🚀 go-pugleaf

In article <C0049H.7tB@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes:
>In article <1992Dec27.163935.20473@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes:
>>It's the network reconfiguration costs that get you. When NBC had to
>>reconfigure from K2 to SBS 3 due to a control failure on K2, it cost
>>NBC $150,000 a *minute* for 4.5 hours until the major ground systems 
>>were re-aimed...   Doing it *unscheduled* because of
>>a failure of the cheapsat, can be really expensive if it only happens
>>once.
>
>Why do you assume that the redundancy will involve repointing?  If you
>*plan* for such handovers, you can put the spare satellite in the same
>orbital slot as the operational one.  (Those slots are over a thousand
>kilometers wide, there's plenty of room.)  Result, no repointing.  Only
>the control room needs to even *know* which bird is live.

Redundancy is always desirable if it's affordable, but there is a practical
difficulty with having *cold* spares in orbit. Will they work when we need
them? They have to be cold spares if they share the same orbital slot and
frequencies. That's why spare capacity is not operated cold. It's located
in another spot where it can be kept as a *hot* spare that can be tested
to assure it's in fully operational condition. With current costs, that
spare capacity is usually *rented* for ad hoc pickups so that it returns
*some* revenue while it's loitering around up there, but if comsats become
cheap enough to be left idle, they still have to pass test signals from
time to time to maintain an assurance their systems are still functional.
That means they can't be in the same slot as the system they are intended
to back up because the testing would interfere with the operations of the
main bird.

>>>>... and since for most orbits
>>>>the satellites aren't retrievable or repairable, and DC won't change
>>>>that...
>>>Again, your assumption, not a self-evident fact.  Cheap launches change
>>>almost everything, including the feasibility of retrieval and repair.
>>
>>I wasn't aware that DC was planned to have a GEO capability, or a large
>>enough cargo bay to retrieve a major comsat.
>
>Why do you assume that DC alone has to do everything?  

Oh I *don't*, I don't even assume DC will *work*. It's you folks who
keep saying: "DC is the answer. Now what was the question?"


>The big expense
>of doing most anything in space is getting into LEO; cutting that cost
>massively makes *everything* more feasible.  It becomes much more
>attractive to develop a tug capable of bringing things back down from
>GEO, or a reentry capsule capable of landing a payload too big for a
>DC cargo bay.  Neither of these devices is technologically difficult;
>they don't exist at the moment because operations costs -- mostly
>the cost of launching to LEO -- are too high.

Well if they're too big for DC, then they can't *get* into LEO in 
the first place by that "cheap" launch method. So you have development
costs *and* deployment costs to consider in addition to support costs
for your tugs and re-entry capsules. They don't look so cheap anymore.
It's not impossible to deploy mulitple special purpose vehicles in
space, of course, but cheap as an airliner ticket they ain't.

Gary

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