Discussion -- Suppose we had evacuated ISS after Columbia?

On 2005-06-17, Jim Oberg wrote:

Unmanned mode does not force commanding into tumble. The station
could be placed in a stable gravity-gradient attitude. The arrays don't even
need to actively track in such a low-load no-crew configuration.

A thought - when Saluyt 7 was re-occupied by the first Mir crew, was it
stable or tumbling?

--
-Andrew Gray

"Jim Oberg" wrote in
:

You may see one angle to this discussion, and that has to do with an
alternative future in which the Russians had NOT become key partners
in the design. Loss of shuttle in such a case would have required a
crew evacuation (through a small bail-out capsule designed and built
with all the money that was saved by not having the Russians along and
by not having to haul all the hardware into an inefficient orbital
inclination).

How soon we forget, Jim... :-)

Before the Russians joined the program, the space station was only to be
intermittently man-tended throughout the assembly sequence, with permanent
crew capability not arriving until the end. The bail-out capsule (ACRV)
would not have been attached until the last assembly flight (MB-17). So a
shuttle accident prior to assembly complete would not have required
evacuation; the station would simply continue to operate autonomously
(until systems start breaking down, of course...). On the other hand, a
shuttle accident *after* assembly complete would indeed require evacuation.

--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

"Andrew Gray" wrote in message
. ..
On 2005-06-17, Jim Oberg wrote:

Unmanned mode does not force commanding into tumble. The station
could be placed in a stable gravity-gradient attitude. The arrays don't
even
need to actively track in such a low-load no-crew configuration.

A thought - when Saluyt 7 was re-occupied by the first Mir crew, was it
stable or tumbling?

It was stable or at least very low angular rate,
according to Dzhanibekov.

Excellent point -- the Russian presence gave us long-duration crew earlier
than originally planned.
And the value of having a long-duration crew? Mainly to maintain the
hardware to keep
the crew alive on long-duration missions.



"Jorge R. Frank" wrote
How soon we forget, Jim... :-)

Before the Russians joined the program, the space station was only to be
intermittently man-tended throughout the assembly sequence, with permanent
crew capability not arriving until the end. The bail-out capsule (ACRV)
would not have been attached until the last assembly flight (MB-17). So a
shuttle accident prior to assembly complete would not have required
evacuation; the station would simply continue to operate autonomously
(until systems start breaking down, of course...). On the other hand, a
shuttle accident *after* assembly complete would indeed require
evacuation.

Jim Oberg wrote:
Granted we have to find a better system than Elektron. This doesn't
mean band-aiding the current design when it's clear the current design
needs wholesale replacement. Learning how to make the current design
work is useless information, since the current system is going to be
retired soon anyway.


retired soon ?????

Until you learn exactly what makes elektron fail, it is pointless to
think that shipping a new unit will magically solve your problems. It
may prove to be reliable for a while, but it will fail in the same ways
as the old elektron.

If they do manage to bring the old unit down for a post mortem, perhaps
the engineers on the ground might find the reason for it being
unreliable, but they may not since they can't reproduce 0g conditions on
the ground.

And it isn't a question of band-aiding the current design. It is a
question of finding out what works and what doesn, process of
elimination of possible causes and possible solutions. These are designs
which probably work flawlessly on the ground and really need to be
tested in long term use in 0g before the problems arise. This is why
leaving the unit off for 2,5 years would have been stupid since this is
the real research going on in the station.

The americans have 0 experience with O2 generators in space, so if/when
they do launch one, it will take 5 years before they know if it works
reliably or not. CDRA seemed to give them some reliability numbers
failry quickly though. (nort good).

Jim Oberg wrote:
Unmanned mode does not force commanding into tumble. The station
could be placed in a stable gravity-gradient attitude. The arrays don't even
need to actively track in such a low-load no-crew configuration.

But what happens when there is a guidance system failure as has happened
before ? If they can't recover, they must put the station in thumble
mode so that arrays get ~some~ sunshine during each orbit.

And there are serious electrical loads when there are no crews. You need
need cooling/heating, some ventilation, all the sensors. So your load
diminishes because you doN't have Elektron and Vozdhuk running, and
hopefully, the condensing units won't fill up during the years of
unmanned since there are no humans breathing humidity, but the cooling
is still needed.

And you still need electricity to have the arrays track the sun, GPS
units, Comms, cameras. Etc.

Jim Oberg wrote: Hmmm, I don't recall this. I know the crew had heard
'strange noises', but
I didn't think any were associated with CMG problems that the crew
could monitor on displays of data that the ground could not see.

If you can be more specific on date I can check the detailed records
available in my archives.


As I recall, it was during a shuttle mission. The strange noises
coincided with bad data from the CMG sensors and were assumed to be bad
ball bearings and the unit was shutdown in a failed status. If i am not
mistaken, it might have been the same mission where the hard drives
failed on the station systems, and that is when they also first use the
canadarm. (which had to be used "in manual mode" because they didn't
want to stress the hard drives of the computer systems). However, I am
not sure it was that particular mission.

Jim Oberg wrote:

Excellent point -- the Russian presence gave us long-duration crew earlier
than originally planned.
And the value of having a long-duration crew? Mainly to maintain the
hardware to keep
the crew alive on long-duration missions.

The value ? Start debugging all the systems and ensuring they work
reliably for long periods of time.

Had this been a USA only station, imagine the wasted time oif after 10
years of assembly, they send the first permanent crew up and within two
weeks, they find out that never used CRDA didn't work reliably ? ( whith
CDRA having never been use for more than a couple days at a time before).

Cosnider that during those 10 years, the USA oxygen generator would have
never been tested for more than a couple of days at a time and it is
only at the end of assembly that thhey would realised, months if not a
few years later that the design was somehow flaed and the unit was
unreliable ?

Having permanent habitation allows those problems to arise sooner and
thus fixed sooner.

10 years in the grand scheme of thing is a long period and it would mean
a delay of 10 years to a mars mission since you can't go there until you
have a realiable O2 generator that you have tested for long operiod in
0g and know it can be relied on.

The Russians have promised to deliver a dry-electrolyte o2 generator
that has no ancestry in Elektron hardware, next year. It's about the
same time as the Hamilton-Sundstrand dry-electrolyte unit from NASA
shows up on node-2.

Elektron will be history, and nobody will care why it didn't work long.




"John Doe" wrote in message ...
Jim Oberg wrote:
Granted we have to find a better system than Elektron. This doesn't
mean band-aiding the current design when it's clear the current design
needs wholesale replacement. Learning how to make the current design
work is useless information, since the current system is going to be
retired soon anyway.


retired soon ?????

Until you learn exactly what makes elektron fail, it is pointless to
think that shipping a new unit will magically solve your problems. It
may prove to be reliable for a while, but it will fail in the same ways
as the old elektron.

If they do manage to bring the old unit down for a post mortem, perhaps
the engineers on the ground might find the reason for it being
unreliable, but they may not since they can't reproduce 0g conditions on
the ground.

And it isn't a question of band-aiding the current design. It is a
question of finding out what works and what doesn, process of
elimination of possible causes and possible solutions. These are designs
which probably work flawlessly on the ground and really need to be
tested in long term use in 0g before the problems arise. This is why
leaving the unit off for 2,5 years would have been stupid since this is
the real research going on in the station.

The americans have 0 experience with O2 generators in space, so if/when
they do launch one, it will take 5 years before they know if it works
reliably or not. CDRA seemed to give them some reliability numbers
failry quickly though. (nort good).

John Doe wrote:
Until you learn exactly what makes elektron fail, it is pointless to
think that shipping a new unit will magically solve your problems. It
may prove to be reliable for a while, but it will fail in the same ways
as the old elektron.

It is well known why it fails. The fundamental reason is liquids
behave differently in 0g. In particular it is damn difficult to
separate liquid from gas because gas bubbles do not raise to the
surface in 0g as they do on Earth. I don't know how those dry
electrolyte devices are supposed to solve the problem, you still
have to put liquid H20 in and get gaseous O2/H2 out.

It's a shame though that we don't see relevant experiments carried
out on ISS right now because that's what it is up there for.