Outward Bound: Beyond Low Earth Orbit

Once a combination launch system that includes a Skyhook has been built and orbiting hotels and factories are in the process of being built, where do we go next?  Low Earth orbit is only two hundred to three hundred miles up, and some astronauts have described low Earth orbit spaceflight as “skimming the cloud tops.”  By comparison, the Moon is 240,000 miles away and Mars is measured in many millions of miles.  Based on this, low Earth orbit is the equivalent of standing on our doorstep.

So again, where do we go next in our outward bound journey?

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Some people want to return to the Moon to mine it for water, oxygen, minerals, helium 3, and as practice before going to Mars.

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Some people want to explore the near-Earth asteroids with the idea of either mining them or moving them closer to the Earth where they could be processed.

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Others want to build an outpost space station near the Moon that would serve as a jumping off point for trips to the Moon, the near-Earth asteroids, and eventually to Mars.

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Some people want to go directly to Mars,

and some want to build space colonies and satellite solar power stations.

The one thing that all of these ideas have in common is the need to go from low Earth orbit velocity to escape velocity.  It takes a lot of change in velocity to do that.  Change in velocity that requires an upper stage and a lot of propellant.  Building an upper stage, filling it with propellant and lifting it into low Earth orbit costs a lot of money even when using a combination launch system.  Even if you make the upper stage reusable you would still have to launch another load of propellant to refill it and use it again, and the propellant would still have to be contained in tanks.  Bottom line, making the upper stage reusable doesn’t save you very much.  So how do we make going from low Earth orbit to escape velocity as affordable as going from the surface of the Earth to orbit on a combination launch system?

The answer to this is the Skyhook that was built for the combination launch system.

In the same way that the lower end of the Skyhook cable is moving at less than orbital velocity for its altitude, the upper end of the Skyhook cable is moving faster than orbital velocity for its altitude.  Once the Skyhook is long enough, the upper end of the skyhook cable will be moving at escape velocity.  That means that a spacecraft that releases from the upper end of the skyhook cable can be placed on a free return orbit to the Moon, on a path to an outpost space station at L-2, or on an escape trajectory to a near-Earth asteroid without the need to use an upper stage or any of its onboard propellant.  In other words, the upper end of the Skyhook will make low Earth orbit to escape velocity spaceflight affordable to everyone.

Once we have this we won’t need to choose between the Moon, Mars, or the asteroids as we will be able to afford all of them all on a commercial basis as profit making ventures.

 

Index of Articles

  1. Opening the High Frontier
  2. Skyhook, a Journey to Orbit and Beyond
  3. In the Beginning . . .
  4. Why do Rockets Cost so Much?
  5. Combination Launch Systems
  6. It’s All About Speed!
  7. Visions of the Future
  8. The Call of an Unlimited Future
  9. Combination Launch Systems, part 2
  10. Outward Bound: Beyond Low Earth Orbit
  11. and someday . . . Starships!
  12. Mars: how to get there
  13. Outpost Space Stations
  14. Dreams of Space
  15. The Moon or Mars?
  16. Skyhooks and Space Elevators
  17. Stratolaunch and the X-15

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