Re: How serious is the May window?

Katipo wrote:
Exactly how do launch windows? My understanding it is the time when the
distance the craft needs to travel to reach its destination is the shortest.

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.
.

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