• Flying in space

    From JF Mezei@21:1/5 to All on Thu Oct 14 18:05:04 2021
    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?

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  • From Snidely@21:1/5 to All on Fri Oct 15 00:16:27 2021
    JF Mezei is guilty of <lQ1aJ.185767$rl3.183257@fx45.iad> as of
    10/14/2021 3:05:04 PM
    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>

    /dps

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  • From JF Mezei@21:1/5 to Snidely on Fri Oct 15 13:08:49 2021
    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.

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  • From Snidely@21:1/5 to All on Fri Oct 15 13:35:48 2021
    Just this Friday, JF Mezei explained that ...
    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.

    BTW, Jalopnik.com has an article about a CF-104D that's for sale, if
    you want to do some experimenting.

    /dps


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  • From JF Mezei@21:1/5 to Snidely on Fri Oct 15 18:19:57 2021
    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.

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  • From Snidely@21:1/5 to All on Fri Oct 15 17:23:36 2021
    Just this Friday, JF Mezei puzzled about:
    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?

    /dps

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    does for Arnold Lund in California or Richard Rothman in Baltimore, are
    the questions -- old and new, good and bad -- this newest tool lets us
    ask. (R. Lerhman, CSMonitor.com)

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  • From JF Mezei@21:1/5 to Snidely on Sat Oct 16 04:12:53 2021
    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.

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  • From Alain Fournier@21:1/5 to JF Mezei on Sat Oct 16 11:29:17 2021
    On Oct/16/2021 at 04:12, JF Mezei wrote :
    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.
    The energy of a collision with a molecule of air goes up with the square
    of the speed. But since you hit twice as much air when you go twice the
    speed you get the power three, two for the energy per molecule hit and
    one for the amount of molecules you hit. Again, if I recall correctly,
    lift is only proportional to the square of the speed. In both cases,
    heating and lift are proportional to air density. So as you go faster,
    you can go higher (lower air density) and still have the same lift, but
    you have more heating. Or you could go much higher and have the same
    heating, but then you lose some lift, so you can't do that very much.

    So the answer to your question is no, you can't keep the same heating
    and lift by going higher.

    In your example with mach 2 at 60,000 feet. If you go to 80,000 feet,
    you have roughly half the air pressure you had at 60,000 feet, so you
    would need to go at roughly mach 2*sqrt(2) to have the same lift. But
    then your heat load would increase by sqrt(2). The heat load being
    multiplied by sqrt(2) to the power three because of higher speed and
    divided by 2 because of lower air pressure. This is only a rough
    approximation, according to the shape of the plane you can have
    different effect sizes, but as a first approximation this should give
    you an idea of what is going on.


    Alain Fournier

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  • From Alain Fournier@21:1/5 to JF Mezei on Sat Oct 16 11:35:19 2021
    On Oct/16/2021 at 04:12, JF Mezei wrote :
    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.

    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.


    Alain Fournier

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  • From JF Mezei@21:1/5 to Alain Fournier on Sat Oct 16 17:31:00 2021
    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).

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  • From Alain Fournier@21:1/5 to Alain Fournier on Sat Oct 16 19:59:42 2021
    On Oct/16/2021 at 19:32, Alain Fournier wrote :

    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.

    Oups! Thirty million times orbital speed is more than the speed of light
    so that wouldn't work. At very close to the speed of light you could get
    some lift (lift would increase due to some relativistic effects). But of
    course heating would vaporize your wings if you have get lift because of relativistic effects near the speed of light.


    Alain Fournier

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  • From Alain Fournier@21:1/5 to JF Mezei on Sat Oct 16 19:32:54 2021
    On Oct/16/2021 at 17:31, JF Mezei wrote :
    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).

    At the Karman line, if you are moving at orbital speed which is also approximately the speed you need to have enough aero-dynamic lift to
    support your weight, then heating is very severe. But every six
    kilo-meters higher you go, the density of the atmosphere decreases by a
    factor of about two, and therefore if you stay at the same speed the
    heating is divided by two. So at 160 kilo-meters, you have divided by
    1000 your heating and you are now in an orbit that is sustainable for
    for a short time. You never get zero heating, ISS is heated by
    aerodynamic drag, but by factor of about a trillionth of the already
    very low heating it would have at an altitude of 160 kilo-meters.

    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.


    Alain Fournier

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  • From Otto J. Makela@21:1/5 to Alain Fournier on Sun Oct 17 15:30:11 2021
    Alain Fournier <alain245@videotron.ca> wrote:

    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.

    In the final chapter of his autobiography Kármán addresses the issue of
    the edge of outer space:
    Where space begins… can actually be determined by the speed of
    the space vehicle and its altitude above the Earth. Consider,
    for instance, the record flight of Captain Iven Carl Kincheloe
    Jr. in an X-2 rocket plane. Kincheloe flew 2000 miles per hour
    (3,200 km/h) at 126,000 feet (38,500 m), or 24 miles up. At this
    altitude and speed, aerodynamic lift still carries 98 percent of
    the weight of the plane, and only two percent is carried by
    inertia, or Kepler Force, as space scientists call it. But at
    300,000 feet (91,440 m) or 57 miles up, this relationship is
    reversed because there is no longer any air to contribute lift:
    only inertia prevails. This is certainly a physical boundary,
    where aerodynamics stops and astronautics begins, and so I
    thought why should it not also be a jurisdictional boundary?
    Haley has kindly called it the Kármán Jurisdictional Line. Below
    this line, space belongs to each country. Above this level there
    would be free space.
    -- https://en.wikipedia.org/wiki/Karman_line
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