How fast do we have to go if Earth had no atmosphere?

  • Thread starter 1832vin
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  • #1
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how fast do we have to go if earth had no atmosphere?
i'm wondering why don't they send a small, but extremely fast projectile in front of the rocket, which heats and expands the air in front which reduces most of the friction? (maybe like a railgun?)
does that not reduce the cost?

or am i being really stupid?
 

Answers and Replies

  • #2
Drakkith
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First, the projectile would be much too quick for the rocket! The rocket starts off at a standstill and only reaches a maximum acceleration of a few g's. This means it takes several minutes for it to reach orbital velocity, while a projectile would be at maximum speed the moment it leaves the barrel.

There are other issues too. In general it just wouldn't work.
 
  • #3
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because of conservation of energy, the energy you use for rising a rocket into the space is the same as the method you mentioned. Basically the idea is that, you still need same work done to push away those air molecules.
 
  • #4
The principle you suggest is used on new ships when compressed air is injected all around the vessel for air bubble lubrication. This reduces the drag substantially.

The problem with a rocket as i understand would be that air as a medium is already very light. "Heating" the air away sounds inefficient to me
 
  • #5
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Terminal velocity = 176 ft/sec. Use that to figure out the drag on the moving object, but that drag would be what you would need to generate to maintain a constant velocity with no acceleration.
 
  • #6
Drakkith
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Terminal velocity = 176 ft/sec. Use that to figure out the drag on the moving object, but that drag would be what you would need to generate to maintain a constant velocity with no acceleration.
Why would you want to maintain zero acceleration?
 
  • #7
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energy conservation
 

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