To reach orbit in horizontal launch is a challenge. We need a first stage that is nearly single stage to orbit capable. Even then we projected a need for the orbiter to make some contribution to the effort. We had to make room for more fuel to achieve orbit. As such we may have a slightly larger vehicle for similar payload capacity. Published data on mass varies widely as some are only targeting limited fuel for orbit and reentry. And some may publish misinformation too? Here is how we stack up, in the middle of the pack…ouch that is a big fuel mass! Well it is being adjusted down real fast now, probably wet mass of 86,000 lbs. Then we start chasing more mass ghosts!
we have a rough outline of structures to transfer loads when attached to the booster and allow room for fuel. More details will be added for payload service later.
FUEL AND STRUCTURES
ROUGH SCALE TO THE X-37 AT 29 AND 54 FT. LENGTH.
This early X-37 study indicates that they once considered HTP and JP as we are doing now. Currently the X-37 uses highly toxic fuels that we will avoid. Besides, we have a source of 100% HTP in Wyoming!
THE X-38 HAD STRAP ON ROCKETS, LITTLE ON BOARD PROPULSION AS A LIFEBOAT.
We anticipate composite structures rather than the metal frames of the X-38.
WE ARE LARGER THAN DREAMCHASER WITH CONFORMAL FUEL TANKS
Here is an illustration of how high pressure fuel tanks get around structures. We will use some low pressure with HTP, but we can fit close to the structures. We do pay a penalty in fuel mass, but hope to reclaim some of that from other components. Our structures show similar spacing here. But we lack a crew pressure vessel to aid structures. We may get some of that from low pressure fuel tanks.
WE WILL USE A TOP HATCH INSTEAD OF A REAR HATCH.
(I wonder how warm that hatch gets in the rocket plume?)
WE ARE SLIGHTLY SMALLER THAN THE (DEAD) ESA HERMES
Our structures are spaced farther apart…were theirs metal?
AND SPEAKING OF DEAD BIRDS…WE ARE SIMILAR TO ORBITAL SCIENCES PROMETHEUS.
We will be learning more about composite construction as we go along. Scaled Composites is displaying good examples of this kind of construction. Compared to metal aircraft they often build large panels with fewer frame structures. Stressed skin can cover a larger part as seen in this tail section. Frame reinforcements are built in to the panel.
SS2 TAIL STRUCTURES
INNER AND OUTER CABINS ARE CONFORMAL WITH FEW STRUCTURAL ELEMENTS. HOWEVER THERE IS A LOT OF STRUCTURE UNDER THE CABIN IN THESE WINGS. OUR WINGS PASS AROUND THE PAYLOAD.
Now we see the zones opened up for fuel tanks and engine access. More changes will follow as we consider skins, and opportunities to use them to reduce structures. Service access and thermal protection will become issues down the road too.
I expect to find this is still heavy; I got my start designing truck frames! My model airplane was designed with the same heavy hand. We found the fiberglass to be so robust that I had to go in and carve a LOT of unnecessary structures out!
This leads to a valuable point: no one could possibly deliver a complete launcher design single handed. We know a series of vendors who can build prototypes. They will be straightening me out as we go along. This is a look at the future that will only come in steps, with collaboration from all over. There is a pit that stumbles a lot of “new space incubators” that only encourage business in their own state. Sorry, that’s a STINKUBATOR.
We publish this to motivate consideration of new solutions, and a lot of vendors have ideas waiting for us. We can expect a consortium of new and old space technologies to be involved to deliver goals. It will not come out of tiny teams or geniuses. How long did it take us to discover the “Hidden Figures” of NASA history? It needs big teams, big dreams, and big bucks.
As a draftsman I used to deliver blueprints to the shop, but now we can deliver vision to the next generation. My illustrations are pointing out both the open and closed doors. These are based on somewhat reachable new and old technologies. We paint a future for the bold to explore. If Gene Roddenberry’s “Star Trek” inspired engineers, than we of industry can do the same. It’s only a paper Airplane, but Low Earth Orbit is important. “Once you get to earth orbit, you’re halfway to anywhere in the solar system.” Robert A. Heinlein We can’t afford to have unaffordable orbital access.
RETURN TO BASE
Life is hard for an orbiter. The vehicle needs thrusters in space so we have those and a couple of extra ones. The main engine needs a bigger nozzle for space but there is little space on the vehicle with the booster pressing in from behind. The reentry needs a clean shape with a curved bottom and a “duck tail” that will motivate a nose high attitude. Then it has to return to level flight to the runway, deal with possible crosswinds, enter ground effect and join the runway. We prefer to land with the belly down when possible as well.
A BELLY FULL!
ON YOUR OWN
OPEN WIDE AND…
HEY! EXTEND THE NOZZLE INTO PREVIOUSLY OCCUPIED SPACE!
AN ABLATIVE EXTENSION COULD BE EXPENDABLE.
OR WE COULD MOVE THE WHOLE ENGINE WITH ACTUATORS.
THEN ONE COULD GIBMAL THE ENGINE BY RETRACTING THE ACTUATORS.
THE UPPER BODY FLAP “DUCK TAIL”
MAY BE SHAPED TO SPLIT HOT FLOW AWAY FROM THE VERTICAL SURFACES
WHILE SPLIT LOWER SURFACES INFLUENCE PITCH AND ROLL
This not a shape that we have seen proposed before, but it fits our horizontal launch designs. It is modeled in Siemens NX software so it is compatible with CFD programs. If you have such tools we can deliver the solid models to you to analyze. We can’t pay to do this but we can let you look it over for your own interests. Anyone who has the tools has potential to do more than we can do now. I have no problem letting real players evaluate and consider the potential. The real refinement comes when the smart guys have a chance to get paid.
WITH THRUSTERS, CROSSWINDS SHOULD BE NO CHALLENGE…FIGHT BACK!
WRONG END OF THE RUNWAY? NOT IF YOU CAN LAND SHORT…
OR DO A QUICK TURN? (Well I can’t find enough runway photos!)
SERIOUSLY, FLYING INTO GROUND EFFECT IS A LOT EASIER TO DO THAN…
SO WITH THRUSTERS WE CAN DO THIS TOO. ON A WIDE STABLE BASE.
SO WHO NEEDS LANDING GEAR?
So we have considered ways to join the craft and cut mass. We try to watch for aerodynamic needs for reentry and the final landing. Now we should have time to locate fuel tanks and payload while refining the structural notions. CAD tools can illustrate notional ideas if we don’t stray too far from known practices. But the picture will always change as engineers find a path to hardware. Analysis and innovation will change everything. These images are already changing every week. I may not recognize this if it ever gets built!
TRIAL BY FIRE? PASS THAT TEST!
The auto club used to say “Bring them back alive”. That would be a good idea for customer payloads and passengers too. Our orbiter aims to reach orbit from a runway without having a payload fairing as big as my house. That has meant avoiding the tall “V” tails that would disrupt our launcher’s idealized wing. Now we need to be able to handle the inferno of reentry without the usual control surfaces. By now you know that I won’t have any problem with UNusual control surfaces! We have to enter the atmosphere with the nose high and the belly serving as a heat shield. There must be control of pitch, roll, and yaw in temperatures reaching 2000 degrees or more.
There is another segment of this landing though. After surviving the fireball of a meteorite, we want to be able to fly as a decent aircraft on the final approach to the runway. We don’t want a lifting body that only flies level when it is forced to do so while suffering from excessive drag. A flying brick is not reassuring to customers. We need good control in level flight and a good way to meet the runway without a lot of extra weight and complexity.
For control during reentry the ESA demonstrated a very uncomplicated solution. This uses only a split body flap, but doesn’t offer a lot of promise for making a runway landing. This is adequate for the meteorite phase of reentry, but what do we do next for a gentle lading?
First, we have moved the vertical surfaces inboard to preserve a clean flow along the joined wings. This helps assure the air breathing and rocket boosted delivery to space.
Separation in space keeps us away from aerodynamic issues at staging, and we can open up the orbiter body flaps to keep them clear of the rocket engine plume. No drag in space!
For roll and pitch control during reentry the lower body flaps are split per the ESA example above. The elevon fairings remain in place during the early reentry phase. The small elevons might not suffer extreme damage, but they are probably not especially effective during the fireball phase.
When temperature, speed, and altitude drops the fairings may also be dropped. In level flight the elevons and rudders offer more effective control for the final approach.
FAIR THEE WELL!
Now you’re looking at that landing and wondering, “what’s missing from this picture?” Well we want to save some fun for next week, right?
VOTING MYSELF DOWN…A DIFFERENT ANGLE AND A NEW ASPECT
One hazard is passing the bosses scrutiny, and it even happens to the self-unemployed. I don’t like what I’m seeing now. I made the orbiter longer to eliminate the fairing, and it looks a bit thin. This may not be good for a glider! We have some ideas about what works from our earlier models.
The center vehicle is our first model, a balsa and foam glider. When I planned the R/C model on the left I wanted more wing span to carry the added weight of plywood, fiberglass, and electronics. Both had successful first flights and helped confirm the concept and CG locations. Now this new design on the right went for a larger booster to deliver most of the launch energy. It looks like I need to consider more wingspan again.
The R/C model on the left never got the first stage built because we had an airplane that could test launch it. That was a good flight and eased my concerns about the low aspect ratio delta wing. Even being overweight it made the flight. The last flight was not so good. The pilot took the blame, but I know that piggy back configuration was top-heavy. We stage in-line now for good reasons.
THE LATE LAMENTED LAUUNCHER
When I compare the new vehicle to the original Concorde I see that we may be a little short on the length of the strake. So increasing the orbiter’s span may get us back on target for the combined stages on the takeoff run. There is enough wingspan to allow a good flight for the orbiter at lower speeds too.
This shows how the new orbiter more closely matches the previous models. Now we have the same upper stage aspect ratio that we saw working even on un-powered gliders.
While this design is smaller than the Concorde, we should be clean enough to see high supersonic speeds in the atmosphere. Once this reaches higher altitudes the rockets may be able to contribute up to 5,000 mph towards the needed orbital velocity. If we can see 50 miles and 5000 mph it is an improvement over 5 miles and 500 mph. New air breathing engine technology may put this in reach.
Now that I got the outline revised I get to go back and re-do all the other parts that used to fit! This revision has opened the door on a lot of other fixes that will all help. There is a lot more room for fuel onboard now too. It just burns my clock to be a perfectionist!
FIRE BURN AND CAULDRON BUBBLE
Reentry is a fiery ordeal for an orbital vehicle. But before it can experience that adventure we have to get it to space. Not wanting to use a huge fairing for vertical launch we need to be sure we can do a horizontal launch. We identified issues with using a mid-stage fairing previously. Now we want to consider the aerodynamics as well.
Seeing the “V” tail so close to the leading edge of the Concorde style wing is a concern. While this may not be the only way to cultivate a friendly vortex, we still want to make it work. If the tails throw off their own vortexes they may interfere with this. For this reason I chose to move the tails inboard and upright. There are many issues, but the first one is getting off the runway in the most efficient manner. So this is the look of the next stage of our adventure.
This long thin shape moves the tails inboard and vertical to avoid interference with the wings. We have the tails serving as both aerodynamic and structural elements where hard point attachment is provided.
Again, there may be better wings to tame the vortex. I suspect this wing has that “zig-zag” as a vortex producing feature. And this engine inlet is not avoiding boundary layer air! Smart guys may give you solutions like this as soon as you pay them!
We will need to modify the placement of control surfaces to manage pitch, roll, and yaw. To allow full flying tail ailerons I remove two small fairings after staging. Better than a 14,000 lb expendable fairing I should hope?
Cutting the fairings off as a flat leaves an edge to break off some boundary flow. This may keep some thermal issues from invading the seam between the flat and the full flying tails.
We now have 20 degrees of roll control and an upper body flap to replace the old “duck tail”. Most of our turns can be by roll and pitching up during reentry. Rudders are less effective at high angle of attack, and the thin vertical surfaces are sheltered from most thermal issues.
On the lower surface is a lower body flap to bring the nose down at lower altitudes and speeds. Two stub fins provide hard point attachment and also serve as landing skids as well. In level flight the conventional rudders will be an asset in cross wind landings.
The lower side of the craft is fairly smooth and protected with fat rounded features. As an artificial meteorite these should be good for a glorious blazing reentry. All’s well that falls well, right? Hopefully aerodynamic analysis will reveal enough wide and flat for the slow part of our landing as well.
This aft view reveals four extended vertical fin surfaces that double as the hard point structure for stage attachment. This recessed engine will make thermal issues for the rear surfaces. It may also offer a unique opportunity to provide a trick nozzle solution. We can position a telescoping section of nozzle extension in this opening that will provide both a cooled shield and a vacuum nozzle shape. More fun to come for the engineers!
This brings us to the rough structural notions with the attachment lining our structures up between the two stages. There will be a lot more fuel volume available in the orbiter now.
This long slim shape offers a cylindrical payload area since most are still designed to fit vertical launch rockets. This still allows a lot of internal volume for fuel and systems.
Now we have more details to define as systems are added to the rough structural cut. There will be more fun ahead, and more mistakes for the smart guys to fix, so stay tuned. And just think what the draftsman has to look forward to. When the engineers make the outer shape better we get to re-do every part that gets warped by the changes!
This week we are looking at the mid-stage fairing and seeing a mid-life crisis. (OK, I am WAY past mid-life!) We began the work last week looking at titanium to handle the structure joining two stages…bad idea! This week we add cylinders to push the vehicles apart for staging, and add skins to this fairing stage. Staging now separates the mid and second stage, then sheds the cover and the structure. Those are expendable unless we find a way to parachute them back to earth.
Here we see the first and second stage pistons driven from their cylinders and the fairing cover ejected.
Now we really have to reduce the titanium structure mass, and add skins and covers of carbon fiber. I tend to build on the heavy side, expecting analysis to point out where to reduce mass. I can deliver illustrations, but validation comes from the high paid partners. Since we have no other mechanical parts here, this is a good place to start tuning my mass estimations. And I really need a tune up!
With my typical bulkhead and skin thickness being quickly carved, this will be a very heavy piece of airframe. It produces details that are visible in renderings, but overweight in the flesh. Too strong is not always bad though. Our model was plywood and fiberglass. The glass was so strong I had to cut a lot of structures out to reduce weight. It completed a good flight, and then two less good flights. The second crash was a power dive from 300 feet while still attached to the carrier aircraft. The fiberglass never cracked, and it is taped up and on display today…we thank Performance One Aviation of Mesa Arizona for super duty body work!
ON DISPLAY IN OUR SHOWROOM
This study did generate some numbers, and we can be sure it needs some mass reduction work. We know that the big space plane projects are being done mostly of composites now. So these lessons can tune our mass estimates more accurately. This is not a one material target though. We see carbon fiber and titanium in the model. There are also some thermal protection material, wiring harnesses, fasteners and other materials mixed in. that means we can factor the material densities a bit in either direction when the total assembly is considered. It certainly seems to need some work. The initial mass figures indicate a lead barge…36,435 lbs!
Now my thick carbon fiber skins are a bit much, but the shuttle thermal tiles were very light. Their density was only .005-.007 lb./cu. in. so we can factor that in. Other TPS may not offer that low density so we can’t get carried away if we want the most economical solutions. Another area for reduction may be the titanium structure. (gee, it’s only 23,032 lbs!) It can likely be a mix with carbon fiber parts. Titanium is now available with new manufacturing methods too. It is possible to use 3D printing, or additive manufacturing. As much as I chopped this model up to reduce weight, we can better target stress areas and cut down low stress areas. How much would this help here? Take a look at the potential of these parts:
I believe that there are smart people out there who can deliver strong parts with low mass. My next run at cutting mass divided the structure up with a lot less titanium and a lot more thin carbon fiber. Oh, gee, we carved it down to “only” 15,427 lbs!
Even this requires drastic measures, as even small units of titanium are a lot heavier than carbon fiber. the new images show a lot more nice dark carbon and less metal…not so shiny. Possibly not too bright either though.
This is why Dan Raymer warns us not to fall in love with your CAD models and drawings. They are so pretty, but the engineers will always be changing them…usually for good reason. Other problems with this fairing include eight servos and four big gas cylinders. This mid-stage may be just a bridge too far. I am inspired to revert to some older ideas that worked better.
If I refer to our suborbital version, we had no mid-bridge and used part of the tail structure as hard points. We can eliminate four servos and two cylinders along with a lot of messy mass. Now I can look forward to a redesign of the second stage and a lot more weirdness to come. But perhaps not as much as we see in this image!
So now you may be wondering how a one-man design can look so much like a committee creation. Just remember, the boss always has the right to be wrong. This is a real-time design so we can get used to going back to the drawing board at times. Bad ideas are the seeds of tomorrow’s better ideas. Stay tuned for more of those…?
NO BONES ABOUT IT…
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.
EIGHT HARD POINT PIN MECHANISMS
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.