# Monthly Archives: July 2017

## 100 Mile Square Solar Array Could Power US

lon Musk gave a talk at the National Governors Association where he stated that a 100 mile square solar array built in place like Nevada could generate an amount of electrical power equal to that of the present electrical grid. This seems like an easy calculation to verify and I thought I do that analysis here. Continue reading

Posted in News Fact Checking | 1 Comment

## US WW2 Submarine Tonnage Sunk Database

While answering a recent question about the tonnage sank by the top US submarine skippers during WW2, I realized that I had not made available my conversion of the JANAC data for vessels sunk by US submarines. The JANAC records are considered the official records because they were cross-checked with information from Japanese records. Continue reading

## Security Risks with Medical Radiation Sources

Posted in News Fact Checking | 5 Comments

## Insulation Opportunity Costs

I have had a number of discussions with coworkers about the different types of wall insulation – some of these discussions have been documented in previous blog posts (e.g. here , here, here). There exists wide cost and performance disparities between the different wall insulation technologies. With respect to cost, I view fiberglass batts as a low-cost insulation option and the spray foams (open and closed cell) as high-cost options. All the options have their advantages and disadvantages. Fine Homebuilding Magazine (August/September 2017) has an excellent article by Martin Holladay provides an excellent spreadsheet-like analysis that illustrates the trade-offs between open and closed-cell foam nicely. My goal in this post is to go through the computational details of his analysis and to discuss his approach to choosing the best insulation for your application. Continue reading

Posted in Construction | Comments Off on Insulation Opportunity Costs

Putting a satellite into orbit requires that you impart a velocity of ~17,000 mph to the satellite. Because the Earth is rotating, its surface velocity gives you a head start on achieving orbital velocity when you launch toward the east – the direction of the Earth's rotation. The closer you move your launch site to the equator, the more velocity you get from the Earth's rotation. Continue reading

Posted in Space | 2 Comments

## Iceberg Size Analogies

e nightly news reports have been filled with stories about the large iceberg that recently calved off of the Larsen C ice shelf. Reports of natural events always struggle with trying to convey the scale of events to the general public. In this case, the media has been reporting that the iceberg is (1) approximately the same area as the state of Delaware, (2) it contains a volume of water that is double that of Lake Erie, and (3) the mass of water it contains is about 1 trillion metric tons. Figure 1 shows a good graphic for area comparisons. Continue reading

Posted in General Science, News Fact Checking | Comments Off on Iceberg Size Analogies

## CO2 Generation By Fuel Per Million BTUs of Heat

My year-round cabin in northern Minnesota needs a furnace, and a furnace needs fuel. My fuel options are fairly limited – fuel oil, liquid natural gas, or propane. I ended up choosing propane because the local propane gas supplier has a reputation for being reliable. While researching the fuels, I became curious about the amount of CO2 released into the atmosphere by the different fuel options for given amount of heat. Continue reading

Posted in Construction, General Science | 1 Comment

## Personnel Count of US Special Operations Forces

I have a son who lives in Butte, Montana – the home town of Robert O'Neill, a famous US Navy SEAL. We were discussing Mr. O'Neill's exploits one night and started to wonder about the size of the different US special operations forces. I quickly looked up some 2014 data from the Government Accountability Office (GAO) and put the data into a pivot table (Figure 1). I was a bit surprised at the numbers involved – it does not surprise me that the Army has the largest contingent, but the size of the Air Force's contingent was a surprise. Continue reading

Posted in Military History | 2 Comments