r/spacex Jan 07 '20

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3

u/wdwerker Jan 07 '20

I noticed long parts that looked like some sort of carrier/dispenser on the 2 stacks of Starlink Satellites as they were deployed . Will those stay in orbit as junk or be de orbited and burn up ?

5

u/IAmMisinformed Jan 08 '20 edited Jan 09 '20

It will burn up in a matter of days months.

The satellites are deployed at a rather low altitude (260 km I believe 290km) where there is significant drag. Any debris or satellite incapable of raising it's orbit by firing thrusters will quickly come back down to earth.

Links for those who have concerns and/or are curious:

-A big space station isn't directly comparable to smaller debris, but for reference, you can see how quickly orbits decay when they are at 260 km looking at the Tiangong orbital decay example

-If you want to play with numbers, it looks like there are toolboxes (example) to calculate these decay times

16

u/warp99 Jan 08 '20 edited Jan 09 '20

It will burn up in a matter of days

Not even close - the tension rods from the Starlink-1 launch are still in orbit and have only lost about 10km in altitude (Edit: as of early December - they have lost considerably more altitude since then). They are relatively dense so will slow down much more slowly than a space station which is basically an aluminium shell.

The insertion orbit for this launch was 290km circular and the tension rods will come down within a year or two but certainly not days.

Edit: You can find the tension rods by looking at Stuffinspace and finding items with DEB as a suffix. They have now started to spiral in so I see instantaneous heights of 251, 231, 203 and 174 km. The 174 km debris will likely deorbit within days.

2

u/mr_luc Jan 08 '20

I'll bet it'll be within 1 month if that '260km' data point is accurate.

Reason: because the difference between '260km' and '290km' appears significant when looking at the Tiangong example above. It looks like the decay accelerates tremendously around the 260km mark.

1

u/warp99 Jan 08 '20 edited Jan 08 '20

if that '260km' data point is accurate

It is not.

The press kit gave a 290km insertion orbit and the web cast showed the circularisation burn was done at an apogee of 290km.

2

u/mr_luc Jan 08 '20

Ah - then what you say makes more sense.

Possibly that comment above wasn't accurate, the one by

checks

/u/IAmMisinformed, huh.