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Old December 10th 05, 02:06 PM posted to sci.space.policy
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Default SpaceX Launch Update

FWIW Got this from the SpaceX email list:

Launch Date
The new launch date is approximately December 20, depending on when the
Missile Defense Agency testing is complete. As soon as we have a firm
time, it will be posted on the SpaceX website.

Liquid Oxygen
Regarding liquid oxygen (LOX) supplies, we expect to have enough on
hand this time to fill the rocket four or five times over. This should
account for almost any issue with a particular storage tank as well as
an extended hold on the pad. There is an engineering term known as a
s*load. I have asked that we have at least two s*loads on hand in case
one s*load is not enough.

We chartered a C-17 to fly two of our empty high quality LOX containers
to Hawaii, sourced another high quality LOX container on Hawaii and put
all three on the barge to Kwajalein. In addition, our LOX plant on
Kwajalein has been repaired and is producing LOX on island again.

Some might be wondering why we were so dumb as to run out of LOX on a
remote tropical island on the last launch attempt.
Believe me, we tried hard to avoid it, but several issues conspired to
create the problem:
* The additional month of Merlin testing resulted in
additional LOX boil-off on island.
Even though it is stored in vacuum jacketed containers,
LOX at -300F degrees does not like being on a tropical
island at 85F.
*The SpaceX LOX plant on island broke down a few weeks prior
to launch,
which meant we could not top up.
*We ordered replacement LOX from Hawaii, but the container
quality was poor,
so only 20% of what we ordered actually arrived.
*Ground winds were unusually high on launch day,
which amplifies the boil-off rate significantly,
since the Falcon's first stage LOX tank is uninsulated.
*All of the above would not have mattered if our final
storage tank did not have a small,
manual vent valve incorrectly in the open position.
Somewhat
agonizingly, we were only a few percent away from being
full. We just needed a little sip from the last tank.
*After a while, we were able to close the vent and fill the
vehicle's LOX tanks.
However, we use LOX to chill our onboard helium and the
absence of ground
LOX to do so resulted in the helium heating up and venting
back to storage.
In the end, we did not have enough LOX to stay filled on the
rocket and chill &
pressurize the helium.

Engine Computer
The engine computer reboot anomaly was definitively traced to a ground
power problem. Importantly, this would have had no effect on flight,
since we switch to vehicle power before the autosequence begins. The
reason it cropped up at Kwajalein was that the higher load on the
longer umbilical (three times longer than in prior tests) coupled with
high temperatures in Kwajalein resulted in increased resistance in the
ground umbilical. This was just enough to lower the voltage below
minimums and cause an engine computer reset when drawing maximum power.
The same max power test was repeated on internal vehicle batteries
with no problem at all.
This problem has been solved by slightly increasing voltage on the
ground umbilical.

--Elon--


Well we know the whole story, do we cut them some slack for this?

Just my $0.02

Space Cadet

 




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