Re: The RCS: Voice Transcript

From: Peter Stickney (peter_at_adelphia.net)
Date: 08/17/04 

Date: Mon, 16 Aug 2004 22:51:50 -0400

In article <10guppepi4g0b09@corp.supernews.com>,
        Pat Flannery <flanner@daktel.com> writes:
>
>
> Mary Shafer wrote:
>
>>On Sun, 01 Aug 2004 16:12:15 -0500, Pat Flannery <flanner@daktel.com>
>>wrote:
>>
>>
>>
>>>It always amazed me that something that streamlined could be that slow;
>>>of course it wasn't area-ruled and that didn't help it any,
>>>but it looked like it was doing around Mach 4 standing still.
>>>It lifted off at 260 MPH, and once actually managed to Mach 1.21 in a
>>>power dive. So its maximum speed was around three times its takeoff
>>>speed...not terribly impressive.
>>>
>>>
>>
>>The X-3 had the same problem as the One-Oh-Wonder and a couple of
>>other aircraft and it wasn't lack of area ruling.
>>
>
> Take a look at it head on though:
> http://www.globalsecurity.org/military/systems/aircraft/images/X-3_3view.gif
> Not only does the fuselage have a lot of wetted area, but it's basically
> square in section back where the wings are attached; which also is about
> its thickest point, the non-area ruled fuselage was enough to prevent
> the YF-102 from getting through the sound barrier due to transonic drag-
> in the case of the X-3, the transonic airflow over the wing gets to run
> into the fuselage side at a ninety degree angle; far worse than if it
> were to encounter a more cylindrical shape like on the YF-102.
> I don't think you would have much luck getting this thing to go to
> higher Mach numbers even with more thrust; and the inlets also were
> badly designed from an aerodynamic and airflow to the engines point of view.

Yabbut, what's important for the Area Rule is teh change in
cross-sectional area. With such a small, thin wing, it really doesn't
add much, and the fuselage is actually pretty close to a Sears-Haack
Body. (Think Rifle Bullet) I wonder about the base drag, though.
Reviewing teh NACA reports on teh X-3 that are on the NACA and Dryden
Tech Reports Servers shows that predicted adn measured drag were
actually very close.
 
>>It was lack of thrust, coupled with lack of space for a bigger engine.
>>Just as a rule for aerospace success, design and build either an
>>airframe or a power plant, but not both at once. The second rule is
>>that you can't ever have too much thrust, but you can easily have too
>>much drag and too much weight. These two rules work for everything
>>from little RC models to the Space Shuttle.
>>
>>If you have a proven powerplant, you design the airframe to fit around
>>it. That's vastly easier than designing a new engine to fit into an
>>airframe built to hold an old engine[1].
>>
>>Not following this rule is how the USAF got McAir to do the Voodoo
>>that they did, instead of doing the Voodoo that they meant to do. So
>>if you want to know how to do the voodoo that you should do, you do.

Of course, if logic had reigned, they'd have let Kelly Johnson stick
J47s into the F-90 (XF-88 competitor.) If you look at a photo of the
F-90's rear end, the tailpipes of its itty-bitty J34's only take up
half of the engine bay. Tge F-90 was a real loe-drag airplane, too -
Given its size, and the lack of power, it moved pretty good. (But
couldn't climb for beans) With a developed F-90 with real engines,
The AIr Force would have bought them instead of the F-101, or, for
that matter, the F-105 or teh Air Force F-4. Of course, there would
have been no F-104, either. 

-- 
Pete Stickney
 A strong conviction that something must be done is the parent of many
 bad measures.  -- Daniel Webster

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