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balloon-supported vacuum space guns?



 
 
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  #1  
Old May 27th 17, 03:00 AM posted to sci.astro.amateur
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Default balloon-supported vacuum space guns?

If you have a 1-meter-diameter 80km long airless tube with a railgun inside it, and you use a series of tethers and balloons along the whole length to keep one end on earth and lift the other end up to 30km, then accelerating at 50G should give enough velocity to put something into low earth orbit. You have to keep it straight despite recoil and stratospheric winds or the projectile hits the sides. The atmosphere up there is 1% of sea level, and air spontaneously burns when you impact it at that speed, so it'd need to be streamlined and have an effective heat shield. And once it's out of the atmosphere, it needs some way to adjust orbit or it'll pass through the earth again at the end of its first orbit. The 30km-up end has to be open enough for the projectile to escape for a few seconds, so air will come in, that has to be actively evacuated. And the tube has to be very wide as far down as the air tends to leak because air will spontaneously explode and and do sonic booms. It's easy for an opponent to shut it down. But if you can do it, look ma, low earth orbit without rockets. Escape velocity is more of the same.

If you can get that to work reliably, you could build another one 2000km long and 10m in diameter along the earth that gradually slants up to 30km in its last 400km section. You'd accelerate horizontal for the first section, then accelerate only up in the balloon-supported section. Then 2G to 3G acceleration could reach low earth orbit, and you could launch shuttles with people. Possibly the whole human population in under a lifetime.
  #2  
Old May 31st 17, 05:25 AM posted to sci.astro.amateur
RichA[_6_]
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Default balloon-supported vacuum space guns?

On Friday, 26 May 2017 22:00:26 UTC-4, wrote:
If you have a 1-meter-diameter 80km long airless tube with a railgun inside it, and you use a series of tethers and balloons along the whole length to keep one end on earth and lift the other end up to 30km, then accelerating at 50G should give enough velocity to put something into low earth orbit.. You have to keep it straight despite recoil and stratospheric winds or the projectile hits the sides. The atmosphere up there is 1% of sea level, and air spontaneously burns when you impact it at that speed, so it'd need to be streamlined and have an effective heat shield. And once it's out of the atmosphere, it needs some way to adjust orbit or it'll pass through the earth again at the end of its first orbit. The 30km-up end has to be open enough for the projectile to escape for a few seconds, so air will come in, that has to be actively evacuated. And the tube has to be very wide as far down as the air tends to leak because air will spontaneously explode and and do sonic booms. It's easy for an opponent to shut it down. But if you can do it, look ma, low earth orbit without rockets. Escape velocity is more of the same.

If you can get that to work reliably, you could build another one 2000km long and 10m in diameter along the earth that gradually slants up to 30km in its last 400km section. You'd accelerate horizontal for the first section, then accelerate only up in the balloon-supported section. Then 2G to 3G acceleration could reach low earth orbit, and you could launch shuttles with people. Possibly the whole human population in under a lifetime.


Going to power it with...?
  #3  
Old May 31st 17, 11:42 AM posted to sci.astro.amateur
Martin Brown[_3_]
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Default balloon-supported vacuum space guns?

On 27/05/2017 03:00, wrote:
If you have a 1-meter-diameter 80km long airless tube with a railgun
inside it, and you use a series of tethers and balloons along the
whole length to keep one end on earth and lift the other end up to
30km, then accelerating at 50G should give enough velocity to put
something into low earth orbit. You have to keep it straight despite
recoil and stratospheric winds or the projectile hits the sides. The
atmosphere up there is 1% of sea level, and air spontaneously burns
when you impact it at that speed, so it'd need to be streamlined and
have an effective heat shield. And once it's out of the atmosphere,
it needs some way to adjust orbit or it'll pass through the earth
again at the end of its first orbit. The 30km-up end has to be open
enough for the projectile to escape for a few seconds, so air will
come in, that has to be actively evacuated. And the tube has to be
very wide as far down as the air tends to leak because air will
spontaneously explode and and do sonic booms. It's easy for an
opponent to shut it down. But if you can do it, look ma, low earth
orbit without rockets. Escape velocity is more of the same.


That is a heck of a lot of engineering for not much gain.

Superguns have been tried before and are doable even at atmospheric
pressure but the sonic boom annoys the neighbours. eg.

http://www.bbc.com/future/story/2016...saddam-hussein

If you can get that to work reliably, you could build another one
2000km long and 10m in diameter along the earth that gradually slants
up to 30km in its last 400km section. You'd accelerate horizontal
for the first section, then accelerate only up in the
balloon-supported section. Then 2G to 3G acceleration could reach
low earth orbit, and you could launch shuttles with people. Possibly
the whole human population in under a lifetime.


Wind loading alone would probably destroy it before you could finish
building it. There is a reason why skyscrapers maximum height is no
longer increasing so quickly these days. And that to get that final
height claim they have a very broad base and a big spike on the top.

http://deskarati.com/wp-content/uplo...-buildings.jpg

The inflation adjusted cost of the Great Pyramid at Giza was a surprise
to me. YMMV

--
Regards,
Martin Brown
  #4  
Old June 24th 17, 04:32 AM posted to sci.astro.amateur
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Default balloon-supported vacuum space guns?

On Wednesday, May 31, 2017 at 3:42:39 AM UTC-7, Martin Brown wrote:

That is a heck of a lot of engineering for not much gain.


Yes. Keeping it straight might be impossible. For example, if the 30km-up section is blowing steady left and the 15km-up is blowing steady right, that might make it impossible for it to be made straight enough to be usable. The biggest gain is for the people-launcher version. But it's at least as feasible as any other design I've seen that could launch the whole population into orbit. (1960s Orion and space elevators are competitors.)

Superguns have been tried before and are doable even at atmospheric
pressure but the sonic boom annoys the neighbours. eg.


Sonic booms in a vacuum aren't too annoying. Ditto for sonic booms 30km up..

Wind loading alone would probably destroy it before you could finish
building it.


Could be.

There is a reason why skyscrapers maximum height is no
longer increasing so quickly these days. And that to get that final
height claim they have a very broad base and a big spike on the top.


The balloon supports make that irrelevant, it's under tension not compression.

  #5  
Old June 24th 17, 04:46 AM posted to sci.astro.amateur
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Posts: 5
Default balloon-supported vacuum space guns?

On Tuesday, May 30, 2017 at 9:25:51 PM UTC-7, RichA wrote:

Going to power it with...?


Electric cables, batteries or capacitors, electromagnets.
  #6  
Old June 24th 17, 05:17 AM posted to sci.astro.amateur
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Default balloon-supported vacuum space guns?

On Friday, June 23, 2017 at 8:46:08 PM UTC-7, wrote:
On Tuesday, May 30, 2017 at 9:25:51 PM UTC-7, RichA wrote:

Going to power it with...?


Electric cables, batteries or capacitors, electromagnets.


Wait, wait ... stratospheric winds are somewhat predictable. They blow from the east to the west along the equator, and from the west to the east above about 30 degrees latitude. West to east is better for launches. The balloons would be pulled by the wind away from the anchor, which is what you want, tension not compression. If you make the balloons streamlined, there's less resistance. If you give them rudders, they can steer, quickly compensating for changes in wind direction themselves. And if you give them turbines they can generate all the power you need in place. They can give aerodynamic lift, not just relying on being lighter than air.
  #7  
Old June 27th 17, 05:40 AM posted to sci.astro.amateur
RichA[_6_]
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Posts: 1,076
Default balloon-supported vacuum space guns?

On Friday, 23 June 2017 23:46:08 UTC-4, wrote:
On Tuesday, May 30, 2017 at 9:25:51 PM UTC-7, RichA wrote:

Going to power it with...?


Electric cables, batteries or capacitors, electromagnets.


Good luck and remember Gerald Bull.
 




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