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'[OT]: Amateur manned "rocketship"'
2001\12\02@233556 by Russell McMahon

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May not look real - but it is (or will be someday not too long from now).


http://www.armadilloaerospace.com/dec1_01/assembled.jpg

3 rocket motors are visible - 1 large, 2 small - 2 more are hidden by
"pilot's" leg and other hardware.

Bbob - note the car

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2001\12\03@001617 by Josh Koffman

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Is this guy going for that prize for the first private rocket in space?
Anyone won that yet? Man I feel so out of touch...first with Ginger,
then with this heh.

Josh

Russell McMahon wrote:
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2001\12\03@002750 by Alexandre Domingos F. Souza

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>May not look real - but it is (or will be someday not too long from now).
>www.armadilloaerospace.com/dec1_01/assembled.jpg
>3 rocket motors are visible - 1 large, 2 small - 2 more are hidden by
>"pilot's" leg and other hardware.
>Bbob - note the car

       Haha, The new John Carmack''s toy ;o)


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2001\12\03@063614 by Russell McMahon

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In due course maybe.
But first he intends to take out all the manned "time to altitude" records
in the next few years - but not with the craft you see there. That is just a
concept investigator. They have 2 unmanned versions flying so far.
"From the people who brought you Doom" :-) (seriously!)


> Is this guy going for that prize for the first private rocket in space?
> Anyone won that yet? Man I feel so out of touch...first with Ginger,
> then with this heh.
>
> Josh
>
> Russell McMahon wrote:
> >
> > May not look real - but it is (or will be someday not too long from
now).
> >
> > www.armadilloaerospace.com/dec1_01/assembled.jpg
> >
> > 3 rocket motors are visible - 1 large, 2 small - 2 more are hidden by
> > "pilot's" leg and other hardware.

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2001\12\03@125152 by Harold M Hallikainen

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       And my wife and I just watched the Wallace and Grommitt cartoon about
taking a trip to the moon for a cheese vacation...

Harold


On Mon, 3 Dec 2001 00:17:04 -0500 Josh Koffman <.....listsjoshKILLspamspam.....3MTMP.COM>
writes:
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2001\12\07@104852 by Roman Black

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Russell McMahon wrote:
>
> In due course maybe.
> But first he intends to take out all the manned "time to altitude" records
> in the next few years - but not with the craft you see there. That is just a
> concept investigator. They have 2 unmanned versions flying so far.
> "From the people who brought you Doom" :-) (seriously!)


As much respect as I have for the Carmack brothers
and their amazing programming abilities I doubt John's
(and staffs) mechanical engineering skills looking
at some of their "flying machine" prototypes.

Why put the payload on top and the four rockets on
the base at floor level?? Surely hang the payload
or pilot at the bottom and the rocket structure at
the top, the rockets are quite far out from the axis
so it will fix so many of their stability and landing
ground effect feedback problems. I was designing flying
machines from about 8 years old and never would have
made a silly mistake like that. Always HANG your
CG weight below your lift engines if at all possible
guys.

And why so many engines?? Why not a central lift
engine, in the middle with the payload divided in two
and hanging lower and to the front and rear, giving
neutrally stable lift with minimum attitude
compensation needed?? ONE rocket lift engine, some
ducting system for attitude adjustment etc.

From their web site I sensed a whole "we have no clue
but we'll try this and see what happens" attitude.
I really appreciate anyone trying to develop new
and wonderful tech stuff but they are in dire need
of someone who has built mechanical stuff THAT WORKS
for about 20 years.

Their whole flying platform concept seems to be based
on a totally ridiculous mechanical system trying to
rely on very fast software to compensate for all
its flaws and hopefully make it fly. :o)
-Roman

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2001\12\07@235101 by Russell McMahon
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> Russell McMahon wrote:
> >
> > In due course maybe.
> > But first he intends to take out all the manned "time to altitude"
records
> > in the next few years - but not with the craft you see there. That is
just a
> > concept investigator. They have 2 unmanned versions flying so far.
> > "From the people who brought you Doom" :-) (seriously!)

Roman said -

{Quote hidden}

I have very great respect for Roman's electronics abilities but in the case
of rocketry I have to (gently) suggest that John's understanding of the
subject is somewhat greater.

While intuitively it is obvious to many people that having your motors high
and your c of g low makes for stability, it happens that intuition is wrong.
This subject has been debated in many forums on many many many occasions and
it takes the non-believers quite a long time to come to believe that it is
the case. We could have just such a discussion here if people wanted but it
would be easier to trust me on this one :-).
For good descriptions search for "pendulum fallacy", which is the name given
to the incorrect intuitive belief. Robert Goddard's first rocket was built
with the motor at the top for this reason. He rapidly realised that his
original assumptions were eroneous and all his later rockets were of what is
now thought of as "conventional" layout.

But I know people wont believe me.

Re rocket motor count. There is indeed one large central motor which provide
most of the thrust and there are 4 smaller outboard motors which provide
orientation and directional control. This is the smallest number required
for sensible control - you could get away with 3 at 60 degrees provided you
were prepared to make some life threatening compromises in your available
control capabilities and strategies. See beloe re ducting.

John, as you might surmise if you think through what it takes to make the 3d
real time virtual worlds involved in his video games' virtual worlds , is
well versed in the mathematical requirements of controlling a real 3d body
in this world.  I have followed his descriptions for quite some while now
and don't consider there is an excessive amount of "what say we try this"
going on. In a real world with real rocket motors that you develop yourself
from scratch it is exteremly normal for theory and reality to not always
meet. A look at video footage of NASA's early days is most amusing and
spectacular. Large rockets looping the loop, flying horizontally, collapsing
in laaaarge fireballs and more.

Enough I think - you get the general idea.

> And why so many engines??

As above

> Why not a central lift
> engine, in the middle

provided

> with the payload divided in two
> and hanging lower and to the front and rear, giving
> neutrally stable lift with minimum attitude
> compensation needed??

Sadly this doesn't work - pendulum fallacy

> some ducting system for attitude adjustment etc.

They decided that 4 independent small rocket engines are easier than a
single ducted engine. It's an engineering decision. Any rocket I have ever
met with vernier guidance has used multiple thrusters.

> >From their web site I sensed a whole "we have no clue
> but we'll try this and see what happens" attitude.

They have more clues in this particular amateur area than almost anyone
else.
Not as many, yet, as the professionals.

> Their whole flying platform concept seems to be based
> on a totally ridiculous mechanical system trying to
> rely on very fast software to compensate for all
> its flaws and hopefully make it fly. :o)

The only way to slow the system working would be to increase the moment of
inertia which could be achieved by changing the shape. This impacts other
factors considerably. Their control system is now adequately fast to
maintain very creditable stable flight. (see latest video). Not quite as
good as the stability of a Sedgway scooter but that has the great advantage
of having the ground as a reference point.

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2001\12\08@074417 by Peter L. Peres

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> Always HANG your CG weight below your lift engines if at all possible
> guys.

All the early rocket designs went through this phase and gave up on it.
See a model of an early GIRD (Russian) rocket (1920's ro 30's) for an
example.

Everybody went away from this because structural weight is very expensive
in rocketry. The payload-on-top model gives better payload/structure
weight ratio. Also having important parts of the payload (like people)
hanging down near the exhaust plumes is a very bad idea for several
reasons. Heat and noise (noise that kills - 200dB+ probably) being just
two of them.

The stability of an unguided rocket in gravity is not achieved by putting
the traction center higher than the CG, but below it, afaik ;-).

> And why so many engines?? Why not a central lift engine,

Maybe they do not build engines with enough thrust for that or lack the
facilities to test them.

Peter

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2001\12\08@104024 by Roman Black

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Russell McMahon wrote:

> I have very great respect for Roman's electronics abilities but in the case
> of rocketry I have to (gently) suggest that John's understanding of the
> subject is somewhat greater.

Hee hee! Don't be gentle with me buddy, i'm
not delicate. ;o)

{Quote hidden}

I'm aware of the pendulum argument. Not that I
totally agree either. Show me helicopters
(or the Osprey?) with the props at the bottom?
;o)

But I do confess to ignorance of the large
central lift engine, I thought there were just
4 radially mounted lift engines. That does
change things.

But I do stand by my argument re the ground
effect issue. When you originally posted about
John's work (thanks!) I downloaded some of the
landing videos and saw the landing instability
due to their mounting positions of the vector
engines and closeness to the ground with the
ground effect.

Just changing the chassis shape and lifting
these engines a foot or two would make the
world of difference with the problems they
are having on landing by slowing the loop.
As would directing the vector thrusters outwards
slightly like the Harrier etc.

I REALLY respect their commitment in time and
money to the project, and good luck to them.
But none of their mechanical platforms impress
me in the least, in terms of strength to weight
or overall design concept, etc. It still looks
like they just bolted some engines on a couple of
bits of steel pipe and rely on the software to
make it not-crash. But I would LOVE to see them
succeed, don't get me wrong there. :o)
-Roman

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2001\12\08@183806 by John Ferrell

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The pictured configuration will require very delicate throttle adjustments
to maintain attitude. Better control than I thought of as attainable with
rockets.

The calculations would be easier with three engines rather than four...

John Ferrell
6241 Phillippi Rd
Julian NC 27283
Phone: (336)685-9606
Dixie Competition Products
NSRCA 479 AMA 4190  W8CCW
"My Competition is Not My Enemy"



{Original Message removed}

2001\12\08@191941 by Ashley Roll

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Hi John and everyone,

I too read the ARocket list.. basically as far as I understand it, all the
rockets are mono-propellent systems based on H202 (hydrogen peroxide) with a
catalyst in the motor. The H2O2 devolves into water (H2O) and oxygen (O2) +
heat generating steam and thrust.

They "throttle" the attitude control motors by simply turning them on and
off with a solenoid valve in the H2O2 supply. These are controlled by the
on-board computer to fire when correction is needed. I guess the firing
frequency isn't that high otherwise they would have problems with the
solenoid..

I'm not sure, but I think they can do the same sort of throttling with the
main lift engine. Kind of PWM I suppose to control the thrust.

Good luck too them I say, Its a very cool toy :)
Ash.

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> {Original Message removed}

2001\12\09@183815 by Alexandre Domingos F. Souza

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>Roman said -
>> As much respect as I have for the Carmack brothers
>> and their amazing programming abilities I doubt John's
>> (and staffs) mechanical engineering skills looking
>> at some of their "flying machine" prototypes.

       Ah...they are not relatives ;o) Just for the sake of curiosity! :o)


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2001\12\09@184609 by Alexandre Domingos F. Souza

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       Hi there Roman!

>I REALLY respect their commitment in time and
>money to the project, and good luck to them.
>But none of their mechanical platforms impress
>me in the least, in terms of strength to weight
>or overall design concept, etc. It still looks
>like they just bolted some engines on a couple of
>bits of steel pipe and rely on the software to
>make it not-crash. But I would LOVE to see them
>succeed, don't get me wrong there. :o)

       Hmm, looks like windows programming is doing the worse to Carmack's mind - He tries to fix in software, what the hardware doesn't do as it should. Maybe it's time to go back to DOS ;o)))


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2001\12\09@192341 by Russell McMahon

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     Russell McMahon
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> > While intuitively it is obvious to many people that having your motors
high
> > and your c of g low makes for stability, it happens that intuition is
wrong.
> > This subject has been debated in many forums on many many many occasions
and
> > it takes the non-believers quite a long time to come to believe that it
is
> > the case. ..........
> > For good descriptions search for "pendulum fallacy", which is the name
given
> > to the incorrect intuitive belief.

> I'm aware of the pendulum argument. Not that I
> totally agree either. Show me helicopters
> (or the Osprey?) with the props at the bottom?
> ;o)

That's an intriguing thought - I've never seen a CONVENTIONALhelicopter or
lift rotor device that has rotors at the bottom.
I think it's mainly engineering considerations that cause this.
Note that several testbed craft wth several small rotors have been built
this way.
I suspect that a helicopter could be built with full size rotors at the
bottom and function just as well aerodynamically but the question is, why
would you want to? With rockets there are several good reasons to place the
engine at the bottom. With a helicopter the opposite applies.

You mentioned "ground affect" below. I suspect this applies much more to a
craft which uses air displacement as its main motive force and which has  a
large area over which it distributes its air into (ie under the rotor
"shadow" ). In the case of helicopters they tend to turn into hovercraft
when the ground deflects and traps the downwards air from the rotor. Many
accidents have been caused by this effect.  In the case of a rocket there
will indeed be some potential effect from exhaust products being deflected
by the ground but the pressure build up will be minimal compared to a
helicopter and the rocket is NOT "ingesting" external air to act as its
reaction mass - any ground effect would be that which acted on thge
superstructure plus, perhaps, a minimal rsult from increased local pressure
on the rocket nozzle exhaust conditions.

In the case of the osprey the blade length is constrained by the mounting
height of the engines above ground level when taking off (as the rotor tips
tend to suffer if they strike the ground :-) ). AFAIR early designs used
larger rotors/props but this was reduced to allow a lower vehicle height.
(reference here somewhere maybe?)

In the case of a "normal" helicopter it SHOULD be possible to build one with
bottom mounted rotor but the engineering problems would be severe. The
undercarriage would need to extend past the rotor ends (or hop out of the
way each time the rotor came past !) and the c of g would be high when on
the ground due to the space underneath for cyclic etc.

It is said that, left to themselves, an aeroplne tries to fly and an
helicopter tries to crash. My one experience at the controls of a helicopter
make me believe this! A 'copter is not a stable beast by itself and is
indeed something like a weight balanced on an inverted pendulum - as is a
rocket! The requirement for stability with a rocket is that the thrust act
through the centre of mass and all stabilising systems (whether fins or
active guidance) work to procude this result.

> But I do stand by my argument re the ground
> effect issue. When you originally posted about
> John's work (thanks!) I downloaded some of the
> landing videos and saw the landing instability
> due to their mounting positions of the vector
> engines and closeness to the ground with the
> ground effect.

As above. Possibly some ground effect but smaller than for eg copter.
The first "lander" did in fact have no main thrust engine. The next
generation has. There is nothing inherently wrong with getting all your
thrust from the positioning engines - it is an engineering decision, as the
computer can happily enough sort out the net thruist required from each. As
an analog you can consider many modern spacecraft to have several "small"
engines and guidance is carried out largely by gimballing or thrsut
vectoring these various "small" engines". eg Space Shuttle (even the
venerable Atlas which had two small vernier engines visibly firing as it
lifted used these fro roll control and gimballed the main engines for
stability control). Typical rockets have the advantage of "longness &
thinness" to give them a superiorly slower roll rate - John is stuck for the
early vehicles with a sqaut lander shape which is keen to do amusing things
when you look away for a moment. His later planned craft which are aimed at
taking a man to altitude have a more conventional shape.




regards



           Russell McMahon

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2001\12\09@210756 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi,

> That's an intriguing thought - I've never seen a CONVENTIONAL helicopter
or
> lift rotor device that has rotors at the bottom.

> I think it's mainly engineering considerations that cause this.

   It would make it much harder to get passengers inside !! If that is not
the only issue I am pretty sure it is one of the good ones :-)

Best regards,
Alexandre Guimaraes

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2001\12\09@214304 by Russell McMahon

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> The pictured configuration will require very delicate throttle adjustments
> to maintain attitude. Better control than I thought of as attainable with
> rockets.
>
> The calculations would be easier with three engines rather than four...

Hey - this is John Carmack's baby - realtime 3D calculations a spcialty
:-).!

Original lander had 4 small engines.
Current one has 5 - 1 large lift in centre and 4 at periphery that provide
both lift and stability. Main engine throttling is too slow for very rapid
control so small engines provide both delta lift control and stability.
Throttling control on main engine is major factor is less than perfectly
smooth landings at present.


       RM

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2001\12\09@214320 by Russell McMahon

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> I'm not sure, but I think they can do the same sort of throttling with the
> main lift engine. Kind of PWM I suppose to control the thrust.

Motorised ball valve.
90% Peroxide

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2001\12\10@004345 by Russell McMahon

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>
> > That's an intriguing thought - I've never seen a CONVENTIONAL helicopter
>> or lift rotor device that has rotors at the bottom.
> > I think it's mainly engineering considerations that cause this.

> It would make it much harder to get passengers inside !!
> If that is not the only issue I am pretty sure it is one of
> the good ones :-)


And parachuting from one would require exquisite timing :-)
Rappelling on a line would be rather problematical also.

Note - I have seen photos of model helicopters being flown inverted by
suitably expert pilots.
The cyclic has to be capable of suitable range to allow blade pitch to apply
vertical "lift" in the opposite direction to normal.


       RM

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2001\12\10@025214 by Alexandre Domingos F. Souza

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>Note - I have seen photos of model helicopters being flown inverted by
>suitably expert pilots.
>The cyclic has to be capable of suitable range to allow blade pitch to apply
>vertical "lift" in the opposite direction to normal.

       And this is very common! But they say that's impossible in a real heli, why?!?


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2001\12\10@033013 by David VanHorn

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At 05:50 AM 12/10/01 -0200, Alexandre Domingos F. Souza wrote:
> >Note - I have seen photos of model helicopters being flown inverted by
> >suitably expert pilots.
> >The cyclic has to be capable of suitable range to allow blade pitch to apply
> >vertical "lift" in the opposite direction to normal.
>
>         And this is very common! But they say that's impossible in a real
> heli, why?!?

Insuficient huevos?

:)

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2001\12\10@061354 by Russell McMahon

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>Note - I have seen photos of model helicopters being flown inverted by
>suitably expert pilots.
>The cyclic has to be capable of suitable range to allow blade pitch to
apply
>vertical "lift" in the opposite direction to normal.

       And this is very common! But they say that's impossible in a real
heli, why?!?

Just my guess -

1,    A model can easily be modified to have increased control range needed
to do this.
Doing the same thing in a full sized machine would require major design
changes which would need to go through the horrendously expensive and
complex certification processes for man rated flying. Unless there was a
good economic reason to do this it won't get done.

2.    Scaling up a "model" often leads to designs which are unworkable due
to the square/cube law effects (area increases as square of dimensions,
volume and mass as the cube. This is why ants can carry many times their
weight in food, elephants would break their legs if they were able to jump
even a very little, white men can't jump (whoops sorry, wrong thread), and
matchbox scale model cars can be pushed off 200 foot scale height tabletops
to bounce unharmed on the floor. Mayhaps the scaling up of a model
helicopter able to take requisite stresses in both directions would lead to
a design which was prohibitively expensive or massive when scaled up.

Reason 1 sounds most likely to me.

BTW - you can barrel roll a full scale jetliner - a barrel roll is a 1 g
positive g manoeuvre throughout (done properly) but people frown at doing
this.





           Russell McMahon

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2001\12\10@070021 by Walter Banks

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Russell McMahon wrote:

> >Note - I have seen photos of model helicopters being flown inverted by
> >suitably expert pilots.
> >The cyclic has to be capable of suitable range to allow blade pitch to
> apply
> >vertical "lift" in the opposite direction to normal.
>
>         And this is very common! But they say that's impossible in a real
> heli, why?!?
>
> 1,    A model can easily be modified to have increased control range needed
> to do this.
> Doing the same thing in a full sized machine would require major design
> changes which would need to go through the horrendously expensive and
> complex certification processes for man rated flying. Unless there was a
> good economic reason to do this it won't get done.

A few years back you used to see one or two different helicopters
do loops at air shows although not the same as inverted flying it has
some of the same problems.

The biggest problem on full sized helicopters is tail strike from a flexing
rotor
when inverted the rotor cones towards the tail. Although not that complicated
inverted flight needs a inverted fuel and oil system. Unlike an airplane an
engine
failure on an inverted helicopter would eat up a lot of energy getting upright
before an auto-rotation.

Many years ago I worked at company that built a prototype(s) of a
battlefield stabilized camera platform on an inverted helicopter base.
(Counter rotating blades on the bottom) It was electric powered by a cable
running down to the ground. (600 volts 400 hertz) We used to sign out
test flight films at lunch hour for our amusement. It did a great figure 9 .

A helicopter is unstable in a hover and tends to have positive feedback.
Flying forward it is more like an airplane with an aft Cof G.

w..

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2001\12\10@070236 by Roman Black

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Alexandre Domingos F. Souza wrote:
>
> >Roman said -
> >> As much respect as I have for the Carmack brothers
> >> and their amazing programming abilities I doubt John's
> >> (and staffs) mechanical engineering skills looking
> >> at some of their "flying machine" prototypes.
>
>         Ah...they are not relatives ;o) Just for the sake of curiosity! :o)


Huh?? Are you serious? John and Adrian?
-Roman

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2001\12\10@093550 by Roman Black

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Russell McMahon wrote:

> You mentioned "ground affect" below. I suspect this applies much more to a
> craft which uses air displacement as its main motive force and which has  a
> large area over which it distributes its air into (ie under the rotor
> "shadow" ). In the case of helicopters they tend to turn into hovercraft
> when the ground deflects and traps the downwards air from the rotor. Many
> accidents have been caused by this effect.  In the case of a rocket there
> will indeed be some potential effect from exhaust products being deflected
> by the ground but the pressure build up will be minimal compared to a
> helicopter and the rocket is NOT "ingesting" external air to act as its
> reaction mass - any ground effect would be that which acted on thge
> superstructure plus, perhaps, a minimal rsult from increased local pressure
> on the rocket nozzle exhaust conditions.


Maybe i'm mistaken but one of the videos you
posted links to seemed to be suffering from
real obvious ground effect instability when it
was trying to land, when the rockets got maybe
6 inches from the ground.

I just looked at it and thought "rocket position
redesign". Obviously the crew there thought
"faster more expensive control computer".
$8000 US for the control computer?? Wow.
I'm sure you could use one PIC, any takers guys?
<grin>
-Roman

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2001\12\10@105239 by Sean H. Breheny

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It appears that Boeing (in the 50s) didn't frown on it too much, at least
in demonstrations :-)

Sean

At 12:11 AM 12/11/01 +1300, you wrote:
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2001\12\10@150502 by Russell McMahon

picon face
> Maybe i'm mistaken but one of the videos you
> posted links to seemed to be suffering from
> real obvious ground effect instability when it
> was trying to land, when the rockets got maybe
> 6 inches from the ground.

Could be the case at 6" off. As likely though to be human operator on
joystick trying to juggle landing. Maybe not.

> I just looked at it and thought "rocket position
> redesign". Obviously the crew there thought
> "faster more expensive control computer".
> $8000 US for the control computer?? Wow.
> I'm sure you could use one PIC, any takers guys?

I don't think the computer onboard is quite in that class!.
The main single "electronics" cost onboard in a Crossbow brand 6DOF inertial
navigatin unit - laser gyros and accelrometers. About $US5000 AFAIR.

               Russell

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2001\12\11@165951 by Peter L. Peres

picon face
> > And this is very common! But they say that's impossible in a real
> > heli, why?!?
>
> Insuficient huevos?

Afaik most normal helis do not have stunt rated fuel systems and the
controls (gyros etc) can go crazy from the inversion, besides flaming out
a turbine in inverted flight at <1000 feet must be great "fun". But I am
not a pilot...

There are at least two real helis that I think do loops. One is an
European (German) one and the other is American.

Peter

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2001\12\12@203306 by Alexandre Domingos F. Souza

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>At 05:50 AM 12/10/01 -0200, Alexandre Domingos F. Souza wrote:
>> >Note - I have seen photos of model helicopters being flown inverted by
>> >suitably expert pilots.
>> >The cyclic has to be capable of suitable range to allow blade pitch to apply
>> >vertical "lift" in the opposite direction to normal.
>>         And this is very common! But they say that's impossible in a real
>> heli, why?!?
>Insuficient huevos?

       HUauhauhauha! But imagine, if it is hard as hell to do in a model copter, a single failure in a real copter would make a mess. BTW, I cite duke nukem: What a mess! ;oD



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2001\12\12@204327 by Alexandre Domingos F. Souza

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>>         Ah...they are not relatives ;o) Just for the sake of curiosity! :o)
>Huh?? Are you serious? John and Adrian?
>-Roman

       Yep, it was written in the first FAQ of DOOM, if I'm not wrong. The first thing I though reading the list of gods who did the game, was that adrian and John Carmack were brothers, but it wasn't stated so.

       Maybe a good reading of some ID software faqs ;o) http://www.idsoftware.com ;oD


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