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 great deal

The argument with recommendation that the government should invest resources in unmanned space flight is rather weak. It is based on the premises that manned space flight is expansive and full of danger, and that there are some success of unmanned space crafts which corroborate a great deal of information can be got without the costs and risks of manned space flight. However, there are many hidden assumptions needed to be explained, as explicated in the following paragraphs.

First, the assumption that the unmanned space flight is not expensive ought to be demonstrated, regarding to the fact that adopting unmanned space flight is less costly than using manned space flight. It is assumed in the argument without explicitly statement. If it is true, as implied in the argument, then the conclusion can be fortified. On the other hand, if the assumptions proved to be false, that is, the unmanned space flight somehow, maybe because of the expenses of novel technology, costs very high, then the final recommendation is worth doubt, worsening the concreteness of the argument.

Furthermore, providing the above assumption is proved to be true, the assumption that the unmanned spaces devices are stable enough to accomplish the observation and gathering information has to be certified, regarding to the claimed that there are some success in the unmanned space technology. The assumption, if proved to be true, can surely strengthen the argument, for the essential requirement of usefulness lies in the stability. On the contrary, if the success is just minute comparing to the claim, then there must be many practical problems which many overshadow the usefulness of the technology, leaving the argument invalid.

In addition, with the help of testimony of the previous two assumptions, the assumption that the unmanned spaces devices are good enough that they can do the same jobs as those manned space flight capable of still should be testified, regarding to the claim that the a great deal of useful information can be gathered. To replace manned devices with unmanned devices, the questions usually being asked is whether they are able to do the fine, exact, graceful jobs as manned ones are. If the assumption is verified, then the possibility of adopting the proposals is high. On the other hand, if it is false, then the recommendation may be fake, i.e. the experts in government need to contemplate it for a long time.

In the end, the argument is rather weak. However, if the above assumptions are demonstrated, it will be greatly reinforced. Therefore, it is hard to simply accept it. Leave the recommendation until further evidences come out.