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• ## Re: A transitional step for a space elevator

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• ... I guess I should have been more detailed, they expect to be able to use balloons up to 40 km, then stack on top of the lower floating structure up to 100
Message 1 of 7 , Feb 26, 2012
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--- In space-elevator@yahoogroups.com, "am4987" <am.swallow@...> wrote:
>
> --- In space-elevator@yahoogroups.com, "brooksn" <bhn1700@> wrote:
> >
> > http://en.wikipedia.org/wiki/SpaceShaft
> >
> > http://spaceshaft.org/
> >
> > Has anyone heard of a space shaft? After reading about it, it seems like the perfect transition step. A levitating platform, using balloons, that is vertical, going from near to the ground to 100km above the Earth's surface. This would allow for high altitude launches avoiding the dense lower atmosphere and potentially creating a transition step for a space elevator.
> >
> > Brooks
> >
>
> 100 km is too high for balloons. You may get about 30 km when lifting a heavy object. There is a small saving in fuel but less than you think, it is the air resistance that you are reducing.
>
> LEO is a velocity around the Earth (7.8+ km/s) not a height. The balloons give you a speed of about 0 km/s against the Earth's surface.
>
> Andrew Swallow
> 1 Attached file| 4KB

I guess I should have been more detailed, they expect to be able to use balloons up to 40 km, then 'stack' on top of the lower floating structure up to 100 km.

My understanding is that at 100 km you're pretty much above 99% of the atmosphere giving a large saving in fuel. The referenced example I found below states, "As a rough estimate, a rocket that reaches an altitude of 20 km when launched from the ground will reach 100 km if launched at an altitude of 20 km from a balloon." In other words 4 times the distance with the same fuel, plus the higher distance you started from. Now 20 km is above 90% of the atmosphere, so at 100 km, I assume we are above 99% giving a little more advantage.

http://en.wikipedia.org/wiki/High-altitude_platform

My understanding is that the 'weight' of objects at 100 km and the escape velocity imparted by the Earth's rotation at 100 km are going to be very small advantages. Having looked up the numbers it appears you 'lose' 1.03% of your weight when you launch from 100 km. Quite small but not totally inconsequential.

Now the Earth's rotation at the equator imparts 0.46 km/s escape velocity, but going up to 100 km does not seem to impart very much more. According to what I found below, at 30 km up you reduce the escape velocity by 0.2% vs. the surface. At 100 km, you reduce the escape velocity even further, v = sqrt (2*G*M/r), so who knows ~0.4% reduction escape velocity?

Regardless it appears that a high altitude, 100 km launch or even a 30 km launch would remove large atmospheric drag Earth has at the surface plus 1% of the weight to launch and maybe ~0.4% of the escape velocity. Seems like something very much worth looking into, plus it can always be a stepping stone to a space elevator while being useful now and not after completion.
Brooks
• ... Now look to see what is happening to the balloon size at various heights. Andrew Swallow
Message 1 of 7 , Feb 27, 2012
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--- In space-elevator@yahoogroups.com, "brooksn" <bhn1700@...> wrote:
>
> --- In space-elevator@yahoogroups.com, "am4987" <am.swallow@> wrote:
> >
> > --- In space-elevator@yahoogroups.com, "brooksn" <bhn1700@> wrote:
> > >
> > > http://en.wikipedia.org/wiki/SpaceShaft
> > >
> > > http://spaceshaft.org/
> > >
> > > Has anyone heard of a space shaft? After reading about it, it seems like the perfect transition step. A levitating platform, using balloons, that is vertical, going from near to the ground to 100km above the Earth's surface. This would allow for high altitude launches avoiding the dense lower atmosphere and potentially creating a transition step for a space elevator.
> > >
> > > Brooks
> > >
> >
> > 100 km is too high for balloons. You may get about 30 km when lifting a heavy object. There is a small saving in fuel but less than you think, it is the air resistance that you are reducing.
> >
> > LEO is a velocity around the Earth (7.8+ km/s) not a height. The balloons give you a speed of about 0 km/s against the Earth's surface.
> >
> > Andrew Swallow
> > 1 Attached file| 4KB
>
> I guess I should have been more detailed, they expect to be able to use balloons up to 40 km, then 'stack' on top of the lower floating structure up to 100 km.
>
> My understanding is that at 100 km you're pretty much above 99% of the atmosphere giving a large saving in fuel. The referenced example I found below states, "As a rough estimate, a rocket that reaches an altitude of 20 km when launched from the ground will reach 100 km if launched at an altitude of 20 km from a balloon." In other words 4 times the distance with the same fuel, plus the higher distance you started from. Now 20 km is above 90% of the atmosphere, so at 100 km, I assume we are above 99% giving a little more advantage.
>
> http://en.wikipedia.org/wiki/High-altitude_platform
>
> My understanding is that the 'weight' of objects at 100 km and the escape velocity imparted by the Earth's rotation at 100 km are going to be very small advantages. Having looked up the numbers it appears you 'lose' 1.03% of your weight when you launch from 100 km. Quite small but not totally inconsequential.
>
> Now the Earth's rotation at the equator imparts 0.46 km/s escape velocity, but going up to 100 km does not seem to impart very much more. According to what I found below, at 30 km up you reduce the escape velocity by 0.2% vs. the surface. At 100 km, you reduce the escape velocity even further, v = sqrt (2*G*M/r), so who knows ~0.4% reduction escape velocity?
>
>
> Regardless it appears that a high altitude, 100 km launch or even a 30 km launch would remove large atmospheric drag Earth has at the surface plus 1% of the weight to launch and maybe ~0.4% of the escape velocity. Seems like something very much worth looking into, plus it can always be a stepping stone to a space elevator while being useful now and not after completion.
> Brooks
>

Now look to see what is happening to the balloon size at various heights.

Andrew Swallow
• All of our modern rockets take heavy advantage of ground support prior to launch. Topping off fuel, providing power, etc. this system will likely lose all
Message 1 of 7 , Feb 27, 2012
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All of our modern rockets take heavy advantage of ground support prior to launch.
Topping off fuel, providing power, etc. this system will likely lose all that, unless we float it as well.
Then there is the prospect of putting a fully fueled rocket out of reach during the balloon ascent. If something, anything goes wrong, how do we abort this potential bomb back to ground?
Fun thought experiment, but I just can't see it happening.
Also a bit of a mischaracterization as a stepping stone to an elevator. This is more of a rocket launch variant, sort of like Sealaunch, that does lead to much useful elevator tech.

--- In space-elevator@yahoogroups.com, "am4987" <am.swallow@...> wrote:
>
>
>
> --- In space-elevator@yahoogroups.com, "brooksn" <bhn1700@> wrote:
> >
> > --- In space-elevator@yahoogroups.com, "am4987" <am.swallow@> wrote:
> > >
> > > --- In space-elevator@yahoogroups.com, "brooksn" <bhn1700@> wrote:
> > > >
> > > > http://en.wikipedia.org/wiki/SpaceShaft
> > > >
> > > > http://spaceshaft.org/
> > > >
> > > > Has anyone heard of a space shaft? After reading about it, it seems like the perfect transition step. A levitating platform, using balloons, that is vertical, going from near to the ground to 100km above the Earth's surface. This would allow for high altitude launches avoiding the dense lower atmosphere and potentially creating a transition step for a space elevator.
> > > >
> > > > Brooks
> > > >
> > >
> > > 100 km is too high for balloons. You may get about 30 km when lifting a heavy object. There is a small saving in fuel but less than you think, it is the air resistance that you are reducing.
> > >
> > > LEO is a velocity around the Earth (7.8+ km/s) not a height. The balloons give you a speed of about 0 km/s against the Earth's surface.
> > >
> > > Andrew Swallow
> > > 1 Attached file| 4KB
> >
> > I guess I should have been more detailed, they expect to be able to use balloons up to 40 km, then 'stack' on top of the lower floating structure up to 100 km.
> >
> > My understanding is that at 100 km you're pretty much above 99% of the atmosphere giving a large saving in fuel. The referenced example I found below states, "As a rough estimate, a rocket that reaches an altitude of 20 km when launched from the ground will reach 100 km if launched at an altitude of 20 km from a balloon." In other words 4 times the distance with the same fuel, plus the higher distance you started from. Now 20 km is above 90% of the atmosphere, so at 100 km, I assume we are above 99% giving a little more advantage.
> >
> > http://en.wikipedia.org/wiki/High-altitude_platform
> >
> > My understanding is that the 'weight' of objects at 100 km and the escape velocity imparted by the Earth's rotation at 100 km are going to be very small advantages. Having looked up the numbers it appears you 'lose' 1.03% of your weight when you launch from 100 km. Quite small but not totally inconsequential.
> >
> > Now the Earth's rotation at the equator imparts 0.46 km/s escape velocity, but going up to 100 km does not seem to impart very much more. According to what I found below, at 30 km up you reduce the escape velocity by 0.2% vs. the surface. At 100 km, you reduce the escape velocity even further, v = sqrt (2*G*M/r), so who knows ~0.4% reduction escape velocity?
> >
> >
> > Regardless it appears that a high altitude, 100 km launch or even a 30 km launch would remove large atmospheric drag Earth has at the surface plus 1% of the weight to launch and maybe ~0.4% of the escape velocity. Seems like something very much worth looking into, plus it can always be a stepping stone to a space elevator while being useful now and not after completion.
> > Brooks
> >
>
> Now look to see what is happening to the balloon size at various heights.
>
> Andrew Swallow
>
• It will increase in size due to increased altitude due to reduced to the pressure. Which is accounted for in current high altitude balloon use and will need
Message 1 of 7 , Feb 28, 2012
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It will increase in size due to increased altitude due to reduced to the pressure. Which is accounted for in current high altitude balloon use and will need to be accounted for in any future high altitude balloon use.
Brooks

> Now look to see what is happening to the balloon size at various heights.
>
> Andrew Swallow
• Why would this system lose all the ground support provides? Every system from the ground can be moved to the upper platform. Plus there have been many non
Message 1 of 7 , Feb 28, 2012
View Source
Why would this system lose all the ground support provides? Every system from the ground can be moved to the upper platform. Plus there have been many non ground supported launches already, first the air force has launched countless balloon based rockets (agreed not the largest rockets we want to use but the experience is there), second the Pegasus is a rocket which launches from a 747 and is still an active program with about 40 launches under its built with very little 'ground support' from the 747, and lastly every multistage rocket (except the first stage) is essentially without ground support
after launch.

An aborting a mission, I don't see why the shutdowns done on the ground couldn't be done during an ascent.

I would consider a space elevator to be far more of a thought experiment then a floating launch tower. Considering that materials and hazards make a space elevator a far taller order, literally and figuratively.

I'm not sure I follow why this wouldn't be a stepping stone, literally you're a 100 km further up from Earth to link with any future attempt to string down an elevator from a GEO. And best of all its useful today, not when the GEO tether finally reaches the ground.

Brooks

> All of our modern rockets take heavy advantage of ground support prior to launch.
> Topping off fuel, providing power, etc. this system will likely lose all that, unless we float it as well.
> Then there is the prospect of putting a fully fueled rocket out of reach during the balloon ascent. If something, anything goes wrong, how do we abort this potential bomb back to ground?
> Fun thought experiment, but I just can't see it happening.
> Also a bit of a mischaracterization as a stepping stone to an elevator. This is more of a rocket launch variant, sort of like Sealaunch, that does lead to much useful elevator tech.
>
> --- In space-elevator@yahoogroups.com, "am4987" <am.swallow@> wrote:
> >
> >
> >
> > --- In space-elevator@yahoogroups.com, "brooksn" <bhn1700@> wrote:
> > >
> > > --- In space-elevator@yahoogroups.com, "am4987" <am.swallow@> wrote:
> > > >
> > > > --- In space-elevator@yahoogroups.com, "brooksn" <bhn1700@> wrote:
> > > > >
> > > > > http://en.wikipedia.org/wiki/SpaceShaft
> > > > >
> > > > > http://spaceshaft.org/
> > > > >
> > > > > Has anyone heard of a space shaft? After reading about it, it seems like the perfect transition step. A levitating platform, using balloons, that is vertical, going from near to the ground to 100km above the Earth's surface. This would allow for high altitude launches avoiding the dense lower atmosphere and potentially creating a transition step for a space elevator.
> > > > >
> > > > > Brooks
> > > > >
> > > >
> > > > 100 km is too high for balloons. You may get about 30 km when lifting a heavy object. There is a small saving in fuel but less than you think, it is the air resistance that you are reducing.
> > > >
> > > > LEO is a velocity around the Earth (7.8+ km/s) not a height. The balloons give you a speed of about 0 km/s against the Earth's surface.
> > > >
> > > > Andrew Swallow
> > > > 1 Attached file| 4KB
> > >
> > > I guess I should have been more detailed, they expect to be able to use balloons up to 40 km, then 'stack' on top of the lower floating structure up to 100 km.
> > >
> > > My understanding is that at 100 km you're pretty much above 99% of the atmosphere giving a large saving in fuel. The referenced example I found below states, "As a rough estimate, a rocket that reaches an altitude of 20 km when launched from the ground will reach 100 km if launched at an altitude of 20 km from a balloon." In other words 4 times the distance with the same fuel, plus the higher distance you started from. Now 20 km is above 90% of the atmosphere, so at 100 km, I assume we are above 99% giving a little more advantage.
> > >
> > > http://en.wikipedia.org/wiki/High-altitude_platform
> > >
> > > My understanding is that the 'weight' of objects at 100 km and the escape velocity imparted by the Earth's rotation at 100 km are going to be very small advantages. Having looked up the numbers it appears you 'lose' 1.03% of your weight when you launch from 100 km. Quite small but not totally inconsequential.
> > >
> > > Now the Earth's rotation at the equator imparts 0.46 km/s escape velocity, but going up to 100 km does not seem to impart very much more. According to what I found below, at 30 km up you reduce the escape velocity by 0.2% vs. the surface. At 100 km, you reduce the escape velocity even further, v = sqrt (2*G*M/r), so who knows ~0.4% reduction escape velocity?
> > >
> > >
> > > Regardless it appears that a high altitude, 100 km launch or even a 30 km launch would remove large atmospheric drag Earth has at the surface plus 1% of the weight to launch and maybe ~0.4% of the escape velocity. Seems like something very much worth looking into, plus it can always be a stepping stone to a space elevator while being useful now and not after completion.
> > > Brooks
> > >
> >
> > Now look to see what is happening to the balloon size at various heights.
> >
> > Andrew Swallow
> >
>
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