Re: harddisk in space

From: The Ghost In The Machine (ewill_at_sirius.athghost7038suus.net)
Date: 02/03/04 

Date: Tue, 03 Feb 2004 05:00:11 GMT

In sci.physics, Papadopoulos Giannis
<ipapadop@inf.uth.gr>
 wrote
on Tue, 03 Feb 2004 02:41:42 +0200
<bvmqo5$23lo$1@ulysses.noc.ntua.gr>:
> Florian-Wolfgang Stock wrote:
>> Jan Panteltje <pNaonStpealmtje@yahoo.com> writes:
>>
>>
>>>The other issue that occured to me is that if you spin up
>>>a harddisk in space, the spacecraft will change attitude
>>>(it would work like a reaction wheel).
>>>I am not sure if the gyroscopic effect of a spinning harddisk
>>>would screw up attitude control algos......
>>
>>
>> As you mentioned it, it comes to my mind ... you are right that every
>> acceleration of the disk results also in reverse acceleration of the
>> Shuttle. But if I now think of it you can easily avoid it. I guess
>> beacuse of redundance (think of raid or similiar) you can assume the
>> number of HDD (if they really use the old fashioned HDD) is multiple
>> of two. Now you just assemble them that you attach to a hard disk
>> another one top to top (or bottom to bottom), so that the spinning
>> axes are the same, but through opposite spinning direction the forces
>> are negated.
>>
>> Florian
>>
>> PS: I guess the inertia from the disks is really low (I dont have time
>> and interest to calc it now), so I dont know if its important. OTOH I
>> think they need to adjust everytime their direction and course due to
>> uncalcable events (like sun winds, magnetic field of the earth and
>> many other I cant even think of) - so they maybe dont care.
>>
> hdds should never be placed upside-down... they are designed to have the
> circuit on the bottom side...

Define "upside down" in deep space. :-)

>
> PS. nice signature ;)
> 

-- 
#191, ewill3@earthlink.net
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