The Mystery Proceedings

At the end of 8th grade, I anonymously received the 1989 Proceedings of the National Space Society’s Eighth Annual International Space Development Conference.

To this day, I have no idea who sent it.

Someone knew of my interest in aerospace. I have no idea why they picked these particular proceedings, as it was well past 1989. I still have the book. Thanks to anonymous! Sometimes the mysteries of life are never known.

Aircraft Dutch Roll with No Dihedral?

Months ago, an excellent question appeared on the Modeling Sciences sub-forum of concerning an flight-dynamics aerospace engineering topic: Is dutch roll possible in an aircraft with zero effective dihedral?

The answer is yes.

Simplified Yaw-only Analysis

The dutch roll flight mode shows up in a yaw only behavior driven in frequency by the yaw stiffness Nβ and in damping by yaw damping Nr. A pilot would identify the behavior as a snake dominated dutch roll behavior. With zero effective dihedral, we could also reasonably expect only little to modest yaw-roll coupling through the rate terms, which would be primarily driven by the vertical offsets of surfaces. For the engineers, this simplified 2DOF model of dutch roll has a frequency and damping term approximated as: (derivation)

Interestingly enough, the dutch roll behavior seems to appear even if the aircraft has zero effective dihedral AND zero effective yaw stiffness, provided the product of yaw damping and sideforce derivatives are positive. Both Nr and Yβ are almost always expected to be negative.

Coupled Roll-Yaw Analysis

The dutch roll flight modes show up in higher fidelity dynamics models. The lateral 4DOF model below contains the spiral, roll, and dutch roll modes with sideslip, roll rate, yaw rate, and roll angle perturbation states:

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[Book Review] Failure Is Not An Option by Gene Kranz

Failure Is Not An Option describes the Mission Control career of Gene Kranz, the archetypal spacecraft flight director. The book covers the period from Mercury to Apollo with additional chapters of Gene Kranz’s early life and USAF pilot experience.

This book is a gem in that Kranz tells the story of the people, the machines, and the infrastructure. He clears shows the challenges, the solutions, the trials, the magnificent success of the Apollo program, and how NASA moved on.

I particularly enjoyed the discussions of infrastructure development (e.g. flight computers, tracking networks). Several of his insights were introduced into my own R&D group, as we see similar challenges. This book would be useful for startup managers and those people developing the infrastructure needed for a complex engineering or science program.

Strongly recommended for aerospace engineers and program managers.

“The Kranz Dictum” after Apollo 1

Spaceflight will never tolerate carelessness, incapacity, and neglect. Somewhere, somehow, we screwed up. It could have been in design, build, or test. Whatever it was, we should have caught it. We were too gung ho about the schedule and we locked out all of the problems we saw each day in our work. Every element of the program was in trouble and so were we. The simulators were not working, Mission Control was behind in virtually every area, and the flight and test procedures changed daily. Nothing we did had any shelf life. Not one of us stood up and said, “Dammit, stop!” I don’t know what Thompson’s committee will find as the cause, but I know what I find. We are the cause! We were not ready! We did not do our job. We were rolling the dice, hoping that things would come together by launch day, when in our hearts we knew it would take a miracle. We were pushing the schedule and betting that the Cape would slip before we did.

From this day forward, Flight Control will be known by two words: “Tough” and “Competent”. Tough means we are forever accountable for what we do or what we fail to do. We will never again compromise our responsibilities. Every time we walk into Mission Control we will know what we stand for. Competent means we will never take anything for granted. We will never be found short in our knowledge and in our skills. Mission Control will be perfect. When you leave this meeting today you will go to your office and the first thing you will do there is to write “Tough and Competent” on your blackboards. It will never be erased. Each day when you enter the room these words will remind you of the price paid by Grissom, White, and Chaffee. These words are the price of admission to the ranks of Mission Control.

USS Alabama Battleship Memorial Park

The USS Alabama Battleship Memorial Park in Mobile, AL displays an interesting collection of WW2 ships and aircraft not normally seen. The collection includes several rare museum items. The park is well worth the visit.

The Battleship Memorial Park visit is contained in 3 parts:

USS Alabama (BB-60)

My visit operated under a slightly modified charter, as it was a sponsored program by the BSA and included an overnight “opportunity”. The ship is designed around three 16 inch gun turrets.

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Aircraft at Battleship Memorial Park

The aircraft collection at the USS Alabama Battleship Memorial Park (Part 1 here) is quite special. There are several gems hidden among the more ordinary museum pieces.

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USS Drum (SS-228)

The second ship at the USS Alabama museum is a WW2 submarine, the USS Drum. Part 1 (USS Alabama) is available here.

The Drum museum is a nice example of a WW2 US submarine.

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Colorado Mountains

In March 2019, I had the opportunity through my job to fly in the mountains of Colorado on a DHC-6 Twin Otter. Here are some images of the flight campaign.

[Book Review] Roskam’s Airplane War Stories

Dr. Jan Roskam’s Airplane War Stories is a seriously good book. The lessons come in bite sized tales (“War Story #”) with the wonderful treat of providing the moral (“Lesson”) in his own words.

This book won’t teach you how to analyze aircraft -Dr. Roskam’s other books take that charge- but once you do know the mathematics, the concept, and the application, this book is a lot of fun to read.

The first part of the book is a bit better than the later part. It is slightly disappointing that the book does not cover as many aircraft design topics with specific discussions of the aircraft features.

Thank you Dr. Roskam for this and other books. The book is available through several sources:


TuskaUAV talk on Aerodynamics and Propulsion

As the advisor of the TuskaUAV group, I was asked to give a 30 minute chat to the student group on the topic of aerodynamics and propulsion with a special emphasis on small unmanned aerial vehicles. The four-up double sided handout is available below. The formal talk concluded with a Q/A session both during and after the meeting. Thanks for the opportunity!

Blood Moon

20 Jan 2019, 11:20 CST.