Thanks Team


Quote of the Day

Thoroughly conscious ignorance is the prelude to every real advance in science.

James Clerk Maxwell

Figure 1: A Gift From A Very Fine Engineer. Thanks Becky.

Figure 1: A Gift From A Very Fine Engineer. Thanks, Becky.

I have now started on my next employment adventure. I can only say thanks to the wonderful team of people that I leave behind. They created the products that allowed the Fiber-To-The-Home (FTTTH) market to flourish. Tens of millions of FTTH products are now manufactured every year by companies around the world. These products are amazing in that for very low-cost they can contain such diverse technology: high-speed digital electronics, FPGAs, RF video,  telephony, battery backup, and wireless. The team can be proud of what they have done. You succeeded where many others failed.

Figure 1 shows something that is very special to me. I have stood while working for many years on a beat-up old plastic mat that I referred to as my "anti-cynicism mat." I always told folks that while I was on this mat, there would be no cynicism. I also warned certain people that they should never stand on my mat because their feet burn would through it. On my last day, an engineer presented me with the mat shown in Figure 1. It will occupy a place of honor in my new garage/workshop, and I will cherish it.

Posted in Personal | Leave a comment

Short-Term Solution for Furnace Condensate Freezing Problem


Quote of the Day

Politicians complaining about the press are like sailors complaining about the sea.

— Winston Churchill

Figure 1: My Short-Term Solution to Stop Condensate from Freezing in My Septic System.

Figure 1: My Short-Term Solution to Stop Condensate from Freezing in My Septic System.

Minnesotans have endured a cold winter with relatively little snow, a situation that causes the ground to freeze deeper than expected. In northern Minnesota, we plan for 60 inches of frost depth, but this year the frost has gone much deeper. For those cabins with condensing furnaces, this extra frost depth has resulted in many frozen septic lines. This winter, I have frozen both my cabin and garage septic lines. The problem has been pervasive enough that the local newspapers have covered it (example).

As I have discussed in a previous post, these furnaces generate ~1 gallon of condensate for every 100,000 BTUs of propane burned. On the coldest days, my garage furnace produces 5 gallons of condensate per day, which means that I have a constant trickle of water flowing into my garage septic line. Unfortunately, this flow rate is so small that the water only slowly moves through the pipes. This slow movement of the condensate means that it can freeze, resulting in a clogged septic line.

I first tried a 1-liter condensate pump, which stores 1-liter of condensate before putting it out in a surge. The idea is that 1-liter slug of water will be less likely to freeze than a trickle. Unfortunately, a 1-liter slug of water was not large enough, and it froze in the pipe.

Figure 1 shows the approach that worked. I have the 1-liter condensate pump fill a 110-litter tub. This tub contains a sump pump that puts out a surge of about 40-liters. This surge was sufficient that it did not freeze. Both my garage and my home have the same setup. I should mention that I chose to use a vertical-float switch rather than a tethered-float switch to eliminate the possibility of the tether catching on an obstruction.

Long-term in the garage, I will pound out the concrete floor and put in a sump basket. The sump will be lower than my furnace, which will allow me to use gravity to feed the sump with condensate, eliminating the need for the 1-liter condensate pump. I will put the sump pump in the basket, which will then pump 40-liter surges into my floor drain. Unfortunately, I cannot install a sump pump in my house because its concrete floor contains in-floor heating tubes. For the house, my short-term solution is also my long-term solution.

The following video shows how to install a sump pump in a concrete floor.

Figure 2: Good Video On Installing a Sump Pump in a Concrete Floor.
Posted in Construction | Leave a comment

Number of Space Travelers


Quote of the Day

If you wanna hire great people and have them stay working for you, you have to let them make a lot of decisions and you have to be run by ideas, not hierarchy. The best ideas have to win, otherwise good people don't stay.

— Steve Jobs

Figure 1: Michio_Kaku_(Wikipedia)

Figure 1: Michio Kaku (Wikipedia)

I was watching physicist Michio Kaku on CSPAN last Sunday night talking about his new book The Future of Humanity. I like watching authors speak on CSPAN because they provide an extended interview format for authors. In this interview, the interviewer Brian Lamb mentioned a factoid as part of a question that I thought was worth investigating.

You say in your book that 544 humans who have been in space and that 18 of those have died. What do those numbers mean to you?

Table 1: Space Travelers By Country.
United States333
Soviet Union73
United Kingdom5
South Africa1
Costa Rica1
Saudi Arabia1
South Korea1
East Germany1
Grand Total558

Of course, the number of people who have been in space is changing with every flight into orbit, and this type of fact is guaranteed to be obsolete immediately after publication. I thought I would investigate the number of people who have been in space and how many have died as part of their mission. These numbers were easier to verify than I would have expected.

The Wikipedia has a page that contains a comprehensive list of the people who have been in space. Using Power Query, I downloaded this list, did some routine data clean up, and generated the data summary shown in Table 1. As of this date, 558 people have gone into space. You can see that the US has put the most people into space, which is most likely because the space shuttle could carry more people than the Soyuz spacecraft.

The Wikipedia also has a page with a list of those who have died on space missions, not all of which reached space. As with Table 1, I downloaded the data, cleaned it up, and generated Tables 2 and 3. Table 2 contains the name of those who died going on space missions, and Table 3 shows the number of space fatalities by vehicle. For those who are interested, my Excel workbook and data are here.

As an aside, I watched a TV show years ago that was hosted by Dr. Kaku in which he was the guest of a US Army unit. The US Army drafted Dr. Kaku during the Vietnam War, which ended before he completed his infantry training. During his stay with this unit, he demonstrated some physics while wearing a US Army uniform. You could tell that both Dr. Kaku and the soldiers enjoyed his visit. He seems like a good man.

Table 2: Space Fatalities. Table 3: Space Fatalities By Vehicle.
Vladimir KomarovSoyuz 1
Georgy DobrovolskySoyuz 11
Viktor PatsayevSoyuz 11
Vladislav VolkovSoyuz 11
Christa McAuliffeChallenger
Dick ScobeeChallenger
Ellison OnizukaChallenger
Gregory JarvisChallenger
Judith ResnikChallenger
Michael J. SmithChallenger
Ronald McNairChallenger
David M. BrownColumbia
Ilan RamonColumbia
Laurel ClarkColumbia
Kalpana ChawlaColumbia
Michael P. AndersonColumbia
Rick D. HusbandColumbia
William C. McCoolColumbia
Soyuz 11
Soyuz 113
Shuttle Challenger7
Shuttle Columbia7
Grand Total18
Posted in Space | Leave a comment

Colonoscopy Notes


Quote of the Day

So, in the face of overwhelming odds, I'm left with only one option: I’m going to have to science the shit out of this.

— Mark Watney, The Martian. I love this quote.

Figure 1: Appendix Opening. This is not mine. (Source)

Figure 1: Appendix Opening. This is not a photo of mine. (Source)

I had a colonoscopy yesterday, and it was a great learning experience. I am fortunate that the anesthetic they gave me had little effect, and the doctor was open to answering questions from an inquisitive patient. It probably helped that the doctor was a mechanical engineer that decided to go into medicine – we had lots to talk about. I found it funny when he mentioned that he did not like engineering work on optics – of course, much of my life has been spent designing optics. In the course of this doctors daily work, he uses optics all day long. His gear was from Olympus, some of which is manufactured in Brooklyn Park, Minnesota, which is near my home. Minnesota is known for its medical technology.

Here are the notes I took on the procedure.

  • What is the basic colon inspection procedure

    The doctor told me that they put the probe in all the way to the appendix without really doing any observations. The colon sort of hugs the probe and you cannot see much. Once the probe gets to the appendix, they inflate the colon with CO2 and do their inspection on the way out.

  • How long is the colon?

    Around four feet long – he said the length is correlated with your height. Here is a good image of the colon. You can see the appendix at the beginning of the colon.

    Figure 2: Colon Structure.

    Figure 2: Colon Structure and Endoscope Detail. (Source)

  • Why is carbon dioxide used to inflate the colon?

    While in my upper colon, the doctor told the nurse he wanted to use CO2 to inflate that section. I asked the doctor why CO2 instead of air. He said that CO2 is absorbed by the colon into the bloodstream very quickly and you just breath it out. Air is not so quickly absorbed and, if used, would leave you feeling bloated after the procedure.

  • Has the doctor ever seen an infected appendix?

    He said that he has seen two during his years of practice (I would put the doctor in his late 40s). He said that an infected appendix is no issue as long as it can drain into the colon. An infected appendix will eventually heal as long as it can drain. You get into trouble when an infected appendix cannot drain and it ruptures.

  • I was floored at how much the technology has improved since my last colonoscopy.

    My last colonoscopy was 9 years ago. The screen images back then were low resolution and black and white. These were high-res and in color. The level of detail was amazing. He controlled how the probe moved using a hand control that reminded me of the old hand controls used for remote manipulators.

  • I have seen two types of polyp removal.

    Nine years ago, I had a mushroom-room shaped polyp and it was removed with a lasso-type instrument that both cut and cauterized the polyp. The doctor extracted the polyp, put it into a bag, and sent it for tests (no issue). I had three very small polyps this time. A very small pliers-like instrument was inserted and he just grabbed the polyps, twisted them to remove them, bagged them, and sent them in for tests.

  • Do people ever come in that were not "cleaned out"?

    I was told it happens all the time. They have to go back home and take more laxatives. They colon has to be cleaned out for the doctors to do their work. Personally, I cannot imagine someone following the procedure and not being cleaned out.

Posted in General Science | 3 Comments

Estimating Component Junction Temperature Using Psi-JT


Quote of the Day

Unfortunately, although the electrical and thermal differential equations are analogous, it is erroneous to conclude that there is any practical analogy between electrical and thermal resistance. This is because a material that is considered an insulator in electrical terms is about 20 orders of magnitude less conductive than a material that is considered a conductor, while, in thermal terms, the difference between an 'insulator' and a 'conductor' is only about three orders of magnitude. The entire range of thermal conductivity is then equivalent to the difference in electrical conductivity of high-doped and low-doped silicon.

Clemens J. M. Lasance, Thermal Engineer for Philips. As an electrical engineer, I use lumped parameter models with confidence because I know that my insulators really insulate. The thermal engineer does not have that luxury.


Figure 1: ADN4612 Pin Diagram.

Figure 1: ADN4612 Pin Diagram. (Source)

An engineer stopped by my cube today and asked a question about how to estimate the junction temperature of a part on a circuit card that may have an over-temperature problem. Using the common thermal resistancesJA and θJC), he was obtaining nonsensical results. This problem was a good illustration of the difficulties present in estimating Integrated Circuit (IC) junction temperatures using the commonly supplied thermal resistances.

I will show how I went about estimating the junction temperature of this device and why the methods usually used can provide unrealistic results. My results are estimates, but show that the junction temperature of the ADN4612 is significantly lower than its maximum rating and does not warrant any further analysis. If it were close, I would bring in a mechanical engineer to perform a more detailed thermal analysis.


Problem Statement

With respect to ADN4612's junction temperature in this application, the following characteristics are relevant :

      • power dissipation: PD = 3.5W
      • top of case temperature: TTop = 105°C (measured with thermocouple)
      • via temperature under part: TPCB = 82°C (measured with thermocouple by a via under the part)
    • package: 88-pin Lead Frame Chip Scale Package (LFCSP )
    • junction-to-ambient thermal resistance: θJA = 24°C/W
    • junction-to-case thermal resistance: θJC = 1.7°C/W
    • maximum allowed junction temperature: TMax = 125°C/W

Issues Using Common Thermal Resistances

IC specifications commonly give two thermal resistances, θJA and θJC. These specifications are useful, but frequently misused. The key to their proper use is to understand how they are measured. θJA is measured on a standard PCB as defined by JEDEC JESD51-2. Since every circuit board design is different, θJA is only useful for comparing the relative thermal performance of different packages. It is not useful for predicting component temperatures on a specific PCB and environment that are different from the test configuration.

θJC is measured in a special jig that forces all the heat through some area on the IC's case. For most ICs, the heat is forced through the top of the case. This makes sense if you are going to put a heat sink on the part and your plan is for most of the heat to go out the top. In the case of the ADN4612, it has a copper slug on the bottom of the part. θJC for the ADN4612 is measured by forcing all the heat through the bottom of the part and into the PCB. Again, this situation is not what actually occurs – the part will dissipate heat into the environment through multiple paths (bottom, top, leads).

Ideally, we would thermal models that provided use thermal resistances for all the possible paths for heat to leave a part. These models, called compact thermal models, do exist, but most vendors do not supply all the required parameters (e.g., Figure 2).

Figure 2: Example of a Compact Thermal Model for an IC (also known as Delphi model). (Source)

Figure 2: Example of a Compact Thermal Model for an IC (also known as Delphi model). (Source)

While compact thermal models for every part would be great, most ICs are not going to have temperature issues. An electrical engineer wants a rough estimate of the junction temperature to determine if he needs to bring in a mechanical engineer for a more detailed analysis of a specific part. For this approximate type of work, I prefer to use Psi-JT (ΨJT). This parameter is NOT a thermal resistance and is referred to as a thermal characteristic. It also is defined in JESD51-2. The standard allows for making a simple linear estimate of a part's junction temperature in a typical application using Equation 1.

Eq. 1 \displaystyle {{T}_{J}}={{T}_{{Top}}}+{{\Psi }_{{JT}}}\cdot {{P}_{D}}


  • TJ is the IC junction temperature.
  • TTop is the measured case temperature on the top of the part (the easiest place to get a measurement).
  • PD is the part power dissipation.
  • ΨJT is the thermal characteristic between the junction and the top of the IC case.

Unfortunately, Analog Devices did not provide ΨJT on their datasheet. This is where a bit of digging comes in …


Obtaining ΨJT

Because the datasheet did not contain ΨJT, I started using my usual search engine to do some specification hunting. It turns out that I did find a couple of references to ΨJT for similar packages:

  • an Analog Devices forum discussion on the 24-pin version of this package, which gave a 0.9°C/W for ΨJT.
  • an Analog Devices forum discussion on the 20-pin version of this package, which gives a simulated value of 0.27°C/W for ΨJT. The difference between a simulated value and measured value like this does not shock me at all.

We can also calculate an approximate ΨJT value using the method I outline on this blog post (Figure 3).

Figure: 3: ΨJT Estimate Using Approximation.

Figure: 3: ΨJT Estimate Using Approximation.

For my calculations below, I will assume the worst-case ΨJT  value I found of 0.9 °C/W.

As a cross-check, I can also make an approximation using ΨJV: junction-to-PCB via thermal characteristic, which I obtained from this chart (Figure 4).



Figure 5 shows my calculations to estimate the junction temperature for the ADN4612 using two different parameters: ΨJT and ΨJV.

Figure 5: Two Ways to Estimate Junction Temperature.

Figure 5: Two Ways to Estimate Junction Temperature.


I view my two estimates of junction temperature (108°C and 103°C) as reasonable close for this type of approximate calculation. Both methods show that the part is not operating near its junction temperature limit of 125°C, which is what I needed to know.

I do wish the semiconductor vendors would provide designers with better thermal data and models that would make applying their parts easier. I should not have to search the web and crawl around forum discussions in order to intelligently use a vendor's part.

Posted in Electronics | Leave a comment

Near-Earth Asteroid Size Estimate Example


Quote of the Day

Knowledge consists in the search for truth ... it is not in the search for certainty.

Karl Popper. I have always found his work on the philosophy of science interesting. He is best known for his belief that scientific concepts must be falsifiable.

Figure 1: Deceptive Image of an Asteroid Passing Extremely Close to the Earth. (USA Today)

Figure 1: Deceptive Image of an Asteroid
Passing Extremely Close to the Earth.
(USA Today)

Newspapers often talk about Near-Earth Objects (NEOs) that are passing "close" to the Earth. To increase the number of clicks, the articles usually include an image implying that the NEO is very close to the Earth. I find these articles a bit irritating.

This morning at 2:53AM Eastern Standard Time, asteroid 2017 VR12 had its closest point of approach to Earth, which was ~4x the distance from the Earth-to-Moon. It is not considered an impact threat. USA Today published an article that included Figure 1, which implies a very close pass. That is simply not correct.

To give you some perspective, let's examine Figure 2, which is a picture of the Earth-Moon system as seen by an asteroid-sampling spacecraft called OSIRIS-REx.

Figure 1: Earth-Moon System.

Figure 2: Earth-Moon System from 3 million miles away. The Moon is 60 Earth radii distant from the Earth. Asteroid 2017 VR12 is ~4x this distance from the Earth at its closest point. (NASA)

The article also mentioned that the asteroid "could be as big as Empire State Building". I thought I would show how you can do that calculation for yourself (Figure 3). The Empire State Building is 443.2 meters tall, which is roughly the maximum equivalent spherical diameter  of 2017 VR12. The uncertainty in size is large because the albedo of asteroids is so variable.

Figure 3: Calculations That Show 2017 VR Could Have an Equivalent Radius Similar to the Empire State Building.

Figure 3: Calculations That Show 2017 VR Could Have an Equivalent Radius Similar to the Empire State Building.

US Today Article Minor Planet Data University of Iowa Astronomical Symbols Table of Asteroid Sizes
Posted in Astronomy | Leave a comment

Cabin Is Complete


Quote of the Day

The young man knows the rules but the old man knows the exceptions.

— Oliver Wendell Holmes Jr.

Figure 1: View of My Cabin as I Walk From My Garage.

Figure 1: View of My Cabin as I Walk From My Garage.

My cabin construction project is now complete. My wife and I are now beginning to furnish our new home, which will take some time. I continue to work on the garage construction myself, which will take until sometime in May to finish. Overall, our planning was good and there were no major surprises. The one area of difficulty that I did not fully appreciate is the remoteness of the site. Before you go to the site, you need to plan out every possible tool or part that you will need while there.

This is a huge, multi-year project that I am relieved to say the house portion is complete – the garage still needs a bit of work. My plan is to retire at this site in 5 to 10 years and spend my time designing hardware, writing software, and building furniture. I hope that my granddaughter will get to spend quite a bit of time here with her grandparents.

Some basic home details:

  • 2100 square feet
  • 2 floors
  • 3 bedrooms
  • 2 bathrooms
  • no basement, concrete slab on ground with in-floor heating
  • insulated with closed-cell foam
  • heated with propane (the only form of fuel that I could get locally)
  • designed for handicapped access (I want to live there when I am old)
    My wife and I can live on the ground floor and have our guests stay on the upper floor.

Some additional photos.

Figure 2: House View From Driveway.
Figure 3: Kitchen View.
Figure 4: Living Room View.
Figure 5: Master Bedroom (2nd Floor).
Figure 6: View of Stairway and 2nd Floor Hall (Bedroom on Left).
Figure 7: Handicap Access Shower (1st floor).
Figure 8: Living Room Fireplace.
Figure 9: Second View of Master Bedroom (2nd floor).


Posted in Construction, Personal | 10 Comments

Minnesotans In the Olympics


Quote of the Day

Yes, I should have given more praise.

Sir Winston Churchill, quoting the reply of the then elderly Duke of Wellington when a friend asked him, 'If you had your life over again, is there any way in which you could have done better?'

Figure 1: People Curling in Northern Minnesota. (Source)

Figure 1: People Curling in Northern Minnesota. (Source)

I spend a lot of time in northern Minnesota now that I have a home there. I have been surprised as to how popular curling is in the area (Figure 1). The US curling team at the 2018 Olympics is dominated by people from northern Minnesota. I also notice that there are quite a few Minnesotans participating in the games' other sports – the numbers are large enough that the New York Times has even written an article called "Team USA? More Like Team Minnesota" on the topic (PDF of the article). Our state does not have a huge population, ~5 million, and most of that population is concentrated around Minneapolis and St. Paul. The northern part of the state is only sparsely populated as it is covered with national forests and wilderness areas.

To understand the participation of Minnesotans in the Olympics, I grabbed an Excel file from the US Winter Olympic Team web site  and generated a couple of pivot tables, which I show below. My workbook is include here.

Figure 2: Top Ten Home States for US Olympic Athletes.

Figure 2: Top Ten Home States for US Olympic Athletes.

California contributes the most athletes to this year's Olympic team, followed by Colorado and Minnesota (Figure 2). Since Minnesota has no mountains, alpine events are not our strength – though Lindsey Vonn is from St. Paul and first skied here at Buck Hill.

The big snow sports here are hockey, cross-country skiing, and curling. You see this reflected in the athletes we send to the Olympics (Figure 3). Biathlon is a combination of cross-country skiing and shooting, which are two common passions here.

At this point, the Minnesota athletes have brought home medals in curling, hockey, and cross-country.

Figure 3: Minnesota Participation in Olympic Sports.

Figure 3: Minnesota Participation in Olympic Sports.

For my family, skating and hockey became a passion first for my children and then for me – this is the reverse for most families. My dad was a hockey player and ice dancer, but I never had any interest early on in either sport. My children saw the movie The Mighty Ducks, and they became driven to skate. I learned to skate and play hockey on the kiddie ponds next to the rinks where my children were practicing.

Table of Athletes

I included a subset of the Olympic spreadsheet here for any general searching that I want to do.

First NameLast NameGenderDisciplineAge (As of 2/8/18)HometownHome State
StaceyCookFAlpine Skiing33Mammoth LakesCalif.
BreezyJohnsonFAlpine Skiing22Jackson Wyo.
Tricia ManganFAlpine Skiing20BuffaloN.Y.
MeganMcJamesFAlpine Skiing30Park CityUtah
AliceMcKennisFAlpine Skiing28New CastleColo.
AliceMerryweatherFAlpine Skiing28HinghamMass.
LaurenneRossFAlpine Skiing29BendOre.
MikaelaShiffrinFAlpine Skiing22Eagle-VailColo.
ResiStieglerFAlpine Skiing32Jackson Wyo.
LindseyVonnFAlpine Skiing33VailColo.
JacquelineWilesFAlpine Skiing25PortlandOre.
BryceBennettMAlpine Skiing25Tahoe CityCalif.
TommyBiesemeyerMAlpine Skiing29KeeneN.Y.
DavidChodounskyMAlpine Skiing33Crested ButteColo.
RyanCochran-SiegleMAlpine Skiing25StarksboroVt.
MarkEngelMAlpine Skiing26TruckeeCalif.
TommyFordMAlpine Skiing28BendOre.
JaredGoldbergMAlpine Skiing26Salt Lake CityUtah
TimJitloffMAlpine Skiing33RenoNev.
NolanKasperMAlpine Skiing28WarrenVt.
TedLigetyMAlpine Skiing33Park CityUtah
WileyMapleMAlpine Skiing27AspenColo.
StevenNymanMAlpine Skiing36SundanceUtah
AndrewWeibrechtMAlpine Skiing32Lake PlacidN.Y.
ClareEganFBiathlon30Cape ElizabethMaine
MaddiePhaneufFBiathlon22Old ForgeN.Y.
LowellBaileyMBiathlon36Lake PlacidN.Y.
TimBurkeMBiathlon36Lake PlacidN.Y.
SeanDohertyMBiathlon22Center ConwayN.H.
LeifNordgrenMBiathlon28Marine Minn.
LaurenGibbsFBobsled33Denver Colo.
JamieGreubel PoserFBobsled34NewtownPa.
ElanaMeyers TaylorFBobsled33DouglasvilleGa.
JustinOlsenMBobsled30San AntonioTexas
CarloValdesMBobsled28Newport BeachCalif.
NathanWeberMBobsled31Pueblo WestColo.
EvanWeinstockMBobsled26Las VegasNev.
SadieBjornsenFCross-Country Skiing28WinthropWash.
RosieBrennanFCross-Country Skiing29AnchorageAlaska
SophieCaldwellFCross-Country Skiing27PeruVt.
JessieDigginsFCross-Country Skiing26AftonMinn.
RosieFrankowskiFCross-Country Skiing26MinneapolisMinn.
AnnieHartFCross-Country Skiing25StillwaterMinn.
KaitlynnMillerFCross-Country Skiing26ElmoreVt.
CaitlinPattersonFCross-Country Skiing28CraftsburyVt.
KikkanRandallFCross-Country Skiing35AnchorageAlaska
IdaSargentFCross-Country Skiing30CraftsburyVt.
LizStephenFCross-Country Skiing31East MontpelierVt.
ErikBjornsenMCross-Country Skiing26WinthropWash.
PatrickCaldwellMCross-Country Skiing23LymeN.H.
SimiHamiltonMCross-Country Skiing30AspenColo.
LoganHannemanMCross-Country Skiing24FairbanksAlaska
ReeseHannemanMCross-Country Skiing28FairbanksAlaska
NoahHoffmanMCross-Country Skiing28AspenColo.
TylerKornfieldMCross-Country Skiing27AnchorageAlaska
AndyNewellMCross-Country Skiing34ShaftsburyVt.
ScottPattersonMCross-Country Skiing26CraftsburyVt.
KarenChenFFigure Skating18FremontCalif.
MadisonChockFFigure Skating25Redondo BeachCalif.
MadisonHubbellFFigure Skating26SylvaniaOhio
MiraiNagasuFFigure Skating24ArcadiaCalif.
AlexaScimeca KnierimFFigure Skating26AddisonIll.
MaiaShibutaniFFigure Skating23Ann ArborMich.
BradieTennellFFigure Skating20CarpentersvilleIll.
EvanBatesMFigure Skating28Ann ArborMich.
NathanChenMFigure Skating18Salt Lake CityUtah
ZacharyDonohueMFigure Skating27MadisonConn.
ChrisKnierimMFigure Skating30San Diego Calif.
AdamRipponMFigure Skating28Los AngelesCalif.
AlexShibutaniMFigure Skating26Ann ArborMich.
VincentZhouMFigure Skating17Palo AltoCalif.
MaddieBowmanFFreestyle Skiing24South Lake TahoeCalif.
AshleyCaldwellFFreestyle Skiing24AshburnVa.
CarolineClaireFFreestyle Skiing18Manchester CenterVt.
AnnalisaDrewFFreestyle Skiing24AndoverMass.
TessJohnsonFFreestyle Skiing17VailColo.
JaelinKaufFFreestyle Skiing21AltaWyo.
DevinLoganFFreestyle Skiing24West DoverVt.
KeatonMcCargoFFreestyle Skiing22TellurideColo.
KileyMcKinnonFFreestyle Skiing22MadisonConn.
MadisonOlsenFFreestyle Skiing22Park CityUtah
MorganSchildFFreestyle Skiing20PittsfordN.Y.
BritaSigourneyFFreestyle Skiing28CarmelCalif.
DarianStevensFFreestyle Skiing21MissoulaMont.
MaggieVoisinFFreestyle Skiing19WhitefishMont.
CaseyAndringaMFreestyle Skiing22BoulderColo.
AaronBlunckMFreestyle Skiing21Crested ButteColo.
MacBohonnonMFreestyle Skiing22MadisonConn.
AlexFerreiraMFreestyle Skiing23AspenColo.
NickGoepperMFreestyle Skiing23LawrenceburgInd.
AlexHallMFreestyle Skiing19Park CityUtah
GusKenworthyMFreestyle Skiing26TellurideColo.
JonLillisMFreestyle Skiing23RochesterN.Y.
EricLoughranMFreestyle Skiing22PelhamN.H.
TroyMurphyMFreestyle Skiing25BethelMaine
EmersonSmithMFreestyle Skiing21DoverVt.
McRaeWilliamsMFreestyle Skiing27Park CityUtah
BradleyWilsonMFreestyle Skiing25ButteMont.
DavidWiseMFreestyle Skiing27RenoNev.
TorinYater-WallaceMFreestyle Skiing22BasaltColo.
CaylaBarnesFIce Hockey19EastvaleCalif.
KaliFlanaganFIce Hockey22BurlingtonMass.
HaleySkarupaFIce Hockey24Rockville Md.
MeganKellerFIce Hockey21FarmingtonMich.
EmilyPfalzerFIce Hockey24BuffaloN.Y.
NicoleHensleyFIce Hockey23LakewoodColo.
KendallCoyneFIce Hockey25Palos HeightsIll.
HannahBrandtFIce Hockey24Vadnais HeightsMinn.
DaniCameranesiFIce Hockey22PlymouthMinn.
KellyPannekFIce Hockey22PlymouthMinn.
LeeSteckleinFIce Hockey23RosevilleMinn.
AmandaKesselFIce Hockey26MadisonWis.
GigiMarvinFIce Hockey30WarroadMinn.
SidneyMorinFIce Hockey22MinnetonkaMinn.
MaddieRooneyFIce Hockey20AndoverMinn.
KaceyBellamyFIce Hockey30WestfieldMass.
JocelyneLamoureux-DavidsonFIce Hockey28Grand ForksN.D.
MoniqueLamoureux-MorandoFIce Hockey28Grand ForksN.D.
AmandaPelkeyFIce Hockey24MontpelierVt.
HilaryKnightFIce Hockey28Sun ValleyIdaho
MeghanDugganFIce Hockey30DanversMass.
BriannaDeckerFIce Hockey26DousmanWis.
AlexRigsbyFIce Hockey26DelafieldWis.
BrianGiontaMIce Hockey39RochesterN.Y.
ChrisBourqueMIce Hockey32North ReadingMass.
MattGilroyMIce Hockey33BellmoreN.Y.
JordanGreenwayMIce Hockey20CantonN.Y.
JohnMcCarthyMIce Hockey31Boston Mass.
JamesWisniewskiMIce Hockey33CantonMich.
DavidLeggioMIce Hockey33BuffaloN.Y.
ChadBillinsMIce Hockey28MarysvilleMich.
RyanDonatoMIce Hockey21ScituateMass.
NoahWelchMIce Hockey35BrightonMass.
RyanZapolskiMIce Hockey31EriePa.
JimSlaterMIce Hockey35LapeerMich.
BrandonMaxwellMIce Hockey26Winter ParkFla.
WillBorgenMIce Hockey21MoorheadMinn.
GarrettRoeMIce Hockey29ViennaVa.
BobbySanguinettiMIce Hockey29WilmingtonN.C.
JonathanBlumMIce Hockey29Ladera RanchCalif.
TroyTerryMIce Hockey20Highlands RanchColo.
ChadKolarikMIce Hockey32AbingtonPa.
RyanStoaMIce Hockey30BloomingtonMinn.
BobbyButlerMIce Hockey30MarlboroughMass.
RyanGundersonMIce Hockey32BensalemPa.
MarkArcobelloMIce Hockey29MilfordConn.
BrocLittleMIce Hockey29RindgeN.H.
BrianO'NeillMIce Hockey29YardleyPa.
SummerBritcherFLuge23Glen RockPa.
ChrisMazdzerMLuge29Saranac LakeN.Y.
TaylorMorrisMLuge26Salt Lake City Utah
MattMortensenMLuge32Huntington StationN.Y.
AndrewSherkMLuge25Fort WashingtonPa.
BenBerendMNordic Combined22Steamboat SpringsColo.
TaylorFletcherMNordic Combined27Steamboat SpringsColo.
BryanFletcherMNordic Combined31Steamboat SpringsColo.
JasperGoodMNordic Combined21Steamboat SpringsColo.
BenLoomisMNordic Combined19Eau ClaireWis.
MattAntoineMSkeleton32Prairie du ChienWis.
NitaEnglundFSki Jumping25FlorenceWis.
SarahHendricksonFSki Jumping23Park CityUtah
AbbyRingquistFSki Jumping28Park CityUtah
KevinBicknerMSki Jumping21WaucondaIll.
MichaelGlasderMSki Jumping28CaryIll.
CaseyLarsonMSki Jumping19BarringtonIll.
WillRhoadsMSki Jumping22Park CityUtah
JamieAndersonFSnowboarding27South Lake TahoeCalif.
KellyClarkFSnowboarding34Mammoth LakesCalif.
ArielleGoldFSnowboarding21Steamboat SpringsColo.
FayeGuliniFSnowboarding25Salt Lake CityUtah
HaileyLanglandFSnowboarding17San ClementeCalif.
NickBaumgartnerMSnowboarding36Iron RiverMich.
MickDierdorffMSnowboarding26Steamboat SpringsColo.
KyleMackMSnowboarding20West BloomfieldMich.
MikeTrappMSnowboarding29Marstons MillsMass.
HeatherBergsmaFLong Track Speedskating28High PointN.C.
BrittanyBoweFLong Track Speedskating29OcalaFla.
ErinJacksonFLong Track Speedskating25OcalaFla.
MiaManganelloFLong Track Speedskating28CrestviewFla.
CarlijnSchoutensFLong Track Speedskating23West JordanUtah
JericaTandimanFLong Track Speedskating23KearnsUtah
ShaniDavisMLong Track Speedskating35ChicagoIll.
JonathanGarciaMLong Track Speedskating31HoustonTexas
KimaniGriffinMLong Track Speedskating27Winston SalemN.C.
BrianHansenMLong Track Speedskating27GlenviewIll.
EmeryLehmanMLong Track Speedskating21Oak ParkIll.
JoeyMantiaMLong Track Speedskating32OcalaFla.
MitchWhitmoreMLong Track Speedskating28WaukeshaWis.
MaameBineyFShort Track Speedskating18RestonVa.
LanaGehringFShort Track Speedskating27GlenviewIll.
JessicaKooremanFShort Track Speedskating34MelvindaleMich.
J.R.CelskiMShort Track Speedskating27Federal WayWash.
ThomasHongMShort Track Speedskating20LaurelMd.
John-HenryKruegerMShort Track Speedskating22PittsburghPa.
RyanPivirottoMShort Track Speedskating22Ann ArborMich.
AaronTranMShort Track Speedskating21Federal WayWash.
Posted in Excel, Statistics | Leave a comment

Time for a Job Change


Quote of the Day

Be kind whenever possible. It is always possible.

— Dalai Lama

Figure 1: I have decided that it is time for a new job. (Source)

Figure 1: I have decided that it is
time for a new job.

My company is changing its approach to hardware development, and after much soul-searching, I have decided to volunteer for layoff. I do not have any immediate plans – it is just time for a change. I will continue to write on technical topics because math, electronics, and software are in my blood.

I fell in love with electronics when I was five-years-old after my neighbor showed me a schematic. I thought it was some weird language that I needed to figure out. My first projects involved building kits from Radio Shack, Heathkit, and Lafayette Radio that I paid for using my income as a paperboy. I also started doing circuit-based science fair projects. It all culminated with me studying electrical engineering and working in this field for my entire career. Even after these many years, my passion for technology of all sorts continues unabated.

If you know of any jobs that would be appropriate for someone like me, please leave me a note here or on my linkedin page. My wife's job is covering my benefits, so either a contract or employee position would work.

Figure 2: Interociter schematic from the movie This Island Earth. This schematic also interested me as aboy. I loved that movie. (Source)

Figure 2: Interociter schematic from the movie This
Island Earth
. This schematic also interested me as a
boy. I loved that movie. (Source)

Posted in Personal | 6 Comments

Smallest Rocket to Put Payload Into Earth Orbit


Quote of the Day

Our educational system is like an automobile which has strong rear lights, brightly illuminating the past. But looking forward, things are barely discernible.

Hermann Oberth, German rocket theoretician, describing the German education system in the 1920s. He was bitter because his doctoral thesis on rocket propulsion was deemed utopian. His work became the basis of all spaceflight today. In my opinion, his criticism of the German educational system could be applied to the US education system today.

Figure 1: Japan's SS-520 rocket. It is reported to be the smallest rocket capable of putting a payload into orbit. (Source)

Figure 1: Japan's SS-520 rocket. It is reported to
be the smallest rocket capable of putting a
payload into orbit. (Source)

I just read a news article about Japan launching a 3 kg satellite into orbit using a 9.7-meter-long, two-stage rocket called the SS-520 (Figure 1). The 9.7 meter length was interesting to me because I recalled an Air & Space magazine article from 1999 that stated that the smallest rocket capable of achieving Earth orbit would be "about 30 feet long." Since 9.7 meters is 31.8 feet long, it appears that Japan's SS-520 is very near the lower size limit for rocket that can put an object into Earth orbit.

The size limit for an orbital rocket is driven by the amount of momentum lost because of atmospheric drag. As with artillery projectiles, larger rockets are more efficient in retaining momentum against drag. For a given shape, larger rockets are more aerodynamically efficient because frontal area increases by the square of the linear dimensions and volume (and mass) scales by the cube of the linear dimensions (see this detailed discussion). Drag is a function of the frontal area of the rocket, thus larger rockets have more mass (and momentum) relative to their drag. Another challenge with implementing a small launch vehicle is the difficulty of efficiently implementing a high specific impulse, liquid-fuel system because of the overhead of all the pumps, plumbing, and cooling.

Because I am still tied up with my cabin project, I have not gone through the minimum-sized orbital rocket calculations myself. Air & Space magazine states that:

A terrestrial rocket has to push through a plug of air equivalent to a 30-foot column of water, and physics dictates that the smallest vehicle capable of moving all that atmospheric mass without paying a penalty in momentum is about 30 feet long.

Historically, the orbital launch market has been dominate by customers who want to put large payloads into space. The advent of CubeSats has created a market for these small rockets. For example, a company called  Rocket Lab uses their Electron rocket to launch small groups of CubeSats.

NASA has been researching the smallest rocket that can return a sample from Mars to Earth. According the Air & Space magazine article, the smallest orbital rocket is "about the size of a pencil" for essentially zero payload. NASA's Mars return mission is targeting a 1 pound payload and the mass is about 170 kg. Having lower gravity and a much thinner atmosphere make the job of getting into Mars orbit much easier than getting into Earth orbit.

People have been discussing these small rockets for many years. In fact, people have tried to motivate innovation in this area with the N-Prize, which is focused on putting a small payload (10 - 20 grams) into Earth orbit for less than 1000 £ . For an excellent discussion on micro-rocketry, see this forum thread. The following Google talk on microlaunchers is also useful.

Figure 2: Microlaunchers – The Case for a New Generation of Very Small Spacecraft.
Posted in Astronomy, Space | 5 Comments