Author Topic: Seven crew members  (Read 18524 times)

Online Herb Schaltegger

Re: Seven crew members
« Reply #20 on: 01/25/2015 11:48 PM »
No, my question is about commercial crew vehicles, asking why all of the CCtCap candidates have a 7 crew member capacity when the ISS already has 6 crew members and is already being serviced by at least one Soyuz.
No, my question is about commercial crew vehicles, asking why all of the CCtCap candidates have a 7 crew member capacity when the ISS already has 6 crew members and is already being serviced by at least one Soyuz.

Because they are all trying to market tourists for the ISS and possible vehicles for trips like bigelow.

Not a holdover from lifeboat/acrv days?

The "ACRV" dates back to Space Station Freedom designs and operational plans, and was never more than notional. There were to be two of them, each with a capacity for 4 in ordinary configurations. I don't recall whether the notional spec was to have more seats than that or not for contingencies.
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Offline Darren_Hensley

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Re: Seven crew members
« Reply #21 on: 01/26/2015 03:21 AM »
My research says "SSF" and "ISS" versions of the current station were manned based on CRV (old designation ACRV) lifeboats, period! The X-38 was the precursor project to the lifeboat implementation. The ISS panel decided that two docked Soyuz craft would make up for the scrapped CRV program giving tremendous returns in real dollars. Enough even to save money buying seats on the Soyuz. Thus the Full scale CRV was never built.

STS capacity had nothing to do with Commercial Crew Designs. Pure coincidence. STS could do more than 8 in an emergency if absolutely necessary based on available space in the flight decks.

So the most often sighted reasons are...
Reason 1: The cost of the CRV fleet was additional to the ferry fleet of manned capsules already scheduled to visit the ISS. Which, in congress and ESAs eyes, would be double or more to operate both systems.
Reason 2: 7 Crew members aboard the ISS vs. Six Crew members is also a large cost expenditure in terms of consumables, sleeping quarters, waste disposal, atmosphere processing and myriad of other notable mass savings. Enough to justify reduction vs meeting planned capacity.

Now to address the 7 seats of the Commercial Crew programs. The capsules 7 "Seats" were seen as a design feature that theoretically could replace a CRV for down mass in terms of bodies. The up mass of any combination of crew and pressurized cargo could be accommodated on a as needed basis. The CRV and/or capsules would go 6 months on-orbit, but no up mass (other than the ship itself) was ever intended with CRV. The 7th seat in either ship could be replaced with valuable down mass.

All return capabilities were based on a 6 month on-orbit shelf life, factored on battery cold (standby) state, Thruster fuel storage, and Docking seal longevity.
~ all sources are international partners web sites and proposal documentation from NRTS.

The bottom line is simple. Economics, not capability, drove the current policy, and design trends for both ISS manning and all CC programs. This conclusion excludes future uses of the capsules for other non-ISS LEO missions and BEO. Obviously the crew number would vary based on mission requirements.

If a docked Capsule and Soyuz(s) were at station together, choice is given rather than excluded for evacuation. Risk is present in any scenario. And if single capsule failure were an exclusion factor 6 members minimum could still return in any combination of two ships, or in the singular Commercial Crew capsule. Having no more than 6 members aboard ISS is an optimal number for any docked capsule configuration, over capacity for down mass is a happystance, under capacity planning is never intentionally allowed. A 3 seat CC ship would still allow for 6 crew to return in an emergency, a single Soyuz return for 6 crew members is out of the question.

I'm sure there are other opinions out there, but this one is mine based on extensive research into the CRV program and the recent program changes in commercial crew, and ISS manning history.
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Online Herb Schaltegger

Re: Seven crew members
« Reply #22 on: 01/27/2015 01:14 AM »
My research says "SSF" and "ISS" versions of the current station were manned based on CRV (old designation ACRV) lifeboats, period! The X-38 was the precursor project to the lifeboat implementation.

Well, you can reach whatever conclusions you want based on your extensive research. I can tell you from personal experience that the "ACRV" (Assured Crew Return Vehicle) was always depicted in Space Station Freedom system diagrams, module layouts and design planning documents as a gumdrop-shaped capsule line drawing. As far as Space Station design and operational planning people were concerned, that was it: a notional way to get 4 people down the ground no matter what (hence the "Assured" part ;) ).  That's it. Nothing else ever mattered to the people working Space Station.
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Offline manboy

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Re: Seven crew members
« Reply #23 on: 01/31/2015 07:48 AM »
No, my question is about commercial crew vehicles, asking why all of the CCtCap candidates have a 7 crew member capacity when the ISS already has 6 crew members and is already being serviced by at least one Soyuz.
No, my question is about commercial crew vehicles, asking why all of the CCtCap candidates have a 7 crew member capacity when the ISS already has 6 crew members and is already being serviced by at least one Soyuz.

Because they are all trying to market tourists for the ISS and possible vehicles for trips like bigelow.

Before Commercial Crew, when the ISS was a destination for Orion, the max crew for an Orion was seven.
Nope, it was six.

http://www.nasa.gov/pdf/306407main_orion_crew%20_expl_vehicle.pdf
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Offline Pipcard

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Re: Seven crew members
« Reply #24 on: 03/20/2015 04:33 AM »
Is the ISS capable of supporting more than six crewmembers, probably with more resupply missions?

Offline Burninate

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Re: Seven crew members
« Reply #25 on: 03/20/2015 05:44 AM »
Is the ISS capable of supporting more than six crewmembers, probably with more resupply missions?
Since the ISS only supports a crew of six, are they really anticipating the availability of destinations such as small commercial space hotels?
The ISS program is intended to support a crew of seven.

Six has been the interim guideline while the station's lifeboat count minimum is two Soyuz capsules (with three crew each).  With a 4-person commercial crew capsule attached, and one Soyuz attached, the station can support seven safely.  NASA suggested a bonus capability in decisionmaking would be a 7-person capsule to evacuate the whole station, in order to provide contingency lifeboat access if zero Soyuz capsules are operational for some reason connected to the evacuation.  In routine operation, that extra space will be filled with non-human downmass, and I doubt Russia would voluntarily go without a single Soyuz capsule attached for any length of time.
While we're picking nits, the ECLSS in the USOS is, almost to a "T," the very same ECLSS designed for Space Station Freedom, which was baselined for a crew of 8 - two independent ARS racks and two independent WRM system racks, each planned to support a nominal 4-person metabolic load, with capacity to handle 8 if necessary (during repairs, contingencies, etc). While the module locations for some of the racks and support equipment have changed, the basic guts of the systems haven't.

That said, the crew sizes for commercial vehicles are based on the general consensus of what's the best overall compromise between mass, cost and capability.

Didn't these answer your question?

The ISS life support could handle 8 long-term with redundancy without changing out the life support system, or 16 if you exhaust the redundancy, but 7 is the intended crew.  Expanding the life support system with new racks is an idea, but I have no idea whether it would be effective, or whether there are upstream bottlenecks.  Additional modules which supplement the life support system in the abstract could hypothetically expand these numbers, but it may end up being more profitable if you're going to substantially increase station size, to just start over with a fresh, more scalable design, something intended to take crew numbers from 10^1 to 10^3 as it expands rather than to be the intensely political first Western attempt at a long-term modular outpost in space, with a minimal crew.  Things like the airflow topology or the control moment gyros or the solar array wing don't really permit painless growth to the point that it could sustain 20 or 30 people, so significant growth would require significant replacement of existing station functions with new modules.

One BA-2100 would be two and a half times the size of the current station.  An array of seven BA-2100's in a figure eight configuration would be seventeen times the size of the current station, and could be plumbed for much better airflow, could permit more security against MMOD strikes, could be designed with larger angular momentum exchange capacity, could be designed from the start for SEP stationkeeping, would have better thermal inertia and insulation, with more docking and berthing ports... the list goes on.

Even tin can MPLM-derived modules look pretty damn nice at, say, a 7 meter diameter standard, in the right configuration, with an emphasis on expandability and inexpensive operation, and with the lessons we have learned in the design and operation of the ISS.
« Last Edit: 03/20/2015 05:52 AM by Burninate »

Offline Patchouli

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Re: Seven crew members
« Reply #26 on: 04/28/2015 11:14 PM »
Most of the commercial crew vehicles seem to have a normal capability of three to  four passengers with seven is mostly for emergencies.

« Last Edit: 04/28/2015 11:19 PM by Patchouli »

Offline manboy

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Re: Seven crew members
« Reply #27 on: 04/29/2015 07:57 AM »
Most of the commercial crew vehicles seem to have a normal capability of three to  four passengers with seven is mostly for emergencies.
I believe you are incorrect. The CCVs would have four seats for ISS missions, but seven seats for possible commercial spaceflights to a Bigelow space station.
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Offline Ben the Space Brit

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Re: Seven crew members
« Reply #28 on: 04/30/2015 12:26 PM »
Since the ISS only supports a crew of six, are they really anticipating the availability of destinations such as small commercial space hotels?

My guess is that, somewhere in the early bowels of the Commercial Crew program was a requirement to be compatible with a Launch On Need (LON) evacuation mission to the ISS - One pilot and the ability to carry all six members of the station crew. As far as I can tell, this is no longer an active mission parameter but it had its impact on all the commercial crew designs.
« Last Edit: 04/30/2015 12:26 PM by Ben the Space Brit »
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Offline FishInferno

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Re: Seven crew members
« Reply #29 on: 04/30/2015 12:37 PM »
If my knowledge is correct, a single Bigelow module can support seven crew, while it takes all of the ISS modules combined to support seven crew.  So joining multiple Bigelow modules can produce some serious crew capacity.
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Offline rayleighscatter

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Re: Seven crew members
« Reply #30 on: 04/30/2015 02:27 PM »
If my knowledge is correct, a single Bigelow module can support seven crew, while it takes all of the ISS modules combined to support seven crew.  So joining multiple Bigelow modules can produce some serious crew capacity.
It's oversimplifying a bit. You can cram a lot of sardines into a small can if they don't have to do anything.

To take ISS beyond its 7 person crew would require more frequent resupply and if those extra people want to do any meaningful science I believe it would exceed the station's power.
« Last Edit: 04/30/2015 02:28 PM by rayleighscatter »

Offline llanitedave

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Re: Seven crew members
« Reply #31 on: 05/01/2015 03:43 AM »
Yep, it's not just the size of the modules.  It's the size of the solar panels you'd need.  And the heat radiators.
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Offline baldusi

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Re: Seven crew members
« Reply #32 on: 05/01/2015 01:50 PM »
Yep, it's not just the size of the modules.  It's the size of the solar panels you'd need.  And the heat radiators.
And the ECLSS, and the supply runs, and the rack space for experiments, and then you have experiments that affect other experiments, and tourists jumping around ruin the microgravity environment of the crystallization experiments, etc.

Online A_M_Swallow

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Re: Seven crew members
« Reply #33 on: 05/01/2015 11:56 PM »
Yep, it's not just the size of the modules.  It's the size of the solar panels you'd need.  And the heat radiators.
And the ECLSS, and the supply runs, and the rack space for experiments, and then you have experiments that affect other experiments, and tourists jumping around ruin the microgravity environment of the crystallization experiments, etc.

I suspect that the tourist spacestation and the microgravity labratory will be separate spacestations. A long term lease of a BA-330 is not that expensive.

Offline baldusi

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Re: Seven crew members
« Reply #34 on: 05/02/2015 12:08 AM »
Yep, it's not just the size of the modules.  It's the size of the solar panels you'd need.  And the heat radiators.
And the ECLSS, and the supply runs, and the rack space for experiments, and then you have experiments that affect other experiments, and tourists jumping around ruin the microgravity environment of the crystallization experiments, etc.

I suspect that the tourist spacestation and the microgravity labratory will be separate spacestations. A long term lease of a BA-330 is not that expensive.
We are learning about living and working in LEO with the ISS. Once you know what is actually worth to do, and how to do it for cheap and standardized, I'm suspecting that the next batch of stations won't be a jack of all trades, but a series of cheap, highly automated smaller and standardized modules with each dedicated to a niche.

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