SpaceX Falcon 9/Dragon COTS Demo (C2+) GENERAL DISCUSSION

[cambrianera]

@Dave G
"I thought the trunk, interstage, and skirt were composite."
Actually the trunk is aluminium (don't ask me the reference, but look at the picture from manboy - reply 841 -)
Non-cylindrical shape makes it harder for composite.

[jnc]

Non-cylindrical shape makes it harder for composite.

I don't think so? I just consulted with my SO (who's a composite structures specialist with NASA), and her take was that in general the cross-section didn't make a big difference - modulo issues like dips and ridges, which could make it much trickier. All depends on the exact shape....

Noel

[cambrianera]

Never said impossible!
Spell it - harder -
Why spend more analyzing the fiber lay-down when you can get a good solution with good old stiffened aluminium!
X33 lesson was a hard one!

[corrodedNut]

The trunk is aluminium now. It was going to be composite, F9 flights 1 & 2 trunks (if you can call it that, more like a spacecraft adaptor) were. The actual trunk is constructed in a similar manner as Falcon 9's first and second stage fuel tanks. The solar array covers or pontoons are still composite, however.

[jnc]

Never said impossible!
Spell it - harder -

I never said impossible either - all I was saying was circular versus (say) oval cross-section is 'not a noticeable factor' for composites. (You did say "Non-cylindrical shape makes it harder for composite", which taken just as written, is not, I think, accurate.) There are some shape factors which make it harder, and I noted some (dips, ridges).

Why spend more analyzing the fiber lay-down when you can get a good solution with good old stiffened aluminium!

Well, that's a perfectly valid point. The modelling tools for composites (not to mention manufacturing technologies) are getting better all the time, but they still aren't as easy to use as those for isotropic materials.

Hey, it's an engineering tradeoff - composites have their advantages, but also disadvantages (such as that one). Depends on how important saving the mass is....

Noel

[cambrianera]

Thanks corrodedNut; I've readed it somewere in the mission coverage.
Fairly credible due to the changes in shape and the attach points of the pontoons (every hard point eats in the engineering margins of composites).
Pictures of the inside of the trunk made me sure of the Al construction (too many stiffeners for a composite)

[cambrianera]

@jnc
explaining everything in detail tends to be annoying, specially on internet.
Some posters here rely on answers declined on single digit words.
I'm not with them, but also I'm not so fluent in english to make long posts.
Anyway all is ok, we are here for fun, isn't it?

[IRobot]

Non-cylindrical shape makes it harder for composite.

I don't think so? I just consulted with my SO (who's a composite structures specialist with NASA), and her take was that in general the cross-section didn't make a big difference - modulo issues like dips and ridges, which could make it much trickier. All depends on the exact shape....

Noel

There are a lot of all-carbon fiber sailboats. They don't have cylindrical shape.

[corrodedNut]

Of all the possible reasons SpaceX might have for changing the design of the trunk, "we can't make this shape out of composites very easily" is probably not one of them.

[cambrianera]

Non-cylindrical shape makes it harder for composite.

I don't think so? I just consulted with my SO (who's a composite structures specialist with NASA), and her take was that in general the cross-section didn't make a big difference - modulo issues like dips and ridges, which could make it much trickier. All depends on the exact shape....

Noel

There are a lot of all-carbon fiber sailboats. They don't have cylindrical shape.

And car frames, and aircraft parts, and more.....
You can spend a lot of money squeezing every single gram on components of your system and composites are a real wonder for this.
But when reliability, cost, complexity and low production numbers kicks in, you are left with few choices.
On the other side, you can buy very cheap composite fishing rods nowadays.

This is fun, in another thread someone called me unrealistic, now I'm playing the other side.....

[cambrianera]

Of all the possible reasons SpaceX might have for changing the design of the trunk, "we can't make this shape out of composites very easily" is probably not one of them.

Time wasn't paramount for them?
And reliability?
Composite tends to have very unusual failure modes (unusual because our actual engineering "usual" is about metals!)

[jnc]

@jnc
explaining everything in detail tends to be annoying, specially on internet.

Yes, but engineering is all about details - and this site is for the people who understand the details!

I'm not so fluent in english to make long posts.

Not a problem...

Anyway all is ok, we are here for fun, isn't it?

Yes, as they say in English, 'We seem to be having a violent agreement!'

Noel

[corrodedNut]

Do we have a timeline for Thursday's departure and reentry yet? AFAIK unberthing is 6:00 am ET, deorbit burn and reentry within a few hours later.

[jabe]

Do we have a timeline for Thursday's departure and reentry yet? AFAIK unberthing is 6:00 am ET, deorbit burn and reentry within a few hours later.

mentioned a few times here
http://forum.nasaspaceflight.com/index.php?topic=28991.msg907140#msg907140

[JimP]

Do we know where Dragon will be unloaded?  Where/when residual prop will be removed?

[yg1968]

This may have been posted already but SpaceX received some Congratulations for berthing to the ISS:
http://www.whitehouse.gov/blog/2012/05/25/space-community-leaders-historic-berthing-dragon-international-space-station

Here is an op-ed by Mark Kelly that is very favorable to commercial crew and cargo:
http://articles.orlandosentinel.com/2012-05-27/opinion/os-ed-space-program-mark-kelly-052712-20120525_1_spacex-dragon-space-program-commercial-spaceflight

[Jim]

Do we know where Dragon will be unloaded?  Where/when residual prop will be removed?

VAFB for destow and probably the Sealaunch facilities for prop unloading

[SpacemanInSPACE]

Is there a chance at any point after splashdown that the dragon will be on display by the public before being sent to Hawthorne? I live nearby and wanted to catch a glimpse if possible.

[SpacexULA]

Is there a chance at any point after splashdown that the dragon will be on display by the public before being sent to Hawthorn? I live nearby and wanted to catch a glimpse if possible.

People did see the COTS craft come into port, the images are in this forum somewhere.

I would not be surprised if the same happens again.

[ugordan]

Is there a chance at any point after splashdown that the dragon will be on display by the public before being sent to Hawthorn?

Before Hawthorne? Not likely. They will most certainly partially disassemble the capsule for postflight analysis just like they did for C1. Once that's done they may put it back together and have it go around for displays.