Why install the payload at the pad?

I've wondered why the payload isn't installed in the payload bay either
at the OPF or the VAB. Why is it often (always?) done at the pad?

Just curious.

Lee Jay

Lee Jay wrote:
I've wondered why the payload isn't installed in the payload bay either
at the OPF or the VAB. Why is it often (always?) done at the pad?

It avoids the risk of the payload being jolted around too much while the
orbiter is being stacked in the VAB, and during roll-out. It can't be
done while the stacked orbiter is in the VAB because there just isn't
the equipment, and the VAB isn't clean enough.

--Chris

Lee Jay wrote:
I've wondered why the payload isn't installed in the payload bay either
at the OPF or the VAB. Why is it often (always?) done at the pad?

When you consider how long it takes between the shuttle bay doors closed at
OPF and the actual launch, your cargo wouldn't be able to carry any
perishable experiments.

If the whole flow of work had been done so that they could be like a Soyuz:
move to the pad and launch the next day, then perhaps they could have done
payload loading in the VAB.

The one advantage of the current process is that it frees the VAB quickly.
This way, they can pipeline the work with an orbiter in OPF, one in VAB and
one at the pad, and thus theoretically have more frequent launches.

Chris Bennetts wrote:
Lee Jay wrote:
I've wondered why the payload isn't installed in the payload bay either
at the OPF or the VAB. Why is it often (always?) done at the pad?

It avoids the risk of the payload being jolted around too much while the
orbiter is being stacked in the VAB, and during roll-out. It can't be
done while the stacked orbiter is in the VAB because there just isn't
the equipment, and the VAB isn't clean enough.

I can buy the second two reasons, but I can't believe the accelerations
endured during stacking and rollout are close to those seen during
launch.

Lee Jay

John Doe wrote:
Lee Jay wrote:
I've wondered why the payload isn't installed in the payload bay either
at the OPF or the VAB. Why is it often (always?) done at the pad?

When you consider how long it takes between the shuttle bay doors closed at
OPF and the actual launch, your cargo wouldn't be able to carry any
perishable experiments.

If the whole flow of work had been done so that they could be like a Soyuz:
move to the pad and launch the next day, then perhaps they could have done
payload loading in the VAB.

The one advantage of the current process is that it frees the VAB quickly.
This way, they can pipeline the work with an orbiter in OPF, one in VAB and
one at the pad, and thus theoretically have more frequent launches.

Interesting. I hadn't thought of those reasons. The only reasons I
could think of involved the need to "maintain" the payload with
electricity and other consumables and that doing so would be difficult
during stacking and rollout. I don't know if that's a real reason or
not.

Lee Jay

Certainly this latter reason was what I recall being said when they were
originally planning more frequent launches in the early days. I think its a
legacy from those days and if it works, why change it?

Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"John Doe" wrote in message
...
Lee Jay wrote:
I've wondered why the payload isn't installed in the payload bay either
at the OPF or the VAB. Why is it often (always?) done at the pad?

When you consider how long it takes between the shuttle bay doors closed
at OPF and the actual launch, your cargo wouldn't be able to carry any
perishable experiments.

If the whole flow of work had been done so that they could be like a
Soyuz: move to the pad and launch the next day, then perhaps they could
have done payload loading in the VAB.

The one advantage of the current process is that it frees the VAB quickly.
This way, they can pipeline the work with an orbiter in OPF, one in VAB
and one at the pad, and thus theoretically have more frequent launches.

Actually, many payloads are installed in the OPF. To put it in a really
simple way, if it is a horizontally processed payload such as the old Space
Labs, or Space Station elements, it is installed while the orbiter is
horizontal. Vertically processed payloads are installed at pad via the
PGHM.


"Brian Gaff" wrote in message
k...
Certainly this latter reason was what I recall being said when they were
originally planning more frequent launches in the early days. I think its
a legacy from those days and if it works, why change it?

Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"John Doe" wrote in message
...
Lee Jay wrote:
I've wondered why the payload isn't installed in the payload bay either
at the OPF or the VAB. Why is it often (always?) done at the pad?

When you consider how long it takes between the shuttle bay doors closed
at OPF and the actual launch, your cargo wouldn't be able to carry any
perishable experiments.

If the whole flow of work had been done so that they could be like a
Soyuz: move to the pad and launch the next day, then perhaps they could
have done payload loading in the VAB.

The one advantage of the current process is that it frees the VAB
quickly. This way, they can pipeline the work with an orbiter in OPF, one
in VAB and one at the pad, and thus theoretically have more frequent
launches.

neon wrote:
Actually, many payloads are installed in the OPF. To put it in a really
simple way, if it is a horizontally processed payload such as the old Space
Labs, or Space Station elements, it is installed while the orbiter is
horizontal. Vertically processed payloads are installed at pad via the
PGHM.

That's not as true now as it used to be. Pretty much all space station
elements of late (which are all processed horizontally) have been
installed at the pad.

--Chris

"Lee Jay" wrote in message Chris Bennetts wrote:
Lee Jay wrote:
It avoids the risk of the payload being jolted around too much while the
orbiter is being stacked in the VAB, and during roll-out. It can't be
I can buy the second two reasons, but I can't believe the accelerations
endured during stacking and rollout are close to those seen during
launch.

he didn't say 'accelerations,' he said 'jolted.' launch is a ~8-9 minute
period of vibration, acceleration, etc.. just the trip to the pad is what,
the better part of a day? neglilgible acceleration, but i'd think a decent
amount of vibration. if payload includes delicate instrumentation/hardware..
why subject it to that duration of needless abuse?

-r (admittedly conjecture.. but it kinda makes sense)

No Body wrote:
"Lee Jay" wrote in message Chris Bennetts wrote:
Lee Jay wrote:
It avoids the risk of the payload being jolted around too much while the
orbiter is being stacked in the VAB, and during roll-out. It can't be
I can buy the second two reasons, but I can't believe the accelerations
endured during stacking and rollout are close to those seen during
launch.

he didn't say 'accelerations,' he said 'jolted.' launch is a ~8-9 minute
period of vibration, acceleration, etc.. just the trip to the pad is what,
the better part of a day? neglilgible acceleration, but i'd think a decent
amount of vibration.

Vibration is acceleration (cyclic).

Lee Jay