Re: Death Sentence for the Hubble?
From: JATO (No-Canned-Ham)
Date: 03/19/05
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Date: Sat, 19 Mar 2005 02:17:04 GMT
On Sat, 19 Mar 2005 03:46:46 GMT, simberg.interglobal@org.trash (Rand
Simberg) wrote:
>On Sat, 19 Mar 2005 00:26:26 GMT, in a place far, far away, JATO
><jato<No-Canned-Ham>@jatobservatory.org> made the phosphor on my
>monitor glow in such a way as to indicate that:
>
>
>>>> ELV are far more reliable than the shuttle.
>>>
>>>Really? Last time I checked, they weren't very far apart in terms of
>>>reliability.
>>
>>Well the insurance companies don't agree with you (and neither do I) the
>>most expense part of insuring a commercial spacecraft is the first 2
>>minutes of the flight, the lift-off, then the next 18 minutes, and then
>>payload separation and orbit injection. The insurance premium for shuttle
>>flights when they were used to launch commercial spacecraft were more
>>expense than ELV's. Why was that? Because the insurance companies realized
>>the risk of failure of a shuttle launch was higher than the risk of a
>>conventional ELV.
>
>That was almost twenty years ago. The insurance companies had very
>little data to work with at that time. It really doesn't mean much.
>
>Shuttle's empirical reliability is two losses in over a hundred
>missions, or better than 98%. The claimed reliability for the EELV,
>supposedly the state of the art for American expendables is...98%.
>
>>But the good thing about the comsats is most of
>>them are insured. In some cases the companies are even paid for the lost
>>revenue the birds would have generated. As for as the billion $ plus spy
>>birds. That's your tax dollars going in the drink. Did you know that there
>>have been government birds prohibited from flying on the shuttle because
>>the probability of loss was to deemed to be to great?
>
>No. Mostly because it's not true.
And you know this how? I have seen the contract for at least one of these
missions. It was prohibited from being launched on the shuttle. While the
reason was not printed in the contract, it was verbalized in no uncertain
terms, and this was not 20 years ago.
>
>Most government "birds" go to orbits that can't be reached by the
>Shuttle.
>
It depends on the mission, there are a lot of government missions that
could be shuttle missions. If the satellites have apogee engines to raise
it's orbit, which most do, and meet the mass requirement then they can be
shuttle launched. Just as all the geo spacecraft that have ever been launch
from the shuttle. The shuttle goes no where near 22K miles out.
>The rest go on other vehicles because they're cheaper, not because
>their reliability is better.
I agree it is cheaper. that goes without saying. But the fact is there
have been missions that where not flown on the shuttle, and not because of
cost or orbit. It was for the reason mentioned above.
>
>>>> Telemetry does a great job of telling you what is going on with the rocket
>>>> during launch. It's designed to do just that.
>>>
>>>This is true, but there are still failures of ELV's where it's hard to find
>>>an exact cause. You may know you lost pressure in the oxidizer feed line to
>>>the upper stage engine, but not know the root cause. In order to "fix" this
>>>sort of problem, you have to resort to expensive engineering analysis to
>>>determine the most likely cause of that loss of pressure. In the end,
>>>that's all you'll have the most likely cause, not *the* cause.
>>
>>Every modern day ELV failure that I know of has been pinned down to the
>>cause.
>
>After many months, and a lot of money.
>
>>>On a reusable vehicle with engine out capability, you'd finish the mission,
>>>land the vehicle, then do inspections (possibly more) to find the root
>>>cause. You're much more likely to find *the* cause of the failure with a
>>>reusable vehicle than with an ELV that's too expensive to recover (if it's
>>>possible to recover intact at all).
>>
>>Why would a commercial business that has a payload to launch want to pay
>>for all the extra weight of a launch vehicle that is going to come back to
>>earth?
>
>One doesn't pay for the weight of a launch vehicle. One pays whatever
>the launch price is.
Launching weight is not free.If doesn't matter if the weight is the launch
vehicle or the payload. The more weight then the thrust you need. The more
thrust, the more the cost. That thrust may come in the form of an SRB or
the primary rocket engine. In any case the customer pays. Which is why one
reasons why some launch cost more than others. If that where the case it
would cost no more to launch a Titan than a Delta 2.
>
>>The extra weight would add a massive amount to the launch price.
>
>There is zero data, or theory, to support this statement. Launch
>prices are much more complicated than vehicle weight. That's one of
>the least significant factors, in fact.
If you think spacecraft mass/weight is not a prime factor for launch
vehicle selection and pricing you are sadly mistaken. I see this on a
regular basis. When the weight of the spacecraft grows during the design
phase, people quickly become concerned about the cost impact of the added
weight for the selected launch vehicle. Especially if the launch vehicle is
carrying 2 (or more) spacecraft such as the Ariane launcher. This
continues right up until the spacecraft's weight and mass grows until it's
forced onto another launch vehicle.
-JATO
http://jatobservatory.org
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