Hypersonic Transport

[KJ_Lesnick]

I know this isn't really a military design, though it could make an interesting Air Force One!

I was thinking about the LAPCAT A2 awhile back and I started thinking, we've had some of the core technology to do what this aircraft could do like 50 years ago, others 15-20 years ago.  Admittedly some of this technology was classified, it was nonetheless do-able.

The obstacles generally revolve around the following

I: Propulsion
II: Thermal Management
III: Aerodynamics
IV: Environmental Concerns

(This section can be a bit long-winded so feel free to skip below this section if you wish)


I: The problem revolved around producing an engine that could produce thrust at low-speed for takeoff and landing, yet also be able to run effectively at high-speed without running into temperature limitations.  The fact is that since the 1950's or 1960's we've had the capability to do this.

The A-12, which first flew in 1962, was officially capable of Mach 3.2, however people who worked on the SR-71A said the plane was good for higher speeds (Mach 6-7); Robert Widmer, who worked on the Convair Kingfish said it (Kingfish) could do Mach 6.25 or 6.5, and both planes were said to be comparable in speed.  Both aircraft were to use a very heavily modified turbojet engine (the J58) which was, on it's own, capable of Mach 4 (The J91 and J93 were designed to power the XB-70, who's chief engineer Walter Spivak specifically stated it's inlets were designed for the temperatures and conditions seen at Mach 4; the J58 was a scaled down version of the J91 with a slightly higher pressure ratio designed for the US Navy, and ended up also being pitched as an alternate to the J93) via the use of a variable camber IGV to lower the pressure ratio throughout the engine and high temperature metallurgy.  By the time this engine was developed as fitted to the A-12, it had underwent so many modifications it truthfully shouldn't have even been designated as the same engine (that would have not been good for secrecy though).  Admittedly the number of compressor stages and turbine stages remained the same, so did the can-annular combustion chamber, and variable-geometry IGV.  Regardless...

• The geometry and size of the blades changed
  
• The metallurgy of seemingly everything in the engine was altered
  
• The afterburner was designed to have full vernier control and the nozzle was made a part of the airframe and enlarged to provide superior expansion
  
• The amount of air-cooling was dramatically increased to the turbine
  
• Six bleed-bypass tubes were added to dump air from the compressors so as to reduce turbine inlet temperatures; by feeding air into the afterburner, afterburner efficiency and thrust were improved at high mach numbers
  
• The JP-7 fuel was used to provide lubrication for the engine as well as active cooling for the afterburner (And possibly the engine: there was something called a bypass-mounted air-cooled air-cooler which in addition to being a tongue-twister, appears to be some kind of kind of intercooler -- bleed air is used for the bypass-system, but is also used for the turbines)
  
• The combustion chamber and afterburner both included a device to allow the fuel/air ratio to be fine-tuned at high mach to keep the engine temperatures down
  
• This one I'm not sure about but I do remember something about the turbine casing being designed to expand allowing the turbines to creep (which is normally a no-no)
  

..
The modified J58-variant was first ready in late 1962 or early 1963, and was first fitted to an A-12 in 1963.

Other engine designs that are usable at hypersonic speeds would include

The hydrogen/methane expander: They basically work by using the expansion of cryogenically cooled gas when exposed to the temperature of the compressor inlet, combustion chamber, and even parts of the airframe to drive a turbine which is generally located inside the engine which drives a multi-stage fan through a reduction gear.  The system works well because there fuel actually can produce power without even burning; the exhaust gas temperature and speeds can be higher because they don't have to flow through a turbine; the turbine being subjected to cooler gasses than typical can run with a higher pressure at a given mach number.  These engines were being developed by Pratt & Whitney during the 1950's, and were to be used on the Lockheed Suntan project.  While this engine wasn't to be hypersonic AFAIK, such an engine could be used for hypersonic aircraft

The Supercharged Ejector Ramjet (SERJ) effectively revolved around the idea of using a ramjet with small rockets which "pumped" the ramjet as well as a small gas-generator (a little turbojet), which drove a small fan/compressor at the front of the engine.  It had the means to work at hypersonic speeds because the gas-generator could be shut-off and the fan could be rotated out of the ramjet.  It was a lightweight and compact engine design which was available by June 1969 at the very least.

II: As an airplane plows through the air, it heats up.  This problem is prevalent even at subsonic speeds, but it's fairly small; when you go supersonic and then hypersonic it becomes far more pronounced.  The issue comes down to being able to keep the plane from burning up, and in this case keep the passengers and the aircrew alive so they can actually live to see their destination, and perhaps post a couple of videos on YouTube (hey these days lots of people do that).

The two ideas revolved around a hot-design which used the fuel as a heat-sink, and would then be expended as fuel, and the other being a heat-shielded design.  Heat shields are clearly the better idea in theory as they reflect away the heat so the plane remains cool, and there's no cooling systems that can fail and get a couple hundred people cremated.  Unfortunately heat-shields can be quite heavy and for a streamlined shape, piped coolant is still needed in the nose.

I would not be surprised if even by the late 1950's if efforts were already underway as the US Government had begun a program called the Aerospace Plane program which is not to be confused with the National Aerospace Plane program started like 29 years later.  By the 1962, North American stated working on a Lenticular Re-Entry Vehicle which was actually a space-borne ballistic missile platform, and based on some of the research they had done with Convair for a missile to defend the XB-70 bomber.  It had a light-weight heat-shield (the whole aircraft weighed 17,000 pounds) which I'm unclear if it started out of the ANP program (there were supersonic proposals and having no fuel to use as a heat-sink, they'd probably use a heat-shield -- hey, remember, no matter how I die it was murder -- even if there was a suicide note and a video of me dying peacefully in my sleep  ) or out of various spaceplane ideas.

By 1965, McDonnell had a rocket-powered spacecraft with a metallic thermal-protection system that could work up to Mach 25 and keep room temperature inside it.  The purpose of the spacecraft was to visit the Manned Orbiting Laboratory.

III: In the late 1950's runways were enlarged to make room for the new jet-liners like the 707's and DC-8's which needed some serious distance to get airborne; once that was done, nobody felt like enlarging things anymore.  Hell even SAC didn't feel like making it's runways longer or modifying it's hangers and facilities for it's proposed B-52 replacement -- and that's the military for god's sake!  The aircraft has to be able to takeoff and land, and handle half decent while doing it, yet fly highly efficient at hypersonic speeds where L/D ratios are generally in the single-digits.

In the late 1940's and early 1950's the British started looking into an idea long this concept effectively using a highly swept delta which was appropriately shaped so that when the shockwave would sweep past the leading edge of the wing, the pressure would build disproportionately along the underside relative to the top.  Over the years they'd come up with numerous variations along this concept. 

In the 1950's in the US, two NACA aerodynamicists: Eggers and Syvertson came up with an idea around achieving high L/D ratios when hypersonic which was based around a delta with a conical body on the underside and downturned wingtips.  The idea was that you'd get a pressure build-up along the bottom without a corresponding pressure up top.  Some waveriding designs had taken shape during the Aerospace Plane program (1957-1963), though this was cancelled.  Some of this research did form the basis of the XB-70.

In 1962, North American had started looking into lenticular-shaped spacecraft based on research done on a defensive missile concocted by Convair.  The vehicle ultimately took on a shape that was had a lenticular leading-edge with delta-wingtips, two vertical fins inboard of the tips, and a straight trailing edge.

In 1966, the British (Pike & Kuchemann) conceived of a design called the Kuchemann Tau which was based around other wave-riding designs but with a difference.  Rather than having a traditional 75-degree delta blended-wing-body with two tail-fins located down the span, this design had a splice in the middle and a 2D section added which was half the span of the wings; the fuselage was then re-contoured to make everything work right and you ended up with a spatular nosed design.

Despite the common myth people seem to have about hypersonic planes needing blunt leading-edges, even by the 1960's they were already keeping the nose-radius down pretty small using high temperature metallurgy and piped coolant running through the leading-edges.  Wright Patterson had done extensive research on this.

IV: Environmental Concerns

The environmental concern is actually present on most all aircraft really, you burn fuel under certain ratios you get high flame temps and N2 and O2 join up into NOx compounds which combined with water vapor cause deterioration of the Ozone layer.  This isn't a big deal for most aircraft, but once you go above around 43,000 feet this begins to become problematic as you get closer and closer to the ozone layer.  Supersonic and hypersonic engines also run hotter, and are typically more powerful so it aggravates things.  It truthfully isn't as big a deal as some would make it out to be, but you know there a lot of tree-hugging hippies who can make a royal stink about things.

On the bright side LH2 burns fast and leaves little NOx behind, LCH4 also burns quick, but I'm not sure how it compares.

If you have decided to read this -- congratulations; if you haven't -- here's the final question: How do you think this would make a WHIF design?

[Rheged]

It would, of course, make a superb Whiff!  The  backstory potential of an Anglo-American project is enormous.

"  In the early 1960's  the  staff of the U S "Brooklyn project"  began co-operating with the  U K's "Metro Metallics"  to develop a  useable   hypersonic aircraft............................"

(Think Manhattan and Tube Alloys of an earlier age  to comprehend the project titles)

[KJ_Lesnick]

Rheged

It would, of course, make a superb Whiff!  The  backstory potential of an Anglo-American project is enormous.

Judging by how the SST project was an all American venture, I assume a hypersonic transport would be the same in the US.  

As for the Europeans, they seemed more amenable to cooperation (UK & France for example worked on the Concorde; UK, France, and Germany worked on Airbus).  I should start doing more research on European Aircraft projects -- the only one's I'm really knowledgeable about are

1: Concorde: Who wouldn't?  It's the only civilian aircraft to actually be designed to fly supersonic for protracted periods of time.  It's also one of the most beautiful airplanes -- damn shame its a museum piece already.  At least I got to fly on it before
2: Airbus A-320/-330/-340 (though I honestly forgot most of what I read):  Mostly I was interested in it because debates would pop up over and over on another forum I belonged to and you'd really get some heated debates and I wanted to have some ammo to slug-down the opponents with.

Others which I am familiar with are

1: TSR-2
2: English Electric Lightning

I do not know much details about hypersonics in the UK and Europe, but in the US in 1967 there was already research done by NASA into Hypersonic Transports, by 1975 there was the Supersonic Cruise Research program, and if research was done into Hypersonic cruise at that time and give 25 years you have a design by 2000

The knowledge you have regarding the UK and Europe I'd love to hear

[deathjester]

25 years to a finished design??   It took a Eurobiz 25 years to get a plane they'd already designed into production!  I present the Eurofighter, where a workable EAP fighter prototype took to the air in 1988, and then went back to the drawing board as it was judged 'too expensive' by the Germans!!

You want a hypersonic transport by 2000?  Better cryogenically freeze yourself - I'll see you in 150 years time...  :lo
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Seriousley, you might find an actual spaceplane, largely designed and built by Reaction Engines Ltd flying about within around 15 - 20 years.  Outmodes a plain old hypersonic bird almost straight away...!

[Rheged]

Rheged

It would, of course, make a superb Whiff!  The  backstory potential of an Anglo-American project is enormous.

Judging by how the SST project was an all American venture, I assume a hypersonic transport would be the same in the US.  

I do not know much details about hypersonics in the UK and Europe, but in the US in 1967 there was already research done by NASA into Hypersonic Transports, by 1975 there was the Supersonic Cruise Research program, and if research was done into Hypersonic cruise at that time and give 25 years you have a design by 2000

The knowledge you have regarding the UK and Europe I'd love to hear

Skylon/ Hotol???

The rest of the group   are probably much more clued up about this sort of thing. I never cease to be amazed and delighted by the breadth and depth of knowledge made freely available  by forum members.


 You might find a surprising amount of data in the book  below.    I didn't buy it, I borrowed it from my local municipal library  at no  cost  at all. Huzzah for the  Local Authorities (Miscellaneous Provisions) Act   that allowed local councils to spend ratepayers money to these up in the late 19th century!!

British Secret Projects 4: Hypersonics, Ramjets and Missiles (Chris Gibson)
Hardcover: 208 pages
Publisher: Midland Publishing, Ltd (January 1, 2008)
ISBN-13: 978-1857802580

[Mr.Creak]

I second the endorsement of BSP4 (although it's written by Tony Buttler!).
EE had some great super/ hypersonic stuff.

[Rheged]

I second the endorsement of BSP4 (although it's written by Tony Buttler!).
EE had some great super/ hypersonic stuff.

Apologies  re possible misleading author info.  Cover says Chris Gibson and Tony Buttler.

[KJ_Lesnick]

25 years to a finished design??  It took a Eurobiz 25 years to get a plane they'd already designed into production!

Well from 1967 to 2000 would be 33 years...

I want to point out that had the SST program went ahead, there would have been a plane entering service in 1974 if all those tree-hugging hippies didn't get in the way

A: The US first started looking into SST's in 1952 or 1954 IIRC
B: Serious efforts started around 1958-1963
C: The SST program was launched in 1963
D: The prototypes would have probably flown in 1970
E: Pre-production models to have flown by 1972
F: Production models to enter service in 1974

That's 22 years and I'm giving 33 years and in the 1980's there was some serious popularity around the idea of a hypersonic airliner

Admittedly you are correct in that this could accelerate a space-plane program along, and in 1986 there was some serious popularity in a spaceplane.  Still I don't know how costly it would be for people wanting to go into space, but Virgin Galactic will cost you an arm and a leg.  Skylon might be cheaper, but I could imagine a spaceplane would be far more useful for other things such as putting satellites into orbit.  After all if you can takeoff and land with a low-maintenance you could pepper space with satellites.

[deathjester]

It's already fairly well peppered with satellites, and bits of the American space programme - in fact, I reckon the main hurdle faced by spaceplanes will be FOD...

[KJ_Lesnick]

It's already fairly well peppered with satellites, and bits of the American space programme - in fact, I reckon the main hurdle faced by spaceplanes will be FOD...

But that wouldn't affect hypersonic planes would it?

[KJ_Lesnick]

Design wise, I was thinking about the following.

The Kuchemann Tau design which was basically a wedge-shaped waverider with a 2D section in the middle which was half the wingspan, and the lenticular reentry vehicle which was a continuous curve.  I'm thinking while the LRV was classified for obvious reasons, the idea of taking the Kuchemann tau and "rounding it out" -- essentially starting with a sweep of zero, then increasing the sweep downspan as you went: This would probably be called an ogival shape.  I think it would work pretty well aerodynamically.

What do you guys think?