Re: Are Solid Boosters Safe?

From: Henry Spencer (henry_at_spsystems.net)
Date: 03/29/05 

Date: Tue, 29 Mar 2005 17:27:59 GMT

In article <eTa2e.7623$Ab.6758@text.news.blueyonder.co.uk>,
Brian Gaff <briang1@blueyonder.co.uk> wrote:
>Solids are not stoppable.

Actually, they are -- the final stage of solid-fuel ICBMs is routinely
stopped when the desired trajectory has been reached -- but it's a
somewhat violent process. Originally the shuttle SRBs were supposed to
have that capability; indeed, solids were picked on the assumption that
thrust termination was feasible. Unfortunately, while terminating the SRB
thrust is possible, the ET and orbiter are unlikely to survive the large
transient loads it causes, so there's not much point.

>However, if one fired, I'd suspect it would be an unsurvivable failure, as
>the bolts holding down the stack fire so soon after ignition.

Simultaneously, in fact.

>I don't think they are any less safe, indeed, more safe (?) than liquids,
>given what happens if a fuel line breaks.

There are two fundamental safety differences, and both favor liquids. One
is that solid failures are almost always catastrophic, whereas most liquid
failures are benign, especially if you shut the engine down as soon as you
detect something going wrong. The other is that liquids can be test-fired
before use, allowing problems to be found on the ground, while a solid
motor is inherently a one-shot device. 

-- 
"Think outside the box -- the box isn't our friend."    |   Henry Spencer
                                -- George Herbert       | henry@spsystems.net

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