Ares vs DIRECT

Ross B Tierney wrote:
:
:The data is ambiguous at best on this issue. SRB's are simpler and
:tend to work incredibly reliably - but tend to have very nasty failure
:modes.
:
:Liquid engines are more challenging to make work reliably all the time,
:with an expected LOM failure probability approximately 5.33 times
:greater than that of SRB's [Source: Space Shuttle Program internal risk
:comparison study between single Shuttle 4-segment RSRB vs. single
:Block-II Space Shuttle Main Engine (SSME)].
:
:In contrast however, liquid engines generally have more benign failures
when was the last time we saw a catastrophic turbo-pump or combustion
:chamber failure on a mature cryo engine?) and are usually able to be
:shut-down and have the added advantage of typically also offering
:throttle control too.
:
:
:I feel that these factors largely balance each other. That convinces
:me that the engines must be assessed on a case-by-case basis and
:generalities are only going to result in mis-leading assumptions - which
:is something we must actively avoid doing in any human space flight
rogram. So:-
:

I'm not convinced they do. What are the odds of a failure mode that
causes loss of vehicle (as opposed to mission failure)?

There's also the issue of the much rougher ride that solids give. Much
higher vibration environment, from what I understand.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw