23 Jul 2019
Over the coming months, years, decades, no one really knows, I will be working
through the exercises from “Fundamentals of Astrodynamics” by Bate, Mueller, and
White. The intent is to not only provide myself with a refresher, but to
provide a resource for enterprising students.
Exercise 1.1 The position, , and velocity, , of a
satellite at a given instant in canonical units: Distance Units (DU) and
Distance Units per Time Unit (TU), respectively, are described by
Find the specific angular momentum, , and specific mechanical
energy, , of the system.
Solution:
Equation for specific angular momentum:
An easy way to set up the crossproduct is using Sarrus’ scheme:
This yields:
Equation for specific mechanical energy:
Since we’re using canonical units, let :
05 Mar 2019
Weight and power if you’ve never heard of it, or in other parlance, weight and
balance is a crucial set of calculations for safety of flight. Having the
numbers wrong could be the difference between life or death. Where I work, it
involves interpreting various charts and tables and hand jamming numbers into a
calculator and penciling in over fifty blanks on a paper form. It takes anywhere
from 10 to 15 mins on average to do depending on experience. Time that can be
better spent with other aspects of flight planning. So why do we have humans do
the calculations when a computer can do it faster and more accurately?
The explanation you’re likely to hear is that it’s because “we’ve always done it
that way” or “it’s important to know how to do the calculations.” I’d only
begin to accept the later, but it’s still a bad explanation. Sure there’s some
merit to knowing how to do it by hand. After all, you may have to do it on the
fly or somewhere you don’t have a computer. But the reality is, these situations
are far from the norm.
A good solution would be to have one day out of the week for pilots to do it by
hand and the rest of the week the computer does it. Sure the software would
have to be written, but it’d be close to trivial. Let’s do the math. On
average, we schedule 4 flights a day. Let’s go with the low end of 10 minutes
to hand jam the numbers. Spread that over 5 days a week and 50 fly weeks a
year, that’s 167 hrs. If you go with the high end of 15 min, that’s 250 hrs.
Pilots get paid on average $60/hr. That comes out to $10,000 to $15,000/yr of
human capital wasted on an easily automated task. I’d write the software myself
for far less. It’s 2019, let’s start acting like it.
02 Mar 2019
Many of my days at work start with checking out a helmet from a small office for
FOD (foreign object debris) walk-down. Just imagine making a line and walking
an area to pick up “trash” like the Boy Scouts do to a campsite. But while that
may sound frustrating to do day in and day out, it’s not the frustrating part.
The frustrating part is the checkout. There is a form that you must fill out
with the checkout date and time, your name, your signature, and the helmet
(actually “your helmet” because everyone has their own). Then of course, you
also have to sign back in with the time and date, your name, and your signature.
What’s more? The same people do this everyday at the same time. It’s not like
you don’t know the majority of who’s going to show up. Now imagine around 20+
people all trying to checkout their helmets at the same time in this small
office. You can barely get in or out of the door. It’s a classic process
bottleneck. One day I walked in and there was a refreshing sign of improvement.
The lady working in the office, who’s almost never busy at this time, had
pre-filled out the date and time since it’s more or less the same for everyone.
Checkout speed doubled. But how long did this last? Less than a week. There’s
got to be a better way. Of course, technology offers many attractive solutions.
My favorite is RFID. The helmets would have a small RFID antenna and when they
pass through the door, they get scanned. Simple. Elegant. No one would have to
fill out anything. But alas, that would take an act of congress. But what
could be done, and what I’m proposing next week is that we make a new form
because we can’t not have a form. But this form will be different. It will
just require two signatures. One when you check out and one when you check in.
All the rest of the information will be pre-printed on the form because it isn’t
variable enough to not be. If it flies, it’s a stupid simple improvement. But
then again, those types of improvements tend to be the best. Keep it simple
stupid.
27 Feb 2019
…works until what comes out of the machine is on the verge of unreadable. So take the time to make a copy of the original if the original still exists. Better yet, make a new original and ask how it can be done better this time around.
26 Feb 2019
In true nerd fashion, here’s my hello world post. It’s been my goal for a long
time to start a blog. So here it is. Welcome to my world.
I hope it moves you.