Re: Briefing on SRB based CEV at NPS with Scott Horowitz

George William Herbert wrote:

> But the general form of the accident could repeat,
> if a large chunk of propellant grain breaks off and
> chokes the gas flow somewhere in the casing.
> And is always by the nature of the vehicle a risk
> for any solid (and, any hybrid, though their
> oxidizer injection nature and transient energy
> potential in the casing at any time reduce the
> magnitude of energy release in potential failures
> significantly).
>
>
> -george william herbert
> gherbert@xxxxxxxxx

This statement is objectively true--but it either misses the point or
intentionally muddies the waters when it comes to overall vehicle
reliability and safety. It's akin to the reasoning used to ban
nukes,"solids are dangerous!" like "nuclear power is dangerous!", never
mind the actual reliability numbers.

The fact is that the SRBs so far have a better overall safety record
than any liquid booster available. The fact that large solids are
capable of having explosive failures is uncontested--but also
completely irrelevant unless considered with the reliability numbers.
Liquid boosters are prone to explosive failures, albeit by a different
mechanism. The large number of SRB flights results in reliability
numbers with a statistically small confidence interval compared to a
comparable liquid booster, very few of which have launched often enough
to provide adequate reliability data. Even with large confidence
intervals for liquids, my hunch is that the SRB would still come out
ahead.

cuddihy

.