Tuesday, January 26, 2016

Back And Forth With skyTran

One of the things we miss about the old days of covering personal rapid transit is the way everything used to be out in the open.

Perhaps an outgrowth of the federally-initiated PRT effort of the Sixties, the leading PRT efforts of the 1990s-Early 2000s welcomed publicity, and actively disseminated the results of their work. That Raytheon was playing with millions in public funds obligated some openness, but that doesn't explain why the private Taxi 2000, and later university spinoff Ultra, was open with the public to varying degrees.

But today's would-be pod transit makers are keeping their cards close to the vest. In some cases the caginess is due to an enterprise not being on the up-and-up (e.g. Maglev Movers, IPERT1, 2, 3), but in most cases the caution arises out of business security. Four, count them, pod transit systems now exist in the world, and the competition to be the fifth might be just that tight.

The result can be 'communication' shielding a lot of mystery. Case in point: the current skyTran demonstration project in Israel. After years of work so secretive that some critics openly accused them of fraud, skyTran is now constructing a demonstration system near Tel Aviv at the campus of Israel Aerospace Industries.

Ask skyTran chief Jerry Sanders about progress and his emailed replies are enthusiastic and confident, yet only partially enlightening. He has some things to say about imminent completion of 'Phase One,' plus some inscrutable attachments. Yet his comments raise further questions; whether this is simply modern corporate communications practice is up to the audience.

Artist Conception
A set of illustrations show a facility resembling an airport lounge or sales showroom. Given the context, could it be the Tel Aviv testing center? But no: in answer to a followup, Sanders explains --
"The illustrations show how easily skyTran infrastructure fits into the urban environment: entering buildings, lobbies, even basement level accommodations."
Jerry Sanders

Maybe skyTran is excited about reinventing the elevator lobby, but seriously folks -- integrating PRT stations into new and existing buildings has been talked about for decades.

Sanders is helpful in clearing up questions about the trusses in Tel Aviv construction photos, which we thought might be station components. He explained under Phase One the guideway will be laid inside those frames, on the ground, giving engineering staff easy access. The drive unit will be tested sans passenger compartment -- that will be attached, he says by the end of the year, when the guideway will be installed on poles.


Tubular video
Early in 2014 we had a chance to see an official presentation containing less than vague descriptions of how skyTran planned to do levitation and propulsion. Depicted was a drive unit that reinvented conventional squirrel cage linear induction -- a motor working like a propeller, pushing against the inside of a tube instead of a flat reaction plate.

Nearly two years later and skyTran is sticking with that approach. Sanders sent us this video to show that it works.

Jerry Sanders

The effect is caused by moving a magnet perpendicular to its long axis along an uncharged aluminum surface. In this video the rotor is turning at 1000 RPM.

Using the same principle to provide lift with two magnetic 'wings' reacting against vertical surfaces, the result is levitation with propulsion.

skyTran now has the hardware to create a demonstration system. It will likely work, and it won't look like past Artist Depictions, which were influenced by inventor Doug Malewicki's conceptual sketches. Gone is the super-skinny guideway, replaced with a 5.9'-wide version: either the wings won't work when close together, or all the parts won't fit inside something that narrow.

(Above) Goodbye skinny     skyTran
(Below) Now: Room for four     skyTran

The other big change is the vehicle, now with an ADA-friendly envelope big enough for 4 people and carryons. We can see why the wings could need to be positioned farther apart.

Whatever the reasons, the changes are good, in that they show skyTran put the engineering and society's expectations first, and didn't feel bound to the Malewicki sketches as inviolable. The result could prove to be a mechanically simpler and more reliable way to do PRT.


  1. Great post. Your insights -- and especially the 3:51-minute "dropbox" video -- should be required reading, in my opinion, as we gauge the progress of skyTran's technology development in 2016, a crucial year for the company's marketing.

    I have taken the liberty of cross-posting this article to the International Maglev Board, whose members have been monitoring skyTran for years, at http://www.magnetbahnforum.de/phpBB2/viewtopic.php?p=52074#52074

  2. From what I have seen from Skytran public presentations, the reason for widening the beam is not due to a wing problem but a design decision because Skytran intends do track switching vertically through the guide-way.

    When the vehicle travels at high speed, the wing keeps the vehicle flying high at the top of the guide-way and continues straight on the track bypassing the stations.
    When the vehicle travels at slow speed, the wing provides less lift, gravity wins, and the vehicle sinks to the lower part of the guide-way, lands on tiny wheels and switches to a different track heading to a station.

    In order for this system to work, the entire vehicle must fit through the width of the guide-way.
    I can see the appeal of super simple and super small passive track switching system, but I am not sure if this feature overcomes the disadvantages of the wider guide-way with vehicle fly-trough :
    -increased cost for the rest of the track
    -bigger visible structure overhead, more shadow over the streets
    -maximum vehicle width defined by track width (can't mix small cabins with bigger vehicles if needed)

    1. Because of how ST used to look, compared to how it looks now, I wonder how much of the latter was conceived from scratch -- and how much of the former was just spitballing. I suspect where it has ended up -- propellers and wings -- is a hint that the inside of the skinny guideway was just a placeholder. What they've come up with is the only way, or best way, their smart people can devise to make passive maglev work.

      Infrastructure programs that include new technology development seem to inevitably increase in cost as changes are made to overcome design or performance hurdles. What we don't know about ST is how much their costs are affected by making the guideway bigger. We don't know HOW they make it bigger, what makes up the additional material.

      We also can't assume the vehicle can't be wider than the guideway, we've only seen the cabin envelope, not how it is connected to the bogie.

      Some observations about aerial structures:
      ST's guideway is now 5.9' wide. There are a lot of things above grade in the cityscape bigger than that, broader, taller and lit. But PRT designers have yet to put as much effort into guideway aesthetics as engineering. A few have talked about it, but only one comes to mind that has actually produced concepts.

      My ideas on guideway --

      Color: Fit into the immediate surroundings. Earthtones are nice. Yet real guideway so far is either white or gray.

      It should look old: 1890s through 1930s, like the Olmsted Brothers designed it. Space-age may look OK downtown, but not out in the neighborhoods. This applies to the vehicles, not just guideway.

      Design for function: In addition to camouflaging wide guideway and allowing light to pass through it, put that structure to work. 5.9' wide can keep pedestrians dry in the rain and shady in the summer. Support posts can also be kiosks and streetlights (not original ideas).

      I'll conclude by observing that ST's guideway is rather thin when viewed sideways, and view preservation is what many NIMBY's will be concerned with.