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Where does space begin on planets without atmospheres?
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On Earth the Karman Line is used as the boundary of space, and I believe it is defined as the height where you would have to go faster than orbital speed in order to obtain aerodynamic lift. Therefore planets like Mars and Venus also have Karman Lines.
However, places like Mercury or the Moon have no atmosphere. Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights. How would you define the space boundary on these planets? Should it be defined as the minimum height where it is possible to complete one stable orbit?
orbit karman-line
asked 8 hours ago
TeslaK20
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up vote
4
down vote
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On Earth the Karman Line is used as the boundary of space, and I believe it is defined as the height where you would have to go faster than orbital speed in order to obtain aerodynamic lift. Therefore planets like Mars and Venus also have Karman Lines.
However, places like Mercury or the Moon have no atmosphere. Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights. How would you define the space boundary on these planets? Should it be defined as the minimum height where it is possible to complete one stable orbit?
orbit karman-line
asked 8 hours ago
TeslaK20
332
The lunar minimum height where it is possible to complete one stable orbit depends on lunar mascons.
– Uwe
8 hours ago
@Uwe the phrase "one stable orbit" doesn't even make sense. The idea of "stable" has to do with the ability of a body to orbit many times without significant changes in the orbit. One stable orbit doesn't really mean anything.
– uhoh
5 hours ago
add a comment |Â
up vote
4
down vote
favorite
up vote
4
down vote
favorite
On Earth the Karman Line is used as the boundary of space, and I believe it is defined as the height where you would have to go faster than orbital speed in order to obtain aerodynamic lift. Therefore planets like Mars and Venus also have Karman Lines.
However, places like Mercury or the Moon have no atmosphere. Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights. How would you define the space boundary on these planets? Should it be defined as the minimum height where it is possible to complete one stable orbit?
orbit karman-line
asked 8 hours ago
TeslaK20
332
On Earth the Karman Line is used as the boundary of space, and I believe it is defined as the height where you would have to go faster than orbital speed in order to obtain aerodynamic lift. Therefore planets like Mars and Venus also have Karman Lines.
However, places like Mercury or the Moon have no atmosphere. Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights. How would you define the space boundary on these planets? Should it be defined as the minimum height where it is possible to complete one stable orbit?
orbit karman-line
asked 8 hours ago
TeslaK20
332
asked 8 hours ago
TeslaK20
332
asked 8 hours ago
TeslaK20
332
asked 8 hours ago
TeslaK20
332
332
The lunar minimum height where it is possible to complete one stable orbit depends on lunar mascons.
– Uwe
8 hours ago
@Uwe the phrase "one stable orbit" doesn't even make sense. The idea of "stable" has to do with the ability of a body to orbit many times without significant changes in the orbit. One stable orbit doesn't really mean anything.
– uhoh
5 hours ago
add a comment |Â
The lunar minimum height where it is possible to complete one stable orbit depends on lunar mascons.
– Uwe
8 hours ago
@Uwe the phrase "one stable orbit" doesn't even make sense. The idea of "stable" has to do with the ability of a body to orbit many times without significant changes in the orbit. One stable orbit doesn't really mean anything.
– uhoh
5 hours ago
The lunar minimum height where it is possible to complete one stable orbit depends on lunar mascons.
– Uwe
8 hours ago
The lunar minimum height where it is possible to complete one stable orbit depends on lunar mascons.
– Uwe
8 hours ago
@Uwe the phrase "one stable orbit" doesn't even make sense. The idea of "stable" has to do with the ability of a body to orbit many times without significant changes in the orbit. One stable orbit doesn't really mean anything.
– uhoh
5 hours ago
@Uwe the phrase "one stable orbit" doesn't even make sense. The idea of "stable" has to do with the ability of a body to orbit many times without significant changes in the orbit. One stable orbit doesn't really mean anything.
– uhoh
5 hours ago
add a comment |Â
2 Answers
2
active
oldest
votes
up vote
21
down vote
Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights.
Why not? There's no essential difference between a high-eccentricity trajectory with an apolune of 1 meter and one with an apolune of 100 kilometers.
How would you define the space boundary on these planets?
If the body doesn't have an atmosphere dense enough for its Kármán line to be above the surface, space begins at the surface. What other sensible definition is there?
answered 7 hours ago
Russell Borogove
67.8k2210290
1
You may ask for an orbit above lunar hills, mountains and crater walls. An orbit being stable despite mascons.
– Uwe
7 hours ago
6
Stable orbit doesn't have much to do with it; you can't complete an orbit at the Kármán line without boost or lift.
– Russell Borogove
7 hours ago
@Uwe "space" and "orbit" are different things. Russell is right: space begins at the surface of the Moon. That's doesn't mean that you can orbit at the surface, though.
– RonJohn
1 hour ago
add a comment |Â
up vote
0
down vote
Where does space begin on planets without atmospheres?
Where the ratio κ=1 for the ion cyclotron and ion collision frequencies - for Earth that is 118 ± 0.3 km.
Source: "Rocketâ€Âbased measurements of ion velocity, neutral wind, and electric field in the collisional transition region of the auroral ionosphere", (April 7 2009), by L. Sangalli, D. J. Knudsen, M. F. Larsen, T. Zhan, R. F. Pfaff and D. Rowland.
See Wikipedia's webpage "Outer Space - Boundary":
"There is no clear boundary between Earth's atmosphere and space, as the density of the atmosphere gradually decreases as the altitude increases. There are several standard boundary designations, ...".
Where there is solid rock there is no outer space.
Where there is the vacuum of space, there is space.
If you had an object a hundred meters in diameter with a large cave you would have space in the cave, you certainly wouldn't have atmosphere, such a small object doesn't have enough gravity to hold enough hydrogen to constitute an atmosphere.
On Earth the Kármán Line is used as the boundary of space, and I believe it is defined as the height where you would have to go faster than orbital speed in order to obtain aerodynamic lift. Therefore planets like Mars and Venus also have Kármán Lines.
Source Wikipedia: "The Kármán line lies at at an altitude of 100 km (62 mi; 330,000 ft) above Earth's sea level and commonly represents the boundary between Earth's atmosphere and outer space. This definition is accepted by the Fédération aéronautique internationale (FAI), which is an international standard-setting and record-keeping body for aeronautics and astronautics.
The line is named after Theodore von Kármán (1881–1963), a Hungarian American engineer and physicist, who was active primarily in aeronautics and astronautics. He was the first person to calculate that the atmosphere around this altitude becomes too thin to support aeronautical flight, since a vehicle at this altitude would have to travel faster than orbital velocity to derive sufficient aerodynamic lift to support itself.".
The line defining the 'edge of space' for Earth at 100 km is convenient, just like international waters are 200 nautical miles from the baseline. Not everyone agrees on it, and it is not scientifically correct; it's agreed upon by treaty.
The line defining the 'edge of space' was determined to be 118 ± 0.3 km.
"Measured ion drifts in the 150–198 km and 92–105 km altitude ranges are consistent with $scriptsizeoverrightarrowE$ × $scriptsizeoverrightarrowB$ motion to within 16 m s$^−1$ rms and with neutral wind velocity to within 20 m s$^−1$, respectively. From these measurements we have calculated the ratio κ of the ion cyclotron and ion collision frequencies, finding κ = 1 at an altitude of 118 ± 0.3 km.
The transition between the two regimes is controlled by the ratio of ion cyclotron to ion collision frequencies, $κ_j = Ω_j/v_j$, where $j$ is a species index. Consequently, collision frequencies can be derived from independent measurements of electric and magnetic fields $scriptsizeoverrightarrowE$ and $scriptsizeoverrightarrowB$, bulk flow velocity $scriptsizeoverrightarrowE$, and neutral winds $scriptsizeoverrightarrowv_j$ [e.g., Egeland et al., 1973].
However, places like Mercury or the Moon have no atmosphere. Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights. How would you define the space boundary on these planets? Should it be defined as the minimum height where it is possible to complete one stable orbit?
This is answered above.
answered 35 mins ago
Rob
1,726221
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
21
down vote
Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights.
Why not? There's no essential difference between a high-eccentricity trajectory with an apolune of 1 meter and one with an apolune of 100 kilometers.
How would you define the space boundary on these planets?
If the body doesn't have an atmosphere dense enough for its Kármán line to be above the surface, space begins at the surface. What other sensible definition is there?
answered 7 hours ago
Russell Borogove
67.8k2210290
1
You may ask for an orbit above lunar hills, mountains and crater walls. An orbit being stable despite mascons.
– Uwe
7 hours ago
6
Stable orbit doesn't have much to do with it; you can't complete an orbit at the Kármán line without boost or lift.
– Russell Borogove
7 hours ago
@Uwe "space" and "orbit" are different things. Russell is right: space begins at the surface of the Moon. That's doesn't mean that you can orbit at the surface, though.
– RonJohn
1 hour ago
add a comment |Â
up vote
21
down vote
Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights.
Why not? There's no essential difference between a high-eccentricity trajectory with an apolune of 1 meter and one with an apolune of 100 kilometers.
How would you define the space boundary on these planets?
If the body doesn't have an atmosphere dense enough for its Kármán line to be above the surface, space begins at the surface. What other sensible definition is there?
answered 7 hours ago
Russell Borogove
67.8k2210290
1
You may ask for an orbit above lunar hills, mountains and crater walls. An orbit being stable despite mascons.
– Uwe
7 hours ago
6
Stable orbit doesn't have much to do with it; you can't complete an orbit at the Kármán line without boost or lift.
– Russell Borogove
7 hours ago
@Uwe "space" and "orbit" are different things. Russell is right: space begins at the surface of the Moon. That's doesn't mean that you can orbit at the surface, though.
– RonJohn
1 hour ago
add a comment |Â
up vote
21
down vote
up vote
21
down vote
Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights.
Why not? There's no essential difference between a high-eccentricity trajectory with an apolune of 1 meter and one with an apolune of 100 kilometers.
How would you define the space boundary on these planets?
If the body doesn't have an atmosphere dense enough for its Kármán line to be above the surface, space begins at the surface. What other sensible definition is there?
answered 7 hours ago
Russell Borogove
67.8k2210290
Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights.
Why not? There's no essential difference between a high-eccentricity trajectory with an apolune of 1 meter and one with an apolune of 100 kilometers.
How would you define the space boundary on these planets?
If the body doesn't have an atmosphere dense enough for its Kármán line to be above the surface, space begins at the surface. What other sensible definition is there?
answered 7 hours ago
Russell Borogove
67.8k2210290
answered 7 hours ago
Russell Borogove
67.8k2210290
answered 7 hours ago
Russell Borogove
67.8k2210290
answered 7 hours ago
Russell Borogove
67.8k2210290
67.8k2210290
1
You may ask for an orbit above lunar hills, mountains and crater walls. An orbit being stable despite mascons.
– Uwe
7 hours ago
6
Stable orbit doesn't have much to do with it; you can't complete an orbit at the Kármán line without boost or lift.
– Russell Borogove
7 hours ago
@Uwe "space" and "orbit" are different things. Russell is right: space begins at the surface of the Moon. That's doesn't mean that you can orbit at the surface, though.
– RonJohn
1 hour ago
add a comment |Â
1
You may ask for an orbit above lunar hills, mountains and crater walls. An orbit being stable despite mascons.
– Uwe
7 hours ago
6
Stable orbit doesn't have much to do with it; you can't complete an orbit at the Kármán line without boost or lift.
– Russell Borogove
7 hours ago
@Uwe "space" and "orbit" are different things. Russell is right: space begins at the surface of the Moon. That's doesn't mean that you can orbit at the surface, though.
– RonJohn
1 hour ago
1
1
You may ask for an orbit above lunar hills, mountains and crater walls. An orbit being stable despite mascons.
– Uwe
7 hours ago
You may ask for an orbit above lunar hills, mountains and crater walls. An orbit being stable despite mascons.
– Uwe
7 hours ago
6
6
Stable orbit doesn't have much to do with it; you can't complete an orbit at the Kármán line without boost or lift.
– Russell Borogove
7 hours ago
Stable orbit doesn't have much to do with it; you can't complete an orbit at the Kármán line without boost or lift.
– Russell Borogove
7 hours ago
@Uwe "space" and "orbit" are different things. Russell is right: space begins at the surface of the Moon. That's doesn't mean that you can orbit at the surface, though.
– RonJohn
1 hour ago
@Uwe "space" and "orbit" are different things. Russell is right: space begins at the surface of the Moon. That's doesn't mean that you can orbit at the surface, though.
– RonJohn
1 hour ago
add a comment |Â
up vote
0
down vote
Where does space begin on planets without atmospheres?
Where the ratio κ=1 for the ion cyclotron and ion collision frequencies - for Earth that is 118 ± 0.3 km.
Source: "Rocketâ€Âbased measurements of ion velocity, neutral wind, and electric field in the collisional transition region of the auroral ionosphere", (April 7 2009), by L. Sangalli, D. J. Knudsen, M. F. Larsen, T. Zhan, R. F. Pfaff and D. Rowland.
See Wikipedia's webpage "Outer Space - Boundary":
"There is no clear boundary between Earth's atmosphere and space, as the density of the atmosphere gradually decreases as the altitude increases. There are several standard boundary designations, ...".
Where there is solid rock there is no outer space.
Where there is the vacuum of space, there is space.
If you had an object a hundred meters in diameter with a large cave you would have space in the cave, you certainly wouldn't have atmosphere, such a small object doesn't have enough gravity to hold enough hydrogen to constitute an atmosphere.
On Earth the Kármán Line is used as the boundary of space, and I believe it is defined as the height where you would have to go faster than orbital speed in order to obtain aerodynamic lift. Therefore planets like Mars and Venus also have Kármán Lines.
Source Wikipedia: "The Kármán line lies at at an altitude of 100 km (62 mi; 330,000 ft) above Earth's sea level and commonly represents the boundary between Earth's atmosphere and outer space. This definition is accepted by the Fédération aéronautique internationale (FAI), which is an international standard-setting and record-keeping body for aeronautics and astronautics.
The line is named after Theodore von Kármán (1881–1963), a Hungarian American engineer and physicist, who was active primarily in aeronautics and astronautics. He was the first person to calculate that the atmosphere around this altitude becomes too thin to support aeronautical flight, since a vehicle at this altitude would have to travel faster than orbital velocity to derive sufficient aerodynamic lift to support itself.".
The line defining the 'edge of space' for Earth at 100 km is convenient, just like international waters are 200 nautical miles from the baseline. Not everyone agrees on it, and it is not scientifically correct; it's agreed upon by treaty.
The line defining the 'edge of space' was determined to be 118 ± 0.3 km.
"Measured ion drifts in the 150–198 km and 92–105 km altitude ranges are consistent with $scriptsizeoverrightarrowE$ × $scriptsizeoverrightarrowB$ motion to within 16 m s$^−1$ rms and with neutral wind velocity to within 20 m s$^−1$, respectively. From these measurements we have calculated the ratio κ of the ion cyclotron and ion collision frequencies, finding κ = 1 at an altitude of 118 ± 0.3 km.
The transition between the two regimes is controlled by the ratio of ion cyclotron to ion collision frequencies, $κ_j = Ω_j/v_j$, where $j$ is a species index. Consequently, collision frequencies can be derived from independent measurements of electric and magnetic fields $scriptsizeoverrightarrowE$ and $scriptsizeoverrightarrowB$, bulk flow velocity $scriptsizeoverrightarrowE$, and neutral winds $scriptsizeoverrightarrowv_j$ [e.g., Egeland et al., 1973].
However, places like Mercury or the Moon have no atmosphere. Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights. How would you define the space boundary on these planets? Should it be defined as the minimum height where it is possible to complete one stable orbit?
This is answered above.
answered 35 mins ago
Rob
1,726221
add a comment |Â
up vote
0
down vote
Where does space begin on planets without atmospheres?
Where the ratio κ=1 for the ion cyclotron and ion collision frequencies - for Earth that is 118 ± 0.3 km.
Source: "Rocketâ€Âbased measurements of ion velocity, neutral wind, and electric field in the collisional transition region of the auroral ionosphere", (April 7 2009), by L. Sangalli, D. J. Knudsen, M. F. Larsen, T. Zhan, R. F. Pfaff and D. Rowland.
See Wikipedia's webpage "Outer Space - Boundary":
"There is no clear boundary between Earth's atmosphere and space, as the density of the atmosphere gradually decreases as the altitude increases. There are several standard boundary designations, ...".
Where there is solid rock there is no outer space.
Where there is the vacuum of space, there is space.
If you had an object a hundred meters in diameter with a large cave you would have space in the cave, you certainly wouldn't have atmosphere, such a small object doesn't have enough gravity to hold enough hydrogen to constitute an atmosphere.
On Earth the Kármán Line is used as the boundary of space, and I believe it is defined as the height where you would have to go faster than orbital speed in order to obtain aerodynamic lift. Therefore planets like Mars and Venus also have Kármán Lines.
Source Wikipedia: "The Kármán line lies at at an altitude of 100 km (62 mi; 330,000 ft) above Earth's sea level and commonly represents the boundary between Earth's atmosphere and outer space. This definition is accepted by the Fédération aéronautique internationale (FAI), which is an international standard-setting and record-keeping body for aeronautics and astronautics.
The line is named after Theodore von Kármán (1881–1963), a Hungarian American engineer and physicist, who was active primarily in aeronautics and astronautics. He was the first person to calculate that the atmosphere around this altitude becomes too thin to support aeronautical flight, since a vehicle at this altitude would have to travel faster than orbital velocity to derive sufficient aerodynamic lift to support itself.".
The line defining the 'edge of space' for Earth at 100 km is convenient, just like international waters are 200 nautical miles from the baseline. Not everyone agrees on it, and it is not scientifically correct; it's agreed upon by treaty.
The line defining the 'edge of space' was determined to be 118 ± 0.3 km.
"Measured ion drifts in the 150–198 km and 92–105 km altitude ranges are consistent with $scriptsizeoverrightarrowE$ × $scriptsizeoverrightarrowB$ motion to within 16 m s$^−1$ rms and with neutral wind velocity to within 20 m s$^−1$, respectively. From these measurements we have calculated the ratio κ of the ion cyclotron and ion collision frequencies, finding κ = 1 at an altitude of 118 ± 0.3 km.
The transition between the two regimes is controlled by the ratio of ion cyclotron to ion collision frequencies, $κ_j = Ω_j/v_j$, where $j$ is a species index. Consequently, collision frequencies can be derived from independent measurements of electric and magnetic fields $scriptsizeoverrightarrowE$ and $scriptsizeoverrightarrowB$, bulk flow velocity $scriptsizeoverrightarrowE$, and neutral winds $scriptsizeoverrightarrowv_j$ [e.g., Egeland et al., 1973].
However, places like Mercury or the Moon have no atmosphere. Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights. How would you define the space boundary on these planets? Should it be defined as the minimum height where it is possible to complete one stable orbit?
This is answered above.
answered 35 mins ago
Rob
1,726221
add a comment |Â
up vote
0
down vote
up vote
0
down vote
Where does space begin on planets without atmospheres?
Where the ratio κ=1 for the ion cyclotron and ion collision frequencies - for Earth that is 118 ± 0.3 km.
Source: "Rocketâ€Âbased measurements of ion velocity, neutral wind, and electric field in the collisional transition region of the auroral ionosphere", (April 7 2009), by L. Sangalli, D. J. Knudsen, M. F. Larsen, T. Zhan, R. F. Pfaff and D. Rowland.
See Wikipedia's webpage "Outer Space - Boundary":
"There is no clear boundary between Earth's atmosphere and space, as the density of the atmosphere gradually decreases as the altitude increases. There are several standard boundary designations, ...".
Where there is solid rock there is no outer space.
Where there is the vacuum of space, there is space.
If you had an object a hundred meters in diameter with a large cave you would have space in the cave, you certainly wouldn't have atmosphere, such a small object doesn't have enough gravity to hold enough hydrogen to constitute an atmosphere.
On Earth the Kármán Line is used as the boundary of space, and I believe it is defined as the height where you would have to go faster than orbital speed in order to obtain aerodynamic lift. Therefore planets like Mars and Venus also have Kármán Lines.
Source Wikipedia: "The Kármán line lies at at an altitude of 100 km (62 mi; 330,000 ft) above Earth's sea level and commonly represents the boundary between Earth's atmosphere and outer space. This definition is accepted by the Fédération aéronautique internationale (FAI), which is an international standard-setting and record-keeping body for aeronautics and astronautics.
The line is named after Theodore von Kármán (1881–1963), a Hungarian American engineer and physicist, who was active primarily in aeronautics and astronautics. He was the first person to calculate that the atmosphere around this altitude becomes too thin to support aeronautical flight, since a vehicle at this altitude would have to travel faster than orbital velocity to derive sufficient aerodynamic lift to support itself.".
The line defining the 'edge of space' for Earth at 100 km is convenient, just like international waters are 200 nautical miles from the baseline. Not everyone agrees on it, and it is not scientifically correct; it's agreed upon by treaty.
The line defining the 'edge of space' was determined to be 118 ± 0.3 km.
"Measured ion drifts in the 150–198 km and 92–105 km altitude ranges are consistent with $scriptsizeoverrightarrowE$ × $scriptsizeoverrightarrowB$ motion to within 16 m s$^−1$ rms and with neutral wind velocity to within 20 m s$^−1$, respectively. From these measurements we have calculated the ratio κ of the ion cyclotron and ion collision frequencies, finding κ = 1 at an altitude of 118 ± 0.3 km.
The transition between the two regimes is controlled by the ratio of ion cyclotron to ion collision frequencies, $κ_j = Ω_j/v_j$, where $j$ is a species index. Consequently, collision frequencies can be derived from independent measurements of electric and magnetic fields $scriptsizeoverrightarrowE$ and $scriptsizeoverrightarrowB$, bulk flow velocity $scriptsizeoverrightarrowE$, and neutral winds $scriptsizeoverrightarrowv_j$ [e.g., Egeland et al., 1973].
However, places like Mercury or the Moon have no atmosphere. Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights. How would you define the space boundary on these planets? Should it be defined as the minimum height where it is possible to complete one stable orbit?
This is answered above.
answered 35 mins ago
Rob
1,726221
Where does space begin on planets without atmospheres?
Where the ratio κ=1 for the ion cyclotron and ion collision frequencies - for Earth that is 118 ± 0.3 km.
Source: "Rocketâ€Âbased measurements of ion velocity, neutral wind, and electric field in the collisional transition region of the auroral ionosphere", (April 7 2009), by L. Sangalli, D. J. Knudsen, M. F. Larsen, T. Zhan, R. F. Pfaff and D. Rowland.
See Wikipedia's webpage "Outer Space - Boundary":
"There is no clear boundary between Earth's atmosphere and space, as the density of the atmosphere gradually decreases as the altitude increases. There are several standard boundary designations, ...".
Where there is solid rock there is no outer space.
Where there is the vacuum of space, there is space.
If you had an object a hundred meters in diameter with a large cave you would have space in the cave, you certainly wouldn't have atmosphere, such a small object doesn't have enough gravity to hold enough hydrogen to constitute an atmosphere.
On Earth the Kármán Line is used as the boundary of space, and I believe it is defined as the height where you would have to go faster than orbital speed in order to obtain aerodynamic lift. Therefore planets like Mars and Venus also have Kármán Lines.
Source Wikipedia: "The Kármán line lies at at an altitude of 100 km (62 mi; 330,000 ft) above Earth's sea level and commonly represents the boundary between Earth's atmosphere and outer space. This definition is accepted by the Fédération aéronautique internationale (FAI), which is an international standard-setting and record-keeping body for aeronautics and astronautics.
The line is named after Theodore von Kármán (1881–1963), a Hungarian American engineer and physicist, who was active primarily in aeronautics and astronautics. He was the first person to calculate that the atmosphere around this altitude becomes too thin to support aeronautical flight, since a vehicle at this altitude would have to travel faster than orbital velocity to derive sufficient aerodynamic lift to support itself.".
The line defining the 'edge of space' for Earth at 100 km is convenient, just like international waters are 200 nautical miles from the baseline. Not everyone agrees on it, and it is not scientifically correct; it's agreed upon by treaty.
The line defining the 'edge of space' was determined to be 118 ± 0.3 km.
"Measured ion drifts in the 150–198 km and 92–105 km altitude ranges are consistent with $scriptsizeoverrightarrowE$ × $scriptsizeoverrightarrowB$ motion to within 16 m s$^−1$ rms and with neutral wind velocity to within 20 m s$^−1$, respectively. From these measurements we have calculated the ratio κ of the ion cyclotron and ion collision frequencies, finding κ = 1 at an altitude of 118 ± 0.3 km.
The transition between the two regimes is controlled by the ratio of ion cyclotron to ion collision frequencies, $κ_j = Ω_j/v_j$, where $j$ is a species index. Consequently, collision frequencies can be derived from independent measurements of electric and magnetic fields $scriptsizeoverrightarrowE$ and $scriptsizeoverrightarrowB$, bulk flow velocity $scriptsizeoverrightarrowE$, and neutral winds $scriptsizeoverrightarrowv_j$ [e.g., Egeland et al., 1973].
However, places like Mercury or the Moon have no atmosphere. Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights. How would you define the space boundary on these planets? Should it be defined as the minimum height where it is possible to complete one stable orbit?
This is answered above.
answered 35 mins ago
Rob
1,726221
answered 35 mins ago
Rob
1,726221
answered 35 mins ago
Rob
1,726221
answered 35 mins ago
Rob
1,726221
1,726221
add a comment |Â
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The lunar minimum height where it is possible to complete one stable orbit depends on lunar mascons.
– Uwe
8 hours ago
@Uwe the phrase "one stable orbit" doesn't even make sense. The idea of "stable" has to do with the ability of a body to orbit many times without significant changes in the orbit. One stable orbit doesn't really mean anything.
– uhoh
5 hours ago