[X] My Assistant

[Chmee]

I am no rocket scientist, but it seems to me that the cheapest way to space for unmanned missions would be to use rockets with solid fuel and not liquid. Solid rockets are much, much simpler than liquid rockets since they have virtually no moving parts (no pumps, engines, etc). It has been my experience that the simpler the design, the fewer potential points, and thus opportunities, for failure.

This simplicity also translates into a much easier assembly process, and thus lower cost. So why don't we use some modified Shuttle SRB's to get into orbit?

I know that that solid rockets have some "drawbacks", in that they cannot be throttled nor turned off once lit. But how many (unmanned) launches have we seen that needed the thrust to be cut? If the rocket went off course, they are blown up immediately, regardless what kind of fuel is in them.

I believe that solid fuel is not as efficient as liquid (at least does not have a high ISP). However, if it is 4 times cheaper to assemble a solid rocket vs. a liquid, the higher fuel requirement should not be a big deal; just make the rocket a bit larger and it will still be much cheaper.

Are there other issues that I did not list that would make using solids not desirable? If there are no other issues, why isn't the space industry using them now for cheap access?