Technology

From the point of view of society, technology is the reason for doing science.

Turbine Cars

Capstone Turbine is planning limited production of a plug-in hybrid, the CMT-380 that uses a small turbine engine to extend range. The car looks great, as it should because it's a basically just a Factory Five GTM with batteries, an electric motor, and a turbine powered generator to keep the batteries topped up on long trips.

My guess is that the weight of the batteries hurts handling and acceleration somewhat.However, I'm still really excited by this car because I'm persuaded that putting turbines in cars is a good thing.

Turbines have several advantages over piston-engines:

1. They are smaller and lighter-weight for a given horsepower.
2. They are much more efficient - more of the energy of the fuel can be turned into usable power.
3. They are much cleaner burning, producing less NOx because they can run a leaner (more oxygen rich) burn.
4. They are naturally flex-fuel. Though turbines are usually optimized for one particular fuel they are generally much less fuel sensitive than piston-engines, making flex-fuel designs easy to implement.
5. They are much more reliable than piston-engines.

For essentially these reasons, turbines are used to power some special purpose ground vehicles, like the M1 Abrams.

Here's another turbine diagram:

So if turbines are so great, why aren't they already being used in cars? They have two serious limitations that have made them impractical until now. The first is that turbines are not good at changing speed. They lose much of their efficiency advantage over piston engines if they are forced frequently change RPM. Also, they don't change speed very rapidly - after all they have a lot of rotating mass that doesn't want to slow down or speed up. The second limitation is that they are high cost.

The brilliant thing about using a turbine in a plug-in hybrid is that it solves the problem of changing RPM. The CMT-380 uses the turbine to spin a generator that charges the batteries when they get depleted. That way, the turbine can spin along at the one RPM where it is most efficient, regardless of how fast the car is moving.

The problem of cost can also be overcome but it depends on economies of scale, and possibly the regulatory environment. For example, tighter emissions requirements may give turbines an advantage over piston-engines. It's certainly the case that if turbines were widely adopted for automotive use that their price would come down somewhat.

Systems Engineering - A Description

Systems Engineering is a structured approach to the development of complex, engineered systems.

The Whole System Approach

·         Top-down design, optimizing for system effectiveness not necessarily component effectiveness.

o   E.g. Metallic structures on spacecraft can magnify radiation hazards. Metal may be the best choice for the frame component, but may not be the best choice for the system.

·         Design the right system.

·         Systems design is inherently interdisciplinary. Systems Engineers must possess and cultivate broad technical knowledge.

·         Manage subsystem interactions.

Project Management

·         Manage cost, resource utilization, and scheduling constraints from an engineering standpoint.

·         Collect voice of customer, communicate with stakeholders, manage and coordinate suppliers.

·         Prepare and maintain a current Systems Engineering Management Plan (SEMP) as the primary controlling document for all system development activities.

The Iterative Design and Evaluation Method

·         The Systems Engineering method is an iterative process by which a system concept is developed and refined with continual evaluation against requirements, until a completed and functional system design is produced that meets the goals established for the system.

• The steps in the Systems Engineering method include:

1.       Develop system performance and cost requirements.

2.       Develop multiple system concepts that can satisfy most or all of the requirements.

3.       Select a concept and begin the design/evaluation loop.

a.       At the outset of the design/evaluation loop, the system concept has poor definition. Each pass through the loop increases the detail of the design.

b.      Also, at the outset there are many risks and unknowns. As the detail is added to the design, frequent evaluation of the design through testing and simulation identifies problems that are then corrected in subsequent design iterations. In this way risk is diminished on each pass through the loop

c.       The design/evaluation loop concludes when a system design that satisfies the performance and cost requirements is complete, and when all risks relevant to the design have been abated or effectively managed.

4.       Produce and implement the system.

Risk Management

·         Systems design carries risk inherently. Consequently, risk management is an important part of the Systems Engineering method.

·         Some common systems risks are:

o   Interdependencies between subsystems magnify effects of point failures.

o   Complex system behavior may be difficult to model or predict (greater than the sum of its parts).

o   System dynamics are strongly characterized by bottlenecks, load variations, and feedback loops.

o   New failure modes arise due to novel design, new technology, or increased complexity.

Interface Design

·         The Systems Engineer (or team) is wholly responsible for the specification and design of interfaces.

o   Create and maintain current Interface Control Documents (ICDs) for all system interfaces.

·         Interfaces carry material, information and energy between components. Interface types include:

o   Mechanical

o   Electrical

o   Data

·         Interfaces are loaded junctions exposed to hazards from more than one direction.

·         Interfaces are sensitive to peak loads, and are natural bottlenecks that can limit system performance.

·         Interfaces can be the source of unintended feedback loops.

·         The more complex a system is the more critical interface design becomes.

UPDATE - Presentation available here.

Systems Engineering

The New Hampshire Business Review is reporting that the University of New Hampshire will begin offering a certificate in Software Systems Engineering. From the article:


“Engineers who are successful at this ‘big picture’ work are rare, yet the demand for these skills is high...”


I think this is exactly correct, and not just in software design. Systems Engineering is one of the few academic disciplines, and the only engineering discipline, that is moving toward greater generalism. The increasing depth of technological knowledge has driven specialization at an increasing rate, and at a heavy cost to technical breadth. Additionally, the increasing specialization has tended to drive natural-born generalists from the ranks of those who pursue engineering degrees. The result is a serious lack of interdisciplinary competence and large world view that is essential to the complex engineering projects that are driving civilization's next big developments. Think of the projects to re-engineer energy production, to redesign cities and transportation at a conceptual level, and even to engineer society and government for the improved welfare of all citizens (we desperately need Economists to start thinking of themselves as Engineers - specifically Systems Engineers - and not as Scientists). 

The emergence of Systems Engineering is a direct and deliberate response to all of these trends. It got its start in the space program, but it has applications far beyond.

Addendum: The University of Illionis is offering a new Master of Science in Finacial Engineering degree through their Systems Engineering department. It's fascinating to me to see a university marrying its Business and Engineering departments in this way.

Sunday Links

California's budget problem results from the uncontrolled growth of government. However, help is on the way! Unfortunately it's coming in the form of a possibly illegal takings (Mother Jones and Cafe Hayek).

You may have already guessed that a rushed and kludgey repair job on the Bay Bridge caused the recent failure. This analysis suggests that guess is correct (Sci-experiments.com).

The University of Utah Genetic Science and Learning Center has created an excellent interactive graphic that helps explain the scale of small things. You'll want to show this one to your kids as you explain to them about germs or molecules (U of U).

The problem with economics is that it hasn't advanced far enough that it can make useful predictions. However, as Nassim Nicholas Taleb would point out, that's OK because there are still plenty of economists who are willing to go out on a limb and suggest untestable hypotheses to explain past events (Amazon.com and Bluematter).

The problem with socialism is that no one knows how much anything costs. Eric Falkenstein uses Amtrack as an example. Funny, but I keep hearing the same thing about health care (Falkenblog).