Author Topic: Air Supported Structure to support multiple Mass Drivers  (Read 781 times)

Offline Cognisant

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Hello I'm new nice to meet you all, I've no credible background in aerospace, rocketry or anything relevant to this site, except maybe IT support but you seem to have that well covered, I'm here to float an idea and hopefully learn something by seeing it shot down.

For anyone wondering what's this "air supported structure" nonsense:
https://en.wikipedia.org/wiki/Air-supported_structure

I'm familiar with the StarTram concept so rest assured I'm not reinventing that wheel rather I have an idea for how the mass driver track can be supported/stabilized which is daunting in scale but seems economical if the megastructure is used to support multiple mass driver tracks. You know those inflated Redbull air racing pylons, or maybe jumping castles are a better example, anyway my idea is to make a conical mountain of air 20km tall and 40km wide (45 degree slope) covered by PVC coated nylon/Kevlar/whatever mesh, on the ocean and weighted down, with as many mass drivers running up the sides as is practical.

Of course you wouldn't have all the tracks meet at the apex ::) but rather angled slightly off so the packages/craft can safely pass by each other, indeed it would be more of a plateau than an apex.

Yes it's a huge project, yes it would cost many billions of dollars, but in terms of getting lots of stuff into space really quickly only an orbital ring would be better and I don't see how anyone can build one of those without building some kind of mass driver system first. Economically the investment would be enormous but assuming there's a demand to get lots of stuff into space really quickly, and we're still launching rockets despite how wildly expensive they are, it could be somewhat profitable.

Offline stefan r

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Re: Air Supported Structure to support multiple Mass Drivers
« Reply #1 on: 09/25/2017 10:13 PM »
Hello I'm new nice to meet you all, I've no credible background in aerospace, rocketry or anything relevant to this site, except maybe IT support but you seem to have that well covered, I'm here to float an idea and hopefully learn something by seeing it shot down.

For anyone wondering what's this "air supported structure" nonsense:
https://en.wikipedia.org/wiki/Air-supported_structure

I'm familiar with the StarTram concept so rest assured I'm not reinventing that wheel rather I have an idea for how the mass driver track can be supported/stabilized which is daunting in scale but seems economical if the megastructure is used to support multiple mass driver tracks. You know those inflated Redbull air racing pylons, or maybe jumping castles are a better example, anyway my idea is to make a conical mountain of air 20km tall and 40km wide (45 degree slope) covered by PVC coated nylon/Kevlar/whatever mesh, on the ocean and weighted down, with as many mass drivers running up the sides as is practical.

Of course you wouldn't have all the tracks meet at the apex ::) but rather angled slightly off so the packages/craft can safely pass by each other, indeed it would be more of a plateau than an apex.

Yes it's a huge project, yes it would cost many billions of dollars, but in terms of getting lots of stuff into space really quickly only an orbital ring would be better and I don't see how anyone can build one of those without building some kind of mass driver system first. Economically the investment would be enormous but assuming there's a demand to get lots of stuff into space really quickly, and we're still launching rockets despite how wildly expensive they are, it could be somewhat profitable.

You will have a problem getting enough acceleration in the short distance.  28.3 km is not long enough for humans or sensitive cargo. 

20 km is still in the atmosphere.  It is much thinner but you still have to deal with it.  The payload needs a heat shield.  The track would still have to be vacuum tube with some sort of window at the end. 

The rail(s) is supported by air pressure.  The air presses against nylon (or kevlar etc).  The base of the sheet has to support the force of the air pressure on 126 km circumference.  Thick material will add weight to the pylon and increase the air pressure.

You are using 1.78 x 109 square meters of fabric in your cone.  Compare to a cable stayed cantilever.  The cables could be mostly nylon(or kevlar, graphene etc) and do not need to be air tight.  The mast needs to support itself, 28km of track and some ~40 km length cables.  The mast could be much shorter than 20 km.

They have built a tower over 800 meters tall in Dubai.  20 km is very ambitious. 

Offline RobLynn

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Re: Air Supported Structure to support multiple Mass Drivers
« Reply #2 on: 09/27/2017 10:41 PM »
Interesting idea, try doing a basic costing of it.  Suspect that you will find cost dominated by pressure loads near base, and also extra strength required for wind loads will be high.  Inflating with nitrogen at close to 100% humidity might just help in this regard - as it's lower density than air would give slowly increasing pressure differential with altitude.

How about instead doing a floating structure something like the eiffel tower with bottom at 15-20km altitude above the worst winds in the troposphere and top at 40-50km, put near equator to avoid worst of winds.  By supporting upper structure on 3 or 4 big balloons at base it works something like a tower mounted on floats in the ocean.
I'm a "glass is twice as big as it needs to be" kinda guy

Offline stefan r

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Re: Air Supported Structure to support multiple Mass Drivers
« Reply #3 on: 09/29/2017 01:47 PM »
... Inflating with nitrogen at close to 100% humidity might just help in this regard - as it's lower density than air would give slowly increasing pressure differential with altitude...

It would rain inside and deflate.

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