Another Space Elevator Design

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choff
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Another Space Elevator Design

Postby choff » Mon Aug 17, 2015 7:20 pm

This one sounds more realistic than the others, well, slightly anyway.


http://www.telegraph.co.uk/news/science ... tists.html
CHoff

AcesHigh
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Re: Another Space Elevator Design

Postby AcesHigh » Mon Aug 17, 2015 9:17 pm

Why exactly would they save so much fuel just because they are leaving from Stratosphere?

They would STILL Need to reach a delta-v of 28 thousand kilometer per hours, which is really what consumes most fuel on a rocket.

Negating atmospheric drag is a small part of that, as a normal rocket reaches 20km high quite fast, and most fuel spent to that altitude went to build orbital speed, not to fight atmospheric drag.



btw, Sketchup can make nice renders with a nice renderer, but nothing more unprofessional than images taken DIRECTLY from Sketchup, without any rendering.

JoeP
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Re: Another Space Elevator Design

Postby JoeP » Mon Aug 17, 2015 9:25 pm

I'm not seeing the advantages so much when compared to a balloon launch system or even a high altitude carrier jet platform. Wind would be a devil to deal with. Think of the shear forces. It is lighter than air. Hurricanes? I'd rather launch a space plane from the top of a nice flat semi-rigid airship than use this thing. Much cheaper too.

When compared to a real space elevator, you have the counterweight in orbit, which can maintain position via thrusters. And it is secured at both ends and has a lot more mass outside the atmosphere, thus limiting the influence of shear.

I haven't studies it in depth, but it just doesn't seem worth it (at first glance). I don't think the patent covers the materials it is made from either. I assume future carbon composites or some such.
Last edited by JoeP on Mon Aug 17, 2015 9:54 pm, edited 1 time in total.

Skipjack
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Re: Another Space Elevator Design

Postby Skipjack » Mon Aug 17, 2015 9:36 pm

I don't see much of an advantage as well. Main things you safe are drag losses and gravity losses. You might be able to use engines that are more optimized for a vacuum. But that's about it.
I don't think it is worth the effort.

AcesHigh
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Re: Another Space Elevator Design

Postby AcesHigh » Mon Aug 17, 2015 9:45 pm

Skipjack wrote:I don't see much of an advantage as well. Main things you safe are drag losses and gravity losses. You might be able to use engines that are more optimized for a vacuum. But that's about it.
I don't think it is worth the effort.


what gravity losses?

as for engine optimization, we are talking here about a huge engineering task... a much smaller engineering task would be to develop rockets using aerospikes engines, which I guess would negate the advantages of using engines only for vacuum, but having to build a 30 km tall tower.

Skipjack
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Re: Another Space Elevator Design

Postby Skipjack » Mon Aug 17, 2015 10:22 pm

AcesHigh wrote:what gravity losses?

Because you can focus on accelerating horizontally and need to spend less energy on getting to altitude, fighting gravity.

AcesHigh
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Re: Another Space Elevator Design

Postby AcesHigh » Mon Aug 17, 2015 10:26 pm

Skipjack wrote:
AcesHigh wrote:what gravity losses?

Because you can focus on accelerating horizontally and need to spend less energy on getting to altitude, fighting gravity.


the tower is what, 20-30 km tall? You would still need to get 300 km higher for a decent dragless orbit. The gains would be marginal, after all, it would still need to leave in a mostly diagonal position, to gain altitude AND horizontal speed.

Skipjack
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Re: Another Space Elevator Design

Postby Skipjack » Tue Aug 18, 2015 12:11 am

AcesHigh wrote:
Skipjack wrote:
AcesHigh wrote:what gravity losses?

Because you can focus on accelerating horizontally and need to spend less energy on getting to altitude, fighting gravity.


the tower is what, 20-30 km tall? You would still need to get 300 km higher for a decent dragless orbit. The gains would be marginal, after all, it would still need to leave in a mostly diagonal position, to gain altitude AND horizontal speed.

They are talking about building one for space launch that is over 100km tall. And I am not saying "dragless". I am saying that the vehicle experiences less drag losses on its way to orbit if it launched from that altitude. Either way, my point was that it would be negligible either way and not worth the spending the money on a tower like that.

AcesHigh
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Re: Another Space Elevator Design

Postby AcesHigh » Tue Aug 18, 2015 12:41 am

oh, I did not read about the 100km tall one.

such a structure would need to reduce $/kg by a HUGE margin to be worth it. However, unlike the space elevator (real one, that goes past geosynchronous orbit) you still need rockets to add a delta-v of 30 thousand km/h.

maybe at that altitude SSTO would be feasible however, Skylon would also make SSTO feasible and for a smaller cost.

Skipjack
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Re: Another Space Elevator Design

Postby Skipjack » Tue Aug 18, 2015 12:49 am

AcesHigh wrote:oh, I did not read about the 100km tall one.

such a structure would need to reduce $/kg by a HUGE margin to be worth it. However, unlike the space elevator (real one, that goes past geosynchronous orbit) you still need rockets to add a delta-v of 30 thousand km/h.

Yes, indeed. That is why I said, that it is not worth it. It is just another idea that looks good on paper, but does not get anywhere.

williatw
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Re: Another Space Elevator Design

Postby williatw » Tue Aug 18, 2015 2:33 am

An Earth based mass-driver that goes up Kilimanjaro mountain is probably more feasible; topped off with laser boosting:


http://everything2.com/title/The+Millennial+Project


Loved that book, still have and look at it once in awhile; to bad it hasn't happened yet.

Skipjack
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Re: Another Space Elevator Design

Postby Skipjack » Tue Aug 18, 2015 2:37 am

williatw wrote:An Earth based mass-driver that goes up Kilimanjaro mountain is probably more feasible; topped off with laser boosting:


http://everything2.com/title/The+Millennial+Project


Loved that book, still have and look at it once in awhile; to bad it hasn't happened yet.

And then your orbital inclination is limited to the direction of the mass driver, no to mention the relatively high g-forces...

williatw
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Re: Another Space Elevator Design

Postby williatw » Tue Aug 18, 2015 3:31 am

Skipjack wrote:
williatw wrote:An Earth based mass-driver that goes up Kilimanjaro mountain is probably more feasible; topped off with laser boosting:


http://everything2.com/title/The+Millennial+Project


Loved that book, still have and look at it once in awhile; to bad it hasn't happened yet.

And then your orbital inclination is limited to the direction of the mass driver, no to mention the relatively high g-forces...



Yeah your right about the g-forces, I believe it was decided it would be better used to launch cargo/components than live people. But once your in orbit as Heinlein said your half way to anywhere; don't have to sweat inclination too much. Launching components to be assembled in orbit for a large manned interplanetary vessel for instance. Of course there is still the idea of a real space elevator; thought Bradley Edwards was working on that for awhile. He came up with the revolutionary idea of using external power beamed to "runners" going up an initial ultra thin cable launched first to geo-stationary orbit by rocket (deployed by spool from the launched satellite downward to earth & further outward to counter-balance). Using the runners to feed line after line of cable until you get useful thickness for your elevator.


https://en.wikipedia.org/wiki/Bradley_C._Edwards

D Tibbets
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Re: Another Space Elevator Design

Postby D Tibbets » Tue Aug 18, 2015 2:31 pm

The idea may help with launch some, though it would be less advantagous compared to a launching aircraft, aka Pegasus. Here you get some forward velocity. With a 12 KM high launch platform there would be some imparted velocity. It would be directly (?) proportional to the velocity gained if the elevator went all of the way up to geostationary anchor point. Lets see... 12 km/ ~ 50,000 km = x/25,000km/hr, um, make that ~ 13,000 km/hr at geostationary orbit . The speed at the top of the platform would be about 3 km/hr- pretty much zero advantage.

Stabilizing the platform would be similar to the tallest sky scrappers, except very many times harder.

Landing on the platform would be difficult. I suspect landing on the ground and lifting the launcher back up the tower would be a better solution- a large internal elevator. Landing for a winged shuttle would be difficult because the lift available via the wings is much less than at sea level. Parachutes would also be more limited at that altitude.

In today's world, planning for sabotage is also critical. It would be an attractive target for terrorists.

Other than the Pegasus Rocket. I wonder if the old Air Force satellite interceptor is the best example of taking advantage of altitude and down range velocity. An F 15 would go into a steep climb and release the relatively small rocket, The launch conditions may have been between 500 to 1000 mph down range speed and 100-300 mph or more of vertical speed and launch altitude may have been 50-60,000 feet. The program had some successful tests but was abandoned (or at least hushed up), possibly for political reasons or technical challenges and safety issues.

Dan Tibbets
To error is human... and I'm very human.

krenshala
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Re: Another Space Elevator Design

Postby krenshala » Tue Aug 18, 2015 2:53 pm

Orbital velocity in a geosynchronous (Earth) orbit is 3.07 km/s.


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