VgGalactic press release thread

[Vfor]

Anyone familiar with Kevlar composites recognizes them on sight.
 
http://www.virgingalactic.com/pressftp/content/Photographs/SpaceShipTwo%20Construction/SpaceShipTwo%20Construction.%20wing%20assembly.jpg

In this construction photo of SpaceShipTwo, you can see where although the crew cabin and tailcone are carbon fiber the center section is Kevlar.

Is that their big plan for dealing with the explosion potential of nitrous oxide because they have no clue what kind caused the July 2007 explosion or any idea what to do about it?

[Blackstar]

CuddlyRocket - 24/1/2008  4:46 AM
Intersting that they're already thinking of different markets for the system. I'm sure there'll be a demand for experimental use (especially if the experimenters get to go up with their experiments!).

It would be interesting to compare it to sounding rockets.  Is its flight time and altitude similar to a sounding rocket, and what's the price comparison?  Makes me wonder if it could eventually be a good choice for NASA and DoD sounding rockets.  I think there's a lot of variables to look at, including the fact that it could carry larger payloads and recover them (not always possible with current payloads).

[Vfor]

Blackstar - 24/1/2008  8:39 PM

CuddlyRocket - 24/1/2008  4:46 AM
Intersting that they're already thinking of different markets for the system. I'm sure there'll be a demand for experimental use (especially if the experimenters get to go up with their experiments!).

It would be interesting to compare it to sounding rockets.  Is its flight time and altitude similar to a sounding rocket, and what's the price comparison?  Makes me wonder if it could eventually be a good choice for NASA and DoD sounding rockets.  I think there's a lot of variables to look at, including the fact that it could carry larger payloads and recover them (not always possible with current payloads).

One application that springs to mind is as a testbed for high altitude emergency egress equipment (ejection seats and space suits), picking up where Joe Kittinger left off.

[Vfor]

meiza - 23/1/2008  4:57 PM

Could someone knowledgeable in the composite business explain about the build process?
http://www.virgingalactic.com/pressftp/content/Photographs/SpaceShipTwo%20Construction/SpaceShipTwo%20Construction.%20wing%20assembly.jpg
What's the black material? And the yellow section?

Black is carbon fiber. Yellow is Kevlar.

The question is, why are they making the section that houses the oxidizer tank out of Kevlar instead of carbon fiber?

[meiza]

Vfor, it was explained a few posts up from here. The oxidizer tank stretches so the fuselage must be of the same material to stretch too, and they say it's glass fibre in the Economist article.

[Vfor]

meiza - 25/1/2008  2:58 AM

Vfor, it was explained a few posts up from here. The oxidizer tank stretches so the fuselage must be of the same material to stretch too, and they say it's glass fibre in the Economist article.

The photos show a Kevlar fuselage section, not fiberglass. If there is an expansion issue, you just build the fuselage big enough in the first place to accomodate the expanded oxidizer tank. Since you can do that just as well with carbon fiber, why are they building that fuselage section out of bulletproof Kevlar?

[meiza]

Ah Vfor, the plot thickens... Maybe it's Kevlar overlay on glass fiber. Kevlar is very stretchy so it should have no problem.
Here's what a glass fiber tank looks like
http://media.armadilloaerospace.com/2003_05_25/tankcoupling.jpg

Why they don't have separate structures? That's a good question. Maybe that could be a bit less mass efficient. I presume now the ox tank is attached to the body and the fuel/chamber/throat/nozzle is attached to the tank. Could even dampen vibrations. But the afterbody is attached to the tank as well. I don't know about the aft part of the wing.
That could create tensions. Maybe the tank only bulges radially.
A weird design decision.

[Vfor]

meiza - 25/1/2008  7:35 AM

Ah Vfor, the plot thickens... Maybe it's Kevlar overlay on glass fiber. Kevlar is very stretchy so it should have no problem.
Here's what a glass fiber tank looks like
http://media.armadilloaerospace.com/2003_05_25/tankcoupling.jpg

Why they don't have separate structures? That's a good question. Maybe that could be a bit less mass efficient. I presume now the ox tank is attached to the body and the fuel/chamber/throat/nozzle is attached to the tank. Could even dampen vibrations. But the afterbody is attached to the tank as well. I don't know about the aft part of the wing.
That could create tensions. Maybe the tank only bulges radially.
A weird design decision.

As for the plot thickening, maybe the reason they're using Kevlar is because they haven't found a solution to the problem of nitrous oxide self-detonating (because there isn't one), so instead of sacrificing money and schedule to a redesign that replaces nitrous oxide with an oxidizer that doesn't explode they're attempting to make their current system workable by armoring SpaceShipTwo with Kevlar.

[aero313]

CuddlyRocket - 24/1/2008  4:10 PM
...It's just Branson making the company seem as green as possible (to address those environmental concerns).

That was my point - make the company SEEM green, as opposed to actually reducing emissions.  Sort of like the automakers who strive for the PERCEPTION of quality, instead of just building a quality product.

[JMS]

Don't you guys think you're being a bit tough on Richard?

[8900]

Vfor - 26/1/2008  6:28 AM

As for the plot thickening, maybe the reason they're using Kevlar is because they haven't found a solution to the problem of nitrous oxide self-detonating (because there isn't one), so instead of sacrificing money and schedule to a redesign that replaces nitrous oxide with an oxidizer that doesn't explode they're attempting to make their current system workable by armoring SpaceShipTwo with Kevlar.

NO oxidizer in completely safe
LOx can explode, N2O4 is even much more dangerous, H2O2 is better but still, it is dangerous
the oxidizer itself is not the problem, the problem is can we improve the procedure to handle
it so that it can be used rather safely
trying to re-creating the explosion scene should be useful in determining the root cause
Given correct precautions and procedures, even the most dangerous N2O4 can be handled safely
Kevlar shield is backup, so that even in worse case scenario explosion did occur, the SS2 can
have a better chance to survive

[HMXHMX]

Uh, LOX can't explode.

Having used many tons of H2O2 I can say with some assurance it can sure act like an explosive even if it doesn't meet the textbook definition of one.

Nitrous most certainly can detonate, though initiation is challenging.  It is a monopropellant, like hydrazine, which can also detonate.

There is no "Kevlar shield" on SS2.  It is not a shield; that is a misperception.  And even if it were, a review of the July accident site shows it would be of no value whatever if the main propellant tank goes high order.

[Vfor]

HMXHMX - 25/1/2008  10:30 PM

Uh, LOX can't explode.

Having used many tons of H2O2 I can say with some assurance it can sure act like an explosive even if it doesn't meet the textbook definition of one.

Nitrous most certainly can detonate, though initiation is challenging.  It is a monopropellant, like hydrazine, which can also detonate.

There is no "Kevlar shield" on SS2.  It is not a shield; that is a misperception.  And even if it were, a review of the July accident site shows it would be of no value whatever if the main propellant tank goes high order.

Let's hope traps designed to prevent detonation waves from propagating back to the main tank are installed and are effective.

[jabe]

from space.com
scary the similarity of design

[Comga]

jongoff - 24/1/2008  11:02 AM

Comga,

Has anyone found in the release the loaded mass of SS2?  It would be interesting to compare it to a Pegasus and the proposed t-Space Quickreach.  The release does mention using White Knight 2 for this kind of operation.

I've been curious about such things myself (particularly due to my recent interest in Air-Launched RLVs), so I did a little digging.  What I found wasn't as enlightening as I hoped, but here's what I have:
http://selenianboondocks.blogspot.com/2008/01/mass-confusion-and-white-knight-2.html
Short version:
Will Whitehorn has publicly given the payload capacity of WK2 on two different occasions (one in at a presentation at Oshkosh this year, and one to Rob Coppinger of Flight Global).  Unfortunately the two numbers don't match.  One was 30,000lb, one was ~30 tons (or tonnes)..... Alas, I fear the smaller number is the right one.  If so, it wouldn't be able to do much more than microsat launches, which as Aero313 put it, doesn't really look like that lucrative of a market.
~Jon

Your own link to Rob Coppinger's Flight Global blog, Hyperbola, http://www.flightglobal.com/blogs/hyperbola/2008/01/white-knight-ii-could-launch-o.html
is adamant about the 13,600 kg / 30,000 lb capacity.  This can be compared to the Pegasus XL, which has a mass of 23,130 kg.  Although the launch altitude would be higher, 60 kft vs 40 kft IIRC, it would be hard to maintain the same relative performance, which would result in something like 200 kg to LEO.   This is pretty small, microsats, as you say, the range of co-manifested secondary satellites, and pretty far from any established market, as you also said.  

Burt Rutan is not "on a mission" like Elon Musk.  Unless someone pays, he won't build.  

Launching payloads from WKII seems like more silliness like VG's environmental sensitivity.
Perhaps we can save the planet by launching 200 kg servers to a LEO belt, where they will be powered by environmentally benign solar cells. :bleh:

On the other hand, there will be science done from SS2.

[8900]

Let's talk about the design
Who think the newly unveiled design is more "cool" than the original concept?

[MKremer]

I know Rutan designs mostly for "form follows function", but these new designs strike me as being more 'traditional' than the original WK/SS1 designs. (WK - fusilage/tailplane design, wing-mounted engines ; SS2 - fusilage design with elongated nose)

[AntiKev]

Vfor - 25/1/2008  6:28 PM
As for the plot thickening, maybe the reason they're using Kevlar is because they haven't found a solution to the problem of nitrous oxide self-detonating (because there isn't one), so instead of sacrificing money and schedule to a redesign that replaces nitrous oxide with an oxidizer that doesn't explode they're attempting to make their current system workable by armoring SpaceShipTwo with Kevlar.

It also looks like that area is where the main spar pass through is.  The kevlar could help with bending loads transferred to the fuselage from the wing spar.

[Rob in KC]

8900 - 28/1/2008  8:18 AM

Let's talk about the design
Who think the newly unveiled design is more "cool" than the original concept?

There's nothing cool about this. It's a suborbital joyride.

[antonioe]

Rob in KC - 28/1/2008 9:50 AM

8900 - 28/1/2008 8:18 AM Let's talk about the design Who think the newly unveiled design is more "cool" than the original concept?

There's nothing cool about this. It's a suborbital joyride.

Well, I think it is very cool.  I will sign up for a ride if I find I can afford it.  At $20K I'd buy a ticket right now.  At $50K I would have to think hard about it.  At $100K, I can't afford it.

I know - alas! - I'll never be able to afford a ride to orbit.  But black sky, Mach 3.5 and 100 km will let me die in peace.