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ATO cargo capacity?

Posted by: tkd720man - Fri Mar 06, 2009 11:34 pm
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ATO cargo capacity? 
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Post ATO cargo capacity?   Posted on: Fri Mar 06, 2009 11:34 pm
Any calculations or projections of how many tons of cargo the ATO concept could transport from orbit to the Earth's surface in a single trip?

I'm assuming that the carrying capacity of the Ascender is far less than that of the orbital airship, so is there any idea of how many Ascender trips would be required to transport that maximum cargo capacity from the DSS to the surface?


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Post    Posted on: Sat Mar 07, 2009 5:21 pm
ii'm also very curious about this, though i would assume the other way around- the ascender has a greater capacity than the orbital stage. after all it has to carry fuel too. also curious, how do you recover the orbital airship? can it brake in atmosphere in time to stay 100,000 ft up or do you have to keep some leftover fuel to slow it down?

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Post can it orbit?   Posted on: Mon Mar 09, 2009 11:47 am
I'm not really sure if the "orbiter" could actually go into orbit. The mass of helium in it's envelope would be huge. Accelerating that mass to orbital velocity, i think, would require more fuel than the orbiter could lift to altitude.

I think that the orbiters main purpose is to reach the "dark sky station", which i still think is a cool concept.


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Post    Posted on: Mon Mar 09, 2009 2:59 pm
no there's one, the real "orbiter", that is never supposed to go below the DSS, and then one that takes stuff to the DSS.

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Post    Posted on: Wed Mar 11, 2009 8:14 pm
As far as I remeber and understand the orbiter doesn't have no helium. It has extremely larger wings - 800 meters long - to be kept at altitude by the extremely thin air.

...



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Post    Posted on: Fri Mar 13, 2009 11:27 pm
You're right in stating that the Orbiter does not contain Helium. You're wrong in saying that it does not contain a lifting gas. At that altitude, the air is so thin Hydrogen is the best choice.

The Orbital airship floats to an altitude of around 170k feet using bouyuncy alone, then activates its engines. Its wings and bouyuncy carry it to 200k feet. At 270k feet, the benefits of bouyuncy are gone, and it uses its wings alone.

Reentry is the point where it shows its biggest advantage over traditional vehicles. Because of its wings and bouyuncy, the craft slows down entirely in the upper atmosphere, where the air is extremely thin. A consquence of this is that it takes longer to reenter, and so the heating is lower.


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Post    Posted on: Sat Mar 14, 2009 10:11 am
Hello, Terraformer,

according to jpowell the orbiter will be built at a DSS - at that altitude it wil return to. It does not go there from the surface and its buoyancy is provided by the large wings.

This I understand from jpowells informations. He doesn' talk of hydrogen but of the wings that are that large to get as much air particles under them that sufficient buoyancy is got.



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Post    Posted on: Sat Mar 14, 2009 4:27 pm
Ekkehard,

The wings can't provide lift when the craft isn't moving, especially since they're optimised for Hypersonic flight. To remain bouyount while at the station, Hydrogen is used to fill the wings. Not all that space is for cargo and people :)


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Post    Posted on: Sat Mar 14, 2009 9:07 pm
Hello, Terraformer,

in doubt the information from jpowell and JP Aerospace is essential and valid to me. I remember the explanation that the wings are that large to get that many air particles beneath them that sufficient buoyancy is provided.

Don't forget that the ATO will be at a DSS while not moving - then the buoyancy of the DSS will keep the ATO in 42 km altitude. The DSS wil be engineered so that it can keep the ATO there of its own if necessary.

When leaving the DSS the ATO is moving and will get sufficient buoyancy by its extremely large wings - according to the informations by JP Aerospace.



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Post    Posted on: Sat Mar 14, 2009 9:38 pm
JP said in Floating to Space that the Orbital Airship would be filled with Hydrogen for bouyuncy. It uses lift to climb to 170k feet, where it starts its engines. The wings are used for climbing above 170k feet.


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Post    Posted on: Mon Mar 23, 2009 7:59 pm
Ekkehard, you misunderstand how buoyancy works. The airship doesn't lie on top of the air any more than a hammer does. No matter how large the wings are, there is nothing keeping the air from flowing out from underneath them.

Next time you're doing the dishes, try taking a plate, holding it at the water's surface, and then pushing it down. The water will flow out from underneath the plate, run over the sides, and the plate will sink. It works the same for the ATO, except that gravity is doing the pushing.

Next, take a cup and push it down into the water, right side up. You'll notice the water level rising, and it takes quite a bit more effort to push the cup underneath the water than it did for the plate. The reason is that you're moving all that water upwards, against gravity. The reason that it takes more of an effort with the cup than it did with the plate is that the volume of the cup is larger than that of the plate. The volume of displaced water is equal to the volume of the object, so you're moving more water up, and that takes more of an effort.

So, what does this have to do with lifting gas in an airship? Well, the weight of the airship equals its volume multiplied by its density. The weight of the displaced air equals the same volume, multiplied by the density of the air. So, if the overall density of the airship is less than that of the air, then gravity will pull the displaced air down underneath the airship and it will go up. If the overall density of the airship is more than that of the air, gravity will pull harder on the airship, the air moves aside, and it will go down. That's why an airship is called a lighter-than-air vehicle. It's also why a football floats: the average density of the air inside and the ball itself is less than the density of water.

Like a football, an airship consists of a shell and a certain amount of gas inside it. The shell is heavier than air, but the lifting gas is lighter. As long as there is enough lifting gas compared to the amount of shell, the whole thing will still be lighter than air on average and go up.

Now, the higher up you go, the thinner the air becomes. In other words, there are less air molecules in a given volume; the air becomes lighter. At some point, the density of the air equals the density of your airship, and you will rise no further. That's the point where the DSS sits, and where the ATO turns on its engines.

Of course, for the ATO this point is higher than for the DSS. The reason for that is that the ATO has a lower density, and the reason for that is that it's bigger. Disregarding any attachments, an airship is just a big bag. Double its size, and you quadruple the size of the (heavier than air) surface (it's a 2D object, it gets twice as wide and twice as long so to speak), but you octuple the (lighter than air) volume (a 3D object, it gets twice as wide, twice as long and twice as high). So, enlarging your airship will lower its density and make it go higher. Unfortunately, the effect gets less and less as it gets larger, so at some point there's not much of a point to it any more. Which is why ATO doesn't go all the way to space on buoyancy alone.


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Post    Posted on: Mon Mar 23, 2009 10:52 pm
Very nice description! I like this type of communication it spreads the wealth of information and helps everyone. I sure would like to see more of this on the space fellowship after all it is a fellowship right! Good Job and thanks.

Monroe

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Post    Posted on: Tue Mar 24, 2009 6:39 pm
Hello, Lourens,

please believe me - I am not misunderstanding how buoyancy works. I don't refer to any understanding of it of mine - I simply and only refer to something I remember to have read under www.jpaerospace.com . I am looking for the exact source.

It's relevant for me that JP said in "Floating to Space" that Hydrogen wil be applied to achieve buoyancy - I simply didn't know about this issue by jpowell and don't have that book or any access to it.

In principle it is so that if I do know or have an understanding of something and innovative experts like jpowell say something different the innovator is more valid than my knowledge or understanding. I don't give up my knowledge and understanding but the innovator will have found something I need to understand before giving up my knowledge or understanding or before deciding that the innovator is wrong or in error.

And if it would turn out that the innovator states something that you say to be wrong but proves to be right in tests the innovator is right and you may or will have missed a thought, causal-logic link etc. Of course this is not the case here up to now.

But in between I have found the issue I refer(red) to:
Quote:
The third part of the architecture is an airship/dynamic vehicle that flies directly to orbit. In order to utilize the few
molecules of gas at extreme altitudes, this craft is big.
The initial test vehicle is 6,000 feet (over a mile) long. The
airship uses buoyancy to climb to 200,000 feet.
From there it uses electric propulsion to slowly accelerate. As it
accelerate it dynamically climbs. Over several days it reaches orbital velocity.
(source: ATO Airship to Orbit, page 2 under www.jpaerospace.com)

In this quote no hydrogen is mentioned but it is said that the few molecules of gas in the high altitude are utilized - it is said in the fourth sentence before the quote that that altitude is 140,000 feet. This does have nothing to do with my understanding of or knowledge about buoyancy - I merely tended to doubt that because of the quoted issue of jpowell. What might have happened really is that I unconsciously interpreted a meaning into the quoted issue that that issue doesn't have. But the few molecules of gas are utilized applying size or scale.



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Post    Posted on: Tue Mar 24, 2009 8:31 pm
Is this an Ion drive? That gets turned on?

Monroe

If so I wonder what the min pressure these will opperate at is?

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Post    Posted on: Tue Mar 24, 2009 9:43 pm
Ekkehard, only because one paragraph, of one document doesn't mention a "lifting gas" (hydrogen in this case), doesn't mean that there is none.

The size of the ATO is necessary to get a big enough volume for storing the hydrogen that provides the lift. Because the air is so thin up there, you have to make your airship truly big, or it will simply be to heavy (as strange as this might sound). It is just like Lourens has explained it. The reference in the ATO pdf about "few air molecules" imho really is a bit misleading and has nothing to do with aerodynamics in this case.

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