Smart, dedicated, competent, polyglot, and more; Samantha Cristoforetti seems to have been invented for a "Star Trek" episode. She is shown here at the International Space Station, where she is staying at the moment of publication of this post. Cristoforetti may not be the last astronaut to orbit the earth, but it is possible that the end of what was once called "the space age" will not be far away in the future. (image credit: ESA/NASA)
As you see, the number of people sent to space peaked in the 1990s, following a cycle that can be fitted reasonably well using a bell-shaped curve (a Gaussian, in this case). We have not yet arrived to the end of space travel, but the number of people traveling to space is going down. With the international space station set to be retired in 2020, it may be that the "space age" is destined to come to an end in a non remote future.
The shape of the cycle can be seen as a "Hubbert curve." This curve typically describes the exploitation of a non-renewable resource; fossil fuels in particular, but it also describes how economic activities are affected by a diminishing availability of resources. In this case, the shape of the curve suggests that we are gradually running out of the surplus resources needed to send humans into space. In a sense, the economics of human spaceflight are like those of the great pyramids of Egypt. These pyramids were expensive and required considerable surplus resources to be built. When the surplus disappeared, no more were built. The shape of the pyramid building curve was, again, Hubbert-like.
This result is not surprising, considering that we are reaching the planetary limits to growth. In part, we are reacting to the diminishing availability of resources by replacing humans with less expensive robots, but sending robots to space is not the same as the "conquest of space" was once conceived. Besides, the decline of space exploration is evident also from other data, see for instance this plot showing the budget available to NASA (from "Starts with a Bang").Note how the peak in human spaceflights coincides with the peak in the resources destined to space exploration.
If space exploration is directly related to the availability of resources, it is also true that, from the beginning, it was not meant to be just a resource drain. The idea of the conquest of space involved overcoming the limits of the earth's ecosphere and accessing the resources of the whole solar system. Some of the concepts developed in this area were thought explicitly as ways to avoid the dire scenarios laid out in the 1972 study, "The Limits to Growth." Proposals involved placing giant habitats at the Lagrange libration points, where no energy was necessary to keep them there. The idea gained some traction in the 1970s and, in the figure, you see an impression of one of those habitats - the "Bernal Sphere."(image credit: NASA)
Today, we can't look at these old drawings without shaking our heads and wondering how anyone could take them seriously. Yet, these ideas were not impossible in themselves and, in the 1970s, we still had sufficient resources to make it possible some kind of human expansion into space, even though not on the grand scale that some people were proposing. But we missed that occasion and we much preferred to invest our surplus in military toys. Today, we can't even dream of colonizing space anymore.
The space age is not completely over, yet, but it is becoming more and more difficult to sustain the costs of it. Right now, the Russians are still willing to launch to orbit West European astronauts. But how long will they continue to do so while Western Europe is enacting sanctions devised to cripple the Russian economy? Samantha Cristoforetti, brave and competent Italian astronaut, may well be a member of the last patrol of humans orbiting around the earth for a long time to come.
Note added after publication: This post generated several interesting comments. It is clear that our interest in space has not faded: we are still going to space and we still think that there is a future there. However, it is also clear that we need to cut corners in whatever we do and the "conquest of space" as it was envisioned in the 1950s and 1960s is today completely beyond our means. Surely we can send robots up there, but the conquest of space means to go there and stay there, as human beings, but for that we missed the (space) boat.
There still remains a big question mark about what what role will have space in our future. Will we decline so sharply that we'll have to abandon all space exploration? It may well be and, in this case, the curve will "look Senecan", indeed. Or, we may be able to maintain a certain level of activity, up there. And it might even expand, pick up momentum, and become something that moves by itself.
Space has some peculiar characteristics as an environment, for one thing, it can be seen as the opposite of the earth's environment in terms or relative availability of energy and resources. The earth's surface is rich in mineral resources, but relatively poor in energy sources. Space is rich in energy resources, but poor in terms of mineral resources. Decades of studies about the "self replicating lunar factory" have built up a lot of knowledge on how a self sustaining metabolic system could be built in space to harness the available energy and resources. But it is very difficult and space enthusiasts have a tendency of launching (almost literally) themselves in wild speculations which, then, leave the details unwritten. Think of the "Dyson sphere", for instance. Beautiful concept, but how do exactly dismantle Jupiter and turn it into a solid sphere that surrounds the sun.... ? Still, space is part of our world view and it will remain there for quite a while.
Then, I thought I could also mention the debate on the "Lunar Landing Hoax" which, apparently, keeps flaring up, and did so also in relation to the present post on the "doomstead diner". On this point, I am absolutely sure: even Samantha Cristoforetti is a hoax and I have solid proof of this. See the image below. She is not a real human being; she is just a cartoon character created by Walt Disney Studios! (source)