The Maltese Falcon

If we're going to follow the money and let the US patent content lead us by the nose, then it calls for a root-and-branch reappraisal of how we configure the eight motors that we've flight-tested recently in the double-decker format appearing two posts ago and which the patent examiner ruled out as at all original in the scheme of things. If there's one thing my brain's full of, it is the endless variations involved in configuring electrical motors around a space-frame for the purposes of flying people by drone.

At the smaller scale, the go-to drone for heavy-lift operations like professional video, aerial survey and crop-spraying is a ring-of-roses arrangement of eight propellers. This provides the most stable platform and the best aerodynamic efficiency, along with the  most assured means of redundancy in the event of a failure of a single power unit. As a result, they don't come cheap, even at this 'industrial' scale.

At the same time they are almost invariably laid out is 'spider-leg' fashion, arrayed in a radial format around the centre-body. Up the ante to cargo drones or people-carriers however, and as often as not you've either a tic-tac-toe arrangement of four spars and a motor at the end of each. Alternatively you might find a pair of spars along the sides of a cockpit, with four motors arrayed along the length of each.

Neither suit the present objective of elevating human beings in a form of 'transporter' of the kind featured in episodes of Star Trek, emptying a 'phone-booth' of around two feet square (or one, in the case of the current half-scale prototype). Discounting the latter type altogether, the problem with a tic-tac-toe layout is that the central square is wholly defined by the diameter of the propellers, and far too big for our purposes.

Instead I opt for a 'Maltese Cross' layout, independent of the diameter of propellers on one hand and able to split into a pair of 'dog-bones' or bogeys for storage or transport. The planform in view will feature 60" long sections, 24" short (between motor axes) as well our 22" propellers. The pre-existing foot-square phone-booth will pass within the outline of its centre-section, the rig rising under its own power to engage the flange at the upper end of said booth and elevate its occupant.

I'm not a big one for setting people on top of drones in harms way ~ thought we could ~ for when all else fails in flight you're descending head first into the ground. Our first flight-test may yet simply affix the passenger booth to the underside (in which event the extent of any undercarriage is marked by the cross-hairs in the above draft), while my own preference is to start out the way we mean to finish by elevating into flight a wholly independent cabin.

It means at the same time that for the purpose of hauling cargo, we can containerise carriage in standardised boxes albeit with an overhang up top able to engage with the drone. I drive semis to pay the bills, and the patentable system changing the world in the 1960s was not the container itself, but those interlocks at each corner securing it.

Don't get me wrong... I'm a small foot-print kind of guy when it comes to personal air vehicles but consider this. We've eight under-powered motors we need to extract all we can from. I've two experts on tap who all along have been pushing me to adopt the tried-and-tested layouts commonplace to Pixhawk flight controllers, beside a patent agent's urgings to follow the money.

Above all this way forward most closely follows an original vision that was intended to entertain, at the same time as inspire.

Beam me up, Scotty.

Money Shot

This changes everything.

From the US patent examiner's initial findings I appear to be in good company, as it cites prior art from Stellantis and Kitty Hawk: an Italian mobility behemoth founded by FIAT and a developer of such solutions by relative unknowns called Google and Boeing.

The notion of flying people in pods sandwiched by propellers is nixed by Stellantis, whose project predated drones and so comprises just two propellers. Meantimes the examiner rejects as original any arrangement of spars you may feel is the 'sliced bread' of mounting motors for flight.

Rising from the ashes of the report like a Phoenix however is a means of flight able to rise under its own power around a transporter, and so beam you up like Captain Kirk.

With this we may yet secure the monopoly on such means across the whole of the US.

Mwah ha, mwah ha, mwah ha ha ha HA HA HA!

Statement of Intent

A benefit of taking time out ~ particularly after the disappointment of our recent flight test ~ is that it provides the opportunity for a reassessment of the endgame. Clearly I have become unduly exercised by the naff-naff and trivia involved in the construction of the airframe at the cost of the overall objective.

What most inspires about the design is undoubtably the enclosure and flight-deck we have, that stems itself from a prolonged evolution of the ideal means for short-range personal air vehicles of this kind. Aside from this however the key to the effectiveness and practicality of the outline is undoubtably the division of lift between an upper and lower drone, each of which can be separated from that enclosure for either transport or storage; and each of which can be addressed separately with a view to redundancy.

As we've to rebuild the airframe to some extent before testing its constituent drones, then crisis can be turned opportunity by examining whether alternative arrangements of airframe might suit equally well. This is one we've flown before, albeit terminated at around waist height for an operator stood within it. At the time, pitching the upper drone in the overhead did not look structurally feasible, but after countless variations it would appear that in fact it is.

Nothing in the sketch above has not been assembled before, and merely rearranges its constituent parts to suit present objectives. It's not rocket science and reading about the struggles of private individuals to put actual rockets and miniature satellites into orbit, the one thing to take away from such endeavours is the time that taken to turn vision into reality. Almost without exception, the current crop of billionaires took not years to elevate themselves into orbit (which still eludes some of them), but decades.

The outline above will be constructed at half scale to suit the current mannekin; seen below in platform it features a foot-wide phone-booth within a three-feet square that pitches the propellers at a diagonal distance of 4.25 feet or 1.30 metres. It would thus feet the dimensional strictures of GoFly's Challenge only with the propellers removed. Nonetheless such challenges as these, like the X-prize, set the ball rolling in pursuit of products that we'd like to see brought to life.

Re: framing the question

To recap, the most recent flight-tests failed because the airframe ~ broadly configured as a cube with a propeller at each of its eight corners ~ was arranged with 'X-8' logic, in so far as all eight motors were involved in control motions. At its heart the problem lay in the fact that only the upper drone was constructed in alloy whilst the booth and lower drone were made of plastic extrusion throughout. Without the upper end tested independently, we have to conjecture that the three-dimensional space-frame in its entirety was insufficiently rigid enough to resist the resonance and flexure that play havoc with computerised control.

In order to resume the test program it will be necessary to fly the upper drone whilst attached to a vacant accommodation booth underpinned by an identical undercarriage of the same outline. That done the lower drone can be tested independently in its role as merely providing sufficient thrust to offset the bulk of the weight of the payload. The approach has much to commend it as a first step, as motors run at constant RPM use considerably less energy than those required constantly to vary it in accordance with the demands of the flight controller.

Fortunately it would appear that the airframe of each drone may be left substantially unmodified, as the picture above shows. Each of the perimeter extrusions measures around 30" but including the tube-connectors the outside edge of each square is 32". In turn this means that if the motor-mounts are offset upon the airframe then there is sufficient clearance for the propellers. A quick check using classroom Pythagoras confirms that a measurement of 16" along the shorter sides of the triangle bound by the hypotenuse (in green) provides for around a half-inch of spacing between rotors.

At the same time we'll take the oppo to reconfigure with the more aerodynamically efficient tic-tac-toe arrangement of rotors, whose outlines on the upper drone appear in red whilst those on the lower appear in blue. You might ask why not arrange them otherwise, but the suggested arrangement allows for regular ingress and egress for the passenger at the bottom end, whilst at the top or steering end we revisit a config that has been successfully flown in the past... likely because it is more rigid than the alternative of controlling motion using a motor at each corner.

What emerges from all of this is effectively an abandonment of the notion that upper and lower drones might be identical in order to reduce the part count to a minimum. In design, as in life, there is ever a compromise between the perfect and the practical.

Mourning becomes Electra

Even NASA can fail. In fact what self-confessedly drove Elon Musk to Martian missions was precisely the feeling that they'd failed in that ambition too. It begs the question though as to what failure is anyway, for to my mind the overriding failure in life is not to venture much for fear of it.

The X-57 ('X' being for Experimental) took the same path as other electrical projects in basing itself upon an existing airframe in the form of the lightest twin-engine airplane available viz. P2006T. Italian aircraft have always been among the most imaginative, invariably as stylish as the efforts of its fashion houses.

Budgeted at $100 million, an 'unforeseen' safety issue involving its propulsion system would apparently take that to nearer $165 million... and I thought I had problems. It is not by a long way the first fixed-wing type to use a distributed array of motors, NASA themselves long having used the approach on delicate solar-powered types which, of necessity, had to split the load along the length of each wing.

Initiated as long ago as 2016, too, it may arguably have been the inspiration for a small number of projects in Europe and the US with commercial orders... not least Electra.