Week 1 - Field Camp 3

Week 1 has been very busy and week 2 is almost to begin.  We were lucky with the weather, but this week looks to begin the inevitable warm up that we all knew would come.  This week the geophysics group went on a field trip to get the regional setting (Monday), learned detailed surveying with the TOPCON differential GPS (Tuesday), conducted a gravity survey, and a magnetic survey (days dependent on group assignment).  The week ended on Saturday with another field trip out west to see some different formations.

The regional field trip went well and we scrambled across some slopes to see most of the section that the geologists would be mapping and be very familiar with.  As a geophysics student I was more interested in the rock properties, what methods we could differentiate them with, etc.  This trip did help put things in a big picture geologic perspective though.

The differential GPS surveying went well despite a few equipment setup issues, which were to be expected with new users.  The basic premise of the system is to leave a very precise GPS unit in place all day while another identical unit is used as a rover.  The two data sets can then be merged using the base to correct for signal attenuation by the continually changing atmosphere and other error sources.  In general sub-centimeter accuracy is achievable.  This accuracy in elevation is especially important in gravity data processing since 1m makes .3086 mGal difference in the data.  While some complain that taking 2 minutes to get a GPS fix is unreasonable I remind you that we are getting a very accurate position on an irregularly shaped rotating planet FROM SPACE... it's amazing it dosen't take longer.

The gravity survey looks at density differences in the subsurface while the magnetic survey examines differences in magnetic susceptibility.  We are interested in contracts between sediments and basement or with a dike especially in this area.  After the processing I will post some results, but I know the magnetometer went crazy when I passed over the suspected location of a large dike.  The gravity survey should also be helpful, but the gravimeter does instill a certain amount of fear in everyone since it is ~$100,000 and VERY easy to break.  Omar is modeling the magnetometer in this picture.

Finally, we went on another trip Saturday which involved me getting some nice rocks with chlorite in them for bookends from a tailings type pile in a field.  This week will be seismic week, so stay tuned for updates and pictures of our new (hopefully) 700m long seismic line!

Setting Up Equipment - Field Camp 2

The past few days have been working to get a solid radio link to downtown.  The internet signal comes up on a 5.8GHz link, is distributed over a 5.12GHz mesh around the camp, and is repeated to others on a 3GHz haul over the canyon.  Below is a picture of the stack at the top of the camp on the study hall.  The repeaters are mounted on the sides of cabins.  The current link is slow, but a new circuit will be installed downtown giving us a fast connection this week.  Also included is a picture of the geophysics server (named thor) and the associated gear.

We also worked on setting up the thumper.  This is a machine that attaches to a trailer hitch of any vehicle (truck, ATV, etc) and impacts the ground with a great force.  We use this in seismic imaging.  Normally we use a sledgehammer for small surveys, but that can get tiring.  For large, deep surveys explosives are used, this machine is a great middle ground.

As you can see there is still some work to be done.  Tomorrow the hitch will be modified and in the evening I'll be building some custom brackets and mounts for the controls and battery with Dr. Keranen.  We'll use aluminium angle iron to build most of the mounts, pictures will follow.

Tomorrow we all leave early for a regional trip to get the general geological/tectonic setting of the area.  This trip will be both geologists and geophysicists.

Setting Up Camp - Field Camp 1

This is the first in a series of posts I'll be writing about my experience at the new Bartell field camp. This camp will serve as the base for summer geology/geophysics students. Geologists will be here 5 weeks, geophysicists 3 weeks. I arrived early to setup computer equipment and help get things going around the place.



I arrived Wednesday and unloaded the server, 10 laptops, associated wiring/network components, and my field gear. More on the setup in the next post when we have internet and the rest of the network up and running.

The first night here the freshman field trip was also at camp, spending the night before departing to Dalhart, TX. We all hooked up the projector, hung a sheet, and had a movie night in the dining hall (complete with popcorn). The movie was 2012, one of the better geological comedies if you ask anybody there.

The camp site is beautiful and my cabin is at the top, affording the best view. This view comes at the price of walking a VERY steep trail, and at 6,200 ft. it's easy to get a bit winded. After a couple days it is not a problem though.




So far the weather has been very cool and rainy in town, but fairly dry up at camp. It's hit freezing at night making a sleeping bag necessary in the cabins. The peaks off in the distance are still snow covered, but today were obscured by rain shafts.




Stay tuned for a tech update tomorrow and then the arrival of the rest of the crew on Sunday. The next few weeks should brings lots of interesting field work and interesting results.


- Posted using BlogPress from my iPad

Location:Silverado Ct,Cañon City,United States

Surviving a Crash - The Black Box Then and Now

After an airliner crashes there is a search for survivors (of which you have about a 1:100 chance of being among) and the search for the ever important in infamous 'black box'.  The black box records critical flight data that helps accident investigators determine what caused the crash and if there are problems with the airplane model that need to be corrected.  This was the case of the stripping jack screw in the tail of the MD-83 that caused the crash of Alaska Air 261 in 2000.  The black box has undergone many transformations over the years, but it has always had to be a durable machine that can preserve data through  the dramatic forces of a crash, water immersion, and inferno like fires of jet fuel and airframe materials.

Some of the earliest flight data recorders used photographic film rolls that had lines exposed on them by light reflected of sets of mirrors.  The mirrors were deflected different amounts according to aircraft parameters resulting in a 'strip chart' on the film.  This was easy to develop, but was only a one time use as the film had to be replaced after exposure.  The first data recorders just recorded a few simple channels of data and were common only on test flights due to their cost.

Later black boxes, like the one featured in the video below, used metal strips with the data scratched into the metal by a sharp stylus.  These records survived the fire and shock much better than film, but were still single use.  Keep in mind this is still all done with 'old fashioned' technology as there was no solid state memory in these days.  The next step was voice recording.  What were the pilots talking about before the crash?

Video on Analog Recorder

In the 1950's spy gadgets were the rage in the intelligence community and they required some of the same properties that aircraft flight data recorder designers desired: compact, durable, simple.  Wire recording was the answer.  Magnetically encode data on a spool of wire and use a ground based playback/decoding system.  It wasn't long before both the flight data and the cockpit voice data were being recorded on the same wire reel.  This reel could be erased and used again.

Modern flight data recorders and required to store at least 88 parameters by law (US) and they are solid state.  There are a few cases where the data has been unreadable to due destruction of the unit, but new units that propel themselves from the crash may solve that problem.  The new recorders also transmit a beacon signal making them easier to find for about a month.  Some of the smart units are even capable of observing when inputs are changing rapidly and collecting data more often as this is when things are likely to go wrong.

The purpose of this trip through the history of the flight data recorder was not only to show the evolution of a remarkable and very useful device, but to show how engineering problems can be solved without a microchip.  Are the recorders now better than those of the film days? Of course, but it required some out of the box thinking to build the mechanical recorders of the early days of aviation.

Progress on Ultrasonic Mapper

My last post was on the idea, brainstorming, and basic setup of a ultrasonic mapper intended for cave passages.  This post is an update on the prototype that is running now and will hopefully be tested relatively soon when a bit more hardware mounting has been done.

Attached are several photos of the current state of the system, a simple plexiglass mount was constructed to attach the servo and sounder to an old tripod.  This mount will be stronger on a final version and detachable from the tripod.  This is just a proof of concept prototype.

Since servos only rotate 180 degrees the final model will use two sounders opposed to each other to collect a full 360 degree profile.  This means a similar connector (5-pin mic style) will be used with two units mounted in one case, or it may be possible to go with a more sophisticated sounder.  Keep in mind that the point of the whole project is to construct the profiler on a student shoestring budget.  

Below is an 'image' collected.  The vertical line on the right side is the back of an office chair and the feature on the left is the back and seat of a couch.  This was scanned rather slowly over about 40 seconds with many pings averaged out to reduce error.

Since I collected these images I have implemented an intelligent algorithm that makes a quick three ping assessment and based upon the results it will move to the next position or ping up to an additional fifty times to reduce the uncertainty.

The next step will be to make an intelligent scanning rate method that will scan with lower resolution over smooth surfaces and slow down over surface features.  Hopefully the whole scan can be a 15-30 second ordeal allowing quick mapping of passages.

Holiday Engineering Project - Beginning an Ultrasonic Mapper

Over the Thanksgiving break I decided to tackle a small engineering project that has been on my mind for the past month or so.  The basic idea was inspired by learning about Bill Stone's underwater cave mapping system (Stone Aerospace).   It is a relatively complex system constructed by more funding that a college student has at his/her disposal.  Being a caver myself I decided to build a much simpler and cheaper version for both above and below ground mapping.

Since this project is not too large it should be easily constructed over a few weekend hacking sessions, and over the last day the first steps have taken place. The machine uses and Arduino Uno as an interface between a computer and the real world.  While it is true that it would be possible to make a self-contained unit that would store data on a flash drive and maybe even display initial results on some simple display, I opted out of that option for cost and control concerns.  It should be simple to make a simple GUI that allows a netbook to control the setup very nicely and process the data real time.  

Above the basic layout from my notebook is shown.  The ultrasonic ranger (an SRF05) is attached to a rotating mount to sweep through the space around it.  In the initial prototype stages I'm using a simple RC servo since I have it on hand.  Servos only sweep close to 180 degrees to avoid bending control links on models.  While continuous rotation servos are made, they have no position feedback which does not allow accurate positioning of the servo.  It would be possible to use multiple rangers so 180 degrees is enough rotation, but it will be more economical to switch to a slow geared motor with an encoder (maybe a quadrature rotary encoder?) to detect the position as the unit slowly sweeps the space around it.  

Also pictured is the Arduino board and the range finder mounted in a custom case built this afternoon (the window added allows the ping LED to be seen inside the case to confirm the link).  Modification of the PCB and mounting hardware was required.  CAT5e cable along with 4-pin radio mic connectors are used for the power, ground, echo, and trigger pins.  The ranger has a built in PIC controller to pulse the output with a length of the echo time.  The unit seems to range effectively up to about 17 feet.  

While I don't know the accuracy at large distances, or the spread of the 'beam' with the increasing path length, some simple tests should help sort that out.  Currently I've written the interface on the Arduino in C, which will listen for commands over the USB connection.  It this executes those commands (such as move servo, get distance, etc) and returns the appropriate values if necessary.  The communication is asynchronous and not really 'handshaking', but using startbits there is some error checking involved.  

The control from the computer is in the form of a python script that takes easy user input and converts it to the short serial commands in the home-made quick transfer format in the Arduino C code.  Currently it moves the servo and returns distances in cm.  At distances less than 30 cm results seem to be accurate to about 2-5mm.  

The next steps include mounting everything up to get 180 degree scans produced, assessing the accuracy and noise limits of the unit.  I also plan to implement a scanning algorithm that scans more quickly over plan surfaces and slows down over more interesting surfaces.  It will also throw out false returns, which could be due to a range folding issue in large spaces (I have not done anything past back of the envelope on if the signal is strong enough to cause a range folding issue).  A leveling mechanism (manual or automatic) would be nice for field applications.  If this were to be used in mapping a tunnel some kind of simple inertial navigation system with a combination of gyros and accelerometers could be used.  These are all for future development and future posts.  

Have a happy and safe Thanksgiving! 

New Nuclear? - The Traveling Wave Reactor

For a few decades the debate has raged: are you pro or anti-nuclear power?  While nuclear power is a fantastic source of energy it can be dangerous and produces waste that we are currently hard pressed to store.  Movies such as 1979's 'The China Syndrome' have aided public fear of nuclear power once the new rubbed off in the 1960's.  Since the Three Mile Island accident, there have been no new reactors built in the US.  What if there were a new kind of reactor that was safer, cleaner, and used our stockpile of waste as fuel?

Lately there has been some press on the traveling wave reactor (TWR).  A spinoff from a Bill Gates backed company called TerraPower is working with the design, but it's really nothing new.  The TWR has been studied since the late 1950's and there are several articles in the literature that describe the theory of the units.

The principle of operation is to use depleted uranium and spent fuel that would traditionally be stashed away in a repository to fuel the reaction.  The reaction starts with ~10% enriched uranium at one end of the fuel column.  As a chain reaction takes place in the critical zone it converts material downstream into fissile material which is then the new critical zone.  Basically the critical zone that is actually producing the power moves down the fuel column with time.  This means if we were to look at a movie of where the power is produced through time we would see a soliton (wave that travels maintaining its shape) pass through the fuel column over a period of ~60 years.

The advantages of such a reactor include using depleted stocks of uranium and not producing material that could proliferate into atomic weapons.  As with every process governed by the laws of physics there is no free lunch.  Currently the reactor is a 'paper reactor'; no prototype has ever been built, though many have been run as numerical simulations.  The unfortunate thing is reactors often don't live up to their numerical ideal models and that could push the TWR into the realm of being currently non-economical.  While the units are smaller and safer they do produce less power and would require a significant investment to start building in an industry that is currently set in its ways.

In reality, the reactors sound fantastic, but I don't plan on seeing them anytime soon as the money for research, even energy related is just not there.  To get a reactor from paper to common production takes decades and often includes unforeseen problems.  Full scale reactors of the fission sort built in the early days had many kinks to work out.  Some would startup and then mysteriously shutdown by themselves; it turns out this was xenon poisoning, something that was handled poorly in the reactor design.  Other reactors such as the SL-1 were thought to be safe, but engineering flaws caused an accident and ended up impaling a man to the roof of the containment building with a control rod.  It has taken decades to get the current reactor technology to where it is.  While remaining optimistic about the TWR design, it is sadly not ready to swoop in and help us in the energy crisis.

TerraPower Website