Re: [GZG][FH] Planet types - atmosphere effects on VTOL's

I was figuring the fixed max speed on the fan wasn't a mechanical
limitation of the fan or engine (though they would probably design it
that
way to prevent damage from overspeeding the mechanisms) but rather an
aerodynamic limitation on the fan blades.  If the fan spins too fast,
the
tips will be breaking the speed of sound - you get shockwaves, stalling,
etc etc...  All bad for efficiency (and the survival of the fan...). 
Even
if you have super strong blades that won't shatter, you get all kinds of
weird effects on the airflow through the fan once the blades go
supersonic.
 
>
>Ummm.... fixed max speed on fans.... try this.... probably fixed max 
>engine rotational torque to the fan shafts.... pushing denser air 
>would mean preforce a slower max rotation speed, ergo possibly the 
>same max lift. And even if you had the power to ram the fans around 
>faster, you'd cause greater heating in the fans because they'd be 
>moving much heavier air (more of it). So perhaps you don't get these 
>benefits. 
>

So we build really powerful engines with cryogenic cooling fluid
circulating through the fan shafts and fan blades by centripidal
force...  

or

....lots and lots of hamsters, running on the treadmill really fast, and
their breath cools the system....

(ok, never mind)

:-)

>Just an alternate viewpoint.....
>

Hey, like I said, I'm using the armchair-physics method of figuring this
stuff out...so who knows if I'm right.	It seems plausible to me based
on
what I think I know, but it would be good if there was an aerodynamicist
around to comment.

For sure there would be *some* kind of effect on the performance of
aircraft that use aerodynamic lift in a higher-pressure environment, for
the same reasons there are effects on aerodynamic lift in lower-pressure
environments.

Adrian