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Large Balloon Reflector: a potentially game-changing antenna design
- kunwon1 3y agoMakes me wonder about an inflatable balloon antenna for amateur radio. I wonder how hard it would be to do this sort of fabrication (aluminizing the inside of a balloon) as an amateur Better pictures here https://www.freefallaerospace.com/nasa-balloon/ https://www.freefallaerospace.com/nasa-balloon/
- itishappy 3y agobuy space blanket (aluminized mylar) tape it over garbage can suck ??? profit
- cwkoss 3y agogreenpowerscience is a fun channel who did a neat version of this https://www.youtube.com/watch?v=-1GV3FIOR6E https://www.youtube.com/watch?v=-1GV3FIOR6E
- aqfamnzc 3y agoJust need to find a parabolic garbage can!?
- eternauta3k 3y agoNo, the garbage can just supports the edges.
- ianburrell 3y agoI don't think it would be useful for most amateur radio which doesn't need the gain and balloon would be huge. It would be useful for people who do higher frequencies and use satellite dishes. Portable link to 2.4GHz mesh network would be example. It might also be useful for cheaply making big dishes for Moon bounce.
- dmbche 3y agoI can't see a picture of the concave shape, I was under the impression that the design is that one third of the sphere is collapsed inside itself to make a nice concave antenna that's cheap and light - is this what's happenning? Edit0: Nope! Part of the sphere is transparent, and the inside is reflective. Nothing collapsed. And it's working very similarily to a normal parabolic antennae, but being inflatable it's way lighter/smaller, leaving more weight and room for power and instruments. Massive win!
- smoyer 3y agoTransparent to some portion of the electromagnetic spectrum ... We might not be able to see through it though.
- aimor 3y agoA good idea. I wonder how robust it is to small debris, I assume it won't pop but will the thin material fold up on itself if there's a hole?
- Terr_ 3y agoI guess it depends on the odds (impacts per cross-section per time) for different debris size/composition/speeds in the planned orbit. I'm sure somebody's studying that, but I'm also sure it must involve a lot of complicated tables. The particular mini-satellite is slated for a 6-month mission, so presumably they think it'll survive at least that long.
- morcheeba 3y agoThat was my first thought, too. My ideas was to make the plastic UV-curable so it would become rigid and not require inflation. I looked it up, and that's what they're doing - UV-curable ribs. It's also not a sphere; it has an inflatable ring. Pictures & paper here: https://asteroid.arizona.edu/KABAND_Inflatable_v3_public.pdf https://asteroid.arizona.edu/KABAND_Inflatable_v3_public.pdf
- ortusdux 3y agoReminds me of Project Echo https://en.wikipedia.org/wiki/Project_Echo https://en.wikipedia.org/wiki/Project_Echo Remastered documentary: https://www.youtube.com/watch?v=19kAuAVAnDc https://www.youtube.com/watch?v=19kAuAVAnDc Scott Manley: https://www.youtube.com/watch?v=19kAuAVAnDc https://www.youtube.com/watch?v=19kAuAVAnDc
- itishappy 3y agoAlso NASA's Inflatable Antenna Experiment, which looks like it spun off a successful commercial product. https://en.wikipedia.org/wiki/Inflatable_Antenna_Experiment https://en.wikipedia.org/wiki/Inflatable_Antenna_Experiment https://spinoff.nasa.gov/Spinoff2010/ps_5.html https://spinoff.nasa.gov/Spinoff2010/ps_5.html https://www.cubic.com/inflatable-satellite-antenna https://www.cubic.com/inflatable-satellite-antenna
- uoaei 3y agoI'm a little confused because the article uses 'spherical' and 'parabolic' seemingly interchangeably. I'm sure the scientists know what they're doing but just found the imprecision a bit odd for a nasa.gov article.
- andreareina 3y agoI understood it as, the structure is spherical, with one parabolic surface that acts as the antenna.
- teo_zero 3y agoNo, it's spherical. Instead of a transceiver placed in the focal point, they use array of min. 3 transceivers. It will definitely not have the same gain of a parabolic of similar size, but it will be more flexible about where the target it aims at must be. They are advertising it not for communication from fixed point to fixed point, but rather between vehicles that are continously moving, where a less directional solution will be an advantage.
- istjohn 3y agoThis page states that it is spherical. https://www.freefallaerospace.com/nasa-balloon/ https://www.freefallaerospace.com/nasa-balloon/
- uoaei 3y agoNice, thanks for finding that. Excerpt: > FreeFall’s antenna technology is unique because it is using a spherical reflector. In the past, antennas always used a parabolic antenna. A parabolic antenna focuses energy to a “single point” – while a spherical antenna focuses energy to a “focal line”. Parabolic antennas are symmetric about only one axis which severely limits field of view. It also requires precise pointing for high gain and has more complex packaging, deployment and on-orbit operations. The spherical antenna provides a wider field of view for antennas and high gain without re-pointing of an antenna. Combining a spherical antennas with inflatables is the key to achieving a large aperture in a simple lightweight system.
- smeej 3y agoI'm oversimplifying, but this is how I read it as a layperson, with a fair degree of joy! NASA, for decades: Launching antennae into space is a difficult, costly procedure that requires billions of dollars. Also NASA: Hey, what if we just...made the inside of one side of a clear balloon shiny??
- foota 3y agoWho would win, the space industrial complex or one shiney balloon boy? Given the other comment about this below (https://news.ycombinator.com/item?id=38044638 https://news.ycombinator.com/item?id=38044638), I'm surprised this hasn't been done sooner though, I wonder if there's some missing downside?
- jdironman 3y agoOne thing I am wondering about is SAT to SAT communication. I imagine the receiver / transmitter is facing "down", or is it maneuverable and does SAT to SAT support something like a BGP router network or something to ensure optimal comms.
- s1artibartfast 3y agoThere are tons of downsides and tradeoffs. Top concers I would have is working lifetime, stability, and percision. You don't want a dish that is continually changing shape. Gas and materials shrink and expand as temperature changes. The balloon will also leak.
- awesomeMilou 3y agoThese sound like manageable problems in space though. Overall the temperature of the balloon will stay pretty constant if it stays on a fixed orbit around the sun. The argument about precision I don't understand - the article talks about creating telescopes with this concept but NASA wants to use this for radio communication - the comparison with JWST doesn't apply, as it's mirrors had to be manufactured to a much higher tolerance. > lifetime I mean we had bigelow Aerospace with their module and it seems to be pretty durable. [0] [0] https://de.wikipedia.org/wiki/Bigelow_Expandable_Activity_Module https://de.wikipedia.org/wiki/Bigelow_Expandable_Activity_Mo...
- slowhadoken 3y agoReminds me of the 320th Barrage Balloon Battalion.
- pmorici 3y agoIs the idea here that this is new for outer space? There are ground based inflatable antennas that you can buy that have been around for a few years. I’ve heard a trade off with these is they aren’t very ridged so in windy conditions they don’t work that great. Maybe that is less of a problem in outer scpace. https://www.cubic.com/inflatable-satellite-antenna https://www.cubic.com/inflatable-satellite-antenna https://spinoff.nasa.gov/Spinoff2010/ps_5.html https://spinoff.nasa.gov/Spinoff2010/ps_5.html
- eternauta3k 3y agoRe: wind, at what frequencies would it be ok to put them in a box / tent?
- MagicMoonlight 3y agoThat makes way more sense than using it somewhere fragile like space. You could have an emergency antenna on life rafts that suddenly inflates to a full size beacon.
- tigershark 3y agoI don’t think that the explanation is entirely correct. Inflating a balloon will produce a spherical antenna not a parabolic one. Now I don’t really remember the implication of using a spherical receiver for radio waves, but in case of light waves it’s necessary to use a parabolic reflector instead of a spherical one to avoid spherical aberration.
- satori99 3y agoIn this case, the spherical shape is an advantage. See uoaei's post (above); https://news.ycombinator.com/item?id=38043955#38045556 https://news.ycombinator.com/item?id=38043955#38045556
- mahazrasheed26 3y ago[dead]
- h2odragon 3y agoLooks to be something easy to experiment with at home. Heat welding vinyl isn't horribly difficult or risky. use copper tape to form your antenna elements. Complicated 3d shapes that can be collapsed and reinflated should be doable. Durability might be a concern but there's a lot of prior art in marine applications to observe.
- mlsu 3y agoThe idea is that these would point to space, right? I wonder if you could create a ground antenna as well, with a pair of these -- one acting as receiver and the other as transmitter, at a very high altitude, pointed at two different locations on the ground. That would give you a very high gain antenna for two fixed points which might obviate the need for e.g. expensive undersea cable link.
- danboarder 3y agoI thought of using a similar technique to build low cost concentrated solar arrays with a pump that adjusts the air pressure within to automatically focus and optimize the incoming light onto the CSP hot end.
- teo_zero 3y agoThe keyword here is "focus": a spherical surface like this does not focus sun rays, you need a parabolic surface for that. While it would be possible to shape a film or another foldable material into a parabolic profile playing with air pressure and a specially crafted frame, I wonder what would be the advantage over a rigid parabolic mirror. The foldable/inflatable part is only an advantage for aerospace applications where size and weight are at premium.
- eternauta3k 3y agoA balloon is not necessarily spherical, see e.g. the long balloons for making balloon animals.
- greesil 3y agoInflatables are nothing new, but still awesome. https://en.m.wikipedia.org/wiki/Inflatable_Antenna_Experiment https://en.m.wikipedia.org/wiki/Inflatable_Antenna_Experimen...
- brucethemoose2 3y agoBalloons In Space are a good idea, and an antenna is not the only concept they've been proposed for: https://www.projectrho.com/public_html/rocket/infrastructure.php#id--Solar_Power_Stations https://www.projectrho.com/public_html/rocket/infrastructure... https://www.projectrho.com/public_html/rocket/enginelist.php#solarmoth https://www.projectrho.com/public_html/rocket/enginelist.php... Even at large volumes, you get a ton of surface area for the mass, as well as a good spherical or parabolic shape for reflectors.
- incompatible 3y ago“At first, I was afraid to share the idea with colleagues because it sounded so crazy. You need a program within NASA that will actually look at the radical ideas, and NIAC is it.” It doesn't seem like an even slightly crazy idea to me.
- mannykannot 3y agoI am pretty sure that something like this was conceived of by David E. H. Jones, under the pen name Daedalus, for one of his tongue-in-cheek columns in either New Scientist or Nature. IIRC, the scheme, for creating a large space telescope in situ, went something like this: 1) create a flat film of some uncured polymer resin, polymer solution or heat-softened plastic on a large ring; 2) inflate it into a hemispherical dome by applying moderate gas pressure on one side; 3) allow the material to harden; 4) release the pressure, which will cause the bubble to adopt a parabolic shape; 5) use ion beam deposition to apply a reflective surface. I can't say whether my recollection of the geometrical claim on which this proposal is based is accurate, or, if so, whether it is correct. Most of Jones's proposals were wildly yet entertainingly infeasible, but not always, and he is somewhat well known for conceiving of a form of 3-D printing (using a laser-polymerized monomer) before any serious proposals for the concept. There are a couple of collections of his Daedalus columns. https://en.wikipedia.org/wiki/David_E._H._Jones https://en.wikipedia.org/wiki/David_E._H._Jones
- Wingman4l7 3y agoThere's also the old concept of spun liquid mirrors, (1994, Amateur Scientist column of Scientific American): https://optica.machorro.net/Optica/SciAm/LiquidMirror/1994-02-body.html https://optica.machorro.net/Optica/SciAm/LiquidMirror/1994-0...
- LanzVonL 3y agoThis is an incredible idea actually.
- myself248 3y agoThis was in my browser history from earlier this year: https://gizmodo.com/upcoming-cubesat-feature-inflatable-beachball-antenna-1850197655 https://gizmodo.com/upcoming-cubesat-feature-inflatable-beac... The military has used them for years on the ground, evidently this is also a nasa spinoff: https://spinoff.nasa.gov/Spinoff2010/ps_5.html https://spinoff.nasa.gov/Spinoff2010/ps_5.html I see the used ones for sale at ham radio flea markets sometimes.
- prvc 3y agoI assume this is based on a spherical cap's being "close enough" to a paraboloid, for the purposes of this design.
- asimpleusecase 3y agoWhen I was a child , so a long time ago, at the Huntsville ( huntsville alabama )Space Museum they had a demo that was something that looked like a pie pan that was 10 feet across with Mylar stretched across it. And a tripod that was attached at the edge and stood over it. At the top there was a cone of metal and inside the cone was a copper tube that ran up one of the tripod legs and spiralled around the inside of the cone then ran down one of the other legs. They had a household vacuum cleaner attached to a tube at the bottom of the pie pan. When the turned on the vacuum the Mylar got sucked down and it made a parabolic surface. The sunshine was then focused into the cone and the turned on the water and it ran through the copper tube . It came out a stream of water for a few minutes but then turned to steam. Always loved that contraption.
- Intralexical 3y agoReminds me of liquid-mirrored telescopes: https://en.wikipedia.org/wiki/Large_Zenith_Telescope https://en.wikipedia.org/wiki/Large_Zenith_Telescope
- tda 3y agoThe article really could use a picture. If I understand correctly you can get a parabolic shape if you have a stretchy film over ring and apply a pressure differential. The spherical balloon functions as the support ring for an internal reflective third layer. If both halves of the balloon are inflated to equal pressure the reflective layer is flat, but by changing the pressure in both halves the layer takes on a parabolic shape.
- eternauta3k 3y agoAs far as I understood, it's just a balloon with a reflective coating from the north pole down to some latitude.
- peter_d_sherman 3y agoInteresting article! >"Now, with an assist from NASA’s Innovative Advanced Concepts (NIAC) program, funded by the agency’s Space Technology Mission Directorate, which supports visionary innovations from diverse sources, Walker’s decades-old vision is coming to fruition." Didn't know about NIAC before reading this. It sounds like a great group of people! https://en.wikipedia.org/wiki/NASA_Institute_for_Advanced_Concepts https://en.wikipedia.org/wiki/NASA_Institute_for_Advanced_Co...
- eternauta3k 3y agoI don't understand why the article and everyone here are talking about spheres. Balloons come in all possible shapes, and in fact the most common birthday balloons are not spherical. Can't they engineer a balloon which has a parabolic surface when inflated?
- dathos 3y agoI think that requires a lot more pieces and engineering in order to work properly
- eternauta3k 3y agoWhat do you mean? We can make party balloons and long balloons for balloon animals without any additional pieces.
- MagicMoonlight 3y agoI’d be concerned that the balloon would pop the moment it comes across some rock or dust. Using a huge balloon to make the shape and then covering it in a material in space could be an idea. Get the ISS crew to build a mega telescope in orbit.
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- denton-scratch 3y ago> it inflates like a beachball, providing a stable parabolic-dish shape Except the surface of a beachball is spherical, not parabolic. A parabolic surface is not closed, so you can't inflate it like a beachball. So I'd like to know either: how they control the shape of the surface, so the mirrored portion is parabolic; or whether the antenna surface is actually spherical, and not parabolic at all. The portion of a parabolic mirror nearest the focus approximates to a sphere. If the deviation is less than 1/4 wavelength of the signal of interest, a spherical mirror will focus the signal perfectly, as if it were a paraboloid. A paraboloid is what you need for distortion-free imaging; this antenna is apparently used only for signalling, so perhaps accuracy doesn't matter, because only the gain is important. But this is a NASA publication, so I wouldn't expect them to say it's parabolic if it's really spherical.
- fgeiger 3y agoMaybe I misunderstand your point of spherical vs parabolic, but doesn't this paragraph explain it? > The concept turns part of the inside surface of an inflated sphere into a parabolic antenna. A section comprising about a third of the balloon’s interior surface is aluminized, giving it reflective properties. The balloon is approximately spherical but probably not exactly (actually, when looking closely, hardly any beachballs are spherical either). What is parabolic is the part of the balloon which is aluminized. Edit: fixed a typo
- denton-scratch 3y agoYeah; I was wondering how they get the mirrored part of the balloon to take on a parabolic shape, rather than spherical; is that done by manipulating the balloon material somehow? Or are they settling for spherical as a good-enough approximation?
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- persnickety 3y agoThis references the problem, but doesn't explain the big question: how do they turn a section of a sphere into a section of a parabola? Beach balls might not be spherical, but my bet would be on ovoid rather than parabolic.
- Daub 3y agoFrom TFA: > Some 30 years ago, a young engineer named Christopher Walker was home in the evening making chocolate pudding when he got what turned out to be a very serendipitous call from his mother. > Taking the call, he shut off the stove and stretched plastic wrap over the pot to keep the pudding fresh. By the time he returned, the cooling air in the pot had drawn the wrap into a concave shape, and in that warped plastic, he saw something – the magnified reflection of an overhead lightbulb – that gave him an idea that could revolutionize space-based sensing and communications. I love genesis stories like this. Reminds me of Feynman's plate: https://demonstrations.wolfram.com/FeynmansWobblingPlate/ https://demonstrations.wolfram.com/FeynmansWobblingPlate/
- blackhaz 3y agoBy the way, inflatable parabolic SATCOM antennas have been sold by a company called GATR for at least 10 years: https://www.militaryaerospace.com/rf-analog/article/16715763/army-looks-to-gatr-for-lightweight-quicksetup-inflatable-satcom-antennas https://www.militaryaerospace.com/rf-analog/article/16715763...
- whycome 3y agoReminds me of the idea of hiding satellite dishes in false water tanks that allow the transmission of whatever freq of radio wave.