Space Forum / Shuttle / February 2006

About that, generally closer to 4 IIRC.

The solids aren't finished yet, so they'll need to be done, along with
the ET. I don't know what state the orbiter's in. From orbiter rollover
to rollout usually takes about a week.

Stacking of the solids started months ago. For a May 12 launch, I'd
expect to see Discovery roll over around late March to (more likely)
early April.

If Discovery hasn't been rolled over by mid-April, she won't fly in May.

I still wouldn't completely rule out Discovery's next trip being aboard
an SCA rather than a shuttle stack.

--Chris

I think it also has to do with the amount of sunlight available at the
Trans-Atlantic abort sites.

JD

There's a little more to it. :-) A launch window is actually a composite
of several constraints:

1) Rendezvous planar window - roughly speaking, the target orbit plane is
fixed in space while the Earth rotates under it. There are only two times
each day when the launch site passes through the orbit plane, one on the
south-to-north leg of the orbit and the other on the north-to-south. The
second one isn't used by the shuttle for range safety reasons; it would
cause the ET and SRBs to come down in inconvenient places.

2) Rendezvous phase window - once you've launched in-plane with the
target, you have to catch up to it. How long that takes depends on where
the target is within that orbit plane. If a vehicle has limits on phasing
capability, it may not be able to launch in every planar window. The
shuttle orbiter doesn't rendezvous until flight day 3 or 4 so it has
enough phasing capability to launch into any planar window.

The two constraints above apply to any rendezvous flight, and since all
future shuttle flights will rendezvous with something (either ISS or
HST), they always apply. For the shuttle, they don't affect whether you
can launch on a particular day, just what time of day you can launch
(planar window) and how long the window is open (both).

For all shuttle-ISS flights, a third constraint applies.

3) Beta constraint - beta is the angle between the orbit plane and the
line of sight to the sun. It determines how much of the orbit is lit and
how much is in the shadow of the Earth. That affects thermal control of
both orbiter and ISS, and ISS solar power generation. It turns out that
if the beta angle is greater than sixty degrees while an orbiter is
docked to ISS, it's impossible to find an orientation for the stack that
satisfies all three constraints, so NASA doesn't launch on those dates.
This constraint isn't very limiting; it creates "cutouts" in the launch
window every 2-3 months that last 2-3 weeks. These cutouts fall during
the nighttime during the summer, and during the daytime during the
winter.

There are two additional constraints that apply to the shuttle Return-To-
Flight test missions:

4) Daylight launch - for photography to see if the foam-shedding problem
is fixed.

5) Lit ET separation - for photography of the ET from the orbiter's
umbilical well camera, for the same reason.

In practice, 5) is more constraining than 4). They are very limiting; in
combination with the beta cutouts, they limit shuttle launches to four
periods during the spring/summer/fall roughly two months apart lasting
roughly 2-3 weeks, with two more periods during the winter lasting maybe
a few days, if you're lucky. These two constraints go away after two
flights with no ET foam shedding above the allowable limits.

Nop. Space station doesn't follow the earth's rotation. It follows an
essentially fixed circular path.

Twice a day, the earth's rotation places KSC directly under that path.
It is only when KSC is under that path that they can launch the shuttle
which can then accelerate along that path and meet with the station
travelling in exactly the same direction.

Think about 2 bowling balls.  You can throw then in intersectinbg paths,
but when they meet, they collide. You need to throw the second one to go
slightly faster and not only in the same direction, but also the same
"path" so that it will gently meet the first one and stay with it.

Due to the earth's rotation, the path of the ISS's orbit moves over the
surface of the earth at roughly 1600km/h. If the shuttle doesn't launch
at exactly the right time, it needs to compensate and that costs a lot
of fuel. Because fuel is limited, they have a narrow launch window of
about 10 minutes before and after the exact time.

Furthermore, because of geography, the shuttle can only launch in a
north-east direction. And this means that only once a day is there a
launch window where shuttle can fly north east and meet up with the ISS.

To complicate matters, the ISS's orbit actually does rotate a little bit
every day. So every day, the launch time moves by a few minutes.

Current requirements are that the shuttle launch in daytime and ET can
be photographed once in orbit while still in daylight. So this restricts
launchs to only certain periods onf the year when this is possible.

OK, you're the expert, so I'll ask: Why is recertification not necessary
for unmanned operation?

Please stop snipping and replying to a post that wasn't the source.
Hiding
text and your answer are not effective forms of making a technical
point.

<restoring context>

Bob Haller wrote:

</restoring context>

Bob Haller wrote:

I don't see the humor here.  Please explain.

Now, you're the expert, so please discuss the following.  Suppose that
loss
of control of the orbiter occurs during rendezvous and docking with
ISS?
Suppose that uncontrolled propulsion systems firing are made with the
orbiter docked to ISS?  I don't see how the lack of recertification
will
help here.  I don't see how the lack of humans on-board will help here.
In
your answer please consider -- as just one source of information --
NESC
document RP-05-18, Shuttle Orbiter Reaction Jet Driver (RJD)
Independent
Technical Assessment/Inspection Report.  Also discuss the loss of
control of
a 200,000+ lb orbiter during reentry and how the lack of certification
and a
crew on board to deal with malfunctions is safe.

Irrelevant.  Please stay on topic.

Please address safety issues including the points above.

--
rk, Just an OldEngineer
"The number of people having any connection with the project must be
restricted in an almost vicious manner.  Use a small number of good
people."
-- Kelly Johnson in Skunk Works
--
rk, Just an OldEngineer
"The number of people having any connection with the project must be
restricted in an almost vicious manner.  Use a small number of good
people."
-- Kelly Johnson in Skunk Works

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Is this enough pasting for you???/:(

I put a smiley behind cant kill a crew, since the only reason the
shuttle is being shut down is the risk of killing another crew. Up
untill columbia most here and certinally nasa were happy to fly this
system at least another 20 years...

Revendous and docking would FIRST invoplve a soyuz crew flying over to
manually fly and dock the shuttle to the station! Docking of shuttlke
wouldnt be automated!

shuttle docked to ISS would have ISS crew in shuttle as needed

uncontrolled engine firing of shuttle can occur at any time, its one
shuttle trouble that would have to be addressed to continue past
2010..its a danger today assuming RTF ever occurs

on reentry, white sands or a off shore landing area would have to be
used to minimize danger during reentry. but even with manned reentry
there are non recoverable failure modes that a live crew cant help,
columbia is a excellent example.

Have a question for YOU, if the next flight sees more foam loss how
will the station be finished and supported till the new system is up
and running?

More to the point, the CAIB doesn't make an exception for it:

R9.2-1
Prior to operating the Shuttle beyond 2010, develop and conduct a vehicle
recertification at the material, component, subsystem, and system levels.
Recertification requirements should be included in the Service Life
Extension Program.