Oolite Bulletins

Designer Burt Rutan, billionaire Paul Allen, rocketman Elon Musk and former NASA boss Mike Griffin are teaming to develop an air-launch rocket system that would use a super aircraft the size of two 747s to carry a liquid-fueled SpaceX booster to 30,000 feet where it would be dropped to fire hardware and humans into orbit.

Read more at Spaceflight Now.

+checks calender+

Nope. it's not the first of the fourth month...


So... virtually *all* the bigger contenders in the altspace community forging an alliance?

Not sure I like that.

Call me a worry wart if you like, but I see some inherent risk in that project. The design of the plane looks flimsy to say the least. A catamaran design supported ONLY by the span of the wing would be quite unstable. Slinging a heavy rocket underneath it would create huge stresses on that structure, specially when the rocket is released. How stable would it be under turbulent conditions? The landing would have to be spot on every time, since even a one degree divergence from horizontal would make a big difference between when each set of landing gear hit the ground and again the stresses on the wing roots may be a failure point in these conditions, especially when bearing the weight of three 747 engines apiece. Can the relatively small tail surfaces contain any control surfaces? If so they will be relatively small for the size of the aircraft and would have to be perfectly synchronised through two separate sets of control cabling. I can't see it being the most responsive beast ever made.

The rocket is a three stage monster too, the same sort of technology that has been used for years to achieve ground-based launches. Are the two transport stages recoverable? If not then you have huge costs to replace them for every launch. If not there's a comparable cost for recovery.

Is bigger still better these days? Custom hangars would cost a fair bit too, and all of that would drive the cost of using the plane upwards and push them out of the market if they're not careful.

I've seen other, more cost effective methods of launching rockets. The tried and tested way already has the infrastructure in place and would cost nothing, and I can't see anyone shelling out the readies to use something like this when they're all trying to save money. The fact that NASA canned ATK as a contractor to save money is a sign that the customers are looking for savings, not outlay on something that is radically different and would need a whole new support infrastructure.

Selezen wrote:

The design of the plane looks flimsy to say the least. A catamaran design supported ONLY by the span of the wing would be quite unstable. Slinging a heavy rocket underneath it would create huge stresses on that structure, specially when the rocket is released.

The design has already been proved. The design for White Knight One/Spaceship One which won the Ansari X-Prize, has already been scaled up into White Knight Two/VSS Enterprise.

White Knight Two has recently completed a whole series of drop tests, with no serious issues. Now all that remains is the final few tests before commercial sub-orbital operations commence, early next year.

Interesting that they say "747 engine"

No such thing of course, at least not from Boeing. Engines are made by companies like Rolls Royce and General Electric for fitting to aircraft, and the same types of engines may be used across multiple aircraft. Perhaps a bit of protectionism there? Couldn't possibly have an Airbus engine could it!

Looks like fun though!

Cheers,

Drew.

Personally I'm a fan of the lifting torus design. More balloon than aircraft but the principle is the same.

JazHaz wrote:

The design has already been proved. The design for White Knight One/Spaceship One which won the Ansari X-Prize, has already been scaled up into White Knight Two/Virgin Galactic Enterprise.

White Knight Two has recently completed a whole series of drop tests, with no serious issues. Now all that remains is the final few tests before commercial sub-orbital operations commence, early next year.

WK2 has a wingspan of 140ft, whereas this beast has a wingspan more than three times that. Yes, the design has been proved but this looks to be a "see how far we can go" experiment with scaling that design.

I don't know the internal structural principles of the wing design so I could obviously be wrong, but I would hesitate to say that just because something works on one scale it necessarily follows that it will work on a larger scale.

My bigger issue with it is the spiralling cost of commercial space flight each time someone takes a design and "scales it up". The WK2/SS2 concept is good and could bear real fruit, like commercial passenger travel and the lifting of a small manned shuttle into space, but taking that concept and using it to launch a rocket is a bit barmy.

Typical Microsoft-funded "bloatware" if you ask me.

wonder if microsoft will provide any software. could be interesting coming back down. "retrorockets.exe has encountered a problem and needs to close" =8-O

Or this on the final descent
"Windows has been updated and will automatically restart in 10...9...8..."

On other experiences...
In '98, there was the Yorktown NT debacle.
Up to until 2008, some had learnt their lessons (the USN moved on to Linux), but others apparently didn't!

Selezen wrote:

WK2 has a wingspan of 140ft, whereas this beast has a wingspan more than three times that. Yes, the design has been proved but this looks to be a "see how far we can go" experiment with scaling that design.

I don't know the internal structural principles of the wing design so I could obviously be wrong, but I would hesitate to say that just because something works on one scale it necessarily follows that it will work on a larger scale.

Back to the topic:

I agree with Selezen simply because of physics.

The square-cube law states that if you double the length of a cube's edge, its surface area is squared and its volume, cubed.

Since aerodynamic lift is a function of the surface area but weight is a function of volume, tripling the size of a plane could increase its lift by the square of the multiplier (lift x9), but would also cube its mass (weight x27). In all, the lift/weight ratio not only doesn't remain the same, but is reduced to 1/3 of the original...