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Re: Imagine the first landing strip on the moon

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Am 30.07.2015 15:34, schrieb Sylvia Else:

>>>> Are you just saying that this task is not achievable without a
>>>> computer?
>>>
>>>
>>> No. It is possible without computers, but is difficult. Certainly the
>>> reverted thrust is not easy to control, since you have a set of
>>> difficult tasks:
>>>
>>> point the engine in the right direction (opposite to the flight path)
>>
>> The spaceship had to point the thrust EXACTLY into the direction, where
>> it is flying, since even a few degrees off would make the ship rotate.
>> And that would be EXTREMELY dangerous.
>
> The thrust line has to pass through the craft's centre of gravity to
> avoid making the craft rotate. The direction of motion (which is
> ill-defined anyway) has nothing to do with it.

Actually no!

There are two components: inertia and gravity.

To decelerate the craft, the thrust should point directly into the 
direction, where the ships flies. (That's what I called 'direction of 
motion'.) This is caused by inertia, what is not altered by the lower 
gravity of Moon.

To compensate acceleration caused by gravity, the engine should generate 
a force in opposite direction (up), hence the thrust should point down.

This makes two accelerations that combine to the needed thrust, (what 
the crew had to direct properly).

Any minuscule error would cause a rotation or other unwanted features of 
the flight (like hitting the ground).

TH

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Re: Imagine the first landing strip on the moon wobbly <wobbly@dont-email.me> - 2015-07-28 22:20 +0000
  Re: Imagine the first landing strip on the moon Thomas Heger <ttt_heg@web.de> - 2015-07-29 03:14 +0200
    Re: Imagine the first landing strip on the moon Thomas Heger <ttt_heg@web.de> - 2015-07-30 22:38 +0200
      Re: Imagine the first landing strip on the moon wobbly <wobbly@dont-email.me> - 2015-08-02 17:02 +0000
        Re: Imagine the first landing strip on the moon kefischer <emoneyjoe@iglou.com> - 2015-08-02 14:40 -0400
          Re: Imagine the first landing strip on the moon Thomas Heger <ttt_heg@web.de> - 2015-08-04 04:32 +0200
            Re: Imagine the first landing strip on the moon John Gogo <jfgogo22@yahoo.com> - 2015-08-03 19:56 -0700
            Re: Imagine the first landing strip on the moon John Gogo <jfgogo22@yahoo.com> - 2015-08-03 19:58 -0700
            Re: Imagine the first landing strip on the moon Bohuš Matuška <bohu@paranetnet.net> - 2015-08-04 15:14 +0000
              Re: Imagine the first landing strip on the moon Thomas Heger <ttt_heg@web.de> - 2015-08-05 06:54 +0200
                Re: Imagine the first landing strip on the moon Bohuš Matuška <bohu@paranetnet.net> - 2015-08-05 13:35 +0000
                Re: Imagine the first landing strip on the moon Thomas Heger <ttt_heg@web.de> - 2015-08-06 06:42 +0200
                Re: Imagine the first landing strip on the moon John Gogo <jfgogo22@yahoo.com> - 2015-08-05 22:24 -0700
                Re: Imagine the first landing strip on the moon Thomas Heger <ttt_heg@web.de> - 2015-08-07 08:09 +0200
                Re: Imagine the first landing strip on the moon kefischer <emoneyjoe@iglou.com> - 2015-08-07 02:41 -0400
                Re: Imagine the first landing strip on the moon Thomas Heger <ttt_heg@web.de> - 2015-08-07 10:05 +0200
                Re: Imagine the first landing strip on the moon Poutnik <Poutnik4NNTP@gmail.com> - 2015-08-07 10:29 +0200
                Re: Imagine the first landing strip on the moon kefischer <emoneyjoe@iglou.com> - 2015-08-07 06:21 -0400
                Re: Imagine the first landing strip on the moon Poutnik <Poutnik4NNTP@gmail.com> - 2015-08-07 13:42 +0200
                Re: Imagine the first landing strip on the moon Emmerich Schultheiß <emme@noemail.thx> - 2015-08-07 13:01 +0000
                Re: Imagine the first landing strip on the moon Poutnik <Poutnik4NNTP@gmail.com> - 2015-08-07 16:00 +0200
                Re: Imagine the first landing strip on the moon Emmerich Schultheiß <emme@noemail.thx> - 2015-08-07 14:11 +0000
                Re: Imagine the first landing strip on the moon Thomas Heger <ttt_heg@web.de> - 2015-08-07 18:26 +0200
                Re: Imagine the first landing strip on the moon kefischer <emoneyjoe@iglou.com> - 2015-08-07 11:20 -0400
                Re: Imagine the first landing strip on the moon Poutnik <Poutnik4NNTP@gmail.com> - 2015-08-07 18:07 +0200
                Re: Imagine the first landing strip on the moon Emmerich Schultheiß <emme@noemail.thx> - 2015-08-07 17:18 +0000
                Re: Imagine the first landing strip on the moon pnalsing@gmail.com - 2015-08-07 10:41 -0700
                Re: Imagine the first landing strip on the moon Emmerich Schultheiß <emme@noemail.thx> - 2015-08-07 17:49 +0000
                Re: Imagine the first landing strip on the moon pnalsing@gmail.com - 2015-08-07 11:15 -0700
                Re: Imagine the first landing strip on the moon Emmerich Schultheiß <emme@noemail.thx> - 2015-08-07 18:26 +0000
                Re: Imagine the first landing strip on the moon kefischer <emoneyjoe@iglou.com> - 2015-08-07 14:31 -0400
                Re: Imagine the first landing strip on the moon pnalsing@gmail.com - 2015-08-07 11:46 -0700
                Re: Imagine the first landing strip on the moon kefischer <emoneyjoe@iglou.com> - 2015-08-07 15:58 -0400
                Re: Imagine the first landing strip on the moon pnalsing@gmail.com - 2015-08-07 19:43 -0700
                Re: Imagine the first landing strip on the moon John Gogo <jfgogo22@yahoo.com> - 2015-08-07 20:47 -0700
                Re: Imagine the first landing strip on the moon John Gogo <jfgogo22@yahoo.com> - 2015-08-07 18:49 -0700

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