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MIT's Inflatable Antennae Could Boost Small Satellite Communications

Posted by timothy on from the very-interesting-and-growing-rapidly-again dept.

coondoggie writes "Researchers at the Massachusetts's Institute of technology say they have developed an antenna for small satellites (known as cubesats) that can fold into a compact space and inflate when in orbit. The inflatable antenna lets a CubeSat transmit data back to Earth at a distance seven times farther than that of existing CubeSat communications."

52 comments

  1. Laser by symbolset · · Score: 1

    Can't they get the signal lasers working? Much better for max signal strength, bandwidth, power usage and transmitter size.

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    1. Re:Laser by Jane+Q.+Public · · Score: 4, Informative

      "Can't they get the signal lasers working? Much better for max signal strength, bandwidth, power usage and transmitter size."

      Signal lasers are WORK and EXPENSE. You have to accurately track your target both for transmission and reception. Far, far more expense than cubesats justify.

      Maybe one day it will be cheap and easy. Not today.

    2. Re:Laser by symbolset · · Score: 0

      With an adjustable lens on your transmitter, no you don't. It is not that hard to widen the beam and use feedback to home in on the target and improve the focus until you have a nice strong signal and then ramp the bandwidth. And the parts for this are truly tiny. Compared to an inflatable balloon in space? No contest.

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    3. Re:Laser by Anonymous Coward · · Score: 1

      With an adjustable lens on your transmitter, no you don't. It is not that hard to widen the beam and use feedback to home in on the target and improve the focus until you have a nice strong signal and then ramp the bandwidth. And the parts for this are truly tiny. Compared to an inflatable balloon in space? No contest.

      So much cluelessness in just 5 sentences. Impressive.

    4. Re:Laser by Jane+Q.+Public · · Score: 4, Informative

      Huh? No, I'm not the one who is wrong here.

      The more focused your "lens", the tighter your aim must be. And my whole point was the expense of accurate aiming equipment.

      Fine, use a parabolic dish for your RADIO. But a pinpoint laser, today, is about the LEAST cost-effective solution you could come up with for cheap satellites.

      Don't take my word for it. Try it.

    5. Re:Laser by Jane+Q.+Public · · Score: 1

      Just to be clear: I didn't miss your point. I understand that focusable, aimable systems can do the job. Far more so than they could have, say, 10 years ago.

      But they STILL can't do it as simply or cheaply as a basic parabolic antenna.

    6. Re:Laser by notKevinJohn · · Score: 2

      The problem with that is cubesats get launched piggy-backed on Air Force satellites; and they can't give you particularly accurate orbital dynamics. It's hard enough to get a signal using the 433 Mhz band where you really only have to know the position of the cubesat to within a few degrees. To use a laser for communication, you would have to know the position to within a tiny fraction of an arc-second.

    7. Re:Laser by AHuxley · · Score: 1

      Signal lasers for special forces on the ground dragging power with them trying to aim up at something at a set time?

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    8. Re:Laser by Anonymous Coward · · Score: 0

      Space Comm engineer here... Not really.
      A bunch of factors are at play:
      1) electrical power to "radiated signal" conversion efficiency can be higher with RF than lasers, at least with current technology. There are efficient lasers to drive optical fibers, but they're not well adapted to radiating in free space (from an optical standpoint)
      2) In order to do any sort of "seeking" you need to have a way to know the direction of the incoming signal. The atmosphere makes interferometric approaches difficult (the phase front isn't flat), so you have to rely on other schemes. None are simple, none work well in low power situations. A "fairly well solved" problem for apertures in the 30cm to 1 meter range, but that's not really cubesat compatible, is it?
      3) on the receive side, the quantum efficiency of optical detectors is low, so the conversion of "received signal energy" into "something we can decide whether it's a one/zero in the presence of noise" is not favorable for optical.
      4) Enormously higher risk for optical. Radio communications for space is a basically solved problem (left as an exercise for the student): thousands of spacecraft have used radios; very, very few have used optical, and none for primary command/telemetry. You're a scientist wanting to do measurements or something in space. Do you want to spend your budget thrashing with optical comm, or working on your science? (unless your experiment *is* optical comm, then more power to you, literally).

      Optical comm is a great idea for very high data rates, but basic physics means that you need more energy to send those bits (can't beat the "joules per bit" vs "joules of noise"), no matter what frequency you use. So, that means that optical is "useful" for spacecraft with lots of energy, which is generally NOT the case for a cube sat.

    9. Re:Laser by symbolset · · Score: 1

      So no, they haven't solved this problem yet. Thanks. I see now that they are starting to work on it. It really is not as difficult as you make it out to be so it should not take them long.

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    10. Re:Laser by bmo · · Score: 1

      Can't they get the signal lasers working?

      There's this thing called weather. Perhaps you've heard of it.

      The problem with lasers is that they do not penetrate clouds at all.

      Clouds take lasers and other light beams and spread them out into nothing in only a few feet. That's because they're composed of a bunch of little prisms - water droplets. As a land survey technician, I couldn't get a beam bounce from a retroreflector during a fog even if I could still see it myself 20 feet away.

      --
      BMO

    11. Re:Laser by Anonymous Coward · · Score: 0

      The whole point of laser based communication is to use less power for a given bandwidth. This doesn't work in all situations, as there are certain fixed costs and minimum practical sizes (but much smaller than a 30 cm aperture on spacecraft), so it isn't really appropriate for the cheap and very small end of the spectrum. Why the efficiency is crap for generating the light, the point is to aim it in a much narrower beam that more than makes up for the efficiency issues. And coupling from a fiber to free space is not the bottle neck in the efficiency in such a system.

      Laser communication is supposed to be cheaper and lower power, but it just doesn't scale down perfectly to something the size of a cubesat, or to the lower power end. If you don't need the extra bandwidth, then there is not much motivation to bother at the low end.

    12. Re:Laser by Anonymous Coward · · Score: 0

      Rain, and clouds to a lesser extent, can have some pretty serious impacts on microwave bands used for satellite communication too. It is less than the impact on most visible and IR, but still an issue.

    13. Re:Laser by ChrisMaple · · Score: 1

      Laser beams can be arbitrarily expanded, cheaply and easily. The disadvantages of laser space communication are elsewhere, including blockage by clouds.

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    14. Re:Laser by bmo · · Score: 1

      Yeah, snow can have an effect when you have to go out and shovel out the C-band dish because the snow is half melted and the water is causing a flat spot in the nice parabola.

      This one.

      http://i.imgur.com/qg9KGAm.jpg

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      BMO

    15. Re:Laser by Anonymous Coward · · Score: 0

      Yes, if everyone was fortunate enough to be using a slice in the c-band, instead of a higher band, and be communicating with a satellite directly over head, and have a setup that doesn't care about a couple dB loss or care about the uplink channel as much as the downlink.

  2. Inflatable Antenna? by jcr · · Score: 1

    What, like this product that's been on the market for about a decade or so?

    -jcr

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    1. Re:Inflatable Antenna? by Anonymous Coward · · Score: 1

      Bad summary, it's the inflation system that's unique.

    2. Re:Inflatable Antenna? by notKevinJohn · · Score: 1

      Maybe, but since cubesats are only 10cm x 10cm it needs to be a LOT smaller.

    3. Re:Inflatable Antenna? by AHuxley · · Score: 1

      The idea could be to replace a few stealthy or known overloaded platforms with trackable orbits just before action against a real enemy with a hint of having anti-satellite weapons.
      Dont bet all on the super expensive stealthy "one" that teams of amateurs blog about.
      Flood the short term war zone with cheap new sats and enjoy the high ground for a bit longer.

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    4. Re:Inflatable Antenna? by Anonymous Coward · · Score: 0

      It is designed for a 3U CubeSat , 10 cm x 10cm x 30 cm , so it works

  3. ENLARGE YOUR ANTENNA by toygeek · · Score: 5, Funny

    New research from MIT scientists shows that you can MAKE YOUR ANTENNA BIGGER! Try our fast safe ANTENNA ENLARGEMENT powder!

    - Convenient!
    - Inexpensive!
    - MORE POWERFUL EMISSIONS!
    - Bigger girth!
    - More Gain!
    - Long Lasting!

    Guaranteed satisfaction, for you AND for her(tz)!

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    1. Re:ENLARGE YOUR ANTENNA by lawnboy5-O · · Score: 1

      Can you put your weed in there?

    2. Re:ENLARGE YOUR ANTENNA by Anonymous Coward · · Score: 0

      You ever think maybe that stuff's illegal for a good reason?

      We also have mod points for a good reason, do downvote people like you.

    3. Re:ENLARGE YOUR ANTENNA by Anonymous Coward · · Score: 0

      MIT's Inflatable Girlfriend Could Boost Small Penis's Activity

    4. Re:ENLARGE YOUR ANTENNA by beelsebob · · Score: 1

      No. Studies that actually score the damage these things do consistently put Canabis very low down the list. Generally far below Alcohol and even Nicotine. The reason it's illegal is purely political.

    5. Re:ENLARGE YOUR ANTENNA by Anonymous Coward · · Score: 0

      You joke, but there were a couple years in the 2000-2005 time period where I got spam for lab equipment themed like this. Maybe it was cute the first time as a joke to get attention, but after a year of it, it blended in with the real enlargement spam. Great marketing campaign where you try to make your emails look more like spam...

    6. Re:ENLARGE YOUR ANTENNA by Anonymous Coward · · Score: 0

      Can you put your weed in there?

      You ever think maybe that stuff's illegal for a good reason?

      Bahahahahahahahahahaha...

      BAHAHAHAHAHAHAHAHAHAHAHA!!!!

      Going to war without justification is illegal too. You wanna start discussing how the very assholes keeping weed illegal are making a mockery of every other fucking law, including the very document put in place to prevent such abuse, or perhaps we should talk about the fact that the very document I speak of is printed on hemp paper, which is the real reason hemp (and cannabis) were outlawed.

      Those that pretend to know why marijuana is illegal today are coming across far more stupid than any Hollywood director could ever portray a stoner.

      Wise up and get your facts straight. Oh, and you might want to put down that beer while you do, hypocrite.

    7. Re:ENLARGE YOUR ANTENNA by ai4px · · Score: 1

      Maybe they just need one of those cell phone antenna booster stickers?

  4. Inflatable? by MobSwatter · · Score: 0

    Maybe until a micro meteor flies through it, lets talk about real world solutions.

    1. Re:Inflatable? by notKevinJohn · · Score: 2

      First line of the article: "Mylar-based attennae could inflate once launched, withstand micro-meteor threat, MIT says."

    2. Re:Inflatable? by khallow · · Score: 4, Informative

      Article says it can take a number of micrometeor impacts and still stay inflated. I buy that claim. It doesn't take a lot of gas pressure to inflate a piece of mylar and they have a good mechanism for maintaining that modest gas pressure (via sublimation of a particular powdered chemical) even in the presence of a bunch of micrometeor holes (low pressure gas doesn't leak out very quickly).

      OTOH, they might have a problem controlling inflation of the antenna in the first place. The sublimation triggers in the presence of vacuum. And they'll have that condition before the cubesat leaves the payload shroud.

    3. Re:Inflatable? by Anonymous Coward · · Score: 0

      OTOH, they might have a problem controlling inflation of the antenna in the first place. The sublimation triggers in the presence of vacuum. And they'll have that condition before the cubesat leaves the payload shroud.

      Maybe the sublimation is a very slow process, in the range of hours, days, so it will take a while to complete, and they would not need to worry about that. But if it is a fast one(seconds,minutes), then they should be worried.

    4. Re:Inflatable? by MobSwatter · · Score: 1

      Mylar has gone a long way to being shatter proof, however seeing small object traveling at say around 25 miles per second, I just don't see it resistant to that.

    5. Re:Inflatable? by ChrisMaple · · Score: 1

      I find it hard to believe that the system could provide enough gas to keep it inflated for a long time in the presence of even micron-sized holes. I'd be more likely to believe that it would maintain structural integrity if they used a plastic that became stiff when struck by ultraviolet light, or became stiff as a plasticizer outgassed.

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    6. Re:Inflatable? by khallow · · Score: 1

      Well, suppose they have a bag of air attached to equipment that feeds pressurized air so as to maintain the bag at standard temperature and pressure (STP which is 20 C and 1 atmosphere) and the bag is suspended in a vacuum. The speed of sound at that temperature for air (which also is the average velocity of molecules in air) is roughly 340 m/s.

      For a millimeter sized hole leaking into vacuum (let's say that the hole is a square millimeter in area), that means that in the absence of friction and turbulence, roughly 3.4*10^-4 cubic meters of air leak out every second (average velocity of air times the area of the hole(s)). At a density of 1.2 kg per sq meter, that's roughly 4*10-4 kg per second of mass lost through that hole. In other words, a gram of air lost ever 2.5 seconds or so.

      But mass loss is proportional to pressure. If instead, the pressure inside the bag were one ten-thousandth of an atmosphere, then the mass loss is 1 gram every 25,000 seconds, or roughly a gram lost every 7 hours.

      A micron sized hole because it's a million times smaller in area would have a mass loss a millionth the rate of this. So in the one atmosphere case, you'd be losing a gram of air every four weeks, roughly.

      In the absence of perturbations or vibration, such an antenna can hold its shape under extremely low pressures. But I doubt that would be the case for a normal spacecraft. At the least, you'd have perturbations from vehicle maneuvering, temperature changes should the vehicle enter shade (say the Sun is eclipsed by the Earth or Moon in the course of the spacecraft's orbit) or change orientation (different parts of the vehicle are lit means some vibration as parts of the vehicle expand or contract).

      So they have to maintain some level of pressure depending on how much vibration they expect and how long they're willing to wait for the antenna to settled down to a usable level.

  5. Best blow up invention since by maroberts · · Score: 4, Funny

    the autopilot [/airplane]

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  6. My antenna went flat by Tailhook · · Score: 1

    ...and I need to change my blinker fluid, lubricate my muffler bearings and put winter air in my tires before it gets cold.

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    1. Re:My antenna went flat by toygeek · · Score: 1

      Don't forget to check your firewall gasket and the piston return springs!

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  7. It takes more than an antenna... by DerekLyons · · Score: 1

    The bird will need an attitude detection and control system to take advantage of this antenna... decreasing the available weight, volume, and power available for other things. TANSTAAFL.

    1. Re:It takes more than an antenna... by ThreeKelvin · · Score: 1

      Actually, cubesats need at least a simple attitude control system, i.e., detumbling. Without one they spin up. See e.g. AAUSat II:

      We are still working on finding the reason for the fast rotation rate, especially why it accelerated over the course of 40 days. We have a number of ideas, der include the torque caused by the magnetic dipole generated by the solar cells.

      That said, being able to actually point in a specific direction with the sat is quite hard, and a lot of work.

    2. Re:It takes more than an antenna... by braindrainbahrain · · Score: 1

      Indeed. As they get more gain out of this antenna, it has to be pointed with more precision. Being inflatable, if the antenna has any kind of wobble after movement... well that's just one more aggravating detail.

    3. Re:It takes more than an antenna... by DerekLyons · · Score: 1

      Space exploration is nothing if not accounting for one aggravating detail after another...

  8. Illiteracy... by msauve · · Score: 1

    Is MIT an insect with inflatable feelers which somehow assist in satellite communications?

    When referring to a radio antenna the plural is "antennas."

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  9. Reactive chemicals in a cubesat by Anonymous Coward · · Score: 0

    Usually the way to get your cubesat launched into space is to hitch a ride on a commercial rocket, that's going up there anyway.

    Q: Which launch provider is gonna risk damaging the multi-million dollar main payload just because a gang of small-time cubesat boys, who are paying ~$100k, want to use a nifty antenna?

    A: Nobody. That's who!

    1. Re:Reactive chemicals in a cubesat by __aaltlg1547 · · Score: 1

      It doesn't take reactive chemicals. Just seal a small amount of gas in the balloon when it's on Earth, say, less than 1cc of nitrogen. When it gets to space, it will inflate as soon as you let it out of the enclosure.

  10. Say what? by __aaltlg1547 · · Score: 1

    The inflatable antenna lets a CubeSat transmit data back to Earth at a distance seven times farther than that of existing CubeSat communications."

    When are they going to be orbiting cubesats 7x higher than they do now? No, what such an antenna can do is allow you to operate at 50x less transmitter power (or 50x the data rate at the same power). Or receive at 50x the data rate. That's all good. but we won't be sending any cubesats past the moon. Spacecraft designed for high orbits must be designed for long missions, and cubesats are designed for short missions because they must compromise something to make things fit in tiny spaces.

  11. I call bullshit by Anonymous Coward · · Score: 0

    How can something inflate in space we all know their's no air there.

    Yet another waste of money illegally obtained without consent or constitution.

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    roman_mir