ISS an accident waiting to happen ?

http://www.space.com/missionlaunches...er_030925.html

Comments on this anyone ?

David Linney wrote:
http://www.space.com/missionlaunches...er_030925.html
Comments on this anyone ?

Mostly sensationalism to draw attention to the article. The board resigned at
the request of the CAIB so it could be reconstituted etc, not because of
problems at the station. They merely said that the station had some
coordination problems between russia and the USA.

They should have implemented a distributed lock manager for the station. When
the USA segment has control of attitude, it should take a lock on the russian
computers to prevent them from firing thrusters. And vice versa. Such things
should not be at the mercy of humans who hope they won't push their button in
moscow bnefore the americans have pushed theirs in houston.

Delegating more of the station's control to the crew on board would also
result in better coordination of tasks, albeit at the cost of increased workload.

http://www.space.com/missionlaunches...er_030925.html

It's a good illustration of why the ASAP has been ineffective.

The ASAP comes up with these alarmist statements, NASA blows them off,
and that just makes the ASAP all the more interested in sounding the
alarm. But this doesn't get listened to, by much of anyone inside or
outside NASA.

As far as I can tell, in some cases the ASAP is right (e.g. having the
two attitude control systems fighting each other could quickly deplete
the fuel, which would be bad). And in other cases, they seem to be
blowing things out of proportion (hard to put my finger on an example,
since just about anything *potentially* has a safety impact, but maybe
the statements about upmass to ISS at
http://www.hq.nasa.gov/office/codeq/...ts/asap02e.pdf on page
44 are an example. Just because there is not enough room for
everything someone wants to fly doesn't mean there is or will be a
safety impact - how about complaining more specifically about what
that impact is?).

So, yeah, I'm not going to miss the ASAP, as it has existed. Let's
hope that it gets replaced by something which works better.

: ISS an accident waiting to happen ?

I hopew the crew gets off OK. I wonder if a lost station would be a goiod
thing

Without the station Shuttle isnt needed.

Good time for redesigning everything and setting our sites on MARS!

Yes, the guy obviously has a suspect motive and knows nothing about
the ISS. A loss of CMG attitude control poses absolutely no risk to
the crew.




On 29 Sep 2003 22:45:41 -0700, (David Linney)
wrote:

http://www.space.com/missionlaunches...er_030925.html

Comments on this anyone ?

There is such a lock manager - it's called GNC Moding. The US
software has the following modes:

Wait
Standby
UDG
Drift
CMGTA
CMG Only

and the Russians have:

Indicator Regime
CMGTA
Thrusters Only
Reboost

If the US is in CMGTA, the Russians will also be in CMGTA. In CMGTA
the gyroscopes control the attitude and the RS thrusters only fire in
response to requests for desaturation counter torques.

If the US is in CMG Only, then the Russians will be in Indicator
Regime. In CMG Only, the gyroscopes control attitude and will not ask
for desaturation counter torques.

However, the Russian Segment GNC computers are designed to take
control if it appears that the US computers have failed (1553 loss of
comm).

Attitude Control handovers involve coordinated handshaking - inside
the software. It is not a matter of flight controllers mis-timing
commands.



On Tue, 30 Sep 2003 05:57:02 -0400, Will Riker
wrote:

David Linney wrote:
http://www.space.com/missionlaunches...er_030925.html
Comments on this anyone ?

Mostly sensationalism to draw attention to the article. The board resigned at
the request of the CAIB so it could be reconstituted etc, not because of
problems at the station. They merely said that the station had some
coordination problems between russia and the USA.

They should have implemented a distributed lock manager for the station. When
the USA segment has control of attitude, it should take a lock on the russian
computers to prevent them from firing thrusters. And vice versa. Such things
should not be at the mercy of humans who hope they won't push their button in
moscow bnefore the americans have pushed theirs in houston.

Delegating more of the station's control to the crew on board would also
result in better coordination of tasks, albeit at the cost of increased workload.

A force fight would not quickly deplete the fuel. In the event of a
force fight, the CMG system (which can only store 14000 N-m-s of
angular momentum) would quickly saturate and remove itself from active
control.



On 30 Sep 2003 12:13:53 -0400, Jim Kingdon wrote:

http://www.space.com/missionlaunches...er_030925.html

It's a good illustration of why the ASAP has been ineffective.

The ASAP comes up with these alarmist statements, NASA blows them off,
and that just makes the ASAP all the more interested in sounding the
alarm. But this doesn't get listened to, by much of anyone inside or
outside NASA.

As far as I can tell, in some cases the ASAP is right (e.g. having the
two attitude control systems fighting each other could quickly deplete
the fuel, which would be bad). And in other cases, they seem to be
blowing things out of proportion (hard to put my finger on an example,
since just about anything *potentially* has a safety impact, but maybe
the statements about upmass to ISS at
http://www.hq.nasa.gov/office/codeq/...ts/asap02e.pdf on page
44 are an example. Just because there is not enough room for
everything someone wants to fly doesn't mean there is or will be a
safety impact - how about complaining more specifically about what
that impact is?).

So, yeah, I'm not going to miss the ASAP, as it has existed. Let's
hope that it gets replaced by something which works better.

Delegating more of the station's control to the crew on board would also
result in better coordination of tasks, albeit at the cost of increased
workload.

I reckon all station control should be done onboard. Appoint a captain of
the station, who makes the final decision on everything.

David

David Findlay wrote:
I reckon all station control should be done onboard. Appoint a captain of
the station, who makes the final decision on everything.


Problem is one of workload. Both Russia and USA spent considerable resources
developping a "remote controlled" station. This way, while the crew is busy
with experiments or sleeping ground can monitor station systems and take
whatever actions necessary. And while the crew is asleep, ground can download
new software to the computers which would then require only a small amount of
crewmember's time to complete the operation.

Consider this: while you are working at your desk, there is someone at the
power generating plant monitoring voltage and other systems to make sure you
can do you work. There is somebody in your building making sure your air
conditioning, telephone, security, elevators work well so that you can be
productive in your work.

So it is not so abnormal to expect crewmembers to concentrate on experiments
while ground makes sure station works well.

Problem is one of workload. Both Russia and USA spent considerable
resources developping a "remote controlled" station. This way, while the
crew is busy with experiments or sleeping ground can monitor station
systems and take whatever actions necessary. And while the crew is asleep,
ground can download new software to the computers which would then require
only a small amount of crewmember's time to complete the operation.

Well yes. The tech is still not good enough to be largely autonomous of
ground control. But it should be. If we want to get spaceflight cheaper we
need to get rid of 5000 people working just for one single mission at any
time. Space stations need to be bigger, have seperate engineering, command
and science teams, and three shifts so that the station can be working
around the clock. The ground can still be useful, but working for the guys
upstairs, instead of the guys upstairs working for the guys on the ground.

David