OK, points (no pun intended) noted; the question now becomes something
along the lines of "Are normal cutter ops handled at velocities where the
aerodynamics becomes enough of an issue that we'd 'need' a 'fairing collar'
or a new class of cutter-like vessel designed for the box module?" The
original question specified "cutter-compatible fittings" specifically so
that the same control/drive framework could be used, provided that the
aerodynamics question is ignored.

Also, has anyone designed a "truck" that could use either the standard
cylinder or the proposed box as a "trailer"?


On Mon, 25 Nov 2019 17:30:30 -0800, Ethan McKinney
<xxxxxx@gmail.com> wrote:

>The square module would affect the cutter's aerodynamics and might change
>the structural requirements for the module.
>
>At subsonic speeds, the cutter simply has so much power, and effectively
>infinite fuel, that it doesn't care about the additional drag. (The flat
>face of the module hitting the airflow is bad; the extreme turbulent flow
>is worse.) This continues in the transonic and low supersonic regimes,
>although the dynamic pressure on the exposed corners of the module will
>build rapidly. If it was a shipping container, this would start to be a
>problem. Assuming that the cutter has advanced fly-by-wire controls with
>artificial dynamic stability, the buffetting caused by the exposed corners
>should be controllable.
>
>As the cutter's Mach number increases, dynamic pressure on the corners also
>increases. Still, the cutter has so much power that it can simply push
>through this. At some point, you're going to be concerned about the
>longitudinal crush resistance of the module (pushing on the front to crush
>it toward the back). The cutter as a whole is very strong, but I would
>design normal modules with the assumption that the front and rear faces
>wouldn't be exposed to high dynamic pressure. At worst, this means some
>additional mass and volume devoted to structure, but it should be taken
>into account.
>
>I'd want to have fairings added to the cutter to cover all eight corners of
>the module (front and rear). This would be a huge help with buffetting, if
>nothing else. Of course, the fairings have to be strong enough to take the
>pressure on them, not tear off in a high negative-G maneuver (from the
>perspective of the fairing), etc. Yes, at TL-12 this is all pretty trivial,
>I'm sure. There are real-world missiles that go to a square cross-section
>in the mid-body, although their cross-sections have rounded corners.
>
>If you don't add the fairings, things get really fun when you enter the
>hypersonic regime. The blunt nose of a cutter is actually a decent shape
>for ballistic reentry (or faster). (See
>https://www.airspacemag.com/space/how-the-spaceship-got-its-shape-137293282/
>) The cutter nose is not so good for subsonic, transonic, or even
>supersonic drag, but, again, it has enough power that it gets to not care a
>lot of the time. When exposed corners are hypersonic, they become hot spots
>where the atmosphere gets compressed and super-heated. Make sure that you
>have good thermal properties, insulation, cooling, materials that aren't
>weakened by extreme heat, etc., etc. because the front of the module is
>well ahead of the cutter's center of mass, any deviation from a zero angle
>of attack (pointing straight into the airflow) will cause a powerful
>dynamic instability reinforcing the movement. In other words, if you yaw a
>bit to the right, the left corners will "catch" the hypersonic flow
>directly. Be sure that you have extremely strong controls, preferably
>thruster plates capable of 15G lateral thrust, or extendable control
>surfaces at the tail.
>
>On Mon, Nov 25, 2019, 15:36 Jeff Zeitlin <xxxxxx@freelancetraveller.com>
>wrote:
>
>> The standard cutter module is a cylinder, given as 15m long and 6m
>> diameter, for a displacement of 30dT. However, because of the shape, less
>> than the full 30dT is usable.
>>
>> What are the ramifications of building a module with cutter-compatible
>> fittings, but square in cross-section, 6m wide, 6m high, and 15m long, for
>> a total (and usable) volume of 40dT?
>>
>>
>> ®Traveller is a registered trademark of
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>> Freelance Traveller
>>     The Electronic Fan-Supported Traveller® Resource
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®Traveller is a registered trademark of
Far Future Enterprises, 1977-2018. Use of
the trademark in this notice and in the
referenced materials is not intended to
infringe or devalue the trademark.

--
Jeff Zeitlin, Editor
Freelance Traveller
    The Electronic Fan-Supported Traveller® Resource
xxxxxx@freelancetraveller.com
http://www.freelancetraveller.com

Freelance Traveller extends its thanks to the following
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