How were these pictures of spacecraft wind tunnel testing taken?
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The picture below from this answer shows four spacecraft wind tunnel tests from the 1950s. In addition to the test object, the bow shock and turbulence are clearly visible.
How is this visualization accomplished?
- Is the medium air, or a denser fluid such as water?
- Is there a pigment added to the fluid to help visualization?
- Is there special lighting, such as polarized light?
- Any notable camera tricks?
- Is the 3-D nature of the test object more significant than being a thick 2-D object?
spacecraft-development
asked May 26 at 13:10
DrSheldonDrSheldon
16.5k5 gold badges65 silver badges131 bronze badges
$endgroup$
add a comment
|
$begingroup$
The picture below from this answer shows four spacecraft wind tunnel tests from the 1950s. In addition to the test object, the bow shock and turbulence are clearly visible.
How is this visualization accomplished?
- Is the medium air, or a denser fluid such as water?
- Is there a pigment added to the fluid to help visualization?
- Is there special lighting, such as polarized light?
- Any notable camera tricks?
- Is the 3-D nature of the test object more significant than being a thick 2-D object?
spacecraft-development
asked May 26 at 13:10
DrSheldonDrSheldon
16.5k5 gold badges65 silver badges131 bronze badges
$endgroup$
$begingroup$
One of my former college instructor's PhD thesis was manned vehicle re-entry in the 1950s or 1960s after Sputnik. He said he simulated re-entry by firing a small projectile and piercing a membrane. He told me the US Air Force tried to get Florida State to cancel his funding because his experiments costs about $30,000 or $50,000 at the time; while the US Air Force budget for the same was multi-million dollars. After his PhD and space program experience, he went on the the NSA. Operation Ivy Bells was one of his programs.
$endgroup$
– jww
May 28 at 10:09
add a comment
|
$begingroup$
The picture below from this answer shows four spacecraft wind tunnel tests from the 1950s. In addition to the test object, the bow shock and turbulence are clearly visible.
How is this visualization accomplished?
- Is the medium air, or a denser fluid such as water?
- Is there a pigment added to the fluid to help visualization?
- Is there special lighting, such as polarized light?
- Any notable camera tricks?
- Is the 3-D nature of the test object more significant than being a thick 2-D object?
spacecraft-development
asked May 26 at 13:10
DrSheldonDrSheldon
16.5k5 gold badges65 silver badges131 bronze badges
$endgroup$
The picture below from this answer shows four spacecraft wind tunnel tests from the 1950s. In addition to the test object, the bow shock and turbulence are clearly visible.
How is this visualization accomplished?
- Is the medium air, or a denser fluid such as water?
- Is there a pigment added to the fluid to help visualization?
- Is there special lighting, such as polarized light?
- Any notable camera tricks?
- Is the 3-D nature of the test object more significant than being a thick 2-D object?
spacecraft-development
spacecraft-development
asked May 26 at 13:10
DrSheldonDrSheldon
16.5k5 gold badges65 silver badges131 bronze badges
asked May 26 at 13:10
DrSheldonDrSheldon
16.5k5 gold badges65 silver badges131 bronze badges
asked May 26 at 13:10
DrSheldonDrSheldon
16.5k5 gold badges65 silver badges131 bronze badges
asked May 26 at 13:10
DrSheldonDrSheldon
16.5k5 gold badges65 silver badges131 bronze badges
asked May 26 at 13:10
DrSheldonDrSheldon
16.5k5 gold badges65 silver badges131 bronze badges
16.5k5 gold badges65 silver badges131 bronze badges
$begingroup$
One of my former college instructor's PhD thesis was manned vehicle re-entry in the 1950s or 1960s after Sputnik. He said he simulated re-entry by firing a small projectile and piercing a membrane. He told me the US Air Force tried to get Florida State to cancel his funding because his experiments costs about $30,000 or $50,000 at the time; while the US Air Force budget for the same was multi-million dollars. After his PhD and space program experience, he went on the the NSA. Operation Ivy Bells was one of his programs.
$endgroup$
– jww
May 28 at 10:09
add a comment
|
$begingroup$
One of my former college instructor's PhD thesis was manned vehicle re-entry in the 1950s or 1960s after Sputnik. He said he simulated re-entry by firing a small projectile and piercing a membrane. He told me the US Air Force tried to get Florida State to cancel his funding because his experiments costs about $30,000 or $50,000 at the time; while the US Air Force budget for the same was multi-million dollars. After his PhD and space program experience, he went on the the NSA. Operation Ivy Bells was one of his programs.
$endgroup$
– jww
May 28 at 10:09
$begingroup$
One of my former college instructor's PhD thesis was manned vehicle re-entry in the 1950s or 1960s after Sputnik. He said he simulated re-entry by firing a small projectile and piercing a membrane. He told me the US Air Force tried to get Florida State to cancel his funding because his experiments costs about $30,000 or $50,000 at the time; while the US Air Force budget for the same was multi-million dollars. After his PhD and space program experience, he went on the the NSA. Operation Ivy Bells was one of his programs.
$endgroup$
– jww
May 28 at 10:09
$begingroup$
One of my former college instructor's PhD thesis was manned vehicle re-entry in the 1950s or 1960s after Sputnik. He said he simulated re-entry by firing a small projectile and piercing a membrane. He told me the US Air Force tried to get Florida State to cancel his funding because his experiments costs about $30,000 or $50,000 at the time; while the US Air Force budget for the same was multi-million dollars. After his PhD and space program experience, he went on the the NSA. Operation Ivy Bells was one of his programs.
$endgroup$
– jww
May 28 at 10:09
add a comment
|
2 Answers
2
active
oldest
votes
$begingroup$
These appear to be Schlieren photography. Schlieren photography uses a collimated light source to highlight the refractive index changes brought on by density gradients in a fluid - in other words, it can visualize the shockwaves in air that are produced by different shapes.
The simplest technique shines collimated light past the object of interest, and places a knife edge at the focal point to block a portion of the light. Light beams that pass through density gradients are bent away from the path, and get blocked by the knife edge. The higher density zones are left as dark regions on the image, as their light was intercepted by the knife edge.
(image NASA)
edited May 27 at 12:07
Hohmannfan♦
13.5k1 gold badge51 silver badges108 bronze badges
answered May 26 at 13:21
SaibooguSaiboogu
5,42429 silver badges34 bronze badges
$endgroup$
5
$begingroup$
Schlieren photography is a fairly old method developed in 1864 by the german chemist and physicist August Toepler. This is why the german word 'Schlieren' is used. It may be used in transparent liquids too.
$endgroup$
– Uwe
May 26 at 14:25
4
$begingroup$
Both Veritasium and Smarter Every Day Youtube channels have done some great videos on (using) the Schlieren effect: 1, 2, 3, 4 and 5
$endgroup$
– Jan Doggen
May 27 at 20:12
add a comment
|
$begingroup$
@Saiboogu's answer is of course correct, this looks to be classic Schlieren photography.
It is notable that NASA has also developed two methods to generate faux-Schlieren images or "synthetic Schlieren" images without the need of special optical systems and collimated beams of light inside wind tunnels.
These techniques can be applied to real high speed aircraft or spacecraft moving in the Earth's atmosphere. Instead of generating light/dark bands from refraction of the collimated, uniform-intensity beam directly, they instead image a finely textured background as the craft passes in front of it. By using "optical flow" or other techniques they map small displacements of the texture due to the refraction, and plot the deflection map as intensity. The result can in some cases be better than traditional Schlieren imaging because they can reconstruct the vector direction of the displacement; the air density gradient.
NASA pioneered the use of the Sun, filtered through a narrow line filter (hydrogen-alpha or calcium-K) to produce the textured background. This could then be imaged from the ground by the craft passing between the ground cameras and the Sun.
Recently however they have also published results using a textured ground pattern in the desert, with a down-looking camera viewing from an aircraft above the craft to be measured.
Ground texture as background
From this answer:
Thanks to @Federico for finding and linking to this video!
Since they are measuring a two-dimensional displacement field, in a similar way to an optical flow measurement, they get a vector field rather than an intensity field for traditional schlieren imaging. That means they can play with the gradient in new ways.
Left: Schlieren image dramatically displays the shock wave of a supersonic jet flying over the Mojave Desert. Averaging multiple frames produce a low-noise picture of the shock waves. Right: Horizontal gradient reveals tip vortices from the same image set.
Solar texture as background
From this answer:
Updated camera testing on the ground, screenshot from NASA Supersonic Flights Validate Flightworthiness for Future Schlieren Imaging
answered May 27 at 0:03
uhohuhoh
54.2k26 gold badges213 silver badges682 bronze badges
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2 Answers
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2 Answers
2
active
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$begingroup$
These appear to be Schlieren photography. Schlieren photography uses a collimated light source to highlight the refractive index changes brought on by density gradients in a fluid - in other words, it can visualize the shockwaves in air that are produced by different shapes.
The simplest technique shines collimated light past the object of interest, and places a knife edge at the focal point to block a portion of the light. Light beams that pass through density gradients are bent away from the path, and get blocked by the knife edge. The higher density zones are left as dark regions on the image, as their light was intercepted by the knife edge.
(image NASA)
edited May 27 at 12:07
Hohmannfan♦
13.5k1 gold badge51 silver badges108 bronze badges
answered May 26 at 13:21
SaibooguSaiboogu
5,42429 silver badges34 bronze badges
$endgroup$
5
$begingroup$
Schlieren photography is a fairly old method developed in 1864 by the german chemist and physicist August Toepler. This is why the german word 'Schlieren' is used. It may be used in transparent liquids too.
$endgroup$
– Uwe
May 26 at 14:25
4
$begingroup$
Both Veritasium and Smarter Every Day Youtube channels have done some great videos on (using) the Schlieren effect: 1, 2, 3, 4 and 5
$endgroup$
– Jan Doggen
May 27 at 20:12
add a comment
|
$begingroup$
These appear to be Schlieren photography. Schlieren photography uses a collimated light source to highlight the refractive index changes brought on by density gradients in a fluid - in other words, it can visualize the shockwaves in air that are produced by different shapes.
The simplest technique shines collimated light past the object of interest, and places a knife edge at the focal point to block a portion of the light. Light beams that pass through density gradients are bent away from the path, and get blocked by the knife edge. The higher density zones are left as dark regions on the image, as their light was intercepted by the knife edge.
(image NASA)
edited May 27 at 12:07
Hohmannfan♦
13.5k1 gold badge51 silver badges108 bronze badges
answered May 26 at 13:21
SaibooguSaiboogu
5,42429 silver badges34 bronze badges
$endgroup$
5
$begingroup$
Schlieren photography is a fairly old method developed in 1864 by the german chemist and physicist August Toepler. This is why the german word 'Schlieren' is used. It may be used in transparent liquids too.
$endgroup$
– Uwe
May 26 at 14:25
4
$begingroup$
Both Veritasium and Smarter Every Day Youtube channels have done some great videos on (using) the Schlieren effect: 1, 2, 3, 4 and 5
$endgroup$
– Jan Doggen
May 27 at 20:12
add a comment
|
$begingroup$
These appear to be Schlieren photography. Schlieren photography uses a collimated light source to highlight the refractive index changes brought on by density gradients in a fluid - in other words, it can visualize the shockwaves in air that are produced by different shapes.
The simplest technique shines collimated light past the object of interest, and places a knife edge at the focal point to block a portion of the light. Light beams that pass through density gradients are bent away from the path, and get blocked by the knife edge. The higher density zones are left as dark regions on the image, as their light was intercepted by the knife edge.
(image NASA)
edited May 27 at 12:07
Hohmannfan♦
13.5k1 gold badge51 silver badges108 bronze badges
answered May 26 at 13:21
SaibooguSaiboogu
5,42429 silver badges34 bronze badges
$endgroup$
These appear to be Schlieren photography. Schlieren photography uses a collimated light source to highlight the refractive index changes brought on by density gradients in a fluid - in other words, it can visualize the shockwaves in air that are produced by different shapes.
The simplest technique shines collimated light past the object of interest, and places a knife edge at the focal point to block a portion of the light. Light beams that pass through density gradients are bent away from the path, and get blocked by the knife edge. The higher density zones are left as dark regions on the image, as their light was intercepted by the knife edge.
(image NASA)
edited May 27 at 12:07
Hohmannfan♦
13.5k1 gold badge51 silver badges108 bronze badges
answered May 26 at 13:21
SaibooguSaiboogu
5,42429 silver badges34 bronze badges
edited May 27 at 12:07
Hohmannfan♦
13.5k1 gold badge51 silver badges108 bronze badges
edited May 27 at 12:07
Hohmannfan♦
13.5k1 gold badge51 silver badges108 bronze badges
edited May 27 at 12:07
Hohmannfan♦
13.5k1 gold badge51 silver badges108 bronze badges
13.5k1 gold badge51 silver badges108 bronze badges
answered May 26 at 13:21
SaibooguSaiboogu
5,42429 silver badges34 bronze badges
answered May 26 at 13:21
SaibooguSaiboogu
5,42429 silver badges34 bronze badges
answered May 26 at 13:21
SaibooguSaiboogu
5,42429 silver badges34 bronze badges
5,42429 silver badges34 bronze badges
5
$begingroup$
Schlieren photography is a fairly old method developed in 1864 by the german chemist and physicist August Toepler. This is why the german word 'Schlieren' is used. It may be used in transparent liquids too.
$endgroup$
– Uwe
May 26 at 14:25
4
$begingroup$
Both Veritasium and Smarter Every Day Youtube channels have done some great videos on (using) the Schlieren effect: 1, 2, 3, 4 and 5
$endgroup$
– Jan Doggen
May 27 at 20:12
add a comment
|
5
$begingroup$
Schlieren photography is a fairly old method developed in 1864 by the german chemist and physicist August Toepler. This is why the german word 'Schlieren' is used. It may be used in transparent liquids too.
$endgroup$
– Uwe
May 26 at 14:25
4
$begingroup$
Both Veritasium and Smarter Every Day Youtube channels have done some great videos on (using) the Schlieren effect: 1, 2, 3, 4 and 5
$endgroup$
– Jan Doggen
May 27 at 20:12
5
5
$begingroup$
Schlieren photography is a fairly old method developed in 1864 by the german chemist and physicist August Toepler. This is why the german word 'Schlieren' is used. It may be used in transparent liquids too.
$endgroup$
– Uwe
May 26 at 14:25
$begingroup$
Schlieren photography is a fairly old method developed in 1864 by the german chemist and physicist August Toepler. This is why the german word 'Schlieren' is used. It may be used in transparent liquids too.
$endgroup$
– Uwe
May 26 at 14:25
4
4
$begingroup$
Both Veritasium and Smarter Every Day Youtube channels have done some great videos on (using) the Schlieren effect: 1, 2, 3, 4 and 5
$endgroup$
– Jan Doggen
May 27 at 20:12
$begingroup$
Both Veritasium and Smarter Every Day Youtube channels have done some great videos on (using) the Schlieren effect: 1, 2, 3, 4 and 5
$endgroup$
– Jan Doggen
May 27 at 20:12
add a comment
|
$begingroup$
@Saiboogu's answer is of course correct, this looks to be classic Schlieren photography.
It is notable that NASA has also developed two methods to generate faux-Schlieren images or "synthetic Schlieren" images without the need of special optical systems and collimated beams of light inside wind tunnels.
These techniques can be applied to real high speed aircraft or spacecraft moving in the Earth's atmosphere. Instead of generating light/dark bands from refraction of the collimated, uniform-intensity beam directly, they instead image a finely textured background as the craft passes in front of it. By using "optical flow" or other techniques they map small displacements of the texture due to the refraction, and plot the deflection map as intensity. The result can in some cases be better than traditional Schlieren imaging because they can reconstruct the vector direction of the displacement; the air density gradient.
NASA pioneered the use of the Sun, filtered through a narrow line filter (hydrogen-alpha or calcium-K) to produce the textured background. This could then be imaged from the ground by the craft passing between the ground cameras and the Sun.
Recently however they have also published results using a textured ground pattern in the desert, with a down-looking camera viewing from an aircraft above the craft to be measured.
Ground texture as background
From this answer:
Thanks to @Federico for finding and linking to this video!
Since they are measuring a two-dimensional displacement field, in a similar way to an optical flow measurement, they get a vector field rather than an intensity field for traditional schlieren imaging. That means they can play with the gradient in new ways.
Left: Schlieren image dramatically displays the shock wave of a supersonic jet flying over the Mojave Desert. Averaging multiple frames produce a low-noise picture of the shock waves. Right: Horizontal gradient reveals tip vortices from the same image set.
Solar texture as background
From this answer:
Updated camera testing on the ground, screenshot from NASA Supersonic Flights Validate Flightworthiness for Future Schlieren Imaging
answered May 27 at 0:03
uhohuhoh
54.2k26 gold badges213 silver badges682 bronze badges
$endgroup$
add a comment
|
$begingroup$
@Saiboogu's answer is of course correct, this looks to be classic Schlieren photography.
It is notable that NASA has also developed two methods to generate faux-Schlieren images or "synthetic Schlieren" images without the need of special optical systems and collimated beams of light inside wind tunnels.
These techniques can be applied to real high speed aircraft or spacecraft moving in the Earth's atmosphere. Instead of generating light/dark bands from refraction of the collimated, uniform-intensity beam directly, they instead image a finely textured background as the craft passes in front of it. By using "optical flow" or other techniques they map small displacements of the texture due to the refraction, and plot the deflection map as intensity. The result can in some cases be better than traditional Schlieren imaging because they can reconstruct the vector direction of the displacement; the air density gradient.
NASA pioneered the use of the Sun, filtered through a narrow line filter (hydrogen-alpha or calcium-K) to produce the textured background. This could then be imaged from the ground by the craft passing between the ground cameras and the Sun.
Recently however they have also published results using a textured ground pattern in the desert, with a down-looking camera viewing from an aircraft above the craft to be measured.
Ground texture as background
From this answer:
Thanks to @Federico for finding and linking to this video!
Since they are measuring a two-dimensional displacement field, in a similar way to an optical flow measurement, they get a vector field rather than an intensity field for traditional schlieren imaging. That means they can play with the gradient in new ways.
Left: Schlieren image dramatically displays the shock wave of a supersonic jet flying over the Mojave Desert. Averaging multiple frames produce a low-noise picture of the shock waves. Right: Horizontal gradient reveals tip vortices from the same image set.
Solar texture as background
From this answer:
Updated camera testing on the ground, screenshot from NASA Supersonic Flights Validate Flightworthiness for Future Schlieren Imaging
answered May 27 at 0:03
uhohuhoh
54.2k26 gold badges213 silver badges682 bronze badges
$endgroup$
add a comment
|
$begingroup$
@Saiboogu's answer is of course correct, this looks to be classic Schlieren photography.
It is notable that NASA has also developed two methods to generate faux-Schlieren images or "synthetic Schlieren" images without the need of special optical systems and collimated beams of light inside wind tunnels.
These techniques can be applied to real high speed aircraft or spacecraft moving in the Earth's atmosphere. Instead of generating light/dark bands from refraction of the collimated, uniform-intensity beam directly, they instead image a finely textured background as the craft passes in front of it. By using "optical flow" or other techniques they map small displacements of the texture due to the refraction, and plot the deflection map as intensity. The result can in some cases be better than traditional Schlieren imaging because they can reconstruct the vector direction of the displacement; the air density gradient.
NASA pioneered the use of the Sun, filtered through a narrow line filter (hydrogen-alpha or calcium-K) to produce the textured background. This could then be imaged from the ground by the craft passing between the ground cameras and the Sun.
Recently however they have also published results using a textured ground pattern in the desert, with a down-looking camera viewing from an aircraft above the craft to be measured.
Ground texture as background
From this answer:
Thanks to @Federico for finding and linking to this video!
Since they are measuring a two-dimensional displacement field, in a similar way to an optical flow measurement, they get a vector field rather than an intensity field for traditional schlieren imaging. That means they can play with the gradient in new ways.
Left: Schlieren image dramatically displays the shock wave of a supersonic jet flying over the Mojave Desert. Averaging multiple frames produce a low-noise picture of the shock waves. Right: Horizontal gradient reveals tip vortices from the same image set.
Solar texture as background
From this answer:
Updated camera testing on the ground, screenshot from NASA Supersonic Flights Validate Flightworthiness for Future Schlieren Imaging
answered May 27 at 0:03
uhohuhoh
54.2k26 gold badges213 silver badges682 bronze badges
$endgroup$
@Saiboogu's answer is of course correct, this looks to be classic Schlieren photography.
It is notable that NASA has also developed two methods to generate faux-Schlieren images or "synthetic Schlieren" images without the need of special optical systems and collimated beams of light inside wind tunnels.
These techniques can be applied to real high speed aircraft or spacecraft moving in the Earth's atmosphere. Instead of generating light/dark bands from refraction of the collimated, uniform-intensity beam directly, they instead image a finely textured background as the craft passes in front of it. By using "optical flow" or other techniques they map small displacements of the texture due to the refraction, and plot the deflection map as intensity. The result can in some cases be better than traditional Schlieren imaging because they can reconstruct the vector direction of the displacement; the air density gradient.
NASA pioneered the use of the Sun, filtered through a narrow line filter (hydrogen-alpha or calcium-K) to produce the textured background. This could then be imaged from the ground by the craft passing between the ground cameras and the Sun.
Recently however they have also published results using a textured ground pattern in the desert, with a down-looking camera viewing from an aircraft above the craft to be measured.
Ground texture as background
From this answer:
Thanks to @Federico for finding and linking to this video!
Since they are measuring a two-dimensional displacement field, in a similar way to an optical flow measurement, they get a vector field rather than an intensity field for traditional schlieren imaging. That means they can play with the gradient in new ways.
Left: Schlieren image dramatically displays the shock wave of a supersonic jet flying over the Mojave Desert. Averaging multiple frames produce a low-noise picture of the shock waves. Right: Horizontal gradient reveals tip vortices from the same image set.
Solar texture as background
From this answer:
Updated camera testing on the ground, screenshot from NASA Supersonic Flights Validate Flightworthiness for Future Schlieren Imaging
answered May 27 at 0:03
uhohuhoh
54.2k26 gold badges213 silver badges682 bronze badges
answered May 27 at 0:03
uhohuhoh
54.2k26 gold badges213 silver badges682 bronze badges
answered May 27 at 0:03
uhohuhoh
54.2k26 gold badges213 silver badges682 bronze badges
answered May 27 at 0:03
uhohuhoh
54.2k26 gold badges213 silver badges682 bronze badges
54.2k26 gold badges213 silver badges682 bronze badges
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One of my former college instructor's PhD thesis was manned vehicle re-entry in the 1950s or 1960s after Sputnik. He said he simulated re-entry by firing a small projectile and piercing a membrane. He told me the US Air Force tried to get Florida State to cancel his funding because his experiments costs about $30,000 or $50,000 at the time; while the US Air Force budget for the same was multi-million dollars. After his PhD and space program experience, he went on the the NSA. Operation Ivy Bells was one of his programs.
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– jww
May 28 at 10:09