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#51 2007-11-29 09:44:50

samy
Banned
From: Turku, Finland
Registered: 2006-01-25
Posts: 180
Website

Re: Space Elevator or Scramjet?

A 10g (centrifugal) launch ring would be able to launch bulk goods as fast as desired. A bulk delivery could be accelerated tangentially at 1,000,000 g if we felt like it, that's not a problem. Big accelerations can be achieved however we like. It's the small accelerations (for humans and non-bulk goods) that have high requirements.

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#52 2007-11-29 09:51:24

Antius
Member
From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: Space Elevator or Scramjet?

There's no realistic way to get the gs down to merely tens with a mass driver. Even hundreds of gs is pushing it.

Maybe as a nationwide megastructure, barely.

For the record, here are the numbers:

For a 10 g force pressing you against the launch ring's outer wall, you will need a launch ring 1230km in radius (2470km in diameter).

100g, 123km radius.

1000g, 12.3km radius.

10000g, 1.23km radius.

I could see a 10000g mass driver being built, but beyond that is going to get real expensive, real fast.

And there's no reason to build multiple mass drivers. If you built a 10g one, you could also use it for the medium and bulk goods.

Some numbers for added clarity:

For a mass driver 100metres long and an exit speed of 10km/s, a mass driver with acceleration 50,000g is needed.

Total acceleration time = 0.02seconds.

Total energy required = 50MJ/Kg (probably closer to 60 including losses)

Total power required during acceleration = 2.5GW/Kg.

That's a lot of power pouring into a very small projectile. The odds are that it would melt within the barrel.  Transmitting that much power to the balloon using beamed propulsion would appear highly dubious to me.

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#53 2007-11-29 09:54:55

Terraformer
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From: The Fortunate Isles
Registered: 2007-08-27
Posts: 3,906
Website

Re: Space Elevator or Scramjet?

I thought it would be in a vacuum so all the energy was kinetic?


Use what is abundant and build to last

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#54 2007-11-29 10:03:37

samy
Banned
From: Turku, Finland
Registered: 2006-01-25
Posts: 180
Website

Re: Space Elevator or Scramjet?

Total power required during acceleration = 2.5GW/Kg.

That's a lot of power pouring into a very small projectile. The odds are that it would melt within the barrel.

Of course, you could just take it easier and use a mere 8MW of power, which would still fire off the projectile in 7.6 seconds.

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#55 2007-11-29 10:13:22

Terraformer
Member
From: The Fortunate Isles
Registered: 2007-08-27
Posts: 3,906
Website

Re: Space Elevator or Scramjet?

There is a thread called Mass Drivers.


Use what is abundant and build to last

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