Sunday, February 10, 2013

Lift, Weather, Dew Point, and Math!

My father, who is one of the most intellectual and knowledgeable people I know, has been my technical adviser for this whole "make steampunk as scientifically accurate as I can" endeavor and today's topic of conversation focused on psychrometrics: Wikipedia has this helpful definition:

Psychrometrics or psychrometry or Hygrometry are terms used to describe the field of engineering concerned with the determination of physical and thermodynamic properties of gas-vapor mixtures. The term derives from the Greek psuchron (ψυχρόν) meaning "cold"[1] and metron (μέτρον) meaning "means of measurement".

The main connection with steampunk is the operation of an airship: a steam or gas-powered airship deals directly with psychrometry because of what lifts it off the ground. Dad explained that a hot air balloon flies much better in cold air because it has much more lift capability and if it is a very hot day, the balloon may not even get off the ground. Yesterday I was writing this into Chapter Seven of Steam on the Horizon:

          "Halloway, Jenkins,” Roberts commanded. “We're running low on time. Increase her to thirty knots.” He didn't want to run her at maximum speed less he burn out her engines on her first official run, but it was difficult to tell just how hard and fast he could push her considering the load she was carrying. Calculating how much cargo an airship could carry and what speeds she could fly was part math, part guesswork, and Roberts knew that it would take several full runs before he had a fairly precise understanding of just how much weight the Horizon could carry at what speed without incurring undue stress. 

Dad pointed out that Roberts would be doing a lot of temperature measurements of the inside of the envelope and the air temperature in order to calculate how much deadweight tonnage the Horizon could lift at one go. During the first year Roberts has the Horizon, he and the crew rebuild her during an unseasonably hot summer, and according to psychrometrics, airships might not even be able to fly in those conditions because they couldn't get enough lift.

The Horizon spends much of the second part of the book freezing her cogs off in the Crimea, so I think I am going to work in that she can lift more and fly a little faster in these colder temperatures. Dad said that very cold is the best temperature for a plane to fly in because the molecules slow down and the air is denser so it holds the plane up better, somewhat like how it is almost impossible to sink on the Red Sea because its high saline content (33.7% salt) gives a human body incredible buoyancy.

Between my dad and my new work as a medical helicopter dispatcher, I am learning an incredible amount of steampunk-related information that, if all incorporated into the book, would make it 1,431 pages long. At work, I am constantly scribbling down ideas for later revision. One revelation was that, in the absence of steampunk NVG (night vision goggles) for her crew, the Horizon needs excellent lights on board for nighttime flying. The general rule of thumb for a helicopter pilot is that if he does not have NVG and is flying via VFR (visual flight rules), he should be able to see three miles during the day and a mile during the night, otherwise, he needs to plant his bird on a helipad until flying conditions improve.

The Horizon, however, cannot simply land wherever she chooses: without skids or other landing apparatus, she has to stay in the air until she can find a berth. Or......I could always make it so that she could indeed land on a level patch of ground if needed. That, however, would require rewriting large sections of the book, so I think I will keep it as is.

Excellent news! InConJunction XXXIII will be hosting Cheri Priest for this year's con! (happy dance!). A friend of mine told me about this con, and I do believe I will need to haul my steampunk-costumed self out to Indianapolis for this particular shindig, particularly since there appears to be a movie version of Boneshaker in development, according to Miss Priest herself.

Did I mention that yesterday, I imbibed 16 ounces of straight espresso in one sitting? I don't recommended it: I reeked physically from all the sweet, I was giggling as if tipsy, and I was smelling colors at one point. But still:

1 comment:

  1. I have to say, I'm incredibly impressed at the research and accuracy you are pouring into your story. It's very interesting. I didn't know that about cold air though it makes sense in hindsight. I guess that's why ballooning is so popular around here - we've got such cold air all of the time. :)