Twelve (was Nine) Years Later and No Closer To Shipping: Terrafugia Transition’s Continuously Slipping Delivery Date…

Terrafugia incorporated in May, 2006 and now nine twelve years later in May, 2015 July, 2018, their Transition aircraft remains the same “two years” away from first customer delivery as when they started.  Considering Terrafugia’s history of delivery estimates, prospective customers should probably toss their most recent estimate in the heap along with all of the other missed estimates that they’ve published.

This list of their most prominent public announcements about expected delivery of the first Transition aircraft to a customer shows no progress toward shipment.  It was compiled in hopes of discerning a trend that might indicate whether the company was closing in on a ship date; they’re not converging.  The estimates show quite the opposite; Terrafugia’s statements have stuck to using a date that’s always about two years from today (average 21.0 months, stdev.p 3.7), regardless of when today actually falls.  October, 2008 represented the high point for customers when Terrafugia proclaimed that they were only 15 months away from starting shipments.  On average since then, Terrafugia has pushed their deadline further into the future and assiduously avoided converging on a real ship date.

Terrafugia Transition’s Estimated Ship Date moves in lock step with the calendar and they appear to be settling in on a delivery “estimate” that’s consistently “24 months in the future”. If Terrafugia were converging on a ship date, then the orange curve should flatten out and the blue one should curve down toward zero as press releases indicated progress toward an actual shipment.

It appears that either Terrafugia employs really poor forecasters, they’re trying to hide something from the public, or maybe it’s just far harder to bring an airplane to market than newly minted college graduates could have imagined?  Their announcements, whatever the motivation, really push the line between optimism and deception.

Update (later May 11, 2015): Only Terrafugia’s press releases indicate they’re making no progress. Their accomplishments do show advancement, just not at the optimistic pace their press releases would have you believe. They’ve certainly learned a lot from the Proof-Of-Concept and first prototype vehicles as well as from their positive FAA and DOT regulatory decisions.  Hopefully their press officer learns from this post too.

Update (July, 2018):  XKCD has gotten onboard by tracking JWST launch date estimates!

FWIW, the slope for Terrafugia’s first customer ship estimates is 1.12. Ouch!

S.H.I.E.L.D’s Helicarrier Could Lift-off Using Today’s Technology

Immediately after watching The Avengers movie (on opening day; and yes, it’s been quite a while), I set off, tongue firmly in cheek, to reality-check S.H.I.E.L.D’s Helicarrier. Professor Allain’s Wired blog “Could the S.H.I.E.L.D Helicarrier Fly?” arrives at a different conclusion than I did, so I thought it’s finally time to write up my alternate assessment.

Like the professor, I began by looking into Nimitz class aircraft carriers. Built using HSLA-100 steel, those 333 meter long carriers displace about 100,000 long tons. S.H.I.E.L.D, with flight as a design goal, would clearly upgrade to titanium, employ aircraft construction techniques, and use other advanced methods to lighten their 450 m Helicarrier by about half to 55,000 metric tons (t).

Next, could real fans fit in the space allocated and still generate enough thrust to lift 55 kt? Using the Harriers Alpha Jets on deck as measuring sticks shows that each of the four fans is 51 m in diameter giving a total rotor area of 8,200 m². The Helicarrier name invites comparison with helicopters, so I initially checked its fans against the remarkable Russian Mi-26 heavy-lift helicopter. The Mi-26′ has a maximum takeoff weight of 56 t using a rotor 32 m across to provide a lift/area ratio of 0.07 t/m². That herculean helicopter’s lift/area ratio provides only 1% of what S.H.I.E.L.D needs to fly. Helicopter rotors are out.

Fortunately, engineers have already done better, much better; the Rolls-Royce LiftSystem in the F-35B produces far higher lift/area ratios. For instance, the front LiftFan generates 20,000 lb of lift from a 127 cm (50 in.) fan and the whole system generates 19 t (41,900 lb) of lift from 2.51 m² of duct area (LiftFan, jet exhaust, and roll-posts). Its 7.56 t/m² ratio leaps two orders of magnitude past the Mi-26 and provides plenty of lift-off thrust for S.H.I.E.L.D’s headquarters. To sustain a single rotor failure, the Helicarrier engineers must have improved on Rolls-Royce by at least 14% to 8.61 t/m² or more. Nonetheless, the Helicarrier appears to fly within the laws of physics here.

Spinning those fans requires an enormous amount of power and generating it presents an even bigger engineering problem, but it hovers (barely) within the realm of possibility. The F35-B’s thrust ratio (55,000 shp delivering 41,900 lb thrust) implies the Helicarrier carries engine(s) capable of 157 million horsepower (shp) or ~117 gigawatts output (that’s more power than all of the nuclear power plants in the USA combined). Any power source would need to be scaled up, but allocating 20% of the carrier’s gross tonnage to the power plant sets the minimum power density at 10.8 ^kW/_kg; for comparison, here’s a quick rundown of some real-world power densities:

• A Pratt & Whitney F135 jet turbine in the F35B produces 38 ^kW/_kg
• The RS-25D Space Shuttle Main Engine delivers the highest power to weight ratio available today at 1445 ^kW/_kg
• For something closer to home, the LS9 supercharged V8 in a Corvette C6 ZR1 produces 638 HP and weighs 530 lb (dry) for a power to weight ratio of 0.9 ^kW/_kg
• The Indy Car Series 2012- engine weighs just 112.5 kg (248 lb) and puts out 522 kW (700 HP) 4.46 kW/kg or 5× the specific power of a Corvette but just half of what’s needed
• A Nimitz A4W nuclear reactor weighs a lot more but at least it contains enough fuel for two decades; it generates 0.05 ^kW/_kg with older, 18% efficienct steam turbines
• The Los Alamos Heat Pipe reactor (alpha of 0.43) combined with 40%+ efficiency turbines raises its specific power to 0.8 ^kW/_kg

Unlike the Nimitz aircraft carrier, nuclear reactors, even lightweight research reactors, won’t work. S.H.I.E.L.D would need around 530 A4W reactors to generate 117 GW and those would weigh over 2 million metric tons; that wouldn’t just ground the Helicarrier, it would sink it!

Shuttle main engines would weigh 81 t or 0.15% of the total. Using the rest of the weight allocation for cryogenic fuel provides 2 hours of flight time in a tank 111 m long and 11 m in diameter.

Turbines have high enough specific power but need to be scaled up a lot; just ganging together 3,000 P&W F135 turbines would be an engineering and maintenance nightmare! Real-world engines have high enough specific power for the Helicarrier, but scaling them up would be incredibly difficult.

For in-world consistency, I also had to consider Tony Stark’s imaginary arc reactors. His Mark III could generate 3 gigawatts (3×10⁹ watts) and the Mark IV upgrade quadrupled that to 12 gigawatts (12×10⁹ watts). Stark could easily pickup either version by hand and so I’ll assume a maximum weight of 50 kg. That’s 240,000 ^kW/_kg! and a specific power 1,600 times greater than the Shuttle turbopump! Using an exotic power source like that obviates the need for anything fancy; just scale up a standard AC induction motor and watch it fly!