"Ian Woollard" wrote in message
om...
What I'm trying to understand or get a feeling for is why the Space
Shuttle takes whatever it takes (the three weeks I mentioned is
probably incorrect) to turnaround after a launch to prepare it to
launch again. I'm just trying to understand it, from the point of view
of looking at ways it could be improved upon in future launch
vehicles.

A typical orbiter flow is broken down into three segments. The first is its
stay in an Orbiter Processing Facility. The average stay is 80 days, and
during that period it is given a thorough inspection, the payload bay is
unloaded and reconfigured for the next flight, systems are tested to verify
their functionality, repairs are made as required, life-cycle-limited items
are replaced as required, small modifications may be performed as time
allows, and some fluids are added for the next flight (ammonia, deionized
water, freon, etc.).

The next segment takes place in the VAB and involves integrating the orbiter
into the complete shuttle "stack". This takes between 5 and 7 days. The
orbiter is mechanically and electrically attached to the ET/SRB stack, and
the interfaces are tested.

The final segment takes place at the pad and runs about 25 days. Hypergolics
are added to the orbital propulsion systems, hydraulics are tested, the main
propulsion system is leak-tested, payload is loaded into the payload bay (if
it wasn't already loaded in the OPF), work on open items from the OPF flow
continues, and final closeout inspections are performed.

For example, some of the tiles need replacement, and I imagine it
takes atleast a week elapsed repairing that. Mating SRBs and main
tanks seem to take a week elapsed or so in total. I bet there are
repairs on the main engines etc. (SSMEs get removed and reinserted I
believe, don't know how long that takes), that kind of thing. Are
there any other long timescale items?

Tile repair is worked in parallel with all other processing work. SRBs take
about a week per booster to stack, but require more work beyond that - say,
a month. The ET doesn't require much work once it arrives at KSC; a small
day-shift team takes care of that. The SSMEs are pulled from the orbiter
after landing and taken to the engine shop for inspection and maintenance. A
fresh set is installed in the orbiter near the end of its stay in the OPF.

The Columbia accident will probably lead to a longer stay in the OPF to
accommodate more extensive inspections. United Space Alliance had plans in
place to gradually reduce the length of an OPF flow to just 30 days by
around 2010, but the mission schedule simply isn't going to require that
kind of effort.

What else can I tell you?

-Kim-