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Power United Kingdom Science Technology

Scientists Develop Self-Propelling Phoenix Aircraft That Inhales Air (bbc.com) 90

dryriver writes: The BBC reports on a 50ft long and only 120kg heavy blimp-like UAV aircraft that is designed to fly at 70,000 feet, is entirely solar powered, uses variable-buoyancy for propulsion, and can essentially stay airborne in a self-powered way until it experiences mechanical or electrical failure. The Phoenix varies its buoyancy continuously using a helium-filled fuselage that also has an interior air sack that works a bit like a lung. It can inhale air and compress it on demand, making the aircraft temporarily heavier than air, and expel the inhaled air through a nozzle at the back of the aircraft, making the aircraft lighter than air again, creating some extra forward propulsion in the process.

The Phoenix -- which is a simple, cheap-to-build aircraft that its designers describe as "almost a disposable aircraft" -- could one day act as a satellite replacement flying at 70,000 feet. It may also be used for surveillance purposes or to release micro-satellites into earth orbit. The Phoenix has already completed short test-flights of 120m inside the hangar it was built in. This YouTube video shows just how gently the Phoenix rises into the air, hovers in place, and lands again. Unlike drones that need to land, refuel and then take to the skies again, the Phoenix may stay in the air for very long periods of time, landing only for periodic maintenance of its electrical and mechanical components.

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Scientists Develop Self-Propelling Phoenix Aircraft That Inhales Air

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  • Time fore some more Digital Receiver Technology?
    https://theintercept.com/2017/... [theintercept.com]
  • by mentil ( 1748130 ) on Wednesday April 24, 2019 @02:16AM (#58481394)

    Who names a blimp a 'phoenix'? Oh, the humanity!
    At least it uses helium. I'm wondering how fast it can propel itself, though.

    • Simple: It's shaped like a huge manatee.

    • OK, yes, there were a couple of "burning" problems with earlier blimps, but we're at least reasonably sure that we solved those.
      • OK, yes, there were a couple of "burning" problems with earlier blimps, but we're at least reasonably sure that we solved those.

        The Hindenburg was actually a dirigible (rigid interior frame) not a blimp, but the German's bad engineering with regard to static control and choice of flammable materials contributed a lot to the disaster, as well as the use of hydrogen.

  • sorry, could not resist...

  • The article does not say why its variable-buoyancy propulsion mechanism is better than regular electric fans.
    • Re: (Score:3, Informative)

      by Solandri ( 704621 )
      It's used as propulsion for long-duration underwater missions [wikipedia.org]. The power requirements are minuscule (energy = pressure * volume change). You alter the buoyancy slightly so the vehicle barely starts to sink, and rely on a wing to convert that downward motion into forward motion. Then when you get close to the bottom you alter the buoyancy again so the vehicle barely starts to float. The wing again converts that upward motion into forward motion. Combine this with electronics which go into a sleep state
      • by fgouget ( 925644 )
        That makes sense. I think the Slashdot summary misled me into thinking the main source of propulsion was the air expelled from the rear of the aircraft:

        and expel the inhaled air through a nozzle at the back of the aircraft, making the aircraft lighter than air again, creating some extra forward propulsion in the process.

        They probably minimize the buoyancy changes to minimize energy expenditure which means expelling relatively little air from the rear so it probably does not contribute significantly to the propulsion.

      • by Ranbot ( 2648297 )

        Great explanation... BBC should have consulted you.

        I wonder what the max payload of these blimps would be... and would payloads scale up economically with larger blimps? I feel like that would be a basic question anyone looking to deploy sensors or communications would need to know. The article says they have to scale up to reach the desired altitudes, but says nothing specific about payload weight/size.

    • by ceoyoyo ( 59147 )

      It's basically the same reason why airplanes are more efficient than helicopters.

      Airplanes use a bit of power to drive themselves forwards, but rely on a wing to provide lift to keep them up. The wing is more efficient at generating lift than a downward-directed fan/prop/rocket/whatever.

      A buoyancy glider uses the same principle flipped: it generates lift (or sink) and uses a wing to translate that into forward thrust. Again, the large fixed wing is more efficient than the small spinning ones.

  • Not Orbit (Score:3, Informative)

    by Gavagai80 ( 1275204 ) on Wednesday April 24, 2019 @03:56AM (#58481612) Homepage

    "It may also be used for surveillance purposes or to release micro-satellites into earth orbit."

    ^ The article directly contradicts this summary claim. There are no plans to accelerate this thing to orbital velocity, which is about 30 km/s and would be absurd to expect from this. The claim of the designers is that it's an alternative to going to orbit. Perhaps it can achieve the goals of some subset of microsatellites so that they don't have to go to orbit.

    • by Ozoner ( 1406169 )

      The article stated that the micro-sats would be released at a high altitude, where they would accelerate to orbit.

      Clearly the micro-sats would need their own propulsion, but that would be much less that would be required from ground level.

      • Re:Not Orbit (Score:5, Informative)

        by necro81 ( 917438 ) on Wednesday April 24, 2019 @07:30AM (#58482222) Journal

        Clearly the micro-sats would need their own propulsion, but that would be much less that would be required from ground level.

        That is a common misconception: that once you get to high altitude, you are practically in orbit. Being in orbit requires velocity, and velocity requires a huge energy input - much more than just getting up to 10s of kilometers of elevation.

        A different slashdot commenter has summed it up as the 6-6-6 rule [slashdot.org]: Mach 6 at 60,000 ft altitude is a whopping 6% of the way to orbit.

        Let's say you are aiming for low earth orbit: altitude 300 km and velocity about 7.72 km/sec. The potential energy for reaching orbital altitude is approximately m * g * h, or mass * 3e6 [J/kg]. The kinetic energy is 1/2 * m * v^2, or approximately mass * 3e7 [J/kg]. In other words, you have to put in 10x as much energy getting the object up to orbit velocity as you do in raising it to orbit altitude.

        • by ceoyoyo ( 59147 )

          This is also a common misconception. You can't analyze rockets by computing kinetic energy. You must compute delta-v. For launching, there are also gravity and aerodynamic losses.

          Accelerating *up* is considerably harder than accelerating in other directions, if that acceleration is applied over some significant period of time. And trimming off a few percent of the *final* energy required can translate to a lot more of the *total* energy required, due to the nonlinearities in the rocket equation. It's like b

          • by necro81 ( 917438 )

            Accelerating *up* is considerably harder than accelerating in other directions, if that acceleration is applied over some significant period of time. And trimming off a few percent of the *final* energy required can translate to a lot more of the *total* energy required, due to the nonlinearities in the rocket equation

            That may be true, but you haven't actually put numbers to it. How much do you save by first lofting your rocket to 60,000 ft altitude? Or: but differently, how much more payload can you pu

            • by ceoyoyo ( 59147 )

              It's an interesting exercise to work the whole thing out. I've got a stuff to do today, unfortunately. But as a rough indication, you can look at the impulse provided by each stage in a Falcon 9.

              First stage: 7607 kN for 162 s = 1,232 MNs
              Second stage: 934 kN for 397 s = 371 MNs

              The first stage is also about four times the mass of the second stage as well. You certainly couldn't replace the whole first stage with an air launch system, especially a stationary one like a blimp, but it does illustrate that delta

    • Earth orbits the Sun at 30 km/s, but the required velocity to orbit the Earth is "merely" 7.8 km/s. Otherwise, yes, you are correct that merely reaching a high altitude is not anywhere close to orbital velocity.
  • by tinkerton ( 199273 ) on Wednesday April 24, 2019 @04:37AM (#58481714)

    So, has it been weaponized yet?

  • It's an old idea, but they could have a way to change the outside surface between black and white, to absorb more or less sun heat, to alter the temperature and the density of the lifting gas. It might be more efficient than compression.

    Buckminster Fuller gave us Cloud Nine: city-sized tensegrity spheres. https://en.wikipedia.org/wiki/... [wikipedia.org]

  • ...Bill Clinton [azquotes.com] quote.
  • Self propelling, inhales air, so like a jet engine then?
    • by AmiMoJo ( 196126 )

      Nothing like a jet engine. A jet engine requires fuel for a start.

      This is basically a blimp, but with a solar powered pump to suck in or expel air and thus vary its mass. Heavier than air and it descends, lighter than air and it ascends.

      The expelled air also provides a little bit of propulsion, but the main way of getting around will be like a hot air balloon. Move to an altitude where the wind is going the same way you want to go.

      • Yeah I get that. I did actually rtfa but still, a jet engine propels itself and it inhales a whole lot of air. Doesn't say anything about not needing anything else lol.
      • Actually, this is not how it moves, at least primarily. FTFA it is variable buoyancy. When it's lighter than air, it glides up and when it's heavier than air it glides down. No doubt expelling air would give it some push but it's not its primary propulsion.
    • This thing seems more like the long-range autonomous vehicles [wikipedia.org] being used for ocean research. They propel themselves forward by gliding up and down through the water using a similar variable buoyancy technique.
  • Unless it's on the cover of Popular Mechanics then I don't believe it exists.
  • Hopefully Pepsi doesn't know about this.
  • by Applehu Akbar ( 2968043 ) on Wednesday April 24, 2019 @08:45AM (#58482552)

    In this unmanned application, why the need to use increasingly scarce helium? Hydrogen is cheaper and would work even better.

    Of courage, you wouldn’t want to call it the Phoenix if it used hydrogen.

  • Phoenix is an unmanned aerial vehicle (UAV) designed to stay in the air indefinitely using a new type of propulsion.

    Actually, variable-buoyancy propulsion is a very old type of propulsion. Solomon Andrews' [wikipedia.org] "Aereon" airship used it in the 1860s.

  • Umm .... like any aircraft it "... can essentially stay airborne in a self-powered way until it experiences mechanical or electrical failure. "

    Not sure what there is to see here.

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