Tesla Roadster Progress - From EP to VP

We've just achieved a significant milestone on our road to Tesla Roadster production. Our first Validation Prototype was assembled at the Hethel facility in the U.K. and was recently airlifted to our San Carlos, Calif., workshop to commence system testing.

VP1 at the Hethel, U.K., facility. The car is riding
a little high because the battery pack and motor
are not yet installed.

The Validation Prototypes (VPs) are the second generation of prototypes, succeeding the first generation Engineering Prototypes (EPs). Although many of the EPs are still undergoing testing, VPs incorporate many changes from EP learning. They are much closer in design to the final production vehicles and so enable us to do more refined testing and validation.

Having been involved in previous vehicle programs, I often get comments from people who see the first prototype (family and friends included, although they should know better by now) along the lines of: "surely it’s nearly finished, so why does it take so long to get to production?" Despite the use of modern computer systems to design and predict the performance of the components, it isn’t until you actually build and test a vehicle that you find out many of the detailed tweaks required to meet the quality, reliability, and performance targets expected of today’s motor cars. Thus the need for both EPs and VPs.

At the start of the Tesla Roadster development, Tesla Motors adopted a New Product Introduction (NPI) process. This process is a cousin of the product development processes utilized by large manufacturers. While the process is lengthy and expensive, it ensures that we produce cars at the level of quality, safety, and durability that customers expect.

From our photographs, the EP & VP cars will look pretty identical, but very few of the newly engineered parts remain unchanged, whether through detail-level physical change or manufacturing process. In fact, I'm struggling to think of one.

Before and after: EP tail lights (top)
used off-the-shelf parts while
VP lights (below) are custom made
and meet FMVSS requirements.

If you wish to play "spot the difference" between our photographs of the EPs and VP1, here are some to look out for:

  • Headlamp and tail lamps (or headlights and tail lights) – The EPs had functional place holders while VPs are fitted to production intent.
  • Seats – The VP seat shell has a wider base and trim detail has evolved.
  • Centre console – We modified the profile to match the seat change.
  • Heating and ventilation – Controls and graphics were adjusted for clarity.
  • CHMSL – Now there's a word you don't come across very often: Center High Mounted Stop Lamp, pronounced "chimsel." It was repositioned to improve rear visibility.

You may also notice that the car looks like it is riding significantly higher than the EP. That isn't because we decided to make a rally car version. It is because the battery pack (the Energy Storage System, or ESS, as we call it) and motor have not been installed yet, so the car is significantly lighter than what the suspension is set for. When those components are added in San Carlos, the ride height will be normal.

Many of the subtle changes that you will not notice relate to aiding the final assembly process during production. These may include visible items for fit and finish, but also a whole host of cable and pipe routings under the skin, plus modifications to improve accessibility for the line assembly operation. This is not only to make life "easier" for the assembler but because easy = consistent = quality and reliability over large production volumes.

The major new technology systems have not escaped the process of evolution, either. Our Power Electronics Module (PEM), motor, and ESS have all gone through significant detailed design changes to improve performance, reliability, and manufacturability. Continued testing and refinement of these elements will occur through the VP phase.

There are also performance "tuning" changes that are built into the VP cars following learning from the EPs. These include driveline mounting stiffness to improve noise and vibration concerns; spring, damper, and sway bar tuning for ride and handling (still some way to go before we finalize these); throttle response; traction control, ABS, and regenerative braking; and the motor control algorithm. And then there are all of the firmware vehicle behaviors.

I think I've said previously that we have more computing power than NASA. I probably underestimated it. One great thing about having so much intelligent control over the vehicle systems is that it allows us to program some trick behaviors relatively easily. One bad thing about having so much intelligent control over the vehicle systems is that it allows us to program some trick behaviors relatively easily. Only kidding, it's a pleasure to be working with my Silicon Valley colleagues. :)

Even at VP level there are features that are still not production intent – by that I mean we'll have an improved version when we start actual production of the car. Some of the plastic moldings (interior trim, headlamp bezel), for example, do not have the final grain finish. This is not added to the tool until we are confident that we do not require any adjustments to the net shape of the part.

So, it's one VP built and nine others on their way. Why would we want nine more? Yup, you've guessed. Four of them get the pleasure of a short life – they are sacrificed for the final validation crash testing. It is necessary to confirm that none of the detail-level changes has invalidated the crash performance we achieved with the EPs. Crash testing is always in the spotlight but there are numerous FMVSS (Federal Motor Vehicle Safety Standards) that also need to be tested and reported. These include low speed bumper impacts, lighting, demist/defog, and field of view from mirrors. Even the powered windows need to meet FMVSS requirements.

Durability testing of the Tesla Roadster must also be repeated, since we need to ensure that the latest iteration of parts that are destined for production meet our stringent life expectancy requirements. Then there is the dynamic tuning of the many vehicle systems to be finalized.

VP1 on the assembly line

Two of the VPs are destined for marketing use as it is very important that our existing and new customers experience the Tesla Roadster closer to the production intent than available in our existing EPs. These VPs will also be used for "first drive" reviews by major car magazines and other members of the media. Maybe we should have built 20 VPs (unfortunately, the cost of building a VP is quite high).

Both series of prototypes are built not only for their technical development but also to ensure that our supply chain and manufacturing processes are prepared and ready. Getting our suppliers on board and their production systems ready is the start of a chain of events that delivers parts from many countries worldwide, to the assembly plant in Hethel, U.K. Our photographs show the prototypes being assembled within the assembly plant, which is proving the production fixtures and processes. The target is to complete the process development and staff training during the prototype build to confirm our readiness for series production.

Our EP vehicles were a waypoint in the long and expensive process to create a great production car. The arrival of the first VP is the next major step on the way.