Why does SpaceX load the LOX first?

http://www.spacex.com/Maiden_Flight_Overview.pdf

They must have some good reason that makes it worthwhile to boil off as
much LOX as they can before launch, right? Does anyone know what it is?

richard schumacher wrote:
http://www.spacex.com/Maiden_Flight_Overview.pdf

They must have some good reason that makes it worthwhile to boil off as
much LOX as they can before launch, right? Does anyone know what it is?

I don't know so i guess, chill structures to prevent thermal stresses?
And rp-1 can't be pumped in because of the common bulkhead thing until
just before launch (it'd warm up the lox). And you can't do the opposite
because of some thermal stress issues?
It's also noticeable that the second stage filling takes
longer and is started earlier, both for lox and rp-1.

Page 12 has a hilarious picture of the satellite in the shroud.
The fairing isn't big, but that payload is such a tiny tiny cube,
30 cm a side, that it feels the rocket is launched empty...
Of course, with their "cheap" price, it makes sense, but it's
also a dod sponsored test launch the way it is (someone
can argue against this).

"meiza" wrote in message ...
richard schumacher wrote:
http://www.spacex.com/Maiden_Flight_Overview.pdf

They must have some good reason that makes it worthwhile to boil off as
much LOX as they can before launch, right? Does anyone know what it is?

I don't know so i guess, chill structures to prevent thermal stresses?
And rp-1 can't be pumped in because of the common bulkhead thing until
just before launch (it'd warm up the lox). And you can't do the opposite
because of some thermal stress issues?
It's also noticeable that the second stage filling takes
longer and is started earlier, both for lox and rp-1.

I spoke to our SpaceX "expert" at work (he's responsible for tracking their
activities) and he tells me it's so they can finish propellant loading
almost simultaneously late in the count. It takes longer to load the LOx, so
they start with it, then begin RP-1 load. When both systems are loaded, the
count is generally down around T-25m or so.

Sorry for the late answer.

In article ,
"Kim Keller" wrote:

"meiza" wrote in message ...
richard schumacher wrote:
http://www.spacex.com/Maiden_Flight_Overview.pdf

They must have some good reason that makes it worthwhile to boil off as
much LOX as they can before launch, right? Does anyone know what it is?

I don't know so i guess, chill structures to prevent thermal stresses?
And rp-1 can't be pumped in because of the common bulkhead thing until
just before launch (it'd warm up the lox). And you can't do the opposite
because of some thermal stress issues?
It's also noticeable that the second stage filling takes
longer and is started earlier, both for lox and rp-1.

I spoke to our SpaceX "expert" at work (he's responsible for tracking their
activities) and he tells me it's so they can finish propellant loading
almost simultaneously late in the count. It takes longer to load the LOx, so
they start with it, then begin RP-1 load. When both systems are loaded, the
count is generally down around T-25m or so.

Sorry for the late answer.

No indeed, thanks! So in fact they're not boiling off more than
necessary. I had assumed that they would load the propellants
sequentially, for simplicity or safety.