JF Mezei wrote on Sat, 8 Jun 2019
20:08:27 -0400:

On 2019-06-08 16:18, Fred J. McCall wrote:

Most capsules aren't pure ballistic objects. They can generate lift.

At 340km altitude, do they generate any lift? Aren't they pure ballistoc
at that point?


As usual you totally miss the point. Let me try and explain it to you
in detail even you will grasp. First, remember that any given bit of
space I need to fly through is empty 99.6%. For the other 0.4% of the
time I might have to do a reentry burn that is slightly suboptimal. If
I'm really stupid I might have to use the OMS to avoid a collision.
Now, once I pass that 340 km altitude, I don't carry those conditions
with me what with me being reentering and all. Instead, I continue to
go down and reach the point where the lift of the capsule can be used
to adjust the impact point to precisely where I want it. THIS IS HOW
IT WORKS NOW AND THERE'S NO REASON IT WOULD CHANGE BECAUSE OF
STARLINK.

Get it now?

99.6% clear. The 400 ms at most that you can't fly through aren't
going to appreciably affect anything.

So what you are stating is that NASA is perfectly OK with de-orbiting
any any time because the odds of being at the wrong place and wrong time
during that 400ms are so low as to not even bother?


No, dear boy. I'm stating what I'm stating, not the stupid things you
try to imply. In order to avoid that satellite you MIGHT have to do
your reentry burn either 200 ms early or 200 ms late, worst case. Even
on a pure ballistic reentry, how far does that move your landing
point? It's certainly within the lift capability of the capsule to
correct.


If they do "aim" to take the threat seriously and pass between 2
satellites based on their orbital elements, is there confidence that a
de-orbit burn can not only start right on time (easy) but also
decelerate at the exact rate (consider a capsule's mass may not be fixed
depending on what cargo they are returning) such that they will cross
path with Starlink orbit at just the right time?


Yes. The capsule's mass is always 'fixed' in that it doesn't change
in flight. If you can't predict the reentry precisely then you cannot
predict the landing point precisely and you cannot do spaceflight.
Since we obviously CAN do spaceflight, your 'concern' is obviously not
a real problem.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn