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WELCOME TO THE WEIRD… and wonderful!

February 19, 2017


I have a problem here.  Last week we discovered a weighty problem with our fuel load, and we are unlikely to cram enough into the second stage.  But our empty weight estimates were based on historical designs with more metal than composites.  We will begin to seek mass reduction in the structural area to begin with.  Later we can explore the potential of new propulsion technology.

As we said this will not produce an actual design, but it will produce a CAD model that can help predict structural mass.  The models will be edited for mass data that reports total mass and the center of gravity.  From one solid model I do a lot of carving to emulate a complex structural assembly with a single model.  The first basic model is fun, but it never ends as we strive to shave off weight.




It looks a little breezy now, but we can cover it later with lightweight skins and thermal protection.  There are a lot of details to add as mechanisms and payload are considered.  All have to have mass data entered and analyzed.

Looking at our Concorde role model, we see a simplified representation of the delta wing with spaces for fuel tanks and a big opening for landing gear.  There is both a problem and an opportunity in that.  The wing spars pass their loads under the fuselage and bulkheads.  Where there are few spaces for spars not filled with fuel, an opening for landing gear is another gap in available structures.


The reality is a bit more complex in the complete structure.  The thin airfoils offer only a low height for spars, and they meet the fuselage abruptly, preventing the deeper section of a blended body.



Here is a good example of a wing blended into the fuselage.  This allows tall bulkhead sections and smooth transitions that distribute stresses over and under the fuselage.  Again we see a gap at the landing gear.


This must have been a challenge with the thin wing leading edge.  The “Y” at the rear still offers little path for stresses over the center.  But that “bridge” structure over the engines is a nice fix.  May I suspect that it could offer a service access to the engines?


Here the F-35 Joint Strike fighter again displays a nice load distribution over and under the fuselage and engine.  Fighters have a huge “G” force loading in combat so this is a tough solution to deliver.


I believe the center structure is a large titanium part, possibly machined from a solid block.  That is a heroic large investment but it is light and strong.  We may see new technologies that can deliver a similar but cheaper result.  I expect much lower stresses on our little orbiter, so we have a use for that.

What can we do about heavy landing gear?  We may steal some ideas from the past again.  Here is a very light weight landing gear on a space plane from days of old.  Hard to take off on those though!


A space plane that never got off the ground may yet launch some good solutions.  The Rockwell Star-Raker was a bridge too far in its day, but pieces look valuable today.  We can use fuel under pressure as a way to bolster lighter bulkheads and spars.  It was a technical challenge for cryogenic fuels, but we see it available with HTP and jet fuel.


JETTISONABLE LAUNCH GEAR?  The Germans did that in WWII but I hate bombing civilians with aircraft wheels!  We like light landing gear but we have a very different takeoff gear in mind for later.  These are little bits that can add up to big mass savings.  Takeoff gear for a bird this big is a mass we can do without.  Landing skids can fit in those narrow gaps shown below.


So we target mass reduction while delivering conceptual mechanisms for in-line staging.  We don’t show the top and bottom flanges of bulkheads or lightening holes yet.  But fuel tanks now have made openings in the first stage frame.  This leaves two very deep spar sections all the way across the fuselage.  Between the stages is an expendable stage with a sturdy structure.


Eight worm drive servos pin the structures at four points on each stage.  Later a gas piston system will motivate stage separation with vigor.


Four aerodynamic spar fins offer tapered holes as hard point attachment.  If any should jam, pyrotechnic devices can blow the joints in an emergency.  Better to damage a booster and save the payload or crew.






Our forces should be less than a combat aircraft, so a titanium structure should again be adequate for this installation. (can you see a CAD error in this image?)  A Boeing patent shows two smaller vehicles joined by four folding inter-stage spars.  I think we can do this with one good solid structure.


CAD designers can picture things like this, but aircraft designers have to think about making it work.  Here is one I found online which suggests a similar idea where wings do not operate in close harmony.  It also points out the issue with landing gear.  Three sets of landing gear?  How does this aircraft rotate on takeoff to achieve the angle of attack for flight?  Well, Dan Raymer’s Aircraft Design book tells us not to fall in love with our CAD images.  Take breaks often!


Here we may begin to flesh out the vehicle and its upper stage.  Well, I am still trying to earn my weirdness merit badge.  How am I doing so far?  Remember, I am illustrating the questions and there are more solutions that I don’t know about yet.  I am challenging innovators and vendors to inform us of better methods and products.  Aircraft designers and rocket guys bring your ideas!  Aero and Space have not been talking for a while now.  We may assume that additive manufacturing has ideas about those titanium structures.  There are also new technologies for thermal protection and propulsion.  You are all invited to contribute on our Facebook group and publish to “Wings to Space” blog.



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