Sunday, January 18, 2015

Comm Exercises, Lost on the Moon, and What Bernoulli Has to Say About Airfoils

By 2d Lt Karin Hollerbach, photos by 1st Lt Pat Bitz, Lt Col Juan Tinnirello, and 2d Lt Hollerbach

Comm Exercises 

2d Lt Gast and Lt Col Tinnirello,
photo by 2d Lt Hollerbach
Lt Col Juan Tinnirello, 2d Lt Matthew Gast, and 2d Lt Hollerbach deployed the HF radio for one of the evening’s comm exercises, in which we checked into the national HF net and tested our ability to communicate with radio operators far away.  With the atmospheric conditions at the time, the conclusion was – it was possible, with some difficulty.  After a number of attempts, Lt Col Tinnirello, Lt Gast, Maj Steven DeFord, and Lt Hollerbach managed to get one of us “checked in” to the net.

Lt Col Tinnirello, photo by
2d Lt Hollerbach

Subsequently, we also participated in a more local NorCal VHF net and had better luck, or at least clearer communications.  For me, as a fairly inexperienced Mission Radio Operator (MRO), it was great practice to review the appropriate communications techniques and net phraseology, which differs somewhat from how pilots are used to communicating on the radio; to get a real-life example of how difficult it can be to communicate, especially with this many radio operators checking in; and generally to see what did and did not work, under the existing conditions (atmospheric conditions, radio frequencies used, number of people participating, local setup, etc.).  We had people checking in both from radios at fixed locations and mobile units.

Aerospace Education Excellence Class #3

This week, we also had the 3rd in a series of 6 Aerospace Education Excellence (AEX) classes, led by 1st Lt Pat Bitz.  This week’s class consisted of two parts:

Lost on the Moon – NASA’s Problem Solving Scenario

In this exercise, we followed NASA’s published problem solving scenario, and compared our answers with those provided by NASA.  The scenario is as follows:

Squadron members and guests contemplating survival on the moon,
photo by 1st Lt Bitz
You are a member of a space crew originally scheduled to rendezvous with a mothership on the lighted surface of the moon. However, your ship was forced to land at a spot some 200 miles from the rendezvous point. During the landing, much of the equipment aboard was damaged.  Since survival depends on reaching the mothership, the most critical items available needed to be chosen for the 200-mile trip.  NASA provided a list of 15 items left intact and undamaged after the landing.   Our task was to rank order the items in terms of their importance in reaching the Command Module – which was going to depart from the rendezvous point in 48 hours, with or without us.  None of the 15 items seemed to enable long-term survival, so our planning was focused entirely on meeting the mothership, one way or another.

Some of us immediately overthought the problem, wondering if these were truly the ONLY 15 items we were allowed to plan on.  In other words, we had NOTHING else?  As in… not even space suits? Clothes?  Anything?  Where to draw the line in planning?  As I said, some of us (well, at least one of us) overthought the scenario.

As recommended by NASA, some of the top items on the priority list included:
  • Two 100-pound tanks of oxygen (how many people in our crew?  I do not know… was this enough for all of us for 48 hours?)
  • Stellar map of the moon’s constellations
  • 5 gallons of water
The main objective of the exercise was to develop situational awareness, while focusing in on the critical timeline (48 hours, since our chances of survival dropped off rather dramatically after that), the resources available (the 15 items plus whatever else we might have had on our bodies, as well as our own resourcefulness).  A technical understanding of our environment also helped – what do we know about the moon?  Maybe not all of us were experts on the environment found on the moon, but if we were actually going there, we should be – would a box of matches be useful on the moon?  What about a magnetic compass?  Solar-powered FM receiver-transmitter? Why or why not, given the environment, the objectives, and the timeline?

2nd Lt Eric Choate, photo by
1st Lt Bitz
For most of us, it’s unlikely we’ll be crash-landing on the moon any time soon.  However, the exercise does serve to remind us that, before flying (air crew!) or going out in the field (ground teams!), it behooves us to think through the environment we’ll be flying over or driving through, in case we need to make an unexpected stop there and have to survive.  What resources would we want to have available there, to help our chances of survival?

Bernoulli’s Principle

The second part of the class consisted of a demonstration of Bernoulli’s principle.  Pilots are all taught Bernoulli’s principle, because of its role in generating lift for the airplane.  Do you remember where it comes from and how it works?

The goal of the exercise was to create an airfoil and to make it fly with a wind applied to it, and to understand how this works.

Lt Col Tinnirello, photo by
1st Lt Bitz
Bernoulli, who was an 18th century scientist and mathematician, applied the principle of conversation of energy to the case of an ideal fluid in steady flow.  Real life isn’t “ideal” but let’s pretend for a moment.  When a fluid (including air) increases in velocity, its pressure decreases.  The increase in velocity represents an increase in kinetic energy (and we’re going to assume there’s no change in potential energy).  To conserve total energy, which is what Bernoulli’s famous equation is about (I am resisting the temptation to print an equation in this blog), it must lose pressure.

Capt Doug Ramsey, prior to takeoff,
photo by Lt Col Tinnirello

Capt Ramsey, upon successful takeoff,
photo by Lt Col Tinnirello
Airfoils, such as those of interest to pilots, provide one example of the core principle: Because of the cross-sectional shape of a wing, air moves over the airfoil faster (lower pressure) and moves under the wing more slowly (higher pressure). The difference in pressure causes the wing to rise toward the area of lower pressure.  If the air is flowing fast enough and the curvature of the wing creates enough of a difference in airspeed (i.e., pressure) above and below the wing, the wing will fly (assuming a few other conditions are true…).

In class, we made a “wing” out of a piece of file folder, attaching it to the edge of a table, and rolling it so that it had the shape (cross-section) of a tear drop. Pointing a hair dryer toward the leading edge of the wing created airflow over the wing, and resulted in the wing lifting off the table.

Stay tuned for the 4th AEX class, which we expect will be scheduled some time in February.

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