On 1/21/2018 12:04 PM, Stephen wrote:
> I think the real problem is that orbital mechanics is not cinema 
> friendly. The public expect (from their experience on Earth) that if you 
> accelerate towards an object you get closer, quicker in a straight line. 
> Not that your orbit will get higher or lower. That is what stopped me 
> watching any of the Star Wars follow ups.
> 

Well, that's not fair, since in Star Wars the space ships have very very 
powerful engines. If you have a powerful enough engine, you can make a 
house fly in a straight line.


Mike

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On 21/01/2018 17:11, Mike Horvath wrote:
> On 1/21/2018 12:04 PM, Stephen wrote:
>> I think the real problem is that orbital mechanics is not cinema 
>> friendly. The public expect (from their experience on Earth) that if 
>> you accelerate towards an object you get closer, quicker in a straight 
>> line. Not that your orbit will get higher or lower. That is what 
>> stopped me watching any of the Star Wars follow ups.
>>
> 
> Well, that's not fair, since in Star Wars the space ships have very very 
> powerful engines. If you have a powerful enough engine, you can make a 
> house fly in a straight line.
> 
> 

Fair or not it broke my sense of disbelief. Pedantic moi?
But then I'm not a great movie fan.

-- 

Regards
     Stephen

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Le 20/01/2018 à 17:09, Kenneth a écrit :
> So it follows that the
> Space shuttle and the apple-- in the same orbit-- are going at the same speed or
> velocity. (If their speeds were different, one would head further off into
> space-- attaining a higher orbit, or maybe a more eccentric one?)

Which remind me of a curiosity: if the apple goes faster, it goes
higher... and performs then less revolutions than the station.

When you're a satellite, if you want to move ahead of another one, you
need to SLOW to be able to jump from behind to the front.

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On 26/01/2018 17:02, Le_Forgeron wrote:
> Le 20/01/2018 à 17:09, Kenneth a écrit :
>> So it follows that the
>> Space shuttle and the apple-- in the same orbit-- are going at the same speed or
>> velocity. (If their speeds were different, one would head further off into
>> space-- attaining a higher orbit, or maybe a more eccentric one?)
> 
> Which remind me of a curiosity: if the apple goes faster, it goes
> higher... and performs then less revolutions than the station.
> 
> When you're a satellite, if you want to move ahead of another one, you
> need to SLOW to be able to jump from behind to the front.
> 

I wish someone had told the Star Wars makers, that fact.

-- 

Regards
     Stephen

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Am 26.01.2018 um 18:02 schrieb Le_Forgeron:
> Le 20/01/2018 à 17:09, Kenneth a écrit :
>> So it follows that the
>> Space shuttle and the apple-- in the same orbit-- are going at the same speed or
>> velocity. (If their speeds were different, one would head further off into
>> space-- attaining a higher orbit, or maybe a more eccentric one?)
> 
> Which remind me of a curiosity: if the apple goes faster, it goes
> higher... and performs then less revolutions than the station.
> 
> When you're a satellite, if you want to move ahead of another one, you
> need to SLOW to be able to jump from behind to the front.

Actually it depends how quickly you want to achieve this maneuver. If
you're in low earth orbit, have plenty of time on your hand, and/or have
a large distance to catch up, you may indeed want to decelerate in the
current direction of travel, wait for the peculiarities of orbital
mechanics to carry you the desired distance ahead, and then re-inject
into the original orbit, as it's probably the most fuel-efficient maneuver.

However, such a maneuver requires at least one full orbital revolution
to complete. Even in low earth orbit, that's about 1.5 hours.

Also, I guess the precision for such a maneuver may be comparatively low.


If you want to achieve the maneuver faster, you need to accelerate more
downward or even forward. For instance, in the final phase of docking
two spacecraft, orbital maneuvering is actually pretty intuitive.

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