Hi,
The analysis is idealized (assume that the cow is a sphere) and assumes zero attraction between the ISS and the Cubesats. It also neglects drag forces and possible effects of the Moon, Sun, and other planets.
The basic idea is that one can think of an elliptical orbit as being a radial oscillation about a nominal circular orbit. It can be shown* that the period of the radial oscillation is equal to the orbital period (if that weren’t the case, elliptical orbits would not be “closed.”). From the point of view of an observer on a platform that is undergoing the circular orbit (we will assume this for the ISS), the Cubesat appears to move back and forth between a slightly lower and slightly higher orbit. It moves a bit faster when it is at its lowest point, and thus gets ahead of the ISS. When it is at its highest point, it moves slower and falls backward. The net effect is the aforementioned elliptical orbit.
73,
Dan K2QM
* If there is interest, I can probably dig up my old notes on this problem.
From: Burns Fisher <[email protected]>
Sent: Friday, July 22, 2022 3:56 PM
To: Daniel R. Marlow <[email protected]>
Cc: Ashhar Farhan <[email protected]>; [email protected]; Joseph B. Fitzgerald <[email protected]>; AMSAT BB <[email protected]>
Subject: Re: [AMSAT-BB] Re: Ten Russian cubesats to be deployed from the ISS
This is awfully interesting! Does the analysis assume a tiny amount of gravitational attraction between the ISS and the cubesat?
I think we are pretty sure that when multiple cubesats are released from a single P-POD one a ride-share rocket they have slightly different velocities and even if they stay in ~the same plane and altitude, they do separate in time. Just wondering how that all fits. (I suppose one difference is that the P-POD carrying stage will like change its orbit after the release).
Thanks!
On Fri, Jul 22, 2022 at 1:08 PM Daniel R. Marlow <[email protected]> wrote:
Hello,
A standard exercise in classical mechanics is to show that when an object is released in the right way from a satellite that is in a circular orbit, that object can end up appearing to orbit the main satellite. The shape of the orbit as seen in the reference frame of the main satellite is an ellipse. Unlike normal Keplerian orbits, where the attracting mass is at one focus of the ellipse, the main satellite is at the geometric center of the elliptical orbit.
73,
Dan K2QM
P.S. Normally the sub satellites are taken to be beer cans, but this analysis should also work for Cubesats.
From: Ashhar Farhan <[email protected]>
Sent: Friday, July 22, 2022 11:57 AM
To: [email protected]
Cc: Joseph B. Fitzgerald <[email protected]>; AMSAT BB <[email protected]>
Subject: [AMSAT-BB] Re: Ten Russian cubesats to be deployed from the ISS
When a satellite is dispensed from a mothership like the ISS, the orbit cant really go too far away due to the nature of orbital mechanics. The iss and the cubesat orbits will have to intersect at least twice. Is there a more precise modeling of this?
On Fri, Jul 22, 2022, 9:19 PM Wayne Greene <[email protected]> wrote:
ok. I'll try the ISS predictions, then. I wasn't able to find anything in space track. Of course, I might have been doing something wrong with my searches.
On Fri, Jul 22, 2022 at 11:32 AM Joseph B. Fitzgerald <[email protected]> wrote:
Regular ISS predictions will be pretty accurate for several days. They were released by hand so the delta-V imparted will be pretty low.
de KM1P Joe
--Wayne Greene
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