Newsgroups: sci.space.shuttle
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: Shuttle landing speed and affect on tires ?
Date: Thu, 14 May 1998 01:03:58 GMT

In article <4C5D3E300D135951.713BECC431457128.E30AA0FBDD3A4843@library-proxy.airnews.net>,
Chris B. <ccblack@airmail.net> wrote:
>     Wasnt there quite a bit of a scandal about the shuttles landing gear
>and brakes etc?  The landing gear on the shuttle are purposely undersized
>to save weight.  But the penalty on such a hot landing is extra wear and
>tear on the tires and brakes. Isnt that one of the reasons the shuttle has
>a parachute braking system for landing now?

It's worse than that.  The real problem, as I understand it, is that the
orbiter gained considerable weight and the landing gear was not redesigned.
The result is a rather marginal design.  One particularly bad feature is
that the tires are Criticality 1 items -- blow a single main-gear tire at
the worst time (nose-gear touchdown, when main-gear loads are highest),
and you probably wreck the orbiter, because the remaining tire on that
side can't carry the full load and will also fail.  During the safety
overhaul after Challenger, there was talk of doing something about this,
but I don't recall hearing of any significant changes...

This was particularly scary because the shuttle *has* blown a tire once,
although at a less critical time (just before stopping), and there were
several incidents of serious tire damage.  The braking chute was added to
reduce braking loads on the tires and make it easier to hold the nose up
longer.  (The slower the orbiter is moving when the nosegear touches down,
the less load the resulting nose-down attitude puts on the main gear.)
--
Being the last man on the Moon                  |     Henry Spencer
is a very dubious honor. -- Gene Cernan         | henry@zoo.toronto.edu