If you prefer to listen rather than read, this blog is available as a podcast here. Or if you want to listen to just this post:
Knowing that the 50th anniversary of the first Moon landing was this month, I felt a strong compulsion to say something about it, but what exactly? There is definitely no shortage of commentary related to the occasion. Obviously the most interesting part of the anniversary is the fact that we haven’t been back since the end of the Apollo Program, nearly 47 years ago. Perhaps I should wait and say something when the 50th anniversary of the last man on the moon rolls around. (Does anyone think we’ll make it back before then?) But I’m definitely not the only one to have noticed this distressing fact, most of the commentary surrounding the anniversary mentions the fact that we haven’t been back. What can I say on this occasion that would be unique?
I do think there’s something interesting to be said about the connection between space travel and human salvation, but I’ve already covered that connection and however unique that observation is, I don’t want to just rehash what I’ve said previously. So what can I bring to the table that isn’t being served in dozens of different locations by hundreds of other commenters? Well, as I survey the commentary I think there’s a definite dearth of extrapolations. Sure, humans will probably make it back to the moon. (I assume that if no one else gets around to it China will, at least, if only for reasons of national prestige.) But if we extrapolate things out and look at the trends, when are we likely to be there permanently, and what about Mars? And, perhaps most important of all, if current trends continue when would humans actually leave the solar system? Obviously this exercise will produce only the crudest of numbers, but I expect that whatever comes out will be pretty depressing even if I end up off by a factor of 2 or more.
To start, though, for those who never read or can’t recall my post on the connection between space travel and salvation, and who don’t have the time or inclination to go back and read it, I should briefly explain my point, which is: If you want to ensure that humanity continues for as long as possible, and you don’t believe there’s any external force capable of helping with that (religion, aliens, vaguer forms of spirituality, etc.) then, ultimately, this is going to require getting off the planet in a sustainable and ongoing fashion. In that post, I further pointed out that most of the large scale goals we’re pursuing at any given moment have very little to do with this endeavor and in fact work against achieving it, if for no other reason than opportunity cost.
It’s upon considering this last point that branching off into an extrapolation of trends starts to look like an important next step. Yes, occasionally when a technology becomes available, things can change dramatically, and trends before this change become meaningless, a great example of this is the internet. But in the case of space travel we’ve had all the relevant technology for at least 50 years (and yes, I’m aware of the EMDrive) but yet so far there’s been no dramatic upward spike in space travel, particularly if we view the Apollo Program as an outlier (as I am inclined to do, see my post about S-Curves). Accordingly if our salvation depends on getting off the planet, and we have 50 or more years of data on the rate at which that’s actually happening, and every expectation that this rate is unlikely to change very much, then, it would definitely appear to be worthwhile to extrapolate out these rates and see where they get us.
None of this is to say that the rate of space exploration and colonization isn’t increasing in an exponential fashion. In fact, for all of my trend extrapolation, I’m going to assume that there’s some underlying law along the lines of Moore’s Law, where a given quantity doubles every X years. Meaning that we merely have to decide what a reasonable rate of doubling would be, using the last 50 years worth of data. I’m not actually saying that there is a parallel to Moore’s Law when talking about space, I’m more saying that there had better be, because the distances from one destination to the next are already exponential. Meaning that we’d better hope things are growing exponentially because otherwise space colonization is definitely doomed. Also something that doubles every two years is going to already assume significant ongoing technological advancements. Meaning that if you do think something like fusion or the EMDrive is going to come along and drastically change things, those advances are probably already built in to the model
For our first example, let’s start off by making the hugely optimistic assumption that the current trend is for the distance humans are capable of travelling to and returning from to double every 10 years. And if we then take 1970 and travelling to the Moon as our starting point, we wouldn’t make it to Mars until sometime in the 2040s, Jupiter would be about 2075, Neptune around 2100 and Alpha Centauri would not be reached until the year 2230. And If we, instead, made the more reasonable, but still fairly optimistic assumption that the distance only doubled every 15 years, then we’d get to Mars around 2075, Jupiter would slot in at 2120, Neptune would be 2180 and Alpha Centauri wouldn’t be until sometime around the year 2360…
That last one may not seem especially optimistic, but recall if we’ve decided that space travel is important for our long term salvation it’s not enough to get there once. Surely some nation can massively divert resources for a single moonshot, which is what the word came to mean, and possibly put people on Mars a half dozen times and bring them back, but in order for it to assist with our salvation we have to be able to do it on an ongoing, perpetual basis. And, of course, not only is all of the above optimistic, but based on a single data point: putting a man on the Moon. Not only have we not gotten any farther than that, we haven’t even been able to do it on the ongoing and perpetual basis I’m talking about. But before we leave this example, let’s conduct the exercise one more time, and assume that, as he has predicted, Elon Musk manages to put someone on Mars in 2024 (and by the way here we would appear to be in the realm of the insanely optimistic). This would finally give us a second data point and putting that into the crude model I’m using it would mean a doubling approximately every 7.5 years. Which gets us to Jupiter in 2045, Neptune in 2075 and Alpha Centauri in the year 2165. Not bad, but still a lot slower than most people imagined 50 years ago, and here we touch on one of the problems.
In many respects we’re living in a science fiction world more incredible than anything anyone imagined in 1969, and in other respects, particularly when one looks at space travel, someone reading Heinlein, Clarke or Asimov would be profoundly depressed by how little progress we’ve made. And yet the idea that any day now things will change and suddenly we will be living in that world is hard to shake. Certainly there could always be some dramatic new invention that would change whatever curve we’re currently on, but at the moment there’s good reason to think that, absent some massive space exploration/colonization inflection point in our future, the current rate of plodding along isn’t going to get us anywhere very fast. Now it may be that it doesn’t matter how long it takes, as long as we get there eventually, but a lot can happen between now and even 2024, to say nothing of 2040, 2075 or 2360. Recall that there’s good black swans and bad black swans, and while the former may be exactly the positive inflection point we were hoping for, there are a lot more things which could happen that would make this whole project much more difficult rather than less.
Moving on, what other trends are there that we can extrapolate? Above I talked about something being continuous, and we have had continuous human presence in low earth orbit (with occasional gaps) since 1973 when Skylab was launched and occupied. All of this has occurred at around 250 miles from the surface, but I’ll be generous and round up to 300. With this as our new starting point we can once again imagine this distance doubling every so many years, only this time it gives us the distance from Earth where humans will be able to sustain a continuous presence. If we once again start with, what I feel, is an incredibly optimistic doubling time of 10 years, we will have a continuous human presence on Mars in 2140, Jupiter (or one of its moons) in 2175 and a continuous presence at Alpha Centauri around the year 2300. If we instead assume a more realistic trend of doubling every 15 years, then Mars is 2225, Jupiter is 2280 and Alpha Centauri is not until the year 2500.
Now I understand that certain things might get easier, for example just getting out of the gravity well of the Earth is a major hurdle, and perhaps we should take that into account, but when you’re talking about a continuous presence, I would argue that getting out of the Earth’s gravity well, is perhaps the least of your worries. Also recall that to a certain extent productivity gains are built into the model of exponential growth we’re already using. Finally, these extrapolations are not meant to be especially precise, but rather to illustrate that even using some fairly generous assumptions space colonization is going to be a lot harder than I think most people realize. Particularly given how spectacularly unimpressive our manned efforts have been since the end of Apollo. But, perhaps that’s where I’m going astray, by so far only focusing on manned efforts.
Unmanned exploration really is the easiest way to explore space. And while unmanned probes do not directly accomplish that “salvation of humanity” I keep coming back to, they are at least a reasonable potential stepping stone along the path to that. With that in mind, what kind of Moore’s Law might we extract if we turned our focus to unmanned exploration? Here, at least, we have multiple data points, one for each celestial body, and if you graph it, it looks like a pretty nice exponential curve:
There are a couple of things to note about this data. First given that Uranus and Neptune were both first visited by Voyager 2, I’m not sure if Neptune should count as a separate milestone from Uranus (or perhaps it’s the other way around). Also you’ll notice that I didn’t include Pluto, if I did you’d see that nice exponential curve flatten out into something that looks a lot more like a plateau, since, at the time New Horizons visited it, Pluto wasn’t that much farther out than Neptune and we didn’t get to it until 2015.
Mapping this to our simple model of deciding on a doubling rate is messier with actual data, but after fiddling with it a little bit it looks like seven years fits fairly well. Taking that and anchoring it around Voyager 2, I came up with an arrival time for the first probe to Alpha Centauri of around 2110. Which is almost exactly NASA’s current estimate of a 2113 arrival for the probe they plan to launch in 2069. (You’ll have to take it on faith that I came up with my number before I found the number from NASA). These estimates might be pessimistic, given that Yuri Milner, the Russian billionaire, is proposing to launch a probe by 2036, which might arrive as early as 2056. But when you get into the details of that proposal there’s reason to question whether it should necessarily be placed in the same category with all of the other probes. The probe proposed by Milner’s team weighs only a few grams and would enter the Alpha Centauri system at 20% the speed of light. Which means the probing part is going to end up being some infinitesimal fraction of the entire trip.
Of all these trends, the trend in unmanned probes is the only one that seems a little bit promising, and even there, it’s going to take quite a while to get anywhere we haven’t already been.
Fifty years ago everything seemed so promising. What happened? What happened to the science fiction dreams I grew up on? Instead the best way to describe space exploration over the last 50 years, is vaguely depressing with occasional all to brief glimpses of triumph here and there. And perhaps even worse than that, there is no sign that the future is going to be any better. Instead most of our energy seems focused inward, and the Great Silence of the universe becomes less and less paradoxical.
The harvest is past, the summer is ended, and we are not saved.
Space: the final frontier. These are the writings of a slightly unhinged blogger. His five-year mission: to explore strange new topics. To seek out new controversies and new weirdness. To boldly go where no man should ever go period! If you’d like to help with this mission consider donating.