Author Topic: General ISS Q&A thread  (Read 657297 times)

Offline usn_skwerl

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Re: General ISS Q&A thread
« Reply #940 on: 03/23/2009 06:37 PM »
what is the white circle with black center? i've seen quite a few of these along the truss on both sides. thanks.

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Offline anik

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Re: General ISS Q&A thread
« Reply #941 on: 03/23/2009 06:55 PM »
what is the white circle with black center?

One of targets of Space Vision System.

Offline ChrisC

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Re: General ISS Q&A thread
« Reply #942 on: 03/25/2009 02:08 AM »
I have a question about the orbital mechanics of the ISS.  I understand that the ISS orbital plane "precesses" around the Earth by about 5 degrees per day, which results in the shuttle launch windows advancing by about 20 minutes per day.  This is due to the non-spherical shape of the Earth, per an answer to an earlier question I posted.

Does this then mean that ISS overflight viewing conditions (i.e. lighting) should recur periodically?  That is, since it advances 5 degrees / 20 minute per day, then it should take about 72 days to come full circle (ha!) and repeat the pattern.

I ask because I'm sometime disappointed with the evening overflight viewing opportunities.  Right now in the U.S., ISS evening overflights are barely making it over the horizon before they blink out into shadow.  But in Europe you've got fantastic viewing.  If the 72-day cycle idea holds, then I just have to wait a few weeks and it'll probably be completely different timing.  In two months it'll be like this again.  Right?

Which leads to a related question.  Is there any seasonal pattern to viewability?  Is it generally better in the fall for the northern hemisphere, just to make an example?
« Last Edit: 03/25/2009 02:17 AM by ChrisC »
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Offline Antares

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Re: General ISS Q&A thread
« Reply #943 on: 03/26/2009 02:13 AM »
Why we do not use each supply ship that is sent as an extra section, so it gets bigger & bigger

Other reasons: these ships would occupy docking and berthing ports.  They don't each have two ports so they could not be daisy-chained.

Also, these ships are designed with less MMOD shielding, so they are statistically not allowed to stay attached longer than that designed-to period.
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Offline duane

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Re: General ISS Q&A thread
« Reply #944 on: 03/26/2009 02:41 AM »
Got a question I moved from the SpaceX Dragon thread to here:

Were the CBM on the ISS nodes designed for a specific number of total Berth/Unbearth actions ?  IE is there a upper limit on their total uses ? (Waranty number)

Just asking as it's my understanding that  Dragon, and Cygnus will be using the CBM's to deliver cargo (20 times in total ?).

Thanks a bunch!
Duane

Offline MKremer

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Re: General ISS Q&A thread
« Reply #945 on: 03/26/2009 05:14 AM »
Got a question I moved from the SpaceX Dragon thread to here:

Were the CBM on the ISS nodes designed for a specific number of total Berth/Unbearth actions ?  IE is there a upper limit on their total uses ? (Waranty number)

Just asking as it's my understanding that  Dragon, and Cygnus will be using the CBM's to deliver cargo (20 times in total ?).

Thanks a bunch!
Duane

The only mechanical parts are the latches and bolting mechanisms on the active (station) CBMs, and I haven't read anything that specified anything about design life issues.

The only limited life issues would be for exposed seal material, but the seals are installed on the docking craft's CBM (the passive side), and would normally be inspected and replaced if necessary before reuse.

Offline ChrisC

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Re: General ISS Q&A thread
« Reply #946 on: 03/27/2009 03:45 AM »
Just a pointer to an unanswered question about ISS orbital mechanics and viewing that I posted above a couple days ago ...
« Last Edit: 03/27/2009 03:45 AM by ChrisC »
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Offline Jorge

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Re: General ISS Q&A thread
« Reply #947 on: 03/30/2009 08:21 PM »
I have a question about the orbital mechanics of the ISS.  I understand that the ISS orbital plane "precesses" around the Earth by about 5 degrees per day, which results in the shuttle launch windows advancing by about 20 minutes per day.  This is due to the non-spherical shape of the Earth, per an answer to an earlier question I posted.

Don't forget (per the earlier question) that you also get an additional 4 minutes per day due to the Earth's motion around the Sun. So the average launch window advance is about 24 minutes per day.

Quote
Does this then mean that ISS overflight viewing conditions (i.e. lighting) should recur periodically?  That is, since it advances 5 degrees / 20 minute per day, then it should take about 72 days to come full circle (ha!) and repeat the pattern.

Closer to 60 days due to the additional effect mentioned above, but yes.

Quote
Which leads to a related question.  Is there any seasonal pattern to viewability?  Is it generally better in the fall for the northern hemisphere, just to make an example?

No. The launch window advance is mainly a function of ISS altitude, not season. There is nothing keeping it "in sync" with the seasons.
JRF

Offline agman25

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Re: General ISS Q&A thread
« Reply #948 on: 03/31/2009 08:57 PM »
Are estimates of the ISS mass required for reboosts. If yes, how do they keep track with all the coming and going?

Offline MKremer

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Re: General ISS Q&A thread
« Reply #949 on: 03/31/2009 09:14 PM »
Are estimates of the ISS mass required for reboosts. If yes, how do they keep track with all the coming and going?

They keep very strict accounting of every kg of mass that arrives or leaves the station. (One reason they're so picky with transfer item details on every Shuttle mission.)

Offline William Barton

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Re: General ISS Q&A thread
« Reply #950 on: 03/31/2009 09:26 PM »
What happens if a major module fails suddenly? Let's say, due to an undetected structure weakness, Node 1 suddenly ruptures (I'm imagining something too big to patch, though not so big the station breaks up).
« Last Edit: 03/31/2009 09:35 PM by William Barton »

Offline rdale

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Re: General ISS Q&A thread
« Reply #951 on: 03/31/2009 09:35 PM »
Abandon ship.

Offline maxx

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Re: General ISS Q&A thread
« Reply #952 on: 03/31/2009 09:48 PM »
Abandon ship.
OK for Node1&2 and the Lab but if it is Colombus or Kibo, can't they just close the hatch if the leak isn't immediately life threatening?

Offline nomadd22

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Re: General ISS Q&A thread
« Reply #953 on: 03/31/2009 09:57 PM »
Abandon ship.
How do you abandon ship if you can't pass through Node 1?

Offline William Barton

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Re: General ISS Q&A thread
« Reply #954 on: 03/31/2009 10:04 PM »
Abandon ship.
How do you abandon ship if you can't pass through Node 1?

Are all the places a Soyuz can dock on the Russian segment?

Offline Jorge

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Re: General ISS Q&A thread
« Reply #955 on: 03/31/2009 10:07 PM »
Abandon ship.
How do you abandon ship if you can't pass through Node 1?

I would think the answer would be obvious.If there is no USOS CRV (Orion, Dragon), then the crew on the USOS side cannot escape.
JRF

Offline Jorge

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Re: General ISS Q&A thread
« Reply #956 on: 03/31/2009 10:07 PM »
Abandon ship.
How do you abandon ship if you can't pass through Node 1?

Are all the places a Soyuz can dock on the Russian segment?

Yes.
JRF

Offline erioladastra

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Re: General ISS Q&A thread
« Reply #957 on: 04/01/2009 02:03 AM »
Abandon ship.
How do you abandon ship if you can't pass through Node 1?

First response is to close hatches and move closer to the Soyuz.  If it is something like Columbus, JEM, or airlock we would seal it off and be done with it.  If node 1, we would still have time to escape (by definition, if it too rapid of a depress we wouldn't be be talking further on this thread), seal it off.  Depending on which hatches were closed in the USOS you might be able to fix it down the road with an interna EVA.  You coul stay for a while on the RS but long term you would have to abandon ship.

Offline erioladastra

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Re: General ISS Q&A thread
« Reply #958 on: 04/01/2009 02:09 AM »
During last week's post launch news conference, there was some Q+A about expedition handover, overlap, crew changeout, etc.  One of the guys (Gerst or Suffredini) was talking about "direct handover" vs "indirect handover".  I didn't quite follow what he was talking about.  I think it was in the context of making sure that the expedition crews had a full 7-10 days of overlap in order to do a good transition, without the distraction of also having a shuttle mission docked, but I didn't fully understand the jargon.  Can someone explain?


erioladastra is probably the one to answer this, but my understanding is that direct handover means the new Soyuz docks before the old one leaves, allowing the new crewmembers to take the handover directly from the departing crewmembers, while indirect handover means the old Soyuz leaves first, so the handover is performed by the three "holdover" crewmembers. (Obviously only applies with a 6-person crew; an indirect handover with a 3-person crew leaves ISS temporarily uninhabited.)

The reason why this might be necessary is shortage of Soyuz/Progress/ATV docking ports. There are currently only three, and a direct handover will require all three (two for the old Soyuzes and one for the new one). That means that the Soyuz rotation schedule will be tightly coupled with the Progress/ATV schedule. Indirect handover frees up a port so that the Progress/ATV schedule can be kept independent (to some extent) from the Soyuz schedule.

While that is true that is not usually what we mean by direct or indirect (but I guess some might use those terms).  Normally it means this:  Direct we schedule N hours of timne for the crew to go over a handover book or specific topic (e.g., emergency response).  Indirect is where we do handover by showing - for example robotics where the new person gets to feel the thing while the old person is there to guide and show features.

Ok, I have to correct myself.  Turns out in 6-crew land, indirect does mean what is above my post.  Sorry for the error.

Offline Colds7ream

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Re: General ISS Q&A thread
« Reply #959 on: 04/02/2009 01:44 PM »
Apologies if this has been asked before, but I'm confused as to the difference between an ISS Expedition and an ISS Increment. Would anyone be able to explain what it is, please?