Actually, it's been the convention in Indo-European languages for a millennium or so; in fact, the structure of many of these allows for no other choice (Slavic languages, German, French etc.), and many English speakers - if not most - are L2 speakers for which this is the most compatible and the only natural alternative (the "uncanny valley" subproblem of interference in interlanguage fossilization).
Well, thanks for the history lesson, but the fact of the matter is, the use of "he" as the gender neutral pronoun fell out of common usage some time ago. Using it in a modern context or to refer to future events, creates a confusion : are you referring to a known male astronaut? Are you assuming that the astronaut will be male? Or are you (for whatever reason) using a language convention from prior the 1960's? English has always had a gender neutral pronoun (Churchyard et. al.) and therefore the use of the male pronoun to describe a person of undetermined gender was merely the convention for a number of years, until it became common practice and convention to use "they" in the singular, or other constructs.
As a bonus, with the rapidly increasing number of perceived and recognized psychological genders (not the linguistic ones) on the very short timescale of the few recent decades, there's no need to rewrite texts and textbooks (considering that the purpose of written texts is to span not only vast amounts of space but of time as well);
Get over it.
English is evolving, it always has. That's the nature of it, and indeed, one of the primary reasons why it has been so successful. If I read Shakespeare I see many conventions, words and artifacts which initially cause confusion until I read it in the context of the time - the same applies to Austen or Salinger. It has always been this way. Pronouns fall in and out of use: use of 'he' as the gender neutral pronoun is in the latter category.
one could easily argue that "improvements" of limited scope such as your "he or she", while attempting to sound inclusive (for whatever strange reason some people might perceive it that way) are, for example, distinctly interphobic - which, again, would be a social construct with limited longevity compared to the potential timelessness of any written text.
One could argue that, but not logically. The use of "they" as a singular, or "the astronaut" avoids confusion and doesn't require us to assign gender to someone who is not of that gender. It's not too hard: I notice you yourself in your reply referred to a person of undetermined gender (the offended/perceiving party above) in gender neutral terms without any loss of meaning or the need to adopt an awkward structure.
So humans won't be able to repair them, because you're not going to send them, and you're arguing the case for machines repairing themselves is equally bad? So what *is* your proposed solution? The "disposable camera" model? That really doesn't scale very well.
I'm arguing that we are always going to send a machine. The machine(s) will always be the larger part of what we send, whether it be a spacecraft designed to sustain humans for as long as possible in the vacuum of space, landing craft, spacesuits. So the choice is whether we send a human as well as the machine(s). Of this technology stack, the least reliable part is the human. So if we are going to be concerned about repairs, our first thought is - how repairable and reliable is the human? The answer is: Not very. Human bodies degenerate if left in low gravity for any period of time. They react badly to changes in pressure and have a narrow range of operating temperature. They need very specific fuels, which are bulky and cumbersome, and easily contaminated. Humans are social, and perform suboptimally outside of a social setting. They tend to change priorities based on feedback from the amygdala, leading to a lack of mission determinism.
Comparatively speaking, robots are simple, designed for the target environment and therefore very reliable.
On average: in a realistic scenario involving a human and a robot in space it's the human that will need repair, not the robot.
(It is also interesting to observe how the "notoriously unreliable" human body of yours actually deals with some space-related conditions such as moderately intense radiation actually better than the majority of our technology, which is prone to hard errors, and if scaled to the cognitive capacity of the human brain would fare even worse.)
Now i think you are being faintly ridiculous. Space related conditions:
Vacuum: will kill me almost instantly, unless some kind of machine forms a protective vessel around me.
Lack of water: Will kill me within about 5 (earth) days, unless a machine supplies me with water
Lack of food: WIll kill me in under a month, unless a machine supplies it to me, processing. refrigerating and heating it for my consumption
Radiation: Will kill me in 12 months, unless a machine deflects that radiation
Lack of gravity: will kill me in 24 months, no known solution at this stage.
If machines are so unreliable and can't handle the stresses of space how do we get to space at all?