A while back, I asked about whether Virgin Galactic's "plane" could be upgraded to ballistically do suborbital and be useful to travel from A
to B. The answers were "not even close" (and that was understatement
since it reaches 100km altitude with speed of 0, and doing New York
Sydney ballistically requires near-orbital speed and thus heat shields).
So now I ask about flying A to B more conventionally with "wings".
Lets assume one had magical engines that suck in vacuum and pushed it to
the back to generate any thrust we wanted. (some pixie dust may be
involved :-).
Say we fitted those engines on a Concorde.
Concorde ezperienced tolerable skin heating of X° cruising at Mach 2 at 60,000 feet.
Could one raise altitude and maintain lift by increasing speed all the
way to near Kaman line?
Would lift generated by wings and heating of skin have linear
relationships since both depend on airspeed and density of air? or would
skin heating increase at faster rate than lift as you scale altitude/airspeed?
aka: if the goal is just to maintain lift to keep weight of Concorde at
same altutude, can you raise aotutude and speed while keeping skin
heating to basically the same X°? (goal is not to go as fast as
possible, just keep flying but at higher speed/altitude).
From aerodynamics point of view, would the shape of Concorde scale to
higher speeds/higher altitude if the increased speed matches the need to maiintain the same aerodynamic lift generation?
Would speed needed to generate lift from such wings scale to near
orbital speed well below Kaman line or near it?
I assume someone has simulated a Concorde and done what speed is needed
at what altitude to maintain lift? Curious on how high/fast the
airedynamci plane could fly if you remove the engine limitations from equation.
From a descent point of view, is it correct to state that as long as the plane "flies" (aka its weight carried by lift geerated by wings) it can
use the friction to slow it down (engines generate 0 thrust) so it can progressively descend while always keeping a speed that doesn't exceed heating limitations for skin?
Hypersonic craft don't seem to look much like a Concorde.
<URL:https://en.wikipedia.org/wiki/NASA_X-43> <URL:https://en.wikipedia.org/wiki/Boeing_X-51_Waverider>
On 2021-10-15 03:16, Snidely wrote:
Hypersonic craft don't seem to look much like a Concorde.
<URL:https://en.wikipedia.org/wiki/NASA_X-43>
<URL:https://en.wikipedia.org/wiki/Boeing_X-51_Waverider>
But my question was more about taking more conventional delta wing and
seeing how high/fast it could go (assuming magical engines that work at
any altitude), and not for a 10 second joy ride to nowhere in a rocket ,
but for a multi hour flight that transports people over long distances.
Based on the difference in wing and body shape, I'm going to say "Mach
2, but maybe not even Mach 3". The Concorde has a /lot/ of surface
area. Much more than the Mach 2 F-104 Starfighter.
On 2021-10-15 16:35, Snidely wrote:
Based on the difference in wing and body shape, I'm going to say "Mach
2, but maybe not even Mach 3". The Concorde has a /lot/ of surface
area. Much more than the Mach 2 F-104 Starfighter.
Concorde carries 100 passengers. A military fighter carries one or maybe
2. So obviously, you need bigger wings to generate more lift as you
carrier bigger load.
And bigger wings mean more drag, which means more heating. Does drag
got up as V-squared? Is the Concorde made out of vanadium?
On 2021-10-15 20:23, Snidely wrote:
And bigger wings mean more drag, which means more heating. Does drag
got up as V-squared? Is the Concorde made out of vanadium?
My question pertains exactly to this.
If plane supports the heat at Mach 2 at 60,000feet, would it sustain
the same heat if it climbed to say 80,000 and accelerated so that wings
would produce equal amount of lift as it did at Mach 2 at 60,000 ?
If the wings generate the same amount of lift, wouldn't that mean equal amount of drag and thus heating?
Again, I am not asking about accelerating the Concorde to a gazillion
kmh or mach 10. Wondering if you exclude engine limitations, you could
make it climb much higher and go at higher speed to match the lift/drag/heating it got at Mach 2 at 60,000.
On 2021-10-15 20:23, Snidely wrote:
And bigger wings mean more drag, which means more heating. Does drag
got up as V-squared? Is the Concorde made out of vanadium?
My question pertains exactly to this.
If plane supports the heat at Mach 2 at 60,000feet, would it sustain
the same heat if it climbed to say 80,000 and accelerated so that wings
would produce equal amount of lift as it did at Mach 2 at 60,000 ?
If the wings generate the same amount of lift, wouldn't that mean equal amount of drag and thus heating?
Again, I am not asking about accelerating the Concorde to a gazillion
kmh or mach 10. Wondering if you exclude engine limitations, you could
make it climb much higher and go at higher speed to match the lift/drag/heating it got at Mach 2 at 60,000.
If I recall correctly, heating goes up with speed to the power three.
one for the amount of molecules you hit. Again, if I recall correctly,
lift is only proportional to the square of the speed.
Same goes for your question about wings producing lift. Lift never goes
down to zero. You could theoretically get lift with wings at the
altitude of ISS. It is only that you would need to go at about thirty
million times orbital speed to have enough aero-dynamic lift to hold
your weight.
On 2021-10-16 11:29, Alain Fournier wrote:
If I recall correctly, heating goes up with speed to the power three.
one for the amount of molecules you hit. Again, if I recall correctly,
lift is only proportional to the square of the speed.
Thanks.
However, how does that work as you approach Karman? Skin heating above
it is basically 0, right?
What sort of math/physics kick in to start reduction of heating as you increase speed/altitude such that you get to 0 heating above Karman?
(Also I assume wings would eventually stop producing lift at speeds that
are too high for their design and air too thin for their design). But am curious on what the limits would be in terms of altitude and speed for "flight". (since suborbital really requires orbiutal class rocket and
that makes for New Yor to Sydney not being realistic).
An interesting side note about this is that if you keep going faster
and higher in order have the same lift, you should reach approximately orbital speed at 100 km. So at that point you are no longer flying but orbiting. That is the reasoning behind the definition of the Karman
line. You can't fly above 100 km because to fly there, you need to
reach orbital speed and therefore you are orbiting not flying. And you
can't orbit below the Karman line because at orbital speed below the
Karman line you have enough lift to fly which means you will also have
enough drag that you won't orbit.
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