Posts Tagged ‘aerospace’

Commemorating a Special Day – Apollo 11

Friday, July 20th, 2012
Upshot of the Apollo 11 Lunar Excursion Module, the Eagle

History and Heroism Infuse the Apollo 11 Lunar Landing!

A Day to Remember!

July 20th 1969 was a special day for this future Aerospace Engineer, in more ways than one. While not aware at the time that was to be my profession, I was a totally engrossed in America’s space program. And so, despite ample distractions, which I will describe later, I found myself planted in front of the television set on that muggy mid-summer evening. I watched history unfold, and heroism manifest, as it was captured and conveyed back to Earth; grainy chunks of rasterized black, white and gray imagery on that screen – breathless.

That was the day that man landed on the moon.

Visionary and Powerful Leadership

It was the crowning event of the American quest set in motion by President Kennedy during his special address to Congress in which he said that “…this nation should commit itself to achieving the goal, before the decade is out, of landing a man on the moon and returning him safely to the earth.” Beautiful, inspirational leadership, and a simple yet elegant system specification as well. To read the entire speech is to witness the power of effective leadership, meted out respectfully mindful of the balance of powers between our three branches of government. A balance of power, and relationships between the branches as established and constrained by our US Constitution. The mission to the moon, and the occasion of this speech, were not for mere pyrotechnic display, or theater, respectively. On the contrary, the President was asking for resources from the Congress in the name of national security. Kennedy cited the extreme stresses of the time, in the midst of the Cold War, and recognizing the on-going struggle between freedom and tyranny taking place on the world stage.

Failed Leadership and Floundering

Kennedy’s strength at the time saddens me, now when considering in contrast, the profound weakness of our current president. Bowing as he does before world leaders, apologizing for, and denying American exceptionalism, abandoning our allies, and decimating our current space program to the point of shambles – we now rely on Russian transport to ferry our astronauts to and from the International Space Station. Pitiful.

Heroism Manifest

As for heroism though, I am continually inspired by that of Neil Armstrong, Buzz Aldrin and Michael Collins – the crew of Apollo 11. To me this is the height of human achievement, exemplary performance under pressure, and a testament to the quality of the human spirit. A spirit which is capable to aspire to, and to accomplish great things. At the bottom of this post I have embedded an annotated video clip of the final 13 of descent and landing on the moon. Armstrong, Aldrin and Mission Control acting in perfect coordination. This is heroism exemplified – Armstrong at the control, Aldrin as co-pilot monitoring systems, and Mission Control coolly and professionally executed mission operations per procedure.

Using computer systems that would be dwarfed in comparison to even the simplest mobile phones of today, they prevailed. The entire video transfixes me, but in particular the last three minutes are absolutely riveting. As Armstrong assesses the suitability of the landing zone he in fact has to make manual flight adjustments to avoid boulder fields. Meanwhile Aldrin is calmly reporting systems status – with master alarms going off, no less! The guidance system was being overloaded, but because of robust software design the descent could continue. Regardless, dealing with master alarms in the final seconds of the landing on man’s greatest adventure to date had to be unnerving – still they steadied on. When they landed the Eagle Lunar Module had less than 25 seconds of fuel remaining. Incredible!

Landing, and then the words: “Houston, Tranquility Base here. The Eagle has landed.”

A Special Gift for a delighted Birthday Boy

As for my other distractions; that day also happened to an anniversary of my own birthday – no need to tell you which anniversary, we’ll let that be a mystery. I am not sure where I stand on the concept of destiny – I don’t actually think that being born on a day that later would also be the day of the first moon landing made me be an aerospace engineer. How I became that is a story for another day.

I can’t deny though, the power of inspiration that I draw from this. Coincidences like this could have had an influence on such choices. But all of that speculation aside I do know that year after year it makes my birthday feel all that more special to me. Not only can I celebrate life, but I can share remembrance of a moment steeped in history and heroism – a moment in time when, as a result of strong vision and leadership, and of near perfect human execution, a great thing was accomplished!

Watch the video here; embedded link provided for your viewing and your appreciation, the annotated video of the Apollo 11 descent and landing:

In addition, the wikipedia entry for this mission is also very interesting.

I find this event inspirational; how does it affect you?

Continuum

Monday, July 9th, 2012
a diagram to illustrate the concept of a continuum

Continuums are Cool!

It is always good to know where you are. This knowledge provides context which can help you make good decisions. It can also help you predict how your environment might affect you physically. This is true in life, in general, but it is also true in science. As an aerospace engineer I am interested in the science of aerodynamics, where environmental context is critically important.

Environment is so important in aerodynamics because aerospace vehicles behave differently depending on where they are. Clearly an airplane and an earth-orbiting satellite operate in different regimes. One way to distinguish flight regimes is determine whether there exists a continuum.

According to wiktionary a continuum is defined as “a continuous series, or whole, no part of which is noticeably different from its adjacent parts, although the ends or extremes of it are very different from each other.”

In practical terms earth’s atmosphere is a continuum. The air is composed of many molecular particles that interact with one another. At sea level these particles are very close and densely packed. High in the atmosphere though, the particles are much less densely packed and are farther apart from one another.

The average distance between particles is called the mean free path. Gravity affects these particles and tends to pull them down to the surface, so they collect densely at sea level and the mean free path is short. With increasing altitude the mean free path increases, for a variety of reasons. Mean free path is one of two important paramters need to the define a continuum.

To discuss the second parameter I need to establish the idea of a simple airplane. The simplest airplane I can think of is a flying disk, so, imagine a frisbee. The diameter of the frisbee is the same as its chord length.For a traditional wing the chord length is the front-to-back distance from its leading edge to its trailing edge. Chord length is the second parameter needed to define continuum.

For the purposes of aerodynamics there is a continuum when the mean free path of the surrounding atmosphere is shorter than the chord length of a object under consideration, in this case, our frisbee.

Once the mean free path exceeds the chord length then there is no continuum anymore. In effect the regime is no longer atmospheric, but rather, space. The physical changes from sea level to the boundary of space are gradual; beyond that boundary the change transitioning to space is abrupt, and calls for a different type of design for any vehicle.

I find this concept compelling for its similarity to other things in life. The ageing process – a continuum. The way we learn – a continuum. Our position in life changes more often like a continuum rather than abruptly. There are many others.

Not all things in life, but many, we experience as a continuum.

I am often amazed at how the things I learned in becoming an engineer have relevance outside of their strict application in science.

 

 

A Brief Introduction to Systems Engineering

Wednesday, June 27th, 2012


Systems engineering is a specialized set of skills that deal with how large and complex projects are acquired for customers like the US Government. Often applied to the development of weapon systems by the defense industry, this approach was also applied for a time in the software development community.

The benefit of the approach, when practiced properly, is that large acquisitions will be more efficient during their development, they will be more likely to be delivered within their cost and schedule constraints, and they will more likely function as required once deployed.

Introduced in the late 1970’s the approach relies on use of diagrammatic models as a means of understanding the context of the systems, its interfaces and its functional requirements. A seminal textbook on the underlying modeling technique was Structured Analysis and System Specification, written by Tom DeMarco.

The goal for a system, as a prerequisite to full-scale development is to have a complete, correct, and executable specification. To do that, the system’s context, boundary, external entities, interfaces, functions, and data needs are defined throughout the process of modeling the system.

The method uses the power of abstraction to define each level appropriate to its implementation. Abstraction means that only the level of detail required is dealt with at that level, and subordinate details are abstracted and pushed down to the correct level where they are meaning full. For example if the system is military airlift, the highest specification only speaks to the distance, volume, frequency and reliability of transport that is required. The fact fact there may be a new airplane as part of the acquisition, or a ground transportation infrastructure, those are to be considered as lower level components and are separately modeled and specified.

Once potential problems are identified and solved in a process called functional analysis, the resulting models can be converted to a common language set of specification that represent each applicable level of implementation.

Realities of the modern economy, changes in acquisition, including likely reductions in defense funding will affect, and possibility displace, many in the workforce. Even though not in vogue outside of defense, the method still has merit. It simply remains as a challenge to the engineer in transition (from defense to commercial) to discover what concepts and portions of the method are reusable and will complement current commercial development techniques. Understanding these systems engineering concepts will be helpful in preparing for that transition. Although specific techniques may have evolved, the need for correctness in understanding the system being built has not.