From: Michael M. Butler (butlerj-nkmail@comp-lib.org)
Date: Tue Aug 11 1998 - 03:31:28 MDT
You're right that helicopters have a problem above 8km (the "Death Zone").
But...
It turns out that true Rotons don't occupy the same flight regime as
helicopters.
Helicopters have to fly sideways. Thus they have unbalanced lift on the
blades.
They have freely-moving very high aspect ratio rotor blades, which causes
all sorts of instabilities when the air speed across them gets too high
(Mach >> 1). The blades are driven by a central shaft that usually must be
articulated to permit maneuvering.
The permissible RPM on a helicopter rotor is strictly limited by all these
factors.
There are a few "rigid rotor" designs that address these limitations, but...
All these characteristics are different from boost-phase Rotons. If you can
spin up a stiff blade array to incredible (non-helicopter-achievable) RPMs,
you can still get some bite out of very thin air. The stresses on the
structure are enormous, but they're symmetrical--if all goes well. The
Roton work I looked at a few years ago also used a hoop to keep the blade
tips constrained.
Calculations suggest that Rotons could work all the way out to where air
acts in a Newtonian way. That's a lot higher than the operating altitude of
a chopper.
And of course you're only using the rotor for *part* of your lift. That's
another difference from regular helicopters.
Not promoting, just reporting.
And rockets, all by themselves, are still the prizewinners at inefficient.
MMB
At 23:06 8/10/98 -0700, you wrote:
>Michael Lorrey wrote:
>
>> >> mark the reason i am having such difficulty with this concept is that
the
>> >> roton is a re-entry system. you still have to lift the thing into orbit
>> >> somehow to reenter the atmosphere. the reentry system of modern
>> >> government launchers is neither the cost driver nor the weight
driver. spike
>>
>> >The roton rotor blades are also used for launching as well.
>
>michael, i should have been clearer in my explanation, but i was trying
tokeep my
>response very short. when i saw the proposal that the roton was
>to use the blades to help launch, i thought the writer must be joking. my
reasoning
>goes thus: if one tries to use the roton blades in the launch phase, one
could at
>best get to an altitude of, well, what? 10 kilometers? our best
helicopters cannot
>get as high as the highest peak, everest, less than 9 km. no chopper rescues
>possible for climbers there.
>
>the key point is, if one starts at zero velocity at the outer edge
atmosphere,
>surprisingly, one is
>not appreciably closer to being in earth orbit than if one starts out on
the deck.
>this is
>true. lets just say the lowest possible orbit is at 100 km, a verrrry
short lived
>orbit. if
>you somehow raise your spacecraft to 100 km without any forward motion,
which is the
>case
>if you went up with a helicopter, you have expended only about 3% of the
energy
>required to
>achieve orbit. i learned of this while evaluating the feasibility of
carrying a
>rocket to great altitude
>using a huge hydrogen balloon. you fire the rocket from a 20 km altitude.
turns
>out, the extra
>altitude gains very little over starting on the ground.
>
>> > In propulsion, it is always more efficient to move a lot
>> >of mass a little, rather than a little mass a lot
>
>right. however, rotary blade flight is not particularly efficient. one
example
>ishuman powered flight. athletes have pedalled across the english
channel, yet
>human powered hover is yet to be accomplished (last i heard anyway). i hate
>to be in the she'll-never-fly-orville crowd, but michael, i can assure you my
>friend, the roton will not fly. nooooo way. {8-[ spike
>
>
>
>
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