X-37C: plans for a crewed version of the X-37

[vulture4]

190kts...

Could that be because the wings were constrained to a span of less than 15 feet by the need to fit in the Shuttle cargo bay? Did the X-37C maintain the same wing loading? The other asre that puzzles me is the squared-off tail of the X-37B. The final design had to fit inside a 5m fairing and also be mounted to the Atlas by the tail for launch, maybe the square (and high-drag) tail was needed for the latter.

[Prober]

190kts...

The other asre that puzzles me is the squared-off tail of the X-37B. The final design had to fit inside a 5m fairing and also be mounted to the Atlas by the tail for launch, maybe the square (and high-drag) tail was needed for the latter.

the squared off tail comes back in the x-40 days...
designed for the shuttle, then delta II, then moved to Atlas.
this program(s) go in many directions to keep funded.

[Jim]

the squared off tail comes back in the x-40 days...
designed for the shuttle, then delta II, then moved to Atlas.
this program(s) go in many directions to keep funded.

 the design did not change in going from shuttle to ELV's.  Delta II was only considered for a few months.

[Jim]

Could that be because the wings were constrained to a span of less than 15 feet by the need to fit in the Shuttle cargo bay?

yes.

[Rocket Science]

190kts...

Could that be because the wings were constrained to a span of less than 15 feet by the need to fit in the Shuttle cargo bay? Did the X-37C maintain the same wing loading? The other asre that puzzles me is the squared-off tail of the X-37B. The final design had to fit inside a 5m fairing and also be mounted to the Atlas by the tail for launch, maybe the square (and high-drag) tail was needed for the latter.

The first thing we have to remember is that this is a rocket plane and not an airplane. That being said, the square -off back end you refer to can be seen on all the "X Series: of rocket planes that had engine bells an feed/dump lines at the rear. The obvious other reason is that you have to mate your rocket plane to the adapter on the launch vehicle. Other vehicles like the Shuttle had to deal with base heating from all the engines and motors back there.
It is not a big deal to have a squared off tail and you see it daily on road vehicles every day and on the racetrack for purposedly designed sports racing cars. The Kammback was a result of aerdynamic theory of Von Karman. He found that there are a subset of design conditions (particularly when there is a length constraint involved) where the total drag is less if you simply cut off the tailcone with sharp corners, rather than taper it down to a point in the same overall length, with attendant massive flow detachment. We don't see that used in airplanes much because we rarely have a length constraint of that magnitude.

http://www.centennialofflight.gov/essay/Theories_of_Flight/von_Karman/TH21.htm

[vulture4]

190kts...

The other asre that puzzles me is the squared-off tail of the X-37B. The final design had to fit inside a 5m fairing and also be mounted to the Atlas by the tail for launch, maybe the square (and high-drag) tail was needed for the latter.

the squared off tail comes back in the x-40 days...
designed for the shuttle, then delta II, then moved to Atlas.
this program(s) go in many directions to keep funded.

The fact that it has survived this long and not simply faded away suggests that there is somebody (I assume at Boeing) who has a clear vision of the advantages of the concept and the role it could play. I would think without the fairing a somewhat longer wing and a mating structure on the booster that would allow the tail of the flight vehicle to be a little more streamlined could really improve landing performance in marginal winds.

NASA seems to see little or no difference between the winged X-37 and a  wingless lifting body, which seems ironic considering the close relationship of the X-37 to the Shuttle design and the research during the design phase of the Shuttle program years ago. To me the delta wing and separated V-tail configuration of the X-37 would appear to have better potential for hypersonic crossrange (due to the wing area at high angle of attack) providing more landing opportunities, CG tolerance (due to the long moment arm for pitch trim) and better structural weight and fatigue life (due to the feasibility of a circular pressure hull). Most importantly, the low-speed L/D and should be higher, providing lower touchdown airspeed and improvement in the landing weather requirements (due to the higher aspect ratio of the lifting airfoil). The X-37 even has wing flaps, not feasible on the Shuttle or Dreamchaser. The Shuttle landings had significant constraints on weather, CG etc. and were on occasion near the edge of what could be safely accomplished; wider performance margins on landing would, in my opinion, significantly improve both safety and operational flexibility.

[Rocket Science]

With all due respect, your opinion doesn’t trump aerodynamics and operational requirements. I have already posted to you more once that the X-37 landing speed is >200Kts with reference link. No matter how much you like the X-37 accept the laws of aero-physical laws and move on… I should know, I teach physics and I’m also licensed pilot and auto racer…

Regards
Robert

[vulture4]

With all due respect, your opinion doesn’t trump aerodynamics an operational requirements. I have already posted to you more once that the X-37 landing speed is >200Kts with reference link. No matter how much you like the X-37 accept the laws of aero-physical laws and move on… I should know, I teach physics and I’m also licensed pilot and auto racer…

Regards
Robert

I replied that the X-37 wingspan and aspect ratio was constrained by the need to fit in the 15 foot payload bay of the Shuttle.

I am not a race car driver, but it is my understanding that the goal of a race car is to _avoid_ aerodynamic lift. At least that seemed to be the purpose of the reverse-ground-effect vacuum blowers that Porsche used to run in the Can-Am at Watkins Glen before they were disallowed. The goal of an aircraft (I got my pilot's license 40 year ago and have two engineering degrees and 25 years in the space program) is in most circumstances to improve lift and reduce drag. I would hope you would take the time to actually read the paper on aerodynamic performance of the lifting bodies for which I provided a link.

"It is not a big deal to have a squared off tail"

That of course depends on whether or not drag is a concern. Most of the NASA lifting bodies had extensive boattailing yet managed L/D no more than 3.5. The wing-and-fuselage Shuttle did better than any of them with 4.5 even with the engine bells exposed. The importance of tail drag is clearly demonstrated by the performance of the Shuttle with the tail fairing in place; it has an L/D of 7.5, exactly double that of the HL-10 and blowing the doors off any of the lifting body designs. This kind of performance advantage is extraordinary and cannot, in my opinion, be ignored if we want a launch system that is practical and safe.

[Rocket Science]

With all due respect, your opinion doesn’t trump aerodynamics an operational requirements. I have already posted to you more once that the X-37 landing speed is >200Kts with reference link. No matter how much you like the X-37 accept the laws of aero-physical laws and move on… I should know, I teach physics and I’m also licensed pilot and auto racer…

Regards
Robert

I replied that the X-37 wingspan and aspect ratio was constrained by the need to fit in the 15 foot payload bay of the Shuttle.

I am not a race car driver, but it is my understanding that the goal of a race car is to _avoid_ aerodynamic lift. At least that seemed to be the purpose of the reverse-ground-effect vacuum blowers that Porsche used to run in the Can-Am at Watkins Glen before they were disallowed. The goal of an aircraft (I got my pilot's license 40 year ago and have two engineering degrees and 25 years in the space program) is in most circumstances to improve lift and reduce drag. I would hope you would take the time to actually read the paper on aerodynamic performance of the lifting bodies for which I provided a link.

"It is not a big deal to have a squared off tail"

That of course depends on whether or not drag is a concern. Most of the NASA lifting bodies had extensive boattailing yet managed L/D no more than 3.5. The wing-and-fuselage Shuttle did better than any of them with 4.5 even with the engine bells exposed. The importance of tail drag is clearly demonstrated by the performance of the Shuttle with the tail fairing in place; it has an L/D of 7.5, exactly double that of the HL-10 and blowing the doors off any of the lifting body designs. This kind of performance advantage is extraordinary and cannot, in my opinion, be ignored if we want a launch system that is practical and safe.

A purpose designed racer had to reduce drag while creating downforce. I’ve read those paper yet you still refuse to believe that the x-37 has a high wing loading and still will have cross wind limitations. It is not a glider sailplane with a 50:1 glide ratio…

Edit to add: If you re-read that paper you can see the “tail cone” on the Orbiter was used only for the early ALT’s and not the operational Orbiter retuning to Earth. It was later removed for proper data collection and flight handling. Thus that represents the realistic lower L/D ratio. All the lifting bodies had a “chopped” flat tail area and made use of the laminar flow being maintained at the rear. Unless you have an extremely long vehicle like Concorde, can you maintain laminar flow at the rear with your “boat tail”. For all the “blunt-short” lifting entry bodies like including Dream Chaser and X-37 (winged or not) the Von Karman “Kammback” is effective for an operational compromise. Now if you are going to ferry a vehicle like the Orbiter on the SCA, of course the tail cone will reduce drag and fuel consumption and increased airspeed

[vulture4]

I agree the X-37 has a high wing loading, the result of the need to fit in the orbiter payload bay. The C model would not have this constraint.

Here's an interesting video-
http://www.space.com/9940-secretive-space-plane-meet-37b.html
from this page
http://www.space.com/13230-secretive-37b-space-plane-future-astronauts.html

[Rocket Science]

I agree the X-37 has a high wing loading, the result of the need to fit in the orbiter payload bay. The C model would not have this constraint.

Here's an interesting video-
http://www.space.com/9940-secretive-space-plane-meet-37b.html
from this page
http://www.space.com/13230-secretive-37b-space-plane-future-astronauts.html

It really no longer has to just do with the payload bay of the orbiter. One the DoD took it over they could have done what they wanted with it including increase wingspan and better glide ratio. They chose not to because of operational requirements, launch fairing and entry heat load on them, thus a compromise as all engineering solutions are.
If you recall the early Shuttle designs there was a battle of wills  (Max Faget) over long non-swept wing vs delta wings. The double-delta with chines won out and still was a compromise…
If Boeing thinks the X-37C is better than their CST-100 they would built it. So I challenge you to convince them .
http://www.astronautix.com/lvs/shuenara.htm

[vulture4]

The DOD elected not to change the aerostructure although they backtracked to hypergols on propulsion. Since the original design had not included aero loads on launch they had to fabricate a 5-meter fairing for the Atlas to duplicate the orbiter payload bay. It was quite a sight on the first launch with the big fairing dropping off in four segments just as the rocket cleared the earth's shadow. This was considered easier than changing the aerostructure.

[Rocket Science]

The DOD elected not to change the aerostructure although they backtracked to hypergols on propulsion. Since the original design had not included aero loads on launch they had to fabricate a 5-meter fairing for the Atlas to duplicate the orbiter payload bay. It was quite a sight on the first launch with the big fairing dropping off in four segments just as the rocket cleared the earth's shadow. This was considered easier than changing the aerostructure.

Hypergolics are simple, easy to store and perfect for long duration flights...

[Jim]

The DOD elected not to change the aerostructure although they backtracked to hypergols on propulsion. Since the original design had not included aero loads on launch they had to fabricate a 5-meter fairing for the Atlas to duplicate the orbiter payload bay. It was quite a sight on the first launch with the big fairing dropping off in four segments just as the rocket cleared the earth's shadow. This was considered easier than changing the aerostructure.

It wasn't a specially made fairing, it was a stock 5 meter.  And it was two piece, the second set of pieces were from the CFLR deck.

[Jim]

It really no longer has to just do with the payload bay of the orbiter.
 One the DoD took it over they could have done what they wanted with it including increase wingspan and better glide ratio.

Yes, it did since Titan IV and subsequently EELV fairings were sized to shuttle bay. Not true, design was basically complete and some hardware ordered and built when the DOD took over.

[Rocket Science]

It really no longer has to just do with the payload bay of the orbiter.
 One the DoD took it over they could have done what they wanted with it including increase wingspan and better glide ratio.

Yes, it did since Titan IV and subsequently EELV fairings were sized to shuttle bay. Not true, design was basically complete and some hardware ordered and built when the DOD took over.

Yes Jim, all true. My only point is if it "were" needed they could evolve the design, but she flys fine as is...

[Prober]

The DOD elected not to change the aerostructure although they backtracked to hypergols on propulsion. Since the original design had not included aero loads on launch they had to fabricate a 5-meter fairing for the Atlas to duplicate the orbiter payload bay. It was quite a sight on the first launch with the big fairing dropping off in four segments just as the rocket cleared the earth's shadow. This was considered easier than changing the aerostructure.

the DOD did a mission change.   I have a great deal of research and the project had many conflicts during its development.  The AR2-3 engine was redesigned and tested at Stennis.  Mission was for like 21-27 days with a landing.

This pic during the build you might find interesting.

[Jim]

the DOD did a mission change.   I have a great deal of research and the project had many conflicts during its development.  The AR2-3 engine was redesigned and tested at Stennis.  Mission was for like 21-27 days with a landing.

No, those changes happened while it was under NASA, long before DOD took over.

[Prober]

190kts...

Could that be because the wings were constrained to a span of less than 15 feet by the need to fit in the Shuttle cargo bay? Did the X-37C maintain the same wing loading? The other asre that puzzles me is the squared-off tail of the X-37B. The final design had to fit inside a 5m fairing and also be mounted to the Atlas by the tail for launch, maybe the square (and high-drag) tail was needed for the latter.

and this you will enjoy.....one of the subprojects proposed.

http://www.sei.aero/eng/papers/uploads/archive/AIAA-2004-5950.pdf

[BrightLight]

190kts...

Could that be because the wings were constrained to a span of less than 15 feet by the need to fit in the Shuttle cargo bay? Did the X-37C maintain the same wing loading? The other asre that puzzles me is the squared-off tail of the X-37B. The final design had to fit inside a 5m fairing and also be mounted to the Atlas by the tail for launch, maybe the square (and high-drag) tail was needed for the latter.

and this you will enjoy.....one of the subprojects proposed.

http://www.sei.aero/eng/papers/uploads/archive/AIAA-2004-5950.pdf

How much is that pony in the window?