Author Topic: Huge 'launch ring' to fling satellites into orbit  (Read 11841 times)

Offline publiusr

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #20 on: 10/17/2006 10:59 PM »
"We think HLLVs are too big and wasteful."

So what do you propose instead?

"Well, we'll just build this 50 km long tra----why are you laughing?"

Offline rfoshaug

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #21 on: 10/24/2006 08:52 AM »
It's a fun idea, like stepping into a cannon shell and being shot to the moon or something like that. But it's completely unrealistic.

- What heat shield is needed to prevent it from disintegrating while travelling at 8 km/s at near sea level?
- You'll need a rocket engine to circularize the orbit (since the original orbit will intersect the Earth's surface). How do you build a rocket engine that survives 2,000 G's?
- How far away will the sonic boom be a problem?
- Since the 30 ramp is a fixed structure, you'd only get a fixed inclination for the launches, and if used as a weapon, the fixed launch direction would be a serious limitation. Except if you have aerodynamic surfaces or rocket engines that can alter the inclination (all of which would have to survive 8 km/s at near sea level as well as 2,000 G's)...

Offline ShotInTheDark

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #22 on: 10/24/2006 11:41 PM »
Quote
rfoshaug - 24/10/2006  1:35 AM
But it's completely unrealistic.

Realisticism is a useful belief system much of the
time.

But is the quibble with reality itself, or reality's scope--to put it another way--are the uncertainties of tomorrow, too far away today?

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- What heat shield is needed to prevent it from disintegrating while travelling at 8 km/s at near sea level?

1) Enclose the acceleration track in a vacuum

2) Build the ascent path--also a vacuum--up the side of a structure (could be geographic, ie a mountain)

3) Release the payload to the atmosphere only at such altitude where the heating will not kill the vehicle

Piece of cake, right?  ;)

Offline nacnud

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #23 on: 10/25/2006 09:41 AM »
If you look at the article the heat sheild for the projectile/rocket was a large lump of tungsten, no need for anything too fancy.

Offline rfoshaug

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #24 on: 10/25/2006 10:05 AM »
A large lump of tungsten... Well that might work. By the way, the word "tungsten" in Swedish translates to "heavy stone". And tungsten is quite heavy, which only increases the challenge of keeping it on track at 2,000 G's.

Even if you release the payload on top of the highest mountain in the world (at 8,850 meters), you'd still have quite a challenge of not burning up at 8 km/s. Besides, the fixed launch direction would be a major disadvantage.

Also, how do you keep a vacuum in a tube that's open in the end (where the vehicle leaves)?

How many G's of deceleration due to atmospheric drag does one expect at this speed and altitude? How much speed is lost before you're in space? How much fuel and how big rocket engines will be needed to circularize the payload so that it stays in orbit?


There are lots of pieces of cake that need to be addressed here... :)

Offline meiza

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #25 on: 10/25/2006 11:25 AM »
You can have a shutter or a membrane at the end of teh sealed tube. :)

Offline ShotInTheDark

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #26 on: 10/25/2006 01:53 PM »
If transitioning from vacuum, to smashing into a brick wall of atmosphere would result in LOV, then one might mitigate such a forceful impact over a longer period of time, with the payload passing through a series of atmospheric chambers of increasing density.

But looking ahead, do I think this monster can fly 50 years from now?

No.

Every step of the way this beast has become more convoluted.  By today's standards, it's akin to a Rube Goldberg machine, an excrutiatingly complex gizmo which performs what in comparison is a relatively simple task.

Fun to look at, yes, nice to ponder when there's nothing better to do, but good grief, we already have rockets which are doing quite well thank you very much!  So what's the point?

One answer is, to a very small extent, there's always those lucky and talented few who bring elegance and simplicity to what was once befuddlement and terrible complexity.

So whilst many in the industry do the magnificent and equally important job of gradually improving existing technology, from many of these same people comes unexpected innovations, new technologies which radically buck the odds in our favor.

And however remote the odds of this are with the launch ring concept, it is nonetheless refreshing that the eternal optimists, and the bean counters, have kept the discussion honest for all those wizened realists.

Quote:
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There are lots of pieces of cake that need to be addressed here...


^ Yup. ;)

I say let all of 'em have their cake and eat it too!

Offline Marcus

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #27 on: 10/26/2006 05:07 PM »
I reject your reality and substitute my own. :)
OPS!
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Offline rfoshaug

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #28 on: 10/27/2006 08:59 AM »
ShotInTheDark,

You are absolutely correct, and I'm sorry If I sounded too negative. My point was that it doesn't seem practical as a launch system in the near-term future, but that doesn't mean it shouldn't be explored, as there's lots to be learned along the way, which might have uses in other applications as well.

:)

Offline ShotInTheDark

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #29 on: 10/27/2006 11:11 AM »
Thanks for the post rfoshaug, and agree totally that it isn't practical near term.  It is far too early on, and there are too many hurdles yet to overcome, before such an idea should have any sort of mini-monopoly on resources or manpower.  Rught now it is a good area to develop some pet theories and perform small scale experiments, hopefully gaining some idea on where to go next---if one should proceed any further at all.

Every idea that you've brought up has been valuable, and if you've got any other trouble spots to point out, we'd all be the better for hearing them.

Offline hop

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #30 on: 10/27/2006 11:07 PM »
One thing to keep in mind is a lot of those problems go away if you build it on the moon. Furthermore, launching bulk raw materials such as refined metals is something you might want to from a real moon colony. Doing it on Mars isn't quite as attractive, but still much easier than earth.

Offline meiza

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #31 on: 10/28/2006 09:53 AM »
a slingshot is better on the moon?

Offline mauk2

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #32 on: 10/28/2006 03:16 PM »
LOL!  Well, not a slingshot, exactly, but mass drivers.

The Moon has a much shallower gravity well than Earth, which means escape velocity is far lower.  Lower escape velocity means that the energy needed to accelerate a given mass to that speed is FAR less.  Far less energy = much smaller driver that can operate at much lower stress.

Oh, and the fact that the Moon's surface is a pretty good vacuum is a gigantic plus as well.  No need to try and ram payload through the soup at Mach 26.  As the old Sprint missile showed,  airframe loading deep in the soup is a huge challenge in and of itself.

Once we get out of the cradle, many of the engineering dictates get a LOT easier. That first step is a real doozy.

Offline meiza

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #33 on: 10/29/2006 06:30 PM »
Just meant that on the moon, a linear accelerator is bigger, more expensive and less flexible than a rotating centrifuge-type accelerator. Ie a rotating pole where two tethers are attached, one has a counterweight and the other the payload to be accelerated.

Offline jimvela

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #34 on: 10/29/2006 07:27 PM »
Quote
meiza - 29/10/2006  12:13 PM

Just meant that on the moon, a linear accelerator is bigger, more expensive and less flexible than a rotating centrifuge-type accelerator. Ie a rotating pole where two tethers are attached, one has a counterweight and the other the payload to be accelerated.

That would work great- right up to the point where you released the payload.  Then what do you do with the counterweight?

Offline meiza

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #35 on: 10/29/2006 08:32 PM »
After lots of searching I found the info back in this thread about the lunar sling:
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=872

But seems a user's post with pictures was removed (that's why the the thread was so damn hard to find). Database problem or was it copyright material?

Offline meiza

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #36 on: 10/29/2006 08:34 PM »
Ah well there is the same material (with pretty picture!) available from AIAA here, it's a preview of an article, the first page which is free:
http://pdf.aiaa.org/preview/1990/PV1990_2109.pdf

Offline Joffan

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #37 on: 10/29/2006 10:32 PM »
Quote
jimvela - 29/10/2006  1:10 PM

Quote
meiza - 29/10/2006  12:13 PM
... a rotating centrifuge-type accelerator. Ie a rotating pole where two tethers are attached, one has a counterweight and the other the payload to be accelerated.

That would work great- right up to the point where you released the payload.  Then what do you do with the counterweight?

You could either launch two payloads simultaneously, or have the counterweight released simultaneously into an energy recovery system. For example, a heavy short-arm counterweight could be sent up a hill and latched.

This would probably be easier if the counterweight (rather than the axis) is used to drive the system, although control mechanisms are good enough that it shouldn't make any difference.
Max Q for humanity becoming spacefaring

Offline TyMoore

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Re: Huge 'launch ring' to fling satellites into orbit
« Reply #38 on: 10/30/2006 01:15 AM »
Interesting, clever...If the bucket was made to resemble a hopper, then at the moment of payload release, almost all of the ballast mass could be dumped--provided of course there wasn't anything nearby for it to hit. If typical standard delta-v increments were required for payloads released on similar trajectories, then it is concievable that a suitable area could even be prepped as a 'bucket landing zone' if one wanted to cut the bucket loose completely.  Leaving a small ballance ballast mass attached to the bucket end of the cable should allow for a balanced 'reel' in of the payload deployment cable back to the tower. This is an interesting concept that I haven't seen until now...

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