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#80
by
Jim
on 29 Sep, 2009 19:04
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Which gives us another rationale for returning Pirs on Shuttle, since the current baseline is to remove and destroy Pirs, and then hope that MLM works, and if not, Zvedza zenith port remains hybrid forever.
That is not a viable reason. A new Pirs would be easier.
I can provide many other what ifs. Don't undock ATV's, the next one might not dock.
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#81
by
Jim
on 29 Sep, 2009 19:05
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Other than the PLM, there are no other missions with an empty payload bay
Is this actually true? If not, are there missions that will return with a partially empty payload bay?
I'm under the impression that 129 will land with an emptly PLB, so will 130, 134, 133
Still forgetting the Pirs cradle.
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#82
by
Space Pete
on 29 Sep, 2009 19:13
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There are no more assembly missions, no more items to be left at the ISS. The "additional" missions will just be resupply, MPLMs and ELC's
I think that ELC's + Node 3 count as assembly missions.
Which gives us another rationale for returning Pirs on Shuttle, since the current baseline is to remove and destroy Pirs, and then hope that MLM works, and if not, Zvedza zenith port remains hybrid forever.
Unless of course you put some kind of Hybrid-to-Probe & Drogue adapter hatch in Zvezda's zenith port, much like this style of hatch (obviously the hatch would need to include all the necessary hardware to latch spacecraft in place):
Also, I'm under the impression that MLM will dock at Zvezda's nadir.
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#83
by
Danderman
on 29 Sep, 2009 19:16
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Other than the PLM, there are no other missions with an empty payload bay
Is this actually true? If not, are there missions that will return with a partially empty payload bay?
I'm under the impression that 129 will land with an emptly PLB, so will 130, 134, 133
Still forgetting the Pirs cradle.
No one can possibly forget your assumed Pirs cradle, but it would be nice to separate urban legends from actual facts. It appears that many Shuttle missions will land with an empty payload bay, despite your earlier assertion.
There is also an assertion that a Pirs cradle would have a large volume, which is something to be examined.
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#84
by
Jim
on 29 Sep, 2009 19:18
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I think that ELC's + Node 3 count as assembly missions.
We are talking the extension missions.
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#85
by
Jim
on 29 Sep, 2009 19:20
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No one can possibly forget your assumed Pirs cradle, but it would be nice to separate urban legends from actual facts. It appears that many Shuttle missions will land with an empty payload bay, despite your earlier assertion.
What urban legends? What are you calling me out on?
You are trying to look at something that is not viable, Can't you take a hint.
Which missions ? We are talking extension missions, not the ones on the current manifest.
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#86
by
Danderman
on 29 Sep, 2009 19:21
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Unless of course you put some kind of Hybrid-to-Probe & Drogue adapter hatch in Zvezda's zenith port, much like this style of hatch (obviously the hatch would need to include all the necessary hardware to latch spacecraft in place):
Also, I'm under the impression that MLM will dock at Zvezda's nadir.
I screwed up and confused Zvezda Nadir with Zenith. MLM and Pirs operate at Zvezda Nadir. Sorry.
As for your adapter hatch for Zvezda NADIR in case MLM has a bad day, sure, it could be done, in theory a Progress could deliver it on its nose, subject to control-ability issues, or it could be carried up by Shuttle, although Jim will tell us that's not possible because its cradle would take up the whole payload bay.
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#87
by
Jim
on 29 Sep, 2009 19:22
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There is also an assertion that a Pirs cradle would have a large volume, which is something to be examined.
It would be as long or longer than the PIRS and then add the clearance for placing it in the bay, which will negate room for a MPLM.
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#88
by
Jim
on 29 Sep, 2009 19:24
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Jim has also informed us that MPLMs absolutely cannot be parked at ISS for long periods, nor that the ISS RMS can berth a module to ISS using the probe and cone docking system.
SO this was a slam.
The MPLM is not going to be parked at the ISS. It is a PLM, a big difference.
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#89
by
Space Pete
on 29 Sep, 2009 19:25
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We are talking the extension missions.
Ah, OK. I just got confused when you mentioned ELC's - all ELC's are currently planned to be launched on currently manifested missions.
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And also, maybe a cradle for Pirs could be, at least partially, constructed on orbit - there are already some unused keel assembly's on the ISS, that were used when the S0, S1 & P1 Trusses were launched.
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#90
by
Danderman
on 29 Sep, 2009 19:26
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What urban legends? What are you calling me out on?
You are trying to look at something that is not viable, Can't you take a hint.
Which missions ? We are talking extension missions, not the ones on the current manifest.
My original post suggested that we look at the possibility of extending or stretching out the Shuttle manifest, and if this happened, could Pirs be retrieved by Shuttle from ISS. I suggested that there may be missions that return to Earth with an empty payload bay, to which you responded:
Quote from: Jim on 09/28/2009 03:46 PM
Other than the PLM, there are no other missions with an empty payload bay
which does not appear to be accurate, thus the comment "urban legend". There have been other urban legends in this thread also, such as the "Pirs will not fit in the Shuttle payload bay", although its only 2.55 meters in diameter.
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#91
by
Danderman
on 29 Sep, 2009 19:28
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And also, maybe a cradle for Pirs could be, at least partially, constructed on orbit - there are already some unused keel assembly's on the ISS, that were used when the S0, S1 & P1 Trusses were launched.
I had no idea about this. Where are those keels now, and what is being done with them?
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#92
by
Jim
on 29 Sep, 2009 19:35
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And also, maybe a cradle for Pirs could be, at least partially, constructed on orbit - there are already some unused keel assembly's on the ISS, that were used when the S0, S1 & P1 Trusses were launched.
I had no idea about this. Where are those keels now, and what is being done with them?
Keels are not a generic item, that is swapped between spacecraft. The keel is another trunnion but in a different plane than the others. What holds the keel trunnion varies greatly between spacecraft. The truss keel assembly's are not viable for this.
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#93
by
Space Pete
on 29 Sep, 2009 19:35
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And also, maybe a cradle for Pirs could be, at least partially, constructed on orbit - there are already some unused keel assembly's on the ISS, that were used when the S0, S1 & P1 Trusses were launched.
I had no idea about this. Where are those keels now, and what is being done with them?
They are currently being stored inside the Truss.
Here's a photo of one of them.
I'll look for some more.
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#94
by
Space Pete
on 29 Sep, 2009 19:40
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Keels are not a generic item, that is swapped between spacecraft. The keel is another trunnion but in a different plane than the others. What holds the keel trunnion varies greatly between spacecraft. The truss keel assembly's are not viable for this.
The keel's in question were designed to support the S0/S1/P1 Truss segments, which weighed 13,132 Kg, 12,572 Kg, & 12,500 Kg respectively. Pirs weighs a comparatively small 3,580 Kg, so I would think that they would structurally be able to support Pirs.
Also, they will not be needed for the Truss segments ever again, so I see no problem with removing them - it would be a fairly simple EVA task.
I'm just trying to establish the feasibility of launching a "flat-packed" cradle for Pirs.
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#95
by
Space Pete
on 29 Sep, 2009 19:55
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Just for the record, here's some photo's of the keel assembly's in question:
Here they are attached to the S0 Truss (they needed to be removed once on orbit, as they would have prevented the MT from moving along the S0's rails):
Here's a couple of shots of them once they were removed on orbit:
You can see the keels installed inside the truss at the very right of this photo:
Hi-res version:
http://www.spaceflight.nasa.gov/gallery/images/shuttle/sts-126/hires/s126e013902.jpg
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#96
by
eeergo
on 29 Sep, 2009 20:24
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I'll get into the discussion. I too find this question interesting, even though it most probably won't ever need to be considered. But as a hypothetical question, it seems appealing.
So the main showstoppers you've talked about so far are volume, how to get a cradle up, how to attach it to Pirs, how to maneuver it to the payload bay and which mission can bring it down.
The volume issue is settled, because it would easily fit in the payload bay even with a cradle. There are also flights coming down with an empty payload bay (you forgot to mention 132, which will only bring the ICC back. That makes a total of 5 downmass-empty flights. Excluding extension, the only viable flights to bring it down would be 132, 133 and 134, because of the time needed for planning the operation. Of course, as it's not a pressing issue, it's probable it wouldn't be ready even for 133, but just talking from a technical standpoint.
How to transport it to ISS? If it's somehow made foldable and takes advantage of the existing keels (assuming some clever way to mount them with the cradle structure was devised), it could be delivered on an ELC. That would of course mean few to no ORUs in that ELC, which isn't a good tradeoff if there's no extension. The only other mission that may have the volume to hold a foldable/unfoldable cradle would be 130, but its APM is too low. So no extension = no Pirs cradle even if they really wanted it done.
The attachment to Pirs seems easier to me (from my untrained perspective) because you could build a sort of double ring structure that would hold the module from its two docking ends, keeping it in place. The cradle could even be fitted with a PDGF (or two) so that it could be maneuvered to/from Pirs instead of the other way round. That plan would probably mean a Zarya PDGF or using MRM-1 as a base (but I think this isn't possible because MRM-1 will have a FRGF?)
So, if they suddenly wanted Pirs down for some very pressing reason, it couldn't be done unless a Shuttle extension was approved? Could the cradle I proposed be concievably (and with a reasonable budget) be built?
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#97
by
Danderman
on 29 Sep, 2009 21:33
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Let me attack the cradle issue from a different perspective. First off, the most important decision is the orientation of Pirs in the Shuttle payload bay. The standard orientation would be lengthwise down the payload bay, similar to MRM-1 or the Docking Module. However, transverse mount (ie sideways) should also be considered, as well as the unfamiliar vertical mount.
In particular, vertical mounting would have advantages that don't seem to be obvious at first, but such an attitude would mostly obviate the cradle issue. Instead of a cradle, a "sort of" Russian male docking adapter could be flown in the Shuttle, locked into a keel pin socket. Then, Pirs would be moved by the RMS to be mated (via the Pirs passive docking adapter), hard docked in the vertical position, with 2 trunions attached to its sides (that part is still magic, although its possible that the truss keel pins mentioned above could be used as trunnions. Once hard docked to a keel fixture fixed to the floor of the payload bay, and assuming that this keel fixture (based on a Russian docking adapter), I suspect that Pirs would be very securely attached to the payload bay.
This "sort of" Russian docking adapter would have a mass about 200 kg, and be small enough to fit under an ICC, ELC and maybe even AMS-02, so it would not "fill the payload bay" as suggested above.
What I don't know is if there is a way to use the truss keel pins as trunnions for Pirs. With a max diameter of 2.55, and assuming a Shuttle payload bay diameter of (geez, I forgot what it is) around 4.5 meters, each keel pin must extend about 1 meter laterally, which from the photos is about their length. How the keel pins or any trunnion, would attach to Pirs is TBD at the moment.
This is a hand wave explanation for one orientation, I am sure that there are others for the other orientations, as well.
The trick is to minimize the mass and volume of the cradle. How that would be done would very interesting.
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#98
by
Jim
on 30 Sep, 2009 00:30
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so I would think that they would structurally be able to support Pirs.
That is a minor consideration. The dimensions are more critical.
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#99
by
Jim
on 30 Sep, 2009 00:42
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In particular, vertical mounting would have advantages that don't seem to be obvious at first, but such an attitude would mostly obviate the cradle issue. Instead of a cradle, a "sort of" Russian male docking adapter could be flown in the Shuttle, locked into a keel pin socket.
A. What says the russian docking adapter can take shuttle landing loads? docking loads are much less
B. The keel can not handle a free standing object. That is reason for the cradle.
