Parts one and two of modeling the atmosphere derived a way to describe atmospheric pressure as a function of altitude, assuming a constant temperature and acceleration due to gravity throughout the ideal gas. In this installment of Modeling the Atmosphere, the same function will be derived, this time using the Boltzmann distribution.
The previous Modeling the Atmosphere post derived an expression for describing the change in pressure with respect to change in altitude in terms of density and acceleration due to gravity :
This equation is short to write, but it is not particularly useful. Before applying it to real-life situations, it must be transformed into the barometric equation.
There’s a physics joke where a dairy farmer calls up the local university asking for some help improving his cow business. He ends up on the phone with a physicist, who assures the man that a solution can be found. Months later the farmer gets a call back. It’s the physicist, who says excitedly, “I can can help you, but my model only works for the case of spherical cows in a vacuum.”
Sprites are tiny; there’s a reason they are called chip satellites. They are powered by a pair of TASC (triangular advanced solar cells) that are less than 5 centimeters square in surface area, and their antennas are even smaller. Is it even possible for one of these devices to send a signal 500 km back to Earth?
After a lengthy process of gathering most of the materials and MacGyvering the rest, I’ve put together a proof-of-concept version of the magnetometer.
The materials used in this build are as follows:
- One (1) 1.905 cm diameter, 0.1588 cm thick neodymium grade N48 axially magnetized magnet
- One (1) 1.905 cm diameter glass mirror (craft supply)
- A Helium-Neon (HeNe) laser (but any laser pointer would work for this alpha build)
- A length of string
- A plastic toothpick
- Some office tape
- A bit of silly putty I found
- Some water
First, the magnet with the mirror, toothpick, and string taped on:
As explained in the first webinar video, one of the long-term goals of the Sprite project is to be able to deploy fleets of them throughout various parts of the solar system. These Sprites would sport a mix of sensors; a portion of them might analyze spectral data while others might have plates for capturing space dust. There’s a long way to go before Sprite fleets are traveling and collecting data outside of low Earth orbit, but Sprites with sensors other than the default temperature sensor could happen much sooner. The design team is considering incorporating a magnetometer, an accelerometer, or a gyroscope into some or all of the KickSat Sprites. While I wait to see whether any of these sensors make their way into my Sprite, I’ve decided to build a magnetometer of my own.