"The following opinion was provided in a letter to the editor of a national aeronautics magazine: “Manned space flight is costly and dangerous. Moreover, the recent success of a series of unmanned space probes and satellites has demonstrated that a grea

The argument makes a few basic faulty assumptions that call its logic into question.

Firstly, the author assumes that all & every type of information that can be obtained through a manned space flight can be obtained through an unmanned space flight. This may or may not be true, and the author should have ascertained whether the extra advantages offered by a manned space flight - in the form of sentient & independently thinking astronauts aboard - can be exactly replicated by unmanned space missions which are controlled by operators based on Earth or rudimentary artificial intelligences and hence suffer from an inherent limitation to completely sense their surroundings. Perhaps the extra costs involved in a manned space flight are justified by the extra, & possibly more detailed, data obtained.

Secondly, while stating "the recent success of a series of unmanned space probes and satellites", the author assumes that this is the case for all unmanned space ventures in recent history. Before declaring the greater success rate of unmanned space flight compared to manned space missions based on only the records of a recent series of unmanned space missions, the author should have ascertained the success rate of unmanned space flight as a whole. This would have increased the accuracy of his argument.

Thirdly, the author assumes that in proportion to the growth of technology that makes unmanned space flight possible, there will not be a corresponding rise in technology & hence, safety levels, of manned space flight. Such a corresponding rise would not only increase the efficiency of manned space flight, but also make it much safer for the human astronauts involved. If such a case does turn out to be true, then the basis of the author's argument would turn out to be faulty.

Finally, the author assumes that the level of technology required for widespread unmanned space flight currently exists. As of now, we can say that the number of unmanned space missions is less than manned space missions. For unmanned space flight to completely replace manned space flight & establish a monopoly, it would have to be extremely efficient & foolproof. Instead of ascertaining whether the level of technology required to implement this actually exists, the author just assumes that it does.

Thus in conclusion, as demonstrated in the points above, the author makes a few faulty assumptions & fails to account for some unexpected situations that adversely affect the impact of his argument.