Author Topic: General Falcon and Dragon discussion (Thread 12)  (Read 290187 times)

Offline Burninate

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #20 on: 02/26/2015 07:52 AM »
Can water be transported in a special container in the unpressurised trunk?
I believe that was the method in ATV.
Seems like a waste of much needed volume to put it in bags inside the small capsule.
Water weighs 1 ton per cubic meter.  It's a solid material rather than hollow cases & circuit board racks.  It's the heaviest thing per volume around.

Online guckyfan

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #21 on: 02/26/2015 07:55 AM »
Water weighs 1 ton per cubic meter.  It's a solid material rather than hollow cases & circuit board racks.  It's the heaviest thing per volume around.

I doubt that after packing the water to NASA standards this will still be true.

Offline rpapo

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #22 on: 02/26/2015 10:20 AM »
Water weighs 1 ton per cubic meter.  It's a solid material rather than hollow cases & circuit board racks.  It's the heaviest thing per volume around.
It's the densest consumable the ISS needs in significant quantities.  It is -far- from the heaviest [per volume] thing around.  If it were, ships would never sink in it.

It has the advantage, however, of being highly recyclable, so the ISS only needs to replenish what gets wasted.  If the ISS didn't have extreme recycling going on, they would require far more supplies than they currently do.
« Last Edit: 02/28/2015 05:12 PM by rpapo »
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Offline eischei

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #23 on: 02/28/2015 04:36 PM »
The thought about the Aerospike came to me as well. I have in mind that the russian N1 experienced a certain performance gain, only because of the arangement of the engines (no source though).

Could Falcon 9 1.1 have a similar advantage?

Regards,

Sepp

Offline TomH

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #24 on: 02/28/2015 04:40 PM »
Water weighs 1 ton per cubic meter.  It's a solid material rather than hollow cases & circuit board racks.  It's the heaviest thing per volume around.
It's the densest consumable the ISS needs in significant quantities.  It is -far- from the heaviest thing around.  If it were, ships would never sink in it.

It has the advantage, however, of being highly recyclable, so the ISS only needs to replenish what gets wasted.  If the ISS didn't have extreme recycling going on, they would require far more supplies than they currently do.

He didn't say it was the heaviest thing around. He said, It's the heaviest thing around per volume. That's exactly what density is. I understood him to mean the same thing as you-the densest consumable in significant quantities.
« Last Edit: 02/28/2015 05:08 PM by TomH »

Offline dror

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #25 on: 02/28/2015 06:02 PM »
Can water be transported in a special container in the unpressurised trunk?
I believe that was the method in ATV.
Seems like a waste of much needed volume to put it in bags inside the small capsule.
Water weighs 1 ton per cubic meter.  It's a solid material rather than hollow cases & circuit board racks.  It's the heaviest thing per volume around.

That's Irrelevant, it's still a wasted volume in the cabin and dragon is volume limited.
If they need to certify a water container, a barrel in the trunk seems like a good alternative.
The biggest disadvantage may be the crew time needed to unpack it with the robotic arm.
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Offline rpapo

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #26 on: 02/28/2015 06:14 PM »
That's Irrelevant, it's still a wasted volume in the cabin and dragon is volume limited.
If they need to certify a water container, a barrel in the trunk seems like a good alternative.
The biggest disadvantage may be the crew time needed to unpack it with the robotic arm.
Yes, Dragon is volume limited.  Which means that if they can choose to load it up with denser stuff (like water) and still have an adequate payload weight margin.  What that would do to their margins for returning the first stage, I cannot say.

With regards to an external tank, does the ISS have an external connection for receiving water?  As far as I know, it does not.  Such an external tank would have to be carried over to the Quest airlock and brought in through there.  In other words, it would have to be small enough to fit through the door there.  The other airlock doors are smaller.

Schedule an EVA to receive can(s) of water?  I find that hard to imagine happening except in a dire emergency.
« Last Edit: 02/28/2015 06:18 PM by rpapo »
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Offline Jim

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #27 on: 02/28/2015 06:31 PM »

That's Irrelevant, it's still a wasted volume in the cabin and dragon is volume limited.
If they need to certify a water container, a barrel in the trunk seems like a good alternative.
The biggest disadvantage may be the crew time needed to unpack it with the robotic arm.


What good is using the arm and "unpacking" it? It has no way of getting inside.  The ATV was plumbed for water transfer.  The Dragon is not, and that is a major mod.  So, containers on the inside is the simpler method.

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #28 on: 02/28/2015 06:45 PM »
One could imagine water tanks outside the pressure vessel but inside the capsule envelope with a port inside the pressurized portion where water vessels could be filled up by astronauts. But this is a mod of Dragon and likely non-trivial.
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Offline BobHk

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #29 on: 02/28/2015 10:52 PM »
I've been looking for the total water capacity of ISS and ran across this:

http://www.water-technology.net/projects/iss_water_recovery/
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110012703.pdf

The WRS reduced total water launch needs by 6.8t per annum. 


Offline the_other_Doug

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #30 on: 03/01/2015 03:30 AM »
Also please recall how the Shuttle would deliver water to the ISS.  Especially since at least some of the water the Shuttle delivered was being generated real-time by its fuel cells.

The Shuttle docking system was not plumbed to replenish the station's water tanks.  They used bags for water transfer.  Lots and lots and lots of bags.  (Or jugs, same difference, but mostly soft-sided bags.)  Some were pre-loaded on the ground before launch, others were filled from the fuel cell potable water system real-time.

So, it's not unprecedented in the slightest degree to pack a supply ship full of bags or jugs of water for transfer to the station.  It's not like it hasn't been done before.  (You just don't want to do a lot of maneuvering with a lot of half-full jugs of water on board.  Ever hear of fuel slosh?  It caused really significant controlability issues on the first two manned lunar landings...)
-Doug  (With my shield, not yet upon it)

Offline Lars-J

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #31 on: 03/02/2015 03:53 AM »
A tweet from Musk about F9 performance upgrades coming soon: (we already knew about the densification and M1D thrust upgrade, but the upper stage stretch(?) is new)

https://twitter.com/elonmusk/status/572257004938403840

Quote
Elon Musk ‏@elonmusk
Upgrades in the works to allow landing for geo missions: thrust +15%, deep cryo oxygen, upper stage tank vol +10%

Offline docmordrid

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #32 on: 03/02/2015 04:04 AM »
At what point does it graduate to v1.2?
DM

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #33 on: 03/02/2015 04:12 AM »
So if S2 is ~14m, this is a ~1m stretch. How significant is this for GSE, can they support this by just lengthening some umbilicals for the payload, or do they have to do more?

Offline Lars-J

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #34 on: 03/02/2015 04:14 AM »
So if S2 is ~14m, this is a ~1m stretch. How significant is this for GSE, can they support this by just lengthening some umbilicals for the payload, or do they have to do more?

1m is probably not a big deal. And the T/E is modular. I would assume that they want to put all of these modifications in use before FH flies. This might give even more benefit for FH.

Online Robotbeat

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #35 on: 03/02/2015 04:15 AM »
At what point does it graduate to v1.2?
Actually, I don't think this is nearly the level of v1.0->v1.1 (which really should've been 1.5 or 2.0, now that we know the magnitude of the changes).

At first, I thought it was a stretch of the first stage tanks not the second. I think stretching the upper stage is less of a big deal because the upper stage is much smaller to begin with, though it should help the performance significantly (especially to high energy).

The propellant densification (i.e. deep cryo LOx) is an interesting upgrade.
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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #36 on: 03/02/2015 04:16 AM »
Actually, upper stage tank volume +10% does not necessarily mean the outer structure needs to be stretched. A good example is the good old Ariane 4 - its LH2 third stage was modified twice in history (first flight 1988, first modification in 1992 and the second in 1994) to allow for slight increases in the fuel capacity with just internal tank stretches of inches. Each stretch brought about 100-150 kg increase in GTO payload capacity.

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Online meekGee

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #37 on: 03/02/2015 04:43 AM »
At first, I thought it was a stretch of the first stage tanks not the second. I think stretching the upper stage is less of a big deal because the upper stage is much smaller to begin with, though it should help the performance significantly (especially to high energy).


Not sure.  This is on the tank that gets to orbit.  I think it represents a lot more dV compared with a first stage stretch.

It gets carried by the first stage, unused, until staging.  Then it gets carried by the second stage until it is "1 m from empty" - and then you have 10% of the second stage pushing a practically empty stage.

The stretch will also reduce the stage velocity by a tad (the other changes not withstanding of course)
ABCD - Always Be Counting Down

Online meekGee

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Re: General Falcon and Dragon discussion (Thread 12)
« Reply #38 on: 03/02/2015 04:52 AM »
A tweet from Musk about F9 performance upgrades coming soon: (we already knew about the densification and M1D thrust upgrade, but the upper stage stretch(?) is new)

https://twitter.com/elonmusk/status/572257004938403840

Quote
Elon Musk ‏@elonmusk
Upgrades in the works to allow landing for geo missions: thrust +15%, deep cryo oxygen, upper stage tank vol +10%

I just posted this as my congratulation comment on the live thread:
Quote
Here's to a year that's boring when it's supposed to be boring and still exciting when it's supposed to be exciting...

Well...  I got what I wished for... 

Changes like this probably also factor into the decision to hold off on FH.  When it finally flies, all these changes would have had to be qualified only once.
ABCD - Always Be Counting Down

Offline TrevorMonty

Re: General Falcon and Dragon discussion (Thread 12)
« Reply #39 on: 03/02/2015 05:30 AM »
Besides the extra 10% tankage also expect deep cryo oxygen of upper which may give closer to 20% increase in fuel. The extra performance in 1st stage shouldn't have any problems lifting it.

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