March 2016

This month we will discuss the movie, The Martian, from an engineering point of view, then talk of something way more important. And, oops, I have to throw in two music videos, just because I can.  Let's start with Mumbles.... 


Clark Terry died in February 2015, at 94 years old.  He was the first African American to appear in a band on a regular television show, in Johnny Carson's Tonight Show on NBC, starting in 1960 and ending in 1972.  He had played in both Count Basie and Duke Ellington's orchestras, and was a WWII vet. Read his obit here. In case you don't understand scat, let me spell out the actual title of this song: Angyumaluma Bongliddleany Nannyany Awhan Yi!

Mumbles by Clark Terry

 The Martian

There is lots of chatter on the web about whether the movie (or for people who can read, the book) was an accurate depiction of what it would be like on Mars.  The windstorm scene is the biggest fabrication, the atmosphere on Mars is 1% of earth's, so there is no way it is going to knock stuff around.

What about the scene where they slow the Hermes, by expelling air? Hopefully the link below lasts a while before it gets yanked. Brace for deceleration...

Brace for deceleration

In the book, it is claimed that this adventure would change the velocity of the Hermes by 29 meters per second.  There are no data available on the mass/volume of the Hermes (which doesn't exist), so let's make a calculation on how much the International Space station would slow if you let the air out of the front end. The table below was done in a spreadsheet and copied onto this page, any mistakes are mine.  Bracing for deceleration was not really necessary, as each astronaut was only exposed to a gentle 1 lb. of force. The change in velocity is extremely small.  This waste of air changed the velocity by less than just 0.3 m/s, which is not going to change the outcome of the event.  The book says the deceleration will be "a little less than one G" (the movie seems to have amped that up). 0.06 G is what I calculated. 


  Units Parameter Source
1.225 kg/m^3 Density of air Wikipedia
916 m^3 Volume of ISS Wikipedia - ISS
1122.1 kg Mass of air expelled Wikipedia - ISS
100 m/s Velocity of air Pidooma
112210 kg-m/s Momentum of air expelled Mass times velocity
4 sec Time air took to expell The Martian (book)
28052.5 Newtons Force incurred by expelling air Momentum divided by time
    Before air is expelled  
420000 kg Mass of ISS Wikipedia
27600 km/h Velocity of ISS Wikipedia
7666.666667 m/s Velocity of ISS  
211600000 kg-m/s Momentum of ISS Mass times velocity
    After air is expelled  
418877.9 kg Mass of ISS Subtract the air
0.267882359 m/s Change in velocity Conservation of momentum
0.066791667 Newtons Acceleration Force/mass
0.006815476 G Acceleration in Gs divide by 9.8
1.363095238 lbs Force relative to 200 lb astronaut  
99.9965% % Relative velocity after/before  

In order for the book to be correct, two orders of magnitude have to be added to the calculation.  Perhaps the air escaped at 10,000 meters per second, 5X faster than the velocity of a rail-gun? No way, Jose, 100 m/s that I used was overly generous.  Perhaps they had 100X more air to get rid of? Maybe the Hermes has 1/100 the mass of the ISS. Maybe a combination of the three gets you 29 m/s.  But you certainly don't have to "brace for deceleration" to change 29 m/s in 4 seconds (which is 0.75G).

Next, let's talk about covering the missing airlock with a sheet of poly-ethelene and some duct tape.  With atmospheric pressure at 16 psi, that tarp would have 10s of thousands of pounds of pressure on it and would not hold.  Sorry I didn't use the metric system, I am a product of the New Jersey educational system, graduating from the unaccredited Montville Township High School not far from where the Real Housewife who served a year in jail used to live. Sorry about all those broken beer bottles on the property, we had to clean out the truck every day on the way home from work...

One more thing about the most popular quote in the movie... which is offensive to me.

Mark Watney:  "In the face of overwhelming odds, I'm left with only one option, I'm gonna have to science the shit out of this."

Scientists ponder what is possible, engineers make it happen by solving problems one by one.  That quote should be "engineer the excrement out of it".

 Of course, we have come a long way in space movies since 1968's Planet of Prehistoric Women... but I would pay some serious cash to own that space car those lucky astronauts got to ride around in, on Venus.

Planet of Prehistoric Women


*What goes up and doesn't come down?

The answer is helium.  Helium is the only substance on Earth that, once you release it, rises through the atmosphere and is swept into space.

Boogie Oogie Oogie

But wait, I promised a second music video,.  Let's go back to 1978, toward the end of the disco era.  Here's a song that that arguably kept Disco alive for many years. The group was "Taste of Honey", the song was Boogie Oogie Oogie, and the bass player and lead singer is Janice–Marie Johnson.  See if you can think of a more talented musician/songwriter/singer today.  Nothing comes to mind.

Janice–Marie Johnson is of Native American heritage and was inducted into the Native American Music Hall of Fame in 2008, and is still going strong, playing this song at the ceremony. There are currently over 5 million Native Americans living in the United States, you would be surprised to know some of people who are part of this family tree.

Get down, boogie till you just can't boogie no more....

Back to the subject at hand: helium.  Helium has many industrial purposes that would be hard to live without, including welding and cryogenics.  It is the only element that literally blows off of the Earth over time, once you release that party balloon, you've frittered some of it away.  Where does it come from? It is found underground, in just a few place on earth, it is a byproduct of uranium that is decaying deep underground.    It is extracted from natural gas. Depending on your information source (I'll let you google that), the world could be running out of helium in 10 or 20 years.  It is worth pointing out that in a post-carbon-fueled society (needed to put the brakes on global warming) there will be less natural gas extracted and less helium available.

Why am I ranting about this all of a sudden?  Here in Tucson, some entrepreneurs have come up with a scheme for a "space port" south of the airport that will supposedly bring money and jobs to our impoverished city and environs. The local Pima County Board of Supervisors bought this bill of goods from World View Enterprises (nice website, they must really know a lot about space business!) and ponied up a loan of $15M of taxpayer money to subsidize it. We will soon build a 120,000 square foot facility for this.

So, will we become the next Cape Canaveral and launch mission to Mars?  Nope.  The idea is that our "spaceport" will provide near-space experience by lifting capsules using giant bags of helium.  Rich people will pay $75,000 for this short ride to 19 miles altitude in the lap of luxury, so they can see for themselves that the Earth is round.  No word on whether there will be a crapper in the capsule, but if there is, it likely won't be vented well to the outside... The projected economics of the venture suggest that the city might get its money back after 20 years. There are many things wrong with this picture.

  1. Do we need another reminder that rich people will enjoy incredible luxury and privileges while the spaceport facility employs our citizens at less than $10 per hour to build and maintain this joy ride?
  2. How does a city that is so broke it can't pay teachers a living wage get in the business of subsidizing someone's money-making fantasy?
  3. Why don't we all work to conserve natural resources (such as helium) rather than waste them?
  4. When the "Voyager" carny ride inevitably kills a bunch of rich people, are they going to sue the city for subsidizing it?

If I were a county supervisor, I'd much rather spend 15 million on things like paying our teachers more so our kids will be able to compete in a global economy and not be part of the vast army of minimum wage earners that sustain big businesses.  

On the topic of education, read two new proposed changes afoot in United States education system:

Cursive handwriting needs to be taught in Arizona (some of the arguments are hilarious)

Algebra should not be a requirement for graduation

You just can't make this stuff up.


Check out the Unknown Editor's amazing archives when you are looking for a way to screw off for a couple of hours or more!

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