Hypersonic Transport

[Mossie]

I don't think so, I think it's the seat back only.

[KJ_Lesnick]

I'm making some guesstimates here, but I'm figuring since the MD-2001, the McDonnell Douglas Orient-Express was 14-abreast internally which essentially consists of 2 x 5 abreast cabins, and 1 x 4-abreast cabin.  So based on that I've made some guesstimates based on the following.  The DC-9/MD-80 and Convair-880/Convair 990 which both have five abreast fuselages have cabin widths of 132 to 134.5 inches, the Concorde which has a fuselage of 4 abreast has a fuselage width of 8'8" or 104-inches.  

So 132 x 2 + 104 = 368 inches, and 134.5 x 2 + 104 = 373".  Granted each cabin has a divider on the inside so there could be a couple extra inches between.  Assuming each seat is 18.5 inches, the divider is about 1/3 to 1/4 that of the seat-width so that would add between 4.625" to 6.167" with a median of 5.286"

Which yields an a cabin width anywhere between 372.625" to 379.167"


KJ Lesnick

[KJ_Lesnick]

Do my numbers sound right?

[kitnut617]

Maybe this will help, scroll down a bit and you'll find a table which has fuselage inside diameters of various airliners. It also gives seat widths in various configurations:

http://en.wikipedia.org/wiki/Wide-body_aircraft

[KJ_Lesnick]

Okay so a DC-9 is 124 inches on the interior, Concorde's interior is 104 inches, with that said the plane essentially has three cabins side-by-side of which 2 are 5 abreast with the center at 4 abreast.

This roughly computes out to 364" with two 6" dividers between the cabin.  Since I think the MD-2001 was to use fuel as a heat-sink and not employ a heat-shield, and I'm thinking of using a heat-shielded structure are those six-inch dividers needed?  The plane could be made a foot thinner otherwise...


KJ Lesnick

[KJ_Lesnick]

Okay, let's go back to the issue of propulsion

Could one develop a hydrogen expander that would incorporate strut-jet like features?  Rather than having a turbo-compressor over the duct, instead the air would go through the compressor, the fuel would vaporize as a function of external heat and the heat of combustion and would drive the turbines.  Rather than having a traditional shaped combustion chamber, you'd have a combustion chamber with geometry more like the strut-jet (not square shaped, it would be annular but with a convergent divergent geometry) that would produce high power rocket-like performance which would be similar to the strut-jet.

You would not need to shut the turbo-compressor off because even as fast as you're going the turbine would not be subject to similar temperature restrictions as it would not be driven by hot gas blasting through the turbines, instead the heat would be absorbed by the LH2 and would then expand and drive the turbine which is very small and located inside the engine (like the P&W 304 engine that powered Suntan), driving the fans/compressor via a reduction gearbox.  I should also note that if it could produce similar performance to the RBCC they had very high power to weight ratios and reasonable subsonic performance (similar to a 1960's era military turbofan)

I don't know if anybody would have thought of it back then truthfully, but considering you had guys coming up with unorthodox engines like those used on HOTOL, and the later SABRE engine design.  Granted those guys were from the UK and this Hypersonic Transport would likely be an American design (Since I'm basing it on American technology that existed already, and the fact that there was an Orient Express proposal devised in the United States in the mid-1980s.)


KJ Lesnick

[KJ_Lesnick]

Here are some diagrams depicting my ideas


This picture depicts the basic concept behind the hydrogen expander engine




This picture depicts the operation of the P&W 304 hydrogen expander engine in particular




This picture depicts a strut-jet RBCC type design





The method of deriving power from hydrogen expansion would be pretty much as depicted in the first and second image with the combustion chamber more like that in the third image, employing a more rocket-like combustion-chamber/nozzle which would ideally be wrapped around the engine (like an annulus, but retaining the convergent divergent bell-nozzle geometry) and would receive airflow from the fan/compressor.

Sound like a good idea?  


Kendra Lesnick
NOTE:  None of the data I am displaying is to the best of my knowledge classified or is in anyway harmful to national-security to the best of my knowledge

[KJ_Lesnick]

Just out of curiousity, why does the P&W 304 have a combustion chamber and an afterburner?  The exhaust doesn't go directly through a turbine, so I fail to understand why there is any need for an afterburner...


KJ Lesnick

[KJ_Lesnick]

The LAPCAT is a proposed hypersonic airliner design with the ability to fly at Mach 5 @ altitudes of at least 80,000 feet for antipodal distances, and also able to fly subsonically for considerable distances as well.  

I was thinking on coming up with some hypothetical ideas working around the basic LAPCAT design.  Here's the ideas I'd be thinking of:

- Removing the canard, and instead changing it with a long, highly swept leading-edge root extention forming out of the aircraft's delta wing forming an effective double-delta.
- Flattening and widening the fuselage to allow more aerodynamic performance to be extracted from the fuselage (Composite structures don't have the metal fatigue problems that metals do, and even during the development of the BWB they were able to work out to some degree using a non circular fuselage)
- Forming the nose and tail into a flattened blade shape which works better at hypersonic speed generally over a conical nose and helps enable the fuselage to better behave as an airfoil

Anybody interested?


Kendra Lesnick

[Weaver]

Okay:

1. Why do you want to remove the canard? How do you propose to control pitch?

2. The fuselage is mostly full of liquid hydrogen tanks which I resume are pressure vessels. As such, they will be more structurally efficient if they are cylinders with hemispherical end caps no matter what material they're made of. Flattening the fuselage would reduce the diameter available for these tanks and to use the new ovoid cross section, you'd either have to have a heavy collection of side-by-side tubes or a heavy non-tubular tank with extra strength at the stress points.

[KJ_Lesnick]

Weaver,

1. Why do you want to remove the canard? How do you propose to control pitch?

I assume the aircraft had elevons for primary pitch control.  Having only a canard for pitch and trim would yield an unstable airplane which for a commercial airliner is something generally to be avoided if you can.  Elevons also generally even on airplanes with canards usually have some trimming functions.  A leading-edge root extension can provide trimming benefits at high speed, especially if sufficiently swept by producing disproportionate amounts of lift up front relative to the rest of the wing which to some degree counteracts the rearward shift in the center of pressure.

2. The fuselage is mostly full of liquid hydrogen tanks which I resume are pressure vessels. As such, they will be more structurally efficient if they are cylinders with hemispherical end caps no matter what material they're made of.

I suppose there is truth to that, but many of the Orient Express concepts often involved flattened tank shapes and I don't recall any problems mentioned regarding the fuel tank set-up.

Flattening the fuselage would reduce the diameter available for these tanks and to use the new ovoid cross section

The idea was to flatten it, but widen it at the same time so the volume would stay about the same.  The flattened structure would provide more lift especially at hypersonic speed.

you'd either have to have a heavy collection of side-by-side tubes or a heavy non-tubular tank with extra strength at the stress points

Of the two which would increase weight the least? 

[KJ_Lesnick]

Do you think LCH₄ would be a preferable fuel-source for a Mach-5 to Mach-6 airliner instead of LH₂?  It's density is lower, it requires less insulation and refrigeration; I don't know if the potential for NOx formation would be substantially greater for LCH₄...

[KJ_Lesnick]

Honestly I think some kind of hybrid of the A2 and a waverider would be a cool idea...

Flattening the fuselage turning the nose and tail into a blade shape (from the overhead view), moving the engines under the fuselage, reshaping the tips a little bit, forming the inboard leading edge into a LERX as it could provide some extra lifting area up front supersonic, some area ruling and blending and such.  

I do have drawing if you need a visual description:



I like the wing design as it offers hypersonic performance and subsonic cruise capability, the engines mounted under the wider fuselage could exploit the wave-riding for inlet benefits too, and obviously improved lift when supersonic/hypersonic.

The afterbody shape is the way it is simply because I haven't thought of anything yet.  Truthfully it would probably be smarter to push the wings back a little bit (One odd idea I've thought of would be to widen the tail up a little bit like the X-43 because it could produce a tailplane effect and with a high enough sweep could keep much of the shockwave off the leading edge and provide a reasonable degree of pitch control to augment elevons which would be mounted on the wing's leading edge but I don't know if it'd work)

As the design is drawn it's length is the same as the LAPCAT A-2.  I don't necessarily think the excessive length is practical, but for the time being, I'll stick with it.

What do you all think?

[KJ_Lesnick]

From what I'm reading the LAPCAT A2 can achieve a L/D ratio of 11:1 at Mach 0.9, and 5.9:1 at Mach 5.  Is this considered good, excellent, superb?  Are there any other aerodynamic shapes that can yield a good hypersonic plane and still achieve at least that performance at subsonic flight without using swing-wings?

KJ Lesnick

[KJ_Lesnick]

How much thrust was the Scimitar projected to produce?  I don't recall ever reading any definitive figures even on their website.

KJ Lesnick