Author Topic: Crew limitations for ISS  (Read 19086 times)

Offline DarkenedOne

  • Full Member
  • ****
  • Posts: 951
  • Liked: 56
  • Likes Given: 8
Crew limitations for ISS
« on: 03/12/2011 06:24 PM »
Alright lets just assume for the moment that SpaceX succeeds with the Dragon with the ability to carry crew.  I remember it was stated somewhere that SpaceX believes it would be able to deliver 7 astronauts on the dragon for $20 million.  If that pans out than NASA will be able to send twice as many people to the ISS for less than what we pay the Russians right now. 

At the moment as I understand it we are largely limited by the crew carrying capacity of the Soyuz.  I remember the Russians saying that they would no longer be able to use the Soyuz for any tourism because all four of the Soyuz spacecraft produced every year need to be dedicated to sustaining the 6 man crew on the ISS. 

What I have been wondering is whether or not there are any other obstacles to maintaining a larger crew on the ISS.  Are the life support systems up to the task, and if not could they be upgraded to handle the additional capacity.

Also assuming long term crew capacity could be increased would it increase the productivity of the ISS.  Obviously with any faculty you reach a point where increasing the number of workers decreases productivity. 

Offline Jason1701

  • Senior Member
  • *****
  • Posts: 2238
  • Liked: 70
  • Likes Given: 39
Re: Crew limitations for ISS
« Reply #1 on: 03/12/2011 06:35 PM »
Russians have committed to producing a fifth Soyuz per year starting in 2013. Space Adventures will once again be sending up tourists. I think the US crew could be increased to four from 2015 onward, since most of the commercial crew vehicles under development would carry seven.

Others are better equipped to answer your life support questions.

Offline Space Pete

Re: Crew limitations for ISS
« Reply #2 on: 03/12/2011 06:37 PM »
There's a lot more to it than just Soyuz seats.

As you mentioned, ECLSS hardware would have to be upgraded (which wouldn't be easy). More consumables would need to be launched each year to support the crew, and we'd need more sleep stations.

ISS has been designed to support 6 crewmembers. It can support more (the record is 13), but only for short periods of time (~2 weeks max).

One way to increase ISS crewmembers would be to use one Soyuz to launch three Russians, and one commercial vehicle to launch three Americans per Increment. A second Soyuz could then be used for short-duration "taxi flights", as Russia used to do prior to Columbia.
NASASpaceflight ISS Editor

Offline apace

  • Full Member
  • ****
  • Posts: 810
  • Liked: 3
  • Likes Given: 1
Re: Crew limitations for ISS
« Reply #3 on: 03/12/2011 06:43 PM »
ISS has been designed to support 6 crewmembers.

Not 7?

Offline Dapholine

  • Member
  • Posts: 39
  • Liked: 5
  • Likes Given: 13
Re: Crew limitations for ISS
« Reply #4 on: 03/12/2011 07:02 PM »
Not 7?

I believe that plan died with the cancellation of the CRV. After the CRV was canceled, Soyuz would be used as the emergency vehicle, thus it was reduced to 6.

Offline Space Pete

Re: Crew limitations for ISS
« Reply #5 on: 03/12/2011 07:07 PM »
ISS has been designed to support 6 crewmembers.

Not 7?

ISS was originally intended for 7 crewmembers, but it was decided a while ago to only support 6 crewmembers.
« Last Edit: 03/12/2011 07:08 PM by Space Pete »
NASASpaceflight ISS Editor

Online hop

  • Senior Member
  • *****
  • Posts: 3277
  • Liked: 429
  • Likes Given: 776
Re: Crew limitations for ISS
« Reply #6 on: 03/12/2011 07:58 PM »
At the moment as I understand it we are largely limited by the crew carrying capacity of the Soyuz.
In addition to the problems mentioned by others, it doesn't matter how many you can produce if you can't park them. Each crew member needs to have a ride home available for their entire stay (CRV). There are only 4 compatible docking ports, and they need to support Progress and ATV. Parking 3 Soyuz for long durations would be impractical. I suppose in theory the Russians could start building APAS Soyuz again and park them on a PMA...

The ISS already went to "indirect" handovers (having the station drop to 3 during rotation instead of going up to 9), in part to help deal with traffic issues.

The math also doesn't work out very well with 3 Soyuz, because ISS might support 7 but 9 for any extended period would be pushing it. So you'd end up wasting seats.

To support 7 for long periods, you'd need US side CRV or a Russian vehicle with more than 3 seats.

I think the US crew could be increased to four from 2015 onward, since most of the commercial crew vehicles under development would carry seven.
Only if they have CRV capability, which isn't a given.

Offline DarkenedOne

  • Full Member
  • ****
  • Posts: 951
  • Liked: 56
  • Likes Given: 8
Re: Crew limitations for ISS
« Reply #7 on: 03/13/2011 12:25 AM »
At the moment as I understand it we are largely limited by the crew carrying capacity of the Soyuz.
In addition to the problems mentioned by others, it doesn't matter how many you can produce if you can't park them. Each crew member needs to have a ride home available for their entire stay (CRV). There are only 4 compatible docking ports, and they need to support Progress and ATV. Parking 3 Soyuz for long durations would be impractical. I suppose in theory the Russians could start building APAS Soyuz again and park them on a PMA...

The ISS already went to "indirect" handovers (having the station drop to 3 during rotation instead of going up to 9), in part to help deal with traffic issues.

The math also doesn't work out very well with 3 Soyuz, because ISS might support 7 but 9 for any extended period would be pushing it. So you'd end up wasting seats.

To support 7 for long periods, you'd need US side CRV or a Russian vehicle with more than 3 seats.

I think the US crew could be increased to four from 2015 onward, since most of the commercial crew vehicles under development would carry seven.
Only if they have CRV capability, which isn't a given.

Well I understand about the limitations of the Soyuz, but future planned vehicles including the Dragon, the Dreamchaster, and the Boeing CST-100 all are designed for 7 people. 

Assuming we use just one of these vehicles with the Soyuz the ISS would have a crew return capability of 10 astronauts. 

Also we should consider whether permanent crew return capability is necessary. After all future missions to places like the Moon and Mars might not have this capability.

Offline Danderman

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 9597
  • Liked: 354
  • Likes Given: 460
Re: Crew limitations for ISS
« Reply #8 on: 03/13/2011 12:31 AM »
Russians have committed to producing a fifth Soyuz per year starting in 2013. Space Adventures will once again be sending up tourists.

From what I have read, the reverse is true - Space Adventures would like a 5th Soyuz, but Roskosmos has not agreed.

Offline pathfinder_01

  • Full Member
  • ****
  • Posts: 1887
  • Liked: 49
  • Likes Given: 0
Re: Crew limitations for ISS
« Reply #9 on: 03/13/2011 12:32 AM »

Also we should consider whether permanent crew return capability is necessary. After all future missions to places like the Moon and Mars might not have this capability.

It would be foolish not to have this ability if possible. The ISS can hold 7 but lacks a lifeboat.  The CST100 can stay in orbit for 7 months, unsure about manned dragon's limit and NASA's Orion can stay for 6 months. The US only needs 4 seats min but more is preferable.

Return from the moon is possible. It is just that for the moon or mars having a dedicated lifeboat makes no sense. For the ISS the need arose because the shuttle could not stay in space for months. With commercail crew a provider might not want to tie their craft up the for the whole lenght of the expidition.
« Last Edit: 03/13/2011 12:53 AM by pathfinder_01 »

Offline Danderman

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 9597
  • Liked: 354
  • Likes Given: 460
Re: Crew limitations for ISS
« Reply #10 on: 03/13/2011 12:34 AM »
In a world where Dragon can support 4+ crew members as a transfer vehicle and as a lifeboat, so that ISS crew would increase to 7 or more, all of the above issues could be trivially resolved.  We, however, don't presently live in that world.

Dragon could easily bring up additional life support resources, consumables, sleeping facilities, there really isn't a show-stopper for ISS crew expansion, if there is a functional and reliable Dragon.



Offline pathfinder_01

  • Full Member
  • ****
  • Posts: 1887
  • Liked: 49
  • Likes Given: 0
Re: Crew limitations for ISS
« Reply #11 on: 03/13/2011 12:41 AM »
In a world where Dragon can support 4+ crew members as a transfer vehicle and as a lifeboat, so that ISS crew would increase to 7 or more, all of the above issues could be trivially resolved.  We, however, don't presently live in that world.

Dragon could easily bring up additional life support resources, consumables, sleeping facilities, there really isn't a show-stopper for ISS crew expansion, if there is a functional and reliable Dragon.


Ideally a lifeboat would hold 7. It would allow more space to manurve a sick or disabled crew memeber as well as allow the whole station to evacuted if for some reason the russians can't get to Soyuz. Additional seats could also come in handy if a commercail crew craft is unable to return to earth.

Online hop

  • Senior Member
  • *****
  • Posts: 3277
  • Liked: 429
  • Likes Given: 776
Re: Crew limitations for ISS
« Reply #12 on: 03/13/2011 01:17 AM »
Well I understand about the limitations of the Soyuz, but future planned vehicles including the Dragon, the Dreamchaster, and the Boeing CST-100 all are designed for 7 people. 
At least initially, I don't think any of these are planned to be able to stay at the station for a long time. "Orion CRV" is.

Quote
Also we should consider whether permanent crew return capability is necessary. After all future missions to places like the Moon and Mars might not have this capability.
Discussed previously, see  http://forum.nasaspaceflight.com/index.php?topic=20833.0 and http://forum.nasaspaceflight.com/index.php?topic=20543.msg557374#msg557374 for example.

Bottom line:
1) Having a CRV adds significant safety benefits for marginal cost.
2) It would be stupid to discard these benefits on this mission just because it won't be available on some other mission.
3) The people who operate ISS are not in the habit of taking unnecessary risk.

If the ISS partners wanted to up the crew count (which AFAIK none of them are particularly clamoring for), the most likely way to do it would be to certify one or more of the new US vehicles for long stays. This should not be hugely expensive, my earlier comment was to point out that they aren't all currently planned to have this capability. A US CRV will probably happen at some point, and it will probably be capable of carrying more than 3.

If the Russians actually add all their planned modules, supporting larger crews will also get easier.

Offline pathfinder_01

  • Full Member
  • ****
  • Posts: 1887
  • Liked: 49
  • Likes Given: 0
Re: Crew limitations for ISS
« Reply #13 on: 03/13/2011 01:34 AM »

At least initially, I don't think any of these are planned to be able to stay at the station for a long time. "Orion CRV" is.

[

CST100 is designed for 7 months. 1 month longer than Orion. Dreamchaser and Dragon unknown but I would expect dragon to be storable for months in it's basic form and as a free flyer dragon has a 2 year life. It is just the different enviroment at the ISS that might limit it.

Offline PeterAlt

  • Full Member
  • ****
  • Posts: 706
  • West Palm Beach, FL
  • Liked: 2
  • Likes Given: 32
Re: Crew limitations for ISS
« Reply #14 on: 03/18/2011 03:45 AM »
The plan is to use commercial crewed (or Orion as backup) vehicles as liefboats as well as crew transportation, just as the Soyuz is now. Once crewed commercial (or Orion) vehicles are in service, the Russians will use a single Soyuz (not two at a time) for Expedition crews, freeing up a Russian docking port for short term Soyuz visits or more Progress vehicles. The additional crew capacity of commercial crew vehicles or Orion will allow at least one additional crew member. In fact, the Russian Space Agency a few months ago announced in a press release that ISS will have a crew size of seven once the new American vehicles enter service.

Offline Danderman

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 9597
  • Liked: 354
  • Likes Given: 460
Re: Crew limitations for ISS
« Reply #15 on: 03/18/2011 02:10 PM »
Well I understand about the limitations of the Soyuz, but future planned vehicles including the Dragon, the Dreamchaster, and the Boeing CST-100 all are designed for 7 people. 
At least initially, I don't think any of these are planned to be able to stay at the station for a long time. "Orion CRV" is.

Really?

What aspects of a crewed Dragon would preclude lengthy stays at ISS?

Offline erioladastra

  • Full Member
  • ****
  • Posts: 1257
  • Liked: 75
  • Likes Given: 0
Re: Crew limitations for ISS
« Reply #16 on: 03/19/2011 08:16 PM »
Not 7?

I believe that plan died with the cancellation of the CRV. After the CRV was canceled, Soyuz would be used as the emergency vehicle, thus it was reduced to 6.

Nope still the plan.  Not sure of the timescale but that is our next major milestone.

Offline robertross

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 17795
  • Westphal, Nova Scotia
  • Liked: 461
  • Likes Given: 3851
Re: Crew limitations for ISS
« Reply #17 on: 03/19/2011 08:44 PM »
Not 7?

I believe that plan died with the cancellation of the CRV. After the CRV was canceled, Soyuz would be used as the emergency vehicle, thus it was reduced to 6.

Nope still the plan.  Not sure of the timescale but that is our next major milestone.

whoa....7?
I assume you mean based on commercial crew capabilities.
Remembering those who made the ultimate sacrifice for our rights & freedoms, and for those injured, visible or otherwise, in that fight.

Offline Space Pete

Re: Crew limitations for ISS
« Reply #18 on: 03/19/2011 08:57 PM »
Not 7?

I believe that plan died with the cancellation of the CRV. After the CRV was canceled, Soyuz would be used as the emergency vehicle, thus it was reduced to 6.

Nope still the plan.  Not sure of the timescale but that is our next major milestone.

Woo! That will certainly enable more science to get done.

We need another Crew Quarters! :)
NASASpaceflight ISS Editor

Online The-Hammer

  • Member
  • Full Member
  • ****
  • Posts: 410
  • Liked: 1
  • Likes Given: 1
Re: Crew limitations for ISS
« Reply #19 on: 03/19/2011 10:38 PM »
I understand that there's supposed to be a third Russian CQ in MLM when it launches.
Grant Imahara: Oxygen deficiency alarm? Is that something I should be worried about?
NASA worker: Only if it goes off.

Offline Space Pete

Re: Crew limitations for ISS
« Reply #20 on: 03/19/2011 10:56 PM »
I understand that there's supposed to be a third Russian CQ in MLM when it launches.

A-ha! Yes, of course.

That would mean that all Russian crewmembers could sleep in the RS (two Kayutas in the SM, plus one in the MLM), which would leave four CQs in the USOS.
NASASpaceflight ISS Editor

Offline Dapholine

  • Member
  • Posts: 39
  • Liked: 5
  • Likes Given: 13
Re: Crew limitations for ISS
« Reply #21 on: 03/19/2011 11:51 PM »
Nope still the plan.  Not sure of the timescale but that is our next major milestone.
Well of course. That is the long-term-plan, but as long as there is no 4+-person CRV, that plan is dead in the water.

Woo! That will certainly enable more science to get done.

We need another Crew Quarters! :)
Yes, I read that as: once we finally get a 7th (or 8th) crew member, the shuffling-bags-or-doing-repair-work to actual-time-spend-on-science ratio will finally be useful. Remember we have Columbus, Destiny and KIBO on the USOS. That is one lab per crew member! Compare that to the Spacelab missions...
The ISS is designed to be useful with 7 (and probably more!!) crew members and we need them ASAP. Somehow, in these past 10 years, policy makers have failed to notice that a large space station is only useful when it's packed with astronauts doing actual science (tm). *sigh*


« Last Edit: 03/19/2011 11:52 PM by Dapholine »

Offline Jason1701

  • Senior Member
  • *****
  • Posts: 2238
  • Liked: 70
  • Likes Given: 39
Re: Crew limitations for ISS
« Reply #22 on: 03/20/2011 01:57 AM »
Nope still the plan.  Not sure of the timescale but that is our next major milestone.
Well of course. That is the long-term-plan, but as long as there is no 4+-person CRV, that plan is dead in the water.

Woo! That will certainly enable more science to get done.

We need another Crew Quarters! :)
Yes, I read that as: once we finally get a 7th (or 8th) crew member, the shuffling-bags-or-doing-repair-work to actual-time-spend-on-science ratio will finally be useful. Remember we have Columbus, Destiny and KIBO on the USOS. That is one lab per crew member! Compare that to the Spacelab missions...
The ISS is designed to be useful with 7 (and probably more!!) crew members and we need them ASAP. Somehow, in these past 10 years, policy makers have failed to notice that a large space station is only useful when it's packed with astronauts doing actual science (tm). *sigh*




Maybe in the future we can add a small sleep module to the USOS (perhaps Cygnus-delivered) and then use the commercial crew vehicles to have a crew of seven astronauts. Russians can maintain one Soyuz for a total crew of ten.

Offline arkaska

  • Senior Member
  • *****
  • Posts: 3041
  • Sweden
  • Liked: 0
  • Likes Given: 0
Re: Crew limitations for ISS
« Reply #23 on: 03/20/2011 10:17 AM »
There is also a limit to how many science-racks can be powered at the same time.

Offline CitabriaFlyer

  • Full Member
  • ***
  • Posts: 307
  • Liked: 14
  • Likes Given: 0
Re: Crew limitations for ISS
« Reply #24 on: 03/20/2011 11:26 AM »
Maybe once commercial space is operating competition between Dragon, CST and Souyz will make it feasible to send short term science crews to ISS to give it a science surge capability.  The crew would consist of a pilot, an engineer, and five scientists.  The pilot and engineer could assist in maintenance tasks and EVAs.  The scientists could work in the labs, split into teams for 24 hour ops which would perhaps relive some of the concern regarding number of racks powered up at any given time.  I would think that you would need two commercial launches to support this.  Once to bring up basic science materials and supplies and return processed samples to earth.  Another launch to bring the crew to and from space.

Offline Space Pete

Re: Crew limitations for ISS
« Reply #25 on: 03/20/2011 11:49 AM »
Maybe once commercial space is operating competition between Dragon, CST and Souyz will make it feasible to send short term science crews to ISS to give it a science surge capability.  The crew would consist of a pilot, an engineer, and five scientists.  The pilot and engineer could assist in maintenance tasks and EVAs.  The scientists could work in the labs, split into teams for 24 hour ops which would perhaps relive some of the concern regarding number of racks powered up at any given time.  I would think that you would need two commercial launches to support this.  Once to bring up basic science materials and supplies and return processed samples to earth.  Another launch to bring the crew to and from space.

I had the same idea, but for logistics, not science.

Assume you timed everything so that Dragon & Cygnus, or HTV & ATV, were present at ISS at the same time. You could then send up a commercial crew vehicle with a "logistics crew" to spend two weeks unloading these vehicles and filling them with trash, in addition to performing maintenance tasks.

It would be just like a Shuttle mission, in the sense that you'd have six people concentrating solely on fast-paced operations, which would in turn free up the Expedition crewmembers to concentrate on science.
« Last Edit: 03/20/2011 11:51 AM by Space Pete »
NASASpaceflight ISS Editor

Offline DARPA-86

  • Full Member
  • *
  • Posts: 137
  • Pig farmer from Ryan, Iowa
  • Liked: 0
  • Likes Given: 1
Re: Crew limitations for ISS
« Reply #26 on: 03/20/2011 12:25 PM »
Maybe once commercial space is operating competition between Dragon, CST and Souyz will make it feasible to send short term science crews to ISS to give it a science surge capability.  The crew would consist of a pilot, an engineer, and five scientists.  The pilot and engineer could assist in maintenance tasks and EVAs.  The scientists could work in the labs, split into teams for 24 hour ops which would perhaps relive some of the concern regarding number of racks powered up at any given time.  I would think that you would need two commercial launches to support this.  Once to bring up basic science materials and supplies and return processed samples to earth.  Another launch to bring the crew to and from space.

I had the same idea, but for logistics, not science.

Assume you timed everything so that Dragon & Cygnus, or HTV & ATV, were present at ISS at the same time. You could then send up a commercial crew vehicle with a "logistics crew" to spend two weeks unloading these vehicles and filling them with trash, in addition to performing maintenance tasks.

It would be just like a Shuttle mission, in the sense that you'd have six people concentrating solely on fast-paced operations, which would in turn free up the Expedition crewmembers to concentrate on science.
This is the metric by which we need to start to measure what is 'full utilization".  Number of man days over the course of a full year, example 365 X 6 = 2190 days per year.  Within that you also have the schedule requirements for long term residents vs. short term stays.  For instance Astronaut health requirements push for up to 2 and half hours a day of exercise to prevent bone and muscle tissue loss for long term space fliers, i.e. six months along with other rest and health related tasks that take time off the schedule.  For short term fliers, 15 days or less, those tasks are usually waived, thus freeing up for time on task.

As an aside, the original design reference - Space Station Freedom called for ten person crews.  I personally believe the "permanment crew" number has shifted based upon the availability of CRV "lifeboats.  The key is the on-orbit loiter time of those lifeboats.

Offline clongton

  • Expert
  • Senior Member
  • *****
  • Posts: 10422
  • Connecticut
    • Direct Launcher
  • Liked: 2378
  • Likes Given: 799
Re: Crew limitations for ISS
« Reply #27 on: 03/20/2011 12:37 PM »
Maybe in the future we can add a small sleep module to the USOS

Bigelow can supply the module. That was the original purpose of TransHab, from which all Bigelow designs are derived. The crew quarters area was designed for 6 as you can see from both the link and image below.

http://en.wikipedia.org/wiki/TransHab
« Last Edit: 03/20/2011 01:13 PM by clongton »
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline Space Pete

Re: Crew limitations for ISS
« Reply #28 on: 03/20/2011 01:03 PM »
Maybe in the future we can add a small sleep module to the USOS

Bigelow can supply the module. That was the original purpose of TransHab, from which all Bigelow designs are derived.

Probably the easiest thing to do would be to install four CQ (Crew Quarters) racks in Node 4/DHS, if it flies. This would mean that the visiting crewmembers would be sleeping near to their vehicle, in case an emergency suddenly occurred. The remaining two of the six visiting crewmembers could sleep in the vehicle itself.
« Last Edit: 03/20/2011 01:04 PM by Space Pete »
NASASpaceflight ISS Editor

Offline Danderman

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 9597
  • Liked: 354
  • Likes Given: 460
Re: Crew limitations for ISS
« Reply #29 on: 03/20/2011 03:47 PM »
In general, its hard to imagine a situation where we have a commercial crew vehicle and the ability to launch Node 4 to ISS and there still being technical limitations at ISS restricting the crew size to 6. Its kind of like asking if we had Warp drive, could we go to Mars.

Online hop

  • Senior Member
  • *****
  • Posts: 3277
  • Liked: 429
  • Likes Given: 776
Re: Crew limitations for ISS
« Reply #30 on: 03/20/2011 07:02 PM »
Well I understand about the limitations of the Soyuz, but future planned vehicles including the Dragon, the Dreamchaster, and the Boeing CST-100 all are designed for 7 people. 
At least initially, I don't think any of these are planned to be able to stay at the station for a long time. "Orion CRV" is.

Really?

What aspects of a crewed Dragon would preclude lengthy stays at ISS?
Given that Cargo dragon is expected to spend significant time at the station it's seems unlikely there would be major roadblocks to doing the same with the crew version. Of course there would additional work to certify it, but it would be surprising if there were really major problems.

Hmm, my impression was that one of justification for "Orion CRV" was that commercial would at least initially just be taxi service. But thinking back I'm not really sure where I got that and it doesn't make a whole lot of sense ;)


Offline robertross

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 17795
  • Westphal, Nova Scotia
  • Liked: 461
  • Likes Given: 3851
Re: Crew limitations for ISS
« Reply #31 on: 03/20/2011 07:11 PM »
Well I understand about the limitations of the Soyuz, but future planned vehicles including the Dragon, the Dreamchaster, and the Boeing CST-100 all are designed for 7 people. 
At least initially, I don't think any of these are planned to be able to stay at the station for a long time. "Orion CRV" is.

Really?

What aspects of a crewed Dragon would preclude lengthy stays at ISS?
Given that Cargo dragon is expected to spend significant time at the station it's seems unlikely there would be major roadblocks to doing the same with the crew version. Of course there would additional work to certify it, but it would be surprising if there were really major problems.

Hmm, my impression was that one of justification for "Orion CRV" was that commercial would at least initially just be taxi service. But thinking back I'm not really sure where I got that and it doesn't make a whole lot of sense ;)

Remember: commodities to sustain a crew of 7 means that service must be available for the entire trip. Now the food & water can come from ISS, but O2 is a different matter. The services must be able to be reliable over those months on orbit. I'm not saying they can't do it, but it has to be certified to last that long.

One good way would be to find mass savings in a cargo variant (which it seems they could) and fly the ECLSS on that flight and have it stay up there for that period of time.
Remembering those who made the ultimate sacrifice for our rights & freedoms, and for those injured, visible or otherwise, in that fight.

Offline pathfinder_01

  • Full Member
  • ****
  • Posts: 1887
  • Liked: 49
  • Likes Given: 0
Re: Crew limitations for ISS
« Reply #32 on: 03/20/2011 08:11 PM »

Remember: commodities to sustain a crew of 7 means that service must be available for the entire trip. Now the food & water can come from ISS, but O2 is a different matter. The services must be able to be reliable over those months on orbit. I'm not saying they can't do it, but it has to be certified to last that long.


err sorry, misunderstood your message.

Food: If I remember correctly food for the space shuttle has to have a 1 year shelf life. So that is no problem.

Water:In bottle form is storeable indefinitely. Most bottle watter on the market has a 1 year shelf life but can be kept longer. Not to mention purification systems.

Oxygen:Liquid oxygen tanks have been used to keep oxygen for years. Oxygen is rather unique in that the more you cool it the less volume it takes up. Not to mention other chemical reactions that can generate oxygen.

Plus the CRV would only need 2-4 days worth of it.
« Last Edit: 03/20/2011 08:47 PM by pathfinder_01 »

Offline Jorge

  • Senior Member
  • *****
  • Posts: 6180
  • Liked: 32
  • Likes Given: 0
Re: Crew limitations for ISS
« Reply #33 on: 03/21/2011 01:41 AM »

Oxygen is rather unique in that the more you cool it the less volume it takes up.

Umm, no, incorrect. *Most* compounds decrease in volume with decreasing temperature - there is *nothing* unique about oxygen in that regard. *Water* is anomalous in that it expands when it freezes, but that is the compound humans have the most experience with in multiple phases.
JRF

Offline Cherokee43v6

  • Full Member
  • ****
  • Posts: 658
  • Garner, NC
  • Liked: 231
  • Likes Given: 96
Re: Crew limitations for ISS
« Reply #34 on: 03/21/2011 02:26 AM »
Well I understand about the limitations of the Soyuz, but future planned vehicles including the Dragon, the Dreamchaster, and the Boeing CST-100 all are designed for 7 people. 
At least initially, I don't think any of these are planned to be able to stay at the station for a long time. "Orion CRV" is.

Really?

What aspects of a crewed Dragon would preclude lengthy stays at ISS?
Given that Cargo dragon is expected to spend significant time at the station it's seems unlikely there would be major roadblocks to doing the same with the crew version. Of course there would additional work to certify it, but it would be surprising if there were really major problems.

Hmm, my impression was that one of justification for "Orion CRV" was that commercial would at least initially just be taxi service. But thinking back I'm not really sure where I got that and it doesn't make a whole lot of sense ;)

Remember: commodities to sustain a crew of 7 means that service must be available for the entire trip. Now the food & water can come from ISS, but O2 is a different matter. The services must be able to be reliable over those months on orbit. I'm not saying they can't do it, but it has to be certified to last that long.

One good way would be to find mass savings in a cargo variant (which it seems they could) and fly the ECLSS on that flight and have it stay up there for that period of time.

An interesting angle to consider on that regarding Dragon.  7 people a life support system and pressurized supplies are surely much less in mass than the maximum capacity that a Cargo Dragon can carry to the station.  However, what is in the Crew Dragon's external trunk?  Shouldn't it be fairly easy for it be configured to carry a supply of compressed consumable gasses to support a 2 - 4 week science surge to the station?
"I didn't open the can of worms...
        ...I just pointed at it and laughed a little too loudly."

Offline robertross

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 17795
  • Westphal, Nova Scotia
  • Liked: 461
  • Likes Given: 3851
Re: Crew limitations for ISS
« Reply #35 on: 03/21/2011 12:08 PM »
The consumables on station, or that can be made available on station, are a fairly minor point for a surge crew. Extending more than one month, it could be a bit more challenging - but we're not there yet, and the commercial providers could fill that need, or Dragon itself.

The issue is the spacecraft itself. It takes time to qualify a system. Look at all the life support systems on the station that have had issues since we started all this. Obviously we are improving, but these are systems held by specific manufacturers. If we now bring in a new system, from a new manufacturer, there is a learning curve there, from all aspects, despite all processing steps. But this is how we learn, how the strong survive, and how a system becomes more robust.

Companies will eventually 'get there', but in some cases, ISS can't wait for that to happen. At least we have Progress, ATV & HTV to help the station out with logistics. What we lack is a Soyuz alternative that is up and running.
Remembering those who made the ultimate sacrifice for our rights & freedoms, and for those injured, visible or otherwise, in that fight.

Online Robotbeat

  • Senior Member
  • *****
  • Posts: 27789
  • Minnesota
  • Liked: 7670
  • Likes Given: 5111
Re: Crew limitations for ISS
« Reply #36 on: 03/21/2011 02:39 PM »
The consumables on station, or that can be made available on station, are a fairly minor point for a surge crew. Extending more than one month, it could be a bit more challenging - but we're not there yet, and the commercial providers could fill that need, or Dragon itself.

The issue is the spacecraft itself. It takes time to qualify a system. Look at all the life support systems on the station that have had issues since we started all this. Obviously we are improving, but these are systems held by specific manufacturers. If we now bring in a new system, from a new manufacturer, there is a learning curve there, from all aspects, despite all processing steps. But this is how we learn, how the strong survive, and how a system becomes more robust.

Companies will eventually 'get there', but in some cases, ISS can't wait for that to happen. At least we have Progress, ATV & HTV to help the station out with logistics. What we lack is a Soyuz alternative that is up and running.
Life support systems (non-regenerative) are not that new. The problems were, I believe, mainly with the more closed-loop systems.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline erioladastra

  • Full Member
  • ****
  • Posts: 1257
  • Liked: 75
  • Likes Given: 0
Re: Crew limitations for ISS
« Reply #37 on: 03/21/2011 04:02 PM »
Nope still the plan.  Not sure of the timescale but that is our next major milestone.
Well of course. That is the long-term-plan, but as long as there is no 4+-person CRV, that plan is dead in the water.

Woo! That will certainly enable more science to get done.

We need another Crew Quarters! :)
Yes, I read that as: once we finally get a 7th (or 8th) crew member, the shuffling-bags-or-doing-repair-work to actual-time-spend-on-science ratio will finally be useful. Remember we have Columbus, Destiny and KIBO on the USOS. That is one lab per crew member! Compare that to the Spacelab missions...
The ISS is designed to be useful with 7 (and probably more!!) crew members and we need them ASAP. Somehow, in these past 10 years, policy makers have failed to notice that a large space station is only useful when it's packed with astronauts doing actual science (tm). *sigh*




That is not a reasonable comparison.  The USOS science labs are designed to have much less crew interactions.  So 2-3 people for 3 labs is not as big an issue as you think it is.  Actually ISS power, thermal and most critically the up/down mass are the real limiters.  Obviously an extra person would help with more time but unlesswe have enough upmass (which I assume will go with the increase to 7) it is only part of the issue.

Offline manboy

  • Senior Member
  • *****
  • Posts: 2082
  • Texas, USA, Earth
  • Liked: 127
  • Likes Given: 539
Re: Crew limitations for ISS
« Reply #38 on: 04/26/2011 12:18 AM »
ISS has been designed to support 6 crewmembers.

A & S: Will the size of the crew come down?

Suffredini:
No. In fact, weíre designed on the U.S. side to take four crew. The ISS design is actually for seven. We operate with six because first, we can get all our work done with six, and second, we donít have a vehicle that allows us to fly a seventh crew member. Our requirement for the new vehicles being designed is for four seats. So I donít expect us to go down in crew size. I would expect us to increase it.

http://www.airspacemag.com/space-exploration/AS-Interview-Mike-Suffredini.html
« Last Edit: 04/26/2011 12:20 AM by manboy »
"Cheese has been sent into space before. But the same cheese has never been sent into space twice." - StephenB

Offline arkaska

  • Senior Member
  • *****
  • Posts: 3041
  • Sweden
  • Liked: 0
  • Likes Given: 0
Re: Crew limitations for ISS
« Reply #39 on: 04/26/2011 09:58 AM »
A & S: Will the size of the crew come down?

Suffredini:
No. In fact, weíre designed on the U.S. side to take four crew. The ISS design is actually for seven. We operate with six because first, we can get all our work done with six, and second, we donít have a vehicle that allows us to fly a seventh crew member. Our requirement for the new vehicles being designed is for four seats. So I donít expect us to go down in crew size. I would expect us to increase it.

http://www.airspacemag.com/space-exploration/AS-Interview-Mike-Suffredini.html

That's a strange statement by Suffredini since in a recent L2 document we can see that they have trouble getting enough science in since all other activities take to much of the crews time.

Offline manboy

  • Senior Member
  • *****
  • Posts: 2082
  • Texas, USA, Earth
  • Liked: 127
  • Likes Given: 539
Re: Crew limitations for ISS
« Reply #40 on: 05/03/2011 12:20 AM »
MLM will include the seventh crew quarter.

http://avia.mirtesen.ru/blog/43766285192
"Cheese has been sent into space before. But the same cheese has never been sent into space twice." - StephenB

Tags: