[meteorite-list] Why did they not use the leftover propellanttoheighten the orbit and push the rogue satellite into space?

From: MexicoDoug <mexicodoug_at_meteoritecentral.com>
Date: Tue, 13 Sep 2011 18:35:12 -0400 (EDT)
Message-ID: <8CE407C88F976A7-4A4-48F77_at_webmail-m101.sysops.aol.com>

Thank you and succinct and very well put Rob! I'm sorry I didn't get
your post before replying to Dennis with mine and if you have any
comments on it I'd appreciate them ...

I agree there is "counter intuition" going on here.

Sometimes taking it to the extreme helps me think about these sorts of
things.

So: Let's say you put on the brakes so hard that you stopped your
satellite in in its tracks. Then what would happen to the orbit?

Well, I guess it would be just like a linear spring expanding and
contracting with the earth at the midpoint. In the real world that
would just be a free fall smash.

But if earth were a equal-sized double planet and no air resistence in
between, and the satellite were perpendicular to their plane of orbit,
you would just get it oscillating up and down between two points in the
"shared sky" through the center of mass. Those points could be as far
away as you wished. The further away they were, the slower the overall
"orbit" average orbital speed would be...The closer they were, the
faster the average orbital speed would be.

That explains intuitively why average speed is slower for higher
orbits, right or wrong, at least to me ;-)

Kindest wishes
Doug








-----Original Message-----
From: Matson, Robert D. <ROBERT.D.MATSON at saic.com>
To: Dennis Cox <dragon-hunter at live.com>; Meteorite List
<meteorite-list at meteoritecentral.com>; MexicoDoug <mexicodoug at aim.com>
Sent: Tue, Sep 13, 2011 5:13 pm
Subject: RE: [meteorite-list] Why did they not use the leftover
propellanttoheighten the orbit and push the rogue satellite into space?


Hi Dennis/Doug,

You're both right, actually. In the counter-intuitive world of orbital
mechanics, while an orbital burn in a direction opposite to the velocity
vector decreases the orbital velocity at that point in the orbit, it
actually increases the average orbital velocity over the entire orbit
since the post-burn semi-major axis will be smaller. (The lower the
semi-major axis, the faster the orbital period *and* the faster the
average orbital velocity). So putting on the brakes, so to speak,
actually speeds you up. --Rob

-----Original Message-----
From: meteorite-list-bounces at meteoritecentral.com
[mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of Dennis
Cox
Sent: Tuesday, September 13, 2011 1:56 PM
To: Meteorite List; MexicoDoug
Subject: Re: [meteorite-list] Why did they not use the leftover
propellanttoheighten the orbit and push the rogue satellite into space?

You're second guessing your self Doug.

You said:

>oops:
>
> "Slow it down 600 mph (to 16,400 mph) and burn up vs. speed it up 600
> mph (to 17,600 mph) and get to an orbit 300 miles higher in altitude "
>
> should read:
>
> "Speed it up 600 mph (to 17,600 mph) and burn up vs. slow it down 600
> mph (to 16,400 mph) and get to an orbit 300 miles higher in altitude "
>
> ****


No, you got it right the first time.

You have to Decelerate the satellite to get it to fall out of orbit and
burn
up. And accelerate it to get it to climb up into a higher orbit.


  
Received on Tue 13 Sep 2011 06:35:12 PM PDT