, but I believe that the SF writers who originally proposed this tetrad knew enough about science and engineering to have a good idea of the problems they were avoiding by using them. Sadly, we've since discovered that the problems were even worse than they originally thought. Perhaps later generations of SF aficionados have forgotten and need to be reminded?

What did I miss? Heat, did you say? Power plants? Shipping corpsicles and thawing on arrival? Put 'em in the comments.