How can a rocket approaching the Karman Line then return to earth faster than 53 m/s terminal velocity?











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In the book, How to Make a Spaceship: A Band of Renegades, an Epic Race and the Birth of Private Spaceflight the opening chapter details the June 2004 attempt to take SpaceShipOne to the Karman Line.



The chapter also recounts a story of the X-15, piloted by Mike Adams in 1967, re-entering the earth's atmosphere at Mach 5 and breaking up in a violent spin. This is used as a warning to the reader about the dangers that Melvill is facing in SpaceShipOne.



How does a vehicle, having exhausted it's primary thrust, return to earth at a greater speed than terminal velocity?










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    In the book, How to Make a Spaceship: A Band of Renegades, an Epic Race and the Birth of Private Spaceflight the opening chapter details the June 2004 attempt to take SpaceShipOne to the Karman Line.



    The chapter also recounts a story of the X-15, piloted by Mike Adams in 1967, re-entering the earth's atmosphere at Mach 5 and breaking up in a violent spin. This is used as a warning to the reader about the dangers that Melvill is facing in SpaceShipOne.



    How does a vehicle, having exhausted it's primary thrust, return to earth at a greater speed than terminal velocity?










    share|improve this question
























      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      In the book, How to Make a Spaceship: A Band of Renegades, an Epic Race and the Birth of Private Spaceflight the opening chapter details the June 2004 attempt to take SpaceShipOne to the Karman Line.



      The chapter also recounts a story of the X-15, piloted by Mike Adams in 1967, re-entering the earth's atmosphere at Mach 5 and breaking up in a violent spin. This is used as a warning to the reader about the dangers that Melvill is facing in SpaceShipOne.



      How does a vehicle, having exhausted it's primary thrust, return to earth at a greater speed than terminal velocity?










      share|improve this question













      In the book, How to Make a Spaceship: A Band of Renegades, an Epic Race and the Birth of Private Spaceflight the opening chapter details the June 2004 attempt to take SpaceShipOne to the Karman Line.



      The chapter also recounts a story of the X-15, piloted by Mike Adams in 1967, re-entering the earth's atmosphere at Mach 5 and breaking up in a violent spin. This is used as a warning to the reader about the dangers that Melvill is facing in SpaceShipOne.



      How does a vehicle, having exhausted it's primary thrust, return to earth at a greater speed than terminal velocity?







      rockets gravity thrust






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      asked 1 hour ago









      Venture2099

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          53 m/s is the approximate terminal velocity of a human skydiver.



          The terminal velocity of a 7-ton metal dart is quite a bit higher. Larger objects tend to be affected less by atmospheric drag than smaller ones, all other things being equal. Terminal velocity also increases with altitude because the air is thinner.



          Assuming 7000 kg mass, 3.5 m2 cross section, and coefficient of drag 0.3 (educated guesses for the X-15), this online terminal velocity calculator gives 295 m/s terminal velocity at sea level (about 0.9 mach). At 25km altitude (air density 0.04), terminal velocity is about 1800 m/s or mach 5.






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          • I thought all things had the same terminal velocity. If we drop a book and a cannonball from a great height they land at the same time no?
            – Venture2099
            1 hour ago






          • 2




            @Venture2099 Not in atmosphere, no (do a feather and a cannonball land at the same time?). The retarding force from air resistance is proportional to cross-sectional area; the relative acceleration imparted by that force is inversely proportional to mass. For spheres of identical density, for example, cross sectional area goes up by the square of radius; mass goes up by the cube of radius, so drag-acceleration is inversely proportional to radius.
            – Russell Borogove
            1 hour ago












          • @Venture2099 The reason a demonstration with two metal balls from not too great a height can work is just that the effect of air resistance will be negligible for fairly massive objects at fairly low velocities.
            – Mark Foskey
            55 mins ago











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          53 m/s is the approximate terminal velocity of a human skydiver.



          The terminal velocity of a 7-ton metal dart is quite a bit higher. Larger objects tend to be affected less by atmospheric drag than smaller ones, all other things being equal. Terminal velocity also increases with altitude because the air is thinner.



          Assuming 7000 kg mass, 3.5 m2 cross section, and coefficient of drag 0.3 (educated guesses for the X-15), this online terminal velocity calculator gives 295 m/s terminal velocity at sea level (about 0.9 mach). At 25km altitude (air density 0.04), terminal velocity is about 1800 m/s or mach 5.






          share|improve this answer























          • I thought all things had the same terminal velocity. If we drop a book and a cannonball from a great height they land at the same time no?
            – Venture2099
            1 hour ago






          • 2




            @Venture2099 Not in atmosphere, no (do a feather and a cannonball land at the same time?). The retarding force from air resistance is proportional to cross-sectional area; the relative acceleration imparted by that force is inversely proportional to mass. For spheres of identical density, for example, cross sectional area goes up by the square of radius; mass goes up by the cube of radius, so drag-acceleration is inversely proportional to radius.
            – Russell Borogove
            1 hour ago












          • @Venture2099 The reason a demonstration with two metal balls from not too great a height can work is just that the effect of air resistance will be negligible for fairly massive objects at fairly low velocities.
            – Mark Foskey
            55 mins ago















          up vote
          4
          down vote













          53 m/s is the approximate terminal velocity of a human skydiver.



          The terminal velocity of a 7-ton metal dart is quite a bit higher. Larger objects tend to be affected less by atmospheric drag than smaller ones, all other things being equal. Terminal velocity also increases with altitude because the air is thinner.



          Assuming 7000 kg mass, 3.5 m2 cross section, and coefficient of drag 0.3 (educated guesses for the X-15), this online terminal velocity calculator gives 295 m/s terminal velocity at sea level (about 0.9 mach). At 25km altitude (air density 0.04), terminal velocity is about 1800 m/s or mach 5.






          share|improve this answer























          • I thought all things had the same terminal velocity. If we drop a book and a cannonball from a great height they land at the same time no?
            – Venture2099
            1 hour ago






          • 2




            @Venture2099 Not in atmosphere, no (do a feather and a cannonball land at the same time?). The retarding force from air resistance is proportional to cross-sectional area; the relative acceleration imparted by that force is inversely proportional to mass. For spheres of identical density, for example, cross sectional area goes up by the square of radius; mass goes up by the cube of radius, so drag-acceleration is inversely proportional to radius.
            – Russell Borogove
            1 hour ago












          • @Venture2099 The reason a demonstration with two metal balls from not too great a height can work is just that the effect of air resistance will be negligible for fairly massive objects at fairly low velocities.
            – Mark Foskey
            55 mins ago













          up vote
          4
          down vote










          up vote
          4
          down vote









          53 m/s is the approximate terminal velocity of a human skydiver.



          The terminal velocity of a 7-ton metal dart is quite a bit higher. Larger objects tend to be affected less by atmospheric drag than smaller ones, all other things being equal. Terminal velocity also increases with altitude because the air is thinner.



          Assuming 7000 kg mass, 3.5 m2 cross section, and coefficient of drag 0.3 (educated guesses for the X-15), this online terminal velocity calculator gives 295 m/s terminal velocity at sea level (about 0.9 mach). At 25km altitude (air density 0.04), terminal velocity is about 1800 m/s or mach 5.






          share|improve this answer














          53 m/s is the approximate terminal velocity of a human skydiver.



          The terminal velocity of a 7-ton metal dart is quite a bit higher. Larger objects tend to be affected less by atmospheric drag than smaller ones, all other things being equal. Terminal velocity also increases with altitude because the air is thinner.



          Assuming 7000 kg mass, 3.5 m2 cross section, and coefficient of drag 0.3 (educated guesses for the X-15), this online terminal velocity calculator gives 295 m/s terminal velocity at sea level (about 0.9 mach). At 25km altitude (air density 0.04), terminal velocity is about 1800 m/s or mach 5.







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited 1 hour ago

























          answered 1 hour ago









          Russell Borogove

          77.3k2248335




          77.3k2248335












          • I thought all things had the same terminal velocity. If we drop a book and a cannonball from a great height they land at the same time no?
            – Venture2099
            1 hour ago






          • 2




            @Venture2099 Not in atmosphere, no (do a feather and a cannonball land at the same time?). The retarding force from air resistance is proportional to cross-sectional area; the relative acceleration imparted by that force is inversely proportional to mass. For spheres of identical density, for example, cross sectional area goes up by the square of radius; mass goes up by the cube of radius, so drag-acceleration is inversely proportional to radius.
            – Russell Borogove
            1 hour ago












          • @Venture2099 The reason a demonstration with two metal balls from not too great a height can work is just that the effect of air resistance will be negligible for fairly massive objects at fairly low velocities.
            – Mark Foskey
            55 mins ago


















          • I thought all things had the same terminal velocity. If we drop a book and a cannonball from a great height they land at the same time no?
            – Venture2099
            1 hour ago






          • 2




            @Venture2099 Not in atmosphere, no (do a feather and a cannonball land at the same time?). The retarding force from air resistance is proportional to cross-sectional area; the relative acceleration imparted by that force is inversely proportional to mass. For spheres of identical density, for example, cross sectional area goes up by the square of radius; mass goes up by the cube of radius, so drag-acceleration is inversely proportional to radius.
            – Russell Borogove
            1 hour ago












          • @Venture2099 The reason a demonstration with two metal balls from not too great a height can work is just that the effect of air resistance will be negligible for fairly massive objects at fairly low velocities.
            – Mark Foskey
            55 mins ago
















          I thought all things had the same terminal velocity. If we drop a book and a cannonball from a great height they land at the same time no?
          – Venture2099
          1 hour ago




          I thought all things had the same terminal velocity. If we drop a book and a cannonball from a great height they land at the same time no?
          – Venture2099
          1 hour ago




          2




          2




          @Venture2099 Not in atmosphere, no (do a feather and a cannonball land at the same time?). The retarding force from air resistance is proportional to cross-sectional area; the relative acceleration imparted by that force is inversely proportional to mass. For spheres of identical density, for example, cross sectional area goes up by the square of radius; mass goes up by the cube of radius, so drag-acceleration is inversely proportional to radius.
          – Russell Borogove
          1 hour ago






          @Venture2099 Not in atmosphere, no (do a feather and a cannonball land at the same time?). The retarding force from air resistance is proportional to cross-sectional area; the relative acceleration imparted by that force is inversely proportional to mass. For spheres of identical density, for example, cross sectional area goes up by the square of radius; mass goes up by the cube of radius, so drag-acceleration is inversely proportional to radius.
          – Russell Borogove
          1 hour ago














          @Venture2099 The reason a demonstration with two metal balls from not too great a height can work is just that the effect of air resistance will be negligible for fairly massive objects at fairly low velocities.
          – Mark Foskey
          55 mins ago




          @Venture2099 The reason a demonstration with two metal balls from not too great a height can work is just that the effect of air resistance will be negligible for fairly massive objects at fairly low velocities.
          – Mark Foskey
          55 mins ago


















           

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