Hanging-Parafoil Dynamic-Ballast Blimp!

December 21, 2008

(This posting was followed up in a more analytical way here.)

Here’s a blimp that can put down a payload in a remote place.

This is actually a big deal.  A conventional blimp can carry a heavy load much more fuel-efficiently than an airplane or helicopter, sure, but can’t put it down!

When the weight of the payload is lost, a regular blimp suddenly has too much lift and can’t land!  Dangit!

The only two (believable) solutions to this problem so far even suggested, as far as I know, are to either 1) Just release some expensive lifting gas into the atmosphere, or 2) Trade the payload for something equally heavy like water pumped up from waiting tanker trucks.

Both solutions #1 and #2 above stink.

#1, venting lifting gas, stinks because lifting gas (helium or hydrogen) isn’t cheap.  If I want to put down a nine-pound gallon of diesel fuel at a diamond mine in northern Canada, but also have to vent four or five dollars’ worth of lifting gas in the process, then that diesel just got really expensive!

#2, trading the payload for water pumped up from below, sucks because not only must there be water trucks handy, but they must be able to get to the drop site. If a truck can get there then what’s the blimp for?

So!  Here’s my solution #3:

Right before dropping its payload, the blimp deploys these hanging parafoils (like the wings of paragliders, but hanging upside-down) and gooses the engines to start moving through the air.  The hanging parafoils generate aerodynamic down-force (like aerodynamic lift but in the downward direction) to compensate for the payload’s lost weight!

The key complication to this scheme, then, is that in order to be able to stop again — which has to happen eventually, namely back at the logistics base where the mission started — the blimp needs to lose lift and/or gain weight, so that the parafols won’t be needed anymore and can be winched back up against the blimp’s envelope.

Lift can be lost in a productive way by having all or some of the lifting gas be CH4, aka methane, aka natural gas, and just burning it up as fuel (‘cuz ‘gotta burn something, and CH4, if it’s available, is always cheaper than diesel fuel anyway).  Further, water vapor in the engines’ exhaust can be condensed to liquid water and retained in tanks, thus doubling the lift-losing/weight-gaining effect.

(The same scheme works if the lifting gas being burned up as fuel is just hydrogen.  You just need the extra machinery at the base to make that hydrogen gas in the first place plus engines that can burn it safely, a perfectly doable but not-so-off-the-shelf sort of thing.  What’s nice about hydrogen, though, is that not only does it lift twice as much as CH4 per volume, but gives about a quarter as much fuel energy per volume too.  Ergo, burning hydrogen gas instead of CH4 lets us lose-lift/gain-weight about 4X as quickly!)

Another way to gain weight is to fly over a body of water at any point along the way back and scoop up water through a special boom.  Here’s a video demo of a helicopter doing this.

And there we have it: A blimp (with some physical and procedural complexities stapled on) that actually can put something down in a remote place in a controlled, cost-efficient and non-catastrophic way!  This could be a big deal in the oil/gas exploration, military logistics and/or emergency humanitarian aid businesses (and/or the other fields that you can help me brainstorm here).

A final interesting tidbit is that since it’s so advantageous to be able to scoop up water on the way back to base, it’s an interesting idea to have that base be a ship.  That’s pretty interesting, becauase now you’re doing heavy deliveries in-country directly from a ship, without having to deal with the roadblocks, washouts, mudslides, theft, spoilage or bribe-seeking customs goons on land!  Awesome!

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6 Responses to “Hanging-Parafoil Dynamic-Ballast Blimp!”


  1. Hello! It’s 21 December (Happy Winter Solstice or Christmas or Whatever!) I get Google Alerts on blimps and airships..yours was in this mornings lot. I decided to have a look, because the word “parafoil” reminded me of an airship design that I had looked at recently; and thought that someone might be commenting on it. Nope. Turned out to be your own production about your own idea.

    First, Bravo! Well thought out and do-able.
    Second……I’ve been setting up to make a similar video of my own….using a whiteboard and dry erase markers and a vid camera….and considered using a digital camera and making a bunch of stills in order to make an annimation…………..so, seeing your own drawings and etc. was a kick!

    Haven’t made up a little video like yours yet; loved seeing your work.
    And very pleased to encounter a note about how you made em up.
    (ever see this?…..look up “PR solar toaster” on YouTube. That is where I was coming from.

    “downward force” dyanamic lift from parafoils…???? Neat idea!

    I’m Darrell Campbell
    http://www.turtleairships.blogspot.com

  2. Matt Brubeck Says:

    “The hanging parafoils generate aerodynamic down-force (like aerodynamic lift but in the downward direction) to compensate for the payload’s lost weight!”

    So the parafoils convert forward thrust (from the engines) to downward “lift”, right? Why is this more efficient than just generating downard force from the engines directly (e.g. using turbines blowing upward).

    The downward force of the parafoils has to equal the lift of the envelope – which in turn has to equal the weight of the cargo. So while the airship is using its “dynamic ballast” it must be generating the same amount of thrust as a heavier-than-air plane with the same cargo capacity. Is this practical? It certainly means that you don’t get any efficiency benefits from lighter-than-air transport during the dynamic ballast portion of the trip.

    “A final interesting tidbit is that since it’s so advantageous to be able to scoop up water on the way back to base, it’s an interesting idea to have that base be a ship.”

    Or a seastead! 🙂

  3. craigrmeyer Says:

    > So the parafoils convert forward thrust (from the engines) to downward
    > “lift”, right? Why is this more efficient than just generating downward
    > force from the engines directly (e.g. using turbines blowing upward).

    Well, for the very same reason that an airplane is more fuel-efficient than a helicopter is. It’s always better to use propellers to generate a horizontal force and let wings “convert” horizontal motion to a vertical force.

    A large parafoil wing has a lift:drag ratio of about 10:1 (which is much crappier than a metal wing at 20:1 or even 30:1). Ergo, just 1 newton of forward thrust can generate 10 newtons of vertical force.

    > So while the airship is using its “dynamic ballast” it must be generating
    > the same amount of thrust as a heavier-than-air plane with the same
    > cargo capacity.

    Yes, that’s exactly right. When the parafoils are out in the “dynamic lift” portion of the flight, the system drag is much higher than otherwise, to the point of the system being draggier than a regular airplane (but still better than a helicopter).

    This means lots of things. For one, it means that the required horsepower (= fuel burn rate) goes way up when the parafoils are out.

    So it’s important fuel-efficiency-wise to get those parafoils back up and out of the way as soon as possible.

    In fact, to show better respect for this fact, I’m looking at an addendum to this posting that’s about dropping the water-scooping idea and using hydrogen instead of CH4:

    Hydrogen lifts twice as much weight per volume as CH4 does, while its fuel energy per volume is about 75% LESS. That’s actually good in this weird case because if the propulsion engines are stuck burning hydrogen instead of methane, they’ll have to blow through four times as much fuel volume per second for the same horsepower. Since each of those unit volumes of hydrogen lifts twice as much as a unit volume methane, the hydrogen-burning engines are actually blowing through EIGHT TIMES as much “lift’s worth” of gas as methane-burning engines would.

    Ergo, the hydrogen-burning craft would return to neutral buoyancy (== not needing the parafoils anymore and allowing them to be winched back up and out of the airstream) that much quicker. I suspect this will end up being the winner.

  4. craigrmeyer Says:

    (And thank you for the comment, Matt. It shows that you were really paying attention, which is flattering. 😉


  5. […] Parafoil Dynamic-Ballast Blimp; take 2 By craigrmeyer (This is a next-level follow-up to a previous posting.) […]


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