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To the Sun

Old 13th Aug 2018, 11:17
  #21 (permalink)  
 
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Originally Posted by ORAC View Post
Response to you - just because chemical energy alone wouldn’t get them out of the gravity well doesn’t mean they’d be trapped. [email protected]/microwave pulsed systems would be able to do it - especially those initially using systems to detonate atmosphere in a bowl cavity on the bottom of a vehicle before shifting to injecting fuel.
Detonating the atmosphere doesn't sound like a good way to launch things and then it comes to injecting fuel. I'll also add that if this is a good way to launch vehicles into space why hasn't it been tried?
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Old 13th Aug 2018, 12:22
  #22 (permalink)  
 
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It has been tried, at least on a small scale..

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Old 13th Aug 2018, 19:15
  #23 (permalink)  
 
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Originally Posted by Hokulea View Post
ORAC - not sure if you saw this, but it's to do with the Fermi Paradox, i.e., why hasn't the Galaxy been colonized by aliens? One reason might be that chemical propulsion might not even get a civilisation into space if all they use is chemical propulsion just like us. As you point out, rockets are inefficient and severely restrict what we can do but we're lucky enough living on Earth that chemical energy can still provide enough energy to go to the moon or Mars.
For the vast majority of the galaxy, the only difficult part is getting into space. Once you're there, travel is easy, so long as you don't care how long it takes.

And even getting into space doesn't need to be that difficult. It's theoretically possible to lift an aircraft from the Earth's atmosphere and deposit it on Mars without expending any fuel, using multiple tethers. Of course, you need to get the first tether into space somehow, and the engineering problems of ensuring you hit all the tethers along the way at the right spot and right time will be... exciting. One screwup, and you fly off into deep space, possibly even out of the solar system altogether.
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Old 13th Aug 2018, 19:21
  #24 (permalink)  
 
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Originally Posted by Hokulea View Post
I'll also add that if this is a good way to launch vehicles into space why hasn't it been tried?
Because there's been no real demand for innovation in spaceflight for most of the last fifty years. Also, perhaps, because it could be a good way to launch low-cost ICBMs that would be difficult to spot, and no-one wants to give the bad guys any ideas.
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Old 13th Aug 2018, 19:53
  #25 (permalink)  
 
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Arthur C Clarke wrote a good book called The Towers of Taprobane (or words to that effect) using towers of a moderate height (23,000 miles I think) to launch vehicles from the top with no fuel needed.
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Old 13th Aug 2018, 20:09
  #26 (permalink)  
 
Join Date: Jun 2009
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Fountains Of Paradise, I think?

The problem with a space elevator, as I understand it, is that you can't build it from the surface to space, you have to build it from space to the surface. Which is OK if you're already able to get into space, but not if your planet is so big that chemical fuels make reaching space very difficult, or impossible.

Though there's still the Orion option. There won't be many habitable planets so large that a few nuclear bombs won't be able to push you into orbit.

Edit: that said, if your planet is borderline for launch from the surface with chemical rockets, launch from a very tall tower might well still be viable. It would eliminate most of the drag from the atmosphere, and allow you to use vacuum-rated engines, which are more fuel-efficient than those which have to operate at sea-level.

It would probably have to be 80-100,000 feet tall, though.
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