
SpaceX Dragon successfully docks with International Space Station - iProject
http://arstechnica.com/science/2013/03/spacex-dragon-successfully-docks-with-international-space-station/
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methodin
Is there any significance to the fact that both major launches had problems
but did not hinder a successful mission? Is that a common occurrence as far as
missions go to fail (or have failures) while still gracefully completing?

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tharax
I remember my statistics lecturer was fond of pointing out that NASA estimated
the probability of SOMETHING failing on launch was (1). That is, because of
the complexity of the project, there was always something that was missed or
broken - although it could have been as simple as a bulb that was backlighting
a switch might be blown, or a cupboard might have been restocked incorrectly,
or a calculation for external events might be slightly off.

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neurotech1
They had a shuttle mission where everything was nominal, even the toilet kept
working the whole mission.

But yeah, space flight is like that. Then again its relatively rare for a jet
fighter to consistently return Code 1, no faults. Usually its Code 2 with
minor fixes required pretty regularly. Code 3 is an abort.

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stcredzero
The human body is basically code 2 all the time. It's just that it can fix
itself, until you get code 3.

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eliben
It would be interesting to see the total cost of this mission, and compare it
to the total cost of similar NASA missions in the past.

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InclinedPlane
Cost is an unknown except to SpaceX. Price (i.e. cost to the consumer) is
easier to figure out but a little more complicated for reasons I'll explain
later.

The easiest direct comparison would be to the ESA's ATV. Each ATV launch costs
around $900 million in amortized development costs plus vehicle costs plus
launch costs. But, it delivers 6,595 kg of cargo, which puts the delivered
cost of cargo at about $132/gram.

In comparison, the Dragon is on a fixed price contract (about $133 million per
vehicle) which includes launch and operations and whatnot. This particular
Dragon is delivering 1050 kg of supplies (677 kg within the pressurized part
of the spacecraft, the rest within the unpressurized "trunk"). This comes out
to a cost to NASA of $127/gram.

Which, admittedly, is not Earth shattering. However, this flight will also be
returning 1370 kg of equipment back to Earth, including highly valuable
scientific experiments and such-like. And Dragon is currently the only vehicle
capable of doing so. On the whole this makes Dragon more than worthwhile.

However, this is still only the 2nd operational Dragon resupply mission, and
they will continue to increase the amount of cargo delivered as they become
more confident in the vehicle and especially as the Falcon 9 v1.1 becomes
operational (which will happen in the next flight) which will add about 4
tonnes of additional payload capacity. If fully utilized it could bring the
cost of cargo deliveries to ISS down to around $30-$50/g. Also, there is
definitely an element of subsidizing the development of new systems in the CRS
contract terms, though even so they're reasonably cost effective.

Edit: to compare to the Shuttle, on an MPLM mission the Shuttle could deliver
about 15 tonnes of supplies and equipment and cost around $1.5 to $2 billion
per launch (the higher figure due to the extremely low flight rate near the
end of the Shuttle program), which works out to a cargo delivery cost of
around $100/g, though the Shuttle could also return significant amounts of
cargo.

Edit2: I inadvertently omitted the cost of the MPLM modules themselves from
the calculation above, although including them would be difficult since most
of them were built by the Italian Space Agency as payment in kind for ISS
access, overall they would only affect the cost figures by less than 20%.
Also, fun fact: the MPLMs were named for famous Renaissance artists, or ninja
turtles, here's NASA's logo: [http://en.wikipedia.org/wiki/File:Multi-
Purpose_Logistics_Mo...](http://en.wikipedia.org/wiki/File:Multi-
Purpose_Logistics_Module_Logo.png)

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ramidarigaz
Wow. I had no idea the ATV was so expensive.

As a side note, your comments in space-related threads are always awesome. Do
you work in the industry?

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InclinedPlane
A lot of the cost of the ATV comes from the development cost and the low
number of missions (for clairty I've amortized that cost through the missions
planned up to 2014 in the above). Even so it costs about half a billion
dollars just to build and launch each one. To be fair, the ATV is able to
transfer propellant to the station which is something that only it and the
Progress vehicles can do.

For myself, I'm merely an enthusiastic amateur, I've been studying spaceflight
closely since I was a child and I've come to pick up a few tidbits of trivia
along the way.

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ameister14
I think a big congratulations is due for SpaceX; one is an aberration, two is
on it's way to being normal. So congrats to them for moving towards a
normalization of privatized space operations.

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DeepDuh
I didn't follow everything in detail this time. What was with that problem
they were talking about?

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ramidarigaz
The capsule's thrusters had a blockage which prevented them from maneuvering
and deploying the solar panels. They managed to clear the blockage just fine.

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DeepDuh
Interesting. Did they release informations on how they solved that? Also,
don't they have some built in redundancy for the thrusters?

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jlgreco
3 of 4 thruster packs experienced the issue; they need 2 of 4 to open the
solar panels and 3 of 4 to dock with the ISS. From what I understand they got
all 4 working again using the "water hammer" effect to clear the blockage, but
I'm not sure how accurate that is.

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DeepDuh
Imagine it's your job to fiddle around remotely with fuel pump electronics (or
whatever may create that water hammer) within a time window of maybe 20
minutes or else you've just sunk a 100M investment somewhere in the ocean.
Must be lots of fun o.O

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pestaa
There's plenty of excitement for me just tweaking a live production server,
not sure my heart could cope with what you just described.

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rockyroadster
I wonder what biological samples taken from the crew means.

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jdavis703
It probably means what you think: urine, blood, saliva, fecal matter...
Whatever a scientist or doctor on the ground might need to analyze.

