Checking the onboard video of PSLV C43 gives a feel like the CubeSats are released in very proximity.
Does this mean that these CubeSats will be orbiting in such very close proximity through out their life?
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asked Nov 30, 2018 at 18:03
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1$\begingroup$ Go into KSP and put a 6 stage rocket into orbit using cheats. Decouple each stage at about the same rate as shown in the video, fast forward time for a few days and see if they're anywhere near each other ;). The only issue for collision is if they launch the cubesats directly perpendicular to the velocity vector. If only the inclination of the cubesat orbit is changed, there is a chance they'll intercept the space station again. However, when you're travelling at 9.4km/s, those cube sats will have significant differences in position and velocity vectors, even with a short launch intervals. $\endgroup$– Magic Octopus UrnCommented Nov 30, 2018 at 18:13
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2 Answers
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At the moment of release from the dispenser on the launch vehicle or other carrier spacecraft the CubeSats will be very close.
After that they will start to naturally separate due to a variety of reasons:
- CubeSats, per the CalPoly standard, are supposed to have small springs that push them apart from other CubeSats in the same dispenser tube
- The launch vehicle will stagger deployment of CubeSats from different dispensers. It can also conduct both attitude and propulsive maneuvers to generate different ejection velocity vectors for each deployer
- Each CubeSat will have slightly different reaction to atmospheric drag and solar pressure effects. This will make their orbits change in different ways.
After a while, the CubeSats will begin to disperse into different orbits. There is a chance of future recontact/collision, and the launch provider is supposed to run analysis to ensure that this chance is minimized.
This is not unsimilar to what happens when two space objects collide. Here instead of "deployments" you have debris being scattered by the collision. Check out this video that shows how the cloud of debris is first clumped together but then starts spreading out.
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This excellent answer lists a number of different cubesat deploy mechanisms used on PSLV-C43. One could try to check each of their deploy velocities, my guess is that they will be in the ballpark of 0.5 or 1.0 meter/sec. Guessing 1 cubesat every minute,that's 30 to 60 meters from one to the next.
Watching the video PSLV-C43 / HysIS Onboard Camera View cued at 01:12 you can see that some cubesats are deployed prograde and the others retrograde. Looking at the image below one can see that there is a bimodal distribution of orientations (left and right, not radial). The spacecraft's axis was first oriented towards the nadir.
After several deployments the spacecraft pitched so that the deploy direction was towards the nadir instead of retrograde + prograde.
While 1 m/s might sound slow compared to 7700 m/s its plenty to space the satellites out. Since Earth's gravity field has both a ~part per thousand oblateness and other lumps, these orbits will tend to "scramble" (excuse the fancy science word) over time.
cued at 01:12:
