20 thoughts on “More On The Giant Airplane”

  1. Did they actually say they’re going to use 747 fuselages or 747-sized fuselages? Big difference.

    While there are a lot of old 747 fuselages available, it seems the amount of reengineering and modification required would be enormous, as would the dead weight. 747s are low wing aircraft. Joining two 747 fuselages and allowing enough ground clearance for the rocket would be a non-trivial engineering exercise. Getting that though FAA certification would also be non-trivial.

    There are likely a lot of 747 components that could be reused on a new vehicle such as the engines and landing gear. If the resulting airplane is to look anything at all like the one shown in the articles, you wouldn’t want 747s.

      1. I didn’t think they said that but here’s what the linked “Popular Mechanics” articles says:

        A fledgling spaceflight company announced today that its hopes to launch rockets into orbit from two fused-together 747 jets before the end of the decade. Called Stratolaunch, and backed by veteran spaceship builder Burt Rutan and Microsoft billionaire Paul Allen, the commercial outfit wants to start by launching small- to medium-sized commercial satellites into orbit from a spaceport in the Mojave Desert. Their sights are set on ferrying humans to orbit by 2020.


        
The yet-to-be-built launch system will actually be made of three vehicles. The two 747s, fused to create a plane with a 385-foot wingspan, will carry a SpaceX rocket between them. It will be a stubbier version of the Falcon 9, which SpaceX has on track to dock with the International Space Station in February 2012.

        That article repeatedly refers to linked 747s which doesn’t make a lot of sense. Probably just typical poor reporting.

    2. The aircraft in the video has an upper deck that looks a lot like the 747, and the profile is vaguely 747-ish but the cross-section appears very different — quite flattened on the sides.

      According to the Stratolaunch website, the aircraft will be built by Scaled Composites, which does not usually do aluminum airplanes.

      They do say it will use six 747 engines.

  2. I say get rid of the two fuselages altogether and widen the wing into a flying wing design. Have it so that the crew in the rocket strapped underneath has control during the flight out to the launch zone. Then after separation and launch the flying wing turns into a UAV directed from the ground to fly itself back to the spaceport.

    1. In an earlier thread someone pointed out that the landing gear on a flying wing would be extremely long, so perhaps an inverted gull flying wing, a cross between an F4U Corsair and a B-2 or Avro Vulcan.

      Another odd option would be to change the drop completely, ejecting the rocket either forwards or backwards during a zero-G lob. Structurally, that would allow a very thick flying wing with the root area near maximum thickness being uncut by a bomb bay, so the landing gear would still be short, the rocket itself would impose almost no drag penalty, and the rocket could ride in a fully insulated tube.

      Putting the insulation in the bomb bay would be a huge benefit for cyrogenic upper stages, eliminating the risk of a high velocity insulation failure, reducing upper stage size and mass, and reusing the insulation as part of the carrier aircraft.

      So if we had a Falcon 9 with a main tank diameter of 12 feet, left 1 foot top and bottom for insulation and wing spar carry throughs, the airfoil’s center section would need to be 14 feet thick. Using a typical reflexed flying wing airfoil like the S5020 (8.4% thick) would give the wing a root chord of 167 feet.

      Forward and back of the central section the center fusulage would stay at this diameter, or even widen toward the front (in a forward toss design) to accomodate a 17 foot payload fairing.

  3. Besides the animation, I’m unable to find the actual news conference video itself. Anyone have a link?

  4. They’re at least not using the 747 fuselages, beyond that I’m not clear. Burt went on about how “salvaging” old 747 equipment for something like this would be stupid,that he’d been saying that for 30 years.

    That being said, they apparently will be using the _engines_. What else may be used is not clear.

  5. I wonder if they considered using the volume in the fuselages for equipment to distill O2 from ambient air during the outbound leg prior to launch, and pumping it to the first stage while at altitude? This would reduce the overall takeoff weight considerably, I imagine.

  6. So, if it’s “Any Orbit, Any Time” how do they avoid dropping the spent booster into the middle of somewhere expensive? Launching out of Florida, you drop into the Atlantic. Do they need different “release” sites depending on where they’re headed?

    I get that they fly the aircraft a considerable distance between ‘spaceport’ and ‘launch’, but if your purpose is to match orbits quickly with something already up there (Bigelow’s space hotel for example) your release points are already tightly constrained.

  8. In order to have flying wing the wing airfoil needs to have a neutral pitching moment. An airfoil with neutral pitching moment is less efficient than one with a normal nose down pitching moment. Also flying wings are very sensitive to CG location. A flying wing makes no sense for such a launcher for basic aerodynamic reasons.

    The book Model airplane aerodynamics has a simplified coverage of aero stability issues. Aircraft that you want to go to high altitude share a lot of characteristics with gliders re wing efficiency etc.. there was a long running newsletter called TWITT (The wing is the thing) talking about flying wing glider aerodynamics. My last significant project before rockets was a solar powered RC plane designed with a low pitching moment airfoil so the wing could be structurally very light.

    1. ^Actually, you don’t need to limit the pitching moment if you get a bit more clever. Conventional flying wings get their short term pitch stability from the wing’s aerodynamics, as changes in control surface motions can take several chord lengths of travel to take effect, which is why so many projects with dynamically unstable configurations failed. Those were trying to compensate for immediate deviations using computers moving control surfaces whose full reaction has a significant time lag.

      If you instead control pitch by applying torque to gyros (such as a big electric motor) in the wing, you can control your pitch angle immediately. To keep the motors from spinning up to their maximum, you use a tachometerand use that as input to a weight shift servo that moves those same motors fore and aft, trying to return the motor speed to zero. There is no response delay because the system relies on the conservation of angular momentum instead of induced changes to the circulation around the airfoil.

      But delta wings and conventional flying wings don’t even need to go there to achieve stability. They’ve been flying for seventy years in all sorts of high speed aircraft. One of the reasons they’re not more widely used is their wetted and lower Cl/Cd, but a space launcher doesn’t need extended range or optimal fuel economy, since it has no real commercial competition and isn’t going to be flown all that often. It’s going to make short hops to altitude and then back down.

      In the quest for the largest payload you could air launch, your naturally going to fall back to the question of the largest payload you can haul to altitude, and that is largely determined by the largest aircraft you can conceivably build. I think flex and torsion will start penalizing convention wing designs, which may be why wingspans hit at least a local maximum around the 1940’s and 1950’s.

  10. So what airport do they plan to use? A 747-400’s horizontal stabilizer is 72′. Using the stabilizer as a measuring stick, the landing gear footprint is at least 150′ wide. That’s about 50′ clearance on Mojave’s Runway 12/30, except the taxiway isn’t wide enough.

    1. They’re building a big hangar for it in Mojave. Presumably they’ll pay to add concrete from it to get to the runway as well. KSC could probably handle it, as could any B-52 base.

      1. Ah, outriggers… The thing is a B-52’s can turn in a smaller diameter due to its main gear having a smaller footprint. For this birdzilla, unless you setup a track like system, you can only pivot on one corner, making your turning radius 150′ as well. Even a B-52 base will have tolerance problems, but I agree it may just work. SLF is wide enough.

        I do wonder if the scale will be adjusted a bit on this bird to accommodate more fields. If its adjusted, it will allow more utility for the aircraft when not servicing launch missions. The mothership could make an awesome freighter.

Comments are closed.