Author Topic: Difference in PV area between B330 and ISS  (Read 2515 times)

Offline high road

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Difference in PV area between B330 and ISS
« on: 07/18/2016 12:58 PM »
I was wondering why there is such an enormous difference in size between the solar panels that are currently on the ISS, and the Bigelow B330 drawings. 3 B330 modules would have the same amount of useful pressurized space as the entire ISS. Even for concept art, they should be attempting to at least approximate the actual power requirements, right?

1) Is it that a more compact space station requires much less power?
2) Does a 'space hotel', which the B330 is supposed to become, require much less power than a research station?
3) The B330 design process migh only be at the point of testing the inflatable envelope itself, not the actual module or electronic subsystems, so even they haven't even begun to make a decent estimate of power requirements.

Is there a breakdown of the power requirements of the ISS in L2? It's a bad idea to renew my L2 subscription before I've finished refurbishing my place, but it'll be good to know it's there once I start designing again.
« Last Edit: 07/18/2016 12:59 PM by high road »

Offline RonM

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Re: Difference in PV area between B330 and ISS
« Reply #1 on: 07/18/2016 03:58 PM »
Space rated solar panels today are about 50% more efficient (Juno spacecraft versus ISS).

Don't know if the panels shown in the B330 images is artistic license or not, but they wouldn't have to be as big as the ISS panels for the same power requirement.

Offline the_other_Doug

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Re: Difference in PV area between B330 and ISS
« Reply #2 on: 07/19/2016 06:52 PM »
Also, ISS is power-hungry.  It has a lot of experiment racks that are pulling power at any given time, plus redundant sets of ECLSS, monitoring systems, comm systems, lighting and annunciation systems, the list goes on and on... all designed to operate in what's supposed to be a power-rich environment.

Note that when ISS loses one of its redundant power strings, they have to shut down a third to a half of the equipment drawing power, including many of the experiment racks.  It can be reconfigured, and AIUI you can add more sources to the remaining string until you get the second string back.  But you lose some power no matter what while operating on just one string.

I bet the total power budget being considered for a Bigelow station, as pictured, is mainly to cover basic things like ECLSS and lighting.  Any experiment packages are gonna need to provide their own power, or operate in such a way as to use what little is left over from the aforementioned budget...
-Doug  (With my shield, not yet upon it)

Online Robotbeat

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Re: Difference in PV area between B330 and ISS
« Reply #3 on: 07/19/2016 09:14 PM »
I wouldn't take B330 pictures as anything more than notional.

But yeah, the arrays are old now and had low efficiency (by today's standards) when they started.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Orbital Debris

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Re: Difference in PV area between B330 and ISS
« Reply #4 on: 09/02/2016 02:42 PM »

3) The B330 design process migh only be at the point of testing the inflatable envelope itself, not the actual module or electronic subsystems, so even they haven't even begun to make a decent estimate of power requirements.

Is there a breakdown of the power requirements of the ISS in L2? It's a bad idea to renew my L2 subscription before I've finished refurbishing my place, but it'll be good to know it's there once I start designing again.

It's number 3.  The drawings are conceptual, done by a graphic artist to please RTB, and have not been vetted by the engineers usually.  Here is a typical meeting of the engineers: 
ECLSS mgr: We need 5kw to power the electrolyzer to break water
Power: 5 kw?  I cant get 5 kw to power the entire spacecraft!
Thermal: I canít reject 5 kw of heat!
Structures: Doesnít matter, I canít pack 5 kw of arrays anyway, it is all fictitious
PM: Wait, we donít have enough power?

I'm paraphrasing, but yes that conversation really happened a few years ago.  It was so incredible, it is burned into my memory.  One of the engineers facetiously scaled a drawing for the 'notional' power requirements and the arrays dwarfed the  softgoods portions.

Offline Patchouli

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Re: Difference in PV area between B330 and ISS
« Reply #5 on: 09/03/2016 05:13 AM »
Actually the size of the arrays and radiators in later artwork is not that unrealistic compared to a pic of Salyut 6.

The full sized multi module station has large solar arrays.
« Last Edit: 09/03/2016 05:18 AM by Patchouli »

Offline high road

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Re: Difference in PV area between B330 and ISS
« Reply #6 on: 09/03/2016 12:23 PM »
Thx for that picture. This means the 'two BA330 modules connected together' actually require support modules to be a functioning space station. I prefer the design with the service module in the middle and the solar panels perpendicular to the modules,  but that's a different discussion.

Offline Jim

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Re: Difference in PV area between B330 and ISS
« Reply #7 on: 09/03/2016 12:33 PM »
. I prefer the design with the service module in the middle and the solar panels perpendicular to the modules,  but that's a different discussion.

Why would you think they have fixed orientations?  They rotate while the stations attitude remains fixed.

Offline high road

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Re: Difference in PV area between B330 and ISS
« Reply #8 on: 09/03/2016 05:15 PM »
My reply wasn't power related. The solar panels will have to track the sun no matter what the configuration of the station is.

What I mean is that I would design the station more 3-dimensional: Start with a backbone of service modules along the z-axis (starting with two, add more if demand increases) which handle station keeping, docking, berthing, EVA, and any other tasks required for operating a space station, connect the B-330's along the x-axis and the solar panels, radiators, outside experiment racks and whatever you want along the y-axis. Everything nice and cumfy together along all three axes, so whatever debris-evasion maneuvers that need to be done require as little fuel and vehicle strength as possible, and no B-330 modules has to be equiped to dock (at least after initial installment) with incoming spacecraft, let alone berth one.

But as I said, that's another discussion.

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