h a l f b a k e r yThe best idea since raw toast.
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Ok... I was thinking the other day about this idea, I
wondered... How about a Super Hubble Space Scope...
here is how it works... you send out a new hubble... this
hubble is half the size of the present hubble and only
consist
of a high definition CCD, just like the hubbles... you dont
have
to worry about special power systems becuase my idea is
two-
fold...
Ok, here it is... (note: you would have to get into deep
space
to use it...to avoid impacts and debree) My idea is a giant
inflatable parabolic lens shaped balloon...
And I Mean Giant!... since you wouldnt really need much
pressure to inflate a balloon in a vacume And the shape of
the
lens balloon could be altered by varying the pressure inside
the inflatable lens... the lens would be perfect becuase its
a
balloon... and its cheap and you could bring a few for
redundancy if one did happen to get hit by a impact... Also
I
am sure you could use it to generate energy using a interior
solar cell... you would have to close the CCD to protect it...
but in this way... it would be nearly perpetual in its
operation... When I say huge lens... Imagine as big as you
can...
And since these Probes would be so cheap and redundant
you could launch multiple Super Hubbles and join them
together to creat one truely giant eye...
what do ya think...
NASA to boldly go
http://www.newscien...s.jsp?id=ns99992955
Recently announced NASA idea to put telescopes at the Lagrange points in Earth-moon orbit. [krelnik, Oct 04 2004]
Sci-Astro thread
https://groups.goog...astro/c/-JAw0Ei6bEo
Discussing ideas for space telescopes. Part way through, someone suggests the use of a mylar balloon. [mitxela, Feb 17 2022]
Bend-Forming of Large Electrostatically Actuated Space Structures
https://www.nasa.go...d_Space_Structures/
[xaviergisz, Jan 31 2023]
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Spelling police: debris, not debree; vacuum not vacume, because, not becuase, truly, not truley.
What happens when a meteorite hits the balloon? |
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The lens, being filled with gas, rather than glass, would have little ability to refract light (a refractive index close to that of a vacuum). And it would be impossible with a balloon to maintain a true shape with the sort of fine control required in a telescope's optics. |
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let me define what I mean... |
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the blow-up lens would have one half of the lens shape
silvered on the outer rim and have transparent center
and the opposite half of the balloon would be silvered in
the center and transparent outer rim... creating a huge
variable shape parabolic telescope... |
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I probably should have included that... |
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If it's in deep space, how is the solar power element going to work? |
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Not that my skepticism should burst your balloon, but I would be surprised if a material could be found that supports both inflation and the kind of optical fidelity needed to make this thing work with usable results. Specifically, I doubt that the light once it had passed through the first surface of this rig would be in any kind of condition from which to capture a usable image. |
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what ub said; but also the fact that it would take *ages* to get there (interstellar space--i take it you mean outside of our galaxy; the nearest star, for example, proxima centauri, is 4 ly away and we can't travel anywhere near the speed of light) and then it would take years for the signals to get back to earth. also, you'd get all sorts of refraction issues because of cosmological redshift (relatively small, i suppose, if you kept it close by), interactions with interstellar dust, hubble shifts from earth's motion, etc... would make clear images difficult i think.
... interesting idea nonetheless--but practically probably non-workable. |
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UB - If there is pressure for it to burst - there is pressure for it to work. |
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I hear NASA have stopped talking to Deep Space One. |
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[Rods Tiger] - That would be debrie |
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<pa>more appropriate ending: "... to deflate your balloon." It does seem weird to see you go on and on about the gas pressure vanishing, and then say something that requires high pressure.</pa> |
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There actually is a serious proposal to put a telescope quite a long ways out into space, well beyond Pluto's orbit. If I recall right, at about 530 Astronomical Units (one AU = distance from Sun to Earth), the Sun's gravity acts as a focal point ("gravitational lensing"). Putting a imaging system at that point means that you are using a "lens" that is something like a million miles wide. |
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Is that big enough for you? |
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Peek-a-boo, I see you, UB. |
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Interesting idea, wrong approach, though. |
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Instead of the lens, use a giant mirror. All you'd need is a reflective coating. The curvature does the rest. |
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As for irregularities in the mirror, wouldn't a huge aperature mean that the usual optical tolerances (ie a wavelength of light) would be thrown out? Would deformations in the mirror of a few feet be allowable as the photons coming from the flaw would be minute compared to those coming from the rest of the mirror? |
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Side note: Interferometry can do this much cheaper and be redundant. There are plans to put arrays of telescopes in orbit around the sun, each with a relatively small resolving power. But when combined, they act as a single massive lens. |
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I migrated a very similar (and more recent) idea about m2p2 to this category. Started out as a halfcrumb on terraforming. I don't see gas freezing as a major problem--in fact the reflective qualities of a pneumoastromirror might be much improved by a gas that crystalized in a uniform way...As for the distortion issues, I suppose you could have a mirror that flopped all over the place so long as you kept track of its every twitch by radar and combined everything together in the right order. The point about lots of small telescopes is a good one. Maybe the definition of small will inflate, however. |
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I'm going to have to go with [rapid transit] here, combining smaller telescopes into one bigger telescopes is the next big thing... made of smaller things. [-]. |
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Make it out of Hubba-Bubba chewing gum, and you could have a Hubba-Bubba Hubble Bubble. |
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Nice idea oxygon, Sorry I have to rant on this. |
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Has anyone ever tried measuring the optical quality of a mylar bafoon using a zygo? I'm wondering if you could get..say..1/20th wave pv. Most likely not. Plus, how can you make it if you can't measure it? Freaking impossible, not even worth a thought. ....I don't undrestand : ) bang bang bang. Wow that hurts!
I can't imagine how difficult this would be. It's hard enough grinding a big mirror with so many known and measureable perameters here on earth let alone the vastness of a 5 billion AU freaking ballon. I just can't come up with all the data to back up my amazment at this wonderful idea. BONE |
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A couple thoughts - Helium should exist as a gas in the relatively high vacuum of space and at the relatively less high vacuum inside the envelope. At STP helium boils at ~4K. Also the tiny bit of heat from the electronics could warm the gas if something other than Helium were used. Secondly, radio waves seem more forgiving, use an appropriatly coated mylar bag as a radio telescope like Arecibo. One pickle I see is the mounting of the instruments. They could float weightless inside the sack and use small fans to "fly" into position. Cabling might distort the reflector or set up resonance that would disturb the alignment. Another idea might be to make the envelope spherical. As I recall at one-half the radius a significant part of the sphere inner surface would be very close to parabolic. Then you might use the envelope as both a receiving and transmitting "dish", if it could be apertured properly and the transmitter and reciever separately positionable. |
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I had the idea of an inflatable parabolic reflector space
telescope, did a search, and found this one. |
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I'm surprised about the amount of negativity the idea got. |
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I read that to resolve features on an exoplanet, we're going
to need a telescope of 40km diameter. An inflatable
parabolic reflector is about the only way I can imagine that
this size could be achieved. |
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The tricky part is figuring out ways to keep the shape of the
parabolic reflector perfect enough to act as a telescope. |
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The mylar sheet could be reinforced with fibres (at the back
surface). The sheet could be folded together 'origami
style'. |
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The reinforcement fibres could be made of a material that is
flexible above a threshold temperature, but becomes rigid
as it cools in space after being inflated. |
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The telescope could use adaptive optics to compensate for
imperfections in the primary mirror. |
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A telescope of this size and fragility could probably not be
easily reoriented. So it could be used to monitor a single
exoplanet. It could have a large flywheel/gyroscope
(perhaps ring shaped around the edge of the parabola) to
keep it pointed in one direction. |
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[xaviergisz] maybe use [pashute]'s Fluid Flywheel idea, but
using gas in the inflated rim. The "mirror" can be on the
outside surface, held mostly by the inflated rim, with some
supports behind to maintain shape. |
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Park another telescope at another Lagrange point,
and use the interferometry with the Webb. |
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[xaviergisz] It's a good idea, hampered by [oxygon]'s terrible presentation. |
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I can think of a few ways of correction for spherical aberration, beyond only silvering a small portion in the middle. You could vary the thickness of the material, so that the balance between elasticity and the inflating gas distorts the natural shape of the balloon. |
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Another option is to spin the entire balloon, and let the centripugal forces distort it into an oblate spheroid. This may in fact make the aberration worse, but it might provide some degree of focussing. |
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A third possibility would be to accelerate the whole thing in the direction of interest. A very long cable attached to the front, with a spaceship acting as a tug. It would have to accelerate at a constant rate until the shape stabilized, but the amount of acceleration would control how distorted the balloon became. Similarly, a constant distortion of this type could be achieved by placing a counterweight on the end of the cable, and rotating the whole assembly, but since it would no longer be facing a fixed direction in space, the utility of such a telescope would be questionable. |
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Further thoughts: Assuming balloon physics follows the physics of bubbles, a membrane stretched over a circular opening, subjected to a pressure differential, becomes a segment of a sphere. Instead of building a whole balloon, build a solid ring, and stretch two layers of mylar across, one silvered and one transparent. When you inflate the gap between the layers, both would bulge outwards and assume spherical curvature. By varying the gas pressure, you would be able to adjust the radius of curvature, and by keeping the radius large enough, you wouldn't need to worry about spherical aberration. |
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//vary the thickness of the material, so that the balance
between elasticity and the inflating gas//
This I like. Should be able to get a parabola; I suspect it's
probably a linear relationship between spring rate & radius
(parabolas are pretty simple). |
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I think it is the James Webb telescope that is
being referenced in one of the comments. It
mentions the Lagrange point. |
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