"Adam Darren" wrote in message

Ok, lets say that there was a problem with tiles and that they decided to
attempt a very different re-entry profile to protect the damaged side (at
the
expense of other areas).

I don't believe there's really much of a predictable capability to do this;
the black side of the orbiter gets hot - the grey areas get really hot, and
the white areas aren't supposed to get very hot. ;-) Aerodynamics, control,
and thermal constraints dictate the attitude the orbiter flies at during
entry. "Protecting" a damaged area - even if theoretically possible - would
likely involve flying in an un-trimmed state and require constant jet
firings and also possibly put other areas of the vehicle over their
allowable design temperatures and creating more (and possibly worse)
problems.

Could the re-entry program be modified with a new
re-entry profile while the shuttle is in orbit ?

There are three parameters that are very important at EI (entry interface):
energy (altitude and speed), REI (range at entry interface), and the angle
at EI. REI and the angle at EI have to be within a specific range and are
dependent on many things including vehicle weight, etc. The shuttle's entry
conditions have been adjusted over the years, as I recall, to result in the
most benign entry possible. There has been some discussion about decresing
the angle at EI *slightly* and increasing the REI *slightly* in order to
provide a lower *peak* temperature, but that would result in greater tile
backface temperatures - there's always a tradeoff. I have seen other papers
that purport to lower the temps even further, but they are only theoretical
and have not been tested or evaluated in any way.

Could the guidance computers be programmed to perform the
initial/different
re-entry which would bring the shuttle to a random location at a specific
altitude and more or less random speed, at which point ground could decide
which runway to target and re-load the computers with the necessary info
to
reach that runway ?

If I am not mistaken, if the drag was greater than expected and the orbiter
for some reason could not make the planned site, the orbiter could be
retargeted to another site that was reacheable. The crew would need to know
exactly which site was best for them, though, and potential landing sites
are not that common. I think with upcoming software releases there are about
90 runways that will be in the orbiters database. Selecting the right one
will be made easier with software that I am involved in testing right now.
See http://www.spacecoretech.org/coretech2002/ssa.html. There are some
papers hosted there that explain the capabilities of SAFM:

1) Onboard Determination of Vehicle Glide Capability for Shuttle Abort
Flight Management (SAFM)

2) Shuttle Flight Abort Management (SAFM) - Application Overview

This new application is possible due to the capabilities provided as part of
the CAU program. [Another poster in a separate thread has claimed that the
MEDS displays and/or CAU is somehow responsible or related to the demise of
Columbia because of "improperly spent funds", but I find this claim to be
without merit and misguided]. You might find the above documents to be an
interesting read.

Jon