11
$\begingroup$

Wikipedia has an article on atmospheric tides but it is mostly earth based considerations. I was wondering if they have any impact on satellites or rocket launches? We know that satellites in Low Earth Orbit are subject to drag from the atmosphere.

Do atmospheric tides impact that drag?

Do any considerations for atmospheric tides need to be made during a rocket launch?

$\endgroup$
  • 2
    $\begingroup$ Yes, they do (I don't have enough knowledge for a full answer, therefore I post it as a comment). $\endgroup$ – gerrit Nov 25 '14 at 16:11
10
$\begingroup$

The diurnal bulge in the atmosphere plays a rather minor role during launch. Launch is short in duration and involves an aerodynamically shaped vehicle that punches through the thickest part of the atmosphere. Whether its locally 2 PM (bulge is thickest) or 4 AM (bulge is thinnest), the density at orbit insertion altitude is tiny compared to that of the troposphere, stratosphere, and mesosphere through which the vehicle has plowed before getting to that orbit insertion altitude.

The diurnal bulge plays a significant role on a satellite in low Earth orbit. The very short duration launch interval (ten minute or less) becomes years of operations for a satellite in low Earth orbit. The effects of drag pile up over the years. On top of that, most satellites have anything but a nice aerodynamic shape. One of the first things a satellite does after separating from the launch vehicle is to deploy its solar arrays.

Another big factor is the Sun. One solar flare, and poof! the upper atmosphere swells. Drag on a satellite can easily more than double between solar minimum and solar maximum.

$\endgroup$
  • $\begingroup$ Do you know if a solar flare expands the atmosphere globally, or just increases the daylight bulge? IRIS has a sun-synchronous Earth orbit from where it can always observe the Sun. So that kind of orbit should not have any problem with atmospheric tides? $\endgroup$ – LocalFluff Nov 26 '14 at 12:52
  • 2
    $\begingroup$ @LocalFluff - Solar activity puffs up the atmosphere as a whole. With regard to a vehicle in a sun synchronous orbit that more or less stays on the terminator, that vehicle will pass into and out of parts of the diurnal bulge. Density in the upper atmosphere reaches minimum and maximum at about 4 AM and 2 PM local solar time, respectively. It's not quite symmetric, and it's not local midnight / local noon. $\endgroup$ – David Hammen Nov 26 '14 at 15:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.