Latest On Space Elevators and Power Beaming

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tonybarry
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Post by tonybarry »

Hello tombo,
Your slingshot idea was used by (among others) missionaries in Ecuador in the 1950s (read about Jim Elliott, "Through gates of splendour").
They found that the tethered object moved to the centre of the circle of turn, and became almost motionless while the plane orbited around it. The missionaries used this method to lower buckets of supplies to their friends where there was no landing strip.

Regards,
Tony Barry

JoeStrout
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Post by JoeStrout »

Mike Holmes wrote:But a possibly better candidate would be Mt. Chimborazo in Ecuador. Relatively low above sea level, it lies very near the equator. Since the Earth is not a sphere, but oblate, that means that, in fact, Chimborazo is two kilometers farther from the center of the Earth at it's top.

Now, the atmosphere is still as thick there, so that still has to be countered. But I wonder if the distance from the center of mass of the planet is, in fact, what's being countered with high elevation launches?
No, it's all about the air density. The difference in gravity (due to a couple miles' difference from the center of the Earth) would be quite insignificant.

Best,
- Joe
Joe Strout
Talk-Polywell.org site administrator

Mike Holmes
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Post by Mike Holmes »

I wasn't supposing that gravity would be significantly different, simply that you might be closer to orbit. Less distance to go, basically. Potential energy due to having driven the vehicle up to elevation, essentially. That's elevation you don't have to counter with reaction mass in the vehicle.

Also Tony may have hit on what might be the real advantage of the equator, the rotational velocity advantage.

Mike

Aero
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Post by Aero »

Yes, confirmed that the advantage of the equator derives from the direction and rate of rotation of the Earth. Orbital velocity is about 17,000 mph around the center of mass. Earth's rotation causes the launch vehicle to be traveling about 1000 mph eastward around the center of mass, as it sits on the surface. Consequently, the satellite need only be accelerated 16,000 mph to reach orbital velocity. Of course there is a 2000 mph penalty if you want to launch westerly, so they don't do that. And the Earth's rotation rate is no help for polar orbits.
Aero

StevePoling
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Post by StevePoling »

tonybarry wrote:Hello tombo,
Your slingshot idea was used by (among others) missionaries in Ecuador in the 1950s (read about Jim Elliott, "Through gates of splendour").
They found that the tethered object moved to the centre of the circle of turn, and became almost motionless while the plane orbited around it. The missionaries used this method to lower buckets of supplies to their friends where there was no landing strip.
I remember being amazed as a kid seeing a picture of this in National Geographic. If it wasn't a Cessna that demonstrated this concept, it was something pretty darned close.

JohnSmith
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Post by JohnSmith »

While I'm slightly in awe of the launch loop concept, and am hoping against hope that we manage at least one megascale engineering project before I die, I'm a bit enamored with the ram accelerator.

http://www.tbfg.org/

Ignoring their terrible front page graphic, I hope that they manage to build a demo. Heck, it'll cost about what WB-7 did!

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