Isn it true that rocket engines are inherently dangerous and so rocket vehicles can never be as reliable and safe as airliners?
There is no inherent reason that rocket engines cannot eventually become as reliable and safe as turbojets. It was initially believed that turbojets were inherently dangerous: large rotating pieces of machinery, temperatures in the combustors above the melting point of metal, operation in uncontrolled environments, millions of moving parts, etc. Yet, today turbo equipment runs safely for hundreds of thousands of hours with just routine maintenance. Many rocket engines actually have fewer moving parts than turbojets and, unlike the latter, only need to perform for a few minutes per flight. Rocket engines simply have not yet flown enough to develop the levels of reliability for which they are capable. To save costs since they only need to be used once, the engines on expendable rocket vehicles have narrow safety margins. The economics of the suborbital RLV business, on the other hand, depends heavily on robust and reliable engines and so developing such engines is a top priority. Since t
