Author Topic: Bigelow for Falcon Heavy (Read 17097 times)

joek · « **Reply #20 on:** 04/12/2011 09:04 pm »

Quote from: Lampyridae on 04/12/2011 08:17 am

---snip---
The original Transhab development indicated the wall mass was about 12kg/m^2.

Based on ISS inflatable mission numbers that appears to have grown to ~20-24kg/m^2... inflatable shell ~2916-3499kg; inflatable surface area ~143m^2 (~158m^2 total - ~14m^2 core ends).

alexterrell · « **Reply #21 on:** 04/13/2011 02:44 pm »

By comparison, 1cm of Aluminum would mass 27kg/m2.

The Transhab wall looks a good 30cm thick.

docmordrid · « **Reply #22 on:** 04/13/2011 06:42 pm »

And Bigelow has said their modules are 16" (40.64 cm) thick.

joek · « **Reply #23 on:** 04/14/2011 03:57 am »

That's consistent with NASA's numbers with MMOD bumper layers (which appear to account for a significant portion ) stated variously as "<16in" and "<0.5m".

alexterrell · « **Reply #24 on:** 04/14/2011 07:57 pm »

so if we assume carbon based materials (like Kevlar) at about 1.5g/cm3, then the Bigelow wall is 2cm of material and 38cm of vacuum or air. I assume there's one air tight membrane near the inside and most of the mass is out side of this.

Would most of the filler therefore be vacuum? If it's air, there's a problem with outgassing. If it's vacuum, there's a problem with expanding it?

docmordrid · « **Reply #25 on:** 04/14/2011 11:44 pm »

There are several redundant air bladders and IIRC the walls are foam filled.

joek · « **Reply #26 on:** 04/15/2011 12:05 am »

Quote from: alexterrell on 04/14/2011 07:57 pm

so if we assume carbon based materials (like Kevlar) at about 1.5g/cm3, then the Bigelow wall is 2cm of material and 38cm of vacuum or air. I assume there's one air tight membrane near the inside and most of the mass is out side of this.

Would most of the filler therefore be vacuum? If it's air, there's a problem with outgassing. If it's vacuum, there's a problem with expanding it?

There approximately "two dozen" layers (see attachment), multiple bladders, thermal and MMOD protection, and several different materials. Most the volume appears to be MMOD protection layers. TransHab used Nextel + open cell foam; assume Bigelow's structure is similar.

From TransHab: NASA's Large-Scale Inflatable Spacecraft, AIAA 2000-1822:

Quote

On orbit, in the vacuum of space, the foam regains its original standoff thickness due to the resilience of the foam.

So in a sense, yes, the outer shell is largely vacuum.

edit: add image.

joek · « **Reply #27 on:** 04/17/2011 12:14 am »

Quote from: Jason1701 on 04/10/2011 10:25 pm

A 6m fairing on the 3.66m core might pose stability problems. Does anyone know the fairing-to-core ratio on the hammerhead ELVs?

The "How big a fairing?" seems to be a recurring question in several threads. I don't have a simple answer for FH, but a couple points of reference...

Atlas V Launch Services User’s Guide, ULA, Mar 2010 (pg 8-1):

Quote

ULA has considered payload fairings as large as 7.2 m (283 in.) in diameter and up to 32.3 m (106 ft long), as shown in Figure 8.1-1. These larger fairings, which are limited to flying on Atlas V configurations of up to four solid rocket boosters (SRBs), require moderate vehicle changes and modifications to the launch pad, limited mostly to secondary vertical processing facility structure.

http://www.ulalaunch.com/site/docs/product_cards/guides/AtlasVUsersGuide2010.pdf

Delta IV Payload Planners Guide, ULA, Sep 2007 (pg 10-11):

Quote

Payload fairings as large as 6.5 m (255 in.) in diameter and up to 25.9 m (85 ft long), as shown in Figure 10-13, have been evaluated and appear feasible. Larger fairings would require modest vehicle changes and modifications to the launch pad, limited mostly to secondary MST structure.

http://www.ulalaunch.com/site/docs/product_cards/guides/DeltaIVPayloadPlannersGuide2007.pdf

...I'll leave it to someone with more chops in aerodynamics to elaborate.

docmordrid · « **Reply #28 on:** 04/17/2011 12:49 am »

3.66m core for F9 and a 3.81m core for Atlas V - less than 6" difference. Do our engineers think that if kept in proportion to core diameter something akin to the above could work?

joek · « **Reply #29 on:** 04/17/2011 01:28 am »

Quote from: docmordrid on 04/17/2011 12:49 am

3.66m core for F9 and a 3.81m core for Atlas V - less than 6" difference. Do our engineers think that if kept in proportion to core diameter something akin to the above could work?

Maybe for F9, but FH is very different. Note:
1. Atlas V (smaller core) but larger PLF than Delta IV (larger core). Counterintuitive?
2. Atlas V larger PLF caveat on number of SRB's.
3. Delta IV larger PLF is shown only on Delta IV Heavy. Significance is unknown.

I can only opine that my past (limited and dated) experience suggests that simple core/PLF rations are inadequate, and that when the the booster is anything other than relatively clean cylinder such as with strapons larger PLFs can be much more of a problem. Will leave elaboration to someone with more aerodynamic chops and/or better CFD tools.